Study On Mechanical Properties Of Fiber Reinforced Soil

Reinforced Earth Technology has been widely used in various projects since it came into being.It is an important technology in the field of civil engineering.Fiber reinforcing technology is a new type of soil improvement technology,which has attracted many researchers at home and abroad.As a material with good mechanical and Engineering Properties,fiber can be closely combined with soil particles,which can effectively improve soil engineering properties and improve soil strength and stability.In this paper,based on the previous research results,linear basalt,linear polypropylene and corrugated polypropylene fibers were selected as the reinforcing materials.Through the unconfined compression test and triaxial compression test,the fiber content,length and its own form were studied on the strength of fiber reinforced soil samples.The effects of water content and confining pressure on the shear strength and index of fiber reinforced soil samples were analyzed.The following results are mainly obtained:(1)The anti-deformation ability of soil was improved obviously by adding fiber.In the unconfined compression test,when the sample is destroyed,the long crack penetrates the sample and the crack is relatively wide on the surface of the plain soil,and the crack on the surface of the fiber reinforced soil is fine and dense.The mixing between fibers will further reduce the damage degree of the specimen,the crack becomes finer,and the position of the expansion and deformation of the sample will be changed.In the triaxial compression test,both the raw soil and the fiber reinforced soil were dilatation failure,but the expansion degree of the fiber mixed sample was obviously smaller.(2)Linear basalt and linear polypropylene fiber when mixed,the unconfined compressive strength of the reinforced soil samples increased firstly and then decreased with the increase of fiber content,and the unconfined compressive strength of the reinforced soil samples increased more with the increase of linear polypropylene fiber.When linear polypropylene is mixed alone,the increase of fiber length will improve the unconfined compressive strength of the sample,enhance the plastic characteristics of the sample,and change the failure form of the sample;When the waveform fiber is mixed alone,the fiber length has little influence on the unconfined compressive strength of the sample and increases the residual strength of the sample.(3)In the unconfined compression test,the fiber content will increase the stiffnessof linear polypropylene fiber reinforced soil in the online elastic stage,while the fiber length has no obvious effect on the sample;Fiber content has no obvious effect on the stiffness of linear basalt fiber reinforced soil;Fiber length will increase the stiffness of corrugated polypropylene fiber reinforced soil.(4)The influence of confining pressure on the shear strength of fiber-reinforced soil is greater at low water content,but decreased at high water content.At low water content,the shear strength of mixed sample of basalt and polypropylene fiber is more sensitive to confining pressure than that of mixed sample of linear and corrugated polypropylene fiber;At high water content,the change degree of shear strength to confining pressure is similar.(5)The addition of fiber can increase the cohesion or the Angle of internal friction of reinforced soil samples.The cohesion of mixed sample of basalt and polypropylene fiber increased obviously,and the internal friction Angle increased less;The cohesion and the angle of internal friction of mixed sample of linear and corrugated polypropylene fiber increased obviously.Linear basalt fiber mainly improves the cohesion of reinforced soil,while corrugated polypropylene fiber increases the angle of internal friction of reinforced soil.(6)The stress-strain characteristics of mixed sample of basalt and polypropylene fiber are strain hardening type,and the axial strain is in the linear elastic stage of0-3%,The stress-strain curve is less affected by water content and the stiffness has no obvious variety.The stress-strain characteristics of mixed sample of linear and corrugated polypropylene fiber were still of strain hardening type,and the linear elastic phase increased compared with that of mixed sample of basalt and polypropylene fiber,and the axial strain was 0~4.5%,is greatly affected by water content,the stress-strain curve of different water content is obviously separated and the stiffness changes obviously.