双线地铁隧道间小净距桥梁钻孔桩施工技术

Construction Techniques for Bored Piles of Bridge Near to Double-Track Metro Tunnel

杨泗港长江大桥汉阳侧匝道桥为连续梁桥,处于地铁上下行隧道区间,基础采用1.2m、1.5m钻孔桩,桩身与隧道最小净距仅3.1m,施工要求与地铁交叉施工区的钻孔桩须在地铁运营调试前完成。受施工环境和工期等限制,该桥桩基采用快速施工工艺:对局部土层进行注浆预加固;采用2台多功能旋挖钻机旋压跟进长护筒;采用大比重优质膨润土泥浆护壁、振动小的设备钻孔等工艺进行快速成孔施工。施工中,护筒对接、焊接接长、护筒内取土、护筒旋转下压等工序循环交替进行直至支护标高,其中第一节护筒底部装有合金钻头(比护筒直径大2cm)。成桩时,单桩钢筋笼采用"长线"法在台座上整体制作成型,接头机械连接,采用汽车吊分节段接长吊装入孔;采用2次清孔工艺,清孔合格后灌注水下混凝土。施工监测和检测结果表明,地铁隧道结构安全,桩基质量满足要求。

The Hanyang side ramp bridge of Yangsigang Changjiang River Bridge is a continu ous beam structure. It is located between two metro tunnels carrying tracks to two opposite direc tions. The foundation is formed of bored piles that are 1.2 m and 1.5 m in diameter, the shortest distance of the pile shaft to the tunnel is only 3.1 m. The construction of bored piles in the joint construction area of the foundation and the metro must be completed before the operation adjusting and testing of the metro , according to the construction schedule. Limited by the construction envi ronment and schedule, the pile foundation was constructed using the accelerated construction tech nique. The ground in some parts was pre strengthened by grouting. The steel pipes were driven down by two multifunctional rotary drilling rigs. The pile holes were quickly formed by using slur ry walls made of large proportional and high quality expansive soil and the equipment with slight vibration. During the construction, the procedures of butt joining of steel pipes, steel pipe length ening by welding, clearing soil inside the steel pipes and the rotary drilling of steel pipes were car ried out alternatively until reaching the supporting elevation. The alloy drilling bit , which is 2 cm larger than the diameter of the steep pipe, was installed on the base of the first lift of the steel pipe. During the pile formation, the steel casing of the single pile was integrally fabricated by the long line matching method, mechanically joined, and then lifted and lowered into the hole section by section by the truck mounted crane. The pile holes were cleared by two times, after evaluated qualified, the tremie concrete was poured. The results of the construction monitoring and inspec tion demonstrate that the metro tunnel structure is secure and the quality of the pile foundation meets the requirements.