The assessment of the degree of consolidation (U) during embankment construction has engineering and contractual implications. Determining U can be critical to confirm adequate shear strength gain has occurred during hold periods between lift placements to avoid embankment instabilities, or that sufficient settlement has been achieved prior to the end of a preload/surcharge period to maintain conformance with post construction settlement tolerances. Various methods have been suggested by researchers to estimate the degree of primary consolidation achieved during construction, with two commonly implemented approaches being: a comparison of peak pore water pressure measurements to the measurements at the time of the assessment, and an observational method utilizing available settlement data (Asaoka, 1978). For both approaches, uncertainty exists during construction as to the accuracy of the prediction of degree of consolidation; therefore, it is often necessary to supplement the predictions with engineering judgement when making decisions that could affect construction costs and schedule. Three Ministry of Transportation, Ontario (MTO) highway embankment sites in Northern Ontario are examined, where foundation monitoring data was collected throughout construction and where the preload or surcharge period has been completed and the end of primary consolidation settlement has been achieved. Installation of wick drains and restrictions on staging were carried out during construction at these sites to mitigate stability and settlement concerns. The range of error in estimating the degree of primary consolidation at various points in time during construction are explored, utilizing pore water pressure data, settlement data in conjunction with the Asaoka method, as well as ‘curve-fitting’ to attempt to match model predictions to monitoring data. Best practices for reducing the uncertainty of the predictions are presented with the intent to allow for improved decision making on future construction projects that involve wick drains, staging and preloading or surcharging.

The paper summarizes the design of stabilization measure which were constructed in the portion of the CN Sub which lies between the towns of Dundas and Copetown, Ontario. Construction of the initial single rail track took place in the early 1850’s, the track was doubled in the 1890’s. The affected section of track rises up from the base to the top of Hamilton Mountain (Niagara Escarpment), it features cuts, side slope fills and embankments. Railway construction was carried out without benefit of sophisticated construction equipment, fills were not subject to dense compaction. Cuts were made into hillsides to construct a level platform to support the track with fill being placed on the downhill side to add platform width. Design of the various sections of earthworks associated with track construction was based on experience rather than rational design methods. Over the past few decades some sections of rail track have experienced ground movements on the uphill side of the track in the steepened cut slopes, with a potential for slide debris in invade the track. In other sections, track supported by fill soils and track lying above native slopes on the downhill side have experienced downslope movements as a result of much increased axle loads and much increased length of trains compared to the initial train loads.

The paper reviews the design of stabilization measure at five sections of track. The stabilization designs feature: gravity wall; gravity berm; soil nailing of entire slope and soil nailing of the top portion of slope. The rationale for design method selection is discussed for each site in conjunction with site constraints such as urgency, property limits, minimal effect on rail operations, site access restrictions and cost.

The supply of low-cost, quality aggregate in Ontario is decreasing. To mitigate this trend for granular (sub)base construction, a possible solution is to use quarried aggregate that does not meet current physical property requirements, but can be shown to maintain proper structural and hydraulic performance of the engineered layers

Two important factors for the design of pavement structures are the resilient modulus (Mr ) and hydraulic conductivity of the granular (sub)base. The resilient modulus depends on aggregate type and particle shape, as well as grading and fines content, moisture content, density, stress level, stress history and the number of load cycles. The permeability is influenced by the gradation of the aggregates. The relation between the mechanical properties and drainage is important as the stress-strain-load cycle behaviour is sensitive to the degree of saturation and ability of the granular material to dissipate any generation of excess pore pressure. This study addresses the effect of fines on the mechanical properties of four different Granular A crushed rock materials. The objective of this paper is to report on the experimental findings regarding the influence of fines on the resilient modulus and hydraulic conductivity.

The Mr, which tended to decrease with an increase in fines content, was found not to be sensitive to the type of fines for the materials. Furthermore, as the amount of paste increased (percent water plus percent passing the 75-micron sieve) during specimen fabrication, the Mr for a given confinement decreased. Results from permeability tests confirmed that with zero fines present, the hydraulic conductivity was much larger than that when fines are present. The permeability did not change much for specimens in which natural fines were replaced by substitute fines. An important observation with regards to the migration of fines is that secondary effects cannot be captured by Darcy’s law.

As a part of upgrades to provide faster, more frequent and more convenient transit service across the Greater Toronto and Hamilton Area (GTHA), electrification of the core segments of the GO Rail network is part of the GO Expansion program. GO Rail Expansion will provide significant new travel choices for GTHA residents, including: electrified service on Metrolinx owned rail corridors, with trains running every 15 minutes in core areas of the network and two-way all-day service. As a part of this expansion program construction work is underway on the Kitchener GO Corridor. Due to limited height clearance in the existing tunnel rail on Kitchener Corridor under Highway 401 near Highway 409, a new twin tunnel is being constructed next to the existing tunnel under Highway 401 crossing 21 vehicular lanes.

A 26mx 10mx 9.8m deep strutted sheet pile shaft was designed to facilitate the installation of a tunnel pre-support pipe canopy by auger boring. The tunnel pre-support was required by the tunnel designer as part of the sequential excavation method (SEM) to provide ground support and minimize the settlements to the highway. The shaft was located in the median space between the Highway 409 eastbound ramp and bridge abutment and Highway 401 eastbound express lanes and abuts the existing rail tunnel along one side. The unbalanced loading on the shaft was considered due to the grade difference between the Highway 409 ramp and Highway 401 eastbound lanes. The temporary shaft structure was also used to control the movements of the adjacent rail tunnel and bridge abutment wingwall structures. This paper will provide a comprehensive overview of the challenges encountered during detailed design, analysis techniques adopted and a summary of the settlement profile observed on the ground surface around the shaft.

Geotechnical assets play a crucial role in the function of transportation corridors. Geotechnical assets such as soil and rock slopes, retaining walls, embankments, and subgrade soils serve to support the provincial highway infrastructure, but can also pose potential threats to the transportation system as a result of deteriorating condition, escalating maintenance costs or catastrophic failures. Asset Management is a strategic and systematic process of operating, maintaining, upgrading, and expanding physical assets effectively throughout their life cycle. It focuses on economic analysis and engineering practices for resource allocation and utilization, with the objective of better decision making based upon quality information and well-defined objectives. Public agencies are beginning to recognize the potential benefits of taking a proactive, systematic approach to the management of geotechnical assets, and geo-professionals are developing tools for the inventory, condition assessment, life-cycle cost prediction and risk assessment of geotechnical assets.

Alberta Transportation is responsible for managing approximately 500 identified geohazard sites through the province. This paper will describe Alberta Transportation’s current Geohazard Risk Management Program (GRMP), and the vision for transforming this program into a formalized Geotechnical Asset Management (GAM) system. Part of the proposed transformation will be to develop and implement a condition rating system that is applicable to a range of geotechnical asset types (slopes, retaining walls, embankments and subgrades), with simplified deterioration models for projecting asset performance over time. The goals of Geotechnical Asset Management are to enhance the Department’s ability to monitor the condition and deterioration of our geotechnical asset inventory, forecast future funding requirements to achieve desired levels of service and risk reduction, and facilitate evidence-based decision making that considers the full life cycle costs and benefits of our geotechnical assets.

Deep geological repositories are being designed to manage spent nuclear fuel of past and future reactors for up to 1 million years across the world. The geosphere surrounding a repository should be structurally stable against geological perturbations, such as earthquakes. Previous studies have evaluated earthquake effects on the repository showing that, there is a measured change in excavation damage zone due to a low probability earthquake event. However, a quantitative study has yet to be performed considering extreme events. In this study, a two-dimensional model was developed in RS2, from Rocscience, a finite element package and compared to a previous repository seismic model. The model utilized a Voronoi joint network around the repository to represent a crystalline rock formation (host rock) and allow for excavation induced damage to evolve during construction. The host rock as well as the engineered barrier system were then subjected to glacial induced stress and earthquake loading. This model was then used to perform a statistical study using analysis of variance (ANOVA) to quantify the earthquake effects. The ANOVA analysis (significance level of 0.05) examined normal and shear stresses and displacements along the Voronoi joints after earthquake events of different seismic coefficients (model coefficients used to represent the peak ground acceleration as a fraction of the acceleration due to gravity), relative to the model with no earthquake events and no glacial loading. Glacial loading caused additional damage in the repository excavation damage zone and had statistically significant effect on joint normal stress. The seismic coefficients had no statistically significant effect on the joint parameters, although only the final state after the earthquake loading was investigated. Future research will examine the dynamic loading response during an earthquake.