The Analysis On The Lateral Load-bearing Characteristics Of Bridge Pile Foundation In The Loess Gully Area

In the highway construction through the loess area, bridge structure is usually used to cross gully terrain, and many bridge piles are located in loess gully slope. Because of pile lateral soil lacking in the gully, pile lateral bearing capacity is reduced. Therefore, to ensure the rational design of bridge pile foundation, the construction security and economy and the bridge operation safety after completion, it is necessary to further study bearing behavior of bridge pile foundation under lateral load in loess gully region.In this paper, based on Xi’an-Shangzhou highway construction project in Shanghai-Shaanxi line, using numerical calculation, the lateral bearing behavior of bridge pile foundation was analyzed in loess gully region of different slope gradient, pile length, pile diameter and pile’s distance with 90 degrees slope, conclusions was drew as the following:(1) The effect of pile lateral bearing capacity increased with the increase of slope gradient, 60 degrees is the critical slope gradient between general loess gully slope and extremely steep loess gully slope; pile lateral bearing capacity could be improved by increasing pile length, but when pile length grew up to 30 m, this method was not applicable.The pile foundation of pile diameter greater than 1.8m had a better mechanical property.When slope gradient was 90 degrees, pile’s distance with 90 degrees slope should be at least greater than 2.5D.(2) The ratio of pile length to diameter was proposed to determine the mechanical properties of bridge pile foundation in loess gully region. When the ratio of pile length to diameter(L/D) was less than 10, pile foundation showed mechanical properties of rigid short pile; When the ratio of pile length to diameter(L/D) was more than 10 and less than 12.5, pile foundation showed mechanical properties of elastic middle-long pile; when the ratio of pile length to diameter(L/D) was more than 12.5, pile foundation showed mechanical properties of elastic long pile.(3) The effective length of bridge pile foundation and loess gully slope gradient was closely related in loess gully region. According to different slope gradient, pile length reduction was considered in the design calculation, the reduction part of pile length provided a smaller lateral soil resistance, which was negligible.(4) With the increase of the distance from the top of the slope, the pile lateral slope soil horizontal displacement decreases and the displacement of the toe at the level of soil close to zero; As the slope increases, the horizontal displacement of pile lateral shallow soil in slope increased, and the change of horizontal displacement of pile lateral deep soil was really quite negligible.This Paper Research provide a theoretical basis for the bridge pile foundation design calculation in the loess gully region, further improve the pile foundation design theory and guide the practical engineering construction.