Consolidated-drained triaxial tests 0z (kN/m²) (Ao d; (kN/m²) 150 527 275 965 350 1225 450 1580 510 1800 Figure 12.58 Task 2: Loading the specimen through a specified stress path A soil specimen is loaded along the stress path O (0, 0), P (250, 0), and A (675, 1000) under drained conditions to reach point A close to the failure line estab- lished in Task 1 (Figure 12.58). Determine the combinations of confining pres- sure and deviator stresses applied to the triaxial specimen at 0, P, and A in order to follow the stress path O-P-A. © Cengage Leaming 2014 Failure line Stress path O-P-A © Cengage Leaming 2014

A soil element beneath a pave ment experiences principal stress rotations when the wheel load, W, passes over it and moves away, as shown in Figure 10.51. In this case, the wheel load has passed over points A and B and is now over point C. The general state of stress at these points is similar to the one shown by a stress block at point D. The phenomenon of principal stress rotation influences the permanent deformation behavior of the pavement layers. Investigate how the magnitude and the orientations of the principal stresses vary with distance from the point of application of the wheel load. Consider the case shown in Figure 10.51. An unpaved aggregate road with a thickness of 610 mm and unit weight of 19.4 kN/m3 is placed over a soil subgrade. A typical single-axle wheel load, W = 40 kN, is applied uniformly over a circular contact area with a radius of R = 150 mm (tire pressure of 565 kN/m2). The horizontal and shear stresses at each point are calculated from a linear elastic finite element analysis for a two-layer pavement and are presented in the following table. a. Use Eq. (10.28) to calculate the vertical stress increases at soil elements A, B, and C that are located at radial distances 0.457,0.267, and 0 m, respectively, from the center of the load. Determine the total vertical stress (y) due to wheel load, the overburden pressure at each point, and enter these values in the table. b. Use the pole method to determine the maximum and minimum principal stresses (1 and 3) for elements A, B, and C. Also determine the orientation (s) of the principal stress with respect to the vertical. Enter these values in the table. c. Plot the variations of 1 and s, with normalized radial distance, r/R, from the center of loading.

Refer to Figure 8.13. The magnitude of the line load q is 45 kN/m. Calculate and plot the variation of the vertical stress increase, between the limits of x = 10 m and x = +10 m, given z = 4 m. FIG. 8.13 Line load over the surface of a semiinfinite soil mass

Use Eq. (6.14) to determine the stress increase () at z = 10 ft below the center of the area described in Problem 6.5. 6.5 Refer to Figure 6.6, which shows a flexible rectangular area. Given: B1 = 4 ft, B2 = 6 ft, L1, = 8 ft, and L2 = 10 ft. If the area is subjected to a uniform load of 3000 lb/ft2, determine the stress increase at a depth of 10 ft located immediately below point O. Figure 6.6 Stress below any point of a loaded flexible rectangular area