Control effects of joint grouting and precision blasting on blasting damage in deep rock masses

With the expansion of underground construction, deep rock mass excavation technology has attracted growing attention, as complex geology and developed joints in deep rock masses challenge rock mass integrity and stability. This paper, based on blasting excavation at Meizhou Pumped Storage Power Station, studies cavern displacement and surrounding rock damage from blasting in jointed rock masses via on-site vibration tests and ultrasonic experiments. Joints significantly increase blasting vibration velocity and rock damage depth. Two control measures are proposed: joint grouting and precision blasting, validated by numerical simulation. Joint grouting enhances joint stiffness, reducing unloading stress wave reflection and rock damage. Post-grouting, peak vibration velocities on both cavern sides decrease, more notably on the joint side, with reductions of 3.05 cm/s, 2.86 cm/s, and 3.97 cm/s in three directions. The right-side damage depth is reduced by 1.01 m, 40%. Precision blasting optimizes borehole layout and initiation networks, extending unloading time and reducing transient unloading effects. Its three-directional peak vibration velocity reductions are 2.53 cm/s, 2.53 cm/s, and 3.07 cm/s; non-joint side reductions are 1.85 cm/s, 1.53 cm/s, and 2.03 cm/s. Average damage depth decreases by 0.47 m (left) and 0.61 m (right).