What are the common forms of tunnel support? The common forms of tunnel support mainly include the following:

　　1. Shotcrete Support: High pressure concrete is sprayed onto the tunnel wall to form a strong protective layer. Shocked concrete can quickly cover the surface of surrounding rock, seal rock cracks, prevent weathering and water erosion, and increase the overall stability of surrounding rock. It can be used as temporary or permanent support.

　　2. Steel Arch Support: A frame structure made of steel or steel grating, installed inside the tunnel to provide support for the surrounding rock. Steel frame support can be used alone or in combination with shotcrete to form a more robust composite support system.

　　3. Rock Bolting or Cable Anchoring: By drilling holes in the surrounding rock, inserting high-strength steel bars or steel strands, and fixing them with materials such as cement slurry, the internal stress of the surrounding rock is transmitted to the deep and stable rock mass, thereby improving the self-supporting capacity of the surrounding rock.

　　4. Lining Support: A permanent structure made of poured concrete or other materials after tunnel excavation, used to withstand long-term ground pressure and water pressure, ensuring the stability and durability of the tunnel. The lining can be cast-in-place concrete, prefabricated concrete pipe segments, or masonry structures.

　　5. Prefabricated Support: Assemble precast concrete slabs, arches, and other components inside the tunnel to form a support structure. This method is suitable for tunnel projects with good conditions and can accelerate the construction progress.

　　6. Grille Support: A grid like structure welded from steel bars or steel bars, usually used in combination with shotcrete to form a lightweight support system, suitable for initial support of weak surrounding rock.

　　7. Soil Nailing: Drilling holes in soil or soft rock, inserting steel bars or pipes, and tightly bonding them with the surrounding soil through grouting to form an effect similar to anchor rods, enhancing the overall stability of the soil.

　　8. Freezing Method: In special circumstances, such as crossing aquifers or weak strata, artificial freezing of the strata can be used to temporarily harden them for tunnel excavation and support.

　　9. Grouting reinforcement: Injecting cement slurry or other chemical slurry into the surrounding rock to fill cracks, improve the compactness and bearing capacity of the surrounding rock, is a commonly used auxiliary support method.

　　These support forms can be used separately or in combination according to specific engineering requirements and geological conditions to achieve the best support effect.