What is the effect of proper drainage on bearing capacity around foundations?

What is the effect of proper drainage on bearing capacity around foundations?

• A. Proper drainage reduces hydrostatic pressure and settlement risks, supporting bearing capacity.
• B. Drainage has no impact on bearing capacity.
• C. Drainage only affects surface appearance.
• D. Drainage increases foundation weight.

Answer: (A)

The key idea is that drainage affects bearing capacity through pore-water pressure and effective stress. When drainage around a foundation is good, water in the soil can escape or be removed, so pore-water pressure stays low as load is applied. That keeps the effective stress high, which increases the soil’s ability to carry the imposed load and reduces how much the foundation will settle. If drainage is poor, pore-water pressure can rise under loading, which lowers effective stress and weakens the soil’s capacity to support the foundation. That can lead to greater settlement and potential differential movement. So proper drainage directly supports bearing capacity by keeping the soil strength higher and settlement more controlled, not by changing the weight of the foundation or by affecting anything superficial like surface appearance.

The key idea is that drainage affects bearing capacity through pore-water pressure and effective stress. When drainage around a foundation is good, water in the soil can escape or be removed, so pore-water pressure stays low as load is applied. That keeps the effective stress high, which increases the soil’s ability to carry the imposed load and reduces how much the foundation will settle.

If drainage is poor, pore-water pressure can rise under loading, which lowers effective stress and weakens the soil’s capacity to support the foundation. That can lead to greater settlement and potential differential movement. So proper drainage directly supports bearing capacity by keeping the soil strength higher and settlement more controlled, not by changing the weight of the foundation or by affecting anything superficial like surface appearance.