Research On The Technology For Construction Of The Double-Arch Tunnel In The Adverse Geological Section

The double-arch tunnel has strong adaptability of the topography. In a number of special terrain conditions, it is a very effective structure of the tunnel, especially the short tunnel (usually less than 500m) constructed in mountainous areas or in the short-shallow hill areas, to be often used with larger advantages. However, from most of double-arch tunnels built in all parts of the country, it has some questions in its construction such as the longer construction period, higher cost and quality issues etc.. The problems what are mentioned above are more prominenet, specially in the the adverse geological conditions.Tongyoushan Tunnel is a double-arch tunnel with complex surrounding rock and construction conditions.Its import of 180m is the shallow-biased, soft surrounding rock, and other adverse geological condistions. The horizontal distribution of surrounding rock is a typical "inside-good, outside-bad" state—the outside is the V-class surrounding rock and the inside is theⅣ-class.Because of Tongyoushan Tunnel is not constructed from the two ends of the tunnel but only from its import, it had very stongly pressure in the construction period. Based on the study of the construction technology of Tongyoushan Tunne in its adversegeological setion, the engineering practice and numerical simulation analysis show that:(1) To the longer and adverse geological condition of the double-arch tunnel, through a series of technical measures to make full use of middle-hole and side-hole as the channel of construction, can be divided into a number of parts to be constructed what can be relaxed the pressure of the constution period due to one-way construction and the adverse geological conditions.(2) The numerical simulation analysis shows: we can give priority to build the inside of the tunnel", which is conducive to the construction and structural safety and uses more efficient construction methods.(3) According to the differences of the surrounding rocks conditions, both sides of the main tunnel can be constructed by different methods of construction and support that can improve efficiency of construction and save projects investment. Such as Tongyoushan Tunnel, the left-hole and right-hole was used different supporting measures that ware proved to be viable and successful. In addition, the three-dimensional numerical simulation to the actual construction process is also adopted in the paper analyzing the effect of longitudinal space with the construction in the adverse geology section of the tunnel. A reasonable distance is presented about of the digging between right-tennel and left-tennel and of the construction between lining and the early support.