At a site, it is planned that a circular grain silo will be constructed at the ground surface. The grain silo will be set on a rigid circular foundation that has a diameter of 6 meters. Assume that the silo will apply a concentric vertical load Q on top of the circular foundation and that the foundation will transfer this load to the top of the silty clay layer as a uniform vertical pressure q. The soil profile at this site is as follows (also shown in attached image): 9-m-deep silty clay layer underlain by bedrock Groundwater table located at a depth of 6 m from the horizontal ground surface, groundwater condition is hydrostatic. Silty clay layer Air-entry value (AEV) = 120 kPa Specific gravity GS = 2.72 Porosity n = 0.42 Average undrained shear strength su = 40 kPa Critical state friction angle Φ'C= 24 degrees (a) How can I compute pore-water pressure, total vertical stress, and effective vertical stress at point P located at a depth of z = 3 m in the silty clay layer along the vertical centreline of the circular foundation prior to the application of the grain silo load Q?        (b) If point P is under at-rest earth pressure conditions and the vertical and horizontal normal stresses at point P are principal stresses, how would I calculate the magnitudes of total and effective horizontal stresses at point P prior to the application of grain silo load Q?

Please help me in answering the following practice questions

At a site, it is planned that a circular grain silo will be constructed at the ground surface. The grain silo will be set on a rigid circular foundation that has a diameter of 6 meters. Assume that the silo will apply a concentric vertical load Q on top of the circular foundation and that the foundation will transfer this load to the top of the silty clay layer as a uniform vertical pressure q. The soil profile at this site is as follows (also shown in attached image):

• 9-m-deep silty clay layer underlain by bedrock
• Groundwater table located at a depth of 6 m from the horizontal ground surface, groundwater condition is hydrostatic.
• Silty clay layer
  • Air-entry value (AEV) = 120 kPa
  • Specific gravity G_S = 2.72
  • Porosity n = 0.42
  • Average undrained shear strength s_u = 40 kPa
  • Critical state friction angle Φ'_C= 24 degrees

(a) How can I compute pore-water pressure, total vertical stress, and effective vertical stress at point P located at a depth of z = 3 m in the silty clay layer along the vertical centreline of the circular foundation prior to the application of the grain silo load Q?       

(b) If point P is under at-rest earth pressure conditions and the vertical and horizontal normal stresses at point P are principal stresses, how would I calculate the magnitudes of total and effective horizontal stresses at point P prior to the application of grain silo load Q?