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.