Numerical Effect of Veil Injection on a Gravity Dam Using Grouting Intensity Number ‘GIN’ Method

Milad Khatib, Melissa Loutfi and Hani Hamdan

This blog post was written by the author of a recent Water Practice & Technology paper and summarises the key features of the research and its implications.

In 2018, I received my PhD in structural and geotechnical engineering, and in 2005, I received my Master's degree from The Beirut Arab University in Lebanon. As a civil engineer, I graduated in 1998. I have learnt a lot about the design and operation of numerical models and technology throughout this period. I have conducted several scale-up experiments in order to strengthen the civil engineering industries. This is my first, but far from final, topic in the IWA water practices and technology. Let us get started to read about “Numerical effect of injection under a gravity dam using grouting method”.

The Quatinah Homos Dam (Syria) is the world's oldest operating dam. It was built between 1319 and 1304 BC during the reign of Egyptian Pharaoh Sethi. Typically, dams are built to stop flows, store water, and generate energy. The Lake Kariba dam (Zambia) has the largest constructed lake by capacity behind such a dam [about 180 billion tons]. The Three Gorges Dam in China, on the other hand, is the world's biggest hydroelectric infrastructure. It has a total capacity of 22,500 megawatts (MW).  Now, and following this historical overview, it becomes clear why the dam is considered to be one of the world's oldest and largest structures.

A gravity dam may encounter two major issues:

- The first is uplift pressure, which may increase the risk of dam reversal.
- The second is groundwater flow, which has the potential to elevate the earth beneath the dam.

If one of these two scenarios occurs, we will be in a disastrous situation.

The breakdown of the Banqiao Reservoir Dam and other dams in Henan Province (China) in 1975 resulted in more deaths than any previous dam catastrophe in history. This catastrophe killed approximately 171,000 individuals and displaced 11 million others.

Furthermore, cracks in dams are typically seen after construction. They are generated mostly because of concrete shrinkage caused by temperature changes. These cracks might form inside in the dam's body or external on the dam's surface. Surface cracks provide a greater risk than inner cracks. These fissures might cause a number of issues with the dam's construction [Silvano et al. (1997), Lariviere et al. (1999)].

In front of all of these situations, several questions can become obsessions:

- How to make the dam stronger?
- How to resist the uplift pressure?
- Can we control the passed flows under the gravity dam?
- Where could exist the best location to fortify the dam?

Many studies have been conducted to answer these problems and provide an appropriate solution. The treatment can be carried out in a variety of ways, one of which is concrete injection beneath the dam. Several studies have demonstrated the effect of the injected concrete in strengthening the dams [Berchten (1985), Turcotte et al. (1994)].

To determine the ideal place for this numerical investigation, 56 alternative locations were considered. The numerical findings reveal that this injection has a significant impact on the uplift pressure force, ground water values, and flows that pass through the gravity dam.

The uplift pressure load obtained was decreased by 83.33%, while the ground water flow under the dam was reduced by 93.95%. The injected veil also obscures the flow arrows as they pass below the gravity dam.

Future research investigations should be conducted on various dam types to determine the effect of injected veil on them.

The article can be read in full over on the Water Practice & Technology web page.

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