山区高陡横坡段桥梁桩基承载机理模型试验

Load-bearing Mechanism Model Test for Bridge Pile Foundation in High-steep Transverse Slope

以现场工程为原型,设计了45°,60°,75°三种不同陡坡下高陡横坡段桥梁桩基的室内模型承载试验。通过对承载过程中桩顶位移、桩身内力及桩侧土压力等的全程测量,对竖向及水平向荷载作用下桩基的荷载传递规律、内力分布规律及桩侧土压力分布规律进行了研究。结果表明:竖向荷载下高陡横坡段桥梁桩基承载力由桩侧摩阻力与桩端阻力组成,但由于临空面存在,靠边坡一侧桩侧摩阻力传递深度更大,且该效应随边坡坡度的增加而增大;水平向荷载作用下,桩基桩顶水平位移随边坡坡度增加而增大,而内力分布规律与平地桩基类似,即存在最大弯矩及反弯点,但最大弯矩随边坡坡度的增加明显增大,反弯点位置则随坡度增加而有所下移;不同荷载及坡度情况下,后桩桩侧压力随深度均呈现先增大后减小的基本规律,而前桩桩前土抗力则随深度逐渐衰减。

With the site project as the prototype, indoor model of load-bearing test was designed for three kinds of bridge pile foundations in the high-steep transverse slope which was 45°, 60° and 75° respectively. Through the monitoring of the top displacement of pile,internal force of pile body and soil pressure around the pile, the load transferring law, the distribution law of the internal force and the soil pressure around pile under the vertical and horizontal load were studied. The results show that the pile bearing capacity under the vertical load consists of the friction around pile and the resistance of pile tip, but the friction around the pile which is close to free face is transferred more deeply because of the free face, and the effect increases with the angle of slope increasing. The horizontal displacement of pile top under the horizontal load increases with the angle of slope increasing, but the distribution law of its internal force is the same as that of pile foundation in the ground, which means that there are maximum bending moment and inflection point, but the maximum bending moment increases significantly with the angle of slope increasing, and the position of inflection point descends slightly with the angle of slope increasing. In different cases of load and angle of slope, the soil pressure of the back pile increases first and then decreases, but the soil resistance of the front pile decreases gradually withthe depth.