Abstract:
In the southern part of Ordos Basin, the main coal seam is Jurassic Yan 'an Formation. Due to the large thickness of coal seam the water-conducting fracture zone of the coal seam leads to the pore-fissure aquifer of the Cretaceous Luohe Formation sandstone overlying the coal seam, resulting in a huge amount of water inflow in the mine, which seriously threatens the mine production. In order to effectively control roof water in thick sandstone layer, a series of roof grouting and water plugging engineering tests have been carried out in this area. However, since conventional cement grouting can only fill large cracks, electrochemical grouting tests have been developed to strengthen the sealing effect of micro-pore cracks in sandstone. Luohe Formation sandstone in Ningzheng Mining area is selected as the research object, and sandstone model materials are made by using river sand and cement according to the proportion of rock types in Luohe Formation. Two sets of electrochemical grouting tests are carried out in the sandstone model materials with calcium chloride and sodium silicate grout. The grout is injected at the cathode, and the voltage used for each grouting is 40 V, and the grout injection rate is maintained at a constant speed 10 mL/min, the test running time exceeded 2 h.The feasibility of electro-chemical grouting in fractured pore sandstone is verified. It is found that calcium chloride grout in solution is more suitable for electrochemical grouting of porous sandstone than collidal sodium silicate grout. The calcium ions in the solution of calcium chloride migrate under the action of electric field and have chemical reactions, forming colloid in the micropores of sandstone. Energy consumption per unit grouting volume of calcium chloride solution needed for 0.09 (kW·h)/L. Metal electrode loss is serious in the grouting process, and will cause Fe pollution to aquifer. In the future, it is necessary to carry out research on how to select environmentally friendly electrodes with low loss.