The Research On Study On Mechanical Properties Of Improved Soil In Red Sandstone

A large number of red sandstones are distributed in a highway section of west Hunan.Such rock masses have the characteristics of low strength,poor water stability and easy disintegration.How to effectively use red sandstone as a filler to fill the roadbed is a problem that needs to be solved in this project.Through field investigation,geotechnical test,engineering site inspection and theoretical analysis,the mechanical properties of the improved soil in west Hunan red sandstone are studied and used in practical engineering applications.The main research work includes the following:(1)Based on laboratory experiments,the physical properties,disintegration characteristics,particle size distribution,liquid plastic limit and compaction characteristics of weathered red sandstone of a highway in Hunan Province were analyzed,which provided basic data for the study of mechanical properties of red sandstone.(2)The bearing ratio of CBR,expansibility,direct shear and elastic modulus of red sandstone undisturbed soil was studied,and the basic mechanical properties of red sandstone were studied.(3)The mechanical properties of red sandstone improved soil were studied by bearing ratio CBR,direct shearing,rebound modulus and unconfined compression under dry and wet cycles.The improvement of red sandstone at home and aboard was analyzed and compared.By comparing the mechanical properties of lime and cement and combining with engineering practice,the cement is selected as a modified scheme for the red sandstone filling of a highway in Western Hunan.(4)Cement modified red sandstone samples under the normal triaxial test conditions,the test curves can be described by hyperbola,and the stress-strain relationship satisfies Duncan's model.Using the regression tangent equation of the Mohr circle under three confining pressure environments,the Moire-Coulomb principle presupposes the internal friction angle and cohesion of the red sandstone undisturbed soil and the improved soil,revealing that the incorporation of cement can greatly enhance the cohesion of red sandstone.Force and internal friction angle.As the cement content increases,the shear strength and initial modulus of deformation of the soil are gradually enhanced.The influence of cement content on the failure ratio is not obvious.The initial modulus and ultimate deviatoric stress difference of the unmodified red sandstone soil is smaller than that of the cement modified red sandstone soil.The initial deformation modulus and the values of the parameters K and n increase with the increase of cement.(5)Deformation analysis based on D-P model shows that the maximum deformation value of the weathered red sandstone subgrade under driving load is 2.71mm,which is larger than the design requirement of 1.77mm.The maximum deformation of the subgrade with 3%cement content is 1.66mm,which meets the design requirements,but at this time the subgrade soil is close to plastic failure.When 4%cement is used,the maximum deformation of the subgrade is 1.12mm,and the stress-strain state of the subgrade is basically consistent with the experimental conclusion.(6)By comparing the field test results of the field improvement section and the unmodified section test road,it can be known that the roadbed filled by the red sandstone improved soil meets the design requirements.