Support foundation

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. In practice, this means verifiable load paths, sufficient bearing pressure capacity, and controlled dissipation of lateral forces and moments during every construction stage.

Definition: What is meant by a 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 resistance to overturning, 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. Depending on the task, checks against sliding, uplift, punching, and local crushing of bedding layers are required.

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. Quality of execution is decisive: compacted base courses, level bearing surfaces, and clean interfaces reduce stress peaks and slip.

Typical elements of a support foundation

• Foundation body (concrete or 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
• Shear keys or surface roughening to increase sliding resistance where required
• Leveling grout, shims, or grout pads for even load introduction under plates and rails

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. Where wire sawing, core drilling, or pressing are involved, temporary foundations maintain positional stability and minimize secondary effects on existing structures.

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. Sequencing that alternates cutting and re-shoring reduces redistributions and keeps settlements within defined limits.

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. Curing times, jacking increments, and monitoring of contact pressures must be defined to prevent torsion and differential settlements during transfer.

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. In addition, leveling layers, dowels into competent rock, and roughened interfaces increase shear capacity and reduce slip along inclined planes.

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. Proofs of pull-out, group effects, and fatigue under cyclic operation are part of the verification, in particular when load directions alternate during cutting or splitting cycles.

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. Where relocation is frequent, modular plate systems with defined friction coefficients and marked load zones increase process reliability.

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. Typical verifications include bearing pressure, sliding, overturning, uplift, punching shear, and deformation limits for short-term and sustained loading. Assumptions, partial factors, and construction stages must be documented transparently.

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 or splitting processes and boom positions
• Boundary conditions: frost depth, drainage, chemical attack, construction stages
• Uplift and pull-out: anchor capacities, embedment lengths, group spacing
• Cyclic actions: frequency and number of load cycles during demolition sequences

Normative requirements must be checked project-specifically. In general, the principles of geotechnics and reinforced concrete construction apply. Depending on jurisdiction, geotechnical categories, exposure classes, and minimum reinforcement for crack control may govern design. 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. Tolerances for levelness, edge distances, and grout thicknesses should be specified; where sliding is critical, provision of shear lugs or keyed interfaces is recommended.

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. In aggressive environments, select frost-resistant aggregates and ensure free-draining backfill to avoid ice lenses and softening of the bearing layer.

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. Clearly defined exclusion zones and load limits at bearing points prevent local overstress during repositioning of equipment and props.

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. Marking of support points, minimum edge distances, and anti-uplift measures (e.g., tie-downs) help maintain geometry during staged removal.

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. Minimum edge distances, hole spacing, and staggered activation reduce the risk of spalling and uncontrolled crack branching.

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. Define trigger levels and action plans so that corrections occur before serviceability limits are exceeded.

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. Selection depends on required bearing pressure, available footprint, and permissible ground disturbance.

• 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
• Ballasted plate stacks with anti-slip interlayers where anchoring to subsoil is not feasible

Typical mistakes and how to avoid them

1. Insufficient geotechnical investigation: at least consider thickness of the competent layer and groundwater.
2. Missing transverse anchorage points: lateral forces from shearing and cutting operations must be proven to be transferred.
3. Insufficient bearing area: point loads otherwise lead to punching and settlement problems.
4. Underestimated water management: without drainage, softening and frost damage threaten.
5. Unfavorable splitting direction: cracks run toward the bearing if distances are too small.
6. Missing monitoring: settlements go unnoticed and accumulate over construction stages.
7. Ignored curing and grout strength development: premature loading reduces capacity and increases slip.
8. Unclear documentation of load cases and construction stages: missing records hinder safe adjustments on site.

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. Lifting plans, tool change procedures, and toolbox briefings should reflect the current support configuration and the verified load limits of each bearing point.

Planning checklist for support foundations

1. Objective and duration: temporary or permanent, define load cases.
2. Ground: investigations, parameters, groundwater, frost.
3. Loads: vertical, horizontal, moments from work equipment (concrete demolition shears, rock and concrete splitters, hydraulic power packs).
4. Geometry: foundation dimensions, edge distances, anchor layout.
5. Execution: concreting, reinforcement details, surface, water management.
6. Monitoring: settlement points, control intervals, limit values.
7. Construction sequence: order of shoring, cutting, splitting, and unloading.
8. Dismantling or reuse: disassembly, recycling, backfilling.
9. Interfaces and permits: responsibilities, approvals, documentation, inspection points.
10. Quality assurance: preloading or proof testing of anchors, grouting records, as-built data.

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. Clear terminology helps delineate tasks in design, execution, and monitoring and ensures that verification responsibilities are assigned unambiguously.