Disease Mechanism And Treatment Measures Of Red Filling Subgrade In The Declivity Sections Of Chengdu-anyue-chongqing Expressway

Most previous studies believed that rainfall infiltration was the main factor that caused the red filling subgrade diseases in the declivity sections.The subgrade diseases caused by drainage clogging were not paid attention to.The two-dimension seepage model was mostly used in previous studies,which could not truly reflect the three-dimension seepage field in the subgrade and the three-dimension failure form of the subgrade slope.Therefore,it is necessary to study the influence of drainage clogging on the three-dimension seepage field of the red filling subgrade and the three-dimension damage range of the subgrade slope in the declivity sections.In this thesis,based on the spatial curved surface settlement failure of the red filling subgrade in the declivity sections of the Chengdu-Anyue-Chongqing Expressway,the disease mechanism of the red filling subgrade in the declivity sections is analyzed.Through compaction test,large direct shear test and triaxial test,the physical and mechanical properties of the red filling are studied.And use FLAC^3D software to simulate rainfall infiltration and drainage clogging（drainage clogging takes into account the changes of 4 factors,namely the height of the water pressure in the pipe,the clogging position,the height of the subgrade,and the angle of the declivity sections）to the influence of the three-dimension seepage field of the red filling subgrade and of the slope stability of the subgrade in the declivity sections.Finally,it provides a reference method for preventing and controlling such subgrade diseases.The main research conclusions of this thesis are as follows:（1）The red filling subgrade is often kept in a stable state in a dry environment.But when the red filling subgrade is soaked in water,the water stability of the red filling is extremely poor.After being soaked in water,it will soften and disintegrate,and the shear strength parameters will decrease,the density of the filler increases at the same time,which is the main reason for the disease of the red filling subgrade in the declivity sections.（2）The biggist dry density of the red filling(_dmax=1.872g/cm³)and the optimum moisture content(_opt=9.53%)are obtained through the compaction test.Different stone content has a great influence on the physical and mechanical properties of the red filling.The internal friction angle and cohesive force of the red filling decrease with the decrease of the stone content.Different water conditions have a severe influence on the physical and mechanical properties of the red filling.After being soaked in water,the strength of the red filling drops very obviously.（3）After the drain pipe is blocked,the three-dimension seepage field of the subgrade appears as a higher position close to the drain pipe and a lower position far away from the drain pipe.The plane projection of the seepage field is distributed in a"fan"shape,and the subgrade slope produces a spatial curved surface settlement.Among the four factors that affect the three-dimension seepage field of subgrade,the higher the water pressure in the pipe,the closer the blockage position is to the subgrade slope,and the higher the subgrade height will expand the range of the seepage field,and the larger the angle of the declivity sections,the smaller the seepage field range.Among the four factors that affect the stability of subgrade slopes,the higher the water pressure in the pipe,the closer the blockage position is to the subgrade slope and the larger the declivity section angle will definitely accelerate the subgrade slope damage,and will reduce the vertical damage range of the subgrade slope.And the higher the height of the subgrade,it will relatively slow down the damage of the subgrade slope,and the extent of the vertical damage of the subgrade slope is enlarged.（4）For the undamaged red filling subgrade,it is recommended to groute from the side slope of the subgrade by drilling holes to improve the mechanical properties of the red filling and prevent subgrade diseases.It is recommended to use vegetation to protect the subgrade slope to enhance the erosion resistance of the subgrade slope.At the same time,vegetation can beautify the environment.It is recommended to use plant roots to enhance the shear resistance of the subgrade slope soil.