翠屏隧道强补给淹井积水抽排技术研究

Study on Water Drainage Technology for Strong Recharge Flooded Well in Cuiping Tunnel

为处治翠屏隧道1~#斜井工区的强补给淹井积水,确定通过未开挖岩体进行超前泄水的施工方案,建立数值模型分析了岩体需要保留的安全厚度。采用短管自由流公式结合现场测试数据分析了泄水孔的直径及上台阶高度对泄水孔流量的影响。结果表明:Ⅳ_(2)级、Ⅳ_(3)级、Ⅴ_(1)级围岩的安全厚度至少应为10,15,18 m,否则隧道主洞进口工区开挖施工会引起岩体拉裂区联通,淹井积水将透过岩体流入主洞工区;要保证单个泄水孔流量大于300 m^(3)/h,泄水孔直径至少应为150 mm;上台阶高度由5 m降低为3 m,泄水孔流量可提高71.6%。采用了以下抽排水方案:翠屏隧道主洞进口工区采用三台阶法开挖至岩盘厚度40 m时停止掘进,中台阶范围施工50 cm厚C30混凝土止水墙,预留20根DN 200 mm排水管,进行?150 mm超前钻孔泄水施工,在积水水面降至拱顶以下3 m后开挖上台阶。经实践,隧道历经3个月实现了上台阶贯通,但排水过程中隧道岩盘泄水孔很容易堵塞,需要经常性清孔。其他类似工程借鉴本研究成果时,应采用防堵塞措施或减小安全岩盘厚度以提高泄水孔出水流量并降低堵塞的可能性。

In order to treat the strong recharge flooded well of No.1 inclined shaft in Cuiping Tunnel,and determine the construction scheme of advance drainage through unexcavated rock mass,a numerical model is established to analyze the safety thickness of rock mass to be reserved.The influences of the diameter of the drain hole and the height of the upper step on the discharge of the drain hole are analyzed by using the short tube free flow formula in combination with field test data.The result shows that(1) the safety thicknesses of Grade Ⅳ_(2),Grade Ⅳ_(3)and GradeⅤ_(1)rock mass should be 10,15,18 m respectively at least,otherwise,the excavation of the entrance area of the main tunnel will cause the connection of the rock mass fracture area,and the water in flooded well will flow into the main tunnel area through rock mass;(2) the diameter of the drain hole should be at least 150 mm to ensure that the flow rate of single drain hole is greater than 300 m^(3)/h;(3) when the upper step height is reduced from 5 m to 3 m,the flow rate of drainage hole can be increased by 71.6%.The following pumping and draining scheme is adopted:to use the 3-step method to excavate the entrance working area of Cuiping Tunnel until the rock mass thickness is 40 m;in the middle step range,to construct C30 concrete waterproof wall with thickness of 50 cm,to reserve 20 DN 200 mm drainpipes for φ150 mm advanced drilling;to excavate the upper step after the water level drops to 3 m below the arch crown.Through practice,it took 3 months for the tunnel to breakthrough the upper steps.However,during the drainage process,the drainage hole of the rock mass of the tunnel is easily blocked need to be cleaned regularly.When other similar projects using this research result for reference,the anti clogging measures or reducing the thickness of the safety rock mass should be adopted to improve the water flow rate and reduce the possibility of clogging.