大面积填土荷载作用下软土地区土体固结变形特性有限元分析

Finite element analysis of consolidation characteristics of soft soil under large filling load

在沉降监测区地面填土调查和沉降监测点历年沉降监测成果对比分析的基础上,结合监测区工程地质条件,借助PLAXIS有限元软件,对宁波软土地区快速发展中填土引发的附加荷载作用下土体固结过程中的沉降变形和孔隙水压力分布及消散特征进行了一系列的模拟分析,对其沉降变形机理进行了探讨。实测及模拟结果表明:填土的广泛分布在宁波市地面沉降中发挥着重要作用;上部淤泥质土体的竖向变形在地面沉降中占绝对大的比重;若土体的均一性较好,则不会产生水平位移,即不易出现地面沉降区域向附加荷载作用范围外扩散的现象;表部附加荷载对上部淤泥质土体的影响显著,而对下部软—可塑的粘性土、砂土及碎石土的影响效果显著降低;填土荷载作用下,宁波市地面沉降变形特性主要由上部淤泥质土体的超静孔隙水压力的缓慢消散引起。

Based on the site investigation at filled land and the comparative analysis of the settlement results in the settlement monitoring area over years,combined with the in-situ engineering geological conditions,a series of simulation analysis was made on the settlement deformation,pore water pressure distribution and dissipation characteristics of soft soil consolidation under the additional load caused by filling in the rapid development area in Ningbo using PLAXIS program. The test and simulation results show that the wide distribution of fills plays an important role in the land subsidence in Ningbo. The vertical deformation of the upper soft soil accounts for an absolute proportion in the ground settlement. If the soil is uniform,there will be no horizontal displacement,that is to say,it is not easy for the land subsidence area to diffuse beyond the scope of additional load. The effect of surface additional load on the upper muddy soil is significant,while the effect on the lower soft to plastic clay,sand and gravel is slight.Under the action of ground filling load,the characteristics of land subsidence deformation in Ningbo is mainly due to the slow dissipation of excess pore water pressure in the upper muddy soil.