空心圆柱仪(HCA)模拟恒定围压下主应力轴循环旋转应力路径能力分析

Analysis on ability of HCA to imitate cyclic principal stress rotation under constant confining pressure

针对国际上大多数HCA仪在主应力轴循环旋转试验中只能提供轴力和扭矩两个加载变量的现状,指出了这种变载方式在模拟主应力轴循环旋转应力路径方面存在的局限性。通过详细的数学推导提出了三种切实可行,且能模拟实际工程中土体经历主应力轴循环旋转的应力加载方式:①在满足轴力W等于3πrori(pi-po)的前提下,仅变化扭矩MT可实现围压p不变,中主应力参数b恒定(0.5),而剪应力q随大主应力轴转角α有规律循环变化的应力路径;②在保持b不变的前提下(此时b可以设定为不等于0.5的任意合理值),只要W和MT能满足一定的三角函数关系式,同时以p—q形式的临界状态线为准绳,通过控制轴力的加载范围限制试验中允许出现的q的峰值,就可以实现p、q之间保持恒定线性关系而α有规律循环变化的应力路径;③若不考虑中主应力对于土体性状影响,则可通过对W和MT采用较为简单的三角函数关系来实现保持q不变,而(σ1+σ3)/2随α单调递减的应力变化方式。研究成果不仅给后继的试验方案提供了理论基础,也为HCA仪器功能的完善提供了很好的依据。

Nowadays most hollow cylinder apparatus （HCA） in the world could only apply two dynamical loads, namely, axial load and torque during cyclic principal stress rotation. The limitation of this loading mode was presented through rigorous deduction, and based on such limitation the possible and applicable loading modes were put forward： ①by setting the axial load W equal to 3πrori（Pi-Po）, the stress path of shear stress q regularly varied with rotation angle a under constant b （the effect of intermediate stress） and the mean principal stress p could be achieved by changing torque MT;② setting a constant b （not equal to 0.5 ） the linear relationship between p and q could be realized under regular change of α. In this case W and MT should satisfy a certain equation and meanwhile the peak value of q should be restricted within p - q critical state line; ③without the effect of intermediate principal stress the monotonous variation of stress path of （σ1＋σ3）/2 with α could be achieved under constant q. Then W and MT must satisfy some simple trigonometric functions.