DHARMSOIL EXPLORATION 757
18.13 Two samplers have area ratios of 10.9% and 21%.
Which do you recommend for better soil sampling and why?
18.14 Compute the area ratio of a sampler with inside diameter 70 mm and thickness 2 mm. Com-
ment.
18.15 A N-value of 35 was obtained for a fine sand below water-table. What is the corrected value of
N?
18.16 A SPT was performed at a depth of 20 m in a dense sand deposit with a unit weight of
17.5 kN/m^2. If the observed N-value is 48, what is the N-value corrected for overburden?
18.17 A vane, 75 mm overall diameter and 150 mm high, was used in a clay deposit and failure oc-
curred at a torque of 90 metre-newtons. What is the undrained shear strength of clay?
18.18 The inner diameters of a sampling tube and that of a cutting edge are 70 mm and 68 mm respec-
tively, their outer diameters are 72 and 74 mm respectively. Determine the inside clearance,
outside clearance and area ratio of the sampler.