| The application of deep foundation pit retaining structure with pouring piles has been widely used,and the design concept—deep foundation envelope structure based on displacement control is very popular.One major step for designing deep foundation envelope structure is to use an appropriate method to calculate the displacement of deep foundation envelope structure.Correctly selecting deformed soil pressure model and soil rock mechanics parameter of soil mass is the key to calculate the horizontal displacement of deep foundation.To calculate the horizontal displacement of deep foundation more accurately,this paper takes the following measures:(1)Based on the improved soil pressure model,introducing p-y curve model for laterally loaded pile,the formula for calculating the horizontal reaction coefficient k_s is derived,and the nonlinear relationship between the excavation depth and the horizontal reaction coefficient is obtained.Combined with the deflection curve equation of concurrent deformation of soil mass and soldier piles,a difference equation is established.Solving the calculation formula of horizontal displacement of retaining piles in deep foundation pit based on p-y curve of horizontally loaded pile.Besides,Matlab programming is made to calculate the horizontal displacement of soldier piles.Combined with the foundation pit engineering of Lanzhou Metro Station,the horizontal displacement calculation of the retaining pile is carried out.The programmed displacement is compared with the actual monitoring displacement,and the conclusion that the calculation result deviates from the actual displacement is obtained,and the reason is analyzed.(2)According to the on-site horizontal displacement monitoring data of the deep foundation pit of Lanzhou Metro Station,the sensitivity analysis of the parameters that may affect the horizontal displacement of the deep foundation pit retaining pile is obtained,and the horizontal reaction coefficient m value and the friction angle φ are obtained as high sensitivity parameters.The elastic modulus E and the cohesion force c are the conclusions of the medium sensitivity parameter;thus,the calculation method of the horizontal reaction coefficient k_s of the soil and the calculation method of the numerical value of the horizontal reaction coefficient proportional coefficient m are analyzed.The author believes that the parameter inversion based on artificial neural network can obtain the physical parameters of the soil that are more realistic,so as to carry out the calculation design and structural analysis of the deep foundation pit.(3)Using the Matlab genetic algorithm toolbox,the actual monitoring displacement is taken as the input data,and the BP neural network is used to invert the soil layer parameters obtained from the actual monitoring displacement inversion.The parameters obtained from the inversion are fed back to the horizontally based load.In the calculation program of the horizontal displacement of the deep foundation pit retaining pile with pile p-y curve,the horizontal calculated displacement of the deep foundation pit retaining pile is obtained,and the actual monitoring displacement is compared with the actual monitoring displacement to draw conclusions:1)Soil through actual monitoring data,The inversion of the main mechanical parameters of the layer can be applied to the selection of soil mechanics parameters in the indeterminate stratum;2)the mechanical parameters obtained by the inversion can better predict the displacement of the next working condition of the foundation pit excavation;3)The inversion of mechanical parameters can better guide the engineering practice in the region;4)The horizontal displacement calculation method of the deep foundation pit retaining pile based on the horizontally loaded pile p-y curve can better reflect the mutual interaction between the retaining pile and the soil function,the calculation results are more in line with the actual deformation. |
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