Peatlands cover 113.6 million hectares in Canada, or 13% of the country’s surface area and are present in all provinces. Due to the existence of the fibres, the application of conventional isotropic elastic soil theory is not appropriate for analysing the undrained behaviour of this material. Therefore, a better approach for understanding the mechanical and engineering properties of peat is required. In this research, results of consolidated undrained and drained triaxial compression and extension tests on undisturbed and remoulded peat specimens were used to fully quantified undrained tensile strength, and define an appropriated failure criterion for peat. Moreover, the impact of fibre orientation on the pore water pressure response, elastic stiffness, and undrained shear strength were further examined and the Poisson’s ratio under drained compression and extension conditions was studied with the aid of characterizing the anisotropic properties of peat. The paper will present the results of this laboratory testing with a specific focus on the variation of tensile strength, and stiffness with the orientation of the principal stresses.
Keyword: peat, triaxial compression test, extension test, direct shear test, undrained tensile strength, pore water pressure response, elastic stiffness, Poisson’s ratio.

In 2014, the Canadian government awarded a $4.3 Billion Design-Build contract to the Joint Venture (JV) team Signature on the Saint Lawrence (led by SNC-Lavalin) for the design and construction of one of the largest infrastructure projects in North America, the new Champlain Bridge in Montreal. In addition to the new 3.5 km main bridge, the overall project involved the construction of tens of smaller bridges and over 20 retaining walls along the bridge approaches. The complexity of the project posed unique geotechnical challenges on many levels.
The west approach alignment was to be constructed over an old landfill where the subsurface investigation indicated up to 9 m of waste solid. A 7-m temporary embankment test was constructed on the existing fill, and 32 settlement platforms were installed during the design phase to monitor the settlement. The “consolidation” and strength parameters were then back calculated and used in the roadway embankment design. Moreover, part of the new highway alignment was to be construed over an existing 11x5 m COS collector with unknown structural condition. The owner requirement was to apply no additional load on the collector. Numerical analysis of the stress-strain conditions along with the use of lightweight fill was performed. Furthermore, the presence of a thick liquefiable silty soil deposit led the geotechnical team to design the foundation system to withstand seismic loading induced during a 2% in 50-year return period. Also, although most structures were constructed on drilled shafts, driven piles to refusal were also used. The nominal resistance was carefully assessed with thorough dynamic testing program due to relaxation phenomenon occurring on the shale formation.
This paper addresses the issues encountered and concerns raised during the geotechnical design and how these were addressed and resolved. Design and construction procedures, challenges and solutions are discussed in detail.

A light rail transit infrastructure project proposed in Toronto requires construction of deep retaining walls with excavations into approximately 18m of glacial till, consisting of silty clay and sandy silts. Due to the proximity of the proposed deep excavation to several sensitive existing infrastructures, an advanced finite element constitutive soil model, the PLAXIS Hardening Soil with Small Strain (HSs) model was used to perform non-linear ground movement analysis, and to assess the soil-structural interaction due to hysteresis effects under seismic condition. The HSs model is a rate-independent, hyperbolic, effective stress constitutive model.

The available laboratory tests comprised of isotropically consolidated, undrained triaxial compression (CIUC), and 1-D incrementally loaded oedometer tests. Field testing included geophysical acoustic velocity measurements, cone penetration testing (CPT), field vane, and TEXAM Pressuremeter.

The calibration of the model, based on a laboratory tests and small strain stiffness from geophysics, is demonstrated in this paper. The model was validated comparing the numerical predictions of shear strength, and stiffness with the values obtained from in-situ field testing. Selected parameters were compared with the local empirical correlations from typical index testing obtained by conventional geotechnical investigation. Results of ground movements behind the proposed excavation from the finite element model were then compared with the empirical normalized ground movements from local studies for deep excavations.

This study summarizes the range of HSs model parameters that are applicable for the project in the local Toronto geology. Through validation from field testing and comparisons with local empirical correlations with data from other local projects, it is shown that the model can predict the in-situ strength and stiffness of real soils with some certainty. Results of the finite element model show that the ground movements are comparable with local empirical experience.

Shear strength parameters of moist soil is often required for the design of underground pipelines since the soil around the pipelines is generally moist. The strength parameters for the sand are usually determined from laboratory tests conducted on dry or saturated sand samples. However, the difference between the the behavior of moist sand and dry or saturated sands are well-recognized. Researcher employed different methods through modification of conventional direct shear or triaxial test apparatus for testing moist sands. This approach is usually complicated and time-consuming, yet not flawless. In the present study, conventional triaxial test apparatus is used to assess the shear strength parameters of a moist sand. The tests are conducted using a local sand with varying moisture contents. Total stress analysis is adopted to interpret the test results for determining the strength parameters. Consolidated undrained test is also conducted on saturated sand for comparison of the test results with the moist sands. Test results are also compared with the results of moist sand available in the literature.

Several Standard Penetration Tests (SPT), Cone Penetration Tests (CPT) and Pressuremeter Tests (PMT) were recently carried out along the Lakeshore West Corridor in the Greater Toronto Area. These tests were carried out in sets spaced at 3 to 5 m so that the same stratum was tested but also to avoid interference between each test. This paper will present a direct comparison of the SPT, CPT and PMT tests for different types of soil with same gradation and plasticity. The results will be used to evaluate the effect of mean grain size, fines content and plasticity which are known to affect the relations of the SPT, CPT and PMT values. The test data will be compared with available correlations in literatures, including CPT to SPT ratio versus mean particle size plot presented in Canadian Foundation Engineering Manual. Finally, improved correlation for the test data will be proposed and its difference with existing correlations in literature will be discussed.

This paper will describe empirical assessments carried out to verify ultimate pile capacity on a wharf project in Western Canada. The wharf is in a river delta at the head of a major fjord system where the shallow stratigraphy typically consisted of interbedded gravely sands, sands, silty sands, silts, and clays.

On typical wharf projects involving driven tubular steel piles, capacity assessments are made based on combinations of static load and high strain dynamic load testing conducted only on selected piles. Remaining piles are evaluated using observations made during driving, such as hammer energy and penetration per blow.

Assessment of driven pile capacity during construction is complicated by time-related factors that arise primarily due to pore pressures developed during pile driving and their subsequent dissipation over time. The phenomenon of pile set-up typically results in final capacities being at a minimum shortly after driving and then increasing over time. Ideally, all pile capacity testing would be conducted a long time after initial driving, however construction schedule pressures dictate that piles must be tested as early as possible after driving.

On the subject project, pile set-up was significant and took relatively long periods of time. The paper describes the pile
assessments that were made including correlating pile capacity test results to pile driving records, long-term set-up factors and the relationship between pile set-up and time since driving.

Pile capacity was assessed by normalizing hammer energy and pile set per blow and correlating to capacity at the time of testing or driving using an initial data set of static load test and high strain dynamic test results. A site-specific correlation between set-up and time was established and used to predict the long-term pile capacity. Relatively high set-up factors were established, considering the predominantly granular nature of the soils at the site.