Feasibility design report for a tailings management facility

Liam Erlic, Kai Neilson, Jaden Procter and Gavin Spence

Community Partner: Klohn Crippen Berger
Degree:
- Bachelor of Applied Science
Program:
- Geological Engineering
Campus: Vancouver

Our design solution

This was a three-stage process that included site selection, site characterization and conceptual design of the tailings management facility.

In the first stage, we selected our site within a large region based on various criteria, including topography, geology, proximity to the mine mill, social and environmental considerations, and accessibility.

During the second stage, site characterization, we developed a comprehensive and costed site investigation plan that we shared with our capstone partner, Klohn Crippen Berger. They provided us with data for 14 boreholes that enabled us to understand the stratigraphy of the site and develop a geological model. This stage also included a lab testing program to support site characterization and obtain parameters for analysis.

In stage three, we developed a conceptual design for a tailings management facility that meets national and provincial codes. Design features include eight metre thick till core chimneys above the starter embankments and drainage blankets through the embankments.

Our analysis shows that our proposed structure and geometry meet the required safety factors for static and seismic loading conditions.

Feasibility Design Project Capstone Poster.

Klohn Crippen Berger

The technical challenges we faced

The most significant issue we faced was geological uncertainty. Although we had borehole data in our area of interest, we had to use our engineering judgement to simplify that soil stratigraphy for our model. There is a danger in oversimplification, and we spent considerable time finding the right balance between accuracy and practicality.

One of the most consequential findings from our site characterization was a thick layer of glaciolacustrine clay beneath the foundations of the proposed west embankment. This material is quite weak, and it became one of our largest constraints as we developed the design.

That finding also shaped our approach to slope stability analysis. Within our models, different equations are used to capture how a structure might fail or what forces might cause it to fail, While we have developed experience in our degree using the Mohr-Coulomb model, this approach did not accurately capture the behaviour of the significant clay unit at our site, particularly given the size of our dam.

Instead, we used the SHANSEP failure model, which is better suited to predicting how soft clay responds to the loading imposed by an embankment. We used the results of our lab testing program to define this relationship and to more accurately represent the strength conditions as a function of depth and produce more reliability failure probability estimates.

With this project, each decision is based on the prior one.

So our first decision – where to locate our site – had cascading effects going forward. Similarly, when we were working with our dam models, we were iterating back and forth between slope stability and seepage models as we considered different design approaches to make sure all safety conditions were met.

One of the biggest single decisions was determining the internal structure of the dam to ensure it would perform adequately during an earthquake.

We incorporated a till core — a hard, compacted mix of clay, sand, and gravel — to control how groundwater moves through the embankment. We also added a gravel drainage blanket at the base of the till core, extending to the toe of the dam, to redirect water away from the structure.

How we validated our solution

We validated our design using RocScience software, which allowed us to model slope stability and seepage conditions and confirm that our proposed geometry and materials met the required safety factors. For decisions that relied heavily on engineering judgment, we worked collaboratively to reach consensus before moving forward.

Our partner, Klohn Crippen Berger, also played an important role in validation. They structured the project across three clear stages, which kept us on track, but left the design decisions largely up to us as long as we could justify them. Weekly check-ins gave us a regular opportunity to validate our thinking and approach.

RocScience

What we’re most proud of

The scale and scope of this project was very satisfying. Producing a single, cohesive design deliverable — one that builds directly on every prior stage of research and analysis — gave us a tangible sense of what engineering practice actually looks like. It's also something that's easy to share and explain to people outside the field.

This project also reinforced something that is at the core of geological engineering. Being a geological engineer is fundamentally about managing uncertainty and making your best inference based on the knowledge you have.

It is important to have evidence backing up your hypotheses so that you can defend your decisions. This project also reinforced the importance of bringing in different perspectives – whether from each other, our advisor or our professors – to explore different options and make sure you are considering all relevant factors.