Characteristics of argillization and adhesion and influencing factors of drilling cuttings in borehole of roadway in soft argillaceous surrounding rock

Borehole drilling is an essential step for the anchoring control of roadway surrounding rock of coal mines. The efficiency of bolt installation and bonding effect between resin-rock interface are closely related to the quality of borehole formation. When borehole drilling in argillaceous surrounding rock, the phenomenon of drill sticking and drill jamming exists, and it is difficult to discharge the drilling cuttings when occurring argillization, which is the bottleneck restricting rapid and high-quality formation of borehole. Therefore, by using theoretical analysis and laboratory test methods, this paper studied the mechanism of argillization and adhesion and influencing factors of the drilling cuttings in the borehole of soft argillaceous surrounding rock containing kaolinite. The results show that the oxygen atoms with strong electronegativity on the surface of kaolinite crystal layer adsorb hydrogen atoms in water molecules to form hydrogen bonds, and constantly absorb water molecules to expand the water layer, and finally form a "water film" of multi-layer water molecules. The adsorption of water by kaolinite clay on the surface of drilling cuttings makes the drilling cuttings also coated by "water film". At the same time, with the continuous dissolution of non- argillaceous minerals and the swelling of drilling cuttings particles, the spacing between drilling cuttings particles is reduced, which is easily captured by van der Waals forces between each other 's water films, so that they aggregate to form aggregates. The main reason for the adhesion of drilling cuttings is that the drilling cuttings is subjected to the electrostatic force generated by its own "water film" and the surface of the drill bit and the interfacial tension of the overall structure formed by the "water film" on the surface of the drill bit. The electrostatic force plays an important role in the process of argillization and adhesion of drilling cuttings. The degree of argillization of drilling cuttings decreases with the increase of particle size of drilling cuttings, solid-liquid ratio, stirring speed and time of drilling tool, and K ion concentration. Acidic solution will also inhibit the mudding of drilling cuttings. The significant degree of each factor on the inhibition of drilling cuttings argillization in the test range is in the order: solid-liquid ratio, particle size of drilling cuttings, stirring time, stirring speed, pH value and K ion concentration. The countermeasures to suppress the argillization of drilling cuttings are put forward. such as adjusting the structure of the drill bit, increasing the liquid inlet pressure, increasing the rotation speed of the drilling tool, and adjusting the composition of drilling fluid can weaken the degree of argillization of argillaceous drilling cuttings and water, and reduce the adhesion to the drilling tool. The research results can provide a theoretical reference for improving the quality, efficiency and anchoring support effect of the boreholes in soft argillaceous surrounding rock.