Abstract:

Groundwater loss caused by karst tunnel construction will affect the surrounding residents and the growth of vegetation. In order to study the influence of tunnel constructioncaused groundwater loss on ecological environment around, the influence of the groundwater loss on the growth of vegetation is evaluated based on three overlapped tunnels crossing Zhonglianshan (i.e. Zhongliangshan Tunnel on XiangyangChongqing Railway, Daxuecheng Tunnel on ChongqingSuining Highway and Geleshan Tunnel on ChengduChongqing Passengerdedicated Line). The growth conditions of Chinese fir and Masson pine are determined by the average ring width, and limited drainage and preventive measures are found to be an appropriate way for groundwater discharge. The results show that: (1) The Zhongliangshan Tunnel with unlimited groundwater discharge induces a strong impact on the quantity of Masson pine (reduced by 71.4%); while the other two tunnels with limited groundwater discharge have relatively low impact on the quantity of Masson pines. (2) The growth of Chinese fir is affected by all three tunnels, and the impact range is about 1 km from the centerline of the tunnel. (3) Based on the recovery period of Masson pines (19921997), the lowest water level in this period is suggested to be the lower limit of the buried depth for the balance of groundwater and ecology, and further to confirm the ecological water level by limited discharge of the disease management concept in Zhongliangshan Tunnel, which is "mainly stop and limited discharge". The results can provide useful information for the control of water level by limited discharge in karst tunnels.

Key words: karst area, tunnel, groundwater loss, growth of vegetation, Masson pine, Chinese fir