# Review on the Influence of Complex Stratum on the Drilling Trajectory of the Drilling Robot
## 1 Instruction
During the drying process, all saturated samples basically recovered their mechanical properties and strength in the dry state. As one of the most direct and effective technical means to prevent and control coal mine accidents and allow safe and efficient coal mining, underground drilling in the coal mine area plays a huge role in the fields of gas (coalbed methane) extraction, water hazard prevention and hidden geological factor exploration in the coal mine area, which is of great significance to ensure the safety of coal mine production, increase the supply of clean energy and reduce greenhouse gas emissions [25; 26]. In terms of prevention and control of water disasters [27; 28; 29], such as directional drilling for drainage of water from the roof of Hongliu Coal Mine, 21 directional drilling holes were completed from August 2011 to April 2012. The total footage was 9762 m, and the maximum water output of a single hole was 216 m\({}^{3}\)/h. The water volume, water pressure and water temperature of the roof aquifer changed significantly through the drainage of six directional boreholes in the test area. The effective control of roof water hazard was achieved through the drainage of directional boreholes. In the process of directional drilling for water exploration and drainage in the No. 1 well of the Carboniferous Well Coking Coal Company, due to the fact that the coal pillar in some sections was less than the specified size, the water in No. 1 Well's goal seeped into the goal in the south wing of the No. 2 well through the rock fissure, seriously threatening the safety production of the No. 2 well. Four directional boreholes were constructed from No. 2 well to No. 1 well to drain the water in No. 1 well, which eliminated the safety hazard of No. 1 well to No. 2 well. The floor grouting reinforcement directional drilling in Zhaoguyi Mine was affected by the regional geological structure and mining stress, and the waterproof floor with weak compressive strength lost its waterproof function. During the drilling and mining process, the underground directional drilling was used to reinforce the floor of Working Face 11,151, transforming the limestone aquifer into a waterproof layer, and the safe mining of the working face was effectively ensured. Directional drilling technology is applied to the exploration of geological abnormal bodies [30; 31; 32; 33], which can accurately locate the abnormal areas and provide guarantee for the safe production of the mine. For example, in order to ensure the safe production of Mengcun Coal Mine, the direction and fault distance of the DF29 fault in the working face were accurately detected by directional drilling in the 4 # coal seam, which ensured the normal progress of roadway excavation and coal mining in the later stage. The 11 # coal seam in Sangshuping Coal Mine was mined under pressure. The structure of the top of the Ordovician limestone layer on the floor of the 11 # coal seam and the development of the karst fissure were explored and grouted to ensure the safe tunneling of the roadway. The traditional rotary drilling technology and equipment in coal mines have the characteristics of an uncontrollable drilling track, small coverage and low drilling utilization, which cannot meet the requirements of efficient and accurate drilling in coal mines. With the development of complex formation detection technology and measurement while drilling (MWD) technology, combined with the research on the impact mechanism of drilling trajectory, real-time accurate control of drilling trajectory can be achieved, improving the level of coal mine underground drilling technology and equipment.