桩基静载试验新方法及在高铁桥梁大直径PHC管桩中的应用OA

In weak soil areas,large-diameter PHC pipe piles for high-speed railway bridges exhibit high bearing capacity,which needs large test loads in vertical static load tests.However,traditional methods such as the Kentledge method,the anchor pile method,and the O-cell method each have significant limitations,such as insufficient safety,poor economic efficiency,or discrepancies between their bearing mechanisms and engineering reality.To address these shortcomings,a new method using pile group and pile cap to jointly provide reaction forces(refer to as the PGCPT method)was proposed and applied in static load tests on large-diameter PHC pipe piles for high-speed railway bridges.Based on the tests,key construction technology in the application of pipe piles was proposed,and the bearing behavior and deformation characteristics of large-diameter PHC pipe piles in typical silt and silty sand areas of the Yellow River Plain were analyzed.The results are as follows.1)The installation process of PGCPT method is simple and efficient,especially suitable for static load tests on large-diameter pipe piles in weak ground foundations,which effectively reduces costs and improves safety.2)The load-settlement curve of the test pile is"steep drop"type.Under the maximum load,the pile tip displays a penetrative failure mode with the continuous settlement over time.The allowable compressive capacity reaches 9 000 kN.3)The distribution patten of pile side resistance changes from an"inverted triangle"to a"single-peak"and then to a"double-peak"with the increase of load,exhibiting a trend similar to the distribution of blows per meter during pile driving.The maximum pile side resistance occurs in the middle silty sand layer.4)The pile side and pile tip load transfer functions are characterized by hyperbolic and bilinear models,respectively.Under the design and ultimate loads,the pile shows the characteristics of friction pile and end-bearing friction pile,respectively.The test results validate the reliability and superiority of the PGCPT method,which can provide important reference for the design and construction.