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Causes of collapse in tunnel projects and remedial measures: Collapse to varying degrees has occurred in both under-construction and completed tunnel projects, causing significant harm to their construction and operation. Therefore, it is very important to analyze the reasons and address them promptly. Causes of landslides 01 Geological factors: Geological conditions are the fundamental causes of landslides. Crossing fault fold zones, as well as severely weathered fractured zones and deposits that are prone to landslides, is challenging. Groundwater is often also an important factor; an abundance of groundwater can lead to landslides. 02 Design factors: Geological exploration requires careful and thorough consideration. When insufficient information is available, one should avoid inappropriate locations. During the design process, the geological conditions were not accurately assessed, and the impact of unfavorable geology on the tunnel was not fully considered. 03 Construction factors: Construction is the direct cause of collapses. An insufficient understanding of the geological conditions leads to the use of inappropriate construction techniques, such as excessive material usage, inadequate or unreliable support, or an excessive exposure time of the surrounding rock. Additionally, if inappropriate methods for dealing with the surrounding rock are chosen and no other remedial measures are taken, this can result in the collapse of the surrounding rock. http://img.civilcn.com/d/file/zhishi/gcgl/2020-03-04/2cc1f6e4f1d99e527334c05dede472d9.jpg Governance measures: 1. In the event of a landslide, quickly rescue the construction workers and reinforce the areas that have not collapsed, in order to prevent the landslide from spreading further and to prepare for clearing the debris. At the same time, it is necessary to determine the situation of the collapse, investigate the extent of the collapse and the current condition of the surrounding rock after the collapse, as well as the causes and nature of the collapse, the patterns of gaps, and the conditions at the collapse site. 2. The collapse mass has not yet filled the tunnel completely; there is a long interval between pauses in collapsing or further collapses, allowing workers to enter the collapsed area to observe and take action, which constitutes a minor collapse. The landslide mass blocks the tunnel; it is on such a large scale that it is impossible to observe the situation, and the landslide continues without stop, with more material continuously adding to it. As a result, construction workers are unable to enter the area affected by the landslide – this is a major landslide. 3. The treatment of landslides is carried out in accordance with the principles of \"treat minor blockages first and deal with severe collapses later\" and \"address water issues first when dealing with landslides\". (1) Minor collapses are common during tunnel construction; in the gaps resulting from such collapses, it is generally necessary to provide support first and then clean up. First, the collapsed areas and the openings caused by landslides need to be stabilized. At this point, temporary supports can be placed on the collapsed mass, after which the debris can be removed, with new columns being installed as the removal progresses. If the collapse cavity is deep, multi-layer scaffolding can be used for support; the top layer of scaffolding should be pressed tightly against the walls of the cavity. If conditions permit, shotcrete can also be used as temporary support to stabilize the collapse. In the case of large collapses, it is not possible to support the collapsed area; when the size of the collapse cannot be determined, it is also not attempted to find out, in order to prevent further collapse as cleanup takes place and the extent of the collapse from expanding rapidly. Therefore, the approach of \"passing through the collapse\" is adopted, that is, moving through the collapsed area. The construction sequence for passing through collapses is to provide protection first and then carry out excavation. First, after reinforcing the supports and lining at the end of the collapse, the plug method is generally used for construction. Depending on the hardness of the debris resulting from the collapse, materials such as wooden planks, steel bars, or railway tracks can be employed for these plugs. Under the protection provided by these plugs, the debris is removed, and sturdy supports are installed promptly. When expanding the structure, plugs also need to be driven in horizontally, with supports being added as the expansion proceeds. The section passing through the collapse area should pass through it from the arch top and the upper cross-section, and then construction should proceed downward. Construction is carried out using the upper and lower adit method; only when collapse occurs in the upper section is it necessary to reinforce the lower support, and supports must be installed in the upper area to prevent further collapse. After that, debris removal or passage is carried out through the upper adit. A top-to-bottom collapse is an extreme form of large-scale collapse; in such cases, it is also necessary to deal with the sinkholes that appear on the surface, securing these sinkholes to prevent them from expanding further. Dig drainage ditches around the collapse site. Prevent surface water from accumulating in the collapse pit, and fill the cracks around it with clay-like materials. A rain shield should be installed above the entrance of the pit to prevent rain and snow from entering the collapsed area. (2) To address landslides, water management comes first; the flow of water can exacerbate the progression of landslides. Therefore, when dealing with landslides, it is necessary to strengthen water prevention and drainage measures, as well as take appropriate actions to divert groundwater from the affected area. (3) Treating large collapses is time-consuming and labor-intensive. To accelerate the construction progress, it is possible to use bypass adits to go around the collapsed area, allowing the treatment of the collapse to proceed simultaneously with the construction of the main tunnel. However, care should be taken when selecting a bypass adit scheme. Prevent further collapses in the bypass adit, or the spread of collapses into the bypass adit. The surrounding rock in the collapsed section is extremely unstable, and the pressure on it increases; therefore, the lining structure needs to be strengthened accordingly. Reinforcement measures should also be taken for the surrounding rock, along with proper drainage systems.