考虑生态环境效应的止水帷幕设计方法初探

当隧道旁穿大型水体工程时,常将隧道与水体之间的止水帷幕设计为具有一定开口的结构型式,止水帷幕开口的大小直接关系到其止水能力以及对周边地下水环境的影响程度。文章依托实际工程,采用数值模拟的方法,探讨了止水帷幕开口大小(埋深和密度)对降水效果及水位回升时间的影响。结果表明:(1)止水帷幕的开口大小对水位降深的影响可分为无影响区、渐变区和突变区三个区域;对水位恢复的影响可分为渐变区和突变区;(2)止水帷幕埋深越大,降水效果越好,但回水时间越长;悬挂部分帷幕布置密度越大,降水效果越差,回水时间越短。综合降水效果、回水时间、施工成本等因素,止水帷幕设计参数的选取应落在渐变区内;(3)结合依托工程水文地质条件,给出了该工程止水帷幕设计参数值,即埋深应在14~20 m内,布置密度在0~0.8内,并通过工程应用验证了其有效性。

Preliminary Study on Design Method of Waterproof Curtain Considering Ecological Environment Effect

When a tunnel passes beside a large water conservancy project,the waterproof curtain between them is of ten designed as a structure with a certain opening,the size of the opening is directly related to its waterproof capacity and its influence on the surrounding groundwater environment.Based on practical engineering,the influence of opening size(buried-depth and density)on dewatering effect and recovery time of the water level is discussed by nu merical simulation.The results show that:(1)it can be divided into three zones regarding the impact of opening size on drawdown,i.e.non-affected zone,gradual changing zone and abrupt changing zone;it can be divided into two zones regarding the impact of opening size on recovery of water level,i.e.gradual changing zone and abrupt chang ing zone;(2)the larger of buried depth of waterproof curtain,the better the dewatering effect but the longer of water level recovery time.In light of dewatering effect,water level recovery time,construction cost and so on,the selection of design parameters of waterproof curtain should be within the gradual changing zone;(3)based on its hydrogeologi cal conditions,the design parameters of waterproof curtain are proposed,that is to say the depth and density should be within 14-20 m and 0-0.8 respectively,and the validity is verified by engineering application.