Midterm Examination - Geotechnical Engineering II

A time dependent change of volume of soil due to gradual dissipation of water from the void spaces is

• a.) Compression

• b.) Pore pressure change

• c.) Immediate Settlement

• d.) Primary Settlement

2.) These characteristics of clay soil undergoing consolidation are true.

i. Pore pressure dissipates at a slow rate with increasing loading

ii. Void ratio increases as a result of too much compression

iii. Effective stress improves resulting to higher strength

iv.Volume change of soil is proportionate to the amount of water that dissipates

• a. i,ii, & iii

• b. all of the above

• c.i,iii, & iv

• d.i, ii, & iv

3.) Consolidation theory of Terzaghi is based on the principles that during consolidation

i. Change of the volume of soil is equal to the change of inflow and outflow

ii. Flow is turbulent caused by pore pressure gradient

iii. Rate of change of effective stress results to decrease of pore pressures

iv. Volumetric change in soil is inversely proportional to change of effective stress

• a.) i & iii

• b.) ii & iv

• c.) i & iv

• d.) ii & iii

1. Given the e-log P curve in figure 1, find the following:

a. The maximum past pressure

b.The Compression index of the soil between void ratio

of 0.755 to 0.65.

Problem 5-6. Refer to figure 2. Considering the soil to be a uniform clay layer, Given: P = 150 kN; B = 3 m; L = 3 m; Df = 1.5 m; H = 8 m; e = 0.7; Gs = 2.72; and LL = 42. Assume that the clay is normally consolidated, and the groundwater table is at the foundation level. The moist and saturated unit weight of soil are 15.7 and 19.3 KN/m³ respectively. Increase of effective stress is approximately equal to the pressure at the foundation level.

What is the effective stress a the mid height of clay?

Problem 5-6. Refer to figure 2. Considering the soil to be a uniform clay layer, Given: P = 150 kN; B = 3 m; L = 3 m; Df = 1.5 m; H = 8 m; e = 0.7; Gs = 2.72; and LL = 42. Assume that the clay is normally consolidated, and the groundwater table is at the foundation level. The moist and saturated unit weight of soil are 15.7 and 19.3 KN/m³ respectively. Increase of effective stress is approximately equal to the pressure at the foundation level.

What is the estimated primary consolidation settlement due to the foundation load?

7.)Differential settlement is caused by these situations

i. Properties of soil profile has wide variations

ii. Magnitude of Structural loads differ greatly

iii. Synchronize Time of construction

iv. Uniform foundation sizes

• a. all of the above

• b. i, ii, & iii

• c. ii, iii & iv

• d. i, ii & iv

Problem 8- 9. A 4.57 m saturated clay layer (two-way drainage) subjected to surcharge loading underwent 90% primary consolidation in 180 days.

a.Find the coefficient of consolidation of the clay for the pressure range in ft²/day.

Problem 8- 9. A 4.57 m saturated clay layer (two-way drainage) subjected to surcharge loading underwent 90% primary consolidation in 180 days.

How long in seconds will it take for a 19-mm-thick clay specimen to undergo 65% consolidation in a laboratory test?

Problem 10-11 Refer to figure 2 for the dimensions and condition of soil. Given: P = 1000 KN, Eu = 7,500 KPa.

Estimate the Distortion Settlement in mm using Skempton & Bjerrum. Given: P = 1000 KN, Eu = 7,500 KPa.