摘要
为增加试样饱和度而采用反压饱和是室内三轴试验中普遍采用的技术手段,但现行规范对试样中反压取值没有具体规定。通过对福建标准砂的一系列固结不排水和固结排水三轴试验,分析了不同反压、围压下饱和砂土的应力–应变关系、孔压发展规律,并分析了几种常用破坏取值标准下土体强度指标的差异。试验结果表明固结不排水三轴试验中,反压对砂土应力应变关系、孔压发展有明显影响,从而影响强度取值;而在固结排水试验中,施加不同的反压对于砂土抗剪强度则基本无影响。在不排水剪切中,建议反压设为300～500 kPa,且在同一组试样中采用统一的反压对试样进行饱和。在破坏标准上,建议采用最大有效主应力比(1/3)max对应强度作为砂土的不排水抗剪强度;而在考虑土体残余强度时,建议采用超静孔压下降为零为破坏标准。
The back pressure saturation method is commonly adopted in triaxial tests to increase the saturation degree of samples. But the value of the back pressure is not stipulated in Chinese standards nowadays. To investigate the back pressure effects, a series of triaxial tests are carried out on Fujian standard sand. The stress-strain relationship of saturated soils under different back pressures and confining pressures is analyzed, and the development of pore pressure is obtained. The effective friction angle obtained from different failure criteria are also deduced. The test results reveal that the back pressure plays an important role in the undrained shearing behaviors of dilative soils, however, it seems to produce no effect on drained condition. According to the test results, it is suggested that, the back pressure should be 300~500 kPa, and be equal in one series of tests. In undrained shear test the strength corresponding to the maximum effective principal stress ratio （1/3）max is recommended as the maximum undrained shear stength. While the residual stress of soils needs to be considered, Au=0 （excess pore pressure equal to zero） could be the failure criterion.
出处
《岩土工程学报》
EI
CAS
CSCD
北大核心
2012年第7期1313-1319,共7页
Chinese Journal of Geotechnical Engineering
基金
地震行业科研专项(200808022)
国家自然科学基金项目(50708095
51178427)
国家重点基础研究发展计划项目(2007CB714203)
关键词
反压
剪胀性
抗剪强度
三轴试验
back pressure
dilatancy
shear strength
triaxial test
