Foundation methods link the subsoil, foundation, and load-bearing system into a robust whole. They start long before the superstructure with excavation of the pit, shoring, and ground improvement, and often only end once bearing surfaces are precisely prepared and existing structural elements have been adjusted or selectively deconstructed. Where rock or massive concrete is encountered, low-vibration removal techniques are used during foundation preparation and strengthening, for example with hydraulic rock and concrete splitters for controlled splitting or with concrete pulverizer for targeted removal of foundations and cropping of pile heads. This is where geotechnical engineering, construction execution, and selective deconstruction interlock.
Definition: What Is Meant by Foundation Methods
Foundation methods comprise all technical measures that permanently and safely transfer a structure’s loads into the ground. This includes the selection and sizing of the foundation type (for example, shallow foundation or deep foundation), pit shoring, ground improvement, groundwater lowering, as well as all preparatory, accompanying, and final work steps, including the controlled demolition of existing foundations or rock structures within the foundation zone. The objective is safe, low-deformation, and economical load transfer while complying with the relevant standards and project-specific boundary conditions.
Types of Foundation Methods: Shallow Foundation, Deep Foundation, and Ground Improvement
The choice of method depends on subsoil, load level, deformation sensitivity, and environmental requirements. In practice, three groups are distinguished, which can be combined in parts.
Shallow Foundation
Load transfer via foundations at small depth (for example isolated, strip, or slab foundations) on competent, low-settlement subsoil. Flat, load-bearing foundation bases are required; rock projections or old concrete are locally adjusted or removed. Here, low-vibration approaches such as splitting rock or selectively removing excess concrete with a concrete pulverizer are suitable to avoid settlements and damage to adjacent buildings.
Deep Foundation
Load transfer via piles, caissons, or diaphragm walls into deeper load-bearing strata. Typical solutions are bored piles, driven piles, or micropiles. In refurbishments, the pile head is often exposed after curing and cropped to exact level; a concrete pulverizer enables controlled opening of the concrete while preserving the reinforcement, which is then cut with a steel shear or multi cutters. Rocky obstructions in the pile axis can be selectively resolved with a hydraulic splitter.
Ground Improvement and Stabilization
Methods such as vibro-replacement, injection, or grouting increase load-bearing capacity or reduce deformations. Where local obstacles (existing foundations, foundation remnant) interfere in the construction area, the zone is selectively deconstructed in advance. In confined conditions, hydraulic splitting and cutting techniques are helpful, as they avoid blasting and generate low vibration levels, for example by using non-explosive rock removal.
Excavation of Pit and Boundary Conditions for the Foundation
The excavation pit is the working field of the foundation. Its geometry, shoring, and groundwater lowering determine quality and schedule. The transition to selective deconstruction is fluid, especially in existing structures.
Shoring and Pit Safety
sheet pile wall, soldier pile walls, bored pile walls, or shotcrete shoring secure the excavation pit. In inner-city environments, vibration, noise, and dust are strictly limited. When working up to existing foundations, controlled removal with a concrete pulverizer helps maintain predetermined break lines and avoid cracks.
Excavation, Grading, and Base Preparation
The foundation base must be flat, load-bearing, and free of loose material. In rocky conditions or with old concrete residues, high precision is required. A hydraulic splitter enables the precise lowering of edges and the release of hard inclusions without damaging adjacent areas.
Dewatering and Soil Management
Open dewatering, filter wells, or a cut-off wall protect the excavation. Excavated material is collected separately and reused where possible. When deconstructing parts of foundations, dust- and water-conscious working methods are important so as not to endanger excavation pit stability.
Interfaces to Concrete Demolition and Special Deconstruction
Foundations in existing structures often require adjustments: partial demolition, exposure, strengthening, or replacement. These tasks belong to concrete demolition and special demolition and must respect the structure’s residual load-bearing capacity.
- Expose and adjust foundation edges without damaging adjacent elements using a concrete pulverizer.
- Split rock ridges or massive foundation blocks in the work area with a hydraulic splitter to reduce vibrations.
- Cut reinforcement and embedded items with a steel shear or multi cutters as a preparatory step for new foundation elements.
- Selective deconstruction in sensitive environments, for example for a special demolition in heritage areas or during ongoing operations.
Selection Criteria for the Appropriate Foundation Method
The decision balances subsoil, structural requirements, environmental requirement, and construction sequence. The following factors are decisive:
- Subsoil and groundwater: load-bearing capacity, settlement tendency, stratification, rock content, water inflow.
- Loads and use: total load, point loads, vibrations, permissible deformations.
- Context: adjacent buildings, vibration and noise limits, inner-city location.
- Logistics: accessibility, working heights, crane and equipment availability, power supply via hydraulic power units.
- Deconstruction and adaptation needs: existing foundations, contaminated sites, necessary openings or recesses.
- Schedule and economy: construction window, staged execution, reusability of materials.
Execution and Quality Assurance
Careful execution prevents later settlements and damage. Quality features include documented soil parameters, proofs of load-bearing capacity, dimensional accuracy, and controlled surface condition of the foundation base.
Tolerances and Dimensional Accuracy
Elevation, flatness, and plumb tolerances must be met. When matching the base to rock structures, controlled splitting ensures a precise result without over-removal.
Documentation
Test records, compaction test certificate, pile integrity tests, and acceptance of the foundation base are part of quality assurance. Selective deconstruction steps are recorded in a traceable manner, especially for works in existing structures.
Safety, Environment, and Legal Framework
Work in the foundation area requires special protective measures against fall protection hazards, burial, and gas or water ingress. Emissions such as noise, dust, and vibrations should be minimized, for example by limiting noise emission and dust exposure. For interventions in load-bearing existing elements, a structural analysis and required permits must be obtained. Legal requirements regarding waste, groundwater protection, and soil protection must be observed; project-specific coordination with the authorities is recommended, without these notes constituting a final legal assessment of the individual case.
Tools and Methods Near Foundations
The choice of tool depends on material, accessibility, and protection targets. The following approaches have proven themselves in the foundation environment:
Open and Work Concrete in a Targeted Manner
- Concrete pulverizer for removing foundation steps, cropping pile heads, and exposing connecting reinforcement.
- Combination shears and hydraulic shear (demolition shear) for cutting rebars, embedded parts, and light steel sections.
- hydraulic power pack as the energy source for mobile, compact operations in confined excavation pits.
Release Rock and Massive Elements with Low Vibration Levels
- Hydraulic splitter for controlled widening of borehole rows to precisely release rock noses or massive blocks.
- Rock wedge splitter for pinpoint corrections of the foundation base in rocky ground.
- Gentle material removal reduces crack formation and protects adjacent structures, for example in inner-city special demolition or during rock breakout and tunnel construction.
Practice-Oriented Use Cases
The following scenarios illustrate typical interfaces between foundation methods and selective deconstruction:
Subsequent Foundation Strengthening in Existing Structures
An existing foundation is enlarged, load level increases. Procedure: expose, mark the target geometry, locally remove concrete with a concrete pulverizer, expose and connect the reinforcement, cast the new foundation slab. Low vibration levels protect sensitive building elements.
Pile Head Preparation for Bored Piles
After curing, the pile head is cropped to design elevation. Concrete is opened with a concrete pulverizer, reinforcement is then cut with a steel shear or multi cutters, and the bearing surface is leveled.
Excavation Pit Enlargement in Rock
Local rock protrusions disturb the foundation base. Set a borehole drilling row, use a hydraulic splitter, release blocks in a controlled manner, excavate material, check and compact the base.
Application Areas and Linkage to Practice
Foundation methods rarely stand alone. They are closely linked to the following application areas:
- Concrete demolition and special demolition: Selectively opening and working foundations, adapting to new load paths.
- Building gutting and cutting: Preparatory measures for core drilling, slots, and breakthroughs in the foundation zone.
- Rock breakout and tunnel construction: Creating adit and shaft bases, leveling bases in hard rock. Methods overlap with rock demolition and tunnel construction.
- Natural stone extraction: Precise splitting of rock that can be used as gravel or block material for foundations.
- Special demolition: Work under operation, in sensitive zones, or with restrictive emission limits, where low-vibration techniques are advantageous.