As the structure of the tunnel support system, the subway bolt is an important part of the tunnel structure; It is the outer barrier of the tunnel, which acts as a resistance to soil pressure, groundwater pressure and some special loads. The subway bolt is assembled while the tunnel is advanced, and the quality of the segment is directly related to the overall quality and safety of the tunnel, affecting the waterproof performance and durability of the tunnel. The geometry of subway bolt products is arc plate-shaped, and it is generally assembled in blocks. Metro bolts are used in the construction of tunnel shield method, after the shield machine cuts the soil forward, several segment bolts are assembled around the inside of the tunnel, and then bolted to tighten to form the lining of the tunnel and withstand the earth pressure.
Excavation can effectively control the ground settlement, reduce the impact on the ground buildings and do not affect the water surface traffic when excavating underwater, etc., the segments are combined together to form a pipeline, which is designed as a straight or certain arc fastening connector, that is, subway segment bolts. Metro bolts are divided into ring and longitudinal. Some designs have the same loop and longitudinal specifications. Some designs use two specifications in the ring and longitudinal direction, or even two strength classes. In general, circumferential segment bolts are longer in length than longitudinal segment bolts.
Metro segment bolts are a special fastener used by shield boring machines to connect and fasten their segments during tunnel boring. Through this subway bolt connection, several arched segments can be connected into a circle, thereby supporting the entire tunnel surface, which is also called subway segment connection bolt
China fastener standard GB/3098.1-2000 this specification. In fact, the name of subway bolts, only in the rapid development trend of the subway in the past two years, this is a general term for the subway needs anchor bolts, but the actual meaning it represents is the high regulations on the anti-corrosion characteristics of stainless steel plates and commodities! In addition, subway segment bolts are used in the shield structure of the subway, the length is different, subway bolt dealers, there are bends and straight, the actual need to see the provisions of each new project, the basis is all to test the stainless steel plate material to 45 steel more common, the grade to 6.88.8 level more common, in the anti-corrosion with 150H copper accelerated salt spray test or 1200 hours neutral salt spray test dominant.
Metro bolts from the past engineering practice shows that the quality of segment assembly directly affects the waterproof, safety and appearance of the tunnel, therefore, in order to effectively improve the waterproof quality of the segment, the segment assembly work should be grasped from all aspects in the construction. Based on this, in order to improve the overall rigidity of the tunnel and improve the stress state of the segment, the installation of the segment adopts the staggered assembly method, adopts a small capping block, and first lapes 2/3 in the radial direction, and then pushes into the 1/3 method of longitudinal pushing.
The common surface treatment of subway segment connection bolts are: hot-dip galvanized (hot-dip zinc), Dacromet (commonly known as: zinc-based chromate), powder zinc infiltration, multi-compound powder zinc infiltration, etc. The quality of the surface treatment of segment bolts is crucial. Because the segment bolts are installed underground, they play the role of connecting the segments. The environment in which it is located is humid, which is easy to cause corrosion of bolts and rust. Therefore, if the surface treatment of the bolt fails to meet the design requirements, resulting in rust and other phenomena such as rust during the use of the subway bolt, corrosion to the inside of the bolt will affect the mechanical properties of the bolt and its tensile strength.