Experimental Study On Seepage Prevention Characteristics And Influencing Factors Of Dispersive Clay

Dispersive soil particles are small,the electrochemical gravity or binding force is weak,the soil particles are not condensed,and show the characteristics of dispersion in water.In addition,the dispersed soil is widely distributed in China,which is inevitable for engineering application.If there is no appropriate treatment and protection measures,it is easy to cause water conservancy accidents.At present,the existing research mainly focuses on the identification,deformation and anti-seepage performance of dispersive clay,and lacks the understanding of the basic properties of soil itself and the consideration of the influence degree between basic properties and anti-seepage performance.Therefore,after referring to a great many domestic scholars’ research results on dispersive clay,this paper conducted a great quantity of tests on the prepared soil with different dispersions at the bottom on the theoretical basis that the dispersion of soil can be changed by adding lime and sodium carbonate,and explored the basic properties of dispersed soil and its relationship with permeability,crack self-healing and other characteristics.The relationship between the basic properties of clay samples,such as limited water content,particle composition,mineral and element composition,porosity,pH,specific gravity and dispersity,is obtained.The permeability characteristics of different dispersive soils are explored through experiments,and the relationship function between the permeability coefficient of different dispersive soils and the amount of reagent added is made.Based on the crack scouring test,the self-healing characteristics of soil under the protection of different dispersive soil,different water head and different filter materials are summarized,and the great application potential of dispersive soil in engineering and corresponding treatment countermeasures are put forward.The following is the major conclusionw of the study.(1)The addition of lime can improve the cohesive force of soil particles and weaken the dispersity of soil.When lime content is 0.05%and 0.1%,the soil is still dispersive soil,but the degree of dispersion is weakened in turn;when the amount of lime is 0.2%,the soil is modified to transitional soil;when the content reaches 0.5%,the soil shows no dispersibility.The addition of sodium carbonate can increase the dispersivity of soil samples.When the content of 0.06%,the soil shows transitional property;when the content is 0.1%,0.2%and 0.4%,the soil shows dispersion characteristics,and the degree of dispersion of soil increases with the increase of sodium carbonate content.(2)The mineral composition of dispersive soil is montmorillonite,and it contains a lot of sodium ions;in the process of dispersion enhancement,the liquid limit increases,the plastic limit decreases and the plasticity index increases correspondingly;In addition,soil porosity decreased;The specific gravity of soil decreased;the alkaline enhancement of soil shows;the correlation characteristics change in the opposite direction when the soil dispersivity is weakened.The relationship between lime content and sodium carbonate content and soil particle weight is linear.(3)Through the permeability test,in the wake of soil dispersion increasing,the permeability coefficient of soil samples decreases gradually,and the permeability resistance is enhanced.The permeability coefficient of the dispersive soil is logarithmic.Viscosity,porosity and initial dry density all influence the permeability coefficient of soil,but the degree of dispersion is the primary factor of permeability coefficient in dispersive soil.(4)In the process of crack scouring,the soil and the filter material share the water head,and the filter material can effectively protect the soil.As time grows and with the rise of water head,the slope in the cracks of dispersive soil increases obviously,and the cracks gradually heal.In the soil with low dispersion,the collapse particles are larger and the gap silts up faster,but the final healing effect is poor.The results show that the particles on the crack surface of dispersive soil are smaller after wetting and disintegration,the crack healing is slower,and the final self-healing degree is better than that of non dispersive soil.In addition,the fracture self-healing characteristics are affected by the changes of soil basic properties and other indicators.When the plasticity index increases,the clay content increases,the alkalinity increases,and the soil specific gravity and porosity decrease,the slope in the fracture increases and the fracture healing quality becomes better.Among many factors,the self-healing performance of cracks is most sensitive to the influence of soil specific gravity.(5)The self-healing performance of the protected dispersive soil cracks is different with the different thickness of the filter material.Compared with the lower envelope filter material,the permeability velocity of the sample is relatively small when the upper and even line are protected.It shows that with the decrease of the filter material particles,the better the auxiliary seepage prevention effect of the filter layer is,the smaller the interference of the dispersive soil particles is affected by the increase of the head,the process of particles scattered and reunited is smooth,and the new siltation at the crack is more dense due to the small interference from the water flow,The better the healing degree of the fractures after a long time.In this paper,two groups of dispersive clay are tested simultaneously to ensure the correctness and universality of the conclusion.The results can be used as a theoretical guide for the application and treatment of dispersive soil in practical engineering.