不同吸力和应力路径下Q_(3)原状黄土的力学特性

Study on Mechanical Properties of Q_(3)Undisturbed Loess Under Different Suctions and Stress Paths

为了研究吸力和应力路径对兰州Q_(3)原状黄土应力应变、临界状态和强度等力学特性的影响,用GDS非饱和三轴仪对不同吸力原状黄土试样进行了应力路径(等向压缩(IC),常规三轴剪切(CTC),等平均应力三轴剪切(TC),减围压三轴剪切(RTC))压缩试验,试验结果表明:(1)随着吸力的增加,试样的弹性指数变化不大,而结构屈服应力和塑性指数增加;(2)应力路径和吸力对原状黄土的初始模量、硬化程度、抗剪强度、剪缩剪胀有明显影响,随着吸力增大,RTC路径下的应力应变曲线出现软化和剪胀现象,不同剪切路径下试样破坏偏应力大小顺序为CTC>TC>RTC;(3)不同应力路径的q-p和v-lgp临界状态点皆收敛在一条直线上,不同吸力下的临界状态线近似平行,不同吸力和应力路径的q-p和v-lgp临界状态线可以进行归一,并提出了统一临界状态方程;(4)随着吸力的增加,原状黄土的内粘聚力增加,而内摩擦角几乎不变,应力路径对抗剪强度参数没有影响。

In order to study the influence of suction and stress path on the mechanical properties of Q_(3)intact loess in Lanzhou,such as stress-strain,critical state and strength,stress path compression tests(IC,CTC,TC,RTC)were carried out on unsaturated loess samples with different suctions using a GDS unsaturated triaxial instrument.The test results show that:(1)with the increase of suction,the elastic index of the specimen does not change much,while the structural yield stress and plastic index increase;(2)the initial modulus,hardening degree,resistance of undisturbed loess to the stress path and suction shear strength,shrinkage and dilatancy have obvious effects,with the increase of suction,the stress-strain curves under RTC path appear softening and dilatancy,and the order of sample failure deviatoric stress under different shear paths is CTC>TC>RTC;(3)The critical state points of q-p and v-lgp of different stress paths converge on a straight line,the critical state lines under different suctions are approximately parallel.The q-p and v-lgp critical state lines for different suctions and stress paths can be normalized,and unified critical state equations were proposed.(4)As the suction increases,the cohesion increases,while the internal friction angle is almost unchanged;stress paths have no effect on shear strength parameters.