单轴循环荷载作用下砂岩变形特性与能量特征

为了研究单轴循环荷载下砂岩的变形与能量特性，利用WDT-1500多功能材料试验机，对砂岩进行不同应力振幅条件下循环加载试验，研究了循环加载过程变形3阶段的变形特性、循环软化与循环硬化及能耗特征，并且建立了耗散能随循环次数变化的演化方程。研究结果表明：① 循环荷载上限高于或者低于砂岩屈服应力时，在循环加载过程中的初始阶段和等速阶段砂岩的环向和轴向变形表现出不同的变形特性；② 单轴压缩条件下的屈服应力是砂岩在循环加载过程中循环硬化和软化特性出现变化的分界点；③ 在循环加载过程中的不同阶段能量耗散特征及其演化规律是不同的，其演化曲线呈现U形或者L形；④ 提出基于Lazan材料阻尼理论的耗散能演化方程，试验数据与计算结果对比显示该方程能够较好地反映砂岩循环加载过程中的能量耗散特征。

Deformation and energy characteristics of sandstone subjected to uniaxial cyclic loading

In order to investigate the deformation，cyclic softening and hardening and energy properties of sandstone，the tests of sandstone samples under different amplitudes cyclic loading were conducted on WDT-1500 reactive material testing machine.A dissipated energy evolution equation with cycle number was founded.In the tests，the following conclusion could be drawn.The lateral and axial deformation characteristics of sandstone are different at the initial and constant speed stages，when the upper cyclic loading is above or below yield stress.The yield stress of sandstone under uniaxial compression could be the peak stress corresponding to the point transferring from cyclic softening to cyclic hardening.The characteristics of dissipated energy are different in the whole process，and the shape of evolution can be U shape or L shape.A dissipated energy evolution equation is proposed for sandstone，and the predicted energy dissipation behavior is consistent with the observations in the tests，which shows that the evolution equation is capable of describing the energy dissipation behavior of sandstone.