基于压水试验和放水恢复试验的帷幕注浆效果综合评价

帷幕注浆效果评价是烧变岩水害治理工程的重要环节之一。以神南矿区柠条塔煤矿S1232工作面烧变岩水害帷幕注浆工程为背景,分别采用检查孔取心验证、注浆前后压水试验、抽水试验以及井下放水试验恢复试验对治理工程的效果进行综合评价。结果表明:通过取心发现在风化基岩段均见到水泥浆液充填薄层,J5孔在烧变岩烘烤岩层中发现浆液填充。注浆后续孔的渗透系数在1.8×10^(-5)~5.9×10^(-5)cm/s,5个检查孔中的渗透系数为2.2×10^(-5)~3.7×10^(-5)cm/s,注浆后的抽水孔渗透系数在2.7×10^(-5)~4.3×10^(-5)cm/s,均属于弱透水。对比注浆前的渗透系数,注浆后的所有钻孔压水试验获得的地层渗透系数均减少了一个数量级。根据抽水实验结果,注浆前后的渗透系数为190×10^(-6)cm/s和(1.04~2.2)×10^(-6)cm/s,单位涌水量分别为0.045 9L/(s·m)和0.014 1~0.023 1L/(s·m)。注浆后帷幕区域渗透系数远小于注浆前,相差两个数量级,单位涌水量数值也减小了一半。根据注浆前后放水恢复实验结果,注浆后井下关水水位恢复均较注浆前快。F26孔初始水压0.8MPa,注浆前后分别在关水后4h和5.55h后水压恢复至0.6MPa;地面长观孔的水位变化也呈现相同的趋势。以上所有指标均反映了帷幕注浆工程对火烧区改造明显,和南侧烧变岩含水层的水力联系明显降低,帷幕注浆效果明显。研究成果将为类似条件的烧变岩水害治理工程效果评价提供参考。

Effects of Tangential Velocity Distribution on Flow Stability in a Draft Tube

Numerical simulations of the flow in the draft tube of a Francis turbine are carried out in order to elucidate the effects of tangential velocity on flow stability.Influence of the location of the maximum tangential velocity is explored considering the equality of the total energy at the inlet of the draft tube.It is found that the amplitude of the pressure fluctuation decreases when the location of the maximum of the tangential velocity moves from the centre to the wall on the cross section.Thus,the stability of the flow in the draft tube increases with the moving of the location of the maximum tangential velocity.However,the relative hydraulic loss increases and the recovery coefficient of the draft tube decreases slightly.