顾及植物生态劣化的山岭隧道控制排水量计算方法

Calculation Method on Drainage Control of Mountain Tunnel Considering Plant Ecological Degradation

山岭隧道排水会局部改变地层中地下水环境,在生态敏感区如果盲目采用以排为主的隧道排水原则,可能会诱发局部植物生态劣化。本文提出了一种顾及植物生态劣化的山岭隧道控制排水量计算方法,首先建立基于地下水达西渗流与土壤水Feddes原理耦合分析的土壤水分场模型,以植物生态吸水量、植物蒸腾量与降雨补给量作为上边界条件,以隧道排水速率作为下边界条件,以土壤水基质势阈值判别植物生态枯萎为优化逼近条件,最后采用黄金分割最优搜索方法,获得保障植物生态要求山岭隧道排水量控制值。以苏州七子山隧道为案例,采用本文所提方法得到以松杉为生态控制目标植物的不同控制断面隧道排水量分别为:洞口段排水量是329 m^(3)/d,深埋段排水量是336 m^(3)/d,浅埋段排水量是325 m^(3)/d;同时得到满足松杉生态要求的洞口段水位为地表以下3.6 m,深埋段水位为地表以下18.9 m;浅埋段水位为地表以下14.2 m。本文所提方法可以作为隧道排水量控制依据为山岭隧道生态控制与保护提供指导。

The drainage of mountain tunnels could locally change the groundwater environment in the stratum.If the drainage principle is blindly adopted in the ecologically sensitive area,it will induce local plant ecological degradation.This paper proposes a calculation method for controlling the drainage of mountain tunnels preventing the plant ecological degradation.First,a soil moisture field model is established based on coupling analysis of the Darcy of seepage and the Feddes principle of moisture.The ecological water absorption of plants,plant transpiration,and rainfall replenishment is taken as the upper boundary conditions,the tunnel drainage rate is taken as the lower boundary conditions,and the soil water matrix potential threshold is discriminated by plant ecological wilting is taken as the optimization approximation condition.The controlling drainage of the mountain tunnel can be obtained using the golden section optimal search method.Taking pine trees as the target plant for ecological protection,the controlling drainage of the Qizi mountain Tunnel of Suzhou city is obtained using the proposed method as listed:the entrance section of 329 m^(3)/d,the deep buried section of 336 m^(3)/d,and the shallow buried section of 325 m^(3)/d.Meanwhile,the controlling underground water level is obtained as listed:the entrance section of 3.6 m below the earth surface,the deep buried section of 18.9 m below the earth surface,and the shallow buried section of 14.2 m below the earth surface.The method proposed can be used as the basis and guidance for controlling drainage and ecological protection of mountain tunnels.