Glossary

Look up definitions here! To find the definitions and terms used in the Home Building on Alberta Soils online course, please click on the letters below.

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Active Zone — Many expansive soil problems can be prevented by proper moisture control within its active zone. The depth of the active zone can be influenced by:

Total precipitation
Evaporation rate
Ground cover
Depth and type of foundation
Service lines
Established vegetation

Adfreeze — Occurs when frost-susceptible soil freezes to the foundation wall then lifts up on the wall, as the soil heaves.

Adhesive Forces — Attractive force between soil and water molecules. It is a key component of capillary action in fine-grained soils.

Allowable Bearing Capacity — See Bearing Capacity.

Bearing Capacity — The bearing capacity of a soil can be defined as the pressure it can withstand. The allowable bearing capacity is the design maximum amount of pressure for a particular subgrade of soil. This capacity is determined by evaluating the subgrade conditions within the influence zone of the foundation and as far down as the significant depth. The serviceability bearing capacity of a soil relates to the amount of settlement that is allowable for the foundation.

Bearing Inspection — A bearing inspection is a visual inspection completed by qualified geotechnical personnel. It is completed to ensure that:

The subgrade was not significantly disturbed during excavation.
The subgrade is not significantly different from what was identified during the initial geotechnical investigation.

Bedrock — Most of the bedrock encountered in developed areas of Alberta is sedimentary bedrock that consists of sandstone, siltstone, mudstone (also known as shale) or claystone. Bedrock in Alberta can normally be excavated to nominal depths with standard excavation equipment.

Bored Cast-in-place Concrete Piles — See Drilled Piles.

Borehole — A borehole is a small diameter hole drilled from the soil surface to collect soil samples. A typical borehole is 150 mm (6") in diameter and can go to depths of over 30 m (100 ft)!

Builder's Resource Manual — Any builder registered with The Alberta New Home Warranty Program receives a copy of this manual. It provides a description of the Warranty Certificate and the mandatory clauses that all members must use in their purchase/construction documents.

CANFEM — Canadian Foundation Engineering Manual. Provides a soil classification system based on particle size.

Capillary Action — The ability of a narrow tube to draw a liquid upwards against the force of gravity. Capillary action occurs when the forces between a liquid and a solid are stronger than the forces within the liquid.

Capillary Fringe — In nature, the zone of soil immediately above the groundwater table.

Chemical Weathering — During this process, the mineral composition of the rock is changed due to the influence of water, oxygen, and carbon dioxide.

Classification — See Soil Classification.

Clay — Clays and silts are both fine-grained soils, but they behave quite differently because of plasticity. Distinguishing between clays and silts is often best left to qualified geotechnical personnel. However, you can refer to the list below to help you identify clays in the field.

Low to high plasticity. It is possible to roll a 1/8" (3 mm) thread at certain moisture contents.
Not dilatant (water sheen does not appear on a wet pat of soil when shaken or struck).
Does not wash easily from hands and other surfaces, requires scrubbing.
Has a smoother feel than silt, more greasy than velvety.
Dries more slowly than silt.

Clay Cap — Layer of clay added on top of existing backfill soils to decrease their permeability and allow surface water to flow away from the foundation.

Coarse-grained — A coarse-grained soil is differentiated from a fine-grained soil based on its particle size. If more than half of a soil sample is trapped on a No. 200 sieve, the soil is classified as coarse-grained. Individual coarse-grained particles are visible to the naked eye (bigger than 0.075 mm in diameter).

Cohesive Forces — The attractive force that holds together individual water molecules in liquid form.

Compaction — Soil compaction is the process of increasing the density of a soil by packing the particles closer together and reducing the volume of air.

Compaction Testing — In Alberta, nuclear moisture-density gauges are primarily used to test the compaction level of a fill soil. This type of gauge gives you the existing moisture-density relationship of the material you are currently testing. This is a non-intrusive test of soil conditions.

Composition — See Soil Composition.

Compression — When a soil is compressed, the soils particles are rearranged, the volume of voids in the soil is reduced, and the soil becomes more dense. Compression tends to occur more rapidly in coarse-grained soils due to their more stable particle arrangement and higher permeability

Concrete Gravity Retaining Wall — Slope stabilization measure. Concrete gravity retaining walls are used when space is limited, under heavy loading conditions, or for high risk areas. A common construction consists of a vertical wall connected to a cantilever base comprised of cast-in-place reinforced concrete.

Consolidation — Consolidation is a form of compression that relates to a reduction in the water content of a soil. It occurs in all soils, but occurs more quickly in coarse-grained soils due to their high permeability; the faster water can be removed from a soil, the faster it will consolidate.

Cut Back Slope — Slope stabilization measure which involves cutting down the slope to a more stable grade and/or orientation.

Diffuse Double Layer — A water layer than can form around clay particles. The thicker this layer becomes, the further apart the clay particles are pushed and the more the clay swells.

Drilled Piles — Type of underpinning. Boreholes are drilled into soil with sufficient strength properties, to a depth determined by a geotechnical engineer. The boreholes are then filled with concrete and steel rebar in accordance with the engineer’s design specifications.

Dynamically Driven Piles — Type of underpinning advanced by mechanical or dynamic means. This is done by repeatedly dropping a mass of known weight on the top of the pile, from a controlled height.

Exclusion Clause — Excludes or limits liability in relation to matters arising from the breach of an agreement or from the negligence of one party in the performance of their obligations to another.

Fill — Fill is a deposit made by man and as such, it can be extremely variable.

Fine-grained — A fine-grained soil is differentiated from a coarse-grained soil based on its particle size. If more than half of a soil sample passes through a No. 200 sieve, the soil is classified as fine-grained. Individual fine-grained particles are not visible to the naked eye (smaller than 0.075 mm in diameter). Fine-grained soils are also often classified based on their plasticity, i.e. how they behave.

Fluvial — Of, or pertaining to, rivers. Fluvial deposits come from rivers. Although commonly associated with coarse-grained soil such as gravel and gravelly sand, they can also include loose or soft silt, sand, and clay deposits. Generally, soils deposited within the channel of the river tend to be more coarse-grained, whereas soils deposited on the banks of rivers tend to be more fine-grained.

Frost Action — As the temperature above ground drops below zero, a freezing front advances down into the soil. When water in coarse-grained soils freezes, it causes the soil to expand by roughly 9%. When water in fine-grained soils freezes, it causes the soil to expand by much more than 9%. This phenomenon is attributed to the formation of ice lens.

Geotechnical Restrictive Covenant — A restrictive covenant is a legal obligation imposed in a deed by the seller upon the buyer of real estate to do or not to do something (e.g. maintain a property in a reasonable state of repair, to preserve a sight-line for a neighbouring property, not to run a business from a residential home, or not to build on certain parts of the property). A geotechnical restrictive covenant is specific to use of the property from a geotechnical standpoint, such as type and size of foundation, drainage requirements, excavation limits and set back limits from slopes.

Glacial Deposits — Of, or pertaining to glaciers. Three common types of deposits left by glaciers include: till, glaciofluvial and glaciolacustrine.

Glaciofluvial — Glaciofluvial deposits were left behind by rivers that helped drain melting glaciers. These deposits are typically composed of coarse-grained soil.

Glaciolacustrine — Glaciolacustrine deposits were created by temporary lakes that formed when glaciers were melting. These deposits usually have a high concentration of fine-grained soil and are the foundation for some of the best agricultural lands in Alberta.

Heel Test — This non-intrusive test of soil conditions is done by thumping on the ground with your heel to see if the soil 'feels' sufficiently solid.

Helical Piles — Type of underpinning, typically proprietary in nature. Helical piles consist of a straight section of pipe that has helical flights welded to it. These piles are advanced using hydraulic equipment which literally screws the helical flights into the ground.

High Pressure Grout — The grouting procedure fills voids that may have developed between the bottom of the foundation element and the underlying soils. With adequate pressures, the structure can be raised – to some extent. This type of repair is typically used when:

The amount of movement required is quite small.
The underlying soils are capable of supporting the structural loads.
The additional weight of the grout is not likely to significantly increase the loads on the subsoils.

Indemnity Clause — One party agrees to indemnify another against the consequences of the other party’s liability through third parties. Indemnity clauses are another way to pass the risk and are generally included in any developer’s contracts.

Influence Zone — The influence zone is the area under the foundation that is affected by the weight of the building. It is common practice to assume that this influence zone is represented by the area enclosed by a line drawn at one horizontal to one vertical (1H:1V) downwards and outwards from the edge of the footing.

Lacustrine — A type of deposit that comes from lakes which previously occupied the area. They are fine-grained soils that have settled through the water and accumulated on the lake bottom, typically leaving them in a soft condition. Many of the swelling clays encountered in Alberta originate from lacustrine deposits.

Level Survey — Conducted by experts to determine if there are variations in the floor elevation.

Limitation Period — Period of time within which a civil action must be initiated. If a person with a civil claim does not initiate legal action within the specified period of time, they will lose the right to bring the claim and recover any damages and/or other relief.

Loess — Loess is a predominantly silt size eolian (wind) deposit. The thicker and more ancient loess was deposited during the retreat of the last glaciers, usually originating from silt beds of glacial outwash or shallow streams. More recent deposits are wind-blown deposits in semi arid to arid regions. This is a type of metastable soil, and is characterized by a low density and porous structure.

Mechanically Stabilized Earth — Slope stabilization measure. A Mechanically Stabilized Earth (MSE) slope involves installing a series of horizontal geogrid layers between compacted soil fill layers of specified thickness. This improves the internal stability of the slope.

Meniscus — The curved top of a column of liquid in a small tube. It is formed because the attractive forces between the soil and the water molecules (adhesive forces) are stronger than the cohesive forces between individual water molecules.

Metastable Soils — Metastable soils are abnormally loosely deposited soils that may collapse when saturated with water. The most common metastable soil is loess. Metastable soils are porous, temporarily stable and have a low density. The temporary strength of metastable soils comes from internal support conditions that developed as the soil was deposited. These conditions can include:

Capillary tension
Cementing agents
Other agents

Micro Piles — Type of underpinning. Micro piles are smaller versions of concrete piles and dynamically driven piles.

Minimum Time Lag Requirements — This is the minimum wait time between the end of fill placement and the start of construction.

Moisture-Density Relationship — This is the range of moisture required to maximize the effect of compaction. It varies depending on the soil type.

Organic Soil — An organic soil is typically identified by its colour (usually dark brown to black), odour (decay), spongy feel and fibrous texture. Typical organic soils found in Alberta include peat, muskeg and common topsoil.

Particle Size — The two common standards used are the American Society for Testing Materials (ASTM) and the Canadian Foundation Engineering Manual (CANFEM). The table below gives you more details on these categories.

Description	Particle Size (mm)
Description	ASTM	CANFEM
Boulders	> 300 mm	> 200 mm
Cobbles	75 mm to 300 mm	60 mm to 200 mm
Gravel	4.75 mm to 75 mm	2.0 mm to 60 mm
Sand	0.075 mm to 4.75 mm	0.06 mm to 2.0 mm
Silt	0.005 mm to 0.075 mm	0.002 mm to 0.06 mm
Clay	< 0.005 mm	< 0.002 mm

Permeability — Permeability relates to how easily one material can pas through another. In the case of soil permeability, we are typically looking at how quickly water can pass through. Water will pass more quickly through a soil with high permeability (i.e. gravel) than a soil with low permeability (i.e. clay).

Phase Relationship — Soil composition is often described with phase relationships. The three possible phases are air, water and solids.

Physical Weathering — During the process of physical weathering, large rocks are broken down into smaller and smaller particle sizes. This can be done through erosion by wind, water, ice, freeze/thaw cycles, or root propagation.

Plasticity — Used to determine the behaviour of the fine-grained portion of a soil. When a soil has a high plasticity, it can be molded into any shape without changing volume or cracking. Essentially, a soil with high plasticity will have the consistency of dough or Plasticine™.

Pore Air — When discussing soils, a void space that is filled with air is often referred to as pore air.

Pore Water — When discussing soils, a void space that is filled with water is often referred to as pore water.

Proctor Test — The proctor test is used to identify the moisture-density relationship of a soil.

In the Standard Proctor test, a specific amount of force (a.k.a. level of effort) is used to compact a soil at increasing moisture contents, until the maximum dry density and optimum moisture content are determined. The level of effort used in the Standard Proctor test is representative of typical compactive effort used in the 'real-life' field case.
The Modified Proctor is based on a higher level of effort than the Standard Test. It is considered more representative of the level of effort used in certain large-scale stringent projects such as earth dams or heavy traffic areas such as aircraft taxiways.
The One-Point Proctor is the maximum dry density possible at a certain moisture content. A One-Point Proctor is sometimes used in problem soils such as silts or clays that have very high natural moisture content.

Rammers — Designed for compaction in confined areas. Percussion tools (rammers) are available as backhoe attachments or as walk-behind models such as 'Jumping Jacks'. Rammers are often best suited for cohesive soils. Rammers are similar to sheepsfoot rollers.

Refusal — When a drill rig or excavator reaches a hard enough layer that they can not penetrate it without damaging the equipment.

Rollers — Mainly used for large scale compaction, such as rough grading operations. Smaller "walk-behind" versions of these rollers are available and can be useful in small areas.

Secant Piles — Slope stabilization measure. Involves advancing a connected series of large deep cast-in-place piles founded at a design depth below the volume of slope undergoing movement.

Serviceability Bearing Capacity — See Bearing Capacity.

Significant Depth — The significant depth is defined by CANFEM as the depth at which the net increase in soil stress under the weight of the structure is less than 10% of the applied load, or less than 5% of the effective stress in the soil at this depth, whichever is less.

Silt — Silts and clays are both fine-grained soils, but they behave quite differently because of plasticity. Distinguishing between clays and silts is often best left to qualified geotechnical personnel. However, you can refer to the list below to help you identify silts in the field.

No plasticity or slight plasticity. It is difficult to roll a 1/8" (3 mm) thread, at any moisture content.
Dilatant (water sheen appears on a wet pat of soil when shaken or struck).
Washes easily from hands and other surfaces.
Grittier feel than clay, more velvety than greasy.
Dries more quickly than clay.

Slope Stabilization Measures — Process by which a slope failure is corrected. Can include minor or major repairs, such as:

Minor repairs:
- Control of failure condition
- Cutting back slope
- Soil berm at toe
Major repairs:

Slough Bottom Deposit — Slough bottom deposits are recent deposits that tend to occur in low lying areas where water is able to pond. Fine-grained particles settle down through the water and accumulate at the pond base. Sloughs typically consist of loose silt, sand, soft clays, and usually a significant portion of organic material.

Soil Berm at Toe — Slope stabilization measure. If a slope failure mechanism is causing the toe of the slope to push out, it can sometimes be controlled by adding weight at the base of the slope.

Soil Classification — The solid portion of a soil sample can be classified into either one of these three main groups:

Organic
Fine-grained (non-granular)
Coarse-grained (granular)

Soil Composition — Soil composition is often described with phase relationships. The three possible phases are air, water and solids. A soil sample represents a grouping of many individual solid particles. These solid particles are separated from each other by void spaces that are generally filled with water and/or air. Note that when discussing soils, void spaces are often referred to as pore water and pore air.

Soil Permeability — See Permeability.

Standard Proctor Test — Used to establish this relationship for standard compaction equipment. This test will also identify the moisture content range for the soil that is required to reach this maximum density.

Stress History — The stress history of a soil plays a role in its swell potential. For example, consider a typical excavation for a basement. Remember: the weight of the soil you remove for a basement typically exceeds the weight of the house you construct in its place. While this fact bodes well from a bearing capacity perspective, it can have a negative impact from a swelling perspective. The weight of the soil had provided a confining pressure against the swelling pressures of the expansive clay at the bottom of the foundation excavation. With the reduced confining pressure, there will be a greater potential for swell.

Subgrade — Prepared earth surface upon which the foundation of a structure is built.

Surface Improvements — The goal of a surface improvement repair is to correct an existing unsatisfactory surface water management condition. Some common surface improvements include:

Re-grade and compact the surface.
Extend the roof drains.
Remove the sprinkler systems.
Modify the vegetation types.

Surface Tension — At the outer surface of a water drop, the cohesive forces are much stronger because the molecules to not have any other molecules to bond to on one side. These stronger bonds create the surface tension that holds the molecules together and forms the drop.

Swelling Clays — Clays that can absorb a lot of water.

Test Pit — A test pit is a hole in the ground that is dug out by a backhoe or an excavator. The size of the pit depends on the size of the equipment used and the scope of the investigation, but they are usually no deeper than 5 m.

Till — Till is a type of glacial deposit. It is an unsorted soil that is generally very dense because of the pressure exerted by the glaciers. Tills are generally made up of a combination of particle sizes from boulders to clay.

Time Lag Requirements — See Minimum Time Lag Requirements.

Underpinning — Process by which an existing foundation wall is strenghtened by placing supports underneath it. Several options are available when considering the underpinning of a weakened or failed foundation system, such as:

Extension of the depth of the original foundation.
Bored cast-in-place concrete piles (drilled piles).
Dynamically driven piles.
Micro piles.
Helical piles.

Vibratory Plates — Designed for compaction in confined areas. Vibratory plate attachments are available for most backhoes and excavators. Walk-behind vibratory plates are also available in various sizes. Vibratory plates are comparable to vibratory rollers.

Void Spaces — Includes any phase in a soil that is not solid (i.e. the air and water phases).To be considered a soil, void spaces must exist; otherwise it would just be a solid mass, like a rock.

Weathering — There are two types of weathering:

Physical weathering
Chemical weathering