Study On Determination Of Brige Pile Foundation Position On High-steep Slope

The construction of high-steep slope bridge is a difficulty in the engineering field,in which the determination of brige pile foundation position is the key in bridge engineering.The determination of brige pile foundation position is not only related to the stability of slope and the safety of bridge,but also related to the cost of engineering items and the difficulty of construction.The finite difference calculation software is used analysing the mechanical characteristics and variation rules of rock mass under the load of piles on high-steep slope,then,the methods of determination of the position of bridge pile foundation on high-steep slope are obtained.The mechanical behavior of rock foundation under piles foundation load,the stress,displacement and stress influence range of rock mass are also analyzed in semi infinite foundation,slope foundation and multi piles slope foundation.The results show that under the load of pile,the stress and displacement of rock mass are affected,and the shape of distribution of stress and displacement of rock mass under pile are bulb-shaped.The stress influence coefficientηof slope surface rock mass increases with the height of slope surface position,and there is a maximumη_max at a certain height,which is different with pile edge distance S and different numbers of piles.It is considered thatηmax is the core of determining of pile foundation position on high-steep slope.The various slope and pile parameters those affected the stress influence coefficient of slope surface rock massη,the stress,displacement andηof rock mass with different parameters are also analyzed.The results show that when slope angle,rock mass quality grade,pile diameter,numbers of piles,pile foundation load increases,the stress and displacement of rock mass,η_max will increase.Those will have adverse effect to the slope stability.When pile spacing and pile edge distance S increase,the stress and displacement of rock mass,η_max will decrease.Those are beneficial to the slope stability.The pile load can only affect the rock mass at a certain depth,beyond the certain depth,the influence of pile load on the stress of rock mass is almost unchanged.Based on the rules between various parameters andη_max,the position of bridge pile edge distance S is obtained as follow:S=0.05126[α^0.93271L_a^-0.11396L_b^-0.33752（1-0.61596^d）（1-0.42927^Ma）（1-0.76832^Mb）N]^1.173k_r^-1.173Take the Dadu River Bridge on Sichuan Tibet railway as an example,the appropriate parameters are selected,the bridge pile foundation position is determined by method of this paper.The rationality of method of this paper is verified.