隧道湿喷纤维高性能混凝土单层永久衬砌研究

PERMANENT SINGLE-LAYER TUNNEL LINING BY FIBRE-REINFORCED HIGH PERFORMANCE SHOTCRETE AND WET-MIX METHOD

针对复合式衬砌在施工、承载和防水方面存在的问题,按照挪威隧道工法(NMT)的原理和技术要求,以昆石(昆明—石林)高速公路小团山隧道为工程实例,从结构设计、抗渗性、耐久性、经济性和施工技术等方面系统地研究了隧道湿喷纤维高性能混凝土单层永久衬砌技术,并在小团山隧道施作了30m长的C45湿喷纤维高性能混凝土单层永久衬砌代替原设计的复合式衬砌。小团山隧道工程实践证明,湿喷纤维高性能混凝土单层永久衬砌代替复合式衬砌,变被动防水为主动防水,防水效果良好;同时,工程量小,施工速度快,节约造价。

In the light of the drawbacks met in the double-layer lining, the permanent tunnel lining by single-layer fibre-reinforced high performance shotcrete (HPS) and wet-mix method is studied systematically. Xiaotuanshan tunnel of Kunshi (Kunming to Shilin) expressway is chosen as an engineering example. Based on the principles and technical demands of New Austrian Tunnelling Method(NATM), this tunnel lining was the double-layer lining in its former design. This double-layer lining has three layers practically. The outer layer, first lining, is sprayed concrete lining with 3 m long rockbolts, whose thickness and compressive strength are 15 cm and 20 MPa, respectively. The inner layer, second lining, is cast-in-situ concrete lining, whose thickness and compressive strength are 35 cm and 25 MPa, respectively. A waterproof membrane is installed between the first and second linings. In this study, based on the principles and technical demands of Norwegian Method of Tunneling (NMT), the double-layer lining of this tunnel is changed into single-layer fibre-reinforced(steel fibres/steel fibres+polypropylene fibres) HPS lining with rockbolts by wet-mix method. There are 4 sets of joints in surrounding rocks of this tunnel, and there is a little water in these joints with water pressure of 0.25-0.30 MPa. Compared with Barton's Q-system, surrounding rock's Q of this tunnel is equal to 0.0396. Based on Barton's graph of Q-system for permanent support of tunnels, the thickness of the single-layer fibre-reinforced HPS lining and its rockbolt length are designed as 20 cm and 3 m, respectively. By field test, 28 d-compressive strength of HPS lining for this tunnel is 45 MPa. There is no leakage for more than two years on the surface of this single-layer fibre-reinforced HPS lining. Compared with the double-layer lining, the cost of the HPS lining is reduced by 12.39%.