循环荷载作用下岩盐动力特性及累积变形研究

Study on Dynamic Characteristics and Accumulated Deformation of Rock Salt under Cyclic Loading

针对岩盐动力特性及累积变形规律研究匮乏的情况,分析了不同试验条件对岩盐动力特性和累积变形发展规律的影响。通过室内动三轴试验,研究了动应力幅值、围压、含水率和加载频率等影响因素作用下岩盐的动强度、动剪切模量和累积应变发展规律。基于Monismith等提出的指数模型,建立了能够合理预测岩盐累积变形的计算模型,并确定了相关参数;在考虑模型建立的背景与条件基础上,分析模型的适用条件。研究结果表明:(1)岩盐强度指标对不同因素的作用响应存在差异,围压和动应力幅值的大小对察尔汗湖区岩盐动强度影响较明显;动强度随加载次数的增加而减低。(2)岩盐在不同因素的作用下形成不同的结构骨架,因而表现出不同的变化规律;动剪切模量随动应变的增加而减小;随围压和动应力幅值的增大而增大,随含水率和频率的增大而减小。(3)岩盐的特殊性,使其累积应变的变化规律与一般土体产生较明显的区别;累积应变随着加载次数的增加均呈现持续增长并逐步稳定的趋势;随动应力幅值、围压和加载频率的增加而增加;存在一个合理的含水率范围,使得岩盐能够在循环荷载作用下有较小的累积应变。通过本研究,揭示了岩盐累积变形发展规律,对该地区的公路路基设计和施工均具有重要的参考价值。

Amid at the lack of research on the dynamic characteristics and law of cumulative deformation of rock salt,the influence of different test conditions on the dynamic characteristics and cumulative deformation of rock salt were analyzed.Through the dynamic triaxial test,the dynamic strength,dynamic shear modulus and cumulative strain development law of rock salt at different dynamic stress amplitudes,confining pressures,water contents and vibration frequencies were studied.Based on the exponential model proposed by Monismith,a calculation model that can reasonably predict the cumulative strain of rock salt was established,and the relevant model parameters were determined.On the basis of considering the background and conditions of the model establishment,the applicable conditions of the model were analyzed.The research results indicated:(1)There are differences in the response of rock salt strength indicators to different factors.The confining pressure and dynamic stress amplitude had obvious influence on the dynamic strength of rock salt in Qarhan Lake;the dynamic strength decreased with the increase of the number of vibrations.(2) The diverse structural framework of rock salt were formed under the action of different factors.Therefore,it showed a different rule of change.The dynamic shear modulus of rock salt decreased with the increase of dynamic strain;it increased with the increase of confining pressure and dynamic stress amplitude and decreased with the increase of water content and frequency.(3) The particularity of rock salt makes the change rule of cumulative strain different from ordinary soil.The cumulative strain of rock salt showed a continuous growth trend and gradual convergence with the increasing number of vibrations;the cumulative strain of rock salt increased with the increases of confining pressure,dynamic stress amplitude and vibration frequency;there was a reasonable water content range,among which the rock salt can have a smaller cumulative strain under cyclic loading.The research results on the cumulative strain development law have significant reference value for the design and construction of highway subgrade in this area.