分级循环荷载下岩石动力学行为试验研究

利用WDT-1500多功能材料试验机，对砂岩、砾岩和砂砾岩进行了分级循环荷载试验，研究了岩石的动弹性模量对应力幅值和应力水平的响应特性，得到了动弹性模量和耗散能随应力幅值、应力水平及含水率的变化规律。试验结果表明，分级循环荷载下岩石的能量耗散越多，动弹性模量越小；应力水平越高，动弹性模量和耗散能越大；含水率和应力幅值越大，动弹性模量越小，耗散能越大。讨论了邓肯-张模型能够描述分级循环荷载作用下岩石的应力-应变关系，构建了动弹性模量随应力水平、应力幅值及含水率变化的演化模型，探讨了模型参数的确定方法。根据能量耗散的经验法则，建立了耗散能演化模型，结果表明，该模型能够描述分级循环荷载过程中能量耗散行为。

An experimental study of dynamic behaviors of rock under stepwise cyclic loading

The aim of this study is to investigate the responses of dynamic elastic modulus of rock on stress amplitude and stress level. Stepwise cyclic loading tests are conducted on sandstone, conglomerate and sandy conglomerate using a WDT-1500 reactive material testing machine. The variations of dynamic elastic modulus and dissipated energy with stress amplitude, stress level and moisture content are determined. The results show that the dynamic elastic modulus gradually decreases with the increase of energy dissipated. It is observed that the higher the stress level, the greater the dynamic elastic modulus and dissipated energy; the greater the moisture content and stress amplitude, the lower the dynamic elastic modulus, but the greater the dissipated energy. Ducan-Chang model is capable of describing the stress-strain relationship of rock under stepwise cyclic loading. Thus, a dynamic elastic modulus evolution model is proposed by taking into account the stress amplitude, stress level and moisture, and the methods to determine parameters of the model are discussed. Then, based on an empirical rule of energy dissipation, a dissipated energy evolution model is developed. The results show that the proposed models are able to describe correctly the characteristic of energy dissipation of rocks under stepwise cyclic loading.