CSA PLUS 4011.1:19

Preface:

This is the first edition of CSA PLUS 4011.1, Technical Guide: Design and construction considerations for foundations in permafrost regions.

CSA Group received funding for the development of this Guideline from the Standards Council of Canada, as part of the Northern Infrastructure Standardization Initiative (NISI) with input from the Northern Advisory Committee (NAC).

Introduction:

1.1 Background
In 2010, CSA Group published CSA PLUS 4011, Technical Guide: Infrastructure in permafrost: A guideline for climate change adaptation. The intent of that document was to provide stakeholders with information on the potential impacts of climate change on infrastructure in Canada's permafrost regions. It is recognized that climate change might impact permafrost terrain more dramatically than terrain in temperate regions. Those involved in the development, design, procurement, construction, and operations of infrastructure in permafrost terrain would benefit from current knowledge on the potential impacts of a changing climate on those activities.

In 2019, CSA Group published an update to the 2010 edition of CSA PLUS 4011. In making revisions and updates to the 2019 document, it was recognized that stakeholders could gain additional benefit if a supplemental document was developed that provided current information on the issues related to the design and construction of foundations in permafrost regions. It is the foundation of buildings that will be most dramatically impacted by rapid and high-magnitude warming of air temperatures.

1.2 Purpose
While both the 2010 and 2019 versions of CSA PLUS 4011 provide discussions on foundations in permafrost, this Guideline is intended to provide more detailed technical information on the attributes of the various foundation systems, selection criteria, ground conditions, and related issues.

This Guideline is a companion document to CSA PLUS 4011. The CSA Subcommittee made a deliberate decision not to include equations, formulas, and design guidelines in this document. It is not a design manual — it is informative. This Guideline is intended to assist developers, designers, the general public, and other stakeholders understand the permafrost terrain of Canada, as well as the general selection process and choices for permafrost foundations and their limitations.

1.3 Document structure
This Guideline is laid out as follows.

• Clause 2 introduces and describes the permafrost of Canada. For this Guideline, permafrost is limited to "northern" permafrost. Topics covered include the distribution of permafrost in Canada, ground temperatures, ice content, salinity, terrain sensitivity, surface hydrology, and the effects of a changing climate on the performance of building foundation.
• Clause 3 describes some important considerations for foundation design in permafrost terrain. Topics include ground temperature and its effect on soil strength, creep, effects of pore water salinity, effects of surface disturbance on the thermal regime of the ground, the need for geotechnical investigations, and the impacts of site preparation. A flowchart to assist in foundation selection is provided, followed by a discussion of foundation and design issues, including thaw settlement, frost heave, and frost jacking. A developing trend in foundation design in permafrost called "adaptive design" is discussed, which involves incorporating low-cost strategies in a foundation design that can be later used to provide mitigation for a future performance issue.
• Clause 4 addresses logistics and northern-specific constraints related to foundation design and construction. Given the remoteness of most northern communities, planning and execution of construction projects is of major importance.
• Clauses 5 and 6 address the attributes of permafrost foundation systems (i.e., shallow and deep foundations). Descriptions of the various foundation systems are provided, illustrated by photographs and figures.
• Clause 7 describes the role and uses of insulation materials in foundation design and construction. The science of insulation continues to evolve, and new materials have the opportunity to improve the performance of foundations on permafrost.
• Clause 8 provides a discussion on the role, merits, and tasks associated with operational monitoring and inspection.
• Annex A is a glossary of concepts and terms use in this Guideline. Annex B lists bibliographic information for the documents referenced in this Guideline.