Study On Fluid-solid Coupling Effect Of Dewatering And Recharging Effect Of Deep Foundation Pit Supported By SMW Method

The anchor cables+SMW is a new form of support type for deep excavations in soft soil area and has wide application prospects.Dewatering is a common engineering measure in high-water pits,and dewatering will cause the groundwater level outside the foundation pit to drop and must lead to uneven settlement of the surrounding surface,which is harmful to the stability and safety of surrounding buildings;and groundwater recharging is often used in projects to eliminate the above-mentioned adverse effects of pit by dewatering.In order to deeply study the influence mechanism of dewatering and recharging on the deformation of the pit,and the working characteristics of the support form,a deep foundation pit engineering in Jinan is taken as an example.Based on the multi-physics fluid-solid coupling theory,used multi-physics coupling software,which named COMSOL Multiphysics,established a two-dimensional fluid-solid coupling model to study the seepage field of the pit and the deformation of the surface outside the pit,under the non-curtain methold and the suspended curtain methold,since dewatering and recharging.Explored the effects of the factors,such as anchor cable,precipitation and recharge,on the bottom apophysis at the bottom of the foundation pit,the settlement of the ground surface outside the foundation pit and the horizontal displacement of the SMW.Research shows:(1)When there is no precipitation and no recharge,with the deeper of the excavation,the larger of the deformation,the smaller of the settlement due to excavation;when have prestressed anchor cables,the deformation of the foundation pit,inside the affected area by the anchor cables,is reduced by about 0.5 times;(2)When there is precipitation but no recharge,the seepage velocity and hydraulic gradient at the corner of the foundation pit are maximum under the condition of without curtain;under the suspended water curtain,the seepage velocity and hydraulic gradient at the bottom of the curtain are the largest;under different embedding depths,the pore water pressure in the soil under the same depth outside the foundation pit is the largest at the embedded depth of 4/5H(the pit depth),and the smallest when without curtain;(3)When precipitation and recharge,the influence of the recharge on the settlement of the external surface of the foundation pit decreased with the deeper of embedding;the seepage stability of the foundation pit increases with the deeper of embedding,and when the depth of the embedding is 4/5H is most reasonable;the recharge well outside the foundation pit can significantly reduce the settlement,but has little effect on the amount of uplift in the pit and the horizontal displacement of the SMW method pile;recharge well best placed away from the foundation pit 20 meters to 30 meters,when more than 30 meters,the recirculation effection weaker with the increasing distance;the simulation results of fluid-solid coupling is more match the result of the monitoring,fully demonstrating the scientific nature of flow-solid coupling analysis.The research results are of significance for the further understanding of the mechanism of the SMW method and its application of the deep excavations in soft soil areas.