循环荷载下地铁隧道基底风化泥质粉砂岩动力特性研究

Dynamic characteristics of weathered argillaceous siltstone under cyclic loading in subway tunnel base

通过对强、中风化泥质粉砂岩进行动三轴循环加载试验,对其低频循环荷载作用下不可恢复累积塑性动应变的发展规律进行研究,分别从不同动应力、静偏应力、围压、频率4个方面入手,对风化泥质粉砂岩的轴向动应变规律进行分析及对不同因素的影响程度进行比较。并对试验数据进行非线性拟合,建立强、中风化泥质粉砂岩在振动荷载作用下的累积应变预测模型。研究结果表明:强、中风化泥质粉砂岩在循环振动荷载作用下的动应变情况受动应力、静偏应力2因素影响较大,并随其增加而增大,但中风化泥质粉砂岩动应变趋于稳定需要的循环次数为2 000次左右,而强风化泥质粉砂岩仅需要1 000次左右;静偏应力从0 kPa增加至200 kPa,中风化泥质粉砂岩的动应变约增长5.97倍,而强风化泥质粉砂岩的动应变则增长约8.53倍,变化更为明显;围压的增大加速了强风化泥质粉砂岩样内部裂隙发展,而中风化泥质粉砂岩样内部裂隙发展受到抑制,从而表现出随围压增加动应变变化趋势相反的现象。

By carrying out dynamic triaxial cyclic loading tests on strong and moderately weathered argillaceous siltstones,the development law of irrecoverable cumulative plastic dynamic strain under low-frequency cyclic loading was studied.Starting from the four aspects of dynamic stress,static deviator stress,confining pressure and frequency,the axial dynamic strain law of weathered argillaceous siltstone was analyzed and the influence degree of different factors was compared.Nonlinear fitting of experimental data was performed to establish a cumulative strain prediction model for strong and moderately weathered argillaceous siltstone under vibration loading.The results show that the dynamic strain of strongly and moderately weathered argillaceous siltstone under cyclic vibration load is mainly affected by dynamic stress and static deviator stress,and increases with the increase of them.However,it takes about 2000 cycles for moderately weathered argillaceous siltstone to reach stability,while that of strongly weathered argillaceous siltstone only needs about 1000 cycles.When the static deviator stress increases from 0 kPa to 200 kPa,the dynamic strain of moderately weathered argillaceous siltstone increases about 5.97 times,while that of the strongly weathered argillaceous siltstone increases about 8.53 times,which is more obvious.The increase of confining pressure accelerates the development of internal fracture of the strongly weathered argillaceous siltstone,while the development of internal fracture of the moderately weathered argillaceous siltstone is restrained,which shows the opposite trend of dynamic strain with the increase of confining pressure.