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Which weir is also called Dry Stone Slope Weir?
Masonry weir
Gravity weir
Rock-fill weir
Concrete weir
Rock-fill weir
A Rock-fill weir, often termed as a 'Dry Stone Slope Weir', is a diversion structure constructed primarily by dumping rocks or boulders into a riverbed without the use of binding mortar. These weirs rely on their self-weight and the inter-locking action of the stone materials to resist the hydraulic forces of the flowing water.
A Rock-fill weir, often termed as a 'Dry Stone Slope Weir', is a diversion structure constructed primarily by dumping rocks or boulders into a riverbed without the use of binding mortar. These weirs rely on their self-weight and the inter-locking action of the stone materials to resist the hydraulic forces of the flowing water.
FsтАЛ=╬гP╬гWтЛЕtan╧ХтАЛ тАФ Factor of safety against sliding, where ╬гW is weight and ╬гP is horizontal pressure.
The stability of a rock-fill weir is derived from the gravity effect of its massive bulk and the friction between the large stones. Because it is a pervious structure, water often percolates through the body, which requires the provision of a downstream filter or apron to prevent internal erosion (piping) of the foundation material.
Constructed without mortar, making the structure flexible and able to accommodate minor settlements.
Specifically suitable for rivers with high sediment transport and rocky beds.
Requires significant cross-sectional volume compared to masonry or concrete weirs due to lower density.
Prone to heavy seepage, often necessitating an upstream clay blanket to reduce water loss.
Economy in materials, especially in areas where local stones are abundant.
Flexibility allows the structure to settle without cracking.
Simple construction technique requiring minimal skilled labor.
High permeability leading to significant seepage losses.
High maintenance cost due to frequent displacement of stones during flood events.
Susceptible to piping failure if filter layers are not properly designed.
Small irrigation diversion works in hilly or mountainous regions.
Temporary diversion structures for river training or construction sites.
Unlike masonry or concrete weirs (Options A, B, and D), which are rigid and impermeable, rock-fill weirs act as semi-permeable gravity structures.
The term 'dry stone' refers to the absence of binding mortar in the construction process.
C is correct тАФ A rock-fill weir is also known as a dry stone slope weir because it is built by piling rocks without mortar, relying on gravity and friction for stability.
When calculating the stability of rock-fill structures, always consider the submerged unit weight (gammasubтАЛ) of the material to assess the effective resistance against sliding and overturning.