Dams & Reservoirs

Question 1

What Characteristics Should the Foundations of a Dam Have?

Answer 1

• Strong and competent with a high load baring strength.
• Ideally the rock should be a crystalline igneous or metamorphic rock or cemented or impermeable sedimentary rock.
• Clay, mudstone and shale are weak, incompetent rocks with a low load baring strength, so are generally unsuitable.

Question 2

Why is the Attitude of Strata Important to Consider?

Answer 2

• Beds that are horizontal or dip upstream provide stable foundations.
• Beds dipping downstream are unstable. There is the potential for leakage and slippage along the bedding planes that may lead to the collapse of the dam.

Question 3

Why are Geological Structures Important to Consider?

Answer 3

• Anticlines make unstable foundations because slippage can occur along bedding planes on the fold limbs.
• Faults are zones of permeability and weakness and may have different rock types on either side.
• Synclines are stable but water can bypass the dam through permeable beds.