Model Test And Analysis Of Jacked Tubular Pile In Sand

Due to the safety, environmental protection and the advantage of quick in construction, so it is best to use the jacked pile in engineering. The penetration and load process has a significant influence on stress and density of surrounding soil. In this paper, semi-analytical semi-numerical method and miniature earth pressure gage pile two different model tests and numerical simulation analysis were proposed, to study the properity of pile during penetration and horizontal load period. Main contents conclude:( 1) Develop vertical and horizontal automatic loading system and sand deposition equipmentImprove and develope loading servo device, through the device, the device is controlled by PLC servo loading system, vertical and horizontal load was applied automatically and accurately on the pile. Loading pattern includes: 1) simulate the penetration process by load control and displacement control method; 2) simulate horizontal load applied on pile after penetration; 3) simulate the combination of vertical and horizontal load. A sand deposition equipment was developed, equipment can prepare the sand layer uniformly and repeatably, relation between sand relative density and control parameters was established.( 2) Propose a semi-analytical and semi-numerical method for analysis of model test of jacketed pileThe procedure of proposed semi-analytical and semi-numerical method: use B-spline function to assume the distribution of the pile load, using the finite element method to calculate the sensitive matrix, using model test method to measure the strain of pile, and then calculate skin friction and lateral pressure through analytical method. Propose lateral pressure during penetration and unloading, when penetration depth is large, frictional resistance is positive, when penetration depth is small or in unloading stage, frictional resistance is negative, the frictional resistance is in proportion to lateral pressure.(3)Study the pressure on pile during penetration and horizontal load based on miniature earth pressure gageDevelop a model pile with miniature earth pressure gage embeded in pile wall,calibrate in a chamber to simulate complex load imposed by surrounding soil,derived the nonlinear relation with pressure and gauge output. Test result show that,ratio of end resistance to total resistance is large than 90%, the ratio decreases with the increase of penetration depth, lateral pressure on pile increased with depth;lateral pressure on pile has a peak, and the depth of peak value increased with the increase of horizontal load; earth pressure on dorsal part of pile is very small, when depth is less than 5.5D, earth pressure increased with the increase of depth and horizontal load, when depth is large than 5.5D.( 4) Numerical study of penetration and horizontal load based large deformation theory, CEL explicit integration algorithm and state dependent theoryBased on large deformation theory, using the CEL(coupled Euler- Lagrangian)explicit integration algorithm, derived integral form of expression related to sand state dependency model based on explicitly program of ABAQUS, developed a procedure to simulate penetration and horizontal stage of jacket pile. Result show that, earth pressure concetrate on pile end region, plastic zone and vertical bearing capacity increases with the increase of diameter; friction resistance is negative at initial stage of penetration, with the increase of penetration depth, friction resistance increased, horizontal pressure has a peak value, the depth of peak value increase with the increase of horizontal load.