在临水或水中大直径超长桩施工中,由于孔外水压力大、水位变化频繁,孔壁稳定显得特别重要,防止孔壁塌落导致钢筋笼被泥砂掩埋的事故.以长江上某特大桥施工中钢筋笼被泥砂掩埋为案例,研究了水位变化频繁下大直径超长桩中钢筋笼埋后处理及预防的措施.①泥浆的密度、黏度参数要达到维护孔壁稳定性的要求;②作业人员每间隔2小时测量一次密度、黏度参数、护筒内外液面高差;③孔壁塌落导致钢筋笼被泥砂掩埋后,为了起拔钢筋笼,用导向筒钻头清理沉渣;④在清理沉渣时,要随时观察反映导向筒钻头所遇阻力大小的扭矩,及时提钻;⑤在大直径超长桩施工中,不能一味追求施工速度、节约成本.%During the construction of bored pile beside the water or in the water,we should pay attention to the stability of hole wall to prevent steel cage buried by collapsed mud and sand from hole wall because of larger water pressure and frequent water level change outside the hole. The author takes buried reinforcement of the Yangtze River bridge in the construction as a case,and treatments and preventions of buried reinforcement in large diameter and super-length pile under frequent water level change are researched. Firstly,the density and viscosity of slurry are required to maintain the stability of the hole wall. Secondly,in the interval of 2 hours,density and viscosity of slurry,liquid level height inside and outside the steel casing are measured. Thirdly,after steel cage is buried by collapsed mud and sand,the sediment is cleaned with the guide cylinder drill in order to lift steel bar cage. Fourthly,when sediment is cleaned,torque reflecting the resistance of drill is observed timely. Fifthly,during the construction of large diameter and super-length pile,we should not only pursue construction speed and cost saving.
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