Exponent has extensive experience in evaluating the performance of foundation systems – structural elements that a support a structure and connect it to the ground. Because our civil engineers and geologists can draw on our in-house expertise in the areas of structural, materials, and mechanical engineering, Exponent can provide a multi-disciplinary approach to an independent review of a foundation design or assessment of foundation failure. They can generally be classified into two broad categories: shallow foundations and deep foundations.
Shallow foundations transfer structural loads to near-surface soils. They are typically used for small to medium-sized buildings when near-surface soil conditions are adequate. Shallow foundations are occasionally used for large structures when the near-surface ground conditions are particularly favorable, such as the presence of shallow bedrock. Shallow foundations can also be used where unfavorable near-surface soil condition have been modified by ground improvement techniques. These include removal and recompaction, stone columns, compaction grouting, soil mixing, and soil surcharging. Due to their relatively low cost and ease of construction, shallow foundations are far more prevalent than deep foundations.
Deep foundations transfer some of a structure’s entire load to deeper soils. Deep foundations are considerably more expensive and complex than shallow foundation systems. Because the bearing capacity of soil often increases with depth, deep foundations generally possess higher structural load capacities relative to shallow foundations. Hence, deep foundations typically are used when adverse near-surface soil conditions are encountered (i.e., soft clays, collapsible soils, and/or expansive soils) and structural load requirements are sufficiently large to warrant the additional cost of deep foundations, or when a high lateral load capacity is needed.
Our services include:
- Emergency response to imminent foundation failure
- Root cause analysis of the cause(s) of foundation, settlement, lateral movement, or cracking
- Analysis of the nature and extent of damage to real property from foundation system failure
- Evaluation of differing site condition claims arising from construction of deep foundations
- Cost analysis, delay impacts, and acceleration evaluation for construction projects involving deep foundations
- Analysis and field evaluation of foundation performance during earthquakes
- Analysis and field evaluation of foundation performance as a result of adjacent construction, e.g., excavations near an existing foundation
- Evaluation of field test data (e.g., vertical and lateral load tests of deep foundation elements, pile driving records, pile test data)
- Evaluation of moisture intrusion problems
- Analysis of causes, timing and repairs for foundations on expansive soils and bedrock, collapsible soils, highly compressible soils, and other difficult ground conditions.
- Field investigation of foundations, including:
- Determining the as-built condition of the foundation or retaining structure
- Geologic mapping
- Documentation of the condition of buildings and structures affected by foundation failure
- Collection of subsurface data by excavation and logging of test pits, small-diameter borings and rock cores, and downhole logging of large-diameter borings
- In-situ subsurface testing
- Installation and monitoring of instrumentation to measure ground movement and groundwater levels
- Geotechnical laboratory testing for measuring rock and soil engineering properties
- Development of repair recommendations