For a saturated normally consolidated clay specimen, the pore pressure coefficient B will be: A) 1.0 B) 0.8 C) 0.2 D) -0.5
Answer (1)
The pore pressure coefficient, commonly denoted as B , is an important concept in geotechnical engineering, specifically in the study of saturated soils. It measures the change in pore water pressure as a response to a change in the applied stress.
For a saturated normally consolidated clay specimen, B can be determined using the following understanding:
Saturated Soils : When a soil is saturated, its voids are completely filled with water. This means any change in stress is initially carried by the water, leading to an immediate change in pore pressure.
Coefficient B : The coefficient B is defined as the ratio of the change in pore water pressure to the change in applied stress:
B = Δ σ Δ u
where Δ u is the change in pore water pressure and Δ σ is the change in applied stress.
Normally Consolidated Clay : A normally consolidated soil is one where the current stress level it is experiencing is the highest it has ever been exposed to. In these conditions, the soil tends to behave predictably under changes in stress.
In the case of a fully saturated normally consolidated clay, the B coefficient is typically 1.0. This is because the applied stress is taken fully by the pore water in the absence of any volume change or drainage.
Therefore, for the given question, the correct answer is:
A) 1.0.
This suggests that any additional load applied to a saturated normally consolidated clay will result in an equal increase in the pore water pressure, indicative of a B value of 1.
