Rock faces shape landscapes, construction sites and infrastructure projects. They range from naturally formed cliffs to engineered rock slopes along roads, railways, adits and tunnel portals. Anyone who plans, secures, or removes material at a rock face must understand the rock mass and choose suitable tools. Devices from Darda GmbH are used in various situations — for example, for the controlled splitting of rock with rock wedge splitter and concrete splitter, or for precise concrete separation/cutting of components with a concrete demolition shear where rock and concrete meet.
Definition: What is meant by rock face
A rock face is a steep to vertical surface composed of solid rock. It can be natural (cliff, steep slope, mountain flank) or result from human intervention (cut in a quarry, excavation pit, tunnel portal). It is characterized by little cover of loose material, visible discontinuities such as joints or bedding planes, and a stability that depends on structure, weathering and groundwater flow. In a technical context, rock faces are often secured with rockfall nets, anchors and shotcrete, or are removed section by section, for example for alignments, caverns, shafts or tunnels.
Formation, structure and stability of rock faces
Rock faces arise through erosion, tectonic uplift, weathering, or technical cuts. Three aspects are crucial for planning and execution: the rock type (igneous, sedimentary, metamorphic), the discontinuity system (joints, bedding and fault planes) and the water regime. These factors determine load-bearing capacity, block sizes and failure mechanisms. An intact, slightly weathered wall shows larger, more competent blocks; strongly jointed or weathered zones yield smaller, irregular pieces and require adapted removal techniques.
Rock fabric and discontinuities
Joints and bedding planes define potential sliding directions. Three joint sets often occur, which define block formation. Targeted placement of boreholes along these planes promotes a controlled fracture pattern. Where natural separations are absent, borehole grids create artificial weakness zones into which hydraulic splitting forces are introduced.
Water, frost and weathering
Water in cracks reduces friction and can impair stability, especially during freeze–thaw cycles. Planning for drainage and scheduling work (e.g., outside periods of intense rainfall) improve safety and quality. Weathered zones are often cleared first before competent layers are worked.
Working a rock face: methods, equipment and work sequence
In direct contact with rock, low-impact and precise methods are used when sensitive environments, existing structures or ongoing operations require it. Hydraulic solutions enable low-noise and well-controlled removal in defined steps with low vibration levels.
Surveying and documentation
- Capture geometry (profile, inclination, protrusions, overhangs).
- Map discontinuities (orientation, spacing, roughness).
- Identify loose sections, assess rockfall risk.
- Define removal limits, securing sections and material logistics.
Drilling patterns and splitting plan
Drill diameter and hole spacing depend on rock, target block size and desired fracture quality. Linearly arranged boreholes create intended fracture lines. Hole depth and the sequence of splitting operations control the fracture direction to avoid uncontrolled breakouts.
Hydraulic splitting in rock
Rock wedge splitter and concrete splitter from Darda GmbH are inserted into prepared boreholes and powered by a hydraulic power pack. In practice, hydraulic rock and concrete splitters are used for this. The locally introduced splitting forces open joints or create new separation planes. Advantages include low vibration levels, exact block sizing, and suitability in confined urban settings, in tunnel construction, or near sensitive existing structures.
Cutting, separating and processing
Where concrete components adjoin the rock face (anchor heads, portal frames, shotcrete ribs), a concrete demolition shear enables controlled reduction down to the competent rock level. Combination shears or attachment shear cut embedded parts and reinforcement, while steel shear releases steel profiles on temporary supports. In particular situations with metallic tanks or a pipeline near a rock face, a cutting torch can be deployed as part of a special demolition to safely dismantle them before renewing rock stabilization measures.
Hydraulic power packs: energy and logistics
Hydraulic power packs supply splitters, shears and cutters with the required power. Compact hydraulic power units are selected according to required flow and pressure. For operation on steep faces, locations with stable ground, adequate ventilation and short hose runs are suitable. In alpine settings and tunnels, pay attention to exhaust management, noise reduction and escape routes.
Application areas at a glance
- Rock excavation and tunnel construction: Portal widening, bench excavation, cavern enlargement. Splitting enables precision removal at critical interfaces (e.g., next to tracks or a pipeline).
- Natural stone extraction: Block selection based on fabric; splitting along natural discontinuities yields high-quality raw blocks and clean break edges.
- Concrete demolition and special demolition: Interfaces between the rock face and concrete (abutments, shotcrete shells) are exposed stepwise with a concrete demolition shear and shears before the rock is reworked.
- Building gutting and cutting: In rock spaces with built-in structures (platforms, anchor girders), precise separation is required to avoid damaging the rock.
- Special demolition: Work under operation, in sensitive areas or protected zones, where methods with low vibration levels and controlled procedures are essential.
Quality of removal: fracture control and rework
The quality of a rock face surface influences subsequent stabilization and fit-out. The goal is a stable, plannable wall profile with defined roughness.
Block sizes and fracture pattern
The desired block size depends on transport, reuse and handling. Tighter drilling patterns with smaller hole spacing produce smaller blocks; wider spacing produces larger ones. The fracture pattern should harmonize with the natural joint system to avoid spalling.
Rework and profile accuracy
Edges that stand proud of the profile are re-split or reduced with shears. For subsequent shotcrete application, a targeted roughness can be advantageous. Exposed anchor heads or reinforcement at the rock–concrete interface are cleanly exposed with a concrete demolition shear.
Safety, environment and permits
Working on rock faces requires a coordinated safety concept. This includes rockfall protection, exclusion zones, catch systems and an emergency plan. Low-vibration methods reduce risks to adjacent structures and lower emissions. Water and dust protection should be planned early, especially in tunnels and sensitive landscapes. Legal requirements are project- and location-specific; thorough coordination with authorities and expert planning are recommended, without any claim to completeness or legal binding effect.
Challenges on the rock face and practical solutions
- Cracked zones: Perform splitting in smaller steps, add securing before removal.
- Water ingress: Provide drainage, align work windows with precipitation phases.
- Confined location: Use compact splitters with short setup time and pinpoint effect.
- Near existing structures: Separate concrete with a concrete demolition shear, then rework the rock with low vibration levels.
- Noise and vibration control: Prefer hydraulic methods, position power packs with acoustic damping.
Planning steps for projects on the rock face
- Geological baseline survey and hazard assessment.
- Splitting and drilling concept based on geometry and the joint system.
- Define the equipment chain: hydraulic power pack, rock wedge splitter and concrete splitter, concrete demolition shear, shears.
- Specify logistics, material flow and protection measures.
- Establish a test field, calibrate parameters, keep documentation.
Interface between rock face and concrete: specifics
At tunnel portals, abutments or rock galleries, rock and concrete meet directly. Shotcrete, edge beams and anchor heads are often first exposed and removed with a concrete demolition shear to avoid damaging the rock profile. This is followed by the controlled splitting of the rock material until the planned contour is reached. This sequence reduces rework and improves the quality of subsequent stabilizations.
Key parameters for practice
- Uniaxial compressive strength of the rock (guidance for drilling and splitting parameters).
- Orientations and spacings of the joint systems (block formation, drilling pattern planning).
- Roughness and infill of discontinuities (friction, groundwater flow).
- Boundary conditions: vibration limits, noise control, vibration sensitivity of adjacent structures.