路堤荷载下刚柔长短桩复合地基承载特性研究

发布时间：2018-11-27 18:17

【摘要】：为研究路堤荷载下刚柔长短桩复合地基的承载特性,结合某桥头过渡段带帽薄壁管桩(pre-stressed thin-wall concrete,PTC)联合水泥土搅拌桩(cement deep mixed,CDM)的软基处理工程,开展了PTC-CDM组合式长短桩复合地基承载特性现场试验,对路堤填筑过程中桩土应力比、荷载分担比以及桩土沉降差的变化规律进行了分析,并进一步采用有限元对刚柔长短桩复合地基的路堤荷载传递规律进行了数值模拟.试验与计算结果表明:CDM桩顶与桩间土应力增长缓慢,PTC桩帽上应力增长相对较快;填土达到一定高度土拱完全形成后,大量的路堤荷载转移至刚性长桩;刚性长桩和柔性短桩的桩土应力比分别达到7.5和2.1;短桩的存在减少了长桩桩顶荷载和上部桩身出现负摩阻力的深度,中性点位置上移;短桩达到一定桩长时再增加其长度,对路基总沉降影响不明显,因此,短桩桩长可根据承载力要求的临界桩长来设计.
[Abstract]:In order to study the bearing characteristics of rigid and long pile composite foundation under embankment load, the soft foundation treatment of a bridge head transition section with cap thin-walled pipe pile (pre-stressed thin-wall concrete,PTC) combined with cement soil mixing pile (cement deep mixed,CDM) was studied. The field test of bearing characteristics of PTC-CDM composite foundation with long-long pile is carried out. The variation law of pile-soil stress ratio, load-sharing ratio and pile-soil settlement difference during embankment filling are analyzed. Furthermore, finite element method is used to simulate the load transfer law of embankment of rigid-flexible pile composite foundation. The results of test and calculation show that the stress on the top of CDM pile and the soil between piles increases slowly, and the stress on PTC pile cap increases relatively quickly, and when the soil arch reaches a certain height, a large number of embankment loads transfer to rigid long piles. The pile-soil stress ratio of rigid long pile and flexible short pile is 7.5 and 2.1 respectively, the existence of short pile reduces the depth of negative friction and the position of neutral point moves up. The short pile length can be designed according to the critical pile length required by the bearing capacity because the length of the short pile increases when it reaches a certain length, which has little effect on the total settlement of the roadbed.
【作者单位】：中南大学土木工程学院;长沙理工大学道路结构与材料交通行业重点实验室;东南大学交通学院;
【基金】：国家自然科学青年基金资助项目(51208517;51108048) 湖南省科技计划博士后专项项目(2012RS4002)
【分类号】：U416.1

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