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我队施工的西湖引水隧洞工程,穿过长约70m的土层,掘进断面为2.9×2.9m的直壁圆弧拱形,采用钢支架支护,支架间距0.6m,覆盖层是厚3～12m的褐黄-褐红粘土,硬塑性,多为灰岩顶面的残坡积土,夹有少量碎灰岩,上部是约1m厚的堆填土石渣,雨天渗水严重。由于覆盖土层遇水后产生较大的地压作用,距洞口44m处有9道钢支架发生沉陷变形,顶板下沉约达40cm,左侧支架腿被挤压内移约50cm,以致无法挂网成巷。为了保证工程质量,必须对沉陷变形支架加以修复。原先,我们采用先拆除一道旧支架,铲除内移的泥土,再重新架设新支架的方法,但随着旧支架的拆除,垮帮冒顶也在发生(冒顶高达3m),且掉块不止,工
Construction of the team’s West Lake diversion tunnel project, through a length of about 70m of soil, heading section of 2.9 × 2.9m straight-walled arc arch, the use of steel bracket support, stent spacing 0.6m, the cover is 3 ~ 12m of brown yellow - brown red clay, hard plastic, mostly limestone top of the residual soil, with a small amount of crushed limestone, the upper is about 1m thick earthfill gravel, severe rain seepage. Due to the large ground pressure produced by the covering soil, 9 steel mounts at 44m away from the hole caused subsidence, with the top sinking about 40cm and the left leg crushed by about 50cm so as to be unable to hang Network into the lane. In order to ensure the quality of the project, the subsidence deformation support must be repaired. Originally, we used the method of dismantling an old support, removing the soil inside, and then reinstalling the new support. However, with the removal of the old support, roof collapse occurred (roof fall as high as 3m)