真空预压地基卸荷变形特性试验研究

为认识真空预压地基在真空压力卸载中的变形特性,对原状软黏土土样进行了常规三轴仪等向压缩与膨胀试验以及CKC三轴仪压缩膨胀试验,以模拟真空预压地基中各种应力状态下的土体单元在卸除真空压力这种球形压力后的变形特征。研究结果表明,真空压力卸载过程中地基土体既产生弹性的体积膨胀,因偏应力的存在,土体还产生剪切变形,在真空联合堆载预压中,堆载产生的较大偏应力将导致真空压力卸载时地基回弹很小,甚至地基继续沉降。真空压力卸载时,地基的沉降效果是土体膨胀变形和土体的剪切变形的叠加。

Experimental study on deformation of soil under vacuum unloading

In order to study the deformation characteristics of soil under vacuum preloading when unloading vacuum pressure, compression-redound tests on undisturbed soft clay samples are performed to simulate different vacuum unloading case by normal using the triaxial apparatus and CKC triaxial apparatus. The test results indicate that the deformation caused by vacuum unloading includes elastic volumetric swelling and considerable shear deformation under high deviatoric stress level, and the vacuum unloading can induce the shear failure of ground when the deviatoric stress is high enough, especially in vacuum-surcharge preloading. So, both the volumetric swelling and the shear deformation should be considered in settlement analyzsis of vacuum preloading ground.