| Pipeline installation technology of horizontal directional drilling in rock is hotspots and problems of the field of horizontal directional drilling at the present time. It is one of the important symbols of a country's technical level in horizontal directional drilling, but its pipeline insallation technology has been less researched in China. In China there are many places where its layer is composed of rock, so it is particularly urgent and necessary for studying pipeline installation technology of horizontal directional drilling in rock. This paper is aimed at some problems about low-efficiency of pilot hole drilling in rock and the difficulty of cutting cleaning in rock. The construction technology of pilot hole drilling and reverse circulation cutting cleaning in rock have been studied systematically in the paper. The main results of the study are as below:1. The pipeline installation technology of horizontal directional drilling in rock, for the first time, has been systematically studied. The key techniques in each engineering procedure of horizontal directional drilling in rock have been theoretically studied, and it has effectively guided the practice engineering. A set of the pipeline installation technology of horizontal directional drilling in rock has been established.2. The pipeline installation technology of horizontal directional drilling by DTH percussive rotary pilot drilling in rock, for the first time, has been studied in China. And a engineering of DTH pilot hole drilling has successfully been completed. Its drilling footage is 12 meters per hour that is more than 5~10 times than of using screw motor or using double drilling tool system. The pipeline installation technology with DTH percussive rotary technology can improve the drilling efficiency and reduce the construction cost of horizontal directional drilling in rock.3. In order to ensure that the equipment in the hole is working correctly, the multiple reducing vibration measures and real-time water cooling technology have been applied in DTH percussive rotary pilot hole drilling. The multiple reducing vibration measures can enable the devices in the borehole with a very strong vibration to work correctly. And the real-time water cooling technology can maintain the ambient temperature of the equipment in hole within its normal scope.4. The reverse circulation cutting cleaning technology, for the first time, is put forward and applied in the horizontal directional drilling pipeline installation . We conducted in-deepth its theoretical study in this paper. It has been successfully applied to the horizontal directional drilling pipeline installation. The efficiency of removing the drill dregs in reverse circulation technique is several times higher than in conventional trenchless technique, so it has significantly improved the construction efficiency and reducing the construction costs. It is in epoch-making significance that its application in the horizontal directional drilling pipeline installation.
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