应力和应变控制下饱和砂土循环扭剪试验分析

Analysis of Cyclic Torsion Shear Experiment of Saturated Sand in Stress and Strain Control

针对某些动荷加载为应变控制的工程问题,如大型工业振动机械的工作平台基础,为研究其动力学性质,利用空心圆柱扭剪仪,分别采用应力和应变控制两种加荷方式,对处于复杂初始应力状态,即不同中主应力系数下的饱和福建标准砂进行小应变循环扭剪试验研究。结果表明,不同加荷方式对土的骨干曲线和剪切模量没有影响;同剪应变幅值时,应变控制下土的阻尼比较应力控制略大;两种控制方式下,试样振动过程中的轴向变形均随着中主应力系数的增大而减小。可见,加荷方式对土的动力特性影响甚微,针对动应变控制的工程问题,在设备有限时可采用应力控制试验模拟代替。

In order to study the dynamic properties of some engineering problems,such as the platform foundation of the large-scale industrial vibration machine. The saturated sand in the complex initial stress state was tested by the hollow shear apparatus through the two modes of stress control and strain control,in which the medium principal stress coefficient varied. The results show that different loading modes have no effect on the shear modulus of soil,and both the damping ratio and pore pressure increment of soil under strain control are greater than that of stress control,in addition,under the both two control modes,the axial deformation of specimen decreases with the increase of the main stress coefficient in the test process. It is concluded that there is no significant difference between the two control modes on the dynamic characteristics of soil,and stress control test can be applied to the dynamic engineering problems of strain control when the equipment is limited.