Study On The Field Test And The Design Calculation Method Of Antislide Pile

Although the use of antislide pile in landslide control engineering has already morethan half a century, but the accurate calculation of it is still a difficult thing that people arehard to do. This is because its design calculation process is complex and relates to theinfluences of many objective factors, such as the reveal of the shapes and positions of slipsurfaces which is correct or not, the values of physical and mechanical parametersespecially the parameters of shear strength of soil in slip zone which are correct or not, thecalculation methods of landslide thrust which are scientific or not, the consideration ofseepage action of groundwater which is reasonable or not, etc. All of them can affect thedifferences between the final design calculation results and real or actual results. So thestudies of the design and calculation of antislide pile and its related problems are still thehot spot problems which are devoted to study by many geotechnical and geologicalengineering scholars at home and abroad. The study jobs of this paper are spread based onabove, the main content is summarized as follows:Firstly, in order to reveal the force and deformation characters of fully embeddedantislide pile under the lateral distributed landslide-thrust and provide dates to comparisonand verification for3D finite element method established by this paper, a large field test ofpushing pile is carried out relying on an engineering antislide pile of landslide control inJindou mountain of Punan highway in Fujian province. The internal forces anddeformations are measured in the test through applying triangle, rectangular, paraboliclateral distributed loads respectively which are used to simulate the possible distributedforms of landslide-thrust on this antislide pile approximately. Meanwhile, the situation ofapplying the horizontal concentrated load on pile top is also made in the test.Secondly, ABAQUS nonlinear finite element soft is used to make3D fininte elementsimulation on the test antislide pile, through the comparative analysis on the calculationdisplacements of fem and the displacements which are caculated by using the actualmeasued moments of test pile section under all kinds of distributed loads to back analyzethe lateral displacements according to finite difference formula, and the reliability of3Dfinite element numerical simulation are verified. Aimed at the problem of the steel bars fixing steel bar meters in test pile not being full length fixed, and the internal forces of pilesection got from finite element calculation results of whole pile which are different fromactual situations, a new method of caculating moments which is using MATAB curvefitting tool to fit the lateral displacement-depth curves of test pile section and calculate thesecond derivatives of fitting results is brought forward. The calculation results of thismethod agree well with actual measured datas. The calculation results also show that itshould considers the effect of pile side wall protection improving antislide potential ofantislide pile.Thirdly, a new method which applies finite element method to back analyze theindexes of shear strength of soil in slip zone is brought forward. This method overcomesthe problem of traditional back-analysis methods based on limit equilibrium theory losingtightness caused by artificial unreasonable assumption. In addition, the shear strength oflandslide which is not exposed slip zone through investigation at critical stable state areback analyzed through the3D soil finite element strength reduction, and the indexes areused to the3D numerical simulation of landslide controlled by antislide piles to obtain thestability of landslide controlled and reveal the distribution rules of internal forces ofantislide piles, pide side earth pressure and pile side friction, and earth pressure of gravityretaining wall at the toe of slope. On the base of above studies, a new method which canmake the whole process design calculation of antislide pile is brought forward, itovercomes the many problems existing in traditional design calculation methods andcurrent numerical simulation methods, and improve the design calculation level of antislidepile controlling landslide.Forthly, a method which uses strength reduction fem of coupling deformation andseepage to analyze the slope or landslide stability under seepage is established, and thecomparations with the traditional Sweden slice method and simplified Bishop methodshow that the method is correct and reasonable. Meanwhile，the influences of thepermeability of soil and the choosing of finite element model borders on the positions ofseepage saturated surfaces and slope stability are studied, and the method is extent to thecoupling analysis of seepage and deformation on landslide system controlled by antislidepile, and the problem of not considering the influence of groundwater existing in current3D numerical simulation of this system is solved.Fifthly, aimed at the problem of current2D plane analysis method unable to realreflect the soil arching between antislide piles, the3D strength reduction fem is used tosimulate the engineering example to reveal the soil arching between antislide piles andobtain the value range of reasonable pile spacing. Finally, the methods brought forward by this paper are applied to the numericalsimulation analysis on landslide controlled by portal antislide rigid frame piles to comparethe stability of landslide in different cases of not considering groundwater and consideringsteady seepage and reveal the distribution rules of internal forces of antislide piles, pideside earth pressure and pile side friction, and earth pressure of gravity retaining wall at thetoe of slope. Meanwhile, the influences of the space of portal antislide rigid frame piles，the section size of the front and back row piles and connecting beam on the internal forcesof portal antislide rigid frame piles are studied, and the results can provide scientific basisto the reasonable design of portal portal antislide rigid frame piles.