Study On Vertical Bearing Mechanism And Influencing Factors Of Rock-socketed Piles

With the constant advancement of modernization,the requirements for infrastructure construction have become more stringent.With the advantages of high bearing capacity,simple construction,small settlement and weak pile group effect,the rock-socketed piles are widely used in infrastructure construction.However,there are still many deficiencies in the study of rock-socketed piles,such as field test of rock-socketed piles,constitutive relation of pile-soil and rock,and the calculation of ultimate bearing capacity.The static load test of pile is the most direct and effective method to test the bearing performance of pile and to determine the bearing capacity of single pile.And in this paper,the vertical bearing mechanism and bearing capacity of single pile of rock-socketed piles are studied through the method of combining the vertical static load test on single pile of rock-socketed piles with FLAC3 D software numerical simulation.The specific work mainly includes:(1)Comprehensively collate the test data of rock-socketed piles under different geological conditions,study the vertical load transfer mechanism of rock-socketed piles,and explore the influence of various design parameters on the bearing capacity of rock-socketed piles.(2)According to the load transfer mechanism of rock-socketed piles,the mechanism,calculation model and influencing factors of the lateral resistance of pile-soil,the lateral resistance of pile-rock and pile-end resistance are analyzed,and then the requirements of vertical bearing capacity of rock-socketed piles are met through controlling the strength of pile materials,rock-socketing ratio,long-diameter ratio and the sediment of pile bottom.And various methods for determining the vertical bearing capacity of rock-socketed piles are analyzed in depth.(3)Taking a residential building as the engineering background,the vertical static load test on single pile of rock-socketed piles is conducted,the trial data are compiled to draw the Q-S curve of test pile.And the vertical ultimate bearing capacity of each test pile can be determined by measuring the settlement value of pile top.(4)The FLAC3 D finite difference software is used to numerically simulate the foundation piles of a residential building,and the distribution curves of the lateral friction resistance of pile,pile-end resistance and axial force of pile body are obtained,and the vertical ultimate bearing capacity of test pile is proposed.Comparing theFLAC3 D numerical analysis results with the field test results,the applicability,rationality and reliability of the model can be discussed and the feasibility of FLAC3 D software numerical simulation analysis method can also be verified.(5)By changing different designs to influence parameters,such as rock strength(modulus),rock-socketed depth and pile diameter,a new model of pile and geotechnical numerical analysis is re-established.According to the results of numerical simulation,it is concluded that as the rock strength decreases,the displacement at the top of pile increases obviously;and as the depth of rock-socketing increases,the proportion of vertical load on the lateral frictional resistance of pile-sock also increases.When the depth of rock-socketing reaches to 3D(D is the pile diameter),the lateral frictional resistance of pile-rock and pile-soil are almost completely loaded,and the end-resistance ratio is extremely small.Therefore,the reasonable rock-socketed depth of rock-socketed piles for this engineering geological is 3D(D is the pile diameter).