Geotechnical Parameter Statistics Of Nanchang Subway Line 2 And Analysis Of Foundation Pit Support At Yayuan Road Station

The deep foundation pit of the subway station is an important part of the subway construction project.It is important not only to ensure the deformation of the supporting structure in the standard range,but also to avoid the high cost caused by the design conservatism.By taking the subway station of Nanchang line two as the background,this paper makes a statistical study on the rock and soil of the 9 sites along this line,and analyzes the relationship between the porosity ratio and the compression coefficient,the shear strength index and the physical quantity of water content and pore ratio.To analyze the internal force and deformation of the enclosure structure of Ya Yuan Road subway station,this paper used the software of deep foundation pit and the finite element software GEOSTUDIO.At the same time,the simulated values are compared with the monitoring results.The main work and research results of this paper are as follows:1.Through the statistics of the rock and soil parameters of the silty clay and the medium weathered sand conglomerate on the 9 sites along the line,the maximum value,minimum value,mean value,standard deviation and variation coefficient of the experimental values of rock and soil parameters in the silty clay layer and the medium weathered rock layer are obtained.The following relationship is obtained by statistical analysis.(1)the compression coefficient av increases with the increase of the pore ratio e,and the expression of the compression coefficient.(2)The plastic limit index Ip increases with the increase of liquid limit WL.(3)The cohesion c and the internal friction angle are decreased with the increase of water content and pore ratio,and the change rule may be influenced by the properties of sand content and dry density.(4)the standard penetration test number and the standard value of carrying capacity change linearly.When the test hit number is about 3~9 hitting the /30 cm,the standard value of the bearing capacity rises more evenly.When the test number is around /30 cm,the standard value of the bearing capacity rises faster.(5)the standard penetration test N increases linearly with the deformation modulus E0.(6)The softening coefficient of moderately weathered glutenite is 0.3,and the standard deviation is 0.05,and the average value is less than 0.75,which belongs to the softening rock.2.Through the rectification deep foundation pit software,to calculate the excavation and construction process of foundation pit of yayuan road station,this paper analyzed the law of internal force deformation of support structure under different working conditions.Using the finite element Geostudio software,the horizontal displacement changes of the surrounding structures in various working conditions during excavation are simulated.The simulation results and the calculation results of the foundation pit software are close to the horizontal displacement trend and results of field monitoring;the deformation curves are roughly the same.This means that the calculation is reasonable and the displacement of the diaphragm wall meets the standard requirements.The results provide some reference for the design and construction of the deep foundation pit engineering in Nanchang metro station.