Deformation Characteristics And Multi Factor Quantitative Analysis Of Neighborhood Tunnels In Mountainous Region

The neighborhood tunnels are frequently employed in highway engineering due to limits imposed by objective conditions such as landform,geological conditions,and route selection criteria,as well as constraints imposed by construction technology and project cost concerns.However,in comparison to conventional tunnels,the neighborhood tunnels are more prone to collapse or other geological disasters during construction in the tunnel’s shallow buried area,owing to its complex stress condition and ease of bearing bias pressure in the mountain area.It is critical to investigate the surrounding rock deformation law and the excavation response of the shallow buried section’s neighborhood tunnels.As a result,this thesis uses the Huangjiakuang tunnels in Weihai City,Shandong Province as the research object,the collapse accident of the tunnel’s shallow buried section as a starting point and conducts research on the construction deformation of the shallow buried section of the neighborhood tunnels using theoretical analysis,on-site monitoring,numerical simulation,and statistics.The purpose of this article is to discuss the reasons for tunnel collapse and the effect of numerous factors on tunnel deformation.This thesis’ s primary research content and conclusions includes the following:(1)Analysis of tunnel monitoring data collected on-siteThe surrounding rock pressure of Huangjiakuang tunnels is theoretically evaluated and a monitoring strategy is proposed with considering the influence of tunnel construction.According to the analysis of field monitoring data for Huangjiakuang tunnels and advance geological prediction,the proportion of grade V surrounding rock in the face area is relatively high,while the proportion of grade III and IV surrounding rock is relatively low;According to the law summary and characteristic analysis of tunnel deformation data from various surrounding rock levels,the surrounding rock deformation of Huangjiakuang tunnels can be classified into two stages: growth stage and stable stage,with the growth stage further divided into rapid growth stage and slow growth stage.Tunnel deformation under grade V surrounding rock is greater than tunnel deformation under grade III or IV,and the time reaching a stable state is longer.By comparing the difference in surface settlement at the entrance and exit at various buried depths,it is determined that the second tunnel has a significant effect on the deformation to first tunnel,and the influence of the second tunnel on the first tunnel gradually decreases with increasing buried depth.(2)Simulation of a tunnel collapse accident in a shallowly submerged sectionUsing the collapse in the shallow buried portion as a starting point,this study analyzes the causes of the collapse and concludes that the nearby tunnel excavation,the nature of the surrounding rock,and over excavation were the primary causes of the tunnel collapse accident.The finite element software is used to simulate a direct surface collapse accident during construction,to determine the deformation characteristics of during construction.The displacement and stress response of the collapse accident were found by examining the tunnel displacement and stress field of numerical simulation results.(3)Analyzing The factors causing tunnel deformation by control variables.The control variables of overbreak height,staggered distance of tunnel face,and varied gradients of elastic modulus of surrounding rock are studied using a finite element model in conjunction with the code requirements.The deformation curves for various operating conditions are determined using the stratum settlement,intercalated rock,and tunnel deformation assessment criteria.Extract and summarize surface and tunnel deformation data,determine the response law of various components to the tunnel and stratum,and determine the eigenvalues of each factor.The correlation degree of three factors on tunnel deformation is determined using the statistical method of grey correlation analysis-entropy weight,and the correlation degree is ranked from big to small to determine the quantitative influence of each element on tunnel deformation.