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Vibration Mitigation and Control for Single-Arm and Double-Curvature-Arm Rock-Drilling Rigs in Shallow-Buried Urban Tunnels
Release time:
2026-09-03
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Summary:
In the construction of shallow‑buried urban tunnels, where surface structures are densely packed and overburden is thin, mitigating the impact of blasting vibrations on the surrounding environment is a key priority in project management. Fully mechanized, integrated construction represents a critical approach to vibration‑reduction blasting, adopted after comprehensive technical evaluation. By deploying mechanized equipment such as multi‑function rock‑drilling rigs and arch‑support carriers, and by installing surface‑structure monitoring instruments for continuous tracking, this method ensures the safety of both public life and property. Combining the high drilling accuracy of rock‑drilling rigs with a robust vibration‑monitoring system creates a dual‑layer vibration‑control mechanism—addressing source‑level borehole control and real‑time vibration regulation—thus providing an effective technical pathway for vibration‑mitigation in shallow‑buried urban tunnel projects.
I. Special Requirements for Vibration Control in Shallow-Buried Urban Tunnels
When shallow‑buried urban tunnels pass beneath existing structures, the dense concentration of surface buildings means that excessive vibration can easily cause damage or even collapse. According to the “Safety Code for Blasting” (GB 6722), the permissible particle velocity for typical civil buildings is 1.5–2.0 cm/s (f ≤ 10 Hz), while for transportation tunnels it is 10–12 cm/s (f ≤ 10 Hz). In urban settings, the allowable threshold for surface vibration from shallow‑buried tunnels is often more stringent; in numerous engineering applications, by carefully designing appropriate cut‑hole configurations and blast parameters, surface vibration has been successfully kept below 2.0 cm/s. When tunneling through masonry structures, the safety threshold must be further reduced to 0.5–2.0 cm/s.
In vibration‑control applications, the rock‑drilling rig serves as the “front‑end precision executor.” Insufficient drilling accuracy can lead to ineffective adjustments in charge quantities and uncontrolled blast vibrations; by contrast, a fully computerized rock‑drilling rig can keep vibration at the source within specified limits right from the drilling stage.
II. Pre‑vibration Isolation Measures Based on Rock‑Drilling Rigs
A ring of slot holes is arranged along the perimeter of the excavation face to isolate it from the surrounding rock mass, preventing impact waves from the face from propagating into the surrounding rock and thereby reducing disturbance. The peripheral pre‑drilled vibration‑damping hole technique is employed: large‑diameter empty holes absorb the stress waves generated by the cut‑hole blasting, thus attenuating energy transmission to the adjacent rock. In shallow‑buried urban tunneling projects, combining large‑diameter cut‑hole empty holes with straight‑hole cut‑hole sequential delayed detonation, together with peripheral pre‑drilled vibration‑damping holes and staggered charging in the peripheral holes, can effectively mitigate the vibrational impact of blasting on surface structures. For hard rock formations, a combined approach of wedge‑shaped cut‑holes and empty‑hole cut‑holes is recommended—leveraging the guiding effect of offset empty holes to promote crack propagation along the designed contour, thereby minimizing the leakage of blasting energy into the surrounding rock.
III. The Supporting Role of Borehole Accuracy Control in Vibration Damping
Drilling errors directly cause the blast energy distribution to deviate from the design, leading to localized vibration concentration and constituting one of the common causes of excessive vibration in urban shallow‑buried tunnels. The CRRC ZYS113G fully computerized three‑arm rock‑drilling rig requires that borehole deviations not exceed 3 cm, with the bottom of all holes lying on the same cross‑section and spaced no more than 10 cm apart; furthermore, the spacing of peripheral holes must be within 5 cm, the fork angle should not exceed 2°, and the holes must be aligned parallel to the tunnel’s centerline.
The computer‑assisted positioning system serves as the technological foundation for achieving high‑precision, vibration‑reduced drilling. Design parameters are entered into the carriage’s onboard computer; using a 3D scanner, the carriage identifies known tunnel points to compute its own position. The central control platform displays detailed information on each blast hole, including depth, location, and angle, enabling the operator to perform precise drilling according to the onscreen instructions. The system continuously monitors and collects key drilling parameters—such as drilling pressure, penetration rate, and drill‑rod rotation speed—and leverages MWD software to reconstruct subsurface geological conditions, refine the blasting plan, and provide dynamic feedback for vibration control. An automated hydraulic control system, which dynamically matches drilling parameters to both advance pressure differential and rotational torque, enables real‑time adaptation of optimal vibration‑mitigation drilling settings across varying surrounding rock conditions.
IV. Dynamic Closed-Loop of Vibration Monitoring and Feedback Control
In shallow‑buried urban tunnels, surface vibration monitoring and borehole‑based vibration mitigation must be integrated into a dynamic closed loop. During construction, surface‑mounted monitoring instruments are deployed to track and record vibrations, with measured data fed back in real time to adjust the blast‑hole layout parameters for the next cycle. A high‑precision millisecond‑delay, hole‑by‑hole initiation technique is employed, with inter‑stage time intervals exceeding 50 ms, ensuring complete separation of vibration waves and minimizing wave superposition effects.
For sections with varying vibration risk levels, a stepwise advance‑length control strategy can be adopted. An advance of 80 cm, by reducing the charge per blast segment, effectively limits surface vibration velocity; meanwhile, a 1.8‑m controlled‑blasting scheme can meet design‑specified vibration limits but results in slightly higher energy input to structures. The most suitable approach should be selected based on site-specific conditions. A 3D scanner is used to measure the tunnel’s inner surface profile after blasting, and the data are processed via computer reconstruction to generate 3D contour information, yielding over‑ or under‑excavation metrics. By comparing these measured profiles with the design specifications, quantitative guidance is provided for optimizing vibration‑reduction drilling patterns in the next cycle.
V. Recommendations
In the construction of shallow‑buried urban tunnels, vibration‑mitigation control by rock‑drilling rigs should be integrated throughout the entire process, from borehole‑design planning to post‑construction performance evaluation. In areas with dense surface structures, the target for ground‑surface particle velocity should be set at no more than 1.5–2.0 cm/s. A combined pre‑vibration‑isolation strategy—employing peripheral slot holes and empty holes—should be adopted to prevent stress waves from propagating into the surrounding rock at the source. The fully computerized rig’s automatic positioning and precision‑hole‑drilling capabilities, coupled with real‑time feedback from vibration‑monitoring data, constitute a critical safeguard for vibration‑controlled tunneling in urban settings. Once a reliable borehole‑blasting match has been established through effective vibration‑control measures, continuous validation via surface‑vibration monitoring can further refine the rig’s drilling parameters, enabling closed‑loop management that spans from “source‑level borehole design” through “vibration assessment” to “parameter optimization.”
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