Study On Direct Shear Creep Characteristics Of Q₂ Loess Reinforced With Palm Fiber

Loess is a special kind of soil,which has the characteristics of macropore,collapsibility and poor engineering properties.Improving the mechanical properties of loess and preventing geological disasters in loess area has always been a research hotspot in the field of geotechnical engineering.Researches show that fiber reinforced technology is an effective way to increase the strength of loess.Fiber reinforcement can inhibit the development of soil cracks,increase soil toughness and enhance soil strength,which has been widely used in engineering construction in loess area.However,most of the researches on reinforced loess focus on shear strength,tensile strength and compressive strength,and few on creep effect and micro structure change of reinforced loess under load.Taking Q2 loess reinforced with palm fiber as test material.Through direct shear test and direct shear creep test,the influence of fiber length and content on the strength and deformation of reinforced Q2 loess was explored.By means of polarizing microscope and scanning electron microscope(SEM),the strengthening mechanism of reinforced Q2 loess was analyzed from micro level.The main research results are as follows:(1)The effect of fiber reinforcement makes the shear behavior of soil change fundamentally.The stress-strain curve of unreinforced Q2 loess is strain softening type,and that of reinforced Q2 loess is strain hardening type.The results show that the reinforced Q2 loess has plastic failure,the soil toughness is improved,and the resistance to large deformation is increased.(2)The shear strength of reinforced Q2 loess is significantly higher than that of unreinforced Q2 loess.Through direct shear test,the optimum content of reinforced Q2 loess is 0.6%?0.8%.(3)Fiber reinforcement can inhibit the creep deformation of soil and improve the long-term strength of soil.The long-term strength has a peak value when the fiber content is 0.6%.(4)The surface of palm fiber is rough with grooves and independent pore chambers.Under the action of friction and compression,soil particles are embedded into the groove and hole chamber,which is conducive to increasing the effective contact area between fiber and soil particles and enhancing the force of reinforcement soil interface.(5)With the addition of fiber,the micro pore structure of soil is changed,the proportion of macropores is reduced,the number of small pores is increased,and the pore distribution is more uniform.It is beneficial to increase the effective contact area of reinforcement soil interface,enhance the interaction of reinforcement soil interface and restrain the creep displacement of reinforced loess.