| In recent years, both highways and railways in our country are developing rapidly towards the direction of high flow and high speed, whereupon a large number of tunnel projects are coming into being and becoming gradually the controlling engineering of the whole line. Tunnel lining, as the major part of support structure of the whole tunnel, its carrying capacity and durability determine the security and stability during the whole period of tunnel construction and operation.Up to now, with the great development of tunnel construction, the design of tunnel structure is no longer a problem for us. However, what we are facing is how to solve problems such as rapid construction, security support, stability and deformation of tunnel rock and durability of tunnels. Besides, as the main materials of support structure in tunnel and underground engineering construction, (sprayed) concrete has its own defects such as brittleness and low tensile strength. Therefore, tunnel builders have no choice but to do better jobs by means of laying tunnel mesh to improve the properties of (sprayed) concrete so as to get a good supporting effect in the lots with poor geological conditions. But this method is still not good enough out of the following considerations. The construction process of laying steel mesh is very complex and it often requires a long time, so a timely support can not be achieved. Besides, cavities will easily appear behind the mesh and thus hidden danger of security will exist accordingly.Fortunately, applying SFRC (steel fiber reinforced concrete) to tunnel construction will be an effective way to solve those problems mentioned-above. Through model test and by using numerical simulation, this paper intends to explore the support behavior of SFRC as tunnel lining and optimize its primary support by substituting sprayed concrete+steel mesh with the main conclusions and contributions as follows:1. Through on-site production and indoor load, a series of four points bending tests are carried out to investigate the toughness of SFRS (Steel Fiber Reinforced Short Crete). By analyzing its toughness and carrying capacity after cracking, the appropriate dosage of SFRS are finally determined.2. The plastic hinge is used to stimulate the bending properties of SFRC after cracking. By numerical calculation, support curve of support structure of SFRC is obtained, which provides reference for support design by using SFRC.3. The geometry similarity ratio (1:20) and the gravity similarity ratio (1:1) are set as the basic similarity ratio to achieve a similarity of physical and mechanical parameters within a elastic range, and thus to carry out the indoor model test of support structure of SFRC with the final purpose of investigating the characteristics of the mechanical behavior of steel fiber reinforced concrete lining. This is the first indoor model test both at home and abroad which aims at studying the support structure of SFRC in tunnel with similarities to a large scale.4. Taking a highway tunnel as the research background, the software ANSYS is applied to calculate and analyze at the same time the internal force of support structure and the stress and strain field of SFRC with the final purpose of drawing a conclusion that SFRC can be used as separate support to replace (Sprayed) concrete with steel mesh or grille arch. |
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