Model Test Study On Flexible Pile-Net Composite Foundation Under The Rigid Foundation

Since the 21 st century,the composite foundation technology has been widely used in the construction of China's infrastructure,and has achieved rapid development.Among them,the flexible pile-net composite foundation is a new type of method to deal with the soft ground after the experts and scholars have studied the existing flexible pile composite foundation in-depth and meticulous.Flexible pile-supported reinforced composite embankment has been widely used in road and railroad subgrade reinforcement projects,but it is less widely used in foundation treatment of buildings.Based on the flexible pile-net composite foundation model,this paper explores the working mechanism of the flexible pile-supported reinforced foundation from the three aspects of whether there are grids,different pile diameters,and the size of prestress on the grid.Get the following conclusions:1?The flexible pile-supported reinforced foundation is a new type of method to deal with the soft foundation after the in-depth study of the existing flexible pile composite foundation.Compared with the composite foundation of a flexible pile,the flexible pile-supported reinforced foundation has less deformation,greater bearing capacity and more reasonable stress.Therefore,it is a good idea to use flexible piles and grids to deal with foundations with insufficient carrying capacity.2?Settlement change law of flexible pile-supported reinforced subgrade:(1)With the increasing of flexible pile diameter,the settlement value of flexible pile-supported reinforced ground gradually decreases,so the bearing capacity of composite foundation The capacity is increasing;when the same load is applied on the ground,the settlement value of the flexible pile-net composite foundation will gradually decrease with the increase of the prestress applied on the geogrid,so the composite foundation The carrying capacity continues to increase.(2)The total settlement of the foundation is composed of three parts: cushion settlement,soil settlement between piles and settlement of bearing layer,but the proportion of soil settlement between piles and settlement of bearing layer accounts for a large proportion of total foundation settlement.(3)When the load is small,the ps curve is relatively flat.With the gradual increase of the load,the settlement also gradually increases.When the load reaches a certain value,the ps curve becomes steeper,and the speed at which the settlement increases increases.fast.(4)The larger the pile diameter of flexible pile,the faster the settlement of the composite foundation increases.The greater the prestress applied on the geogrid,the slower the settlement of the composite foundation increases.3? The variation law of the axial force of the pile body in the flexible pile-supported reinforced foundation:(1)The applied load on the foundation becomes larger,and the axial force of the flexible pile body also becomes larger.(2)When the load imposed by the local base is small,the axial force of the pile body changes slowly.With the increase of the load,the axial force of the pile body changes gradually.(3)In the flexible pile-supported reinforced foundation,the axial force of the flexible pile gradually increases from the top of the flexible pile to the neutral point.From the neutral point to the bottom of the pile,the axial force of the flexible pile slowly decreases.(4)The larger the diameter of the flexible pile,the greater the axial force that the pile bears.When the same load is applied on the local base,the axial force of the flexible pile increases with the prestress applied on the geogrid.Large and constantly decreasing.4?The change law of the lateral friction resistance of the pile body in the flexible pile-supported reinforced foundation:(1)The load imposed on the flexible pile-net composite foundation gradually increases,and the lateral friction resistance of the flexible pile body also increases gradually.Big.(2)The larger the diameter of the flexible pile,the greater the lateral friction resistance of the pile body;when the same load is applied on the local foundation,the lateral friction resistance of the flexible pile body is affected by the geogrid.Increased stress increases.(3)On flexible piles,from the top of the pile to the neutral point,the negative friction resistance of the pile body first increases and then decreases;from the neutral point to the effective pile length,the pile body is subjected to positive The resistance gradually increases along the pile.5?The variation law of pile-soil stress ratio in pile-supported reinforced pile foundation:(1)The pile-soil stress ratio is always greater than 1,indicating that the flexible pile plays an important role in bearing.(2)With the continuous increase of the load imposed on the upper part of the foundation,the stress ratio of the pile-soil is constantly increasing,and the stress-strain ratio of the pile-soil is also relatively large.(3)The larger the diameter of the flexible pile,the greater the stress ratio of the pile to soil in the foundation;the same ratio of pile to soil stress applied to the geogrid when the same load is applied on the foundation.The prestress increases and increases.6?The ratio of the earth pressures above and below the grid in a flexible pile-supported reinforced foundation:(1)The ratio of the earth pressure under the grid in the cushion to the earth pressure on the grid is greater than 1,ie the soil under the grille in the cushion The pressure is greater than the earth pressure on the grille.(2)As the load increases,the ratio of the earth pressure under the grid to the earth pressure on the grid also increases.(3)The larger the pile diameter of the flexible pile,the larger the ratio of the earth pressure below the grille to the earth pressure on the grille;with the increasing prestress on the geogrid in the cushion,the cushion The ratio of the earth pressure under the grille to the earth pressure on the grille is gradually decreasing.7?The law of pull-up force on the grid in flexible pile-supported reinforced foundation:(1)As the load imposed on the composite foundation increases,the tension on the grid in the cushion also increases.(2)When the load is small,the change of pulling force on the grid is relatively slow,but as the load increases,the change of the pull force on the grid also increases gradually.(3)The larger the pile diameter of the flexible pile,the smaller the pull force on the grille in the cushion layer;as the prestress on the grille in the cushion layer increases,the pull force on the grille in the cushion layer also increases.And the pull on the grille is also changing.