Analysis of Crack Initiation and Propagation Thresholds of Inclined Cracks under High-Pressure Grouting in Ordovician Limestone

Control of the grouting pressure within critical for crack propagation in Ordovician limestone can not only ensure grout penetration length, but also prevent risk creating an artificial water channel. Based on fracture mechanics theory, a formula was proposed to calculate mixed mode I-II cracks limestone. The necessary conditions tilted opening, rationality existing empirical value maximum allowable investigated based mechanical model. RFPA2D-Flow numerical simulation software used evaluate deduced theory. research results show that theoretical calculation agrees with results; when initiation occurs, exceeds perpendicular stress overlying rock; greater density rock mass, initiation; side coefficient ≥1, dip angle increased and tended decrease; at is 2.0–2.5 pw, which will cause failure crack.