Special construction of open cut tunnel and portal technology programme
The 07 contract section of Wanli Expressway contracted by our department is 5.096km long from K42+845 to K47+940.5. There are two tunnels along the line, including one long tunnel, namely Liujiayan Tunnel; One short tunnel, namely Taiji Tunnel. 3.2.2 Main Project and Quantity Table 6 Overview of Open cut Tunnel and Portal Project No. Tunnel Name Location Starting and Ending Stake No. Open cut Tunnel Length (m) Construction method of tunnel portal form affected by topography 1. Left line entrance of Taiji Tunnel ZK44+065 ～ ZK44+080 15 open excavation without bamboo cutting 2. Left line exit of Taiji Tunnel ZK44+330 ～ ZK44+340 10 bias end wall type half bright and half dark 3 Right line entrance of Taiji Tunnel K44+082 ～ K44+097 15 open excavation without bamboo cutting 4 Right line exit of Taiji Tunnel K44+346 ～ K44+355 9 bias end wall type open excavation 5 Liu Jiayan Left line entrance of tunnel ZK44+735 ～ ZK44+739 4 Bias end wall open excavation 6 Left line exit of Liujiayan Tunnel ZK44+705 ～ ZK45+710 5 Bias end wall open excavation 7 Right line entrance of Liujiayan Tunnel K44+845 ～ K44+855 10 Bias end wall open excavation 8 Right line exit of Liujiayan Tunnel K45+695 ～ K45+700 5 Bias end wall semi open and semi concealed table 7 Project quantity of each tunnel open tunnel and portal Table No. Tunnel Name Location Portal Excavation (m3) Intercepting Ditch (m) Temporary Protection (m2) Open Tunnel (m) Backfill (m3) Permanent Protection (m2) 1 Entrance of Taiji Tunnel 3626.09 132.09 881.3 30 2454 881.3 2 Exit of Taiji Tunnel 5883.72 166.48 850 19 882.55 850 3 Entrance of Liujiayan Tunnel 5330.77 111.72 850 14 1056.3 850 4 Exit of Liujiayan Tunnel 3918.07 229.4 425 10 479 425 3.3 Natural geographical characteristics 3.3.1 Topography, formation lithology and structure (1) The entrance of Taiji Tunnel is located in the middle and upper part of the natural slope in the east of Modaoxi River, with the slope aspect of 340 ° and the slope toe of 20 °~39 °. The micro landform at the entrance is terraced terrace, which is the former site of residential houses, and has been restored as farmland. The tunnel enters the tunnel in a straight line. The intersection angle between the tunnel axis and the slope direction is about 19 °, and the intersection angle with the rock stratum trend is large. The overburden layer of the slope is gravelly soil and sandy gravel soil with a thickness of about 17.0m. The underlying bedrock is sandstone and shale of the Middle Jurassic Xintiangou Formation. Shale is soft rock, and sandstone is relatively soft rock. The entrance is structurally located at the northwest wing of Longju anticline. The attitude of the rock stratum is 340 °∠ 48 °. The interlayer combination is general. The strongly weathered layer is 6.7m~7.8m thick. The moderately weathered rock mass is relatively complete, with medium thick layers. Two groups of fractures are developed in the rock mass: ①, 70 °∠ 86 °, ②, 142 °∠ 33 °. The underground water is poor, and a small amount of water may seep out in drops after rain. The soil mass of the slope at the portal section is stable, and the natural slope toe is 5 °~15 °. According to the survey, there is no obvious deformation sign under the natural state and long rain, and no adverse geological processes such as collapse, landslide and debris flow are found.
