The Impaction On Groundwater And Vegetation Of Cimushan Tunnel Construction

With the development of basic construction, more and more city-and railwaytunnel crossing through the scenic areas. Tunnel excavation breaking the existinggroundwater balance, it would change or reform the surface and ground water collectionsits and discharge passage. This would change the hydrogeology, engineeringgeological conditions within the scope of the project, and further impact the ecologicalenvironment and especially vegetation in tunnel site.Now except some special tunnels adopting fully waterproof method, most projects,especially mountain area tunnel follow the principle “waterproofing, drainage control,disconnect the water supply, and comprehensive management according to the localcondition.” But in real project, the drainage still be the most common way to solve thetunnel water gushing. This method will not only cause serious economic losses, but alsolead the deterioration of environment.The author studies the water inflow during tunnel excavation on the base ofCimushan tunnel. Using filed investigation, water chemical analysis, theoreticalanalysis and numerical analysis, the work carried out as fellow:①Basing on the engineering geological survey information and field research theauthor uses the groundwater runoff modulus, precipitation infiltration and dynamicshorizontal tunnel dewatering empirical formulas together with groundwater dynamicsmethod to calculate and evaluate the water inflow of tunnel.②And then, using the MIDAS/GTS to predicate the change of total head and porepressure head and water inflow during tunnel excavation.③Thirdly, consider the effective of surround rock grouting, the different rockpermeability coefficient is used to analysis the ground water change and the pluggingeffect.④Comparing the water inflow value calculated from different methods and reachthe conclusions of groundwater change during tunnel construction in this region.⑤According to the literature, field research data and vegetation types andvegetation characteristics in the tunnel site, together with the calculated water inflowvalue to analysis the tunnel construction impact on vegetation. ⑥Choosing the Zhenwu tunnel and Geleshan tunnel do the vegetation comparisonanalysis, further illustrate the impact of tunnel construction on vegetation is very small.