Research Of Longitudinal Cracks Of Prestressed Concrete Solid Square Pile When The Pile Tip Insert Into The Rock Layers During The Piling Process

Shandong province will build a large number of public buildings and port terminals and other buildings and facilities with the implementation of the Peninsula Blue Economic Zone and other national strategies in the next few years.As a traditional foundation type-the pile foundation,it will be unprecedented demand.The prestressed concrete solid square piles for its high strength,cracking,bending,and good corrosion resistance,strong ability to penetrate into the rock,strong adaptability for geological conditions,etc.are widely used in industrial and civil construction,railway,port,ports,municipal,etc.pile foundation engineering of ground foundation engineering.In this regard,the research group under the leadership of author?s mentor and Qingdao Hao River Cement Products Co.,Ltd.jointly developed a prestressed concrete solid square pile(hereinafter referred to as square piles).It was approved as the standard design atlas of Shandong Province(<The prestressed concrete solid square piles>)(L13SG410).However,there are much crushed stone,fine-grained granite,strongly weathered rock and lamprophyre etc.in earth formation due to the geographical environment influence in Shandong Province.This will led square piles easy to appear longitudinal cracks in the piling construction process,this will seriously affect the stability and the durabilityof of pile foundation,especially for the Shandong peninsula,the harm is unimaginable due to geological conditions with special acidic corrosive media erosion.To solve the above problem,I will use LS-DYNA nonlinear finite element softw are in this paper to research into the causes of the longitudinal cracks in the piling construction process and explore those related square pile design to achieve depth and quality requirements in terms of controlling the longitudinal crack.We get the following conclusions:(1)Thelongitudinal crack in the piling construction process will appear when transverse tensile stress is greater than design value of tensile strength of concrete.(2)The longitudinal cracks will be most likely to appeared in both ends of the pile When the pile tip get to the hard interlayer or supporting stratum.The conical pile tip and pile ferrule and the encrypted spiral stirrup from atlas can be better to limit longitudinal cracks.(3)The effective pre-stress from square pile can offset longitudinal tensile stress that generated during piling so that do not worry the transverse cracks.(4)the cushion with suitable thickness and stiffness can significantly improve the performance of square piles crack resistance in addition to the timely replacement cushion in piling construction.