Experimental Study On The Servability Of Widely-Graded Soils As Anti-seepage Material

As a new type of anti-seepage material with good performance,widely-graded soil has obvious advantages over traditional clay and geomembrane in strength,deformation and other mechanical properties,as well as the acquisition of material and engineering cost.Widely-graded soil is gradually widely used in the field of anti-seepage project.Therefore,it is necessary to do further study on the engineering characteristics of widely-graded soil.In this paper,widely-graded soil as an anti-seepage material was selected as the research object.Firstly,four factors affecting its permeability characteristics were studied.The control variable method was used to explore the relationship between the physical characteristics of fine content,the content of fine part,the gradation,compaction work and saturated permeability coefficient,and then got the main control factors.Then,by controlling these four factors,a suitable mathematical model was established to acqiure common seepage control standards(Ks<1 × 10-7m/s)and higher seepage control standards(Ks<1×10-8?1× 10-9?1×10-10m/s)to meet certain anti-seepage requirements.Besides,the compression and consolidation as well as shrinkage characteristics of widely-graded soils were explored in order to get the influence of fine content and compaction work on the compression characteristics parameters and the relationship between fine content and volume shrinkage.Thus,we can get the scientific control measurements of post-construction settlement and shrinkage cracking of widely-graded anti-seepage materials,which can be used to guide engineering practice.Based on the above experimental study,the main conclusions were as followed:(1)The content of fine part,physical properties of fine content,compaction work and particle size distribution had significant effects on the permeability coefficient of widely-graded soils.The optimum fine content of widely-graded soils ranged from 30%to 40%;the permeability coefficient decreased with the increasing of liquid limit and plastic index of fine part and decreased in the form of negative exponential function with the increasing of compaction work.The permeability coefficient of continuous coarse-grained soils could reach 1/100 of discontinuous soils,and fine content was the main controlling factors.(2)Based on the four factors,the revised curvature coefficient Cc' was defined as the gradation control index of widely-graded soils.The seepage control standard of widely-graded soils with different physical properties was established respectively,and then we ed the calculation model of seepage control standard,so the seepage control standard of commom seepage control requirement(Ks<1 × 10-7m/s)of widely-graded soils was obtained.Based on that,a higher impervious standard was obtained by adding a certain amount of bentonite and increasing the compaction work.(3)With the increasing of fine content,the compression coefficient decreased rapidly at first and then increased gradually,and the compression modulus had the opposite tendency.When the fine content was between 20%-30%,the compression coefficient of widely-graded soil reached its minimum value and the compression modulus got its maximum value.Compressive modulus and defined modulus ratio ?=Emax/E0 increased in power function with the increasing of load.Compared with pure fine-grained soil,it can effectively reduce the compression coefficient of soil and increase the compression modulus.(4)With the increasing of the fine content,the volume shrinkage decreased rapidly and then increased slowly,and when the fine content was between 25%and 30%,widely-graded soils had the best dry shrinkage resistance.The volume shrinkage of 30%fine-grained soil was 0.386 times than that of pure fine-grained soil.Widely-graded soils could effectively reduce the shrinkage deformation of soils compared with pure fine-grained soils.