Study On Construction Mechanical Behaviors And Construction Technology Of The Shallow Bias Tunnel With Large Span And Small Spacing

With the rapid growth of the national economy, As the traffic demand increases sharply, there are a large number of three-lane highway tunnels, as a representative of the small spacing and large span tunnel. With large-span flat section and interaction of the double holes construction, the whole stability of surround rock of the small space and large span tunnel is relatively poor, especially on shallow burying bias section and more shallow, more broken and weathering rock, load capacity is extremely poor and bias, stress distribution of surrounding rock, the support structure and deformation is very complex, it lead to crack easily, seepage, even landslide and stability. But our country is a mountainous country, during route selection of highway, the tunnel meet the mountain slope extremely, so the optimizing design and construction of the shallow bias tunnel with large span and small spacing has become a key technical problem.This paper introduces research situation of the optimizing design and construction of the shallow bias tunnel with large span and small spacing and combine the existing research results, based on the shallow burying bias section in the Linwu tunnel,use the combined regimen of finite element numerical analysis and monitoring data analysis, having research and discussion for the problem in the design and construction of the optimizing design and construction of the shallow bias tunnel with large span and small spacing, the main work and conclusions are as follows:1. The analysis of engineering shallow buried bias large-span small interval tunnel in the definition and characteristic of the shallow cover and bias, big cross and small interval of the factors such as mutual coupling effect, make its construction mechanics behavior is very complex, safety construction control is difficult.2. Analysis of a single circular hole tunnel excavation and support the process of surrounding rock stress field and tunnel construction characteristics of the surrounding rock stress state, and put forward the corresponding characterization method and expression and to explore the construction safety control evaluation.3. Using the ABAQUS finite element software tunnel shallow bias surface reinforcement and the use of surface pre-grouting and on the cover of reinforced concrete cover to reinforcement both construction program of construction of numerical simulation to study in the shallow bias small interval tunnel construction process surrounding rock stress and strain and supporting structure internal force and displacement of the changes in its rule. The results of the study show that:due to bias affect the surrounding rock largest stress cast is buried side spandrel arch with the shallow side of the foot, and buried side arch foot and the shallow side of the spandrel super-shallow side of the tunnel will be a stress concentration or stress increases; horizontal displacement of the surrounding rock and play a key role in the stability of surrounding rock, shallow side of the tunnel and surface vertical upward displacement; supporting structure spandrel upward overlying shallow weak parts of the surrounding rock deformation, leading to the supporting structure instability and destruction; underwent tunnel construction on the first hole is very obvious.4. Through the numerical simulation results, study the difference of construction of the mechanical behavior that between before the reinforcement measures wether were set to the bias of the shallow surface of small spacing cross tunnel, to assess the project reinforced the program’s effectiveness.5. Analysis of the problems encountered in the Lin house tunnel ultra-shallow bias of the actual construction and project measures, the experimental data and numerical results were compared, put forward a guiding significant conclusion of the actual construction, and provide a reference for future similar projects.