不同围压和振幅下岩石循环荷载动力特征分析

Dynamic Characteristics Analysis of Rock in Different Compress and Amplitude under Cyclic Loading

循环荷载试验是为了得到中风化砂岩试样在循环荷载下的动力学特征,对周期荷载下工程稳定性评估方面有着参考和指导作用。通过MTS(力学测试系统)岩石试验机进行频率为1 Hz的不同应力幅值和围压的循环加、卸荷载试验的方法,研究了中等风化砂岩在不同围压下的滞回环形态、动弹性模量、轴向应变和阻尼比的变化规律。结果表明:在循环荷载的过程中,随着应力幅值的不断增大,其滞回环的面积不断增加,消耗能量和损伤加大;围压增加,阻尼比降低,滞回环形态发生改变,试样的轴向应变减弱,表明围压抑制试样的变形破坏发展;随着应力幅值增加,试样循环加卸载次数～应变曲线呈初始、稳定和加速3个阶段,加速阶段的曲线的明显陡升表明试样内部损伤加剧;其动弹性模量先减少后增加并趋于稳定,总体呈阶梯状下降,且随着围压的增加而增加,表明循环荷载在一定程度上使试样强度增加,此现象与阻尼比趋势一致。

The cyclic loading experiment is to obtain the dynamic characteristics of middle-weathering sandstone in cyclic loading, with the functions of direction and reference for engineering stability evaluation under period loading. The method of 1 Hz rock cyclic loading experiment in different compress and amplitude by using MTS(mechanics test system) rock test machine to study the changing laws of strain, dynamic elastic modulus, damping ratio and form of hysteretic cycle.The result show that in the proceeding of cyclic loading ,what area of hysteretic cycle increasing with amplitude mean consumption of energy and damage is augmenting. The adding compress can restrain strain of samples because there are phenomena of decreased axial strain and damping ratio. As the stress amplitude increases, the area of the hysteresis loop increases, and the energy consumption and damage increase. The obvious steep rise of the curve in the acceleration phase indicates that the internal damage of the sample is intensified;Its dynamic elastic modulus first decreases, then increases and tends to be stable, and generally falls in a stepped shape. Moreover, it increases with the increase of confining pressure, indicating that the cyclic load increases the specimen strength to a certain extent, which is consistent with the trend of damping ratio.