ф3.8m大直径钻孔桩钻填施工

Construction of Boring and Concreting of ф3.8m Large Diameter Bored Piles

嘉绍大桥两岸水中区引桥采用ф3.8 m大直径钻孔桩,考虑工程规模及复杂的水文地质条件,选用国内首次采用的KTY-4000型大扭矩动力头液压式旋转钻机施钻,气举反循环排渣,泥浆护壁,水下填充混凝土成桩。主要施工流程为:施工准备;钻孔平台搭设;钢护筒插打;摆放钻机、钻孔;终孔、检孔、清孔;安放钢筋笼、二次清孔;水下填充桩身混凝土;桩底压浆、桩头凿除、超声波无损检测。施工前对可能出现的问题进行分析,并采取了针对性的防范措施,施工仅发生了可塑状粉质粘土包钻和钻孔漏浆问题。目前施工进展顺利,说明该方案是可行和适用的。

The ф3.8 m large diameter bored piles were used for the approach bridge piers in the water areas on both banks of Jiashao Bridge.In consideration of the construction scale and the complicated hydrologic and geologic conditions at the bridge site,the large torque,power head and hydraulic KTY-4000 rotary boring machine put in use for the first-time domestically was selected for the boring construction of the piles.The boring slag in the bored holes of the piles was cleared off through reverse circulation by air lifting,the walls of the holes were protected by slurry and the treime concrete was then cast into the holes to consequently form the piles.The principal construction procedures for the plies included the construction preparation,setting up of boring platforms,inserting and driving of steel casings,setting of boring machine,boring,completing of bored holes,inspection of the holes,clearing-off of the holes,laying of reinforcement cages,the second time clearing-off of the holes,casting of tremie concrete into the holes,grouting of pile bases,chiseling-off of pile heads and ultrasonic inspection of the completed piles.Before the construction started,the possible problems that might occur were analyzed and the corresponding preventive measures were taken in advance.In the boring construction,only the problems of wrapping of the boring bits by the plastic silt clay and slurry leakage occurred.At present,the construction of the bored piles of the bridge is still underway,showing that the construction scheme mentioned above are feasible and practicable.