The Observational Method in TSF Construction: Why It Matters

Modern tailings storage facilities (TSFs) operate in environments where ground conditions are variable, water pressures shift, and construction stages evolve over time. In such dynamic settings, relying solely on pre-construction assumptions is not enough.

This is where the Observational Method becomes one of the most powerful tools in tailings dam engineering, enabling engineers to adapt, respond, and refine designs based on actual field behaviour rather than theoretical predictions alone.

1. What Is the Observational Method?

The Observational Method is a systematic construction approach where:

• Engineers predict a range of possible ground behaviours.

• Instrumentation and monitoring systems are installed to track real-time performance.

• Construction is adjusted as needed based on actual field responses.

Rather than waiting for issues to surface, the method creates a proactive framework for continuous assessment and improvement.

It is especially valuable in TSF construction, where soil conditions, drainage behaviour, and tailings deposition can evolve over time.

2. Why It Matters in Tailings Facility Construction

Tailings dams are not traditional structures with a fixed shape or load. They grow, sometimes for decades, as new lifts are constructed and material properties change.

The Observational Method helps address key uncertainties such as:

• Unexpected settlement or deformation of the foundation.

• Increasing pore pressure during or after deposition.

• Changes in tailings strength due to moisture fluctuations.

• Slope behaviour as embankments rise.

• Drainage performance under varying climatic conditions.

By tracking how the dam responds, engineers can refine designs and strengthen embankments before risks escalate.

3. Key Components of the Observational Method

To work effectively, the method relies on three pillars:

A. Predictive Models

Engineers outline potential behaviour scenarios, from expected performance to worst-case conditions.

B. Instrumentation & Monitoring

Instrumentation provides real-time data on:

• Pore water pressure

• Settlement and movement

• Seepage rates

• Stress changes

• Water levels

Examples include piezometers, inclinometers, settlement plates, and vibrating wire sensors.

C. Pre-Defined Response Actions

Before construction starts, the project team defines the actions to be taken if monitoring data deviates from predictions, including design modifications, drainage improvements, reinforcement, or operational limits.

This structured approach reduces uncertainty and enhances safety.

4. Benefits for TSF Safety and Performance

The Observational Method improves outcomes through:

• Early detection of abnormal behaviour

• Timely corrections during construction

• Reduced risk of failure

• Optimized material use and lower construction costs

• Better alignment with GISTM and international best practices

In regions where soil variability, rainfall intensity, and groundwater behaviour are difficult to predict, such as many parts of Africa, this approach significantly strengthens TSF resilience.

5. The AES Approach

At African Engineering Services (AES), we integrate the Observational Method into all major TSF projects through:

• Advanced geotechnical investigation

• Real-time instrumentation and monitoring

• Data interpretation supported by regional expertise

• Adaptive construction supervision

• Continuous engagement with operators and stakeholders

Our method ensures that TSFs are not only engineered correctly, but also constructed and monitored under the highest safety standards.

Because every lift, every layer, and every data point contributes to long-term stability.