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Flexible excavation scheme for single-arm and double-curve-arm rock drilling rigs at tunnel intersections
Release time:
2026-09-22
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Summary:
In tunnel construction, in‑tunnel junctions—such as cross passages and the transition zones between adits and the main tunnel—are critical “bottleneck” areas characterized by complex spatial configurations and abrupt changes in cross-sectional geometry. Constrained by the precision and flexibility of conventional manual drilling and blasting, excavation at these junctions is prone to excessive or insufficient overbreak and underbreak, while process handovers are time‑consuming. The adoption of single‑arm and dual‑curved‑arm rock‑drilling rigs, coupled with judicious equipment selection and streamlined workflow integration, can effectively address these challenges.
I. Hyperbolic-Arm Trolley: A Versatile Solution for the Bench Method and Irregular Cross-Sections
In weak surrounding rock or large‑section tunnels, intersections often require excavation using two‑stage or three‑stage methods to minimize disturbance to the surrounding rock. Conventional rock‑drilling rigs, constrained by their straight‑arm design, struggle to reach low, under‑bench areas, resulting in limited adaptability to different construction techniques. The introduction of a double‑curved‑arm rock‑drilling rig has filled this gap. Its pioneering “Z‑shaped curved arm” configuration, incorporating two bending hinges and a dual‑rotation reducer, enables the boom to swing with exceptional flexibility, extending its working reach below the horizontal plane and easily accessing the invert and lower bench zones—thereby overcoming the longstanding challenge of traditional equipment being unable to construct the invert.
In the construction of key national projects such as the Shenyang–Baishan High-Speed Railway, the double‑arm rock‑drilling rig has demonstrated exceptional efficiency and flexibility. At the Hou’an Tunnel on the Shenyang–Baishan HSR, it achieved an average of 3.5 hours to complete two‑stage excavation at a single working face, with a maximum advance of 4.7 meters per cycle. Meanwhile, at the intersection of the No. 2 inclined shaft in the Changqing Tunnel—where the cross‑section measures 8 m × 9 m—the rig consistently drilled a single hole in under two minutes, enabling highly efficient execution of more than 120 blast holes. Its compact overall length effectively prevents collisions between the boom and the side walls of the working face; coupled with remote‑control operation, operators can closely monitor drilling conditions from outside the cab, ensuring precise control over the excavation geometry of the transition zone at the intersection.
II. Straight-Arm Plus Curved-Arm Combination: Solving the Challenge of “Full-Process Coverage”
To address the common pain point in intersection tunneling—equipment idling due to frequent changes in construction methods—the “straight‑arm plus curved‑arm” combination is a highly recommended configuration. Conventional straight‑arm rock‑drilling rigs excel at drilling in the arch crown and sidewalls but are significantly constrained during three‑stage excavation and invert construction; by contrast, dual‑curved‑arm rigs are well suited to variable cross‑sections and low‑position drilling. Working in tandem, the dual‑curved‑arm rig takes the lead on the upper and middle stages as well as the invert, while the single‑arm or straight‑arm rig supports sidewall drilling and fills in gaps, thereby substantially boosting equipment utilization and eliminating idle time caused by method transitions.
Furthermore, for intersections such as inclined shafts and cross‑tunnels with limited width, the sliding‑arm structure (a dual‑sliding‑arm carriage) employs a drill‑arm sliding mechanism that significantly reduces the overall vehicle length. This design meets the stringent requirements of multi‑section construction and high maneuverability in curved sections, enabling the machine to turn around and reposition itself with ease even in tight intersection spaces.
III. Single-Arm Trolley: The “Gap-Filler” for Narrow Cross-Sections and Precision Operations
At intersections with small cross-sections—such as connecting tunnels—or in areas requiring precise slotting, large, multi‑arm articulated rigs are often constrained. In such cases, single‑arm rock‑drilling rigs, with their compact footprint and high maneuverability, can quickly position themselves in confined spaces to accurately drill slotting holes and perimeter blast holes, making them particularly well suited for step‑by‑step excavation methods and auxiliary drilling operations.
At the initial support reinforcement section of the intersection, the single-arm carriage can also be used to drill anchor bolt holes and advance pipe‑shed holes, enabling “one machine, multiple functions” and reducing the need for auxiliary equipment.
IV. High-Precision Control and Rapid Ring Formation: Eliminating Over- and Under‑Excavation at the Source
Whether it’s a dual‑arm or single‑arm rig, its core value lies in high‑precision positioning control. The fully computerized rock‑drilling rig, equipped with a 3D scanning and automated hole‑placement system, can keep hole‑position deviations within design tolerances, ensuring that blast holes all terminate on the same plane and thereby minimizing disturbance to the surrounding rock at the source of blasting. Compared with traditional manual drilling, the rig delivers a substantial boost in drilling efficiency while significantly reducing the number of operators required.
In terms of workflow coordination, the efficient operation of the tunneling carriage creates favorable conditions for “rapid excavation and rapid support.” By leveraging the carriage’s built-in wet-spraying manipulator or integrating it with an arch‑support carriage, immediately after each sectional excavation at the intersection, shotcrete is applied to seal the excavated area, swiftly establishing an initial support system and effectively mitigating the risk of stress concentration in the surrounding rock during construction of intersecting tunnel segments.
In summary, under the complex working conditions at tunnel intersections, the double‑arm rock‑drilling rig, with its articulated boom design, effectively addresses the challenges of adapting to both benching and invert‑construction methods, making it the primary equipment for overcoming the bottleneck sections. Meanwhile, the single‑arm rig leverages its maneuverability to handle narrow spaces and perform high‑precision auxiliary drilling. When these two types of rigs operate in coordinated synergy, coupled with a high‑precision automated control system, they can significantly enhance both the safety and cost‑effectiveness of intersection‑area construction.
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