真空堆载联合预压作用下软土地基位移和孔压变化规律研究

Study on laws of the displacement and the pore water pressure variation in strengthening soft ground by using vacuum-surcharge preloading

根据实测资料分析了真空堆载联合预压作用下加固区地表沉降、土体侧向位移、孔压、超孔压变化规律,并对孔压消散原因进行微观解释,结果表明:真空预压形成的负压与堆载预压形成的正压二者在加固软土地基的效果上是一致的,场地中心处的沉降要比四周大,用固结度对数配合法推定最终沉降,停泵时的平均固结度达到97%;真空预压阶段土体侧向位移方向是指向加固区内的,而堆载预压阶段是指向加固区外的;开始抽真空后浅层土体孔压消散非常明显,深层土体孔压消散较为缓慢,后期较深土层中孔压才有较大变化;超孔压在抽真空后变为负值,在真空预压阶段绝对值越来越大。

Based on the observation data from vacuum-surcharge preloading,the variation laws with time such as the ground settlement,the lateral displacement,pore water pressure and excess pore water pres-sure are analyzed,and the microcosmic reasons for the dissipation of soil pore pressure are explained.The results indicate that the effects of the negative pressure produced by vacuum preloading and the positive pressure produced by surcharge preloading are the consistent for the reinforcement of soft ground.The set-tlement in the site center is greater than that in the surrounding area,and the final settlement shows that the average degree of consolidation reaches 97%.The direction of the lateral displacement in the process of vacuum preloading turns to the inside of the strengthened area,while in the process of surcharge pre-loading it turns to the outside of the strengthened area.The dissipation of pore water pressure in shallow soil is obvious while in deep soil is very slow in the beginning stage,and the pore water pressure in deep soil changes greatly in the later stage.The excess pore water pressure turns to negative after the vacuum preloading begins,and the negative value is increasing as the vacuum preloading continues.