Numerical Analysis of Joint-Controlled Slope Stability under Blasting-Induced Vibration: A Case Study of the Jakarta-Bandung High-Speed Railway Tunnel 4

Abstract

Blasting for Tunnel 4 of the Jakarta–Bandung High-Speed Railway is conducted close to an active andesite quarry, where blast-induced vibration may interact with pre-existing discontinuities and groundwater to reduce slope stability. This study evaluates the combined effects of joint structure, groundwater conditions, and tunnel-blasting vibration on quarry-slope stability using two-dimensional finite-element analysis in RS2 with the shear-strength-reduction method. Field characterization comprised scanline discontinuity mapping, rock-mass classification, laboratory testing, and Minimate vibration monitoring. Jointless and explicitly jointed slope models were evaluated under four scenarios: dry-static, dry-dynamic, saturated-static, and saturated-dynamic. The monitored blast dataset was additionally evaluated using the site-specific scaled-distance relationship, PPV = 156.3(SD)−1.056 (R2=0.376), where SD = R/√Q, to characterize vibration attenuation and its uncertainty. Under static conditions, explicit joints reduced the factor of safety (FoS) by 3% in the dry model and 6% in the saturated model. Under dynamic conditions, the joint-related FoS reduction increased to 15% in the dry model (4.1 to 3.5) and 42% in the saturated model (3.4 to 2.0), with the probability of failure reaching 17% in the critical saturated-dynamic-jointed scenario. A charge-per-delay sensitivity analysis at a fixed source-to-slope distance of 25 m further showed that increasing explosive charge progressively increased the predicted longitudinal peak particle acceleration (PPA) and reduced slope stability. Based on the adopted stability criteria, the analysis supports maximum site-specific charges of 30 kg/delay under dry conditions and 20 kg/delay under saturated conditions at 25 m. These results demonstrate that groundwater saturation substantially amplifies the destabilizing influence of blasting on joint-controlled slope response and highlight the need for groundwater-dependent blast control, controlled trial blasts, and field monitoring before operational implementation.