Abstract: To avoid deviation in the drilling trajectory during smalldiameter horizontal wireline coring drilling and drill pipe broken induced by deviation, the experience of horizontal hole drilling in long and large tunnels of various railway projects that have been completed and the rotation characteristics of horizontal hole drilling equipment in the hole are analyzed. After analyzing the working conditions of various components of the drilling tool, such as drill string, cartridge chamber, cartridge stopper, reamer, and the drill bit, as well as the deformation degree of the drilling tool after being stressed, the hole diameter structure, and the occurrence and integrity of the stratum, it is found that in addition to operating experience affecting the drilling deviation, the drill bit posture has a significant impact on the drilling deviation. Therefore, a smalldiameter wireline coring drill pipe centralizer is further developed, which has been applied experimentally in the exploration of ultradeep horizontal holes in a tunnel of a plateau railway. The application results in practical engineering show that the use of the drill pipe centralizer in smalldiameter horizontal wireline coring drilling effectively reduces the deviation angle of the drilling hole and has a good antideviation effect. However, to further rationally and effectively use the drill pipe centralizers, further experimental research should be conducted on the number of centralizers installed, spacing, and distance from the drill bit.

Key words: horizontal wireline coring drilling, hole deviation; drill pipe centralizer, deflection prevention method