Soil nailing wall support is a widely used technique in foundation pits, slopes, and tunnel engineering. It involves driving a certain number of anchor bolts (or nails) into the soil or rock mass and combining them with shotcrete, reinforcing mesh, and other materials to form an integrated support structure. This method enhances the stability of the soil or rock mass, preventing slope sliding or foundation pit collapse.

　　The construction process of soil nailing wall support includes the following steps:

　　1. Slope Surface Preparation: The soil should be excavated in layers and sections. The depth of each excavation layer should match the vertical spacing of the soil nails, with the excavation level being 200mm below the nail positions. After each layer of soil is excavated, it should be trimmed to remove any protruding soil and compact any loose soil to ensure a smooth surface for the shotcrete application.

　　2. Initial Shotcrete Layer Application: The shotcrete should be applied from top to bottom, with the nozzle kept at a distance of 0.8 to 1.5 meters from the surface. The spray direction should be perpendicular to the surface, with a minimum thickness of 40mm for each application. Accelerators may be added to the shotcrete to speed up the setting process and prevent the concrete from sagging.

　　3. Soil Nail Positioning, Drilling, and Hole Cleaning: Before drilling, mark the nail positions according to the design requirements. Begin drilling slowly, and once a certain depth is reached and the soil layer is stable, proceed at a normal speed. The drilling process should not disturb the surrounding soil layers. After drilling, clean the holes using high-pressure air or water.

　　4. Soil Nail Placement: Cut the main reinforcement bars according to the design length plus 20cm. The outer end should be bent into a 90-degree hook of 20cm. Centering supports should be welded every 1 to 2 meters to prevent the main reinforcement from deviating from the center of the soil nail. The structure of the supports should allow the grout to flow freely during grouting. The grouting pipe should be tied together with the main reinforcement and positioned about 0.5 meters from the hole bottom. The end of the soil nail should be connected to the reinforcing mesh and reinforcing bars within the surface layer.

　　5. Grouting: Pressure grouting should be used. The grout pipe should be inserted 250-500mm from the hole bottom, and a grout stopper should be set at the hole opening. After filling the hole, maintain pressure for 1-2 minutes. The grout pipe should be slowly and evenly withdrawn during grouting, ensuring that the outlet is always below the surface of the grout, allowing any air in the hole to escape. The grout mix ratio and pressure should be controlled according to design specifications.

　　6. Reinforcing Mesh Installation: The reinforcing mesh should be installed layer by layer along with the soil nails. The protective layer thickness should be no less than 20mm, with an overlap length of no less than 30 times the diameter of the reinforcing bars, and the single-side weld length no less than 10 times the diameter. The mesh should extend to the ground surface and protrude 0.5 meters beyond the slope line.

　　7. Installation of Drainage Pipes: Insert horizontal (slightly downward) drainage pipes with a length of 400-600mm and a diameter of no less than 40mm into the back of the support surface layer. The outer end of the pipe should extend out of the support surface. The spacing between drainage pipes can be 1.5 to 2 meters to effectively drain water from the soil behind the shotcrete layer.

　　8. Shotcrete Application: After the reinforcing mesh and soil nails pass inspection, begin applying the shotcrete. The nozzle should be kept perpendicular to the surface. If the surface layer thickness exceeds 100mm, the shotcrete should be applied in layers, with the first layer being no less than 40mm thick. The next layer should only be applied after the previous layer has set, with an overlap width of at least twice the layer thickness, ensuring that the joints are staggered. After the final set, the shotcrete surface should be kept moist by spraying water within 2 hours to maintain proper curing.

　　The construction process of soil nailing wall support is a systematic engineering approach involving geology, mechanics, materials science, and requires the construction team to have extensive experience and professional skills to ensure quality and safety.