Study On The Mechanical Characteristics Ofthe Lining Structure Of A Single Hole Doublelayer Dark Dug Tunnel

With the development of civil engineering technology,after solving the technical problems such as spreading and fire fighting,the double layer tunnel has become a better form of tunnel construction because of the contradiction between the rapid increase in traffic volume and the more limited space in the construction of the city.However,for the design and construction of double deck tunnel,there is no reference to the corresponding normative documents,and lack of relevant engineering experience and theoretical research support.In this paper,through the method of finite element simulation and theoretical analysis,the stress characteristics of the section,lining parameters and lining of the lining of a single hole and double layer urban road tunnel are systematically studied.The above conclusions are based on the current standard and standard,the scheme is feasible and the parameters are reliable,which can be used to demonstrate the urban double deck road tunnel and the similar underground workers.The construction of the course provides a certain basis and reference.The results of this paper are as follows:1.Under the span of 1 and two lanes,the horseshoe shape is the best section,and the horseshoe shape is the best section under the three lane span,and the horseshoe shape and the circle are hard to distinguish under the four lane span.With the increase of span,the advantage of horseshoe shaped section is smaller than that of circular section,and both of them have advantages in the four lane.It can be concluded that with the increase of the span,the circular section will be more advantageous than the horseshoe shape and become the best section.2.Through the mechanical characteristics of the lining structure under concrete conditions,the mechanical characteristics of the shotcrete and the two lining of the double layer tunnel are studied.It is found that the two sides of the shotcrete are the dangerous parts of the structure,and the extreme value of the axial force,the extreme value of the shear force,the extremum of the bending moment,the extreme value of the main stress and the plastic breaking are all in the place,and the initial support is the lining of the lining.The main body of the structure carrying the external load is the two lining,which plays a role of safety reserve while bearing a small amount of external load.3.Through the study of the influence of the changes of lining parameters under different surrounding rock on the mechanical properties of lining,through a large number of data,the changing trend of lining displacement,axial force,shear,bending moment,principal stress and the plastic failure of surrounding rock with lining parameters is obtained.It is found that the thickness and strength of lining can be increased.The effect of lining is improved,but the influence of lining thickness is more obvious.The worse the quality of surrounding rock is,the more obvious the trend is.4.The influence of the partition board on the overall lining of the tunnel is studied.Through the force contrast of the middle partition board,it is found that the partition board not only has the partition space,bearing the upper lane and the driving load,but also can participate in the overall lining of the lining.The displacement of the two sides of the lining at the two sides of the lining is contained,and the lining of the two sides of the inverted arch is effectively improved.The phenomenon of stress concentration.5.According to the study of the shape of the middle partition,the result shows that the stress concentration near the inverted arch of the polygon section is the weakmost,and the most outstanding protection effect is on the most dangerous area of the inverted arch,but the polygon section is separated from the plate in the polygon section.The distribution of body stress is poor,and there is a certain stress concentration in the middle partition;the arch section has the most excellent protection effect on the middle partition itself,and the displacement of the partition plate is far less than the former two,but the stress concentration phenomenon in the arch section is the most obvious;the mechanical performance of the rectangular section is poor.6.The design scheme of a double lane highway double deck tunnel project in Chongqing is a little weaker than the study of the three lane double deck tunnel,but the difference is small.The finite element calculation model is established according to the specific working conditions of the project,and the calculation results conform to the relevant specifications.That is,the rationality of the design is verified,and the correctness of the research conclusion is verified.