冻融循环对黏质粗粒土抗剪强度影响的试验研究

通过室内循环冻融循环试验和三轴不固结不排水(UU)压缩试验研究了循环冻融作用与细砾组含量(P2-5)对黏质粗粒土抗剪性能的影响。结果表明,冻融循环作用对黏质粗颗粒土的应力-应变曲线性状具有一定的影响,可使其由未冻融的应变软化向应变硬化转变的趋势,但随着细砾组P2-5含量的增加,冻融作用对其影响逐渐减弱。随着冻融循环次数的增加,土样剪切强度呈现逐渐衰减,且在5~9次冻融循环次数后基本保持不变,多次循环冻融作用后剪切强度最大衰减幅度可达40%。弹性模量随冻融循环次数的增加上下波动较大但整体呈现下降趋势。在抗剪强度指标方面,冻融作用对黏聚力影响比较显著,随着冻融循环次数的增加,黏聚力逐渐减小,最大衰减幅度可达65%,而内摩擦角上下波动较大无明显趋势。此外,随着细砾组P2-5含量的增加,剪切强度、弹性模量及抗剪强度指标均呈现不同程度的减小,这与粗粒土内部粗颗粒和细颗粒占比及其强度发挥机制有关。

Experimental Study on Effect of Cyclic Freeze-thaw on Shear Behaviors of Clayey Coarse-grained Soil

Effects of freeze-thaw cycles and fine gravel P_2-5 contents on the shear behaviors of clayey coarse grained soils were studied by triaxial unconsolidated-undrained (UU) compression tests. The test results show that the stress-strain curves of coarse-grained clayey soils tend to change from strain softening to strain hardening if increasing the frequency of freeze-thaw cycles. However, with the increase in P_2-5 contents, such change becomes slighter. The shear strength decreases gradually if increasing the frequency of freeze-thaw cycles, and tends to be stable after 5-9 freeze-thaw cycles. The maximum decrease in the shear strength can be as much as 40%. Moreover, the elastic modulus fluctuates considerably and shows a decrease trend after the freeze-thaw cycles. In terms of the shear strength parameters, the cyclic freeze-thaw effect is more significant on cohesion. The cohesion decreases with increase in freeze-thaw cycles, and the maximum decrease reaches 65%, but there was no obvious regulation for the internal friction angle. In addition, the shear strength, the elastic modulus and the shear strength parameters decrease by different degrees with increase in P_2-5 contents. The decrease is related to the proportion of coarse and fine particles in the coarse grained soil.