Study On The Design And Rapid Construction Technology Of Highway Tunnel Prefabricated Invert Structure

In recent years,prefabricated structures have been widely used in the construction of overground and underground projects due to the advantages of fast construction speed,easy control of project quality,and simple maintenance in the later periods.At present,the construction of highway tunnels has entered an vigorous development period.In the face of complex engineering geological environment,the traditional cast-in-site tunnel inverted arch structure has problems such as low construction efficiency,difficult construction quality control,and inadequate maintenance,which lead to the cracking of the bottom drum of the inverted arch,the rupture of the lining structure of the inverted arch,and the occurrence of diseases such as the pavement churn and water.The road prefabricated tunnel lining structure is a new direction for the development of tunnel construction technology,which is conducive to saving energy,reducing construction pollution,and improving labor productivity,quality and safety.At present,the application and research of prefabricated inverted arch structures in highway tunnels are less.In this paper,numerical calculation,BIM and 3D laser scanning new technologies are used to study the design and construction of tunnel-assembled inverted arch secondary lining and filling structure,which achieved the following results:(1)Based on the classic "load-structure model",The finite element software ANSYS is used to establishes the calculation model of the overall lining structure of the tunnel,and numerically calculates the lining of the tunnel in different surrounding rocks and different burial depths.The analysis shows that the basic stress characteristics of the lining structure of the invert arch of the highway tunnel are: in the condition of different surrounding rock classification and different burial depths,the distribution rules of the internal forces(bending moment,shear force,and axial force)of the lining structure of the inverted arch of the tunnel are basically the same: mainly bear the effect of axial force,bear less shear force,and bear less bending moment at local positions.The bending moment of the middle part of the inverted arch is small,the bending moment of the two sides is large,and there are positive and negative bending moment change sections(four bending moment zero positions),which concluded the horizontal block of the inverted arch secondary lining structure is feasible.(2)Considering the mechanical characteristics of the tunnel inverted arch structure and the hoisting and lifting conditions of the construction,the block scheme of the prefabricated inverted arch and the filling structure is proposed from the two aspects of the open hole section and the dark hole section of the tunnel.The block scheme is compared and analyzed in terms of force,engineering economy,construction speed,mechanical equipment,construction organization,safety and environmental protection,and the optimal block scheme suitable for the open and dark sections is obtained respectively.(3)The 3D laser scanner is used to scan the excavation section of the inverted arch of the tunnel to obtain the point cloud data,and the point cloud model and the tunnel design model are compared and analyzed to obtain the deviation data.The excavated section of the inverted arch is trimmed to match the prefabricated standard blocks of the inverted arch structure to ensure that the blocks can be accurately installed in place.(4)BIM technology is used to carry out 3D visualization modeling of tunnel inverted arch and filling structural blocks,and the structural blocks are visually pre-assembled,and the construction process of prefabricated inverted arch and filling structure is determined.(5)Design the inverted arch and filling structural section of the open cut tunnel section in practical engineering,and briefly introduce the key technologies such as construction block prefabrication,base treatment,and structural waterproofing.