Model Test Of Expressway Tunnel For Maintenance And Reinforcement Strategies

Due to design, construction, geological condition as well as tunnel structures, management work is required for built expressway tunnels and such tunnels in which diseases occur require reinforcement. However, expressway tunnels have large sections and busy operation conditions, which result in difficult maintenance and high maintenance costs. In order to reduce reinforcing difficulty and maintenance costs, studies on such aspects should be carried out.Aiming at section characteristics of present expressway tunnels and relying on Appraisement of Long-term Security of Expressway Tunneles and Study on Maintenance and Reinforcement (Key task project in scientific and technological research of Chongqing Science and Technology Committee), studies are put upfor the basic ante type------Bijiashan Tunnel. This paper analyzes causes resultingin diseases in expressway tunnels and tunnel diseases and maintenance reinforcement are classified into four grades. According to such grades, diseased tunnels are reinforced.This paper takes geometric similarity ratio 1:25 and bulk density similarity ratio 1:1 as basic similarity ratio and carries out indoor plane model test. Such tests realize complete similarity in elastic range for controlled physical mechanical parameters.In model tests, influence of caverne in arch, insufficient lining thickness and different construction methods on bearing capacity of tunnel structures are studied in such surrounding rock as Grade II , III and IV. At the same time, tunnel structures with different defects are loaded until diseases occur in tunnel structures; different reinforcements are applied according to different diseases and different disease grades; after diseased tunnels are reinforced, load is sequentially applied up to structure damage in order to study bearing capacity of reinforced tunnel. According to test results, disease forms are attained for such structures with different defect forms; influences of defect forms on bearing capacity of tunnel linings are analyzed; and applicability of such reinforcing methods as backfill caverne in arch, reinforced bolts, reinforced internal surface, reinforced arch rib/inner lining, or their combined reinforcing mode, are put forward. Finnaly, this paper brings forward agreeable countermeasures of maintenance and reinforcement for different defect forms and different ground stress fields.