Study On Swelling Characteristics Of Rock And Soil Mass Of Piers Of Jian Shan-ying Bridge On Guiyang-guangzhou High Speed Railway

Guiyang to Guangzhou high-speed rail passes through the Jian Shan-Ying bridge of Chang Ming Town,Guiding County,Guizhou Province,and is located in the core of the Chang Ming syncline.The pier shows the uplift in the rainy season after field monitoring data and the dry season sank.Under the background of this study,this paper mainly studies the swelling characteristics of the overlying rock mass of the pier.Through the change of the dry density of rock and soil and the initial water content,the swelling deformation of rock samples under certain axial load and internal pressure and the value of expansion stress are simulated.The relationship between the water absorption of rock and soil and the volume of rock and soil body during the expansion and deformation process is obtained.The main research results of this paper are as follows:(1)Summarizing the existing expansive force instrument,this paper designs a set of dilatometer.The instrument can study the dilatancy and shrinkage characteristics of rock and soil,and explain the operation principle,internal structure and test procedure of the test instrument.The error of the test results is mainly caused by the piston friction force.The value is 0.08 MPa,and the solution to reduce the error is put forward.(2)Through indoor physical and mechanical test,the basic parameters of rock and soil are obtained,and the change of Jian Shan-Ying is compared.It is found that the main factors affecting the lifting of the pier are the expansion rock.Among them,the expansion potential of pier 4,5 and 8 is the largest,and the value of free expansion rate reaches 82%,which accords with the statistics of site monitoring.Through the swelling potential of rock and soil,the swelling characteristics of cores 4,5 and 8 are tested.(3)In the expansion deformation test,in addition to the expansion strain curves of different dry density and different initial water content,the relationship between the water absorption and volume change of rock and soil is also found-the amount of water is larger than the volume expansion.(4)Under the condition of initial moisture content,the swelling stress of rock and soil is exponentially related to dry density.The larger the initial moisture content,the smaller the expansion force.Under the same initial moisture content,the swelling force increases with the increase of dry density.The smaller the initial moisture content,the greater the change trend of swelling force.Considering the particularity of the Jian Shan-Ying bridge,the expansion and deformation of the overlying rock under the pier is simulated by the self-made expansive instrument,which provides a theoretical basis for the construction of the south line and the high iron line through the expansive rock formation.