厚表土薄基岩凿井突水溃砂井筒破坏治理技术研究

Study on shaft damage control technology of water inrush and sand burst in drilling process with thick topsoil and thin bedrock

针对厚表土薄基岩地层凿井井筒溃砂涌水综合治理修复技术难题,以两淮矿区某在建煤矿副井为工程背景,分析认为马头门上覆岩层受反复扰动发生弯曲下沉变形是该矿副井井筒破坏的主要原因,主、风井井筒破坏为副井引发的次生破坏。本着修复、预防并重的原则,制定"注、冻、修、防"井筒综合治理方案,即通过地面注浆改善地层性能,防止下部基岩再次发生弯曲变形;通过套壁与原井壁形成复合井壁,提高井筒在该复杂地层条件下的结构安全度;既有井筒围岩冻结作为套壁措施工程,为其施工提供安全保障。研发了系列井筒及马头门修复施工技术:(1)下行式钻注结合,见漏就注,多级套管的挠动地层注浆孔施工与注浆技术;(2)副井内、外排孔分别采用局部、全深冻结,主、风井全深冻结,冻结壁内均设置水文卸压孔,测温数据与数值模拟结合预测冻结壁发展的控制冻结技术;(3)依据井壁破坏程度采取不同修补方式的井壁修复技术;(4)组合钢板拼装和焊接、高性能混凝土(钢纤维混凝土)配制等内套钢板井壁施工技术;(5)壁后注浆加固马头门围岩,破损马头门破除,超强复合永久支护控制围岩,两侧同时分层修复架设施工技术等。综合监测结果表明:工业广场内地表沉降稳定;修复后的3个井筒内套井壁内力和副井壁间压力均小于设计值;主、风井井筒涌水量各为1m~3/d左右,副井井筒涌水量为4 m~3/d左右。采用该方案修复后的主、副、风3个井筒,符合相关规范(程)要求,井筒均处于安全运行状态。

Aiming at the technical problems of comprehensive treatment and repair of sand burst and water gushing in drilling wellbore in thick surface and thin bedrock strata,taking a coal mine auxiliary shaft under construction in Lianghuai Mining Area as an engineering background,the analysis shows that the bending and subsidence deformation of the overburden strata of ingate under repeated disturbance is the main cause of the damage of the auxiliary shaft.The damage of main shaft and air shaft is secondary damage caused by auxiliary wells.In line with the principle of paying equal attention to repair and prevention,a comprehensive control scheme for injection,freezing,repair and prevention wellbore is formulated.That is to say,ground grouting can improve formation performance and prevent bending de⁃formation of lower bedrock;compound shaft lining can be formed by sleeve shaft lining and original shaft lining to improve the structural safety of the shaft in this complex stratum condition;freezing surrounding rock of existing shaft can be used as sleeve shaft lining measure engineering to provide safety guarantee for its construction.Research and development of a series of wellbore and ingate repair construction technology:①downward drilling and injection combined with leakage,multi-stage casing flexible formation grouting hole construction and grouting technology;②auxiliary wells,drainage holes are respectively local and full depth freezing,main and air wells are full depth freezing,hydrological pressure relief holes are set in the freezing shaft lining,temperature measurement data and numerical model,combi⁃ning with the control freezing technology to predict the development of freezing shaft lining;③adopting different repair methods according to the damage degree of shaft shaft lining;④the construction technology of inner steel plate shaft shaft lining,such as assembling and welding of composite steel plate,preparation of high performance concrete(steel fiber concrete);⑤and strengthening surrounding rock of ingate by grouting behind the shaft lining,breaking ingate super-strong composite permanent support control surrounding rock,layered re⁃pair and erection technology on both sides at the same time.The comprehensive monitoring results show that the surface subsidence in the industrial square is stable;the internal force of the sleeve shaft lining and the pressure between the auxiliary wellbore are less than the de⁃sign value after repair;the water inflow of the main and air wellbore is about 1 m^(3)/d,and the water inflow of the auxiliary wellbore is a⁃bout 4 m^(3)/d.The main,auxiliary and air wellbore repaired by this scheme meets the requirements of relevant specifications and are in safe operation state.