Geotechnical studies

This study is used to determine the characteristics and composition of the soil under a proposed or existing building. This test determines if the soils of the site under study are suitable to receive a load (a building in many cases).

This study is used to determine the characteristics of a slope in order to plan the location of a building or a proposed expansion. This test determines the areas at risk of landslides and may include the bearing capacity of the soil.For example, in the Montréal area and its surrounding suburbs, a geotechnical investigation for slope stability can cost approximately $10,000 to $13,000 for “small” residential (single family to approximately triplex), commercial or industrial projects of up to 3 stories.

This study is used to determine the soil characteristics at the location of a proposed septic system (septic tank and leach field which is also called drain field or absorption bed). This plan is used by a contractor to complete the proper installation of a septic system and associated facilities.

It is normally recommended to proceed to a qualitative control of the various stages of the construction in order to ensure the quality and the stability of a projected work. Multitest is able to carry out this aspect such as the inspection of the foundation soils before the concreting of the footings and the control of the backfilling, compacting, concreting, paving, etc.

Other tests are possible such as a short soil bearing capacity study, the control of the soil compaction with a nucleodensimeter, the quality and the resistance of the concrete (for example to check the state of the foundation walls of a building). Please contact us according to your needs.

For “small” buildings (maximum of 600 m^{2, i.e. approximately 6,500 ft2, and three stories), some municipalities may require geotechnical studies; this is often the case for:}

• Building extensions or new constructions located on the waterfront or on a mountainside;
• Known areas with low soil bearing capacity;
• Areas where significant backfill activity has occurred in the past;

Except for the situations mentioned above, for such “small” buildings, it is often at the discretion of the owner, but we strongly recommend it for any construction project to secure your investment and avoid unpleasant surprises.

For larger buildings, a geotechnical study is mandatory according to the National Building Code.

Garantie construction résidentielle (GCR) requires a geotechnical study for certain buildings, notably divided condominiums of more than 5 units. For more details, refer to section 87 of the Regulation respecting the guarantee plan for new residential buildings (chapter B-1.1, r. 8).

The equipment chosen depends on several factors (type of test, type of building, regional soil types, etc.). For example, for soil bearing capacity, when possible, we use an excavator to minimize the cost of the study; however, some files require much more expensive drilling machinery (geotechnical drill rig).

If you provide the equipment required for the surveys (test pits with an excavator or boring with a geotechnical drill rig, as recommended by our engineer), this can reduce the cost of our work. The type of equipment required is established on a case-by-case basis for each file and is confirmed before the contract is signed.

This depends on the type of study. For the bearing capacity of the soil carried out with an excavator by way of test pits (also called trenching or exploration wells), the level of the water table, if it is not encountered during our work, will be estimated by the visual observations of the specialist in the test pits. In the case of a soil bearing capacity study carried out with a geotechnical drill rig, it will be measured with a water well(s) installed in any borehole done. Remember that the groundwater level varies during the year (mainly seasonally) and can therefore change.

It is used primarily by the designers of the proposed building (architects, structural engineers, civil engineers and builders); therefore, it is essential to ensure that a copy of the geotechnical study is forwarded to them as soon as possible, as the results can have a significant impact on aspects such as site preparation, type of foundation or location of a proposed building.

In the case of an existing building, this study is used by the expert conducting the investigation of the identified building problem.

• Identification of geotechnical issues related to the project
• Preparation of the site according to the construction project
• Recommendations regarding the foundation: types of footings, raft foundation (slab serving as foundation), piles, etc.
• Building drainage
• Specific characteristics of commercial, industrial or institutional buildings
• Temporary support structures (e.g. decontamination under a building or near the public domain; construction of a building with several underground levels or near the public domain) or permanent support structures (e.g. construction of a building with underground garages or of a retaining wall on a sloping ground)
• The type of wastewater treatment system (septic installation) if applicable
• The stability of a slope on the property (risk of destabilization)