Como funciona uma barragem de rejeitos

Summary

The video discusses the construction and challenges of tailings dams, which are built to store mining waste. Unlike water dams, these structures are made using dry tailings as the foundation and grow continuously as waste is deposited. The construction process involves building a starting dam, or 'dick,' and using the solidified tailings as the base for expansion. A common method used is upstream raising, which is cost-effective but poses significant safety risks due to the low shear strength and susceptibility to liquefaction of the tailings. Efficient water drainage is a critical challenge in managing these dams.

Takeaways

• 😀 Tailings dams are structures built to store waste materials from mining operations, which are different from water dams that use concrete.
• 😀 Tailings dams are always expanding and use dry tailings as a foundation for construction.
• 😀 The construction process begins with the creation of the first embankment (Dick de partida), from which the structure grows through continuous addition.
• 😀 Tailings are the leftover material when the ore is separated from the rock, and are deposited as a slurry (a mix of solids and water).
• 😀 Over time, the tailings dam dries out, and the solid material accumulates at the bottom while the water is drained and treated.
• 😀 The dried tailings are used as a foundation for future embankments, facilitating the dam's expansion.
• 😀 The most commonly used method for constructing tailings dams is the upstream raising method (alteamento a montante), which is cost-effective and easier to transport materials.
• 😀 The construction cost is spread out over the duration of the project, as the dam expands to its full designed capacity.
• 😀 Despite its popularity, the upstream method has critical safety concerns due to the materials used being loose and unsolidified, making the dam vulnerable to shear failure and liquefaction.
• 😀 The dam structure is difficult to manage in terms of drainage, as it is hard to build an efficient system to control the water levels within the dam.

Q & A

What is a tailings dam?

A tailings dam is a structure built for storing mining waste, which is a byproduct of mineral extraction. These dams are different from water dams, as they use materials like dry tailings as a foundation instead of concrete.

How do tailings dams differ from water dams?

Tailings dams use the dry mining waste as a base for construction, while water dams typically use concrete. Additionally, tailings dams are continuously expanded as mining operations grow, unlike water dams.

What is the process of constructing a tailings dam?

The process starts with the construction of an initial embankment (called a Dick de partida). From there, the structure is built up through continuous layers using the tailings, which accumulate at the bottom as the dam dries.

What are tailings, and why are they important for dam construction?

Tailings are the leftover materials after minerals are separated from rocks during mining. They are important for dam construction because they are used as the primary material for the embankments and foundations of the dam.

What happens to the tailings over time in the dam?

As tailings are deposited in the dam, they gradually dry out, and the solid portion accumulates at the bottom, while the water on top is drained and treated.

What is the purpose of the water drained from the tailings dam?

The water drained from the tailings dam is treated before being released. The goal is to manage water levels effectively and prevent contamination from untreated water.

How do tailings dams expand over time?

Tailings dams are expanded by using the solidified tailings at the base to construct higher embankments, a process that is continuous throughout the dam's operational life.

Why is the upstream method of raising the dam embankment commonly used?

The upstream method is widely used because it is more cost-effective and involves simpler logistics for transporting construction materials, mainly using the tailings themselves.

What are the risks associated with the upstream method of constructing a tailings dam?

The main risk of the upstream method is the potential for low shear strength and susceptibility to liquefaction due to the unconsolidated, saturated tailings. This makes it difficult to construct an efficient drainage system for controlling water levels.

Why is it difficult to manage water drainage in tailings dams?

Water drainage is challenging in tailings dams because the tailings are in a saturated, loose state, which complicates the construction of an effective drainage system to control water levels within the dam.