冻结饱和砂土真三轴试验及本构模型研究

True Triaxial Test and Constitutive Model of Frozen Saturated Sand

为研究冻结饱和砂土在不同温度、初始围压、中主应力系数影响下的强度和变形特性,借助冻土真三轴试验机对黑龙江某矿砂土在-5℃、-10℃、-15℃3个温度下进行等小主应力σ等中主应力系数b加载真三轴试验,试验结果表明:在同一围压和温度下,冻结饱和砂土破坏强度随b值增大而增大,当b值达到0.75后,强度随b值增大而降低,近似呈二次函数关系;在同一围压和b值下,冻结饱和砂土破坏强度随温度降低线性增长。冻结饱和砂土在真三轴条件下体应变先剪缩后剪胀,且b值越大或围压越小,剪胀性越强。根据试验结果规律,通过对邓肯-张参数进行回归分析,建立了以温度和中主应力系数为影响因素的改进邓肯-张模型,并验证模型可靠性。研究结果可为富水砂层中冻结法施工提供一定参考。

In order to study the strength and deformation characteristics of frozen saturated sand under the influence of different temperatures,initial confining pressure and intermedium principal stress coefficient,with the help of frozen soil true triaxial test machine,the true triaxial test under the conditions of constant minor principal stressσand intermedium principal stress coefficient b of sand from a certain mine in Heilongjiang was carried out at three temperatures of-5℃,-10℃and-15℃.The test results show that under the same confining pressure and temperature,the failure strength of frozen saturated sand increases with the increase of b value.When b value reaches 0.75,the strength decreases with the increase of b value,which is approximately a quadratic function.Under the same confining pressure and b value,the failure strength of frozen saturated sand increases linearly with the decrease of temperature.Under the true triaxial condition,the volume strain of frozen saturated sand shows the characteristics of shear shrinkage first and then dilatancy,and the greater the value of b or the smaller the confining pressure,the stronger the dilatancy.In view of the failure of Duncan-Chang model to consider the influence of medium principal stress,according to the results of frozen soil true triaxial test and based on the regression analysis of Duncan-Chang parameters,an improved Duncan-Chang model with temperature and the coefficient medium principal stress as influencing factors is established,and the reliability of the model is verified.The research results can provide some reference for freezing construction in watery sandy stratum.