Dynamic Response and Stability Analysis of Underground Mine Water Sump Under Blasting Vibration

Blasting in open-pit mines can disturb permanent underground structures. This study examines an underground water sump in medium–hard dolomite at Kunyang Phosphate Mine. A detailed three-dimensional model was built in ANSYS Workbench. The Drucker–Prager (D-P) yield criterion was used. Measured acceleration time histories were applied throughout the model in three directions. Six cases were identified by representative peak vibration velocities of 6.4–27.1 cm/s. Transient dynamic analyses examined stress, displacement, vibration velocity and local safety reserve. High stresses occurred at junctions of the roof and walls, bottom corners and sump–shaft connections. The peak equivalent stress increased almost linearly from 8.08 to 12.90 MPa. The maximum principal stress showed local tension and compression. Its tensile peak increased from 0.72 to 3.56 MPa. This was below the static tensile reference of 9.44 MPa for intact laboratory specimens. The minimum principal stress was mainly compressive. The peak compressive stress in the deep surrounding rock reached −15.10 MPa. Positive displacement peaks increased from 0.69 to 2.51 mm. Negative peaks changed from −0.80 to −2.71 mm. These values describe transient model responses. Positive velocity peaks increased from 6.36 to 26.74 cm/s. Cases P2–P6 exceeded the project control reference of 8.5 cm/s. The local indicator FS was greater than one for the extracted states at all nine monitoring locations. At high vibration levels, FS was about 1.25 at the arch baseline and the middle of the bottom side wall. These locations had relatively low reserves. The results provide a quantitative basis for blast parameter optimisation and vibration control for the water sump.