34
施工技术
CONSTRUCTION TECHNOLOCY
2012年4月上第41卷第362期
全套管钻机成孔复合型桩基降水施工新技术
张素英
（北京市轨道交通建设管理有限公司，北京100037）
【摘要】针对基坑降水量小，围护结构外侧改移管线密布且交通繁忙无布设降水井场地，以及漂石地层中管井成孔报告将桩身加长，在桩底填滤料形成汲水区，用副钢筋笼内配套水票、滤管与图护桩钢筋笼连接，排水管和水泵电线置于PVC套管中，沿围护桩钢筋笼升至地面，汲水区上部用细砂将预施围护桩隔离。计算显示围护桩内水位降
深3m时，引起单桩沉降为0.12mm，小于桩顶总沉降值的10%。采用本工艺降低了施工成本，经济效益明显。【关键调】地下工程；基坑：降水；围护桩；全套管钻机：沉降
[中图分类号】TU753.3
【文献标识码］A
【文章编号】1002-8498(2012)07-0034-04
Composite Pile Dewatering Construction New Technology of Hydraulic
Casing Rotator Machine Drilling-holes
Zhang Suying
(Bejing MTR Construction Administration Corporation, Beijing 100037, Ching)
Abstract: Because of small foundation excavation precipitation, pipeline densely covered on the outside of supporting structure and busy traffic, there isn't dewatering well sites and drilling holes is hard in boulder formation and tight schedule. A new composite pile formation dewatering method is proposed which 1meter diameter supporting piles are drilled by hydraulic casing rotator machine. The piles body is extended with the survey report and filter material is filled in the bottom of piles to form water-absorbing area and an assistant reinforcing cage contains a pump and a filter tube which is welded to the supporting pile' reinforcing stage. Water pipeline and wire are protected in the PVC casing which is along the reinforcing stage up to the ground. In the top of the water-absorbing area, sand is filled to separate the prepared constructing supporting pile. Calculations show that the settlement of single pile caused by dewatering is 0. 12mm, when dewatering depth is 3m in a supporting pileless than 10% of the total settlement of the pile. The application of the technology reduces the construction cost and obtains economic benefit.
Key words: underground; foundation excavation; dewatering; supporting piles; hydraulic casing rotator machine;settlement
工程概况
北京地铁某站为两条地铁线路相交换乘车站，
位于城市主干道交叉路口北侧的道路下方，南北向布置。车站西侧为商业超市与住宅小区，东侧为乡政府和住宅小区。车站主体采用装配式铺盖法施工，围护结构为全套管钻机成孔灌注桩。车站南端为两条线换乘节点，换乘节点处基坑深26.52m，基底标高20.08m，进人潜水1.0m，为保证水位在坑底
【收稿日期】2012-01-05
【作者介】张素英，北京市轨道交通建设管理有限公司高级工程师，北京市西城区百万庄大街甲2号
100037，电话：13811100617，
E-mail ; zhangsuying808@ 163. com
万方数据
1m以下，水位需降深2.0m，降水量约为800m。换乘节点临近立交桥，周围交通繁忙，且基坑外改移管线密布，工程环境极其复杂，难以寻找合适的降水井场地。车站所处地层自上而下为人工填土、新近沉积土层、第四纪晚更新世冲洪积地层。第四纪晚更新世冲洪积层包括圆砾卵石③层、卵石层、卵石③层，潜水面在卵石②层。在地层底深3.8 34.2m，粒径200mm以上卵石含量在60%以上，且大漂石含量较高，在层深20m左右，漂石最大粒径可达1000mm。