人工挖孔抗滑桩护壁与桩身结构相互作用模型试验

为研究护壁结构对抗滑桩水平承载力的贡献,以某人工挖孔抗滑桩工程为背景,依据相似理论设计了1∶10的分段式护壁结构、整体式桩身结构模型,并通过2个MTS作动器分别同时施加水平位移荷载于条件完全相同的有护壁桩和无护壁桩桩顶,开展室内物理模型试验研究.结果表明:相同桩顶水平位移条件下,有护壁桩桩端土压力要大于无护壁桩桩端土压力,顶部桩前被动土压力要小于无护壁桩,加固柔性桩上部被动区土能更有效提高其水平承载能力.相同桩顶水平位移下,有护壁桩桩身受拉钢筋最大应变始终大于无护壁桩;随着桩顶水平位移的增加,桩身受拉钢筋最大应变截面逐渐下移,但有护壁桩下移滞后于无护壁桩;随着水平荷载的增加,有护壁桩桩身受拉钢筋最大应变增大比例先增加后减小,当桩顶水平位移为30 mm时达到最大,增大比例为165.03％,当桩顶水平位移为90mm时达到最小,增大比例为20.23％.若以桩顶水平位移为桩的水平承载力控制标准,试验护壁提高桩身水平承载力达20％以上,工程实践中可参考所提公式和折减系数来计算护壁对桩身水平承载力的贡献.

Model test of interaction between the segmental protection-wall and the Integral pile structure of artificial drilled anti-slide pile

Based on artificial drilled anti-slide pile, the model structure of segmental protection-wall and integral pile was designed on the similarity theory. With two same actuators of MTS respectively loading horizontally on the top of pile with protection-wall and of pile with no protection-wall, a model test with the scale of 1:10 was carried out to study the interaction of segmental protection-wall and integral pile structure of anti-slide pile under horizontal load. By simultaneously loading horizontally of MTS actuators, results are achieved as follow. Firstly, with the same horizontal displacement of pile top, the earth pressure at the bottom of pile with segmental protection-wall was larger than that of pile with no protection-wall, but the passive soil resistance on the top of pile was reverse, and reinforcing of upper passive soil of flexible pile could improve the horizontal bearing capacity. Secondly, with the same horizontal displacement of pile top, the maximum strain of tensile steel bar of pile structure with segmental protection-wall was always larger than that of pile with no protection-wall. With the increase of horizontal displacement of pile top, the section position of maximum strain of tensile steel bar of pile was moving down, but the moving velocity of pile with protection-wall laged behind that of pile with no protection-wall. Furthermore, with the increase of horizontal load, the proportion of maximum strain of tensile steel bar with protection-wall than that of with no protection-wall increased first and then decreased, and the maximum proportion was 165.03% with the horizontal displacement of 30mm and the minimum proportion was 20.23% with the horizontal displacement of 90mm. Thirdly, with the horizontal displacement of pile top as the control standard of horizontal bearing capacity of pile, the horizontal bearing capacity of test pile in this paper increased more than 20%, and in the pile practice, the contribution of horizontal bearing capacity improvement of segmental protection-wall could be considered with the size of pile structure and the segmental protection-wall structure.