Stability Analysis For The Trench Of Ultra-Deep Diaphragm Wall Based On The Distinct Lattice Spring Model

In the rapid development of infrastructure projects,diaphragm wall project has been one of the important foundation projects.The analysis and research on the stability of diaphragm wall during trench excavation is of great significance for the stability evaluation of engineering and the safety construction of diaphragm wall.Based on the construction of ultra-deep diaphragm wall in Hangzhou Metro,this paper made a comprehensive numerical analysis of the factors influencing the stability of diaphragm wall during excavation based on the distinct lattice spring model(DLSM).(1)A fiber-distinct lattice spring model(Fiber-DLSM)was developed,which can simplify the mechanical modeling and analysis of reinforced concrete structure.Its applicability for analyzing steel-concrete structures was verified through tensile and compression numerical experiments.On this basis,a refined steel-concrete coupling diaphragm wall model was constructed and its elastic and plastic mechanical responses were obtained.Based on the anisotropy analysis of the diaphragm wall,the equivalent parameters for numerical model of the diaphragm wall in Hangzhou Metro were obtained.(2)The developed elastic-plastic distinct lattice spring model(DP-DLSM)and the distinct latttice spring model based on the distributed loading gravity overweight method(GIM-DLSM)have advantages in the analysis of large deformation and instability failure of diaphragm wall.Combined with the construction of ultra-deep diaphragm wall in Lot 15 of Hangzhou Metro Line 6,a three-dimensional numerical model for the trench of diaphragm wall was established by these two models.Based on the comprehensive consideration of mud,slot size,surface load,jet-grouting pile reinforcement,especially the slotting plan,three-dimensional numerical simulation of the slotting process was carried out.The construction scheme suitable for the excavation of the ultra-deep diaphragm wall trench was proposed based on the results of deformation and failure of the trench.(3)DLSM was re-developed and formed as the creep-enhanced distinct lattice spring model(DP-NB-DLSM)which can calculate the creep failure of materials.On the basis of verifying the correctness and applicability of the model,a parametric analysis of cohesion,internal friction angle and tensile strength was carried out,which showed that the model is fast and accurate to characterize the complete creep of rock and soil.Subsequently,taking the construction of the ultra-deep diaphragm wall in Section 15 of Hangzhou Metro Line 6 as the background,the stability of the trench under the influence of creep was numerically calculated based on the DP-NB-DLSM,and corresponding construction suggestions were given based on the simulation results.