Experimental Study On Influence Factors On Bearing Capacity Of Sand Foundation Reinforced By Geogrids Under Aging

With the proposal of the national "One Belt and One Road" plan,relatively higher requirements have been put forward for China's railway,highway and other infrastructure construction.Therefore,how to ensure the stability and safety of the foundation is an urgent problem that needs to be solved by the builders of the vast engineering road.Geogrid is widely used in reinforced engineering due to its prominent advantages of light weight,high strength,large deformation modulus,convenient construction,certain flexibility,and strong bite force between tendon and soil.In the geogrid reinforced foundation under the action of vertical load,the friction between the geogrid and the filler would produce a horizontal pulling force,which can increase the strength of the soil,limit the deformation of the foundation,and prevent the uneven settlement of reinforced soil foundation by geogrid.Study on geogrid tensile,creep,aging,direct shear,interface characteristics of geogrid-soil,bearing capacity of geogrid reinforced soil,creep behavior of geogrids after aging,interface characteristics of geogrid-soil after creep and other relevant results have been achieved in China.However,little research has been done on the test of the bearing capacity of reinforced ground after geogrid aging.In this paper,based on the national natural science fund project(51578359),with geogrid as the research object,firstly,three kinds of geogrids(two-way geogrid TGSG1515,two-way geogrid TGSG2525 and a three-way geogrid)are used to withstand 700 h photooxidation aging in the xenon lamp aging test box whose radiation intensity was 500W/ m~2 and 600W/m~2 respectively.Then a series of reinforced foundation plate load tests indoor were performed.The earth pressure was measured by the earth pressure boxes and the subsidence was observed with two dial indicators.The effect of the applied grid on the bearing capacity of the reinforced subgrade,the earth pressure in the foundation and the effect of the stress diffusion were investigated.The influence factors of the geogrid-reinforced ground on the bearing capacity,the earth pressure and deformation law in the foundation were analyzed.The following conclusions were obtained:(1)After the geogrid is added to the foundation,the bearing capacity of the foundation is increased and the settlement is relatively reduced.The reinforcement effect of the geogrid will only begin to play after the applied load reaches a certain value,and the reinforcement effect will more and more obvious as the load increases.The reinforced effect of the reinforced ground by aging geogrid is between the unreinforced ground and the not aged reinforced ground.(2)Bearing capacity,displacement,and earth pressure in the foundation of Geogrid-reinforced ground are related to many factors,such as the type of geogrid,the shape and size of the geogrid hole,the ultimate tensile strength of the geogrid,the ageing degree of the geogrid,and the geogrid specimen size and test conditions and so on.Within a certain range,the greater the ultimate strength of the geogrid,the lower the degree of aging geogrid and the larger the size of the specimen,the better the reinforcing effect of the foundation.The size and ultimate strength of the geogrid have a greater influence on the reinforcement effect of the foundation and the degree of aging of the geogrid has relatively less effect on the reinforcement effect of the foundation.(3)The earth pressure at the center point of each layer in the foundation is the largest.As the horizontal distance to the center point of the load plate increases,the earth pressure gradually decreases.As the vertical distance to the center of the load plate increases,the earth pressure also decreases.After the sandy soil foundation is reinforced by geogrid,the stress in the foundation is changed.At the same point,the earth pressure of the geogrid foundation is smaller than that of the unreinforced foundation.The greater the strength of the geogrid,the lower the degree of aging,the larger the size of the specimen,the smaller the earth pressure at the same point.(4)In the practical application of reinforced earth engineering,reasonable dimensions and the effect of the aging of reinforced materials on the bearing capacity of foundations should be taken into consideration,the matching of the geogrid hole and the sand should be considered.When designing the foundation involved the relevant ultimate bearing capacity,etc.,it should be appropriately reduced according to local experience.