A support foundation is the load-bearing base for components, equipment, or temporary shoring that safely transfers loads into the ground. In the context of concrete demolition, special deconstruction, rock excavation, and tunnel construction, it plays a central role because it ensures structural stability during interventions in existing structures and reliably supports work equipment. Wherever components are separated with concrete demolition shears or dismantled with hydraulic rock and concrete splitters, rock splitting cylinders, or Multi Cutters, the load transfer via a well-planned support foundation must remain structured.
Definition: What is meant by support foundation
A support foundation is a permanent or temporary foundation that transfers vertical and horizontal forces from props, anchors, bracing, machines, or auxiliary structures into the subsoil. It serves to ensure overturning safety, to avoid excessive settlements, and to resist shear forces that arise during cutting, splitting, or gripping. In contrast to areal foundations (e.g., floor slabs), a support foundation often concentrates loads at points (isolated foundations, socket foundations) and can be combined with grouted anchors, micropiles, or bearing plates.
Structure, load transfer, and operating principle
A support foundation typically consists of a load-bearing subbase (frost protection and base course), a foundation base of concrete or reinforced concrete, reinforcement for tensile and bending forces, and, where applicable, bearing and/or anchoring points. Loads follow defined load paths from the prop or machine into the foundation and from there into the ground. In addition to vertical compressive stress, lateral forces from wind, equipment reactions, wire saws, shear operation, or splitting processes must be considered.
Typical elements of a support foundation
- Foundation body (concrete/reinforced concrete) with sufficient bearing area
- Reinforcement and, if applicable, connection reinforcement for bearing details
- Connections: dowels, embedded parts, head plates, anchors
- Water management: drainage, capillary-breaking layers
- Ground improvement: compaction, replacement, injections
Fields of application in concrete demolition and special deconstruction
During deconstruction in existing structures, support foundations secure load axes, machine foundations, and auxiliary shoring in contexts of concrete demolition and deconstruction. They enable controlled separation cuts with concrete demolition shears or the splitting of massive foundations with rock and concrete splitters without overloading adjacent components.
Strip-out and cutting
During strip-out, interior walls, slab fields, and bearings are removed step by step. Temporary support foundations carry head screw jacks, steel posts, or shoring towers. Cutting and pressing forces from concrete demolition shears, combination shears, and steel shears must act only on components that transfer loads into the ground via the support foundation. This limits deformations and avoids inadmissible restraint.
Underpinning in existing structures
If the existing foundation is too weak, or if a new load regime must be created in the course of demolition, underpinning is carried out. Support foundations are constructed in sections while loads are taken over by needle beams or presses. Where rock splitting cylinders are used, the splitting direction must be chosen so that no tension cones run toward the temporary foundations.
Support foundations in rock excavation and tunnel construction
In rock excavation, support foundations serve as bearings for drilling carriages, column supports, temporary portals, or machines. Their task is safe support on uneven, often inclined rock. At tunnel portals, they stabilize bracing and anchor points. When rock blocks are released with rock and concrete splitters, minimum distances to foundation edges must be maintained to avoid spalling in the bearing area.
Lateral forces and reaction loads
Hydraulically operated equipment (e.g., concrete demolition shears, Multi Cutters) generates reaction forces. The support foundation must transfer these forces into the ground via anchorages, anchor plates, or shear dowels. With low soil bearing capacity, micropiles help to take up lateral forces.
Natural stone extraction and temporary bearings
In quarries, support foundations serve as stable setup surfaces for booms, lifting devices, and power unit stations. Temporary support foundations can be designed as load-distributing plates when changing locations are required. Low vibration levels during splitting and crushing facilitate work near sensitive bearings; nevertheless, settlement and inclination monitoring is advisable.
Design: actions, ground, and safety concept
Dimensioning is based on subsoil conditions and the acting loads. The goal is a foundation that satisfies structural safety, serviceability, and durability.
Relevant input parameters
- Soil parameters: density, angle of friction, cohesion, stiffness modulus, groundwater level
- Permanent loads: self-weight of prop, foundation, equipment
- Variable loads: operating forces from concrete demolition shears, rock and concrete splitters, transport, wind
- Lateral forces and moments: from cutting/splitting processes and boom positions
- Boundary conditions: frost depth, drainage, chemical attack, construction stages
Normative requirements must be checked project-specifically. In general, the principles of geotechnics and reinforced concrete construction apply. The information is without guarantee and does not replace a structural design.
Material selection and execution
Reinforced concrete is often chosen for permanent support foundations. Temporary foundations can consist of reinforced cast-in-place concrete, precast elements, heavy-duty plates, or composite systems. Corrosion protection of anchors, sufficient concrete cover, and appropriate water management increase durability. The foundation surface must be executed so that bearing plates, hydraulic power packs, and cutting torch peripherals stand securely and forces are introduced in a defined manner.
Water and frost
Standing moisture and frost heave jeopardize serviceability. Capillary-breaking layers, slopes, and drains keep the foundation dry. In frost-prone zones, the foundation depth must be adjusted.
Practice with concrete demolition shears and rock and concrete splitters
The work sequence influences the requirements for the support foundation. Precise cuts and splitting processes reduce uncontrolled load redistributions.
Load paths and support points
Before separating with concrete demolition shears, load paths must be defined. Temporary supports stand on support foundations with sufficient bearing area and slip resistance. The locations of anchor drill holes must be chosen so that the anchor groups can take shear and tension.
Drilling pattern and splitting direction
When using rock splitting cylinders, the drilling pattern and splitting direction influence the fracture surfaces. Distance from the support foundation prevents cracks from propagating into its bearing area. With high lateral forces, counter-bearings or anchors must be provided.
Monitoring settlements
Monitoring points at prop bases, wedges, and foundation edges reveal settlements early. Minor readjustments at screw jacks or shims prevent tilting before cutting or splitting operations continue.
Temporary support foundations: variants and use
Temporary solutions can be produced and dismantled quickly. They are suitable for changing site situations during strip-out, special operations, and natural stone extraction.
- Heavy-duty mats and plates with sand-cement bedding for load distribution
- Modular foundation boxes with infill (e.g., gravel, lean concrete)
- Steel consoles on micropiles for confined existing basements
- Socket foundations for mounted steel posts with interchangeable head plates
Typical mistakes and how to avoid them
- Insufficient geotechnical investigation: at least consider thickness of the competent layer and groundwater.
- Missing transverse anchorage points: lateral forces from shearing and cutting operations must be proven to be transferred.
- Insufficient bearing area: point loads otherwise lead to punching and settlement problems.
- Underestimated water management: without drainage, softening and frost damage threaten.
- Unfavorable splitting direction: cracks run toward the bearing if distances are too small.
- Missing monitoring: settlements go unnoticed and accumulate over construction stages.
Safety, organization, and environmental protection
A support foundation is part of the safety concept. Escape and work routes to be kept clear, regulated load transfers, and defined exclusion zones must be established. Dust and noise protection should be planned early; hydraulic methods with low vibration levels facilitate work near sensitive existing foundations. Permits and verification obligations depend on the project and region and must generally be clarified with the responsible authorities in advance.
Planning checklist for support foundations
- Objective and duration: temporary or permanent, define load cases.
- Ground: investigations, parameters, groundwater, frost.
- Loads: vertical, horizontal, moments from work equipment (concrete demolition shears, rock and concrete splitters, hydraulic power packs).
- Geometry: foundation dimensions, edge distances, anchor layout.
- Execution: concreting, reinforcement details, surface, water management.
- Monitoring: settlement points, control intervals, limit values.
- Construction sequence: order of shoring, cutting, splitting, and unloading.
- Dismantling/reuse: disassembly, recycling, backfilling.
Terminology and distinctions in context
Support foundation denotes the load-transferring base for props, machines, and auxiliary structures. It is distinct from plain bearing plates without bond to the ground and differs from abutments, which primarily resist horizontal forces from cables or presses. In underpinning, the support foundation is constructed section by section under existing components; in deconstruction, it carries temporary systems until components are removed in a controlled manner with concrete demolition shears, concrete demolition shear peripherals, or rock splitting cylinders. This creates a consistent load path from the intervention point down into the ground.