摘要
桥梁大直径超长桩通常采用气举反循环钻进施工,沉没比是重要的钻进参数。为了解大直径超长桩气举反循环施工沉没比的变化规律,以甬江左线特大桥3.0m、长132.5m的钻孔灌注桩气举反循环施工为背景进行分析。根据气举反循环原理,计算风包埋深,并结合试钻结果制定风包倒换方案,采用该方案进行钻进施工,获得沉没比、风包埋深、风压、钻进深度之间的关系。结果表明:为实现气举反循环泥浆上返,在风包埋深确定的情况下风压必须达到一定值,或在相应风压下风包埋深必须小于一定值;气举反循环开始时间由沉没比决定,沉没比大于0.4时才有可能进行;随钻进深度的增加,沉没比持续增大,但到一定程度后沉没比不再增加而是趋于稳定;换滚刀钻头对于沉没比并无太大的影响。
The large-diameter very long piles are usually constructed by air-lift reverse circula-tion method and the submergence ratio is an important drilling parameter .In order to control the law of submergence ratio variation during the air-lift reverse construction of large diameter very long piles ,the air-lift reverse construction of the 132 .5 m long bored piles with a diameter of 3 .0 m of the left bridge of Yongjiang River Bridge was taken as the study background .Based on the principle of air-lift reverse circulation ,the burying depth of wind package was calculated ,and com-bined with the results of the trial drilling ,the rearrangement scheme for the wind package was made ,according to w hich the drilling construction conducted and the relations among the submer-gence ratio ,burying depth of the wind package ,air pressure and drilling depths were gained .The results indicate that to make the slurry produced during the air-lift reverse circulation flow up-wards ,the wind pressure must reach a certain value under the condition that the burying depth of the wind package is fixed ,or the burying depth of the wind package must be smaller than a certain value under the relevant wind pressure .The initiation of the air-lift reverse circulation was dictated by the submergence ratio ,only when the submergence ratio is greater than 0 .4 can the air-lift re-verse circulation construction start .As the drilling depth increases ,the submergence ratio steadily rises ,but w hen reaching a certain degree ,the submergence ratio does not continue to increase but tends to be stable .And the application of hob drill showed no effect on the submergence ratio .
出处
《世界桥梁》
北大核心
2014年第4期64-67,共4页
World Bridges
关键词
钻孔灌注桩
气举反循环
风包埋深
风包倒换
沉没比
钻进深度
变化规律
bored pile
air-lift reverse circulation
burying depth of wind package
wind pack-age rearrangement
submergence ratio
drilling depth
variation law