The excavation pit is the heart of many civil and building construction projects: This is where foundations are constructed, basements are built, and existing structures are deconstructed. To turn planning into safe reality, geotechnical engineering, excavation, pit shoring, groundwater lowering and low-impact concrete separation/cutting as well as splitting techniques interlock in a targeted way. Especially in inner-city locations, methods with low vibration levels are used—such as concrete demolition shears for the deconstruction of massive components or rock and concrete hydraulic splitters for precisely releasing rock and concrete without explosives. Darda GmbH provides hydraulic solutions for this purpose, used in various applications from concrete demolition to rock excavation.
Definition: What is meant by an excavation pit
An excavation pit is a temporarily created, lowered ground area required for constructing foundations, basements, or technical installations. It includes the excavation of soil or rock, securing of slopes or walls (shoring), groundwater control as well as all measures that ensure a safe, dry, and accessible construction state. Depending on depth and boundary conditions, a distinction is made between shallow sloped pits and deep pits supported by shoring. In the course of creating the excavation pit, existing foundations, concrete slabs, or rock heads are often released—depending on material and boundary conditions, cutting and splitting techniques are then used.
Planning and setup of the excavation pit
Planning begins with subsoil investigation: stratigraphy, bearing capacity, groundwater level, and potential disturbances influence geometry, shoring, and construction sequence. Based on this, excavation and disposal concepts, mass balances, and a safety concept for the temporary construction states are developed. Typical building blocks include selecting the shoring type, sizing the bracing, organizing groundwater lowering, and choosing suitable cutting and demolition methods for concrete and rock areas. In confined zones or within existing structures, hydraulic handheld tools are often used; they are supplied by mobile hydraulic power units and feature low emissions.
Excavation pit safety and shoring types
Excavation pit safety stabilizes the pit walls against earth and water pressures. In addition to sloped faces, shored systems are used, selected according to depth, adjacent buildings, soil mechanics, and space constraints.
Common shoring types at a glance
- Soldier pile and lagging wall (Berlin shoring): steel beams with timber or shotcrete infill, suitable for dry or weakly water-bearing soils.
- Bored pile wall: successive piles (secant, tangential), tight and stiff, also for greater depths.
- Sheet pile wall: steel sheets as a closed system, well sealable, often with bracing frames; later flush trimming of protruding heads often with steel shears.
- Shotcrete/nail wall: stiffened shotcrete with nails; partial rework on heads and edges often with concrete demolition shears.
Bracing, anchors, and temporary elements
Depending on the load case, tension anchors, braces, or frames are used. When removing temporary elements in the construction sequence, controlled separation of concrete and reinforcement is required—combination shears, multi cutters, and concrete demolition shears allow targeted exposure and cutting of reinforcement without excessively stressing the surroundings.
Excavation methods: soil, rock, and concrete in the excavation pit zone
Excavation is performed with excavators, grabs, or milling attachments. Where the excavation pit meets rock or massive concrete, materials must be released and broken down. In sensitive areas, methods with low vibration levels provide precise work and protect neighboring structures.
Low-vibration techniques
Rock and concrete hydraulic splitters as well as rock wedge splitters from Darda GmbH generate controlled splitting forces in the borehole. In this way, rock heads, foundation blocks, or floor slabs are opened without blasting. Advantages include low vibration levels, reduced noise emission, and minimal collateral breakout—decisive in special demolition, special deployments, and urban environments.
Selective deconstruction below grade
Concrete demolition shears crush thick concrete cross-sections, such as foundations, supports, or diaphragm wall heads. Combination shears and high performance multi cutters separate reinforcement and built-in components; steel shears are used for beams, sheet piles, or temporary steel structures. Hydraulic power packs from Darda GmbH supply the equipment with the required drive power—mobile and adaptable to spatial constraints.
Dewatering and groundwater
Keeping the excavation pit dry is a central issue. Methods range from pumping sumps to wellpoint systems and filter wells. The choice depends on permeability, inflow, and boundary conditions. A lowered groundwater level stabilizes the excavation and improves occupational safety. When using hydraulic splitting and cutting technology, dry work areas are advantageous; water ingress is captured and drained in a controlled manner. Measures to avoid settlements and to monitor drawdown cones are project-specific and based on recognized rules of practice.
Occupational safety, environmental and neighborhood protection in the excavation pit
Dust, noise, and vibrations are to be minimized. Hydraulic cutting and splitting methods work quietly and generate low vibration levels. In addition, dust suppression, targeted shielding, and a low-emission equipment fleet help. Safety distances, load-bearing work platforms, and clear signaling remain fundamental. Limits and obligations are always project-specific and are generally based on applicable regulations, without replacing case-by-case advice.
Construction logistics, material flow, and processing
A clear material flow accelerates the construction process: separate loading of soil, concrete debris, and steel fractions, short routes, adequate buffer areas. Crushing with concrete demolition shears creates loadable piece sizes, reduces loading times, and facilitates construction waste sorting. Where possible, recycled construction material is planned; disposal and recycling routes are secured at an early stage.
Interfaces with special foundation engineering, concrete demolition, and tunnel construction
Excavation pits often interface with special foundation engineering: underpinning, pile heads, anchor exposure, and diaphragm wall heads require precise cutting and finishing. In rock excavation as well as in tunnel heading, rock and concrete hydraulic splitters can be used for controlled profile corrections. In building gutting below grade, compact hydraulic devices from Darda GmbH enable work in tight, hard-to-access areas.
Quality assurance and monitoring
Measurements accompany the construction state: inclinometers and settlement gauges record deformations, groundwater level measurements monitor the dewatering. Regular inspections of shoring heads, bracing, and work spaces increase safety. Documentation, photo logs, and the continuous alignment of design versus as-built geometries support a disruption-free excavation pit construction.
Backfilling and excavation pit closeout
After completion of the basements, temporary elements are removed and the excavation pit is backfilled in layers. Protrusions of concrete or steel are trimmed flush—concrete demolition shears for concrete elements, steel shears for steel profiles. Compaction, drainage, and surface profiling secure the durability of the subsequent construction measures.
Typical challenges and practical solutions
- Confined conditions: Compact, hydraulic handheld tools with an external hydraulic power pack enable work with low headroom.
- Adjacent buildings and vibration protection: Splitting technique instead of impact or blasting reduces vibrations.
- Heavy reinforcement: A combination of concrete demolition shear and multi cutter enables selective separation of concrete and reinforcement.
- Groundwater ingress: Provision of pumping sumps, redundant pump technology, and coordinated dewatering.
- Hard rock or high-performance concrete: Pre-drilling, then controlled splitting with rock wedge splitters.
- Heterogeneous embedded parts: Survey, expose, then separate by material (concrete, steel, composite).
Selecting suitable cutting and splitting technology in the excavation pit
The choice of method depends on material, component thickness, accessibility, and emission requirements. The following criteria support the decision:
- Material type and strength (rock, concrete, reinforced concrete, steel).
- Component geometry and intended fracture planes (e.g., foundation blocks, pile heads, wall heads).
- Accessibility, headroom, and load-bearing capacity of the work platform.
- Requirements for low vibration levels and noise emission in the surroundings.
- Water conditions and the need for dry work areas.
- Fragmentation and disposal concept (blocky, granulated, segregated).
- Hydraulic performance and energy supply via suitable hydraulic power packs.
Terms and key parameters in excavation pit practice
Some key parameters are decisive for planning and execution: allowable slope angles, earth pressure assumptions, groundwater levels and buoyancy safety, deformation limits at the shoring, characteristic loads from traffic and adjacent structures, as well as the design of temporary construction states. Excavation classes, homogeneous zones, and rock description influence equipment choice and construction time; realistic excavation production rates, buffers for weather and logistics, and coordinated monitoring form the framework for an economical and safe excavation pit.