坚硬岩石地层钻孔桩旋挖钻机成孔技术

Using Rotary Drilling Rigs to Make Holes for Bored Piles in Hard Rock Strata

新建商合杭铁路芜湖长江公铁大桥主桥为(98+238+588+224+84) m钢箱板桁结合梁高低矮塔斜拉桥。主桥0号边墩和1号辅助墩均为22Ф2.5 m钻孔桩基础,设计桩长42~58m,入岩深度17~28m,岩石最大强度达151MPa,采用旋挖钻机施工成孔。旋挖钻机布置在水上钻孔平台上,钻孔过程中采用优质膨润土化学泥浆护壁。覆盖层中采用截齿钻头全断面钻进;倾斜或软硬交界岩面采用“稳定器+截齿钻头或取芯钻头”钻进1.2~1.5m;坚硬岩层中采用牙轮环切钻头和扩孔钻头按照? 1.5 m→Ф2.0 m→Ф2.5 m分3级钻进成孔。最后采用泵吸反循环清孔。

The main bridge of Wuhu Changjiang River Rail-cum-Road Bridge on the newly-built Shangqiu-Hefei-Hangzhou high-speed railway is an extradosed bridge with five spans of 98, 238, 588, 224 and 84 m. The bridge has two pylons of different heights and the main girder is the composite structure formed of steel box beams, steel trusses and concrete slabs. The No. 0 end pier and the No. 1 auxiliary pier all stand on the foundation formed of 22,Ф2.5 m bored piles. The piles have the designed lengths of 42 to 58 m, and extend about 17 to 28 m into the rock. The maximum hardness of the rock reached up to 151 MPa, as a result, the rotary drilling rigs were used to make holes for the piles. The rotary drilling rigs were placed on the water drilling platform, and high-quality bentonite slurry was filled to protect the walls of the holes during the hole drilling process. For the overburden, cutting bits were used for full cross-section drilling. For the oblique rock surfaces or the soft and hard rock interfaces,“the stabilizer and cutting bits or coring bits” were used in combination to drill a depth of 1.2 to 1.5 m. In the hard rock strata, the rolling cutter bits and reamers were used to form holes from a diameter ofФ1.5 m throughФ2.0 m toФ2.5 m. At last, the holes were cleared by pumps by means of reverse circulation.