深层隧道排水系统中井隧水力学特性研究

Study on the hydraulic characteristics of dropshaft and tunnel in the deep tunnel drainage system

深层隧道排水系统(深隧)是布置于深层地下的大型排水工程,一般由调蓄隧道、入流竖井、通风设施(排气井)及排水泵站组成,具有调蓄雨洪及控制溢流污染的作用。其中调蓄隧道为避开地铁等城市地下工程往往布置于距离地面30~60 m深处,入流竖井连接地表浅层管网和深层隧道。深隧系统竖井内部的水力学特性复杂,具有单宽流量大、落差高及大量掺气等特点,处理不当将造成较大的破坏。而极端降雨期间,由于未能充分排气而产生的间歇喷涌,也会对设施造成损害。本研究采用物理模型试验和水-气两相流数学模型CLSVOF(Coupling Level Set and Volume Of Fluid),研究了不同结构竖井(旋流式竖井和螺旋阶梯式竖井)水力学特性和调蓄隧道中的间歇喷涌问题。根据施工条件设计的两种竖井方案的消能率接近,旋流竖井存在负压及较大震动、排气不畅,而螺旋阶梯式竖井流速较低且流态稳定。在对调蓄隧道中"间歇喷涌"的数值模拟研究中,排气井管径对间歇喷涌的影响十分显著,模拟情景中最剧烈的喷涌会产生5.35倍初始状态下的测压管水头和38.2 m/s的喷涌速度。

The deep tunnel drainage system is a large-scale drainage project arranged deep underground,which has the functions of regulating-storing stormwater and controlling overflow pollution.It is composed of a main tunnel,dropshaft,exhaust shaft and drainage pump group.The storage tunnel is arranged normally underground deeper than 30-60 m,and the dropshaft connects the surface shallow pipe network and the deep tunnel.The hydraulic characteristics inside the dropshaft of the deep tunnel system are complex,with the characteristics of a high hydraulic head and large discharge as well as aeration and air exhaust.Improper handling can cause great damage.During periods of extreme rainfall,geysers due to insufficient exhaust can also cause damage to facilities.In this study,physical model tests and mathematical models of waterair two-phase flow were used to study the hydraulic characteristics of dropshafts with different structures(vortex dropshaft and stepped spillway dropshafts)and geysers in storage tunnels.The energy dissipation rates of the two dropshaft schemes designed according to the construction conditions are close.There are negative pressure,large vibration and poor exhaust in the vortex dropshaft,while the flow velocity in the stepped spillway dropshaft is low and the flow pattern is stable.In the numerical simulation study of the"geysers"in the storage tunnel,the diameter of the exhaust shaft has a significant influence on the intermittent spout.The most violent geyser in the simulation scenario will produce 5.35 times the piezometric head in the initial state and a gushing velocity of 38.2 m/s.