The quality of the tunnel depends on the quality of the process, and the quality of the process depends on the quality of the excavation, initial support and drainage and drainage, etc. The better control of the initial support and drainage and drainage can strengthen the supervision, so the focus is on the quality of the excavation, which depends on the quality of the excavation The quality of drilling and blasting means that in theory, the quality of the initial support without subsequent over-excavation is guaranteed. Therefore, the quality of the tunnel depends largely on the quality of drilling and blasting.
(1) The crack should be penetrated and have a certain crack width on the ground. For medium-hard rock, the crack width should not be less than 1.0cm; the crack width of hard rock should reach about 0.5cm; but when the width of the crack on soft rock reaches more than 1.0cm, the shock absorption effect is not significantly improved, and some field tests should be done to Lee sums up experience.
(2) The unevenness of the pre-cracked surface after excavation should be greater than 15cm.
(3) The retention rate of blast hole traces on the pre-cracked surface should not be less than 80%, and the rock near the blast hole does not show serious blast cracks.
The construction of the tunnel and the gate are also very important. The excavation and support of the cave entrance, the slope, and the tunnel should be excavated and layered from top to bottom, and the outside of the cave, temporary prevention, and drainage must be carried out first to make the surface water smooth. Avoid surface water washing the slope.
When necessary, artificial slope repair is adopted to prevent over-excavation and reduce disturbance to adjacent sections of the opening; excavation exposed slopes shall be designed and protected in time to reduce the exposure and weathering of surrounding rocks, and support shall be followed closely. On the high side and the slope, if it is not timely, safety cannot be guaranteed, and a lot of manpower and resources will be wasted.