卸载回弹特性及计算方法研究

Study on Characteristics and Calculation Method of Unloading Rebound

为了研究开挖回弹计算方法,以某地区浅层原状粉质粘土为研究对象,采用GDS静三轴试验系统对其进行不同预压荷载及不同卸荷比的试验研究。通过试验结果分析,得到了回弹变形特性:卸荷量较小时,几乎无回弹变形发生,回弹路径为一条水平线;各卸荷比情况下的回弹曲线基本为一组平行线。仅当卸荷量达到一定水平时,才产生较大的回弹变形。并在此基础上得到了当全部卸载后的最大回弹量取决于初始应力水平,推导了基坑开挖基底回弹变形的估算公式,为实际工程提供了参考。

In order to analyze the calculation method on the excavation rebound,taking the shallow silty clay in one area as the research object,the tests of different preloading load and different unloading ratio are carried out by using geotechnical digital system（GDS） tri-axial instrument.Through the analysis of test results,the characteristics of springback deformation is obtained as follows： When the unloading is small,there has almost no springback deformation and the rebound path is a horizontal line;The rebound curve in every unloading situation is a set of parallel lines.Only when the unloading reaches a certain level,the larger deformation can be produced.On the basis of this,it is obteined that the maximum springback after all unloading depends on the initial stress level,and the estimation formula of springback deformation is derived,thus making the reference to practical engineerings.