For the upstream face of an earthen dam, the most adverse condition for stability of slope is A. sudden drawdown B. steady seepage C. during construction D. sloughing of slope

The correct answer is A. sudden drawdown.

Sudden drawdown is the most adverse condition for stability of slope because it causes a decrease in effective stress and an increase in pore water pressure. This can lead to slope instability and failure.

Steady seepage is a less adverse condition because it does not cause a sudden change in effective stress or pore water pressure. However, it can still lead to slope instability if it is not

During construction, the slope is often in a state of instability because it is not yet fully compacted. This can be a problem if the construction process is not properly managed.

Sloughing of slope is a type of slope failure that can occur when the soil on the slope becomes saturated and loses its strength. This can be a problem if the slope is not properly protected from erosion.

In conclusion, sudden drawdown is the most adverse condition for stability of slope because it causes a decrease in effective stress and an increase in pore water pressure. This can lead to slope instability and failure.