Research On The Deformation Characteristics And Stability Of Plate Supporting Structure

Plate type supporting structure has become the most common supporting structure in foundation pit supporting engineering because of its characteristics of clear force and convenient construction.There have been a lot of studies on its design calculation and stability analysis.At present,in the design calculation of slab support structure,lateral earth pressure is often assumed to be in the limit equilibrium state and analyzed by using Rankine theory.However,in practical engineering,soil often fails to reach the limit equilibrium state,resulting in the lateral earth pressure of the support structure failing to reach the critical value.Therefore,it is of great practical significance to consider the nonlinear variation of lateral earth pressure in the design calculation of slab support structure.In the stability analysis of slab support structure,the elastic theory only studies the stress and deformation of undamaged soil,unable to consider the ultimate failure conditions of the supporting structure and soil,so it is very necessary to introduce the plastic theory to the stability analysis of slab support structure.In addition,in order to meet the requirements of strength and stability of slab support structure,it is also of important engineering value to strengthen and optimize it.Therefore,on the basis of existing research,this paper takes analytical derivation,laboratory test and numerical calculation as analysis methods to carry out in-depth discussion from three aspects of deformation characteristics,stability and reinforcement methods of slab support structure.The main research work and results are as follows:(1)Accorded to elastic theory and basic assumption,the calculation model of stress and displacement distribution of slab support structure is established.Combined with boundary conditions and compatible equations,the analytical formula of stress and displacement components of the supporting structure under the limit displacement condition is derived by using the semi-inverse solution method,and the calculation formula of earth pressure under the finite displacement condition is introduced,considering the nonlinear relationship between earth pressure and lateral displacement of the supporting structure,the analytical formula of stress and displacement of the supporting structure under the soil pressure-Rb displacement mode is modified and improved.By using ADINA finite element numerical calculation,the correctness of elastic theoretical solutions of displacement and stress of slab supporting structure is verified.It is proved that the method can be used as a tool for conventional design of supporting structure and has important practical value.(2)Accorded to the Winkler foundation beam theory and basic assumptions,the supporting structure is regarded as a vertical elastic foundation beam,and the earth pressure is simplified to the earth pressure spring.Considering the interaction between the stiffness of the supporting structure and the soil support,the calculation model of displacement and internal force distribution of the plate type supporting structure is established.Combined with the flexural differential equation and boundary conditions of the supporting structure,the p-y curve method is introduced to consider the nonlinear change of earth pressure,and the analytical calculation formula of displacement and internal force of the supporting structure is solved based on the finite difference method.The correctness of Winkler analytical solution of displacement and internal force of the slab supporting structure is verified by ADINA finite element numerical calculation.The results can be used to perfect the design theory of supporting structure.(3)Accorded to upper limit theorem of plastic theory,the analytical calculation formula of critical height of supporting structure is deduced.The correctness of analytical solution of critical height of supporting structure is verified by referring to existing research results,which proves that this method can be used as a preliminary method for stability analysis of rigid supporting structure.The soil sliding phenomenon is simulated by laboratory model test and numerical method,and the formation law of the natural Angle of repose and the soil sliding fracture surface is verified.(4)Based on the calculation method of Yang Guangqing,the preliminary design of reinforcement optimization of slab supporting structure is completed.Combined with PLAXIS finite element calculation method,the additional stress acting on the supporting panel is recalculated to complete the reinforcement optimization design of supporting structure,and the final optimization scheme of reinforcement strip size and layout is given.The bearing capacity and stability of the reinforcement scheme are verified by the indoor sand box model test.The results have important value for the development of reinforcement optimization theory of supporting structure.