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为了研究盐岩在低频循环荷载作用下的蠕变特性,采用恒轴压、循环围压的应力加载方式对盐岩开展了低频循环荷载蠕变试验。试验结果显示,当蠕变时间较短时,盐岩轴向蠕变曲线近似为平滑曲线,波动性不大;当时间增加到一定程度以后,盐岩变形随围压变化而发生明显的波动。总体来看,循环荷载下盐岩轴向蠕变曲线与Burgers模型蠕变曲线较为相似。将Burgers模型分解为Maxwell模型和Kelvin模型,忽略材料的疲劳效应,分别推导了恒轴压、循环围压应力加载方式下Maxwell模型和Kelvin模型的轴向蠕变方程,分析了荷载循环周期对模型蠕变性的影响规律;将循环荷载下Maxwell模型和Kelvin模型的轴向蠕变方程进行叠加,得到了循环荷载下Burgers模型的轴向蠕变方程,并利用盐岩蠕变试验结果对其合理性进行了验证。结果表明:拟合曲线和试验曲线吻合良好,该模型能够较好地反映盐岩在循环荷载作用下的蠕变特性和荷载变化对盐岩蠕变性的重要影响,特别是能够反映出不同荷载循环周期下盐岩变形随荷载变化而发生的明显的波动现象。
In order to study the creep characteristics of salt rock under low-frequency cyclic loading, low-frequency cyclic creep creep tests were carried out on rock salt using stress loading of constant axial pressure and cyclic confining pressure. The experimental results show that when the creep time is short, the rock salt rock salt creep curve approximates to a smooth curve with little fluctuation. When the time increases to a certain extent, the rock salt deformation fluctuates obviously with the confining pressure. In general, the creep curves of salt rock under cyclic loading are similar to those of Burgers model. The Burgers model is decomposed into the Maxwell model and the Kelvin model. Ignoring the fatigue effect of materials, the axial creep equations of Maxwell model and Kelvin model under constant axial compression and cyclic confining stress loading are deduced respectively. The effects of load cycle on the model Creep. The axial creep equation of Burgers model under cyclic loading is obtained by superposing the axial creep equations of Maxwell model and Kelvin model under cyclic loading. The creep test results of salt rock are reasonable Sex has been verified. The results show that the fitted curves are in good agreement with the experimental curves. The model can well reflect the creep characteristics of rock salt under cyclic loading and the important influence of load changes on the creep properties of rock salt, in particular, it can reflect different loads The obvious fluctuation of salt rock deformation with load changes in the cycle.