椒江二桥主墩大直径超长嵌岩桩成孔技术

椒江二桥为(70+140+480+140+70)m双塔双索面组合梁斜拉桥。主墩基础采用2.5～2.8m变直径超长嵌岩桩,桩长120～139m,最大钻孔深度达149m,地质情况复杂,施工难度大。针对椒江二桥主墩超长嵌岩桩钻孔施工过程中易出现的斜孔、渗漏浆、堵塞钻杆等难题,采取加大钻机功率、提前更换滚刀钻头、斜岩面处减压扫孔、配备优质泥浆、改进钻头等措施,确保所有桩基顺利成孔,超声波检测均满足设计和规范要求。

Technique of Hole Boring for Large Diameter and Very Long Rock Socketed Piles of Main Piers of the Second Jiaojiang River Bridge

The Second Jiaojiang River Bridge is a composite girder cable-stayed bridge with double pylons,double cable planes and with span arrangement(70+140+480+140+70) m.The foundations for the main piers of the bridge are of the 2.5～2.8 m very long rock socketed piles with variable diameters.The length of the piles is 120~139 m,the deepest bored hole of the piles is 149 m and at the locations of the piles,the geologic conditions are complex and the construction of the piles is difficult.In view of the problems that the inclining holes,cement mortar leakage and blockage of boring stems would easily occur in the construction of the piles,a series of measures of increasing the boring machine power,changing the cutter bits in advance,boring off the holes at inclining rock surface by pressure reducing,mixing the high quality slurry and improving the boring bits were taken to ensure that all hole boring could be smoothly carried out and the ultrasonic detection of the completed piles would satisfy the relevant design and code requirements.