Numerical Test On The Stability Of The Surrounding Rock And Support System For The Rectangular Tunnel With Arch Crown

The ideas of NATM are commonly accepted by tunnel engineers in the developed country. The construction method is also introduced during the early 1960s in China, but up to now the tunnel design method still stays at the 1950s' 'rock-load theory' phases, furthermore, the systematic quantitative study on the tunnel stability is little reported. In order to apply the theoretical analysis rather than the empiricism only into the tunnel design as soon as possible, the Austrian program FINAL is used to perform numerical tests to study the characteristics on the tunnel stability under various factors such as rock material, the initial stress, the burden depth, the tunnel span and the ratio of high and span. The comparison between the numerical test and the in-site measurement validates the reliability of the numerical tests.Through the numerical tests in this paper, some qualitative features are obtained for the surrounding rock stress field after excavation, the rock displacement field, the rock plastic region, the stresses and deformation of the shotcrete which are affected by several factors such as the primary stress field, the burden depth, the tunnel span and the ratio of high and span in the different surrounding rock. The quantitative properties of the rock stress value, the displacement value, the stress of the shotcrete, the bolts force, etc. at the top arch, the middle arch and the middle point of the straight wall are also discussed. At the same time, the differences of these characteristics in different surrounding rock are analyzed. The applicable scope of the traditional method and the project analogism is evaluated, too. At last, some conclusions are attained as follows. The displacement values in numerical tests are very near to those from in-site measurements and their features are also identical. The displacement values increase with the depth increasing and the worse the rock mass is, the more sharply the values increase. These prove that the numerical tests are reasonable and available in the underground opening.