| Fiber reinforced soil is an effective soil improvement technology.Studying the mechanical properties of fiber-modified Guilin red clay can provide theoretical basis for relevant practical engineering in Guilin.In this paper,the variation of mechanical properties of fiber-modified red clay under different fiber lengths and dosages was studied with Guilin red clay as the research object.The mechanism of fiber-modified red clay was discussed by means of electron microscopy(SEM)microscopic test.Based on the orthogonal experiment,the strength characteristics of fiber reinforced red clay under multi-factor coupling were studied.The multivariate nonlinear regression model of fiber reinforced red clay was established and verified.The main conclusions are as follows:(1)The physical properties of red clay were tested.The mineral composition and chemical composition of Guilin red clay were tested by X-ray diffraction and fluorescence spectroscopy,which provided effective basic data for later experiments.(2)When the fiber is mixed into red clay,the shear stress of fiber reinforced red clay under the length and dosage of each fiber is higher than that of plain red clay;the c of fiber red clay of each length reaches the peak at 0.5% fiber content;The fiber length and the amount of the fiber have a small effect on the fiber φ.In any dosage,the compression coefficient of 3mm fiber red clay is smaller than that of plain red clay,and the compression coefficient of 6mm fiber red clay is higher than that of plain red clay,but all are medium compressive soil.The incorporation of fibers failed to change the order of permeability of the red clay,and the permeability coefficient peaked at a length of 9 mm and a blending of 0.5%.(3)Based on the results of SEM microscopic test,the microscopic mechanism of the strength characteristics of fiber reinforced red clay is discussed.The shear strength of fiber reinforced red clay depends on the way of fiber reinforcement: short fiber,fiber in fibery soil with small content The mode of action is a ribbing effect,and the ability to increase the strength is limited;after the fiber length and the dosage increase,the fiber reinforced mode is converted into the plane lacing and the space network,and the strength of the soil sample is obviously improved;(4)From the microscopic point of view,the mechanism of compressive deformation of fiber-modified red clay is expounded: the short fiber with a length of 3 mm is filled in the inter-particle pores of the soil to increase the frictional force of the interface of the reinforced soil,and the integrity of the soil is enhanced.The compressibility is reduced;the fiber of6 mm length is mainly embedded in the soil in a "flat" manner,and the "joint" action of thefiber drives the movement of the soil particles,which improves the compressibility of the soil;when the fiber is longer and the amount is higher For a long time,the contact surfaces of the fibers increase,and the friction coefficient between the fibers is extremely small.Under the vertical pressure,the fibers are likely to slip between the fibers,and the soil particles adhering to the surface of the fibers are displaced and displaced.The compressibility of the soil.(5)It was found by electron microscopy that there are fine pores between the fibers in the red clay and the effective flow path for water circulation.The high-volume,long-fiber fiber red clay,the wider the water basin,the macroscopic performance of the soil-like permeability coefficient increases.(6)Using the orthogonal experimental design method,the effects of multi-factor coupling such as water content,dry density,fiber content and fiber length on the shear strength indexes c and φ of fiber red clay were studied.The test results were carried out by SPSS software.The extremely poor and variance analysis determined the optimal preparation process of c and φ and the significance of each influencing factor and established a multivariate nonlinear regression model of multi-factor and fiber red clay c and φ. |
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