Bearing Capacity And Negative-friction Effect Study Of The Squeezed Branch Pile

To solve the problem of settlement and bearing capacity of the pile, various of special-figure piles was invented.The squeezed branch pile is a representative one, Through a dedicated drilling equipment,set up a number of bearing plates on the pile body. The presence of these bearing plates increased contact area with the under-plates soil, the part of the friction converted to end bearing force, which fully used the bearing capacity of the under-pile soil, The force mechanism of bearing capacity was improved. The squeezed branch pile with zhe advavtage of high bearing-capacity, strong anti-settlement, material saving, lower cost.So has been widely used.Through the vertical bearing capacity and negative friction resistance test of three different branch seted model piles, Found that under vertical load the pile settlement curve was graded one, obviously plunged section does not appear, in the range of ultimate load,Settlement with decreasing with the increases of branch distance; branch pile axial force decreases along the depth, the support plate’s load-sharing effect is obviously, plummeted axial forces occur in the upper portion of the support plate,on the top plate the amount reducing of small and large at the lower plate.This shows that the carrying capacity of the soil under the plate largely determine the carrying capacity of branch pile, so the branch pile design should support plate set at a higher-load carrying-capacity-soil; negative friction greater impact on the lower plate more than the top plate,at about 4-5 times, and other locations have little effect, the neutral point increase from the rise with the distance of the plates after the first fall, when the distance is equal three times,the neutral point is the lowest, the neutral point approximate 0.5 to 0.6 times of the length of the pile, litter higher than the pile specification provided one, Too large axial force of the lower plate is adverse with the pile settlement control, design and construction should be given more attentions. Also used the finite element software ANSYS to comparative analysis, numerical simulation results is in good agreement with the experimental results, and further study of soil parameters, support plate spacing on branch pile bearing capacity of soil modulus, cohesion, internal friction angle increases help to improve the carrying capacity.For the branch and plate pile group under vertical loads, load-shareing of the center pile, the angle pile, and the side pile was In turn reduced, mainly differ with the single pile,the top plate bear most of the load, capacity of the lower plate is very weak, the top plate can be shallowed work with platform together, more conducive to improving the carrying capacity of the piles group.