含砂地层大直径旋挖钻孔桩孔内泥浆性能研究

Study on the mud properties of large diameter rotary drilling bored pile in sand stratum

为探究大直径钻孔桩在成孔过程中孔内泥浆性能的变化及对施工质量的影响,以龙泉市大直径钻孔桩的施工为背景,根据对现场泥浆性能的测量结果及时制定应对措施,为大直径钻孔桩的施工提供参考。结果表明,在成孔过程中泥浆中的砂子向孔底沉淀,使孔内泥浆比重逐渐减小,含砂率与比重的拟合指数R2在0.858~0.987之间。泥浆含砂率的降低导致其黏度下降,在循环使用期间,泥浆中的胶体部分逐渐被消耗,导致清孔时泥浆携砂性能下降。终孔后,泥浆含砂率的变化直接影响孔底沉渣厚度,孔底泥浆含渣率最高可达86%。采用气举反循环方式协同除砂机进行清孔,1.5~2 h可完成清孔;清孔完毕后应立即浇灌混凝土,避免孔底再次淤积沉渣。

In order to investigate the changes of mud properties and its impact on the quality of construction, the construction of large diameter rotary drilling bored pile in the process of hole forming in Longquan city is taken as the background. According to the changes of mud properties measured on site, the control measures are formulated in time,which provides reference for construction of large diameter bored pile. The results show that the sand in the mud of the hole precipitates towards the bottom of the hole during hole forming, so that the mud specific gravity in the hole gradually decreases, and the fitting indexes R2 between the sand content and specific gravity are between 0.858 and 0.987. The decrease of sand content results in the decrease of mud viscosity, and the colloidal portion of the mud is gradually consumed during the cycle, which leads to the sand carrying capacity of mud decreasing during hole cleaning.After finishing drilling, the changes of sand content of the mud directly affects the thickness of the sediment at the bottom of the hole. The sand content of the mud is up to 86%. The gas lift reverse circulation together with the sand removal machine is used to clear the hole, and the clearing process can be completed in 1.5-2 hours. After clearing the hole, it is necessary to pour concrete immediately to avoid sediment deposition at the bottom of the hole again.