超载卸荷后再压缩软土的次压缩特征及变形计算

Secondary compression characteristics and settlement calculation of soft clay under overloading-unloading and reloading

采用软土重塑试样进行了超载卸荷后再压缩过程的一维压缩试验。试验表明:超载卸荷后软土的再压缩过程较原压缩过程的主固结时间大大缩短,次固结系数在较长的时间内和时间无关,随再加荷压力的增大而增大,随着预固结压力的增大而减小,次固结系数和超载比之间具有规则的对应关系,可以用双曲线简化模型模拟;根据次固结系数双曲线模型建立的次压缩变形计算公式,既反应了软土本身性质的影响,也反应了预固结压力和再加荷压力的影响。工程算例数据和工程实测的工后沉降数据表明,使用改进的次压缩变形计算公式得到的结果,较之采用传统次压缩变形计算方法具有更高的可靠性,采用传统的次压缩变形公式计算再压缩软土的次压缩变形会产生较大的正偏差。

A series of 1-D consolidation tests are carried out for soft remolded clay under overloading-unloading and reloading. It is found that the primary consolidation time is greatly reduced than that of the original compression. The secondary consolidation coefficient is not related to time of sustained loads, and it becomes larger as the reloading pressure increases and becomes less with the pre-consolidation pressure. The regular relationship between the secondary consolidation coefficient and OPR （over pressure ratio） can be simulated by the simplified hyperbolic model. Based on the model, the secondary compression settlement formula is established, which reflects the influence of soft clay characteristics, pre-consolidation pressure and reloading pressure. Comparison between calculated values of the engineering example and post-construction measured data shows that the results by the secondary compression settlement formula are reliable. The present method is more reasonable than the traditional methods, while the results by the traditional methods are much larger than the true results.