Thirty-Ninth Canadian Geotechnical Colloquium: Unsaturated soil mechanics — bridging the gap between research and practice

Abstract

12The majority of geoengineering applications occur in the unsaturated zone, which is in the near-surface 13 region forming the connection between meteorological phenomena above and saturated ground below. 14 The key characteristic of the unsaturated zone is that water is in tension or, put another way, pore water 15 pressure is negative. Moisture content, as well as most material properties, vary spatially and temporally 16 in the unsaturated zone and coupled processes are common. In geoengineering applications in the vadose 17 zone, unsaturated soils may be present during part or all of its design life. The question is how or when 18 to consider the unsaturated soils principles in an analysis or design. Although most geoengineering 19 applications have an unsaturated component, use of unsaturated soil mechanics in practice lingers 20 behind the prolific number of publications due uncertain benefit of accounting for unsaturated effects, 21 complexity, and conservativeness among other reasons. The focus of this colloquium is to continue 22 bridging the gap by illustrating unsaturated soils principles using application-driven examples in the 23 areas of capillarity as well as flow, strength, and deformation phenomena. As principles of unsaturated 24 soils become more understood and demand increases for incorporating climate change effects in design, 25 use of unsaturated soils principles in practice will continue to increase. 26

Quantifying the contribution of matric suction on changes in stability and displacement rate of a translational landslide in glaciolacustrine clay

“…However, advancements have resulted in more efficient and reliable monitoring methods due to improved manufacturing, and increased sensitivity in sensors for both in-situ water content and matric water potential (suction). The contribution of matric suction is a factor for stability in slopes with extensive vadose zones and should be considered in many geotechnical applications (Leroueil 1999;Blight 2003;Siemens 2018).…”

An Investigation of Rainfall-Induced Landslides From the Pre-Failure Stage to the Post-Failure Stage Using the Material Point Method

“…In the treatments that take place in the initial condition, the initial state is assumed to be satisfied with geostatic and hydrostatic conditions, and so the initial velocities of each phase can be set as zero (Bandara et al, 2016;Siemens, 2018). The initial stress distribution is set using a K 0 procedure (Bandara et al, 2016).…”

“…Above the phreatic surface, the suction is generated hydrostatic until it reaches a prescribed value. Below the phreatic surface, the pore water pressure is generated according to the depth of the groundwater (Siemens, 2018).…”

An experimental investigation on the water retention behaviour of a silty soil for the computation of the lateral earth thrust on a retaining wall

“…Clayey or silty soils compacted on the dry side of the compaction curve display a bimodal pore structure while soils compacted on the wet side of the compaction curve or reconstituted slurries present unimodal pore structures [1].…”

“…Retaining structures often retain soils that are in partially saturated conditions and, these conditions may be present during part or all of their design life [1]. Regardless, their performance is influenced by the environmental actions.…”