Research On Bearing Mechanism And Design Method Of Rocksocketed Pile Foundation Of Viaduct On Steep Slope

Due to development of economic construction in the western region of China,the infrastructure needs to be improved urgently.Pile foundation is what a foundation form is used wildly while building the viaducts in mountainous areas.However,the design of the structures in the western region is different from those in the eastern region,for the western region terrain is complex.While relevant researches on pile foundations on flat ground have been carried out thoroughly,the analysis and design methods of pile foundations on steep slopes still need to be further researched urgently.This paper proposes the methods of analysis and calculation for the single and double pile foundations on steep slopes,based on the existing research by theoretical analysis,numerical simulation,and field engineering example.The design methods for doublepile foundations on steep slope are also given combined with the engineering cases.The procedures are as follows:The bearing mechanism of a single pile foundation on steep slope has been studied at first.On the basis of the models of calculation and analysis of previous,a finite difference solution based on the collocation methods with higher accuracy and strength applicability than previous solutions is illustrated,and the correctness of the solution is verified.Then,the correctness of the adopted calculational and analytical model is also verified by combining the horizontal static load test of a single pile on a steep slope reported in the literature with the numerical simulation method.The improving 8)-method was introduced to optimize the model on the basis of the engineering experiments.The susceptibility-analyses of the single pile foundation have been carried out.The result show that the slope gradient will greatly affect the 8)value of the gravel soil foundation,and the growth of slope gradient will lead to the nonlinear increasement of the displacement of the pile top and the internal force of the pile body.The corresponding anti-sliding measures should be taken for steep slope which could be excessive.Secondly,researches on the bearing mechanism and design methods of the double-pile foundation on steep slope have been done.The calculation-model of the cross-slope doublepile foundation has been established at the beginning of this research,the model and solution are verified with engineering cases which had been reported in the literature.The susceptibilityanalyses shows that for the cross-slope double-pile foundation,the connecting beam on pile top can effectively adjust the internal force of the pile,while the pile spacing has little effect on the displacement and internal force of the cross-slope double-pile foundation in this model case.The pile diameter and 8)value still control the internal force of the pile foundation.In addition,for the first time the relevant researches of anti-slide piles are used to propose a calculationmodel of through-slope double-pile foundation under the thrust of the sliding-slope.The design method considered both the safety of the slope and piles is illustrated.The calculation method of the design load of the through-slope double-pile foundation is proposed.This paper summarizes the design method of both the cross-slope and through-slope double-pile foundation.Finally,the bearing capacity of two double-pile foundations,which are originally designed for a viaduct in the mountainous area of Sichuan,have been checked by using the method developed above.The results suggest that the steep slope pile foundation should be carefully considered in the design,for some unfavorable factors will challenge the bearing capacity of the pile,such as the designed horizontal load,the large design bending moment of the pile top,and the reduction of horizontal resistance.