Construction technologies of high-angle synchronous directional coring drilling for tunnel investigation

Abstract:

In order to solve the problems such as the great difficulty of cross-river tunnel investigation in alpine-gorge areas， the asynchronous high-angle precise orientation and wire-line coring， and the low drilling efficiency in hard strata， the synchronous technology of directional deflecting and wire-line coring drilling， the real-time trajectory control technology for high-angle directional holes， high-strength wire-line coring drill rods， and iron-based pre-alloy layered core bits were developed. Combined with the kilometer-level wire-line coring directional drilling equipment， a set of high-angle directional core drilling technology was explored and formed. The research results were applied to the investigation of the diversion tunnel of a major hydropower project in the western region. An ultra-deep L-shaped directional borehole was arranged on the left side of the river valley， and the following achievements were obtained： The construction task of a 1004 m curved directional core drilling deep borehole was completed with high quality and efficiency. The average monthly efficiency of the drilling rig was 197.64 m， the average core recovery rate of the whole hole was 94.35%， and the average mechanical drilling rate of core drilling was 1.46 m/h. The trajectory was well controlled. The top angle of the borehole trajectory increased from 25° to 78°， meeting the design requirements. The developed iron-based pre-alloy layered bit had obvious advantages， with a faster drilling rate and a longer service life. The faults and unfavorable geological bodies at the bottom and on both sides of the river valley were identified and exposed， achieving the geological objectives and obtaining good application results.