Calculation Of Internal Force And Displacement Of Composite Soil Nailing Wall With Prestressed Anchor Rod

With the development of the city and the increasing tension of land space,the scale and depth of foundation pit engineering are expanding.Prestressed anchor composite soil nailing wall is widely used in foundation pit engineering because of its’ fast construction and low cost.However,in the study of internal force of prestressed anchor composite soil nailing wall,the interaction between prestressing anchor and soil nailing is seldom considered,and the relevant theory of displacement is pointed out.On the other hand,there are relatively few studies.On the basis of previous studies,this paper starts from the stress characteristics of soil nails and anchors,establishes the displacement compatibility equation according to the effect of soil pressure,soil nails and anchors on displacement,and then solves the internal force of soil nails and anchors and the horizontal displacement of foundation pits.The main contents and conclusions are as follows:(1)In order to study the internal forces of soil nails and anchors,the soil pressure acting on the soil nailing wall is defined firstly,and the mechanism and mechanical characteristics of soil nails are studied by analyzing the construction process of the composite soil nailing wall with pre-stressed anchors,so as to give the expressions of the axial force and shear stress of soil nails under various working conditions;secondly,according to the mechanism of pre-stressed anchors,the expressions of the axial force and shear stress of the anchoring section are studied.According to the stress characteristics,the calculation formula of bolt stiffness in the code is improved.(2)Deducing the horizontal displacement of foundation pit caused by earth pressure and constraint on displacement caused soil nail and anchor.The displacement compatibility equation is established by taking advantage of zero relative displacement between nail and soil at potential sliding surface.The axial force of soil nail and anchor and the horizontal displacement of foundation pit under different working conditions are solved.Combining with practical engineering,excavation and support of foundation pits are simulated using finite element analysis software Plaxis2 D.The simulation is carried out with the support,and the results are compared and analyzed with the calculated results under various working conditions to verify its accuracy.(3)Based on the foundation pit supported by a pre-stressed anchor composite soil nailing wall,the effects of soil parameters,soil nailing design parameters and anchor design parameters on the stability and horizontal displacement of foundation pit are analyzed.The results show that the soil parameters have a great influence on the stability and horizontal displacement of foundation pit,reasonable calculation parameters should be selected in the design process of foundation pit support.It has a great influence on the stability of foundation pit,but has no obvious effect on the horizontal displacement.The design parameters of anchor have significant influence on the horizontal displacement.The effect of controlling the horizontal displacement of foundation pit can be achieved by adjusting the design parameters of anchor.