竖向加卸载下邻近双端约束倾斜桩侧移规律试验研究

Experimental Study on Lateral Displacement Rule of Adjacent Inclined Pile with Both Ends Constrained under Vertical Loading and Unloading

深厚软基上修建高路堤时,路基经常发生不均匀沉降、滑移甚至垮塌,必须探索有效控制措施。基于倾斜桩和竖直桩工程特性,提出在坡脚设置倾斜桩、桩顶部设置连梁方案。采用室内模型试验,对承压板进行3次循环加卸载,测试承压板侧面处顶端设置连梁、底端约束的倾斜双排桩的水平位移,研究高路堤荷载作用下坡脚倾斜桩水平位移变化规律。结果表明:加载过程中,桩顶和桩身水平位移均随地基侧向荷载增加而增长,增长率随加载次数增加而降低;第2次加载超过首次加载最大压力时,加载曲线沿第1次加载曲线的延长线发展,水平位移随着荷载的增大继续增加;卸载的初、中期,桩身的回弹变形均不敏感,卸载到0时才产生明显的回弹变形,说明加载所产生的变形均主要为塑性变形;桩顶与桩底回弹量均小于桩身中部,说明桩顶连梁、桩底约束嵌固约束了水平位移;地基侧向荷载一定时,在0°~9°范围内,桩顶和桩身水平位移均随倾斜角增加而减小;相同荷载作用下,负斜桩顶侧移小于竖直桩,与负斜桩主动承受桩顶水平荷载作用下桩顶水平位移大于直桩相反;实际工程中,坡脚桩采用底部嵌岩、顶部设置连梁的倾斜桩,更有利于抵抗滑移。

When high embankment is built on deep soft foundation,the differential settlement,slippage and even collapse often occur in subgrade,effective control measure must be explored.Based on the engineering characteristics of inclined pile and vertical pile,the scheme of setting inclined pile at the foot of the slope and connecting beam at the top of the inclined pile is put forward.By indoor model test,with 3 loading and unloading of the bearing plate,the horizontal displacement of the inclined double row piles with top setting beam and bottom constraint at the side of the bearing plate is tested,and the horizontal displacement change rule of the inclined pile at slope foot under the high embankment load is studied.The result shows that(1)The horizontal displacements of pile top and pile body increase with the increase of lateral load of subgrade during loading,and the growth rate decreases with the increase of loading times;(2)when the second loading exceeds the maximum loading for the first time,the loading curve develops along the extension line of the first loading curve,and the horizontal displacement increases with the increase of the load;(3)the rebound deformation of the pile is not sensitive at the initial and middle stages of unloading,and the apparent rebound deformation is produced when unloading to 0,indicating that the deformation produced by the loading is mainly plastic deformation;(4)the resiliences of pile top and pile bottom are smaller than that of middle pile body,which indicates that horizontal displacement is restrained by pile top beam and pile bottom constraint embedment;(5)when the lateral load of subgrade is constant,the horizontal displacements of pile top and pile body decrease with the increase of inclination angle in the range of 0°~9°;(6)under the same load,the lateral displacement of the top of the negative inclined pile is smaller than that of the vertical pile,opposites to that the horizontal displacement of the pile top is greater than that of the vertical pile when the negative inclined pile actively bearing the horizontal load on pile top;(7)in practical engineering,the measure of the slope foot pile adopts inclined pile with rock socketed at the bottom and connecting beam at the top is more favorable for resisting sliding.