超高填方明洞采用双层衬砌型式的可行性研究

高填方明洞衬砌厚度常超过2 m,工后受水化放热影响易产生收缩裂缝并影响结构安全,故提出采用双层衬砌设计形式来降低水化热影响。以重庆丰都高填方明洞为研究背景,采用数值模拟方法研究了双层衬砌明洞的水化热及安全性,并探讨外衬与内衬厚度比例对结构的影响,结果表明:(1)双层衬砌结构可明显减少水化热释放,在各种层厚比下,衬砌工后内部温度最高降幅达到38%,温度应力极值的降幅可达53%;(2)相比整体式衬砌,双层衬砌设计基本不影响结构安全性;(3)双层衬砌的层厚比对结构的安全性影响极小,最大影响程度仅有2%;(4)推荐采用1∶1的外衬内衬厚度比,可在不影响安全性的前提下最大程度降低水化热影响。

Research on Feasibility of Bi-layer Lining Adopted in the Design of High-fill Open Cut Tunnel

The thickness of monolithic lining adopted in high-fill open cut tunnel is often over 2 m and may result in cracks due to hydraulic heat and affects the structure safety. The bi-layer lining is specifically proposed to solve this problem. Based on a high-fill open cut tunnel in Fengdu,the hydration heat of bi-layer lining and its safety are analyzed by way of numerical analysis and the influence of the thickness ratio between the outer lining and the inner lining on the hydration heat and the safety of lining are also analyzed. The conclusions are as follows:( 1) bi-layer lining receives much less hydration heat than monolithic lining,the limit temperature stress increase my reach 38% and the limit temperature stress decrease 53%;( 2) compared with the monolithic lining,the bi-layer lining imposes almost no impact on the structure safety;( 3) the thickness ratio of bi-layer lining does little impact on the safety of structure,and the maximum impact is only 2%;( 4) the thickness ratio of outer and inner lining is suggested to be 1 ∶ 1 to offer maximum hydration heat reduction and maintain the safety of lining at the same time.