Experimental Investigation On Mechanical Properties Of Reinforced Laterite And Its Application In Retaining Wall

The laterite is a kind of regional special soil,which is widely distributed in the south area of the Qinling Mountains-Huaihe River in our country.It is inevitable that the laterite will be involved during the construction of roads,railways,and houses.Compared with the ordinary fine-grained soil,the laterite has better mechanical properties but inferior physical and hydraulic properties.Adding geosynthetics in laterite to form a reinforced composite is one of the effective means to improve the properties of the laterite.Currently,there are few studies on the mechanical properties of reinforced laterite,which seriously affects the application of reinforced laterite in engineering.This thesis is targeted at the remolded fine-grained laterite.The differences in strength,deformation,and failure modes of unreinforced laterite and geotextile-reinforced laterite were compared and analyzed through a series of laboratory tests.Based on the study of the geotextile-soil interaction through direct shear interface test and triaxial test numerical simulation,the reinforcement mechanism was analyzed.Finally the feasibility of using laterite as the filling of the reinforced soil retaining wall was explored.On this basis,the engineering characteristics of the reinforced soil retaining wall under various working conditions were studied through the parameter analysis.The main research results are as follows:(1)The compressibility of laterite increases with the increase of moisture content and the decrease of compactness.The unconfined compressive strength decreases with the increase of moisture content and the decrease of compactness.The influence of moisture content is more obvious.Adding reinforcement can increase the unconfined compressive strength while changing the failure of the specimen from brittle failure to ductile failure.(2)The shear strength of laterite under triaxial compressive stress decreases with the increase of moisture content,and increases with the increase of compactness.The effect of reinforcement on laterite is mainly reflected in the suppression of the strain softening behavior of the specimen under low confining pressure and the improvement of the peak deviatoric stress.The effect of reinforcement increases with the increase of the reinforcement stiffness,the reinforcement layers,and the moisture content of the laterite,and decreases with the increase of the confining pressure.In addition,the test results also show that the lateral deformation of the specimen can be restrained by the reinforcement.The effect of reinforcement on shear strength parameters is mainly manifested in the increase of cohesion,while the change of internal friction angle is small.(3)The shear strength of the geotextile-laterite interface decreases with the increase of the moisture content.The numerical simulation results of the triaxial test show that the frictional resistance of the interface changes the stress field of the soil within a certain range near the reinforcement,increases the minor principal stress of the soil,changes the failure mode of the soil and improves the overall strength of the reinforced soil to some extent.The equivalent confining pressure mechanism can explain the experimental phenomenon well.And the effect of the reinforcement is related to the apparent cohesive force of laterite.The higher the apparent cohesive is,the less obviously the triaxial compressive strength of the reinforced laterite increases.(4)The numerical simulation results of reinforced laterite retaining wall showed that laterite can be used as the filling of the reinforced soil retaining wall.On this basis,the parameters of the moisture content of filling,the reinforcement stiffness,the reinforcementsoil interaction,the overload,and the local load were analyzed,and corresponding engineering practice suggestions were put forward based on the results of parameter analysis.In particular,water proofing and drainage measures should be taken for the reinforced laterite retaining walls.