| The load mechanics and analysis method for higher pile-column bridge pier structural system are of new tasks faced by highway transportation construction in western mountainous areas. For the complexity of alpine (coteau) terrain and various of loading condition and working condition, the bearing mechanism, deformation analysis and stability calculation methods of high pile-column bridge pier structural system are all deficient for further study. Therefore, it is significative in theoretical analysis and engineering practice to master its bearing mechanism, mechanical characteristics and analysis method comprehensively for rational design of this system. In this paper, combined with the supports of the program of National Natural Science Foundation "study on the buckling mechanism for pile foundation with high pile-cap based on meshless method"(50378036) and the scientific project of Communications Department of Hunan Province "study on the bearing mechanism and optimization design for piles foundation with high bridge piers in mountainous district"(200513), the load mechanics and analysis method of higher pile-column bridge pier structural system were researched and discussed in order to enrich its design and calculation theory based on theoretical analysis, numerical simulation and model experiment.Firstly, based on comprehensive analysis of the domestic and overseas related references, the engineering characteristics and its mass methods to distinguish weathering zones were analyzed by introducing rock masses structure control theory , a quantization expression is established for rock masses around the higher pile-column bridge pier structural system. With analysis and summary of the slope-stability analysis methods, a method about multilevel fuzzy comprehensive evaluation is introduced to evaluate rock slop around higher pile-column bridge pier structural system by considering its uncertain factors. According to the stress characteristics of higher pile-column bridge pier structural system, the bearing behavior and loading mechanism of higher pile-column bridge pier were discussed and the analytical thought was used for references which includes stress and deformation of conventional pile in the plain under loads, the externality loads include axial loads, horizontal loads, lateral distribution thrust forces and resistances from pile side rock. With the distribution of resistances and thrust forces simplified and the calculation model of higher pile-column bridge pier structural system established, the internal force calculation method of higher pile-column bridge pier structural system is deducted with power series method applied and the relevant computer program is developed.Secondly, on the basis of analyzing stability calculating theory and load calculation method of pile ,according to the nonlinearity and abruptness features of higher pile-column bridge pier, a mechanical model is set up by synthetically analyzing the higher pile-column bridge pier. Based on the catastrophe theory, the cusp catastrophe model of higher pile-column bridge pier is established by the determination of its potential function and bifurcation set equation, the necessary instability conditions of high pile-column bridge pier are deduced, and the determination method for column-buckling and lateral displacement of higher pile-column bridge pier are derived. In accordance with the problem of karst development under pile , according to the abruptness and fuzziness features of cave roof , the determining methods of safe thickness of cave roof under high pile-column bridge pier and load-bearing capacity of high pile-column bridge pier are proposed and the new stability evaluation method for cave roof under pile tip in karsts region is established by combining introducing catastrophe theory and fuzzy analysis with fuzzy subordinate function and catastrophe progression.In order to further study on bearing mechanism and load characterize of higher pile-column bridge pier structural system, combining practical projects and with the aid of nonlinear finite element analysis software, based on considering nonlinear factors including discontinuous deformation between pile and rock contact area, the three-dimensional elastoplastic model for single-row double pile of higher pile-column bridge pier structural is established, and the stress distribution is obtain according to different characteristic in different construction stage. The stress characteristic is achieved under different load condition through calculation and the stability influence factors are also fully discussed, so the bearing mechanism of higher pile-column bridge pier structural system is more profound understand.Then, using nondeterminism analysis method, at the based of summering reliability basic theory and present reliability assessment method, aiming at the limits of present reliability analysis method, the improved response surface method of higher pile-column bridge pier structural system is presented for reliability calculation by introducing response surface method. Basing on the interval feature of higher pile-column bridge pier structural system mechanic parameters, interval theory and non-probabilistic thought are introduced to build up non-probabilistic reliability analysis method of higher pile-column bridge pier structural system in which uncertain geotechnical mechanic parameters is viewed as interval variable. Thus, the more whole nondeterminism analysis method of higher pile-column bridge pier structural system is formed.At last, laboratory model tests on high pile-column bridge piers are carried out, it totally includes two parts. The first part is about bearing characteristic experiment , four groups of model piles tests are carried out. The influence factors of pile foundation are researched with different load mode, different pile shaft free length, different pile shaft fixity depth and different slope angle etc. The bearing mechanism and load characteristics of higher pile-column bridge pier structural system are further deepened. The second one is about the failure and instability experiments of higher pile-column bridge piers, the buckling working behavior of higher pile-column bridge piers is studied by taking into account of the different factors of pier-pile length ratio, boundary condition and material stiffness, buckling failure mechanism and loads of higher pile-column bridge piers are gained. The theoretical and experimental results show that the theoretical calculating values agree well with the experimental ones and the rationality and engineering reference value of the method in the paper is verified and displayed.
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