南宁地区红黏土循环动力特性试验研究
肖桂元1，2，刘晓楠1*
1.桂林理工大学土木工程学院，广西 桂林541000；
2.桂林理工大学广西岩土力学与工程重点实验室，广西 桂林 541000
摘要：为研究南宁红黏土在循环荷载下的动力特性，制备动三轴圆柱体试件（以下简称试件）进行系列动三轴试验，探究不同固结围压、循环应力比、加载频率对南宁红黏土动强度衰减和动变形演化特性的影响，分析动弹性模量和阻尼比变化规律。试验结果表明：1)不同加载条件（固结围压、加载频率、循环应力比）下试件的动应力均随循环次数的增大先快速减小后趋于稳定；循环次数相同，动应力随固结围压的增大而增大，随加载频率、循环应力比增大而减小；固结围压、加载频率、循环应力比对试件的动应力有显著影响。2）在固结围压为300 kPa和加载频率为1.0 Hz条件下，试件的抗压强度最大；且在加载循环一定次数后，抗压强度对受力条件的敏感性降低。3）固结围压、循环应力比、加载频率对试件的动弹性模量均有影响，表现为随动应变累积，动弹性模量减小且减小速率变缓；相同动应变下，动弹性模量随固结围压、加载频率的增大而增大，随循环应力比的增大而减小；不同固结围压、加载频率和循环应力比条件下，动弹性模量的倒数与动应变近似线性相关。4）动应变增量相同时，阻尼比变化量随固结围压的增大而减小；随循环应力比的增大先基本不变后减小；随加载频率的增大而减小；阻尼比在一定范围内波动，随动应变的增大而增大。
关键词：红黏土；动三轴试验；动弹性模量；阻尼比；动应变
Experimental study on the cyclic dynamic characteristics of red clay in Nanning area
XIAO Guiyuan1,2, LIU Xiaonan1*
1.School of Civil Engineering, Guilin University of Technology, Guilin 541000, China;
2.Guangxi Key Laboratory of Geotechnics, Guilin University of Technology, Guilin 541000, China
Abstract: To study the cyclic dynamic characteristics of red clay in Nanning area, dynamic triaxial cylindrical specimens (hereinafter referred to as specimens) are prepared for a series of dynamic triaxial tests. The effects of different consolidation confining pressures, cyclic stress ratios, and loading frequencies on the dynamic strength degradation and dynamic deformation evolution characteristics of Nanning red clay are investigated, along with an analysis of the variation patterns of dynamic elastic modulus and damping ratio. The test results indicate that:1)Under different loading conditions (consolidation confining pressure, loading frequency, cyclic stress ratio), the dynamic stress of the specimens decreases rapidly and then tends to stabilize with the increase of the number of cycles. For the same number of cycles, dynamic stress increases with the increase of consolidation confining pressure, while it decreases with the increase of loading frequency and cyclic stress ratio, indicating that consolidation confining pressure, loading frequency, and cyclic stress ratio have a significant impact on the dynamic stress of the specimens. 2)Under a consolidation confining pressure of 300 kPa and a loading frequency of 1.0 Hz, the compressive strength of the specimens reaches its maximum; furthermore, after a certain number of loading cycles, the sensitivity of compressive strength to loading conditions decreases. 3)Consolidation confining pressure, cyclic stress ratio, and loading frequency all influence the dynamic elastic modulus of the specimens, which is characterized by a decrease in dynamic elastic modulus and a slowing rate of decrease with the accumulation of dynamic strain; for the same dynamic strain, the dynamic elastic modulus increases with the increase of consolidation confining pressure and loading frequency, while it decreases with the increase of cyclic stress ratio; under different conditions of consolidation confining pressure, loading frequency, and cyclic stress ratio, the inverse of the dynamic elastic modulus is approximately linearly correlated with dynamic strain. 4)When the increment of dynamic strain is the same, the change in damping ratio decreases with the increase of consolidation confining pressure; it remains relatively constant and then decreases with the increase of cyclic stress ratio; and it decreases with the increase of loading frequency; the damping ratio fluctuates within a certain range and increases with the increase of dynamic strain.
Keywords: red clay; dynamic triaxial test; dynamic modulus of elasticity; damping ratio; dynamic strain
