Construction Technology Discussion of Ultra-long Horizontal Directional Pre-grouting Boreholes

Abstract:

In the periphery of long and deeply buried tunnels of water conservancy projects, along the tunnel axis of a wide range of fracture zones and water-rich areas, the use of the ground more than 1,000 meters of horizontal directional drilling pre-grouting ahead of the management, to achieve a good effect of the surrounding rock reinforcement and gushing water blocking, is a successful attempt in the water conservancy industry. This paper introduces the successful experience of drilling ultra-long horizontal directional pre-grouting holes with screw drilling tools in a project, and discusses the difficulties of powder removal in ultra-long horizontal drilling holes, coping with the problem of “back pressure”, the interference of strong magnetic field with the drilling measurement system, the measures of green exploration, as well as the problems of insufficient adaptability of drilling rigs, low efficiency of hard-rock drilling, and the influence of grouting on drilling in operation, etc. and the measures to solve them. and measures to solve the problems. The project has 4 main holes and 6 branch holes, the longest hole is 1427m, and the drilling workload is 8737.89m. The implementation of the project proves that the current directional drilling technology has the ability to drill accurately over long distances, which can provide a guarantee for the pre-grouting and over-treatment of the complex strata of the ultra-long tunnels and the related drilling projects.