隧道初期支护结构受力特性及适用性研究

复合衬砌是目前隧道支护结构的基本形式,即由初期支护与模筑混凝土二次衬砌结构复合而成。按照新奥法原理进行设计和施工时,在围岩稳定性较差的条件下,初期支护通常采用由喷射混凝土与型钢钢架或格栅钢架及锚杆组成的组合结构,但在采用型钢钢架还是格栅钢架支护问题上一直存在不同的观点,其争论的焦点是对其支护结构性能及其适应性的认识,核心则是“支护-围岩”作用体系中支护结构的作用及其演化过程特点,而在不同围岩及工程尺度条件下其作用效果也有所不同。为此,该文首先通过型钢钢架和格栅钢架的室内性能试验,对两种支护结构的受力特性、破坏过程及演化特征、极限承载力及变形量等进行了系统的研究；然后通过有限元组合结构进一步分析了型钢钢架和格栅钢架的受力特性、极限承载力和变形特性；最后结合京沪高铁金牛山隧道现场试验,取得了两种支护类型下围岩荷载释放规律和压力分布特点,并分别给出了型钢钢架与格栅钢架的特点和最佳适用条件。该成果对于澄清支护作用机制以及隧道初期支护设计和施工具有重要的理论价值和指导作用。

STUDY ON MECHANICAL CHARACTERISTICS AND APPLICABILITY OF PRIMARY LINING USED IN TUNNEL

Composite lining is commonly adopted for a tunnel support nowadays, which is designed and constructed according to the new Austrian tunneling method. When tunneling under unfavorable geological conditions, the primary lining composed of shotcrete, steel rib/lattice girders and cables is typically adopted. However, there exist arguments on the applicability of the steel rib and the lattice girder. Thusly, laboratory experiments are first performed to test the mechanical characteristics of the steel rib and the lattice girder respectively. Then finite element analyses are conducted to study the mechanical characteristics of the steel rib and the lattice girder separately. Finally, on-site experiments at Jin Niushan tunnel located at Beijing-Shanghai high-speed railway line are implemented to test these two kinds of support structures. The stress release characteristics of the surrounding rock and the stress distribution characteristics along the steel rib and lattice girder are revealed. Moreover, the support characteristics and the optimum installation time of the steel rib and the lattice girder are elaborated. The research is helpful to clarify the support characteristics of the primary ling composed of different kinds of steel sets. It is also helpful to facilitate the further tunnel design as well as tunnel construction.