Incremental Analytic Method Of Prestressed Anchor Composite Soil Nailing Wall Retaining System In Coordination

Soil nailing wall retaining system is a novel retaining-soil system for soil excavation and slope stability firstly developed overseas, it has been broadly used since introduced in domestic in the 80 s. It is applied broadly not only where the soil quality is good, but coastal areas where soil quality is soft. With the increasing of buildings all around and height of the buildings, the deepen of underground excavation, pure soil nailing wall retaining system could not satisfy the requirement of modern foundation engineering, then composite soil nailing wall retaining system arises in time. For the foundation with deep height or the relatively strict requirements of lateral displacement, pre-stressed anchor composite soil nailing wall retaining system can be used. This kind of retaining wall retaining system can meet the requirements properly, and it has been used broadly also for its economy and time-saving. However, with the working mechanism complicated, soil nailing force mechanism and the failure mode of foundation unclear, the engineering always design by empirical and checking, the phenomenon of theory analysis laying behind the engineering application exists.In this paper, the major study contents include:(1) With the three-dimensional explicit finite-difference program FLAC3 D, build the models of soil nailing wall retaining system and pre-stressed anchor composite soil nailing wall retaining system respectively, considering the excavation process, and change the parameters of pre-stressed anchor position, pretension value, and so on, summarize the mechanical property and stability of pre-stressed anchor composite soil nailing wall retaining system in the aspect of deformation law of foundation excavation, characteristic of forced soil nailing;(2) On the base of summarizing the force and deformation law of pre-stressed anchor composite soil nailing wall retaining system, supposing the potential slip surface is wedge, with the security coefficient, derive the incremental analytic method of pre-stressed anchor composite soil nailing wall retaining system in considering the excavation process;(3) With the incremental analytic method, analyze the sensitivity of the anchor position, pretension value, and provide the suggestion of the proper design method of pre-stressed anchor composite soil nailing wall retaining system.The major study conclusions of the paper includes:(1)the pretension of the anchor can decrease the soil nailing forces, while the scope is limited, and influence of the upper soil nailing force is bigger than the lower;(2) with the simplified hypothesis, the incremental analytic method of pre-stressed anchor composite soil nailing wall retaining system is introduced, and compared with the results of numerical simulation and the actual project to prove that the method is feasible;(3) The effect of pretension is larger when the anchor is set in the middle or lower of foundation;(4) The optimal value of the pretension exists(the value of the model is 100 k N in this paper), where the pretension value is the most effective, when the pretension value is larger than that, the effect of the pretension decreases.