Qatar University

College of Engineering

Department of Civil & Arch. Engineering

1. Direct shear box test results for clayey sand specimens tested at three different normal stresses

are shown in Table 1.

a. Plot the shear stress-shear displacement relationship and determine the peak shear strength at

each normal stress. At which value of shear displacement would the peak shear strength be

mobilized?

b. Draw the failure envelope for the peak shear strength. Use the same scale for the x and y axes.

e. Determine the shear strength parameters and write the equation that can be used to estimate

the peak shear strength (5,) of the tested soil.

Table 1. Test results for soil tested in direct shear apparatus

Normal Stress (G)-42 kPa

Time, see (t)

0

30

60

90

120

150

Proving ring reading

(Div.)

0

15.9

27.4

37.1

45

52

Foundation Engineering I (CVEN 330)

Assignment No. 1 (Sep. 21, 2023)

180

210

240

270

300

330

360

390

420

450

480

510

540

Use the following to process the data:

57.4

61.8

65.2

68.8

69.7

68

61.8

15.9

G-78 kPa

Proving ring reading

(Div.)

0

31.8

51.2

65

• Area of shear box-6×6 cm² -0.0036 m²

Shear rate=0.01 mm/sec

• Proving ring constant-0.00204 kN/div

•

74.1

85.4

93.2

104.8

108.7

109.4

108.5

98.8

31.8

G-130 kPa

Proving ring reading

(Div.)

0

45.9

70.6

91.75

Shear Displacement, &-Shear rate time

Shear Force, T-Proving ring constant Proving ring reading

Shear Stress, T-T/cross-section area of shear box

107.65

120

129.5

138.7

146.1

151.2

157.95

162.35

166.2

169.4

171.9

174

175.5

173.5

169.4

Hint: You may use the following equations to process the data of the table, and show

detailed calculations in your solution.