悬臂排桩支护基坑沿长度方向连续破坏的机理试验研究  

Experimental study on mechanism of progressive collapse along length of excavation retained by cantilever contiguous piles

作　　者：程雪松[1,2] 郑刚[1,2] 黄天明[1,2] 邓楚涵[1,2] 聂东清 刘杰[1,2] 

机构地区：[1]天津大学滨海土木工程结构与安全教育部重点实验室,天津300072 [2]天津大学土木工程系,天津300072

出　　处：《岩土工程学报》2016年第9期1640-1649,共10页Chinese Journal of Geotechnical Engineering

基　　金：国家科技支撑计划课题项目(2012BAJ01B02-03);中国博士后科学基金项目(2014M561186)

摘　　要：大长度基坑发生了一些沿长度方向上由局部破坏引发数10 m至100 m以上的连续破坏事故,然而基坑连续破坏的发生及终止机理却少有研究。设计了悬臂排桩支护基坑局部支护桩破坏倒塌的模型试验,对局部破坏引发的土压力和支护结构内力变化等规律等进行了研究,在此基础上进行了局部破坏引发支护桩连续破坏的试验。结果表明,基坑局部垮塌会引起邻近桩的土压力和桩身内力瞬间增大,随后坑外土体滑塌进基坑内,造成邻近支护结构主动区卸载,但此卸荷过程相对滞后。当局部垮塌引发的荷载传递系数大于邻近桩的承载力安全系数时,将会导致基坑连续破坏。连续破坏发生后,随着破坏范围增大,土体滑塌引发的卸荷使得土拱效应不足以继续导致支护桩出现破坏时,连续破坏将自然终止。试验还表明,在一定局部破坏长度范围内,局部垮塌长度越大,荷载传递系数和影响范围越大;围护桩嵌固深度越小,即支护桩抗侧移刚度越低时,荷载传递系数越小,但局部破坏影响范围较大。Progressive collapse of deep excavations along the longitudinal direction induced by partial failure may extend to tens of meters or even more than one hundred meters. However, the researches on the initiation and termination mechanism of progressive collapse are limited. The model tests on partial collapse caused by the breakage of some retaining piles are designed. The changing rules of earth pressures and internal forces of adjacent piles are analyzed. Furthermore, the model tests on progressive collapse induced by partial collapse are conducted. The test results show that the partial collapse can cause sudden increase of earth pressures and structural internal forces of adjacent piles. Afterwards, the soil outside the excavation flows into the excavation, which is an unloading effect for the adjacent piles. However, the unloading effect lags behind the loading effect. If the load transfer coefficient of partial collapse is larger than the safety factor of bearing capacity of the adjacent piles, the progressive collapse will occur. During the process of progressive collapse, when the soil arching effect is mitigated by the unloading effect and cannot cause further breakage of the retaining structures, the progressive collapse ceases naturally. Within a certain extent, the larger the partial collapse is, the larger the load transfer coefficient and the influenced area are. Additionally, when the lateral stiffness of piles is low, the load transfer coefficient will be small, but the influenced area will be large.

关 键 词：基坑 排桩 连续破坏 局部垮塌 荷载传递 

分 类 号：TU473[建筑科学—结构工程]