Research On The Design Of Anti-slide Pile In Wan Zhou City Of Three Gorges Area

The Three Gorges area is one of the regions that landslides are overgrown, and Wanzhoucity is the centrality of landslide in The Three Gorges area. Hydrogeology condition's changewould change and deteriorate landslide's geological environment because of the sluice of threegorges area. So our country has ploughed much money into landslide reconnaissance andtreatment in three gorges area. Anti-slide piles have been widely used in Wanzhou city, paper hascollected a lot of engineering examples in the second and third hazards treatment period inWanzhou city. Based on analysis and experiment of landslide mass and rock physics mechanicalcharacters, the paper emphases on the study of calculation and distribution model of landslidethrust, rock parameters and rock-socketed length, the subgrade retaining coefficient, the ultimatestate calculation and design theory. The study will promote important instruction to the antislidedesign in Wanzhou city. The main research work containing some aspects as following:ⅠStudy on distribution model of landslide thrust on anti-slide pile piles, which concludes:The present design jobs are summarized and the distribution models of landslide thrust arediscussed in this paper. Validation has been done for the equivalence of two different calculationmethods of water pressure, "Code Method" and "Pan Jia-zheng Method" and the explanation ispresented for the reason of the error of "Simplified Pan Jia-zheng Method". The calculationprinciple and processs of thrusting force with Strength Reduction Method of FEM is introduced,and the thrusting force and its distribution, moment and shear amount are obtained by thismethod. Taking Ercengyan landslide as a sample, Limit Equilibrium Method and StrengthReduction Method of FEM are compared through the results of the landslide thrust distributionson the piles and stress fields in the piles, which porve that it is effective to use FEM to calculatethrusting force and simulate its distribution. It is concluded that the distribution forms of thelandslide thrust on piles are trapeziums and different distributions can be obtained when theparameters of slide body changed.ⅡStudy on rock-socketed length of antislide piles, which concludes: A statistic job isaccomplished for physical and mechanical parameters of socket part rock based on the anti-slidepiles of more than twenty landslides. And the characters of the rocks of socket part are analyzedand tests are finished for getting the parameters of the socket part rock of antislide piles. Thelateral allowed bearing capacities is respectively discussed for soils and moderate integratedbedrocks, and the range of it is achieved in this paper for Wan Zhou city. The classification ofrock mass basic quality is given for socket part of antislide piles: The classification of siltymudstone and clay rock basic quality isⅣ-Ⅴ, and The classification of dauk and feldspar silicarenite basic quality isⅢ～Ⅴ.The elasto-plastic model of calculation is discussed for therock and soil around the antislide piles. Based on the analysis of Wu Jia-wan landslides, thecritical height of elasto-plastic area before piles is given when the slipping surface is declining.Subsequently, the relationships between the critical height and slipping surface angle, the resistforce of rock and soil before piles and the strength parameters is discussed. Two differentmethods are presented for the length calculation of the rock-socket section when bedrocks areintensely weathered. Tacking Ercengyan landslide as a sample, the above tow method arecompared, and the calculations of the length of rock-socket fragments are respectively discussedwhen rock-socketed part is in soil layer or half soil and half bedrock or bedrock mixed with softinterlayer.ⅢStudy on the subgrade retaining coefficient of antislide piles, which includes: Thedefinition and experiment methods are introduced for the subgrade retaining coefficient. Theinfluence factors of the coefficient are discussed and some questions are pointed out when theground coefficient table is used. The presumptions of the distributions of the subgrade retainingcoefficient are discussed for antislide piles calculation. Then the stress calculations in theanti-piles for different distributions of subgrade retaining coefficient are presented. The stressesin the antislide piles calculated by different subgrade retaining coefficient method are comparedand a conclusion is drawn that the "m" method is the best choice for the calculation of antislidepiles in Wan Zhou city.ⅣStudy on the ultimate state design theory, which includes that: The differences of the pilebottoms support conditions are discussed and it is pointed out that the rivet presumation for thecondition of pile bottom is not suitable in the design of the landslides in Wan Zhou city. Thefreedom brace condition for the pile bottom can be chosen for the case of gravel soil at thebottom and the gemel condition is more suitable for the bedrock. The differences between rigiditypile and elastic pile are discussed and the elastic pile presumption in the landslide design is morereasonable in the Wan Zhou area based on case studies. Three key questions, the pre-stressingforce, the tension change and loss of pre-stressing force in anchor cable, are researched foranchor, cable pile system used in the reservoir bank landslides. The long-term load is used tocalculate the pre-stressing force of anchor cable and the additional short-term load is undergoneby coordination deformation between landslide and anchor cable. If the pre-stressing in the cableis too high, the antislide pile will suffer an adverse condition. The load effects of antislide pilesare analyzed and three ultimate state equations, bend failure, shear failure and compress brokenaround the bedrock of rock-socket part, are achieved. The three main factors, includingsurrounding loadings, material characters and the geometric parameters, are summarized. And itis pointed out that the most important thing for ultimate state design is the cognition of thefeatures of soil and rock around the rock-socket part, which includes ground coefficients, uniaxialcompressive strength, rock mass structure, fractures of bedrock, weathering and softendegree,etc.