Numerical Simulation Comparison With Engineering Project Of The Prestressed Anchor Cable Composite Soil Nailing

Soil nailing,as one of the supporting technique for deep foundation pit,is economic, reliable and convenient, thus it has been widely applied in engineering practice. However, it can't separately used in those projects, which with unsatisfied soil condition, higher underground water level and strictly deformation controling, such as sullage soft soil. So, based on the soil nailing, the composite soil nailing , for instance soil nail-cement mixing pile, prestressed cable and leading mini-pile, have been developed rapidly and used widely in different domains of civil engineering in recent years. They can combine with each other flexibly according to the different geological and local conditions. But because of analysis in working behavior and mechanism is not in deep enough, usually result in the following two phenomena: on the one hand, designers always try to improve the safety factor of foundation pit in order to stability and security, which often lead to material waste; on the other hand, engineering accidents are occurred frequently owing to instability of foundation pit and oversize deformation.In this paper, in view of the requirement of composite soil nailing research and engineering application, the FEM software MIDAS/GTS was used to simulate the behavior of commonly used composite soil nailing, and research deeply and utterly, the numerical simulation result was compare with a engineering project, some useful conclusions for design have been generalized, as follows:(1)MIDAS/GTS was adopted to simulate the"inverse construction method"construction course of composite soil nailing, the investigation shows that horizontal displacement curve was showing "drum belly" in various construction stages whether soil nailing or prestressed composite soil nailing, the maximum horizontal displacement was in the low part of pit rather than in the top part.(2)The axial force distribution of prestressed cables is curve-shaped approximately, and become larger With the increase of the depth of excavation,the maximum ones along the anchorage section is in the free section which connecting with prestressed cables, the maximum ones is in distal end.(3)The slope horizontal displacement and ground settlement of deep foundation pit increased significantly because of overloading, therefore, particular attention should be paid to the ground overload when in designing foundation pit.(4)Generalize conclusions from comparation numerical simulation results and measured data are that implanted trusses unit can be used to imitate prestressed cable, but the prestress value should reduce appropriately allow for prestress loss and structural units defects;distance of both sides around slope toe should be special note when in determining calculation range in case of it too small.