Study On Strength And Stability Characteristics Of Sprayed Straw Reinforced Loess

The existing fiber reinforcement technology has the defects of low construction efficiency and high construction difficulty when applied to slope protection,special-shaped hole filling,soil wall protection and other working conditions.Sprayed fiber reinforcement technology has the advantages of high construction efficiency,continuous construction and conveying distance,which is a kind of green and low cost reinforcement technology.However,there is currently a lack of research work on the strength and stability of sprayed fiber reinforced loess,which poses difficulties for engineering applications.Therefore,based on the concept of turning waste into treasure,this article selects common wheat straw fibers from loess areas,and conducts research on the strength and stability of sprayed straw reinforced loess.The details are as follows:(1)Considering that high-pressure air equipment is rarely used in reinforced soil and the sample preparation is difficult,the sample preparation scheme of the straw-shotted stiffened loess was studied first.After many tests,the optimization of initial moisture content of the sprayed straw reinforced loess material,the optimization of mold specifications,and the determination of fiber material length established.The sample preparation process of sprayed straw reinforced loess with shotcrete straw was determined.(2)The moisture content and fiber content of the sample are the key factors affecting the shear strength of the sprayed straw reinforced loess.With the same fiber content,the lower the water content of the sprayed straw reinforced loess,the greater the increase of the shear strength.The shear strength of sprayed straw reinforced loess with the same water content increased first and then decreased with the increase of fiber content,and the failure mode changed from strain softening to strain hardening.The optimum content of straw fiber is proposed from the perspective of shear resistance.(3)The disintegration resistance of the sprayed straw reinforced loess is obviously higher than that of unreinforced soil.The moisture content and fiber content of the sample are the key factors affecting the disintegration resistance of the sprayed straw reinforced loess.When the moisture content of the sample is low,the disintegration rate of the sample is fast,and the sample can quickly disintegrate to the fiber aggregation position,accelerating the disintegration of the sample.The residual amount of disintegration of the sample presents a change law of "first increasing and then decreasing" with the increase of the fiber content.When the water content of the sample is higher,the disintegration rate of the sample is slow,and the fiber groups can lock in more water to form a water barrier,further delaying the disintegration of the sample.The sample has not disintegrated to the position of fiber aggregation,the sample has been stable,and the residual amount of disintegration of the sample presents a change rule of "first increasing and then easing" with the increase of the fiber content.From the perspective of disintegration,the optimal content of straw fiber corresponding to different moisture content samples is proposed.(4)Dry and wet cycle tests of sprayed straw reinforced loess with different fiber content showed that:The sprayed straw reinforced loess with different fiber content all can well inhibit the generation and development of cracks caused by wet and dry cycles,but its resistance to wet and dry cycles presents a "first rise and then decline" rule with the increase of fiber content.With the increase of fiber content,the surface cracks of sprayed straw reinforced loess with the same dry and wet cycles first changed from the penetrating main cracks to the randomly distributed micro cracks,and then from the randomly distributed micro cracks to the random cracks with large width.The crack rate of the sample showed a change rule of "first decreasing and then increasing" with the increase of fiber content.The paper proposes the optimal amount of straw fiber from the perspective of crack resistance.The research results can supplement the related theories of reinforced soil,help to optimize the performance of reinforced soil,expand the application of fiber reinforced soil in large area slope protection,green building and other aspects,and the promotion,design,and scientific selection of construction methods for spraying straw reinforced loess engineering are of great significance.