低应力及拉应力条件下非饱和土强度及剪胀特性  

The strength and dilatancy characteristics of unsaturated soil at low and tensile stresses

作　　者：徐筱 蔡国庆[1,2] 李舰[1,2] 赵成刚[2,3] XU Xiao;CAI Guoqing;LI Jian;ZHAO Chengang(Key Laboratory of Urban Underground Engineering of Ministry of Education,Beijing Jiaotong University,Beijing 100044,China;School of Civil Engineering,Beijing Jiaotong University,Beijing 100044,China;College of Civil Engineering;rchitecture,Guilin University of Technology,Guilin,Guangxi541004,China)

机构地区：[1]北京交通大学城市地下工程教育部重点实验室,北京100044 [2]北京交通大学土木建筑工程学院,北京100044 [3]桂林理工大学土木与建筑工程学院,广西桂林541004

出　　处：《岩石力学与工程学报》2018年第8期1933-1942,共10页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金优秀青年基金项目(51722802);国家自然科学基金面上项目(51478135);河南省交通运输科技计划项目(2017B4)~~

摘　　要：利用宽广含水率变化范围内非饱和压实土低应力下的直剪试验和抗拉强度试验,研究非饱和土的强度及剪胀特性。试验结果表明:含水率低于塑限时,非饱和土剪切时出现应变软化型破坏和剪胀性;宽广含水率变化范围内,非饱和土峰值剪切强度、最小剪胀率及单轴抗拉强度均随着含水率的增加先增加后减小,变化趋势相同。基于试验结果,首先,对非饱和土拉应力区的Mohr-Coulomb强度包线进行修正。其次,验证修正的Bishop非饱和土抗剪强度模型预测性较差,并分析这种模型广为流行的原因。最后,得到吸力对非饱和土峰值抗剪强度的贡献来源于吸力引起的颗粒间的拉应力和剪胀作用两方面,其中吸力应区分毛细和吸附作用,并可用单轴抗拉强度近似表征拉应力的大小。The strength and dilation behavior of unsaturated compacted soils was investigated via low-stress direct shear and direct tensile tests over a wide range of water contents. The results show that the unsaturated soils with the water content below the plastic limit exhibit the characteristics of strain softening and shear dilation. The peak shear strength,the minimum dilation rate and the uniaxial tensile strength of unsaturated soils over a wide range of water contents increase and then decrease with the increasing of water content similarly. A modified Mohr-Coulomb strength envelope in tensile stress regime for unsaturated soils is proposed based on the test results. It is verified that the revised Bishop＇s shear strength model predicts the effect of suction on the shear strength poorly,and the reason why this model is popular is analyzed. Finally,it is suggested that the contribution of suction on the peak shear strength can be described in terms of the effect of suction on interparticle tensile stress and shear dilation,in which the suction is the sum of capillary and adsorptive processes,and the interparticle tensile stress is approximated by the uniaxial tensile strength.

关 键 词：土力学 非饱和土 低应力 拉应力 抗剪强度 剪胀作用 

分 类 号：TU43[建筑科学—岩土工程]