引水隧洞穿过防渗帷幕的有关问题探讨

Discussion on Intersection-Related Issues Between Horizontal Section of Diversion Tunnel and Impervious Curtain

引水隧洞上、下水平段与防渗帷幕相交,防渗帷幕的阻水作用使帷幕前、后渗流场发生急剧变化,因此防渗帷幕前、后通常分别采用钢筋混凝土衬砌设计和钢衬钢筋混凝土衬砌设计,对两种衬砌在什么位置相接比较合适及防渗帷幕与引水隧洞水平段交会区需要采取什么加强措施以确保防渗帷幕连续性和衬砌结构安全等问题进行了分析、研究。引水隧洞穿过防渗帷幕容易在幕体与隧洞交接面产生渗流通道,使防渗帷幕整体连续性受到破坏,参考有关工程经验,采用先在隧洞内四周设计环形灌浆幕体,将防渗幕体与隧洞交接面灌浆密实以达到设计要求,然后再将引水隧洞上、下的防渗帷幕与环形灌浆带相接形成连续幕体。用上述方法可有效加强帷幕整体的防渗能力。在库岸形成稳定渗流场之前,水库在蓄水过程中及在蓄至正常高水位以后一段时间内在库岸渗流区将产生不稳定渗流浸润线,在引水隧洞设计时外水压力取值不仅要考虑稳定渗流浸润线,而且要考虑不稳定渗流浸润线对设计荷载的影响,找出不利荷载,使引水隧洞的结构设计更完善、可靠。

The upper and lower segments of horizontal diversion tunnel intersect with impervious curtain. Due to the effect on water-flow re-tardation of the curtain,seepage fields in front of and behind the curtain change dramatically,which results in different linings:concrete lin-ing for the section in front of the curtain and steeling lining for the area where behind the curtain. Such intersection-related issues as the proper connections between the two linings,enforcement for curtain continuity and lining safety that should be undertaken for the intersection with the curtain were studied and discussed by the author. Seepage passages were easily to be emerged at the interface between curtain body and tunnel when going through impervious curtain,which brought damage to the general continuity for the curtain. After referring to relevant engineering projects,ring grouting around the inside tunnel was designed so as to increase the density of the interface;then connecting the upper and lower impervious curtain of the tunnel with ring grouting belt to form as one curtain,the abovementioned approach was effective to strengthen anti-seepage capacity. Before stable seepage field formed at the reservoir bank,unstable saturation line would be generated at the seepage fields at the bank when storing water and storing water at normal high water level for a period of time;therefore,the perfect and reliable design should include stable seepage saturation line for finding the value of external water pressure and the effect inserted on design load by the unstable saturation line when design diversion tunnel so as to make the design more perfect and reliable.