摘要
为了研究开挖扰动对花岗岩的破坏机理,对北山花岗岩进行了加轴压卸围压的三轴试验,试验中设置0.1,0.5,1.0,1.5,2.0 MPa/min五种卸围压速率,轴压加载速率是卸载速率的10倍,每一种卸载速率设置5,10,15,20,30 MPa五个围压,并在试验过程中记录声发射事件。分析了声发射事件数随卸载速率的变化规律,使用层次聚类的方法将声发射事件分为张拉破坏和剪切破坏,研究了卸载速率、围压和卸载时间对张剪比(张拉破坏与剪切破坏的比值)的影响,研究表明:(1)随着卸载速率的增加,声发射事件数呈幂函数下降,且围压越高,声发射事件数下降越明显;(2)裂纹的张剪比随着卸载速率的增加而增加,随着围压的增加减小,随着卸载时间增加降低;(3)围压卸载速率增加,岩石声发射b值降低,初始围压升高,对应的b值增加,且卸载速率和围压对张拉b值的影响比对剪切b值影响更明显;(4)基于Maxwell模型分析岩石内局部应力状态,并进一步研究了岩石破坏过程中张剪比变化的力学机理。
To better understand the effects of unloading confining pressure on failure mechanism,several trial tests on loading axial stresses and unloading confining pressures with different unloading rates are performed,and acoustic emission events are recorded at the same time.In the experiment,five unloading confining pressure rates are set at 0.1,0.5,1.0,1.5 MPa/min and 2.0 MPa/min,and the axial stress loading rate is 10 times the unloading confining pressure rate.Five confining pressures are set at 5,10,15,20 and 30 MPa under every unloading rate.The variation laws of the acoustic emission events with the unloading rates are analyzed,the hierarchical clustering is used to divide the acoustic emission events into tensile failure and shear failure,and the effects of unloading rate,confining pressure,unloading time on the tensile and shear failures are investigated.The results show:(1) The acoustic emission decreases in the form of power function with the increase of the unloading rate,and the effects of the unloading rate on the acoustic emission are more obvious when the confining pressure increases;(2) The ratio of tensile to shear fractures increases with the increasing unloading rate,but it decreases with the increasing confining and unloading time;(3) b-values decrease with the increase of the confining pressure unloading rate and increase when the confining pressure increases,and the influences of the unloading rate and confining pressure on the b-values of the tension fractures are more obvious than those on b values of shear fractures;(4) The local stress state is analyzed by using the Maxwell model,and the mechanism of variation of tensile and shear fractures is further studied.
作者
王超圣
周宏伟
王睿
王子辉
何树生
刘建锋
WANG Chao-sheng;ZHOU Hong-wei;WANG Rui;WANG Zi-hui;HE Shu-sheng;LIU Jian-feng(School of Mechanics and Civil Engineering,China University of Mining and Technology,Beijing 100083,China;School of Water Resources and Hydropower,Sichuan University,Chengdu 610065,China)
出处
《岩土工程学报》
EI
CAS
CSCD
北大核心
2019年第2期329-337,共9页
Chinese Journal of Geotechnical Engineering
基金
十三五国家重点项目(2016YFC0600704)
国家自然科学基金项目(51674266)
关键词
北山花岗岩
加卸载速率
声发射
拉破坏
剪破坏
B值
Beishan granite
loading and unloading rate
acoustic emission
tensile failure
shear failure
b-value