井筒冻结孔解冻涌水发生机制及其控制技术

Mechanism and control technology of water inrush from shaft freezing holes after thawing

针对冻结井筒解冻后频繁发生涌水灾害的情况,通过工程实例分析了冻结技术、井筒地层条件及解冻涌水特征。结果表明,涌水发生是由于解冻后冻结止水帷幕失效,冻结管周围地层介质渗透性增强,介质接触界面粘结强度降低而致界面缝隙扩大连通,使冻结钻孔连通含、隔水层而形成竖向导水通道,通道内高压水通过井筒薄弱部位发生涌水。采取在井筒外围适宜地层开挖环形巷道,在环形巷道内逐个切断冻结管并向冻结管内外注浆加固,最后将环形巷道用混凝土回填,形成人工隔水塞层。利用RFPA2D–Flow渗流耦合模型验证了该治理方案的可行性,且利用FLAC3D程序计算出环形巷道距离井壁7.50 m是最佳开凿位置。经该措施处理后的井筒涌水由原来的90 m3/h降低至2 m3/h,且井筒保持了稳定。

In order to solve water inrush disaster from shaft freezing holes, based on analyzing the characteristic offreezing sinking technology, stratum condition and water inrush status from freezing holes after thawing in someprojects, it is indicated that four reasons result in water inrush. Firstly, water-resisting curtain is failure after stratumthawing; secondly, the stratum penetrability increases around freezing holes; thirdly, the interface adhesionstrength is reduced, as a result, the aquifer and aquifuge are connected during freezing holes to form vertical channelfor water; fourthly, the high confined water can spurt from weakest part of shaft. Calculating by RFPA^D–Flowseepage program, the project is workable, and the best radius is 7.50 m to dig circular impermeable tunnel by LAC^D. digging circular tunnel at feasible stratum outside shaft and cutting off freezing pipe to grout, then backfillingthe circular tunnel to form artificial aquifuge were taken, the quantity of water inrush was reduced from90m^/h to 2m^/h, and the shaft was steady, reaching the aim of control and prevention of water inrush.