Design of multi-channel continuous cable duct for double-bit self-balancing drilling system

The problems, such as low drilling efficiency, large disturbance to the hole wall and long assistance time of tripping caused by the “long arm jurisdiction” drive of the ground drilling rig to the underground drill bit, are faced during the drilling rescue of mine disaster. In order to solve these problems, the bionic self-balancing continuous cable duct drilling technology of double drill bit without drilling rig was proposed, the design of the multi-function continues cable duct is one of the key and challenging aspects of this technology. In terms of the technology, a multi-functional continuous cable duct with built-in channels of power supply, signal and chip removal is required. Therefore, the multi-channel continuous cable duct was designed according to the needs of the self-balancing drilling system from three aspects: function, structure and parameters. For continuous drilling, the multi-channel cable duct should have the functions of mud circulation, electrical and signal transmission, and electromagnetic shielding, as well as sufficient strength and good elasticity. Further, the parameters of the outer diameter of the armoured cables for the cable duct, as well as the inner and outer diameters of the inner and outer pipes, were designed, and the upward reflux rate of drilling fluid in the annulus was calculated. The calculation results show that the diameter parameters of the inner and outer pipes of the cable duct meet the requirements of the minimum upward reflux rate. Therefore, force analysis was conducted for the key components of the cable duct with the theoretical calculation and numerical simulation in combination. Meanwhile, the tensile strength, compressive bending strength and extrusion strength of the outer pipe wall were checked. The results show that the multi-channel continuous cable duct is designed with reasonable structure and reliable performance, which could meet the technical requirements of the bionic self-balancing drilling system of double drill bit without drilling rig. Generally, a safe, reliable and fast mobile multi-channel continuous cable duct technology and method is provided for the bionic self-balancing drilling rescue work of the double drill bit without drilling rig for mine disaster.