| With the plan of western development to have been being done, the infrastructure construction will continue to be reinforced in mountainous areas, and more tunnel engineering will be being applied. There are a great of accumulation of rocks with loose structure and poor self-stability in western region, being a typical poor geological condition. Some reserchers have done a lot of work and have achieved fruitful results about the slope stability of tunnel portal, but it still need studying further after the tunnel excavation because of that special strata usually being in a critical state under the natural state. Taking MaZhao highway project construction as the background in this paper, deeply study that constructing disturbance make the influence on deformation law and stability of surrounding rock and slope at shallow-depth portal section of Laoyingpan tunnel in Zhaotong, by the integrated use of literature reference, site investigation, theoretical analysis and numerical simulation and other methods. The major research work and achievements are listed as follows:(1) Through the collected literature and investigated data on site, systematically analyze the geological condition and engineering condition of Laoyingpan tunnel in theory;(2) Systematically expatiating on forming process, distributing region, geometric features and classification of the accumulation of rock, analyze the slop stability of accumulation of rock in theory. Then the stability of slop before tunnel portal is calculated and analyzed under the action of gravity by numerical simulation;(3) By setting different construction methods and excavation sequences, obtain the different effects that they make for deformation law and stability of tunnel and slop, with numerical simulation methods to research and analyze. The results show:the right tunnel excavated firstly overall being superior to the left done firstly; step method is compared with full section method and CD method, its stress and deformation being superior to full section method and being close to CD method, but its speed is faster than the CD method’s, which also ensure the constructing safety of tunnel and slop at some times;(4) With numerical simulation method, research effects of tunnel surrounding rock and slop made by different spatial layout of double tunnel in deformation law and stability. The results show:for vertical displacement, the optimal horizontal spacing being 25 meters, it is better to take vertical spacing and depth of the tunnel as small as possible; for horizontal displacement, the optimum horizontal spacing also as 25 meters being, the best depth being as small as possible, the vertical spacing have a little influence on surrounding rock deformation, but that of surface is greatly reduced after the first increase by it, vertical spacing as 10 meters being better by the comprehensive analysis; the importance of change of maximum shear stress and the maximum shear strain increment made by the three factors, according to the priority sequence, are vertical spacing, depth, horizontal spacing of double tunnel. |
