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How to harness the power of soil: What are the surprising differences between earth-rock dams and rock dams?
With the increasing global demand for water resources management, the design and construction of earth and rock dams has become particularly important. Each of these dam types has its own characteristics, advantages and disadvantages, so it is important to select the appropriate dam type. This article will explore the construction, function and use cases of both types of dams to help you understand how to harness the power of soil in the most effective way.
Earth-rock dam is a large artificial dam, which is usually composed of semi-plastic sediments composed of various soils or rocks. Its core is made of dense, impermeable material that effectively prevents moisture from penetrating.
Types of earth-rock dams
Earth-rock dams are mainly divided into two types: earth dams and rock dams. Earth dams are made of compacted soil, while rock dams use blasting techniques to aggregate rock fragments into a dam. The cross-section of both types of dams usually takes on the shape of a bank or a hill, with the central portion of most dams consisting of impermeable material to prevent water penetration. This makes vast valley areas particularly suitable for the construction of such dams.
The core of an earth dam can be an impermeable material such as clay, concrete or asphalt concrete, making it an option for a wide range of applications.
Characteristics of earth dams
Earth dams, also known as elastic dams, can be constructed from local materials, making them cost-effective in some areas. The construction of such dams can effectively utilize rich soil, making construction more economical. For example, the Tarbela Dam in Pakistan is the largest earthen dam in the world, with a reservoir of 95 square miles (250,000 square kilometers), climbing to a height of 485 feet (148 meters), and using approximately 200 million cubic yards of Filling.
Modern zoned earth dams are equipped with filtration and drainage areas to collect and remove seepage water, protecting downstream integrity.
Characteristics of rock dams
Rock dams are made of tightly packed, granular soil with impermeable areas. Typically, the rock fill contains large amounts of particles and is designed to effectively resist earthquakes, which is especially important in areas with frequent earthquakes. Furthermore, if clay is used in the core of an earthen dam, it is called a composite dam. Despite the many advantages of rock dams, quality controls must be adhered to during construction to avoid liquefaction of the dam with sand and other poor-quality materials.
For example, the New Melonis Dam in California and the Firza Dam in Albania are both rock dams.
Concrete faced rock dam
A concrete faced rock dam (CFRD) is a rock dam with a concrete slab on its upstream face. This design prevents leakage and is not affected by buoyancy pressure. They are fast to construct and less expensive than earth dams, so they have become increasingly popular in recent years based on demand. China's Shuikou Dam is currently the world's tallest CFRD, completed in 2008 and reaching a height of 233 meters (764 feet).
Security considerations
After the dam is built and the reservoir is filled, new weight will be exerted on the valley and the dam, and the water pressure will increase as the water depth increases. This also makes the dam behavior semi-plastic and more flexible under vibration and other external forces. If the water flow exceeds the capacity of the spillway, there will be a risk of dam collapse, and even a small sustained overflow can remove a large amount of dam material within a few hours. This results in very high design standards for spillways, which are usually required to accommodate at least a once-in-100-year flood.
Thus, penetration monitoring becomes a safety factor that must be considered to prevent failure of the confluence.
After considering the characteristics of earth-rock dams and rock dams, it is crucial to choose an appropriate dam design. This not only affects construction and maintenance in a specific geographical environment, but also relates to the effective management of water resources and the safety of local society. Which dam design do you think will be more forward-looking and sustainable in the face of increasingly severe water resources challenges?
