Transfer Law Of Axial Force And Response Of Lateral Load For Pile Impaling Karst Caves At Slope By Test

The distribution of karst is extensive in China,and the surface of the rock layer often is inclined.Transfer law of axial force and response of lateral load for pile when the pile passing through multiple layers of caves are not very clear,which restricts the reasonable selection of pile foundation parameters and safety evaluation.The model test and loading system were designed to test the transfer law of axial force when piles passing through multi-layered cavities and the variation characteristics of lateral load for pile when the horizontal force response of piles under constant pile top load at slopes,and to analyze the p-y curves of piles in the upper soil layer and its fitted curve characteristics,so as to provide a test basis for the Karst piles study about engineering properties and engineering design evaluation at slopes.The results show that.(1)When the pile top is pressurized,the pile settlement increases with the increase of pile through the layer of cavity,and the curve of the axial force of the pile in soil layer is trough,the axial force at the cavity and the cavity bottom plate appear local maximum and local minimum respectively,which decreases with the increase of cavity depth,the more the pile pass through the layer of cavity,the deeper the axial force is.(2)When the fixed load on top of pile and lateral stacking,the soil settlement and pile lateral displacement increase with the increase of the number of cavity layers,and the pile lateral displacement mainly occurs above the first layer of cavities.The number of cavities increases and the lateral shift at the bottom of the soil layer increases.(3)When the fixed load on top of pile and lateral stacking,the soil pressure and soil resistance curves of the pile body in the soil layer are outwardly "convex",and the extreme value point of the outer "convex" pile is in the lower part of the soil layer,while the extreme value point of the soil pressure of the pile without cavities is in the upper part of the soil layer at the beginning of the loading,and the extreme value point moves towards the soil layer as the load increases.The point of maximum value transitions to the lower part of the soil layer as the load increases,indicating that the load has the characteristic of transferring to the deeper part of the soil layer during lateral pile loading.The soil resistance of the pile body is much smaller than the soil pressure at the corresponding position,which means that the pile body is mainly subjected to soil pressure under the action of lateral pile load at the slopes.(4)When the fixed load on top of pile and lateral stacking,the pile bending moment appears at the fixed position in the soil layer,and the pile bending moment above the bending point is outwardly "convex",while the pile bending moment below the bending point is "<".As the load level increases,the outer "convexity" becomes more and more obvious,and the"<" angle becomes smaller and smaller.The maximum pile bending moment increases with the increase of the number of cavities.(5)The p-y curves of the pile body in the soil layer are fitted with a varying between 0.0061 and 0.582 and β varying between 0.2785 and 0.7198.The β at each point of the monopile is more sensitive to the number of cavity layers the pile passes through.