往复位移作用下整体桥台后土压力计算方法

整体桥具有使用寿命长、施工方便、造价及养护费用低等特点,目前在国内外得到了广泛应用与推广,但是,其台后土压力计算方法还缺乏深入研究。为此,以永春上坂大桥整体桥为设计背景,开展了整体式桥台-H形钢桩-土相互作用的低周往复荷载拟静力试验研究,主要研究了台后土压力大小及其衰减规律,并给出了桥台内力和台后土压力计算方法。研究结果表明：台后土压力与正向加载位移成非线性关系,且随着正向加载位移的增大而增大;台后土压力沿深度方向主要呈"三角形"与"梯形"分布,同时,台背处土压力合力作用点基本位于2/3桥台高度的埋深位置处;台后土压力沿纵桥向成指数衰减,且在台后2倍的桥台高度处基本衰减为0,即温度作用下整体桥桥台的纵向移动仅对台后2倍桥台高度范围内的土体有影响。现有研究及规范给出的方法不适用于整体桥的台后土压力计算,而所提出的台后土压力计算方法与试验、实桥监测结果较为吻合,其可为整体桥的设计及规范的制定提供参考与借鉴。

Method to Calculate Earth Pressure of Backfill of Integral Abutment Bridges Under the Action of Reciprocating Longitudinal Displacement

The integral abutment jointless bridge (IAJB) has many desirable characteristics such as long service life, convenient construction, and low building and maintenance costs. It has thus been widely used and applied both in China and worldwide. However, the method to calculate the earth pressure of the backfill behind an integral abutment requires further investigation. Therefore, considering an integral abutment bridge in China, a reciprocating low-cycle pseudo-static test was carried out to determine the integral abutment-H-shaped steel pile-soil interaction. The mechanical behavior and decaying law of the earth pressure behind the abutment were evaluated, and methods to calculate the abutment internal force and earth pressure coefficient were proposed. The results show that a nonlinear relationship exists between the earth pressure behind the abutment and the loading displacement for the longitudinal forward-abutment direction; furthermore, the earth pressure increases with the increase in the loading displacement of the forward-abutment. The earth pressure behind the abutment exhibits primarily triangular and trapezoidal distributions along the depth direction. Meanwhile, the position of the resultant force for the abutment is located at a depth of two-thirds the height of abutment. It was also noted that the earth pressure is exponentially attenuated along the longitudinal bridge and decreases to nearly zero at an abutment height of two times that behind the abutment. This means that the longitudinal movement of the abutment of the IAJB, under the effect of temperature, affects only the backfill of the abutment within the range of two times the abutment height. The calculation shows that the methods recommended by the specification are not appropriate for the calculation of the earth pressure of the IAJB. The results obtained using the proposed method to calculate the earth pressure behind the abutment demonstrate good agreement with the test and the bridge monitoring results, and the proposed method can thus be used as a reference for the design of IAJB and the formulation of the specification.