真空预压作用下竖井地基孔压消散研究

考虑竖井地基变形和渗流属于三维问题,提出真空预压作用下竖井地基的三维单井有限元计算方法。根据经典比奥固结理论,编制了可以考虑孔压、位移耦合的三维有限元程序。结合提出的三维单井有限元计算方法,应用该程序,分析某高速公路试验段在不同竖井间距、不同竖井打入深度下的孔压消散情况。分析表明:竖井地基的孔压消散规律为竖井间距越小,土体固结越快;竖井打入越深,下卧层孔压消散越快,处理区固结稍慢,但有利于整个土体固结。实际应用中竖井间距可取为1.0～1.5m,竖井应尽量打穿软土层,未穿时,可按5m影响深度考虑下卧层的固结。

Research on dissipation of pore water pressure of foundations stabilized by vertical drains under vacuum preloading

Considering that deformation and seepage flow of foundation stabilized by vertical drains are three dimensional problem,3-D single drain FEM method is put forward for consolidation analysis of the ground with vertical drain wells under vacuum preloading. Based on classical consolidation theory developed by BIOT,3-D finite element program coupling deformation and pore-pressure is coded. Pore water pressure dissipation of a highway test section stabilized by vertical drains together with vacuum preloading is analyzed using the 3-D single drain FEM method. Different vertical drain installation depth and different drain spacing are taken into account in the analysis. The analysis shows that shortening the space of the vertical drains can significantly increase the rate of consolidation. It also shows that the deeper the vertical drains are installed the faster consolidation rate of the section without vertical drain is; however,the consolidation rate of the section with vertical drain will be reduced. From a macro point of view,it is advantageous to the consolidation of the system. In engineering practice,vertical drain wells can be installed at from 1.0m to 1.5m spacing and the soft clay in the compression zone should be penetrated through. If the vertical drain is installed partially,5m influence depth can be evaluated for consolidation analysis of the section without vertical drain.