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

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

　　2. Steel Arch Support: A frame structure made of steel or steel grid is installed inside the tunnel to provide support for the surrounding rock. Steel Arch Support can be used alone or in combination with shotcrete to form a more solid 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 pouring and fixing with materials such as cement slurry, the stress inside the surrounding rock is transferred to the deep stable rock mass, thereby improving the self-bearing capacity of the surrounding rock.

　　4. Lining Support: After the tunnel is excavated, a permanent structure made of concrete or other materials is poured to withstand the ground pressure and water pressure for a long time to ensure the stability and durability of the tunnel. The lining can be cast-in-place concrete or prefabricated concrete segments or masonry structures.

　　5. Prefabricated Support: Use prefabricated concrete slabs, arch blocks and other components to assemble in the tunnel to form a support structure. This method is suitable for tunnel projects with better conditions and can speed up the construction progress.

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

　　7. Soil Nailing: Drill holes in the soil or soft rock, then insert steel bars or steel pipes, and grout them to make them tightly bonded with the surrounding soil, forming an effect similar to that of anchor rods, enhancing the overall stability of the soil.

　　8. Freezing Method: In special circumstances, such as crossing an aquifer or soft stratum, the stratum can be artificially frozen to temporarily harden it, facilitating tunnel excavation and support.

　　9. Grouting Reinforcement: It is a commonly used auxiliary support method to inject cement slurry or other chemical slurry into the surrounding rock to fill cracks and improve the density and bearing capacity of the surrounding rock.

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