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我队在多孔抽水中，7号孔为试验主孔，其目的是评价矿区中段灰岩富水性，给矿坑涌水量预测提供依据。为了取得可靠的水文地质资料，必须采用清水钻进，在整个钻进孔段，灰岩是主攻对象。灰岩本身硬，脆，碎，裂隙多，填充物是松散软泥状；破碎带则呈松散砂粒状，胶结性极差。由于钻进时钻具敲打孔壁；起钻时下部钻孔形成低压空间，地下水携带沉砂涌进孔内，有时碴子抽进管内，少者1—2米，多者5—8米；有时掉块较大，堵着钻孔，使孔壁失去稳定性。造成孔内严重坍塌，涌碴，掉块，漏水，连续捞碴而始终是不减少，影响施工进度。
My team in the porous pumping, hole No. 7 as the main test hole, the purpose is to assess the middle of the limestone reservoir water-rich, to provide a basis for prediction of mine pit water. In order to obtain reliable hydrogeological data, it is necessary to use clean water to drill in. The limestone is the main target of drilling through the entire borehole. Limestone itself hard, brittle, broken, fissures and more filled loose clay-like; broken belt was loose sand-like, poor cementing. As the drilling tool hits the wall of the hole, the lower part of the hole drills to form a low-pressure space, and the groundwater carries grit into the hole, sometimes the ballast is drawn into the tube, less 1-2 meters, mostly 5-8 meters; Sometimes the larger block, blocking the drilling, the hole wall loss of stability. Resulting in a serious collapse of the hole, Chung ballast, block, leakage, continuous ballast and never reduce, affecting the construction progress.