Research Of The Stability And Reliability Of Surround Rocks In The Process Of Large-span Tunnel's Construction

Large-span tunnels have gradually increased at home and abroad, but large-span Tunnels with small net span are rare in cities. Therefore, thinking about these factors such as construction safety, reliability, reducing impacts on the neighboring buildings in the process of design and construction and so on, we must study the stability of surrounding rocks of large-span tunnels with small net span in cities. At the same time the stability of bysmalith should be thought about in the process of the construction of large-span tunnels with small net span, because it has important influences on the stability of the entire tunnels. So this article studies the stability of large-span tunnels with small net span and the reliability of bysmalith. Specific contents are as follows:①This paper introduces factors that effect on the stability of surrounding rocks of tunnels, including stresses due to dead weight and the tectonic stress.②This article summaries stress distributions about different cross sections of circular tunnels, oval-shaped tunnels and oval tunnels and presents impacts of invert excavation and overbreak and underbreak excavation on tunnels.③According to geometrical damage mechanics, micromechanics, continues media mechanics and viscoelasicity fracture mechanics this paper explores mechanical constitutive equation of damage rocks, does MTS mechanical uniaxial and triaxial experiments about wall rocks of Daping tunnel through site samplings and puts sandstone mechanical constitutive equation of Daping tunnel.④This paper has the numerical analysis on the no widening areas of Daping tunnel using 2 D-σnumerical software, and analyses correct of the numerical analysis through comparing with monitoring data, further explores the numerical analysis on three broad bands of Daping tunnel.⑤Based on demands of design the paper analyses the reliability of bysmalith of three broad bands of Daping tunnel using the numerical analysis, and critical short separation of bysmalith of every broad band using the reliability.