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采用模型试验的方法研究了砂土地基中基坑开挖对抗拔桩极限承载力的影响,试验过程中考虑了基坑开挖直径、开挖深度及坑底以下有效桩长不同的情况,共进行19组试验。试验结果表明:开挖深度相同时,基坑开挖直径越大,抗拔桩极限承载力下降越多,开挖直径为30 cm(10d)时,抗拔桩极限承载力较开挖前有明显下降,随着开挖直径的继续增加,极限承载力继续下降,但下降幅度逐渐减小,并趋于一个稳定值;开挖深度相同时,坑底以下有效桩长越短,开挖后抗拔桩极限承载力损失比例越大;开挖卸荷后坑内土体处于超固结状态,抗拔桩极限承载力大于土体为正常固结状态时,开挖深度相同时,坑底以下抗拔桩长度越短,开挖后桩周土体超固结比越大,抗拔桩极限承载力与土体正常固结状态相比增加比例越大;坑底以下有效桩长相同时,开挖深度越大,开挖后桩周土体超固结比越大,抗拔桩极限承载力也越大。
The influence of the excavation of foundation pit on the ultimate bearing capacity of anti-pull piles in sandy soil foundation was studied by using the model test. The excavation diameter, excavation depth and effective pile length under pit bottom were taken into account during the test. Nineteen experiments were conducted. The results show that when the excavation depth is the same, the larger the excavation diameter is, the more the ultimate bearing capacity of the pile will drop. When the excavation diameter is 30 cm (10 d), the ultimate bearing capacity of the pile is higher than that before excavation With the excavation diameter continues to increase, the ultimate bearing capacity continues to decline, but the decline decreased gradually and tends to a stable value; excavation depth is the same, the shorter effective pile length below the pit bottom, after excavation The greater the ultimate bearing capacity of anti-pull pile loss ratio; excavation unloading soil after overconsolidation state, the ultimate bearing capacity of pile is greater than the soil when the soil is normal consolidation state, the same excavation depth, below the pit The shorter the length of the anti-pull pile, the greater the over-consolidation ratio of the soil around the pile after excavation, the larger the ultimate bearing capacity of anti-pull pile increases with the normal consolidated state of the soil. When the effective pile length below the bottom of the pit is the same, The greater the digging depth, the greater the excess consolidation ratio of the soil around the pile after excavation, the greater the ultimate bearing capacity of the pile will be.