Test research on bearing capacity and negative friction force for single pile in collapsible loess ground
In order to study the problem of pile foundation bearing capacity caused by the collapsibility of loess in collapsible loess ground,a load-special immersion test was conducted using mechanically drilled cast-in-place piles(with a diameter of 0.8 m and a length of 26 m)at a construction site in Pingliang City.In the experiment,multiple sensors were installed on the pile body to analyze the axial force and lateral friction resistance of the pile body at different depths during the test process.The results show that the ultimate bearing capacity of the test pile in its natural state is greater than 13 200kN,and its stress characteristics are typical of friction piles.Due to the influence of the mud wall protection construction method on the immersion of the hole wall in the early stage and the uncertainty of the physical and mechanical properties distribution of the soil around the pile along the length of the pile,there are multiple peaks in the lateral friction resistance along the depth,with the maximum values occurring above the mud wall protection(pile body is 2-6 m).Under the special immersion test conditions of combining seepage holes and seepage pits,the negative frictional resistance on the pile side tends to stabilize on the 8th day of the immersion test,with the neutral point at the 8 m position of pile body and a negative frictional resistance of 107.6 kPa.During the test,the soil around the pile collapses in sections along the length of the pile,rather than gradually collapsing from top to bottom with immersion.SZH was subjected to pre-immersion,after the static load test,the neutral point appeared at a position of 12 m of pile body,with a negative frictional resistance of 127.8 kPa.Manual immersion tests mainly increased the axial force of the pile body above 8 m,while the neutral point position remained unchanged,indicating that the negative frictional resistance was significantly affected by the pile top load,immersion method,and immersion consolidation time.
万方数据
维普
