| Weak surrounding rock has become a large proportion of in the construction of highway tunnels so far. Weak surrounding rock always has the characteristic such as well developed joints, high and complicated ground stress and so on. People do not have a clear understanding of the characteristics of surrounding rock and deformation mechanism during the construction process of short-interval and weak surrounding rock tunnel at before. Therefore, it is of great significance to study on the deformation characteristics of weak rock tunnel. This paper mainly studied on the deformation mechanism of weak rock tunnel and balance and stability theory of surrounding rock and supporting structure system. In terms of ADECO-RS, the research had showed the relationship of extrusion deformation and advanced convergence deformation and convergence deformation. In accordance with data monitored in the field with regression analysis, the method of displacement back analysis was adopted to realize the goal of determining ?. FLAC3D was used to learn about the characteristic of weak rock and neighborhood tunnel under different lateral pressure coefficient. Ultimately reach the following main conclusions:(1) In accordance with data monitored in the field with regression analysis, determine equations of the best temporal curve of vault subsidence and horizontal clearance convergence were U=T/(0.1154+0.0271×T) and U=39.5276×e(-2.4498/T). Calculate ultimate displacement value were 36.96mm and 39.53mm. The final value of lateral pressure coefficient ? was 1.1305 by twelve times iteration convergence algorithm. The accuracy of convergence met the requirement. The computing result had a margin of error of 20.95%. The value of objective function was 31.4 less than 31.7.(2) Deformation of surrounding rock along the axial direction of tunnel excavation showed a weakening trend. The relation of extrusion deformation and axial distance were linear. When lateral pressure coefficient was less than 1.0, extrusion deformation and top and bottom advanced convergence deformation were linear, but horizontal advanced convergence deformation was not. When lateral pressure coefficient was 1.0, the relationship of extrusion deformation with both top and bottom and horizontal advanced convergence deformation were linear. When lateral pressure coefficient was more than 1.0, extrusion deformation and horizontal advanced convergence deformation were linear, and it had more significant linear effect than with top and bottom advanced convergence deformation.(3) Careful consideration should be given to the larger deformation of weak rock before applying lining. Numerical experimentation determined the supporting time of lining after surrounding rock had developed adequate self-supporting capacity. The experimental results showed that deformation of weak rock before applying lining almost reached 1/3-2/3 of ultimate displacement value. When lateral pressure coefficient was 1.0, lining stiffness was designated as 10.5GPa, at appropriate supporting time, so that it could be provided with sufficient pre-supporting resistance. Give full play to self-supporting capacity of surrounding rock, and prevent large deformation of weak rock.(4) The relation of extrusion deformation and advanced convergence deformation were almost linear, and advanced convergence deformation determined the numerical size of convergence deformation. After applying lining, convergence deformation of surrounding rock in the rear of tunnel face brought down 50%, and advanced convergence deformation of surrounding rock in front of tunnel face brought down about 25%, and extrusion deformation put down almost 10%.In the rear of tunnel face within the scope of one meter, deformation of surrounding rock occurred a sharp change. As a result of fixed end effect of tunnel face and earth stress field, the displacement direction of rock in front of tunnel face could become opposite.(5) Compared with the existing tunnel, twin-track tunnels caused that displacement of surrounding rock in inner sidewall decreased, while displacement of outer sidewall increased, and displacement increment of inner sidewall was less than outer sidewall. The displacement increment value of both vault and invert increased with the increase of lateral pressure coefficient. When lateral pressure coefficient was 0.5, the curve of displacement increment had an obvious symmetry. When ? was less than 0.5, the displacement increment absolute value of vault was more than the invert in the same distance. When ? was more than 1.0 and equal to 1.0, the displacement increment absolute value of invert was more than vault in the same distance.(6) Compared with the twin-track tunnels, the curves of horizontal displacement variation and vertical displacement variation disturbed by the following tunnel had an obvious symmetry. When ? was less than 0.5, surrounding rock deformation of twin-track tunnels excavation, was basically the same as the following tunnel disturbance. Relative to twin-track tunnels excavation, right sidewall and tunnel vault produced relatively large displacement variation. Extrusion deformation was not the same with each other under different lateral pressure coefficient. When ? was 0.5. extrusion deformation was the most minimum. Increased with ?, lateral pressure coefficient and extrusion deformation were similarly linear. |
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