Interface Shear Characteristics Of Geosynthetics And Clays Based On Landfill Liner System

With the rapid development of our country's economy,more and more people live in cities,and more rubbish is produced in cities.At present,the main method to deal with the sanitary garbage in China is still landfill,which also promotes the large-scale construction of sanitary landfill in China's large and medium-sized cities.however,because of multi-layer seepage control system,and the seepage control system each layer material tensile properties and interfacial shear strength is put in bigger difference,making the interface between the different seepage control layer shear transfer mechanism is very complex,at the same time also caused when using multilayer composite liner as impervious layer,landfill in design difficulty.Based on geosynthetic in the landfill liner system and modified clay compaction as the research object,mainly for the clay and the interface between the geosynthetic material shear test,analysis of the stress-strain curve under different stress level,the interface between the geomembrane and geotextiles shear test and creep test interface,analyzes the change rule of stress-strain curve under different stress level,and creep curve change rule,and indeed into material between the direct shear friction coefficient of impermeable layer,interface as the cohesive force,the related parameters such as interface friction Angle and liner system in the peak shear stress between the layers,These parameters can provide a reference for the application of gasket system in practical engineering.The main research contents and conclusions of this paper are as follows:(1)To study the mineral composition of different modified clay and interface shear stress effect of geosynthetic,using the improved direct shear apparatus,the modified clay andgeosynthetic between interface shear test,the test results show that when the normal stress is low,mainly for two stage,elastic stage,stable stage,in the high normal stress there are three stages,three kinds of clay elastic stage,strain softening stage and stable stage.The strain softening of smooth geomembrane is obvious,while the strain softening of cylindrical geomembrane and non-woven geotextile is not obvious.The application of cylindrical point geomembrane and non-woven geotextiles can effectively improve the interface friction performance of the gasket system and alleviate the strain softening phenomenon.When the normal stress is high,the peak shear force is about twice that of smooth geomembrane,and the interface friction performance of cylindrical point geomembrane is close to that of non-woven geotextile.For geotextile,the interface shear and friction performance of clay-geotextile interface is mainly affected by soil type and normal stress,which is a key factor affecting the overall performance.Generally,"sliding" is triggered under lower normal stress,while "sliding + tillage" is triggered under higher normal stress.Tillage is the main cause of texture cracking of geotextile.Loading direction larger influence on geotechnical fabric structure,thus further influence the interface shear stress behavior,in which parallel to the loading direction is vertical than harder to resist shear force,because when the vertical loading direction,a spinning geotextiles prone to crack,crack extension with the increase of the shear stress and shear displacement will damage a spinning geotextiles structure,reduce spinning geotextiles stiffness.The higher interlayer friction can not only reduce the relative slip between geotextile and layer,but also enhance the shear resistance of geotextile.Therefore,the stress-displacement curve will be improved.In addition,the similar cohesive force and internal friction Angle between different geotextile and clay interface can be used as engineering reference.(2)Landfills in composite liner system,geosynthetic and interfacial friction between geosynthetic performance is the most weak,in order to study different kinds of geomembrane and geotextiles between the interface friction performance for a long time,by changing the types of geomembrane,the types of geotextiles and spinning the loading direction of geotextiles,interface of geomembrane and geotextiles interface shear test and creep test interface,test results show that:When using smooth geomembrane base,geotextiles shear displacement curve similar to clay,but the interface shear strength is much lower than smooth geomembrane and shear strength of clay,non-woven geotextiles,spinning geotextilesmeridian texture with loading direction is vertical and parallel,they form of interface shear stress and strain curve is also similar.The strain softening between the cylindrical geomembrane and the geotextile is not obvious,which is mainly manifested in the elastic stage and the stable stage,that is,the shear stress increases rapidly and reaches the peak strength at the beginning of shear,and then tends to be stable with the increase of displacement.The shear peak strength of the interface is greatly improved when the cylindrical point geomembrane is used.In terms of interface creep of geosynthetic,both smooth geomembrane and cylindrical geomembrane have constant creep mode under high stress,that is,the displacement increases with the increase of time and the rate is the same.Under the similar shear stress,the creep rate of cylindrical geomembrane and non-woven geotextile can be reduced,but not much.Column point geomembrane + has spun geotextiles point(parallel)and column(vertical)geomembrane + has spun geotextiles creep curves of the shape differences,found a spinning using column point geomembrane + geotextiles(vertical),The main reason is that with the increase of shear time,under the action of horizontal shear force,the column point geomembrane on the lower surface will pull on the interface of geotextile,resulting in tiny cracks in its texture structure,so it is easy to produce large displacement.