Study On Compressive Strength Test And Reinforcement Mechanism Of Straw Reinforced Soil

In recent years,natural reinforced materials have attracted the attention of researchers because of their advantages of convenience,economy and environmental protection.In this study,the surface morphology and tensile strength of straw reinforced soil were analyzed to verify its superiority as reinforced material.The unconfined compressive strength test was used to investigate the effect of reinforcement and the effect of reinforcement ratio and length on the compressive strength of reinforced soil.The optimum reinforcement condition of straw-reinforced soil was evaluated by the value of unconfined compressive strength and energy absorption capacity.Finally,based on the surface morphology of straw,the interaction mechanism between straw and soil particles is analyzed,the reinforcement mechanism of straw reinforced soil is studied,and the influencing factors of strength of straw reinforced soil are analyzed.The main conclusions of this study are as follows:(1)The results of SEM results showed that the outer surface of straw was covered with nearly hemispherical mastoid structure and tumor-like structure except root hair,which was helpful to enhance its adhesion and friction with soil particles,and was an ideal reinforcing material.The results of tensile test showed that the minimum tensile force of straw was 98.97 N,and the maximum tensile stress and elongation were improved and the flexibility was better after soaking.(2)Within the range of 0.1%～0.5%,the unconfined compressive strength of the reinforced soil reaches the maximum value when the reinforced soil is 0.2%,then,with the increase of reinforcement rate,the unconfined compressive strength of reinforced soil gradually decreases.when the reinforcement rate is the same,the unconfined compressive strength of reinforced soil shows the trend of first increasing and then decreasing with the increase of reinforcement length,and reaches the maximum value near 25 mm.(3)The stress-strain curves of reinforced soil and plain soil are Strain softening type,and the axial stress reaches the peak at about 0.4% axial strain;the failure of plain soil samples belongs to obvious shear failure,and the failure process of reinforced soil samples is "progressive" shear failure.(4)Taking into account the compressive strength value and energy absorption capacity of the specimen,it is concluded that the optimal reinforcement conditions under this test condition are as follows: the reinforcement rate was 0.2% and the length of the reinforcement was 20mm～25mm.Under the optimal reinforcement condition,the contribution rate of straw reinforcement to soil strength is 1.84～1.88.(5)The interaction mechanism between straw and soil particles mainly includes frictional effect,occlusal effect,connection reinforcement effect and energy absorption effect,all of which can improve the ability of reinforced soil to resist deformation and achieve soil reinforcement effect.