护壁套管钻孔灌注桩微扰动施工分析

在上海轨道交通9号线盾构隧道的近距离钻孔灌注桩微扰动施工中，预先将护钢套管旋压至超出隧道底部约3 m后，再用泥浆循环方法进行取土成孔。实测结果表明，由于钢套管的护壁作用，钻孔灌注桩成孔时在钢套管位置几乎不存在地层损失；随着钢套管旋入深度的增加，管内土体的堵塞程度越来越严重，当钢套管旋压至隧道轴线以下位置时发生相对较严重的土体挤压，导致隧道上浮，并发生竖椭圆收敛变形。为减小护壁套管旋压过程中对既有地铁隧道的影响，建议在钢套管旋入过程中同时取出套管内部分土体。

Analysis of small disturbing construction of protective jacket tube for cast-in-situ bored pile

The small disturbing scheme that rotating and pressing the protective jacket tube to the depth which under the shield tunnel bottom about 3 meter and then boring the hole through the slurry circulating system has been used in the construction of cast-in-situ bored pile, which near to the shield tunnel of Shanghai Metro Line 9. The actual measurement shows that there is no ground loss in the scope of the protective jacket tube when boring the hole. The soil blocked the tube more and more serious with the increase of the depth of the protective jacket tube, and there is some soil squeezed out when the bottom of the tube under the axis of the tunnel, so the tunnel came-up and the vertical ellipse deformation occurred. In order to decrease the influence from the construction of the protective jacket tube, it is suggested that some of the soil should take out from the protective jacket tube when pressing it in the ground.