Numerical Analysis On Settlement Influence Of New Type Ribbed Prestress Pipe

In the 21st century, the construction technology of pile foundation continues to be updated and improved in the direction of low-pollution, pile with reaming, special-shaped pile, submerged pile, portfolio constraction process pile, high-strength pile and a variety of pile body materials. In this development tendency, Zhejiang Tianhai Pipe Corporation put forward to a new type pile foundation—a new type ribbed prestress pipe, to improve the bearing capacity of single pile based on expland the pile-soil contact area. Dependent on static pressure, this pile push into soil then use mechanical trailer coupling pile extention instead of welding pile extention. Therefore it has those advantages: convenient construction, stability quality, low noise and so on.As a relatively new type pile, this prestressed ribbed pipe even though the new technology works in practice effect, but are still in the stage of technology development and application, lack of a systematic study in theory. Compared with the traditional pre-stressed pipe, pipe lateral side is added to ring-shaped convex rib and longitudinal convex rib. Therefore, researching the influence law to settlement under the change of structure dimensions can provide the reasonable basis for design and construction of future engineering. Based on the static load test,combined with the study of Japanese nodular piles, settlement of new type ribbed pretressed pipe pile is discussed in this paper. The research in this paper mainly including:1,Based on the summary of pile settlement calculation method, combining with《Technical Code for Building Pile Foundations》(JGJ94-2008) and calculating additional stress of foundation soil Mindlin stress factor considering piles diameter impact, using elastic theory method, the settlement of new type ribbed prestress pipe under vertical load were deduced. Using the two engineering examples from Hangzhou, Zhejiang, the vertical compression static load test results for new type ribbed prestress pipe with different lengths verified recommended calculation method of application any further. To change the under part length of annular flange rib of new type ribbed concrete pipe with calculation method, comparison in both groups,it is found that, the settlement is increase with the increase of the under part length of annular flange rib, but the increasing amplitude decreases. When the load is a certain level, the settlement is basically unchanged, the trend is relatively stable. Finally the paper puts forward the suggestion that practical engineering application of the under part length of annular flange rib is less than 160mm.2,Referring to geological conditions of static load test and using MIDAS/ GTS software for the numerical analysis, to change some parameters of new type ribbed concrete pipe, and to make an analysis of the influence of these parameters.(i)the effect of diameters of annular flange rib When the load level is smaller, the effect to settlement is not obvious; When the load level is higher, the settlement is relatively small if the diameter of annular flange rib is larger. Under the same load level, the deformation decreases with the increse of diameter of annular flange rib, decreasing amplitude increases.(ii)the effect of annular flange rib pitchWhen the load level is smaller, the effect to settlement is not obvious; When the load level is higher, the deformation increases with the increse of annular flange rib pitch,When annular flange rib pitch is less than 1.5 m, decreasing amplitude is larger. When annular flange rib pitch is larger than 1.5 m, the deformation still increases, but the decreasing amplitude is smaller.(iii)the effect of the under part length of annular flange ribIt is explained that the change of the under part length of annular flange rib of new type ribbed pretressed pipe is no meaning to settlement when it is larger than 160mm. It is suggest the under part length of annular flange rib is less than 160mm in the furture engineering application. When the load level is smaller, the effect to settlement is not obvious with the increase of the under part length of annular flange rib; When the load level is higher, the effect of deformation is more and more obvious with the increase of the under part length of annular flange rib, under the same load level, the deformation decreases with the under part length of annular flange rib, increasing amplitude increases.The conclusion agrees well with the third chapter about calculation formula with the engineering example analysis, further confirms the applicability of the calculation formula.