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Four sand types, marked as I, II, III, and IV, were chosen for laboratory testing. These sands were classified as very coarse, gravelly, fine, and silty sand, respectively, and they cover a broad range of hydraulic conductivities typical for most water-bearing formations, i.e., from 10−5 to 10−3 m/s. Their conductivity values were determined empirically from the grain size distributions and experimentally in a permeameter using the constant-head method (Table 1). Moreover, minor adjustments to the W-tube apparatus made it possible to perform additional constant-head permeability measurements for all samples placed in the small cylindrical chambers. Since testing required filling the W-tube with the same type of sand more than once, the hydraulic conductivity of every analyzed sample was known. The results of hydraulic conductivity measurements performed in the W-tube are shown in Figure 3.
Table 1

Hydraulic conductivity values of the sand samples k [m/s]

Hydraulic conductivity k [m/s]
No.Sand typeFrom the Hazen equationFrom the USBSC equationBased on the constant-head test in a permeameterBased on the constant-head test in the U-tube
Very coarse sand 7.81 × 10−3 3.77 × 10−3 1.71 × 10−3 (2.24 ± 0.25) × 10−3 
II Gravelly sand 3.38 × 10−4 4.90 × 10−4 3.04 × 10−4 (1.66 ± 0.23) × 10−4 
III Fine sand 5.10 × 10−5 2.74 × 10−5 5.35 × 10−5 (4.99 ± 0.96) × 10−5 
IV Silty sand n/a* 1.08 × 10−5 1.81 × 10−5 (1.42 ± 1.21) × 10−5 
Hydraulic conductivity k [m/s]
No.Sand typeFrom the Hazen equationFrom the USBSC equationBased on the constant-head test in a permeameterBased on the constant-head test in the U-tube
Very coarse sand 7.81 × 10−3 3.77 × 10−3 1.71 × 10−3 (2.24 ± 0.25) × 10−3 
II Gravelly sand 3.38 × 10−4 4.90 × 10−4 3.04 × 10−4 (1.66 ± 0.23) × 10−4 
III Fine sand 5.10 × 10−5 2.74 × 10−5 5.35 × 10−5 (4.99 ± 0.96) × 10−5 
IV Silty sand n/a* 1.08 × 10−5 1.81 × 10−5 (1.42 ± 1.21) × 10−5 

*The following condition is not satisfied: 0.1 < d10 < 3.

Figure 3

Hydraulic conductivity measurements performed in the W-tube for all tested sand samples.

Figure 3

Hydraulic conductivity measurements performed in the W-tube for all tested sand samples.

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