2. The main body of the station is constructed by combining frame cover excavation with open excavation. In order to deal with the contradiction between foundation pit safety and construction progress, combined with the surrounding rock conditions, the cover excavation method is boldly combined with hanging foot piles, that is, the supporting form of hanging foot piles and rock bolts is adopted in the better range of rock strata at the west end of the station, and the hanging foot piles bear the roof and pavement loads; Long pile anchor cable support is adopted in the poor section of the eastern stratum. At the same time, the concrete-filled steel tubular middle column is used in the design, and the inverted seam of the column adopts double-beam structure, which not only saves the construction period, facilitates the construction, reduces the cost, but also minimizes the impact time on traffic and pipelines.
3. Qingdao has a typical soil-rock binary composite stratum structure. Generally speaking, the granite bedrock with strong, moderate and slightly weathered degree is covered with Quaternary soil layers with different thicknesses. The thickness of Quaternary overburden along Line 3 varies from 0 to 20 meters, and each station section passes through various weathered rocks and soil layers, which is very uneven in the longitudinal direction and generally presents the characteristics of "soft on the top and hard on the bottom". Therefore, the foundation pit of Qingdao subway open-cut station, the construction method of underground excavation station and the interval tunnel have their own uniqueness.
4. Dunhua Road Station of Metro Line 3 is deeply buried due to the longitudinal slope of the line, and the main body of the station is located in the weathered granite layer. In order to make full use of the characteristics of Qingdao slightly weathered granite, such as high strength and good integrity, and highlight the characteristics of Qingdao, the station is designed as a tower-column station with separated island platform. The tunnel between the two platforms is supported by natural rock pillars, and the tunnel is permanently supported by bolting and shotcreting. All the equipment rooms are externally hung, and the station halls at both ends are separated from the platform and connected by long inclined channels.
5. The subway line passes through the main city of Qingdao, and the surrounding buildings are dense, and it also passes through many cultural relics protection buildings to avoid the influence of train vibration on buildings and residents' lives after the subway is opened and operated. This project fully considers the vibration influence and adopts various international advanced vibration control technologies to minimize the vibration influence caused by subway operation. Among them, Qingdao Metro Group, together with universities and research institutes, has improved the sprayed polymer damping materials used in the field of national defense and military industry, carried out application tests in subway projects, obtained scientific and technological achievements with completely independent intellectual property rights, developed new technologies and materials dedicated to vibration and noise reduction of subway tunnels, and obtained national patents. The material has the advantages of convenient construction, good vibration reduction effect, low engineering cost, environmental protection and non-toxicity, and can also be used as a tunnel waterproof layer to realize "one thing has multiple uses".
6. In the construction of Qingdao subway, some sections have to pass through bad geological sections such as river bed and water-rich sand layer. When excavating tunnels in these unfavorable strata, there will be problems such as collapse, water gushing and sand gushing, and the construction progress is slow and risky, which may even lead to the settlement of ground buildings and roads. In the construction of Metro Line 2, this kind of stratum is constructed by shield method to minimize the risk of construction and surrounding environment.