摘要
在广州地区,上部土层、下层是岩体的基坑非常普遍,深基坑支护常采用上部桩锚、下部岩层土钉墙,由于在坚硬岩层中施工灌注桩难度大、工效差、桩的入岩深度不够,难以形成理想的桩锚支护体系,导致支护桩处于无嵌固状态,从而出现所谓的"吊脚桩"基坑支护型式。广州周大福金融中心(东塔)深基坑支护主要采用这种型式,在施工过程中大部分监测项的监测数据满足设计要求,局部出现了较大的变形,及时进行了加固处理,保证了基坑的安全。以PLAXIS2D有限元软件为开发平台,建立了上部桩锚、下部岩层土钉墙的"吊脚桩"基坑支护模型,有限元数值计算结果与现场大部分监测结果比较一致,并分析了在不同预留岩肩宽度、锁脚锚索预应力和嵌岩深度下基坑的变形规律。根据有限元分析反映的变形规律,结合现场实际情况,进行了地质分析,实际"吊脚桩"岩肩宽度不够,基坑开挖切断了岩层,产生了顺层滑移,爆破进一步破坏了岩体的完整性,认为顺层滑移和爆破是基坑C区南侧变形较大的主要原因。
The foundation pits with upper soil stratum and underlying rock stratum are commonly in Guangzhou area.The composite supporting systems with the upper pile-anchor piles and lower soil nailing wall are used in deep foundation pit.It is difficult and poor efficiency to construct piles in hard rock.The piles into rock depth are not good enough and it is difficult to form ideal pile-anchor systems.The supporting piles are the so-called"end-suspended pile".The said systems of the deep foundation pit in the CTF Finance Centre(Canton East Tower)are used.During the construction process,the monitoring data for most monitoring items meet the design requirements,but there are large deformations in part area.The reinforcement for the pit is carried out in time,which ensures the safety of the pit.Based on the finite element software PLAXIS 2D,the deep foundation pit models with upper anchor piles and lower soil nailing wall are set up;the main results calculated by FEM are consistent with the in-situ monitor results;the deformation of the pit has been analyzed under different rock shoulder width,axial stress of anchor and rock-socketed depth.Through the overall trends of the deformation from FEM in the pit,combined with the actual situation on the spot,the geological analysis is carried out.The actual rock shoulder width is not enough,the pit excavation cuts off the rock stratum,the rock stratum bedding glides and the blast further destroys the rock integrity.It is considered that the bedding glide and the blasting are the main reasons for the large deformation on the south side of the pit C area.
作者
伍四明
Wu Siming(Guangzhou Urban Planning and Design Survey Research Institute,Guangzhou 510060,China)
出处
《工程勘察》
2020年第12期7-13,共7页
Geotechnical Investigation & Surveying
关键词
深基坑工程
桩锚支护
吊脚桩
基坑监测
有限元分析
地质分析
顺层滑移
爆破
deep foundation pit
pile-anchor support
end-suspended pile
monitoring of excavation
finite element analysis
geological analysis
bedding glide
blast
