砂土场地中组合荷载下单桩竖向承载特性研究

Model Tests on Vertical Bearing Behavior of Single Pile Under Combined Loads in Sandy Ground

摘要:

考虑砂土场地中单桩承受水平和弯矩荷载的共同影响，完成了五组共十根单桩的室内模型试验，分析了在组合荷载作用下砂土中单桩的竖向承载特性.研究表明：在不考虑竖向荷载作用的情况下，随着水平荷载作用点高度的增加，由于出现了弯矩荷载，单桩的水平极限承载力降低，但降低幅度逐渐减小；水平或弯矩荷载的增大，均会导致单桩沉降的增大和竖向承载力的降低，但只有当水平荷载达到相应位置水平极限承载力的0.5倍以上时，这种变化幅度才较明显；预先施加的水平和弯矩荷载在产生水平位移后，再施加竖向荷载，将会出现PΔ效应，造成单桩水平位移的增大和水平承载力的降低；水平和弯矩荷载共同作用时对单桩的沉降和桩端阻力的影响程度，与水平和弯矩荷载产生的桩顶水平位移的大小正相关.

关键词:砂土场地; 水平荷载; 弯矩荷载; 模型试验; 竖向承载特性

Abstract:

Based on five groups of tenpile indoor model test, considering the influence of lateral load size and its loading position, the vertical bearing capacity of the single pile under combined loads in sandy ground are studied. The results of model test show that without regard to vertical load, horizontal ultimate bearing capacity decreases of the single pile with the height of the point of application by lateral load apart from the ground increases, while its magnitude is reduced gradually. The settlement of pile top increases and vertical bearing capacity decreases with the increases of the preapplied lateral or moment loads of the single pile, and its effect on the magnitude is dependent on the lateral load. The vertical load produced a PΔ effect when it was applied after the lateral and moment loads, which causes the horizontal displacement increases and the ultimate horizontal bear capacity of the single pile decreases. The experiment data indicate that the horizontal displacement at the top of pile is positively associated with settling volume of single pile, tip resistance of pile.

Key words:sandy ground; lateral load; moment load; model test; vertical bearing behavior