Because natural conditions, geological environment, climate conditions, etc. are relatively complex and changeable, the construction difficulty of highway engineering is increased to a large extent. Tunnel engineering is a particularly important project in expressway construction. In recent years, as expressway construction extends to mountainous areas, the number of tunnel projects has also increased greatly. Tunnel construction has a certain degree of danger, concealment, and technology, so it is easy to encounter various technical problems in the process of construction. In addition to being restricted by the technical level of tunnel design, management level, materials and other factors, highway tunnels are prone to various diseases, among which lining cracks are more common. Lining cracks and diseases will affect the quality of highway tunnels to a large extent. Therefore, it is necessary to pay more attention to the diseases. Only by analyzing and finding out the cause of the disease can we formulate more targeted remediation measures and realize effective treatment.
Overview of Lining Cracks
Lining cracks are a very common type of disease in highway operations. When a highway tunnel lining cracks, it is easy to cause water leakage in existing tunnels. If the cracks are serious, it may even cause a sharp drop in the bearing capacity of the highway tunnel structure. Caused the road tunnel instability, collapse and other safety accidents. It can be seen that lining cracks are prone to have many adverse effects on highway tunnels. The distribution of lining cracks is more diversified, such as vertical cracks, longitudinal cracks, diagonal cracks, combined cracks and so on. Different lining cracks in different distribution patterns require different treatment methods. In order to achieve a better control effect, it is necessary to have a full understanding of the different distribution patterns of cracks.
Vertical cracks mainly refer to vertical axis cracks that occur in highway tunnels. The distribution of cracks occurs more in construction joints, settlement joints and the junctions of different addresses. For example, vertical cracks are prone to occur in the middle part of each slab molded concrete. Vertical cracks generally start from the bottom of the side wall, and continue to the end of the arch waist. The cracks are basically symmetrical at the left and right side walls, and some of the cracks will extend upward until they meet the vault. Longitudinal cracks mostly occur in the part of the tunnel vault and arch waist. Relatively speaking, the number of longitudinal cracks is less than the number of vertical cracks, but the harmfulness of longitudinal cracks is greater than that of vertical cracks. With the further development of longitudinal cracks, it is very likely that the tunnel lining will break or even collapse.
Oblique cracks mostly occur in the location of the tunnel arch and side walls, and oblique cracks are also harmful. Combination cracks refer to the cracks formed by any combination of the above three types of cracks. Combination cracks generally show Y-shaped and X-shaped cracks. When the number of cracks is too large, it is easy to form network cracks when the crack distribution is added. .
Analysis of Causes of Lining Cracks in Expressway Tunnels
There are many reasons for the cracking of highway tunnel lining, such as natural environment, materials, construction, etc., which are prone to cause lining cracks. In order to better prevent and treat lining cracks, it is necessary to understand the causes of lining cracks. The following section analyzes the causes of lining cracks from the aspects of design, construction, and materials.
1. Design reasons
Compared with other pavement engineering, highway tunnel engineering is more complicated, and it has higher requirements in terms of construction, design, technology and so on. As far as tunnel design is concerned, it includes overall line layout, entrance and exit settings, construction and excavation plan, etc. Any omission in any of the design links will affect the quality of tunnel construction and cause lining cracks. In the design of highway tunnels, the problem of unreasonable structural design is more prominent. Designers often pay attention to the design of structural forces and surrounding rock stability, and ignore structural design and detailed design. For example, the design of the longitudinal drainage pipe of the tunnel did not consider a separate location, which could easily lead to water intrusion and cracks in the lining.
2. Reasons for construction
Highway tunnel construction has higher requirements on technology and technology. Scientific and advanced construction technology can ensure the quality of tunnel construction and improve the reliability of the overall tunnel. As far as the current highway tunnel construction is concerned, due to the limitation of construction technology level, construction environment and construction technology, some shortcomings and problems are prone to occur during the construction process, and improper construction technology will cause tunnel lining cracks. The construction quality directly affects the overall quality and operation efficiency of the tunnel. If there are quality problems in the construction, it will easily cause the tunnel to appear disease in the subsequent operation process.
3. Material reasons
In the construction of highway tunnel engineering, materials are a particularly important subject. Whether the quality of materials passes the customs directly affects the construction quality of the tunnel engineering and the subsequent operation efficiency. For example, during the construction process, the large error in the measurement of raw materials during concrete production will affect the stability and reliability of the tunnel lining, and it will be prone to cracks in the lining.
Treatment measures for cracks in highway tunnel lining
1. Preventive measures for lining cracks
The treatment of lining cracks is more to take measures to repair and strengthen afterwards. Although repairing and strengthening can also achieve effective treatment effects, it will affect the appearance of the tunnel and the overall operating efficiency to a certain extent. Therefore, for highway tunnel lining cracks, the key to its treatment lies in the prevention and control of cracks. The most important thing for prevention and control is to take effective measures during the design and construction process. For example, in terms of lining structure design and tunnel excavation methods, it is necessary to strengthen construction management and improve the technical level in order to reduce the occurrence of tunnel lining cracks in the later period. During the construction of highway tunnels, by improving the quality of construction and strengthening construction management, the quality and efficiency of the later operation of the tunnel can be ensured to a large extent. This is also the fundamental method of treating tunnel lining cracks, that is, controlling and preventing cracks from the source. happened.
2. Lining crack repair technology
For lining cracks that have occurred, effective repair techniques must be adopted for treatment. According to different types of lining cracks, different crack repair techniques need to be selected. For example, for some small, non-hazardous cracks, spray concrete reinforcement can be used to repair. For some complex, wide, and hazardous cracks, it is necessary to choose the most reasonable repair technology according to the actual situation. In the case of serious diseases, it is even necessary to consider the method of partial dismantling or lining dismantling for disease treatment. Lining crack repair techniques are more diversified, such as steel belt reinforcement, arch reinforcement, anchor rod reinforcement, basin concrete reinforcement and other methods for repair and management. For the phenomenon of severe damage to the tunnel lining structure, peeling off and falling blocks, the method of sleeve arch reinforcement can be used for disease treatment. The arch reinforcement has good durability and bearing capacity, and is a very effective method of structural reinforcement. When the local cracks in the tunnel are large in scale and the cracks are more harmful, it is necessary to consider the way of lining removal and replacement for disease treatment.
3. Strengthen the maintenance and repair of highway tunnels
In the process of putting the highway tunnel into operation, many serious lining cracks were further developed due to the lack of early control. Therefore, during the operation of expressway tunnels, it is necessary to strengthen the regular inspection, maintenance, and maintenance of the tunnel, which can not only improve the operating quality of the tunnel, extend the service life of the tunnel, but also find the diseases and problems in the tunnel in time. , And then take timely and effective measures for governance. By strengthening the maintenance and repair work of highway tunnels, the lining cracks can be effectively prevented from developing further, and the diseases can be strangled in the budding period.
In summary, the lining cracks of expressway tunnels have a direct impact on the normal operation and overall quality of expressway tunnels. Therefore, in order to better ensure the safe and reliable operation of highway tunnels, it is necessary to pay more attention to lining cracks. It is difficult to treat tunnel cracks, and the treatment cost is relatively high. If the construction team does not have professional treatment technology and the treatment equipment is simple, it will be difficult to achieve the ideal treatment effect. Therefore, the key to the treatment of tunnel lining cracks should be to strengthen the construction and management during the construction period, while paying attention to the structural design of the tunnel. For lining cracks that have occurred, methods such as shotcrete reinforcement, steel belt reinforcement, and arch reinforcement can be used to treat them. Only by thoroughly solving the lining cracks can the normal and safe operation of highway tunnels be guaranteed.