粗粒土在三向卸载时的强度特性试验研究  

Experimental study on the strength characteristics of coarse-grained soil under three-dimensional unloading

作　　者：施维成[1] 朱俊高[2] 胡锡鹏 代国忠[1] 李雄威[1] 李书进[1] Shi Weicheng;Zhu Jungao;Hu Xipeng;Dai Guozhong;Li Xiongwei;Li Shujin(School of Civil Engineering&Architecture,Changzhou Institute of Technology,Changzhou 213032,Jiangsu,P.R.China;Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering,Hohai University,Nanjing 210098,P.R.China;CCCC Third Highway Engineering CO.,LTD,Beijing 101300,P.R.China)

机构地区：[1]常州工学院土木建筑工程学院,江苏常州213032 [2]河海大学岩土力学与堤坝工程教育部重点实验室,南京210098 [3]中交第三公路工程局有限公司,北京101300

出　　处：《土木与环境工程学报（中英文）》2020年第2期10-16,共7页Journal of Civil and Environmental Engineering

基　　金：国家自然科学基金(51678083);常州市科技支撑计划(CE20195034)。

摘　　要：卸载是引起岩土材料破坏的常见工况,为了研究粗粒土在不同中主应力系数b情况下三向卸载时的强度特性,使用真三轴仪对粗粒土进行偏应力q保持300kPa不变,球应力p不断减小的等q、等b三向等量卸载试验,分析三向卸载条件下粗粒土的强度特性,研究常用强度准则对卸载条件粗粒土的适用性。试验结果表明:在三向等量卸载条件下,粗粒土的强度参数与中主应力系数b有关;对于不同的b值,b=0时的内摩擦角φb最小,破坏应力比Mb最大;破坏应力比Mb随着b的增大而减小,且随着b的增大,减小的梯度在逐渐减小;内摩擦角φb在b值较小时随着b的增大而增大,在b值较大时随着b的增大而减小,3个方向剪切的共同影响可以解释这一变化规律;Matsuoka-Nakai强度准则、粗粒土应力不变量强度准则和Lade-Duncan强度准则这3个强度准则都能反映内摩擦角φb与b之间的这一规律,其中,Matsuoka-Nakai强度准则在b值较小时与试验结果较为接近,粗粒土应力不变量强度准则在b值较大时与试验结果较为接近;粗粒土角隅函数强度准则与等q、等b试验结果较为吻合。Unloading is a common condition that causes damage to geotechnical materials.In order to investigate the strength characteristics of the coarse-grained soil under three-dimensional unloading in different cases of the coefficient of intermediate principal stress b,several three-dimensional equal unloading tests in which the spherical stress pdecreases with constant b and constant deviatoric stress q(300 kPa)were performed on coarse-grained soil by using true triaxial apparatus.The strength characteristics of coarse-grained soil were analyzed and the applicability of the commonly used strength criterions was studied.The test result shows that under the condition of three dimensional equal unloading,the strength parameter of coarse-grained soil is related to the coefficient of intermediate principal stress b.When bequals to 0,the internal friction angle φb is the minimum and the failure stress ratio Mbis the maximum.The stress ratio at failure decreases with the increase of b and,as b increases the gradient decreases gradually.The internal friction angle increases with b for small b values while decreases with the increase of b for large values.This can be explained by the co-impact of the shearing in three directions.All of the three strength criterions,including the Matsuoka-Nakai criterion,the criterion expressed by stress invariants of coarsegrained soil and Lade-Duncan criterion,can response the law betweenφband b.It is found that the Matsuoka-Nakai criterion is the closest to the test results for small b values while the strength criterion expressed by stress invariants of coarse-grained soil is the closest to the test results for large b values.It is also found that the corner function strength criterion of coarse-grained soil is consistent with the experimental results.

关 键 词：强度准则 粗粒土 强度参数 卸载 加载 

分 类 号：TU447[建筑科学—岩土工程]