Modern Tunnelling Technology,2013年50(6):66-71 ISSN：1009-6582
[ Zhang, Huijian ; Kong, Chao ; Qiu, Wenge ; Man, Shuai ] Key Laboratory of Traffic Tunneling, School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China
Adjacent tunnels - Limit analysis - Model tests - Quantitative method - Rock mass stability - Structural safety - Support parameters - Tunnel construction
The key to the construction of tunnels and other underground works is to ensure rock mass stability during construction and structural safety during operation. While an appropriate quantitative method to assess the rock mass stability is lacking in China at present, a numerical limit analysis of rock masses was adopted to quantitatively describe the stability of a rock mass during tunnel construction using the Hongyancun tunnel group as an example. The results of the limit analysis and indoor model test were that the construction consequences were optimized based on the safety factor of the rock mass stability and the rationality of the support parameters was verified, the development law of the rock mass fracture plane during the tunnel group construction was obtained, and the limit analysis was deemed appropriate to assess rock mass stability during tunnel construction.
Extensive research and investigations on the durability of existing railway and highway tunnels indicate that the majority of tunnels suffered from various degrees of defects induced by durability deficiencies. There are many reasons that can contribute to the lack of durability of the major structure of a tunnel and the root cause proves to be the philosophy of design. The previous design standards of mountain tunnels were generally alow level and did not sufficiently consider tunnel structure durability, which could only be regarded as strength-oriented design rather than comprehensive performance -based design. Many misconceptions involved in the philosophy of tunnel design include failing to pay sufficient attention to the geological and hydrological conditions, inappropriate concrete material, failing to strictly control the initial cracking of concrete, single composition and poor gradation of the cementitious material, thicker second linings with excessive stiffness and poor toughness, etc. Regarding the design deficiencies in the structure durability of mountain tunnels, the following main measures are proposed: multiple composite cementitious material is to be used to prepare concrete, composite cementitious material is distributed by the batching plant, the primary support is to be strengthened while the second lining thickness is reduced, and proper fiber is to be added to the concrete.