Study On Nonlinear Energy Consumption Analysis Method Of Slurry Trench Stability Based On Spatial Discretization Technique

The foundation pit is an indispensable part of the structure for the foundation of open-cut underground structures or high-rise buildings.With the acceleration of urbanization in China,infrastructure construction in major cities is in full swing,and foundation pits also appear in various types of projects along with the construction of these infrastructures.As an important form of foundation pit enclosure structure,underground diaphragm wall has been widely used in foundation pit projects because of its strong applicability,good overall performance and high construction efficiency.Although there is a process of mud wall protection to protect the stability of the mud trench during the construction process,if the geological conditions of the ground are poor and the slurry pressure is not enough to resist the soil pressure on both sides of the slurry trench,the soil on both sides of the slurry trench is prone to collapse.Once the slurry trench collapses,the collapse range may extend to the surface,inducing soil settlement on both sides of the slurry trench and posing a serious threat to the safety of the neighboring structures.Therefore,it is of great theoretical significance and practical engineering value to carry out research on the stability of slurry trenches during the construction of ground-linked walls under complex conditions,and to investigate the influence of the coupling of complex factors such as soil non-linear damage criterion,soil non-homogeneous characteristics and pore water pressure on the stability of slurry trenches.Based on the National Natural Science Foundation of China(NSFC)(51878074),this paper combines theoretical analysis and numerical simulation to systematically study the mechanism of instability damage and evaluation methods of slurry trenches under complex conditions.The main research contents are as follows.(1)Based on the mechanical mechanism and damage characteristics of soil destabilization damage,the two-dimensional and three-dimensional damage mechanisms of slurry trenches were constructed using spatial discretization techniques.Based on the MohrCoulomb nonlinear damage criterion and the upper bound analysis,the objective function of the safety coefficient of the slurry trench is derived based on the calculation of the external power and the internal energy dissipation power of the slurry trench,and the optimal upper limit solution of the safety coefficient of the slurry trench is obtained through the optimization calculation,and the influence law of each parameter on the stability of the slurry trench under the consideration of the nonlinear damage characteristics of the soil body is obtained by parametric analysis.The influence law of each parameter on the stability of the slurry trench under the consideration of soil nonlinear damage characteristics was obtained by using parametric analysis.(2)The work done by the pore water pressure is considered as a kind of external power into the energy consumption calculation,and the upper limit solution of the safety coefficient of the slurry trench considering the coupling effect of soil nonlinear damage characteristics and pore water pressure is obtained,and the influence law of pore water pressure and groundwater level change on the stability of the slurry trench considering the action of soil nonlinear damage characteristics is obtained through parametric analysis.(3)By introducing the non-homogeneous characteristics of soil into the upper limit theory of imaginary power calculation,the objective function of safety coefficient of mud trench considering the coupling effect of non-linear damage characteristics and nonhomogeneous characteristics of soil body is obtained,and the safety coefficient of slurry trench in the limit state is calculated by using non-linear optimization method.The influence law of soil non-homogeneous characteristics on the safety coefficient and collapse damage range of mud trench under the action of considering soil non-linear damage characteristics is obtrained through parametric analysis.(4)The three-dimensional damage model of the trench construction of the ground connection wall is constructed by using the finite difference software FLAC3D,and the numerical solution of the safety coefficient of the mud trench in the limit state and the corresponding shape of the collapse and destabilization damage surface of the mud trench are obtained by combining the strength reduction method.The validity of the theoretical calculation is verified by comparing the numerical solution of safety coefficient and collapse surface of slurry trench with the upper limit solution under the same parameters.