Question
a) A new building is to be built on a series of spread foundations that will be undrained by saturated clay. Undisturbed soil samples have been obtained from this site and are ready to be tested. Should the laboratory test programme focus on producing values of c' and Ø', or Su
(undrained shear strength)? Explain.
B) A grain silo, which is very heavy structure, was recently built on saturated clay. Because the harvest season was fairly short and intense, the silo was completely loaded fairly quickly (i.e., within a couple of weeks). This is the first time the silo has been loaded. The grain weights about twice as much as the empty silo. The weight of this grain, along with the weight of the silo, has induced both compressive and shears stresses in the soil below.
Suddenly, someone has become concerned that the soil may be about to fail in shear under the weight of the silo and grain. This is a legitimate concern, because such failures have occurred before. Discuss the soil mechanics aspects of this situation and determine whether the risk of failure in the soil is increasing, decreasing, or remain constant with time.