A tank foundation supports cylindrical or rectangular storage tanks, compensates for ground irregularities, and protects against settlement, tilting, and uplift. It is the interface between subsoil, tank bottom, and periphery (pipelines, containment areas, drainage). In planning, execution, maintenance, and deconstruction, structural, geotechnical, and concrete-technology requirements meet practical workflows. Especially during deconstruction, the choice of low-emission, low-spark methods plays a central role – concrete demolition shears and hydraulic rock and concrete splitters are frequent tools in concrete demolition and special deconstruction.
Definition: What is meant by tank foundation
A tank foundation is the load-bearing and leveling construction layer beneath stationary storage tanks for liquids or gases. It distributes loads from dead weight, fill level, wind, and earthquakes to the ground, prevents inadmissible settlements, and provides a flat bearing for the tank bottom. Typical types are the ring foundation (ringwall), the base slab (solid slab), combined solutions with piles or deep foundation, as well as engineered gravel and sand cushions with bituminous or mineral surface layers. Depending on the medium and location, additional functions come into play: chemical resistance, frost protection, dissipation of stray currents, leak detection, and secondary containment.
Structure and construction types of tank foundations
The structural build-up depends on tank diameter, permissible ground bearing pressures, environmental requirements, and operational demands. Ring-shaped reinforced concrete foundations with an internal sand or asphalt bed are common; for high loads or soft subsoil, massive concrete slabs or pile cap slabs are chosen. The decisive factor is a permanently even, compacted, and dimensionally accurate surface for the tank bottom, including defined falls and drainage.
Design, subsoil, and load assumptions
Design considers permanent and variable actions: dead weight, operating fill levels, temperature variations, wind, earthquakes, and uplift under high groundwater. Subsoil investigations provide parameters for bearing capacity, settlement behavior, and frost susceptibility. The objective is a stress and deformation state that secures the tank bottom’s flatness over the long term and minimizes differential settlement.
Key influencing factors
- Subsoil: grain structure, consistency, groundwater level, organic content
- Tank geometry: diameter, height, shell stiffness, anchorage
- Environment: freeze–thaw cycles, chemical exposure, seismic intensity
- Operation: temperature profiles, filling cycles, inspection intervals
Materials and layer build-up
Common are mineral base layers (crushed stone, gravel), hydraulically bound base layers, bituminous wearing courses, and reinforced concrete for ring walls or slabs. Depending on the medium, chemically resistant concretes, coatings, or membranes are used. In containment areas, liquid-tight surfaces are required that limit crack widths in a controlled manner.
Typical layer sequence
- Prepared subgrade and geotextile (optional)
- Frost protection and base layer with defined compaction
- Ring foundation or base slab of reinforced concrete
- Levelling layer (sand, mortar, mastic asphalt)
- Tank bottom (steel plate with annular plate)
Execution and quality assurance on site
Execution requires controlled compaction, adherence to flatness and elevation tolerances, and documented concrete handling. Before setting the tank, the surface is cleaned, inspected, and reworked if necessary.
Inspection points
- Flatness, roundness, and elevation tolerances of the bearing surface
- Compaction records and bearing capacity tests
- Concrete quality, reinforcement placement, joints, and edges
- Drainage, falls, and connection details
Waterproofing, leak detection, and secondary containment
Depending on the medium and location, additional measures are provided: catch basins, sealing layers beneath the tank bottom plate, capillary-breaking layers, and leak monitoring. The aim is to detect escaping substances early and retain them within the system. In practice, combined solutions are used that combine hydraulic tightness and mechanical durability.
Typical damage and causes
Damage often results from differential settlement, inadequate compaction, chemical attack, or thermal restraint stresses. It becomes visible as cracks, spalling, edge breakouts, voids, or loss of flatness, which can induce stresses in the tank bottom.
Early detection and monitoring
- Regular leveling surveys and geometry checks
- Documentation of crack formation and edge damage
- Control of drainage and water conveyance
Repair and strengthening of tank foundations
Depending on the damage pattern, measures range from local repairs to partial or complete renewal. The goal is to restore load-bearing capacity, flatness, and tightness with minimal operational interruption.
Typical methods
- Packing/underfilling and leveling with mineral or resin-bound mortars
- Concrete replacement at edges and joints, surface reprofiling
- Ring foundation widening or raising to redistribute loads
- Ground improvement (e.g., injections) in suitable cases
For interventions in concrete cross-sections, concrete demolition shears offer advantages: controlled removal, good separation of concrete and reinforcement, reduced noise, and fewer secondary effects. To open massive areas, rock and concrete splitters can be used to initiate cracks in a targeted way and keep demolition low-vibration.
Deconstruction of tank foundations: methods and equipment
Deconstruction generally follows an orderly sequence: emptying and degassing the tank, dismantling the periphery, cutting up the tank, exposing and demolishing the foundation, separating material streams, and proper disposal or recycling.
Sequence and tools at a glance
- Tank cutting: tank cutters are used for low-spark, thermally minimized cuts on the tank shell and roof, especially in sensitive areas.
- Concrete demolition: concrete demolition shears crush ring foundations and slabs in a controlled manner, protect adjacent components, and separate reinforcing steel.
- Controlled splitting: rock and concrete splitters as well as rock splitting cylinders create controlled fracture planes in massive cross-sections or rock layers.
- Steel separation: steel shears, combination shears, and multi cutters cut reinforcement, anchors, lines, and sections.
- Power supply: hydraulic power packs feed the hydraulic tools as required.
The use of such methods aligns with typical application areas: concrete demolition and special deconstruction at the foundation, strip-out and cutting at the periphery and tank, and—where the subsoil is rocky—rock excavation for targeted removal within the work area. In particularly sensitive scenarios, special operations with strictly limited emissions and low-vibration methods are required.
Special boundary conditions: groundwater, uplift, frost, and earthquakes
High groundwater levels can lead to uplift and moisture ingress; drainage, capillary-breaking layers, and waterproofing must be planned accordingly. Freeze–thaw cycles require adequate frost-protection layers. In seismic regions, ductility and crack width control are emphasized, as is a low-settlement foundation.
Interfaces: tank bottom, annular plate, and connections
The transition between ring foundation and tank bottom (annular plate) is sensitive in terms of geometry and materials. A defined bearing line, cleanly formed chamfers, and a uniform support minimize notch and edge stresses. Connection details for equipotential bonding, leak lines, and measurement sensors should be coordinated early.
Occupational safety and emission reduction
Work on tank foundations requires careful work preparation, coordination, and protective measures. Low-spark cutting methods, dust extraction, water misting, and noise reduction are crucial in many facilities. In areas with increased ignition risk, low-ignition-source methods are preferred and permit-to-work procedures are followed. The notes described here are general and do not replace an object-specific risk assessment or regulatory requirements.
Outlook: lifecycle, sustainability, and recycling
A robustly planned tank foundation reduces maintenance effort and facilitates later adaptations. During deconstruction, selective separation of concrete, reinforcement, and asphalt supports high-quality recycling. Equipment concepts with precise fragmentation—such as via concrete demolition shears or rock and concrete splitters—improve material stream quality and reduce transport and disposal efforts.
Fields of application and practical relevance
Tank foundations are found in refineries, chemical and tank farms, water and wastewater facilities, agriculture, and energy supply. Depending on the location, design and requirements vary: from a simple ring wall on competent sand to a pile cap slab in soft soils. During conversion or deconstruction, the mentioned devices from Darda GmbH are part of the technical chain in many scenarios, while no single method universally satisfies all requirements—the decisive factors are subsoil, environmental conditions, and operating limits.