延安Q3黄土应力应变特性及其归一化性状研究

Study on Stress-strain Characteristics and Normalized Characters of Q3 Loess in Yan an

为研究延安原状Q 3黄土应力应变关系特性,并总结其在不同含水率不同围压下的归一化性状,进行了一系列固结不排水三轴剪切试验。试验结果表明:延安原状Q 3黄土的应力应变关系整体上随围压增大由弱硬化型向强硬化型转变,但在含水率极低且低围压条件下会呈现出一定的软化特性;基于Kondner双曲线模型,对原状Q 3黄土进行应力应变归一化分析,含水率为5%、10.2%的Q 3黄土在400 kPa以下的围压下不存在归一化性状,含水率为17%的Q 3黄土在300 kPa以上的围压下存在归一化性状,含水率为22%、27%和32%的Q 3黄土在200 kPa以上的围压下归一化性状较显著;通过比较,选用初始切线模量或极限偏应力作为延安原状Q 3黄土的归一化因子,归一化效果较好;建立了不同含水率下延安原状Q 3黄土应力应变关系的归一化方程,其预测值与试验值较接近。该方程对延安Q 3黄土相关工程设计及工程经验的验证有一定参考价值。

A series of consolidated undrained triaxial shear tests were carried out to study the stress-strain relationship of undisturbed Q 3 loess in Yan’an,Shaanxi,China,and to summarize its normalized behavior under a different water content and confining pressure.The test results show that the stress-strain relationship of undisturbed Q 3 loess in Yan’an changed from weak hardening type to strong hardening type with the increase of confining pressure,but it shows certain softening characteristics under the condition of extremely low water content and low confining pressure.Based on Kondner hyperbolic model,the stress-strain normalization analysis of undisturbed Q 3 loess was carried out.The Q 3 loess with water content of 5%and 10.2%did not have normalized behavior under confining pressure below 400 kPa;the Q 3 loess with 17%water content showed normalized behavior under confining pressure above 300 kPa;and the Q 3 loess with moisture content of 22%,27%,and 32%had obvious normalization behavior under confining pressure above 200 kPa.Through comparison,the initial tangent modulus or ultimate deviator stress were selected as the normalization factor of the undisturbed Q 3 loess,and the normalization effect was improved.The normalized equations of stress-strain relationship of undisturbed Q 3 loess under different water contents in Yan’an were established.The predicted values were close to the experimental value.The equations shall have a certain reference value for the engineering design related to the Yan’an Q 3 loess and for the verification of experience.