To evaluate the regularity of resilient modulus for hot-mix asphalt(HMA) under large temperature fluctuations,back propagation(BP) neural network technology was used to analyze the continuous change of HMA resilient m...To evaluate the regularity of resilient modulus for hot-mix asphalt(HMA) under large temperature fluctuations,back propagation(BP) neural network technology was used to analyze the continuous change of HMA resilient modulus.Firstly,based on the abundant data,the training model of HMA resilient modulus was established by using BP neural network technology.Subsequently,BP neural network prediction and regression analysis were performed,and the prediction model of HMA resilient modulus at different temperatures(-50℃ to 60℃) was obtained,which fully considered multi-factor and nonlinearity.Finally,the fitted theoretical model can be used to evaluate the HMA performance under the condition of large temperature fluctuations,and the rationality of theoretical model was verified by taking Harbin region as an example.It was found that the relationship between HMA resilient modulus and temperatures can be described by inverse tangent function.And the key parameters of theoretical model can be used to evaluate the continuous change characteristics of HMA resilient modulus with large temperature fluctuations.The results can further improve the HMA performance evaluation system and have certain theoretical value.展开更多
This study aims to quantify the susceptibility of granular materials used in pavements to changes in moisture content and propose a correlation model to incorporate this susceptibility into seasonal analyses.The fines...This study aims to quantify the susceptibility of granular materials used in pavements to changes in moisture content and propose a correlation model to incorporate this susceptibility into seasonal analyses.The fines content and the percentage of fractured coarse aggregates were identified as direct indicators of the resilient modulus susceptibility to changes in water content.The results showed that the percentage of fractured coarse aggregates particles(FR)has a more significant impact on the resilient modulus(Er)of crushed granular materials used in pavement construction than the combined indicator of the fines content and sample volumetrics(nf).Crushed granular materials with a higher percentage of fractured coarse aggregates are relatively insensitive to changes in the degree of saturation,but become more sensitive as the fine fraction porosity decreases.An adjusted model was proposed based on the existing formulation,but considers a complex parameter to describe and adjust the sensitivity of base granular materials to variations in moisture content with respect to fabrication charac-teristics,fines content and volumetric properties.The model shows that the variation of Er values is below10%for fully crushed granular materials.However,it reaches approximately±12%for materials with 75%of crushed coarse aggregates andþ40%and-25%for materials with FR=50%.This model could help select good ag-gregates characteristics and adjust grain-size distribution for environments where significant moisture content variations can occur in the pavement system,such as in the Province of Quebec(Canada).As it is based on pa-rameters that can be easily determined or estimated,it also represents a valuable tool for detailed design and analysis that can consider material characteristics.展开更多
Although the dynamic properties of subgrade soils in seasonally frozen areas have already been studied, few researchers have considered the influence of shallow groundwater during the freeze–thaw(F–T) cycles. So a m...Although the dynamic properties of subgrade soils in seasonally frozen areas have already been studied, few researchers have considered the influence of shallow groundwater during the freeze–thaw(F–T) cycles. So a multifunctional F–T cycle system was developed to imitate the groundwater recharge in the subgrade during the freezing process and a large number of dynamic triaxial experiments were conducted after the F–T cycles. Some significant factors including the F–T cycle number, compaction degree, confining pressure, cyclic deviator stress, loading frequency, and water content were investigated for the resilient modulus of soils. The experimental results indicated that the dynamic resilient modulus of the subgrade was negatively correlated with the cyclic deviator stress, F–T cycle number, and initial water content, whereas the degree of compaction, confining pressure, and loading frequency could enhance the resilient modulus. Furthermore, a modified model considering the F–T cycle number and stress state was established to predict the dynamic resilient modulus. The calculated results of this modified model were very close to the experimental results. Consequently, calculation of the resilient modulus for F–T cycles considering the dynamic load was appropriate. This study provides reference for research focusing on F–T cycles with groundwater supply and the dynamic resilient moduli of subgrade soils in seasonally frozen areas.展开更多
The resilient modulus(MR)of subgrade soils is usually used to characterize the stiffness of subgrade and is a crucial parameter in pavement design.In order to determine the resilient modulus of compacted subgrade soil...The resilient modulus(MR)of subgrade soils is usually used to characterize the stiffness of subgrade and is a crucial parameter in pavement design.In order to determine the resilient modulus of compacted subgrade soils quickly and accurately,an optimized artificial neural network(ANN)approach based on the multi-population genetic algorithm(MPGA)was proposed in this study.The MPGA overcomes the problems of the traditional ANN such as low efficiency,local optimum and over-fitting.The developed optimized ANN method consists of ten input variables,twenty-one hidden neurons,and one output variable.The physical properties(liquid limit,plastic limit,plasticity index,0.075 mm passing percentage,maximum dry density,optimum moisture content),state variables(degree of compaction,moisture content)and stress variables(confining pressure,deviatoric stress)of subgrade soils were selected as input variables.The MR was directly used as the output variable.Then,adopting a large amount of experimental data from existing literature,the developed optimized ANN method was compared with the existing representative estimation methods.The results show that the developed optimized ANN method has the advantages of fast speed,strong generalization ability and good accuracy in MR estimation.展开更多
The current study aims to evaluate the dynamic response of stabilized cohesive soil using an enzymatic preparation in terms of resilient modulus.We ran a series of resilient modulus testing according to AASHTO T307 on...The current study aims to evaluate the dynamic response of stabilized cohesive soil using an enzymatic preparation in terms of resilient modulus.We ran a series of resilient modulus testing according to AASHTO T307 on three types of cohesive soil treated with an enzymatic preparation to investigate its potential on roads construction.The results show significant improvement in the resilient modulus values,estimated at 1.4 to 4.4 times that observed for the untreated soil.Because of the complexity in conducting the resilient modulus measurement,we did a regression analysis to produce reliable correlation formula to predict the resilient modulus for untreated and stabilised soil samples involving stress state.The resilient modulus values for the subgrade materials at the anticipated field stresses were determined using a universal model.The enzymatic preparation was applied in pavement of a sample road and evaluated using the plate load test.SEM analysis for soil samples shows improvement in the soil compaction via reduction of voids between soil particles.XRD analysis shows no major structural changes in the treated soils.The enzymatic preparation contains 43 mg/mL of proteins.We used the SDS-PAGE(sodium dodecyl sulphate polyacrylamide gel electrophoresis)technique to identify the main protein components;however,the presence of interfering materials(surfactants)hinders the separation.展开更多
Dynamic cone penetrometer（DCP） has been used for decades to estimate the shear strength and stiffness properties of the subgrade soils. There are several empirical correlations in the literature to predict the resil...Dynamic cone penetrometer（DCP） has been used for decades to estimate the shear strength and stiffness properties of the subgrade soils. There are several empirical correlations in the literature to predict the resilient modulus values at only a specific stress state from DCP data, corresponding to the predefined thicknesses of pavement layers（a 50 mm asphalt wearing course, a 100 mm asphalt binder course and a200 mm aggregate base course）. In this study, field-measured DCP data were utilized to estimate the resilient modulus of low-plasticity subgrade Piedmont residual soil. Piedmont residual soils are in-place weathered soils from igneous and metamorphic rocks, as opposed to transported or compacted soils.Hence the existing empirical correlations might not be applicable for these soils. An experimental program was conducted incorporating field DCP and laboratory resilient modulus tests on "undisturbed" soil specimens. The DCP tests were carried out at various locations in four test sections to evaluate subgrade stiffness variation laterally and with depth. Laboratory resilient modulus test results were analyzed in the context of the mechanistic-empirical pavement design guide（MEPDG） recommended universal constitutive model. A new approach for predicting the resilient modulus from DCP by estimating MEPDG constitutive model coefficients（k;,k;and k;） was developed through statistical analyses. The new model is capable of not only taking into account the in situ soil condition on the basis of field measurements,but also representing the resilient modulus at any stress state which addresses a limitation with existing empirical DCP models and its applicability for a specific case. Validation of the model is demonstrated by using data that were not used for model development, as well as data reported in the literature.展开更多
In order to investigate the suction-dependent properties of subgrade granular material and its effect on pavement responses,coupled hydro-mechanical simulations were conducted in Abaqus.A suction-dependent resilient m...In order to investigate the suction-dependent properties of subgrade granular material and its effect on pavement responses,coupled hydro-mechanical simulations were conducted in Abaqus.A suction-dependent resilient modulus model was integrated into the commercial finite element(FE)code Abaqus by developing a user-defined material(UMAT)subroutine.The developed model was validated by triaxial test results under different suction conditions and good agreement was achieved.A three-dimensional(3D)FE pavement model was established and the suction-dependent properties of subgrade granular material was characterized by the developed constitutive model.Hydro-mechanical pavement responses subjected to three moisture states and the falling weight deflectometer(FWD)load were calculated.Simulation results reveal that the resilient modulus of subgrade granular material is sensitive to suction and stress states;high groundwater table decreases the overall resilient moduli of subgrade structure due to suction reduction,leading to the increase of the maximum surface deflection,the tensile strain at bottom of the surface layer,compressive strain on top of subgrade,and consequently,deterioration in pavement performance.展开更多
The performance evaluation of existing flexible pavements has become a priority issue for many highway maintenances engineers.To make appropriate rehabilitation and management decisions,the engineers most often rely o...The performance evaluation of existing flexible pavements has become a priority issue for many highway maintenances engineers.To make appropriate rehabilitation and management decisions,the engineers most often rely on efficient methods for the determination of the strength of pavement layers.Resilient modulus is a very important parameter to be identified and used in pavement design.The resilient moduli of asphalt mixtures are typically measured using the indirect tension test procedure in compliance with the ASTM D4123 standard that is superseded by ASTM D7369.The standard requirement is that the prepared specimens for the tests should have a minimum height of the sample over its diameter ratio of 0.4.Generally,specimens used in the tests are either a nominal 100 mm or 150 mm in diameter with a minimum thickness over diameter ratio of 0.4.However,100 mm diameter core specimens taken from site wearing courses with thicknesses ranging from 40 mm to 50 mm most often do not fulfil the minimum ratio of 0.4 after they are trimmed for testing.Since there was no any option,part of the binder courses had to be trimmed to make up for the minimum ratio requirement.This tends to result in inaccurate assessment of the resilient modulus values of the samples.As such,a new procedure was explored to test specimens smaller than 100 mm in diameter.This may minimize the material volume requirement from the field and also for the fabrication of smaller samples in the laboratory.Based on the available thickness of wearing course or overlay,the appropriate sizes were determined.For a two-layer system a 56.3 mm diameter was deemed necessary while a 37.5 mm diameter was observed to be appropriate for a three-layer system.Such an approach for resilient modulus test using miniature specimens of 56.3 mm and 37.5 mm in diameter has a great potential for practical relevance for the industry.展开更多
Interlayer soil in railway substructures is characterized by a fine/coarse soil mixture.Considering that the resilient modulus M_(r) of the mixture is influenced by the microstructure of fine soil,it is worthwhile to ...Interlayer soil in railway substructures is characterized by a fine/coarse soil mixture.Considering that the resilient modulus M_(r) of the mixture is influenced by the microstructure of fine soil,it is worthwhile to investigate this aspect further.In this study,the microstructure of fines was explored by mercury intrusion porosimetry(MIP),and its influence on the M_(r) of the mixture was studied by multi-stage dynamic triaxial tests with varying deviator stress amplitudesσ_(d).The results showed a fine matrix fabric obtained at water contents of fine soil w_(f)=17.6%and 13.7%(>the plastic limit of fine soil w_(p)=12%),and a fine aggregate fabric identified at w_(f)=10.6%(<w_(p)=12%).Interestingly,the influences of w_(f) andσ_(d) on the M_(r) of the mixture were observed:the rise inσ_(d) contributed to a decline in M_(r) when w_(f)>w_(p) but to an increase in M_(r) when w_(f)<w_(p).It was concluded that,for the fine matrix fabric(w_(f)>w_(p)),increasingσ_(d) induced a reduction in M_(r),while for the fine aggregate fabric(w_(f)<w_(p)),increasingσ_(d) gave rise to the growth of M_(r).The distinct M_(r)-σ_(d) behaviors for these two fabrics were explained by the competing influences between soil hardening upon loading and soil rebounding upon unloading.For the fine matrix fabric(w_(f)>w_(p)),considering its high deformability,the rebounding effect on M_(r) outweighed the hardening effect,and thus a decline in M_(r) occurred with the growth ofσ_(d).Conversely,for the fine aggregate fabric(w_(f)<w_(p)),the rebounding effect on M_(r) was secondary compared with the hardening effect based on the consideration of its low deformability,and thus an increase in M_(r) was observed with risingσ_(d).展开更多
The fatigue behavior, indirect tensile strength （ITS） and resilient modulus test results for warm mix asphalt （WMA） as well as hot mix asphalt （HMA） at different ageing levels were evaluated. Laboratory-prepared...The fatigue behavior, indirect tensile strength （ITS） and resilient modulus test results for warm mix asphalt （WMA） as well as hot mix asphalt （HMA） at different ageing levels were evaluated. Laboratory-prepared samples were aged artificially in the oven to simulate short-term and long term ageing in accordance with AASHTO R30 and then compared with unaged specimens. Beam fatigue testing was performed using beam specimens at 25 ℃ based on AASHTO T321 standard. Fatigue life, bending stiffness and dissipated energy for both unaged and aged mixtures were calculated using four-point beam fatigue test results. Three-point bending tests were performed using semi-circular bend （SCB） specimens at -10 ℃ and the critical mode I stress intensity factor K1 was then calculated using the peak load obtained from the load-displacement curve. It is observed that Sasobit and Rheofalt warm mix asphalt additives have a significant effect on indirect tensile strength, resilient modulus, fatigue behavior and stress intensity factor of aged and unaged mixtures.展开更多
Low average temperature, large temperature difference and continual freeze-thaw （F-T） cycles have significant impacts on mechanical property of asphalt pavement. F-T cycles test was applied to illustrate the mixture...Low average temperature, large temperature difference and continual freeze-thaw （F-T） cycles have significant impacts on mechanical property of asphalt pavement. F-T cycles test was applied to illustrate the mixtures＇ compressive characteristics. Exponential model was applied to analyze the variation of compressive characteristics with F-T cycles; Loss ratio model and Logistic model were used to present the deterioration trend with the increase of F-T cycles. ANOVA was applied to show the significant impact of F-T cycles and asphalt- aggregate ratio. The experiment results show that the compressive strength and resilient modulus decline with increasing F-T cycles; the degradation is sharp during the initial F-T cycles, after 8 F-T cycles it turns to gentle. ANOVA results show that F-T cycles, and asphalt-aggregate ratio have significant influence on the compressive characteristics. Exponential model, Loss ratio model and Logistic model are significantly fitting the test data from statistics view. These models well reflect the compressive characteristics of asphalt mixture degradation trend with increasing F-T cycles.展开更多
This article explains the results of a study conducted on the characterizations of subgrade soils in the region of Thies. The road platforms are mainly composed of a background soil, which is generally overlapped by a...This article explains the results of a study conducted on the characterizations of subgrade soils in the region of Thies. The road platforms are mainly composed of a background soil, which is generally overlapped by a surface layer that plays two roles. Firstly, it protects the soil structure, ensures the leveling, and facilitates the movement of vehicles. Secondly, it brings harmony in the mechanistic characteristics of the materials that compose the soil while improving the long-term life force. The methodology consisted in taking samples of subgrade soil along the roads all over the region of Thies in a 5 km diameter span. The identification tests allowed the Thies-Tivaoune, Thies-Khombole and Thies-Noto axes are characterized by tight sands, poorly graded size. While Thies Pout-axis is characteristic of severe solid particle size and spread well graded and serious to spread and well graded particle size. Finally the Thies-Montrolland axis is characterized by severe to very tight particle size and graduated to spread and serious and well graded particle size. The specific gravity values found Proctor test shows the presence of sand, sandy laterite and laterite. In the target area, polished soils of the A-3 type according to the AASHTO classification system are the most represented with 60%, followed by the A-2-6 type 25%, and the A-2-4 type with 9%, which are typical of gravel, clay, and silty sands. Soils of the A-1-b type (2%) typical of roc fragments, sands and clay are also represented. Polished sands of the A-3 type have a better efficiency on road infrastructures than other types of soil listed above. Finally, we’ve also noted the presence of soils of the A-2-7 and A-4 types with the low percentage of 2%. Subgrade soils of class S4 are the most represented with 58%, followed by those of class S5 with 42%. Samples of the Thies-Montrolland road have a claylike plasticity (CL or CH group), while those of the Thies-Pout road belong to the ML or OL and CL or OL groups with a tendency mostly directed to the CL or OL group. All these results confirm the very nature of soils on the two roads and put the light on the presence of lateritic materials with certain plasticity.展开更多
This paper will visually and experimentally assess the level of deterioration of one of the new constructed ring road pavements in Khartoum State as well as to examine and identify the causes of the failed pavement. A...This paper will visually and experimentally assess the level of deterioration of one of the new constructed ring road pavements in Khartoum State as well as to examine and identify the causes of the failed pavement. A series of field and laboratory exercises were carried out on the materials that were used in the construction of the designated pavement. Huttab, a natural gravelly material, was used in both subbase and base blend of this deteriorated pavement. The experimental tests consisted of two tasks： the first covered the study of the actual causes of pavement distress, whereas the second explored typical base material alternatives that satisfy base course needs. The tests involved basic tests and dynamic tests such as sieve, Atterberg limits, linear shrinkage, compaction, CBR （Calitbrnia bearing capacity）, abrasion whereas the dynamic tests included MR （resilient modulus）, and PD （permanent deformation）. The routine tests showed that an improper base blend was used in the failed road that resulted in excessive rutting whereas in the second tests scenario the results showed that the proper base blend from the named materials gave high strength and stiffness values and low PD compared to the natural one. On the other hand, the pure crushed sample reported high MR values and the lowest PD compared to the base blend alternative.展开更多
Ceramic waste materials are abundantly available in Malaysia from the production of ceramic tiles.In general,ceramic materials seem to possess low thermal conductivity characteristics that could reduce pavement temper...Ceramic waste materials are abundantly available in Malaysia from the production of ceramic tiles.In general,ceramic materials seem to possess low thermal conductivity characteristics that could reduce pavement temperatures when used as aggregates in asphalt mixtures.A study was undertaken to look into the performance of crushed ceramics incorporated in asphalt mixtures to replace the conventional granite aggregates from sizes 5.0 mm down including the 75 micron filler.The replacement was done proportionally with 0%,20%,40%,60%,80%and 100%ceramic aggregates by weight of granite.Several mix designs with various percentages of ceramic aggregates were formulated to determine the marshal properties such as stability,flow,and resilient modulus.In addition,the potential of ceramic aggregates in reducing the asphalt pavement temperatures was also studied.The outcome of the study showed that the ceramic aggregates in the asphalt mixtures were able to improve the performance of the mixture up to 20%which means there is a great potential for the use of it in road construction.Besides that,the rate of heating(RoH)compacted samples subjected to various temperatures dropped significantly as compared with the control granite specimens.The fatigue performance of the compacted and temperature conditioned ceramic asphalt mixtures displayed an interesting trend in terms of strain resistance at elevated temperatures.展开更多
The mechanical characteristics of road pavement layers are influenced by moisture conditions. Drying and wetting change the moisture content of the materials used in pavement structures, consequently affecting the mec...The mechanical characteristics of road pavement layers are influenced by moisture conditions. Drying and wetting change the moisture content of the materials used in pavement structures, consequently affecting the mechanical response. An experimental program was conducted to evaluate elastic deformations of a road pavement structure utilizing repetitive rigid plate load tests in a model test-pit facility. A typical Brazilian pavement （a multilayer system composed of a concrete asphalt and coarse base, and subbase） was simulated in this test-pit with devices for measuring humidity （TDR （time domain reflectometry）） and suction （tensiometers） installed every 20.0 cm along the profile. A pair of displacement transducers was attached on the surface of the pavement structure to record deformations due to dynamic loads. Two levels of groundwater table were analyzed, verifying that the pavement structure displacement increases with groundwater table growth. The structural response was evaluated and compared in physical and numerical models, and the results confirmed that the higher groundwater levels caused the greatest pavement displacements.展开更多
Stone Matrix Asphalt(SMA)is a gap graded mix;characterized by higher proportion of coarse aggregate,lower proportion of middle size aggregate and higher proportion of mineral filler.In the present laboratory study,com...Stone Matrix Asphalt(SMA)is a gap graded mix;characterized by higher proportion of coarse aggregate,lower proportion of middle size aggregate and higher proportion of mineral filler.In the present laboratory study,commonly available one conventional VG 30 bitumen and another modified binder,namely CRMB 60 have been used along with a non-conventional natural fiber,namely coconut fiber which is abundantly available in India to provide improved engineering properties and at the same time preventing the usual draining of binder in SMA.The role of a particular binder and fiber with respect to their concentrations in the mix is studied for various engineering properties.Marshall procedure has been followed to determine the optimum binder and optimum fiber contents and also to study the relative advantages of fiber addition in the SMA mixtures.Thereafter,the engineering properties under both static as well as repeated load conditions and moisture susceptibility characteristics have been studied.It is observed that only a marginal 0.3%coconut fiber addition brings significant improvement in the engineering properties of SMA mixes.展开更多
T<span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">his research was carried out to determine the rheological parameters of later...T<span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">his research was carried out to determine the rheological parameters of lateritic soils in order to contribute to the improvement of the technical documents used for pavement design in tropical Africa. The study is based on the loading repeated of cyclic triaxial tests (LRT) performed at </span><span style="font-family:Verdana;">University Gustave Eiffel (formerly Institut Fran<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">ç</span>ais des Sciences et Technologies des Transports de l’Aménagement et des Réseaux (IFSTTAR))</span></span></span></span><span><span><span><span style="font-family:;" "=""> </span></span></span></span><span></span><span><span><span style="font-family:Verdana;">in Nantes with the application of the European standard EN 13286-7: 2004</span><span style="font-family:Verdana;"> [<a href="#ref1">1</a>]</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">. The tests were performed at constant confinement stress and using the stepwise method to determine the resilient axial (<img src="Edit_9d1c29ae-1a5f-434a-9fe3-00ef5aeb5d24.png" alt="" /></span></span></span><span><span><span style="font-family:;" "=""><span><span style="font-family:Verdana;">) and radial (<img src="Edit_42548459-8f50-4ea1-832d-25e9cfdad034.png" alt="" /></span><span style="font-family:Verdana;">) deformation as a function of the axial and radial stresses. Four gravel lateritic soil</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">s</span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"> from different sites selected in Burkina Faso and Senegal were the subject of this research for the triaxial tests. These materials have a maximum diameter of 20 mm and a percentage of fines less than 20%. The LRT tests were carried out on samples compacted at three moisture contents (</span><i><span style="font-family:Verdana;">w</span><sub><span style="font-family:Verdana;">opm</span></sub></i> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">-</span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"> 2%, </span><i><span style="font-family:Verdana;">w</span><sub><span style="font-family:Verdana;">opm</span></sub></i><span style="font-family:Verdana;"> and </span><i><span style="font-family:Verdana;">w</span><sub><span style="font-family:Verdana;">opm</span></sub> </i><span style="font-family:Verdana;">+ 2%) and at 95% and 100% of optimal dry density (</span></span></span></span><span><span><i><span style="font-family:;" "=""><span style="font-family:Verdana;">γ</span><sub><span style="font-family:Verdana;">dopm</span></sub></span></i></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">). Test results showed that the characteristic resilient Young’s modulus (</span><i><span style="font-family:Verdana;">E</span><sub><span style="font-family:Verdana;">c</span></sub></i><span style="font-family:Verdana;">) of gravelly laterites soils depends on the compacted water content and the variation of the grains size distribution (sand (</span><i><span style="font-family:Verdana;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">ø</span></span></i><span style="font-family:Verdana;"> < 2 mm), motor (</span><i><span style="font-family:Verdana;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">ø</span></span></i><span style="font-family:Verdana;"> < 0.5 mm) and fines content (</span><i><span style="font-family:Verdana;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">ø</span></span></i><span style="font-family:Verdana;"> < 0.063 mm) obtained after (LRT). Materials with a high percent of fines (>20%), mortar and sand (Sindia and Lam-Lam) are more sensitive to variations in water content. The presence of water combined with the excess of fines leads to a decrease in modulus around 25% for Lam-Lam and 20.2% for Sindia. Materials containing a low percent of fines, mortar and sand (Badnogo and Dedougou) behave differently. </span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">And </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">the resilient modulus increases about 225</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">.</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">67% for Badnogo and 312.24% for Dedougou with the rise of the water content for approximately unchanged the percentage of fines, mortar and sand. Granularity therefore has an indirect influence on the resilient modulus of the lateritic soils by controlling the effects of water on the entire system. </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">Results of statistical analysis and coefficients of correlation (0.659 to 0.865) showed that the anisotropic Boyce’s model </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">is suitable to predict</span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"> the volumetric </span><span style="font-family:Verdana;">(<img src="Edit_1a36888c-cad0-4f1c-9c68-b5da0ddc323f.png" alt="" /></span><span style="font-family:Verdana;">)</span><span style="font-family:Verdana;"> and deviatoric strain (<img src="Edit_993added-0ec4-49db-ae12-3e540fa49f9c.png" alt="" /></span><span style="font-family:Verdana;">)</span><span style="font-family:Verdana;"> with stress path (Δ</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><i><span style="font-family:Verdana;">q</span></i></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">/Δ</span><i><span style="font-family:Verdana;">p</span></i><span style="font-family:Verdana;">) of the lateritic soils. </span><span><span style="font-family:Verdana;">The predicted </span><i><span style="font-family:Verdana;">E</span><sub><span style="font-family:Verdana;">r</span></sub></i><span style="font-family:Verdana;"> resilient Young’s modulus from anisotropic Boyce’s model varies according to the evolution of </span></span><span style="font-family:Verdana;">the bulk stress (<img src="Edit_ab550c56-8bab-4806-9ec7-fab794d785eb.png" alt="" /></span><span style="font-family:Verdana;">). A correlation around 0.9 is obtained from the power law model.</span></span></span></span></span>展开更多
Vigorous and continued efforts by researchers and engineers have contributed towards maintaining environmental sustainability through the utilization of waste materials in civil engineering applications as an alternat...Vigorous and continued efforts by researchers and engineers have contributed towards maintaining environmental sustainability through the utilization of waste materials in civil engineering applications as an alternative to natural sources.In this study,granite aggregates in asphaltic mixes were replaced by electric arc furnace(EAF)steel slag aggregates with different proportions to identify the best combination in terms of superior performance.Asphalt mixtures showing the best performance were further reinforced with polyvinyl alcohol(PVA),acrylic,and polyester fibers at the dosages of 0.05%,0.15%,and 0.3%by weight of the aggregates.The performance tests of this study were resilient modulus,moisture susceptibility,and indirect tensile fatigue cracking test.The findings of this study revealed that the asphalt mixtures containing coarse steel slag aggregate exhibited the best performance in comparison with the other substitutions.Moreover,the reinforced asphalt mixtures with synthetic fibers at the content of 0.05%exhibited an almost comparable performance to the unreinforced asphalt mixtures.Modifying the asphalt mixtures with PVA,acrylic,and polyester fibers at the proportion of 0.15%have improved the fatigue cracking resistance by 41.13%,29.87%,and 18.97%,respectively.Also,the fiber-modified asphalt mixtures with PVA,acrylic,and polyester have enhanced the fatigue cracking resistance by about 57%,44%,and 39%,respectively.The results of the resilient modulus demonstrated that as the fiber content increase,the resilient modulus of the reinforced asphalt mixtures decreases.Therefore,introducing synthetic fibers at the content of 0.3%has slightly decreased the resilient modulus in comparison with unreinforced mixtures.On the other hand,the results of the mechanisticempirical pavement design showed that the reinforced asphalt mixes with a high content of synthetic fibers have shown lower service life than the control mixes due to the low resilient modulus.On the contrary,based on the laboratory results,the asphalt mixes incorporating PVA,acrylic,and polyester fibers at the proportion of 0.15%have shown the potential to reduce the thickness of the asphalt layer by about 14.9%,11.80%,and 8.70%,respectively.展开更多
The type of subgrade of a railroad foundation is vital to the overall performance of the track structure.With the train speed and tonnage increase,as well as environmental changes,the evaluation and influence of subgr...The type of subgrade of a railroad foundation is vital to the overall performance of the track structure.With the train speed and tonnage increase,as well as environmental changes,the evaluation and influence of subgrade are even more paramount in the railroad track structure performance.A geomechanics classification for subgrade is proposed coupling the stiffness(resilient modulus)and permanent deformation behaviour evaluated by means of repeated triaxial loading tests.This classification covers from fine-to coarse-grained soils,grouped by UIC and ASTM.For this achievement,we first summarize the main models for estimating resilient modulus and permanent deformation,including the evaluation of their robustness and their sensitivity to mechanical and environmental parameters.This is followed by the procedure required to arrive at the geomechanical classification and rating,as well as a discussion of the influence of environmental factors.This work is the first attempt to obtain a new geomechanical classification that can be a useful tool in the evaluation and modelling of the foundation of railway structures.展开更多
A new characterization technique,a repeated load CBR test,was used to evaluate the resilient properties recycled mix-granulate unbound base material. This is a mixture of crushed concrete and crushed masonry,so recycl...A new characterization technique,a repeated load CBR test,was used to evaluate the resilient properties recycled mix-granulate unbound base material. This is a mixture of crushed concrete and crushed masonry,so recycled demolition waste,this is used on a wide scale in the Netherlands as road base material. The repeated load CBR test,done with standard CBR testing facility,was conducted to estimate the resilient modulus. For comparison and assessment purposes the tests were carried out with the same material conditions (composition,grading,moisture and compaction degree) as have been applied in earlier triaxial testing in the Road and Railway Engineering Laboratory,Delft University of Technology. The results indicate that the repeated load CBR test yields a good estimate of the stress dependent equivalent modulus for the sample material as bulk,which can be used in mechanistic pavement analysis in the absence of triaxial test results.展开更多
基金support from the projects of Science and Technology Project of Transportation Department of Heilongjiang Province (No. HJK2019B009)the Fundamental Research Funds for the Cornell University (No. 2572021AW10)the Ludong University to Introduce Talents Research Start-up Funding Project (No. 20240050)
文摘To evaluate the regularity of resilient modulus for hot-mix asphalt(HMA) under large temperature fluctuations,back propagation(BP) neural network technology was used to analyze the continuous change of HMA resilient modulus.Firstly,based on the abundant data,the training model of HMA resilient modulus was established by using BP neural network technology.Subsequently,BP neural network prediction and regression analysis were performed,and the prediction model of HMA resilient modulus at different temperatures(-50℃ to 60℃) was obtained,which fully considered multi-factor and nonlinearity.Finally,the fitted theoretical model can be used to evaluate the HMA performance under the condition of large temperature fluctuations,and the rationality of theoretical model was verified by taking Harbin region as an example.It was found that the relationship between HMA resilient modulus and temperatures can be described by inverse tangent function.And the key parameters of theoretical model can be used to evaluate the continuous change characteristics of HMA resilient modulus with large temperature fluctuations.The results can further improve the HMA performance evaluation system and have certain theoretical value.
文摘This study aims to quantify the susceptibility of granular materials used in pavements to changes in moisture content and propose a correlation model to incorporate this susceptibility into seasonal analyses.The fines content and the percentage of fractured coarse aggregates were identified as direct indicators of the resilient modulus susceptibility to changes in water content.The results showed that the percentage of fractured coarse aggregates particles(FR)has a more significant impact on the resilient modulus(Er)of crushed granular materials used in pavement construction than the combined indicator of the fines content and sample volumetrics(nf).Crushed granular materials with a higher percentage of fractured coarse aggregates are relatively insensitive to changes in the degree of saturation,but become more sensitive as the fine fraction porosity decreases.An adjusted model was proposed based on the existing formulation,but considers a complex parameter to describe and adjust the sensitivity of base granular materials to variations in moisture content with respect to fabrication charac-teristics,fines content and volumetric properties.The model shows that the variation of Er values is below10%for fully crushed granular materials.However,it reaches approximately±12%for materials with 75%of crushed coarse aggregates andþ40%and-25%for materials with FR=50%.This model could help select good ag-gregates characteristics and adjust grain-size distribution for environments where significant moisture content variations can occur in the pavement system,such as in the Province of Quebec(Canada).As it is based on pa-rameters that can be easily determined or estimated,it also represents a valuable tool for detailed design and analysis that can consider material characteristics.
基金Projects(41672312, 41972294) supported by the National Natural Science Foundation of ChinaProject(2017CFA056) supported by the Outstanding Youth Foundation of Hubei Province, ChinaProject(KFJ170104) supported by the Changsha University of Science & Technology via Open Fund of National Engineering Laboratory of Highway Maintenance Technology, China。
文摘Although the dynamic properties of subgrade soils in seasonally frozen areas have already been studied, few researchers have considered the influence of shallow groundwater during the freeze–thaw(F–T) cycles. So a multifunctional F–T cycle system was developed to imitate the groundwater recharge in the subgrade during the freezing process and a large number of dynamic triaxial experiments were conducted after the F–T cycles. Some significant factors including the F–T cycle number, compaction degree, confining pressure, cyclic deviator stress, loading frequency, and water content were investigated for the resilient modulus of soils. The experimental results indicated that the dynamic resilient modulus of the subgrade was negatively correlated with the cyclic deviator stress, F–T cycle number, and initial water content, whereas the degree of compaction, confining pressure, and loading frequency could enhance the resilient modulus. Furthermore, a modified model considering the F–T cycle number and stress state was established to predict the dynamic resilient modulus. The calculated results of this modified model were very close to the experimental results. Consequently, calculation of the resilient modulus for F–T cycles considering the dynamic load was appropriate. This study provides reference for research focusing on F–T cycles with groundwater supply and the dynamic resilient moduli of subgrade soils in seasonally frozen areas.
基金Project(51878078)supported by the National Natural Science Foundation of ChinaProject(2018-025)supported by the Training Program for High-level Technical Personnel in Transportation Industry,ChinaProject(CTKY-PTRC-2018-003)supported by the Design Theory,Method and Demonstration of Durability Asphalt Pavement Based on Heavy-duty Traffic Conditions in Shanghai Area,China。
文摘The resilient modulus(MR)of subgrade soils is usually used to characterize the stiffness of subgrade and is a crucial parameter in pavement design.In order to determine the resilient modulus of compacted subgrade soils quickly and accurately,an optimized artificial neural network(ANN)approach based on the multi-population genetic algorithm(MPGA)was proposed in this study.The MPGA overcomes the problems of the traditional ANN such as low efficiency,local optimum and over-fitting.The developed optimized ANN method consists of ten input variables,twenty-one hidden neurons,and one output variable.The physical properties(liquid limit,plastic limit,plasticity index,0.075 mm passing percentage,maximum dry density,optimum moisture content),state variables(degree of compaction,moisture content)and stress variables(confining pressure,deviatoric stress)of subgrade soils were selected as input variables.The MR was directly used as the output variable.Then,adopting a large amount of experimental data from existing literature,the developed optimized ANN method was compared with the existing representative estimation methods.The results show that the developed optimized ANN method has the advantages of fast speed,strong generalization ability and good accuracy in MR estimation.
基金Project supported by the Academy of Scientific Research and Technology,ASRT,Cairo,Egypt
文摘The current study aims to evaluate the dynamic response of stabilized cohesive soil using an enzymatic preparation in terms of resilient modulus.We ran a series of resilient modulus testing according to AASHTO T307 on three types of cohesive soil treated with an enzymatic preparation to investigate its potential on roads construction.The results show significant improvement in the resilient modulus values,estimated at 1.4 to 4.4 times that observed for the untreated soil.Because of the complexity in conducting the resilient modulus measurement,we did a regression analysis to produce reliable correlation formula to predict the resilient modulus for untreated and stabilised soil samples involving stress state.The resilient modulus values for the subgrade materials at the anticipated field stresses were determined using a universal model.The enzymatic preparation was applied in pavement of a sample road and evaluated using the plate load test.SEM analysis for soil samples shows improvement in the soil compaction via reduction of voids between soil particles.XRD analysis shows no major structural changes in the treated soils.The enzymatic preparation contains 43 mg/mL of proteins.We used the SDS-PAGE(sodium dodecyl sulphate polyacrylamide gel electrophoresis)technique to identify the main protein components;however,the presence of interfering materials(surfactants)hinders the separation.
文摘Dynamic cone penetrometer（DCP） has been used for decades to estimate the shear strength and stiffness properties of the subgrade soils. There are several empirical correlations in the literature to predict the resilient modulus values at only a specific stress state from DCP data, corresponding to the predefined thicknesses of pavement layers（a 50 mm asphalt wearing course, a 100 mm asphalt binder course and a200 mm aggregate base course）. In this study, field-measured DCP data were utilized to estimate the resilient modulus of low-plasticity subgrade Piedmont residual soil. Piedmont residual soils are in-place weathered soils from igneous and metamorphic rocks, as opposed to transported or compacted soils.Hence the existing empirical correlations might not be applicable for these soils. An experimental program was conducted incorporating field DCP and laboratory resilient modulus tests on "undisturbed" soil specimens. The DCP tests were carried out at various locations in four test sections to evaluate subgrade stiffness variation laterally and with depth. Laboratory resilient modulus test results were analyzed in the context of the mechanistic-empirical pavement design guide（MEPDG） recommended universal constitutive model. A new approach for predicting the resilient modulus from DCP by estimating MEPDG constitutive model coefficients（k;,k;and k;） was developed through statistical analyses. The new model is capable of not only taking into account the in situ soil condition on the basis of field measurements,but also representing the resilient modulus at any stress state which addresses a limitation with existing empirical DCP models and its applicability for a specific case. Validation of the model is demonstrated by using data that were not used for model development, as well as data reported in the literature.
基金The Science and Technology Project of China Communications Construction(No.2015-ZJKJ-26)
文摘In order to investigate the suction-dependent properties of subgrade granular material and its effect on pavement responses,coupled hydro-mechanical simulations were conducted in Abaqus.A suction-dependent resilient modulus model was integrated into the commercial finite element(FE)code Abaqus by developing a user-defined material(UMAT)subroutine.The developed model was validated by triaxial test results under different suction conditions and good agreement was achieved.A three-dimensional(3D)FE pavement model was established and the suction-dependent properties of subgrade granular material was characterized by the developed constitutive model.Hydro-mechanical pavement responses subjected to three moisture states and the falling weight deflectometer(FWD)load were calculated.Simulation results reveal that the resilient modulus of subgrade granular material is sensitive to suction and stress states;high groundwater table decreases the overall resilient moduli of subgrade structure due to suction reduction,leading to the increase of the maximum surface deflection,the tensile strain at bottom of the surface layer,compressive strain on top of subgrade,and consequently,deterioration in pavement performance.
文摘The performance evaluation of existing flexible pavements has become a priority issue for many highway maintenances engineers.To make appropriate rehabilitation and management decisions,the engineers most often rely on efficient methods for the determination of the strength of pavement layers.Resilient modulus is a very important parameter to be identified and used in pavement design.The resilient moduli of asphalt mixtures are typically measured using the indirect tension test procedure in compliance with the ASTM D4123 standard that is superseded by ASTM D7369.The standard requirement is that the prepared specimens for the tests should have a minimum height of the sample over its diameter ratio of 0.4.Generally,specimens used in the tests are either a nominal 100 mm or 150 mm in diameter with a minimum thickness over diameter ratio of 0.4.However,100 mm diameter core specimens taken from site wearing courses with thicknesses ranging from 40 mm to 50 mm most often do not fulfil the minimum ratio of 0.4 after they are trimmed for testing.Since there was no any option,part of the binder courses had to be trimmed to make up for the minimum ratio requirement.This tends to result in inaccurate assessment of the resilient modulus values of the samples.As such,a new procedure was explored to test specimens smaller than 100 mm in diameter.This may minimize the material volume requirement from the field and also for the fabrication of smaller samples in the laboratory.Based on the available thickness of wearing course or overlay,the appropriate sizes were determined.For a two-layer system a 56.3 mm diameter was deemed necessary while a 37.5 mm diameter was observed to be appropriate for a three-layer system.Such an approach for resilient modulus test using miniature specimens of 56.3 mm and 37.5 mm in diameter has a great potential for practical relevance for the industry.
基金supported by the Jiangxi Provincial Natural Science Foundation of China(Nos.20224BAB214063,20224BAB214064,and 20232BAB204083)the National Natural Science Foundation of China(Nos.52208347 and 52208348)+1 种基金the China Postdoctoral Science Foundation(No.2023M731436)the Key Projects of Jiangxi Provincial Department of Water Resources(No.202426ZDKT01).
文摘Interlayer soil in railway substructures is characterized by a fine/coarse soil mixture.Considering that the resilient modulus M_(r) of the mixture is influenced by the microstructure of fine soil,it is worthwhile to investigate this aspect further.In this study,the microstructure of fines was explored by mercury intrusion porosimetry(MIP),and its influence on the M_(r) of the mixture was studied by multi-stage dynamic triaxial tests with varying deviator stress amplitudesσ_(d).The results showed a fine matrix fabric obtained at water contents of fine soil w_(f)=17.6%and 13.7%(>the plastic limit of fine soil w_(p)=12%),and a fine aggregate fabric identified at w_(f)=10.6%(<w_(p)=12%).Interestingly,the influences of w_(f) andσ_(d) on the M_(r) of the mixture were observed:the rise inσ_(d) contributed to a decline in M_(r) when w_(f)>w_(p) but to an increase in M_(r) when w_(f)<w_(p).It was concluded that,for the fine matrix fabric(w_(f)>w_(p)),increasingσ_(d) induced a reduction in M_(r),while for the fine aggregate fabric(w_(f)<w_(p)),increasingσ_(d) gave rise to the growth of M_(r).The distinct M_(r)-σ_(d) behaviors for these two fabrics were explained by the competing influences between soil hardening upon loading and soil rebounding upon unloading.For the fine matrix fabric(w_(f)>w_(p)),considering its high deformability,the rebounding effect on M_(r) outweighed the hardening effect,and thus a decline in M_(r) occurred with the growth ofσ_(d).Conversely,for the fine aggregate fabric(w_(f)<w_(p)),the rebounding effect on M_(r) was secondary compared with the hardening effect based on the consideration of its low deformability,and thus an increase in M_(r) was observed with risingσ_(d).
文摘The fatigue behavior, indirect tensile strength （ITS） and resilient modulus test results for warm mix asphalt （WMA） as well as hot mix asphalt （HMA） at different ageing levels were evaluated. Laboratory-prepared samples were aged artificially in the oven to simulate short-term and long term ageing in accordance with AASHTO R30 and then compared with unaged specimens. Beam fatigue testing was performed using beam specimens at 25 ℃ based on AASHTO T321 standard. Fatigue life, bending stiffness and dissipated energy for both unaged and aged mixtures were calculated using four-point beam fatigue test results. Three-point bending tests were performed using semi-circular bend （SCB） specimens at -10 ℃ and the critical mode I stress intensity factor K1 was then calculated using the peak load obtained from the load-displacement curve. It is observed that Sasobit and Rheofalt warm mix asphalt additives have a significant effect on indirect tensile strength, resilient modulus, fatigue behavior and stress intensity factor of aged and unaged mixtures.
基金Funded by the National Science&Technology Support Program during the 12th Five-year Plan Period(No.2014BAG05B04)the Construction and Science Project of the Ministry of Transport of China(No.2013 318 490 010)the Doctor Postgraduate Technical Project of Chang’an University(No.2014G5210002)
文摘Low average temperature, large temperature difference and continual freeze-thaw （F-T） cycles have significant impacts on mechanical property of asphalt pavement. F-T cycles test was applied to illustrate the mixtures＇ compressive characteristics. Exponential model was applied to analyze the variation of compressive characteristics with F-T cycles; Loss ratio model and Logistic model were used to present the deterioration trend with the increase of F-T cycles. ANOVA was applied to show the significant impact of F-T cycles and asphalt- aggregate ratio. The experiment results show that the compressive strength and resilient modulus decline with increasing F-T cycles; the degradation is sharp during the initial F-T cycles, after 8 F-T cycles it turns to gentle. ANOVA results show that F-T cycles, and asphalt-aggregate ratio have significant influence on the compressive characteristics. Exponential model, Loss ratio model and Logistic model are significantly fitting the test data from statistics view. These models well reflect the compressive characteristics of asphalt mixture degradation trend with increasing F-T cycles.
文摘This article explains the results of a study conducted on the characterizations of subgrade soils in the region of Thies. The road platforms are mainly composed of a background soil, which is generally overlapped by a surface layer that plays two roles. Firstly, it protects the soil structure, ensures the leveling, and facilitates the movement of vehicles. Secondly, it brings harmony in the mechanistic characteristics of the materials that compose the soil while improving the long-term life force. The methodology consisted in taking samples of subgrade soil along the roads all over the region of Thies in a 5 km diameter span. The identification tests allowed the Thies-Tivaoune, Thies-Khombole and Thies-Noto axes are characterized by tight sands, poorly graded size. While Thies Pout-axis is characteristic of severe solid particle size and spread well graded and serious to spread and well graded particle size. Finally the Thies-Montrolland axis is characterized by severe to very tight particle size and graduated to spread and serious and well graded particle size. The specific gravity values found Proctor test shows the presence of sand, sandy laterite and laterite. In the target area, polished soils of the A-3 type according to the AASHTO classification system are the most represented with 60%, followed by the A-2-6 type 25%, and the A-2-4 type with 9%, which are typical of gravel, clay, and silty sands. Soils of the A-1-b type (2%) typical of roc fragments, sands and clay are also represented. Polished sands of the A-3 type have a better efficiency on road infrastructures than other types of soil listed above. Finally, we’ve also noted the presence of soils of the A-2-7 and A-4 types with the low percentage of 2%. Subgrade soils of class S4 are the most represented with 58%, followed by those of class S5 with 42%. Samples of the Thies-Montrolland road have a claylike plasticity (CL or CH group), while those of the Thies-Pout road belong to the ML or OL and CL or OL groups with a tendency mostly directed to the CL or OL group. All these results confirm the very nature of soils on the two roads and put the light on the presence of lateritic materials with certain plasticity.
文摘This paper will visually and experimentally assess the level of deterioration of one of the new constructed ring road pavements in Khartoum State as well as to examine and identify the causes of the failed pavement. A series of field and laboratory exercises were carried out on the materials that were used in the construction of the designated pavement. Huttab, a natural gravelly material, was used in both subbase and base blend of this deteriorated pavement. The experimental tests consisted of two tasks： the first covered the study of the actual causes of pavement distress, whereas the second explored typical base material alternatives that satisfy base course needs. The tests involved basic tests and dynamic tests such as sieve, Atterberg limits, linear shrinkage, compaction, CBR （Calitbrnia bearing capacity）, abrasion whereas the dynamic tests included MR （resilient modulus）, and PD （permanent deformation）. The routine tests showed that an improper base blend was used in the failed road that resulted in excessive rutting whereas in the second tests scenario the results showed that the proper base blend from the named materials gave high strength and stiffness values and low PD compared to the natural one. On the other hand, the pure crushed sample reported high MR values and the lowest PD compared to the base blend alternative.
文摘Ceramic waste materials are abundantly available in Malaysia from the production of ceramic tiles.In general,ceramic materials seem to possess low thermal conductivity characteristics that could reduce pavement temperatures when used as aggregates in asphalt mixtures.A study was undertaken to look into the performance of crushed ceramics incorporated in asphalt mixtures to replace the conventional granite aggregates from sizes 5.0 mm down including the 75 micron filler.The replacement was done proportionally with 0%,20%,40%,60%,80%and 100%ceramic aggregates by weight of granite.Several mix designs with various percentages of ceramic aggregates were formulated to determine the marshal properties such as stability,flow,and resilient modulus.In addition,the potential of ceramic aggregates in reducing the asphalt pavement temperatures was also studied.The outcome of the study showed that the ceramic aggregates in the asphalt mixtures were able to improve the performance of the mixture up to 20%which means there is a great potential for the use of it in road construction.Besides that,the rate of heating(RoH)compacted samples subjected to various temperatures dropped significantly as compared with the control granite specimens.The fatigue performance of the compacted and temperature conditioned ceramic asphalt mixtures displayed an interesting trend in terms of strain resistance at elevated temperatures.
文摘The mechanical characteristics of road pavement layers are influenced by moisture conditions. Drying and wetting change the moisture content of the materials used in pavement structures, consequently affecting the mechanical response. An experimental program was conducted to evaluate elastic deformations of a road pavement structure utilizing repetitive rigid plate load tests in a model test-pit facility. A typical Brazilian pavement （a multilayer system composed of a concrete asphalt and coarse base, and subbase） was simulated in this test-pit with devices for measuring humidity （TDR （time domain reflectometry）） and suction （tensiometers） installed every 20.0 cm along the profile. A pair of displacement transducers was attached on the surface of the pavement structure to record deformations due to dynamic loads. Two levels of groundwater table were analyzed, verifying that the pavement structure displacement increases with groundwater table growth. The structural response was evaluated and compared in physical and numerical models, and the results confirmed that the higher groundwater levels caused the greatest pavement displacements.
文摘Stone Matrix Asphalt(SMA)is a gap graded mix;characterized by higher proportion of coarse aggregate,lower proportion of middle size aggregate and higher proportion of mineral filler.In the present laboratory study,commonly available one conventional VG 30 bitumen and another modified binder,namely CRMB 60 have been used along with a non-conventional natural fiber,namely coconut fiber which is abundantly available in India to provide improved engineering properties and at the same time preventing the usual draining of binder in SMA.The role of a particular binder and fiber with respect to their concentrations in the mix is studied for various engineering properties.Marshall procedure has been followed to determine the optimum binder and optimum fiber contents and also to study the relative advantages of fiber addition in the SMA mixtures.Thereafter,the engineering properties under both static as well as repeated load conditions and moisture susceptibility characteristics have been studied.It is observed that only a marginal 0.3%coconut fiber addition brings significant improvement in the engineering properties of SMA mixes.
文摘T<span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">his research was carried out to determine the rheological parameters of lateritic soils in order to contribute to the improvement of the technical documents used for pavement design in tropical Africa. The study is based on the loading repeated of cyclic triaxial tests (LRT) performed at </span><span style="font-family:Verdana;">University Gustave Eiffel (formerly Institut Fran<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">ç</span>ais des Sciences et Technologies des Transports de l’Aménagement et des Réseaux (IFSTTAR))</span></span></span></span><span><span><span><span style="font-family:;" "=""> </span></span></span></span><span></span><span><span><span style="font-family:Verdana;">in Nantes with the application of the European standard EN 13286-7: 2004</span><span style="font-family:Verdana;"> [<a href="#ref1">1</a>]</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">. The tests were performed at constant confinement stress and using the stepwise method to determine the resilient axial (<img src="Edit_9d1c29ae-1a5f-434a-9fe3-00ef5aeb5d24.png" alt="" /></span></span></span><span><span><span style="font-family:;" "=""><span><span style="font-family:Verdana;">) and radial (<img src="Edit_42548459-8f50-4ea1-832d-25e9cfdad034.png" alt="" /></span><span style="font-family:Verdana;">) deformation as a function of the axial and radial stresses. Four gravel lateritic soil</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">s</span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"> from different sites selected in Burkina Faso and Senegal were the subject of this research for the triaxial tests. These materials have a maximum diameter of 20 mm and a percentage of fines less than 20%. The LRT tests were carried out on samples compacted at three moisture contents (</span><i><span style="font-family:Verdana;">w</span><sub><span style="font-family:Verdana;">opm</span></sub></i> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">-</span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"> 2%, </span><i><span style="font-family:Verdana;">w</span><sub><span style="font-family:Verdana;">opm</span></sub></i><span style="font-family:Verdana;"> and </span><i><span style="font-family:Verdana;">w</span><sub><span style="font-family:Verdana;">opm</span></sub> </i><span style="font-family:Verdana;">+ 2%) and at 95% and 100% of optimal dry density (</span></span></span></span><span><span><i><span style="font-family:;" "=""><span style="font-family:Verdana;">γ</span><sub><span style="font-family:Verdana;">dopm</span></sub></span></i></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">). Test results showed that the characteristic resilient Young’s modulus (</span><i><span style="font-family:Verdana;">E</span><sub><span style="font-family:Verdana;">c</span></sub></i><span style="font-family:Verdana;">) of gravelly laterites soils depends on the compacted water content and the variation of the grains size distribution (sand (</span><i><span style="font-family:Verdana;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">ø</span></span></i><span style="font-family:Verdana;"> < 2 mm), motor (</span><i><span style="font-family:Verdana;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">ø</span></span></i><span style="font-family:Verdana;"> < 0.5 mm) and fines content (</span><i><span style="font-family:Verdana;"><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">ø</span></span></i><span style="font-family:Verdana;"> < 0.063 mm) obtained after (LRT). Materials with a high percent of fines (>20%), mortar and sand (Sindia and Lam-Lam) are more sensitive to variations in water content. The presence of water combined with the excess of fines leads to a decrease in modulus around 25% for Lam-Lam and 20.2% for Sindia. Materials containing a low percent of fines, mortar and sand (Badnogo and Dedougou) behave differently. </span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">And </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">the resilient modulus increases about 225</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">.</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">67% for Badnogo and 312.24% for Dedougou with the rise of the water content for approximately unchanged the percentage of fines, mortar and sand. Granularity therefore has an indirect influence on the resilient modulus of the lateritic soils by controlling the effects of water on the entire system. </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">Results of statistical analysis and coefficients of correlation (0.659 to 0.865) showed that the anisotropic Boyce’s model </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">is suitable to predict</span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;"> the volumetric </span><span style="font-family:Verdana;">(<img src="Edit_1a36888c-cad0-4f1c-9c68-b5da0ddc323f.png" alt="" /></span><span style="font-family:Verdana;">)</span><span style="font-family:Verdana;"> and deviatoric strain (<img src="Edit_993added-0ec4-49db-ae12-3e540fa49f9c.png" alt="" /></span><span style="font-family:Verdana;">)</span><span style="font-family:Verdana;"> with stress path (Δ</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><i><span style="font-family:Verdana;">q</span></i></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">/Δ</span><i><span style="font-family:Verdana;">p</span></i><span style="font-family:Verdana;">) of the lateritic soils. </span><span><span style="font-family:Verdana;">The predicted </span><i><span style="font-family:Verdana;">E</span><sub><span style="font-family:Verdana;">r</span></sub></i><span style="font-family:Verdana;"> resilient Young’s modulus from anisotropic Boyce’s model varies according to the evolution of </span></span><span style="font-family:Verdana;">the bulk stress (<img src="Edit_ab550c56-8bab-4806-9ec7-fab794d785eb.png" alt="" /></span><span style="font-family:Verdana;">). A correlation around 0.9 is obtained from the power law model.</span></span></span></span></span>
基金This work was supported by Universiti Tenaga Nasional(UNITEN)through BOLD Refresh Publication Fund 2021 under Grant J5100D4103-BOLDREFRESH2025-CENTRE OF EXCELLENCE.
文摘Vigorous and continued efforts by researchers and engineers have contributed towards maintaining environmental sustainability through the utilization of waste materials in civil engineering applications as an alternative to natural sources.In this study,granite aggregates in asphaltic mixes were replaced by electric arc furnace(EAF)steel slag aggregates with different proportions to identify the best combination in terms of superior performance.Asphalt mixtures showing the best performance were further reinforced with polyvinyl alcohol(PVA),acrylic,and polyester fibers at the dosages of 0.05%,0.15%,and 0.3%by weight of the aggregates.The performance tests of this study were resilient modulus,moisture susceptibility,and indirect tensile fatigue cracking test.The findings of this study revealed that the asphalt mixtures containing coarse steel slag aggregate exhibited the best performance in comparison with the other substitutions.Moreover,the reinforced asphalt mixtures with synthetic fibers at the content of 0.05%exhibited an almost comparable performance to the unreinforced asphalt mixtures.Modifying the asphalt mixtures with PVA,acrylic,and polyester fibers at the proportion of 0.15%have improved the fatigue cracking resistance by 41.13%,29.87%,and 18.97%,respectively.Also,the fiber-modified asphalt mixtures with PVA,acrylic,and polyester have enhanced the fatigue cracking resistance by about 57%,44%,and 39%,respectively.The results of the resilient modulus demonstrated that as the fiber content increase,the resilient modulus of the reinforced asphalt mixtures decreases.Therefore,introducing synthetic fibers at the content of 0.3%has slightly decreased the resilient modulus in comparison with unreinforced mixtures.On the other hand,the results of the mechanisticempirical pavement design showed that the reinforced asphalt mixes with a high content of synthetic fibers have shown lower service life than the control mixes due to the low resilient modulus.On the contrary,based on the laboratory results,the asphalt mixes incorporating PVA,acrylic,and polyester fibers at the proportion of 0.15%have shown the potential to reduce the thickness of the asphalt layer by about 14.9%,11.80%,and 8.70%,respectively.
基金This work was partially carried out under the framework of In2Track,a research project of Shift2Rail.This work was partly financed by FCT/MCTES through national funds(PIDDAC)under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering(ISISE)under reference UIDB/04029/2020It has been also financially supported by national funds through FCT—Foundation for Science and Technology,under grant agreement[PD/BD/127814/2016]attributed to Ana Ramos.
文摘The type of subgrade of a railroad foundation is vital to the overall performance of the track structure.With the train speed and tonnage increase,as well as environmental changes,the evaluation and influence of subgrade are even more paramount in the railroad track structure performance.A geomechanics classification for subgrade is proposed coupling the stiffness(resilient modulus)and permanent deformation behaviour evaluated by means of repeated triaxial loading tests.This classification covers from fine-to coarse-grained soils,grouped by UIC and ASTM.For this achievement,we first summarize the main models for estimating resilient modulus and permanent deformation,including the evaluation of their robustness and their sensitivity to mechanical and environmental parameters.This is followed by the procedure required to arrive at the geomechanical classification and rating,as well as a discussion of the influence of environmental factors.This work is the first attempt to obtain a new geomechanical classification that can be a useful tool in the evaluation and modelling of the foundation of railway structures.
文摘A new characterization technique,a repeated load CBR test,was used to evaluate the resilient properties recycled mix-granulate unbound base material. This is a mixture of crushed concrete and crushed masonry,so recycled demolition waste,this is used on a wide scale in the Netherlands as road base material. The repeated load CBR test,done with standard CBR testing facility,was conducted to estimate the resilient modulus. For comparison and assessment purposes the tests were carried out with the same material conditions (composition,grading,moisture and compaction degree) as have been applied in earlier triaxial testing in the Road and Railway Engineering Laboratory,Delft University of Technology. The results indicate that the repeated load CBR test yields a good estimate of the stress dependent equivalent modulus for the sample material as bulk,which can be used in mechanistic pavement analysis in the absence of triaxial test results.
