The general geological conditions of gravel accumulation tunnels are poor, the rock formations are broken and weathered seriously, and construction safety problems are common. Ordinary tunnel pipe shed reinforcement methods will have problems such as stuck drilling and hole position deviation. After a period of verification, the self-drilling soil nail pipe shed has fully proved that it can pass through the broken and accumulated rock mass and successfully complete the construction.
Reinforcement Method of Gravel Accumulation Tunnel
During the construction of the gravel accumulation tunnel, due to the poor stability of the surrounding rock, the vibration generated by the construction may cause problems such as the falling of the gravel, which has great difficulty and safety risks. In order to ensure the stability of the accumulation, a comprehensive field investigation and test verification are required before construction.
If the ordinary pipe shed is used for grouting reinforcement, due to the crushing of the surrounding rock and the large gap between the crushed stones, there will be continuous falling of the crushed stones, stuck drilling, hole position deviation and collapse during the construction process, which will cause the construction progress to lag. . self-drilling soil nails combine bolt drilling, bolt grouting and anchoring. There are various types of drill bits, which can be selected according to the geology of gravel accumulation.
The self-drilling soil nail has the characteristics of high construction efficiency, large anchoring force, good anti-corrosion performance, and convenient operation. It can be drilled in different rock layers, and high-pressure grouting can be realized at the same time. In weak, broken and loose rock formations, a better grouting anchoring effect can be formed, and the requirements for the working platform are small, and the reinforcement effect and construction progress can be well controlled.
Construction Process of self-drilling soil nail
Get the Drilling Rig Ready
The platform should be built before the construction of the bolt to facilitate the construction of the drilling rig. The position of the drilling rig should be precisely arranged according to the design, and a clear mark should be made. The positioning of the drilling rig should be accurate, adjust the drilling angle, align the drilling direction, then start the drilling rig, move the head slowly, and carry out drilling construction.
Drilling
The drill bit of the self-drilling soil nail should be aligned with the hole position, and the drilling rig should be started. In the early stage of drilling, the speed needs to be slowed down, and the drilling method of multi-circle and less impact should be adopted. During the drilling process, the drilling direction should be grasped at all times to prevent the drill bit from deviating when encountering rocks or rock formations with uneven strength.
Connect the Anchor Rod
The self-drilling soil nail has a full-length unbonded external thread on the outside, which can be cut and connected arbitrarily. It needs to be connected through a matching size connecting sleeve. The connecting sleeve has an internal thread, which can connect the two anchors. The two ends are connected together by screwing.
Grouting Reinforcement
self-drilling soil nails are used to reinforce the surrounding rock with cement slurry, the water-cement ratio is 1:1, the grouting pressure is 1~1.5MPa, and the final pressure is 2MPa. During the grouting process, part of the grout will be lost along the pores of the surrounding rock below, so a second grouting is required to ensure that the pressure meets the design requirements.
The above is the answer to the question of how to strengthen the gravel accumulation tunnel. The self-drilling soil nail has simple construction and fast construction efficiency, and has low requirements for the installation site. The process of following the tube casing.