Sealing Performance of New Solidified Materials: Mechanical Properties and Stress Sensitivity Characterization of Pores

Abstract

Borehole-sealing solidified material plays a significant role in improving sealing quality and enhancing gas drainage performance. In this study, the MTS815 electro-hydraulic triaxial servo test system and MR-60 NMR test system were adopted to conduct triaxial compression control experiment on the coal sample material, concrete material, and new solidified sealing material, respectively. This paper aims to analyze the difference of support effects, porosity, and stress sensitivity between those materials. Experimental results show that under the same stress condition, the stiffness of traditional concrete solidified material is the largest, while the new solidified material is the second, and the coal sample material is the smallest. Compared with the traditional concrete solidified material, the new solidified sealing material has better strain-bearing capacity and volumetric expansion capacity under each confining pressure in the experiment. The axial strain and volume increment of new solidified material is higher than those of the traditional concrete solidified material at the peak stress. Meanwhile, the confining pressure has a certain hysteresis effect on the postpeak stress attenuation. Fracture has the strongest stress sensitivity in three pore types, and its T2 map relaxation area has a larger compression than adsorption pore and seepage pore under the same pressure. The relative content of seepage pore and fracture in the new solidified material is less than that of coal and concrete samples, and the stress sensitivity of the new solidified materials is weaker than that of coal and concrete materials, thence, new solidified material will have better performance in borehole sealing. Outcomes of this study could provide guidance on the selection of the most effective sealing materials for sealing-quality improvement.

Development and Application of Water Sealing Technology for Gas Drainage Boreholes

“…As the soft coal seam easily collapses, the hole sealing device is difficult to be sent. Moreover, the hole sealing device needs to be matched with expansion cement, and the operation process is cumbersome. , The bore is sealed by inorganic materials, simple operation, low cost, have certain block of surrounding rock around the borehole fissure, but material curing slower, hole sealing time is long, cement mortar material shrinkage resistance, especially the problem of hole sealing is lax in fissure zone, lead to water, air drilling, influence the effect of gas drainage and coal injection. In addition, the cement mortar is prone to dehydration, shrinkage, and cracking in the solidification process, which makes it difficult to guarantee the hole sealing effect.…”