{"id":19222,"date":"2025-09-16T12:58:17","date_gmt":"2025-09-16T10:58:17","guid":{"rendered":"https:\/\/www.darda.de\/soil-failure"},"modified":"2026-04-13T17:35:02","modified_gmt":"2026-04-13T15:35:02","slug":"soil-failure","status":"publish","type":"page","link":"https:\/\/www.darda.de\/en\/knowledge\/soil-failure","title":{"rendered":"Soil failure"},"content":{"rendered":"
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Soil failure describes the failure of the ground under load. The topic is equally relevant to construction and deconstruction practice: when removing foundations, opening excavation pits, in tunnels, and during rock works. Those who deconstruct components with concrete demolition shears or release massive blocks with rock and concrete splitters<\/a><\/em> influence load paths, groundwater flows, and the stability of temporary construction stages. Careful planning and a low vibration<\/strong> approach help prevent ground failure and protect adjacent structures. Robust method statements, coordination with dewatering and shoring, and staged sequences minimize transient overloads and unforeseen redistributions.<\/p>\n

Definition: What is meant by soil failure?<\/h2>\n

Soil failure refers to the bearing capacity failure of the subsoil<\/strong> due to excessive loading. The soil experiences shear failures and can no longer carry the load; the result is sudden settlements, sliding, or punching through the foundation base. This is distinct from hydraulic heave<\/strong> (base heave, uplift, piping): uplift forces and groundwater flows lift the base of the excavation or wash out fine-grained constituents. It is also distinct from ordinary consolidation settlements<\/em>, which are time dependent deformations without shear failure. Both phenomena affect shallow foundations, excavation pits, shafts, and edge areas of deconstruction and demolition zones and must be verified for temporary as well as final states.<\/p>\n

Forms of soil failure and typical triggers<\/h2>\n

In practice, different failure patterns often occur in combination: bearing capacity failure in shallow foundations, near-edge soil failure due to concentrated point loads (e.g., in front of excavation slopes), hydraulic heave with a lowered ground surface elevation or deep excavation base, as well as localized liquefaction under dynamic loading. Additional drivers include loss of fines by seepage, cyclic loads, stress relief due to excavation, and abrupt load rerouting during dismantling. Triggers include excessive base pressures, unfavorable groundwater conditions, inadequate ground improvement, and unplanned load redistributions during deconstruction, especially in layered or anisotropic soils.<\/p>\n

Bearing capacity failure under slabs and foundations<\/h3>\n

When loads exceed the soil\u2019s shear strength, slip surfaces form; cone or wedge shaped bulging follows, accompanied by abrupt settlements. During deconstruction, this can occur when load bearing components are removed and remaining foundations concentrate loads into the ground. Undrained soft clays react brittle with small deformation reserves, while dense sands may show pronounced edge bulging; in both cases, limiting eccentricities and avoiding high edge stresses is essential.<\/p>\n

Hydraulic heave in excavation pits<\/h3>\n

With sandy or soft soils and high groundwater levels there is a risk of base heave. Uplift and seepage flows overcome the self weight of the base; consequences include heaving, water inflows, or piping. This also concerns shafts, channels, and deep utility trenches in the vicinity of deconstruction sites. The risk increases as the upward hydraulic gradient approaches a critical level; filter stability and base tightness should be checked and safeguarded with suitable measures.<\/p>\n

Near-edge loading from construction logistics<\/h3>\n

Heavy equipment, material storage, or demolition debris near slopes and sheet pile walls increase base pressure at the edge. Local soil failure can initiate along the excavation wall if stand off distances<\/strong> are not observed. As a rule of thumb, keep significant concentrated loads set back from the crest by at least an order of the excavation depth unless a project specific verification allows smaller distances.<\/p>\n

Vibrations and low-vibration alternatives<\/h3>\n

Additional dynamic loading promotes soil loosening and pore water overpressure. Rock and concrete splitters<\/strong> as well as concrete demolition shears<\/em> work with low vibration and reduce risk compared to percussive methods. This can be decisive in sensitive temporary conditions. Selecting methods with limited impulse energy and controlled frequency content further reduces the potential for pore pressure build up and settlements in adjacent structures.<\/p>\n

Relation to concrete demolition and special deconstruction<\/h2>\n

During selective deconstruction, load paths change step by step. When walls, beams, or columns are removed with concrete demolition shears, the point loads on remaining supports increase. In combination with soft or water saturated subsoil, this can lead to soil failure<\/em>. Planned sequencing of removal, temporary shoring, and controlled downsizing of large components reduce load peaks. Rock and concrete splitters<\/strong> enable targeted breaking of foundations or rock edges without introducing additional vibrations into the ground. Where necessary, temporary underpinning, pre unloading of critical supports, and intermediate bearing pads distribute loads during transitional phases.<\/p>\n

Example: Removing foundations with concrete demolition shears<\/h3>\n

When removing foundations, the width of the remaining bearing should be dimensioned so that no impermissibly high edge pressures arise. Section by section downsizing with concrete demolition shears limits block sizes and avoids concentrated point loads from large demolition pieces. Leaving load cores<\/em> (kern zones) in place until the end of removal and early unloading of heavy superstructures reduces the risk of soil failure. Load spreading mats or temporary blinding layers can further reduce contact pressures from machines and debris during interim stages.<\/p>\n

Rock demolition and tunneling: splitting instead of blasting<\/h3>\n

In rock, controlled crack initiation with rock and concrete splitters<\/strong> makes load redistribution manageable. In tunnel headings or when opening caverns, a stepwise, low frequency approach reduces the risk of local loosened zones and decreases the influence on adjacent unconsolidated rock areas. Short rounds with prompt support installation and careful face control enhance stability. Hydraulic power units<\/a> provide the required energy without introducing impact type loads into the ground.<\/p>\n

Planning and design: factors influencing stability<\/h2>\n

Safety against soil failure depends on soil, geometry, groundwater, and construction stage. Key factors are:<\/p>\n