Prepare for your Soil and Foundation Quality Control interview with these questions covering soil tests, foundation checks, and construction standards. Click on questions to view detailed answers.
The Standard Penetration Test (SPT) is a common field test used to find out the strength and density of granular soils (like sand and gravel) and the consistency of cohesive soils (like clay).
How it works: A standard split-spoon sampler is driven into the ground by dropping a hammer from a fixed height. We count the number of hammer blows (called the "N-value") needed to drive the sampler a certain distance (usually 300 mm).
Importance in Foundation Design:
Dewatering is the process of removing groundwater or surface water from a construction site, especially from excavation areas, to make them dry and stable for work.
How it's done: Common methods include:
Why it's needed for foundations:
The choice between shallow and deep foundations depends on several factors, primarily related to soil conditions and structural loads. Critical quality control aspects differ for each type.
Factors Influencing Choice:
Quality Control Aspects:
Shallow Foundations (e.g., Spread Footings, Rafts):
Deep Foundations (e.g., Piles, Piers):
Expansive soils (like certain clays) swell when wet and shrink when dry, causing significant ground movement that can severely damage foundations. Managing quality control for such sites requires special attention.
Key Quality Control Strategies:
Liquefaction is a phenomenon where saturated, loose granular soils (like sand or silt) temporarily lose their strength and behave like a liquid during an earthquake or rapid loading. This happens because the shaking causes the soil particles to lose contact with each other, and the water pressure between them increases, making the soil unable to support loads.
Implications for Foundation Design:
Quality Control (QC) and Mitigation Strategies:
If a site is identified as having liquefaction potential (through SPT, CPT tests, and seismic studies), QC focuses on implementing mitigation measures:
Instrumentation and monitoring involves installing sensors and devices in and around a construction site to measure ground movement, water pressure, stresses, and deformations. For large foundation projects, especially those with deep excavations or difficult soil, it's a vital part of quality control and risk management.
Contribution to Quality Control:
Common Instruments Used:
Geotechnical reporting is the process of documenting all soil investigations, lab tests, field tests, and recommendations related to the ground conditions of a construction site. It's a fundamental part of foundation quality control because it provides the essential information needed to design and build safe and stable foundations.
Importance in Foundation Quality Control:
Information a Geotechnical Report Should Contain: