Experimental Research And Application Of Diversion Function Segments

According to the overall plan of Jinan City,the population of the central city of Jinan City will expand to 5 million by 2030,and the scale of land use will expand to 500 square kilometers.The contradiction between urban transportation,environment,and resources is increasingly prominent.The construction of rail transit is a necessary means to alleviate the above contradictions.The construction of Jinan Rail Transit Underground Project is located in a section with complex hydrogeological conditions.Groundwater ecological protection,especially the protection of groundwater transportation channels in limestone fissures and karst caves,is an urgent engineering and technical problem to be solved in Jinan Rail Transit Underground Project construction.When underground water is blocked by a shield tunnel,it may cause water intrusion upstream,resulting in an increase in the water pressure difference between both sides of the tunnel.This project innovates the design concept and designs a new type of pipe segment with diversion function.The underground water can flow into the conduit inside the pipe segment through the water collecting pipe,and then flows to the stratum through the opposite water collecting pipe,playing a role in protecting the underground water and preventing the pipe segment from being subjected to bias pressure.In this paper,through indoor model tests,a diversion function segment model test box is designed and manufactured,through which the working state of the diversion function segment is simulated;Embed an earth pressure box and a pore water pressure gauge in the model box to measure the earth pressure and pore pressure around the segment under seepage bias pressure,and attach a strain gauge to the inner side of the segment to measure the stress and strain distribution of the segment.Research the diversion function of the segment model test box to study the repair effect of the diversion segment on blocking the flow of groundwater.Through numerical simulation,the pressure difference on both sides of the segment is changed,and the distribution and variation of stratum deformation,internal force of the segment,soil pressure around the segment,and pore water pressure are analyzed and studied.The main research results of this paper are as follows:(1)According to the model test of the diversion function segment,under the conditions of different pressure difference on both sides of the segment,the bottom,top and upper left of the segment generate compressive strain,and the compressive strain value at the bottom of the segment is the largest,and the tensile strain value at the bottom left,bottom right,right and left of the segment is the largest,and the tensile strain value at the bottom right of the segment is the largest;The strain value at each measuring point of the segment increases with the increase of pressure difference,and the strain value at the upper right of the segment changes from tensile strain to compressive strain with the increase of pressure difference;In addition,the strain difference at the symmetrical position of the segment increases with the increase of the pressure difference,which indicates that the greater the pressure difference on both sides,the more asymmetrical the strain produced by the segment,the more obvious the vertical elliptical deformation of the segment,and the more likely to cause damage.(2)According to the comprehensive comparison between the test results of the diversion function segment model and the numerical simulation results,the earth pressure and the total stress around the segment increase with the increase of the pressure difference,and the pore water pressure on the right side of the segment decreases with the increase of the pressure difference;Under the same pressure difference,the soil pressure,pore water pressure and total stress around the segment increase with the increase of depth.The soil pressure value of the segment is small on the left and large on the right,and the pore water pressure value and total stress value are large on the left and small on the right;In addition,the earth pressure difference,pore water pressure difference and total stress difference on both sides of the segment increase with the increase of the pressure difference,and the greater the depth is,the greater the difference is,the more obvious the bias effect of the soil pressure,pore water pressure and total stress on the segment is,and the segment is more prone to deformation.(3)According to the stratum settlement nephogram of different pressure differences,the upper soil of the tunnel segment is uplifted,and the lower soil is subsided,and the uplift value decreases with the increase of the distance from the arch top,and the settlement value also decreases with the increase of the distance from the arch bottom.In addition,with the increase of the pressure difference on both sides of the segment,the uplift value of the surface increases continuously.The maximum uplift point of the surface is at the center of the tunnel axis.The farther away from the tunnel axis,the smaller the uplift value.(4)According to the numerical simulation results,under any pressure difference,the maximum axial force of the segment appears at the tunnel arch bottom,the maximum tensile point of the segment is at the tunnel arch foot,and the maximum compression point of the segment is at the tunnel arch bottom.With the continuous increase of the pressure difference,the axial force and bending moment of the segment at the same position also continue to increase,and the maximum change of the axial force and bending moment appears at the tunnel arch bottom,which is a place worth paying attention to the internal force change.