| Fiber reinforced earth technology has been used in engineering practice in China since ancient times,but it has not yet formed a complete theoretical system.Thousands of years ago,in ancient China,natural fibers such as straw and hay were mixed into the soil and used for the wall structure of houses.The emergence of modern chemical fibers has added new development space to the engineering field.Modern fiber technology has developed rapidly in the engineering field with advantages such as environmental protection,easy construction,and low cost.Fiber reinforced soil technology has become a research hotspot of scholars at home and abroad.In the past 30 years,researchers at home and abroad have carried out a lot of work around the subject of fiber reinforced soil through various methods and means,and have made many important achievements.A large number of research results show that fiber reinforced soil can effectively improve the shear strength of the soil and enhance the destruction toughness of the soil.Nevertheless,the theory of shear strength of fiber reinforced soil under the action of large shear displacement is still not perfect.In this paper,the effects of fiber content,fiber length,effective normal stress,water content,dry density,and shear rate on the shear strength of fiber-reinforced soil are explored through the ring shear test.The following conclusions are mainly drawn:(1)Under the same shear displacement conditions,the stress-strain curves of plain soil and fiber-reinforced soil show different rules.The stress-strain curve of plain soil exhibits a single-peak structure,which decreases smoothly to residual strength when the shear stress reaches the peak value;while the stress-strain curve of fiber reinforced soil exhibits a multi-peak structure,which decreases to a certain strength after the peak value of shear stress The value begins to increase smoothly to the second peak,and then the shear stress decreases with the increase of the shear displacement,and so on to the residual strength value.(2)The peak strength and residual strength of fiber-reinforced soil are much greater than that of plain soil;the peak strength and residual strength of fiber-reinforced soil increase with the increase of fiber content and decrease with the increase of fiber length;the increase of fiber content causes The increase of cohesive force c has little effect on the internal friction angle φ;the fiber length has little effect on the shear strength index.(3)With the increase of effective normal stress and dry density,the peak strength and residual strength of fiber reinforced soil increase;with the increase of water content,the peak strength and residual strength of fiber reinforced soil decrease;The peak strength of fiber reinforced soil is greatly improved,but the residual strength is less affected by it.(4)As the shear displacement increases,the larger the fiber content,the more easily the strength of the fiber reinforced soil will show softening characteristics;the strength of the sample under the action of high water content will easily show the hardening characteristics;the test under the effect of high effective normal stress Sample strength is easy to show softening characteristics.(5)When the test is over,the upper shear plane shows a smooth shear failure state,and the shear plane "shears inward";the lower shear plane shows a layered,thick shear failure state.The state of the shear failure surface is greatly affected by the fiber content and effective normal stress.The smaller the fiber content of the sample,the easier the shear stress reaches the residual strength value;the lower the effective normal stress applied by the sample,the shear stress The more difficult it is to reach the residual strength value. |
