A long highway embankment, having the cross-section shown in Figure 2, is to be rapidly constructed at a site. The unit weight of the embankment material is 18.85 kN/m³. The soil profile at the site consists of a 3 m thick layer of coarse sand underlain by an 8 m thick layer of overconsolidated soft silty clay. 2.5 4.0m 4 4.0 m Coarse sand 2.0 m piezometer 2.0 m Soft silty clay 3.0 m 2.5 10.0 m Impermeable layer 3.0 m 8.0 m Figure 2: Cross-section of a long embankment instrumented with three piezometers. From the results of laboratory tests, the saturated unit weight of the coarse sand is 16.5 kN/m³. Based on the results of tests performed on a sample from the mid-depth of the soft silty clay layer, the saturated unit weight of the coarse sand is 17.0 kN/m³, the initial void ratio (eo) is equal to 2.30, the swell/re-compression index (Cr) is equal to 0.055, the compression index (C) is equal to 0.245, and the coefficient of consolidation (c) is 20 m²/yr. Finally, it is estimated that the overconsolidation ratio (OCR) is 2.50. a) Compute the vertical effective stress at the mid-depth of the soft silty clay layer prior to the placement of the embankment. b) Estimate the preconsolidation stress (σp) for a sample from the mid-depth of the soft silty clay layer. c) Compute the increment in vertical total stress (Aσ,) at the mid-depth of the soft silty clay layer along the centerline of the embankment due to its construction. Consult Section 7.8 in the textbook (also see Figure 7.13) or use the equations presented in lecture. d) Compute the ultimate primary consolidation settlement (sc) of the mid-depth of the silty clay layer along the centerline of the embankment. e) What is the time required to reach 50% of the ultimate primary consolidation settlement. f) Compute the amount of primary consolidation settlement after 120 days. g) After one year, what would be the excess pore pressure measured by the three electric piezometers that were installed in the soft silty clay layer?

Refer to Figure P3.3. Use Eqs. (3.10) and (3.11) to determine the variation of OCR and preconsolidation pressure c. FIGURE P3.3

Redo Problem 6.12 using Figure 6.15. 6.12 Refer to Problem 6.1. Using Eqs. (6.3) and (6.29), estimate the average stress increase (av) below the center of the loaded area between depths of 3 m and 6 m. 6.1 A flexible circular area is subjected to a uniformly distributed load of 150 kN/m2 (Figure 6.2). The diameter of the load area is 2 m. Determine the stress increase in a soil mass at points located 3 m below the loaded area at r = 0, 0.4 m, 0.8 m, and 1 m. Use Boussinesqs solution. Figure 6.2 Increase in pressure under a uniformly loaded flexible circular area

Refer to the flexible loaded rectangular area shown in Figure 10.47. Using Eq. (10.36), determine the vertical stress increase below the center of the loaded area at depths z = 3, 6, 9, 12, and 15 m. Figure 10.47