Nonlinear calculating method of pile settlement

Abstract

To study calculating method of settlement on top of extra-long large-diameter pile, the relevant research results were summarized. The hyperbola model, a nonlinear load transfer function, was introduced to establish the basic differential equation with load transfer method. Assumed that the displacement of pile shaft was the high order power series of buried depth, through merging the same orthometric items and arranging the relevant coefficients, the solution which could take the nonlinear pile-soil interaction and stratum properties of soil into account was solved by power series. On the basis of the solution, by determining the load transfer depth with criterion of settlement on pile tip, the method by making boundary conditions compatible was advised to solve the load— settlement curve of pile. The relevant flow chart and mathematic expressions of boundary conditions were also listed. Lastly, the load transfer methods based on both two-broken-line model and hyperbola model were applied to analyzing a real project. The related coefficients of fitting curves by hyperbola were not less than 0.96, which shows that the hyperbola model is truthfulness, and is propitious to avoid personal error. The calculating value of load—settlement curve agrees well with the measured one, which indicates that it can be applied in engineering practice and making the theory that limits the design bearing capacity by settlement on pile top comes true.

Keywords

pile engineering / settlement / nonlinear / load transfer method / hyperbola model

References

[1] ZhaoM.-h., ZouX.-j., LiuQ.-jian.. Loading test on the vertical bearing capacity of super-long and large-diameter bored piles in the soft soil area of Dongting lake[J]. China Civil Engineering Journal, 2004, 37(10): 63-67

[2] HaldarS., Sivakumar BabuG. L.. Load resistance factor design of axially loaded pile based on load test results[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2008, 134(8): 1106-1117

[3] ZhangL. M., WangH.. Development of residual forces in long driven piles in weathered soils[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2007, 133(10): 1216-1228

[4] ZhangL. M., NgC. W. W., ChanF.. Termination criteria for jacked pile construction and load transfer in weathered soils[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2006, 132(7): 819-829

[5] ZhangL. M., EricY. W. W.. Centrifuge modeling of large-diameter bored pile groups with defects[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2007, 133(9): 1091-1101

[6] ZhangL. M., XuY., TangW. H.. Calibration of models for pile settlement analysis using 64 field load tests[J]. Canadian Geotechnical Journal, 2008, 45(1): 59-73

[7] AlawnehA. S.. Modeling load-displacement response of driven piles in cohesionless soils under tensile loading[J]. Computers and Geotechnics, 2005, 32(11): 578-586

[8] SeolH., JeongS., ChoC.. Shear load transfer for rock-socketed drilled shafts based on borehole roughness and geological strength index(GSI) [J]. International Journal of Rock Mechanics and Mining Sciences, 2008, 45(6): 848-861

[9] SeedH. B., ReeseL. C.. The action of soft clay along friction piles[J]. Trans ASCE, 1957, 122: 731-754

[10] KraftL. M., RayR. P., KagawaT.. Theoretical t—z curves[J]. Journal of the Geotechnical Engineering Division. ASCE, 1981, 107(3): 1465-1488

[11] CloughG. W., DuncanJ. M.. Finite element analysis of retaining wall behavior[J]. Journal of the Soil Mechanics and Foundations Division, ASCE, 1971, 97(12): 1657-1674

[12] HuL.-m., PuJ.-liu.. Experimental study on mechanical characteristics of soil-structure interface[J]. Chinese Journal of Geotechnical Engineering, 2001, 23: 431-435

[13] CaoH.-zhi.. The axial load transfer of pile and numerical calculating method of load-settlement curve[J]. Chinese Journal of Geotechnical Engineering, 1986, 8(6): 37-48