Calgary grew fast after the 1950s oil boom. The city spread over glacial tills, lacustrine clays and alluvial terraces. Many early subdivisions sit on soils that are naturally dry but prone to drastic volume changes when moisture shifts. That is where unsaturated soil analysis becomes critical. Unlike saturated conditions, partially saturated soils behave differently. Suction forces hold particles together. Once water enters, those forces drop. We measure suction, water retention and shear strength under controlled moisture. It is not a standard lab test. It requires sealed sampling and specialised equipment. In Calgary, ignoring this step has led to cracked slabs and tilted walkways within a few years. Before we start any foundation design, we run ensayo triaxial on undisturbed samples under unsaturated conditions to capture real field behaviour.
Suction loss in Calgary tills can reduce bearing capacity by 40 percent after wetting. Unsaturated soil analysis prevents that risk.
Methodology and scope
A common mistake we see in Calgary is treating all tills as uniform. They are not. Glacial till here contains silt, sand, clay and cobbles in varying proportions. When dry, it feels strong. Builders sometimes skip a proper unsaturated soil analysis because the ground looks firm. Then spring thaw or irrigation adds moisture. The soil loses suction. Settlement or heave follows. We have documented cases where bearing capacity dropped by 40 percent after wetting. To avoid that, we perform suction-controlled tests using the axis-translation technique. We also run filter paper tests for total suction. Parameters we measure include:
Soil-water characteristic curve (SWCC)
Effective stress parameters under unsaturated conditions
Collapse potential upon wetting
Swelling pressure for expansive clays found in parts of southeast Calgary
This data helps engineers predict how the soil will react years after construction.
Technical reference image — Calgary
Local considerations
Calgary sits at 1,048 metres above sea level. The climate is semi-arid with long dry spells. That keeps shallow soils in a highly unsaturated state. When new developments add irrigation or alter drainage, the moisture front moves down. Unsaturated soil analysis captures this transition. Without it, foundations built on dry, stiff clay can experience up to 75 mm of heave after wetting. In 2013, widespread flooding in southern Alberta triggered ground movement in several neighbourhoods. Many homeowners blamed foundation cracks on the flood itself. In reality, the soil had been unsaturated for decades. Once it finally got wet, it swelled. We now recommend unsaturated soil analysis for any site with plastic clay within 3 metres of grade.
Measured via WP4C dewpoint and axis-translation apparatus
Total suction range
0 to 30 MPa depending on moisture content
Unsaturated shear strength
Triaxial tests with controlled suction (50 to 400 kPa)
Collapse potential
Double-oedometer test per ASTM D5333 (CFEM Ch 4) (CFEM Ch 4) (CFEM Ch 4) (CFEM Ch 4) (CFEM Ch 4)
Swelling pressure
Constant volume method up to 800 kPa in clay-rich tills
Volumetric water content
Measured on undisturbed Shelby tube samples
Associated technical services
01
Suction-controlled triaxial testing
We perform consolidated drained triaxial tests with controlled suction using the axis-translation method. Samples are trimmed from undisturbed Shelby tubes or block samples. We apply suction levels from 50 kPa to 400 kPa. Results include effective stress parameters c' and phi' under unsaturated conditions. This data is essential for slope stability and foundation design in Calgary's dry tills.
02
Soil-water characteristic curve determination
Using a combination of WP4C dewpoint potentiometer and pressure plate extractors, we generate the SWCC from saturation to residual conditions. The curve defines how much water the soil holds at each suction level. Engineers use it to model infiltration, heave and collapse potential. We provide fitting parameters for Fredlund-Xing or van Genuchten models.
Why is unsaturated soil analysis needed in Calgary?
The reference range for this service in Calgary is CA$1.340 - CA$3.990. The final price depends on the project scope and volume.
How much does unsaturated soil analysis cost in Calgary?
The typical range for a full unsaturated soil analysis including SWCC and suction-controlled triaxial testing is CA$1,340 to CA$3,990. Final cost depends on sample quantity, test complexity and depth. We recommend contacting us with your project scope for a detailed quote.
What is the difference between SWCC and standard moisture content?
Standard moisture content tells you how much water is in the soil at one point in time. The SWCC shows how the soil holds or releases water across a range of suctions. It is a fundamental curve for predicting volume change, permeability and shear strength in unsaturated soils.
Can unsaturated soil analysis detect swelling or collapse potential?
Yes. The SWCC combined with double-oedometer tests reveals collapse potential upon wetting. Swelling pressure is measured directly on undisturbed samples. In Calgary's clay-rich tills, swelling pressures can exceed 200 kPa. Knowing this early prevents structural damage.
