Final answer:
The minimum depth of excavation for curbs below the subgrade can vary depending on factors like design requirements and soil type.
Step-by-step explanation:
The minimum depth of excavation for curbs below the subgrade can vary depending on different factors, such as the design requirements and the type of soil.
An older rule of thumb suggested a depth of 7-8 times the diameter of the curb. For example, if the curb has a diameter of 1 meter, the minimum excavation depth would be 7-8 meters. However, newer research suggests excavating up to 15 times the diameter for better stability.
It's important to consider the specific project requirements and consult professional engineers for precise recommendations.