| Fiber reinforced soil is a mixture obtained by uniformly mixing fibers and soil according to a certain ratio.Due to the simple construction process of fiber reinforced soil,low environmental impact,and low construction cost,it is an economically feasible method of soil improvement.Basalt fiber is a new type of inorganic environmentally friendly green high-performance fiber material,which has excellent properties such as high strength,corrosion resistance and high temperature resistance,and has a very good improvement effect on soil.In this paper,the typical loess in Xi’an,Shaanxi is taken as the research object,and the basalt fiber is used to improve the loess.The unconsolidated and undrained triaxial shear test(UU)explores and analyzes the factors such as fiber length L,fiber content η and confining pressure σ3.The influence of the stress-strain characteristics of reinforced loess,and the relationship between the deformation characteristics of reinforced soil and various factors was analyzed by means of noncontact digital image acquisition technology.Finally,based on the existing research results of the combined strength theory of the soil,the fitting correction is used to obtain the empirical formula for the combined strength theory of the reinforced loess under complex stress conditions.The main research contents are as follows:1.Carry out a triaxial shear test(UU)of basalt reinforced loess,analyze the influence of fiber length,fiber content and confining pressure on the strength characteristics of reinforced soil,and analyze the experimental results to conclude that adding fiber can strengthen the soil stress The hardening trend of the strain curve affects the constitutive behavior of the soil.As the confining pressure increases,the generalized shear stress of plain loess and reinforced soil increases;under the same confining pressure and fiber content,as the fiber length increases,The failure strength of the soil increases first and then decreases,and there is the best reinforcement length and the best fiber content;as the fiber content and fiber length increase,the cohesive force c increases first and then decreases,and the internal friction angle φ is affected by the fiber The influence of change is small,and the whole is fluctuating.The reinforcement coefficient R shows the trend of increasing first and then decreasing with the change of fiber length and fiber content,and the reinforcement coefficient R gradually decreases with the confining pressure.2.Using digital image acquisition technology to measure the evolution process of specimen failure deformation in the triaxial shear experiment,and use finite element calculation to obtain the soil surface strain field.Plain loess and low-fiber reinforced soil(less than 0.3%)are in the form of shear band failure,and the axial strain field corresponds to a large-strain region in a strip-like distribution;at higher fiber content,the soil body is swollen and damaged.The large strain area of the axial strain field is distributed laterally.Adding a certain length and an appropriate amount of basalt fiber can coordinate the deformation of the soil during the shearing process,making the failure deformation more coordinated.3.Summarize the classic combined strength theory of soil,based on the triaxial shear test data and uniaxial tensile test data of reinforced soil,select the quadratic parabolic joint strength model and hyperbolic joint strength model for fitting and correction,and derive It is applicable to the joint strength theory empirical formula of basalt fiberreinforced loess.Based on this formula,it is reasonable to judge the damage of reinforced soil with different fiber content and fiber length under complex stress conditions. |
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