17.12: Appendix L- The Properties of the 105 μm Sand

The sand in the new laboratory DE, with a d₅₀ of 105 μm, is examined for the following soil mechanical parameters:

1. The minimum and the maximum density, Table L-1: Pore percentages, indicated are the average measured densities for the various blade angles.

2. The saturated critical density, Table L-1: Pore percentages, indicated are the average measured densities for the various blade angles.

3. The permeability as a function of the density, Table L-2: Permeabilities, indicated are the average permeabilities for the various blade angles.

4. The angle of internal friction as a function of the density, Table L-4: The angle of internal friction as a function of the pore percentage.

5. The d₅₀ as a function of the time, Table L-3: The d50 of the sand as a function of time.

6. The cone resistance per test.

7. The density in the test stand in combination with the cone resistance.

The points 6 and 7 need some explanation. As with the 200 μm sand density measurements are performed in situ with the aid of a Troxler density measuring set. The calibration formula for the 105 μm sand is:

\[\ \mathrm{n=\frac{69.9}{C_{p}^{0.068}} \quad\text{ with: n in %, }C_{p}\text{ in kPa}}\tag{L-1}\]

In which the cone resistance is determined in a top layer of 12 cm, where the cone resistance was continuously increasing and almost proportional with the depth. The value to be used in this equation is the cone resistance for the 12 cm depth.

With the aid of this equation it was possible to determine the density for each cutting test from the cone resistance measurements. As, however, new sand was used, the density showed changed in time. The sand was looser in the first tests than in the last tests. This resulted in different average initial densities for the different test series. The tests with a 45^o blade were performed first with an average pore percentage of 44.9%. The tests with the 60^o blade were performed with an average pore percentage of 44.2%. The tests with the 30^o blade were performed with an average pore percentage of 43.6%. Because of the consolidation of the sand a relatively large spread was found in the first tests.

Table L-2 lists the permeabilities corresponding to the mentioned pore percentages. By extrapolation in Table L-2 a permeability of 0.00017 m/s is derived for the maximum pore percentage of 51.6%.

The sand bed is flushed after the linear tests because of the visibility in the water above the sand. In the tables it is indicated which soil mechanical parameters are determined after the flushing of the sand bed.

Table L-1: Pore percentages, indicated are the average measured densities for the various blade angles.

Minimum density	51.6%
Maximum density	38.3%
Initial density 30 o	43.6%
Initial density 45 o	44.9%
Initial density 60 o	44.2%
After the flushing
Minimum density	50.6%
Maximum density	37.7%
Saturated critical density	44.5%

Table L-2: Permeabilities, indicated are the average permeabilities for the various blade angles.

Pore percentage	Permeability (m/s)
42.2%	0.000051
45.6%	0.000082
47.4%	0.000096
49.4%	0.000129
Initial
43.6%	0.000062
44.2%	0.000067
44.9%	0.000075
After the flushing
39.6%	0.000019
40.7%	0.000021
41.8%	0.000039
43.8%	0.000063
45.7%	0.000093
48.3%	0.000128

Table L-3: The d₅₀ of the sand as a function of time.

Date	d50 (mm)
06-08-1986	0.102
06-08-1986	0.097
06-08-1986	0.104
06-08-1986	0.129
06-08-1986	0.125
06-08-1986	0.123
29-08-1986	0.105
29-08-1986	0.106
29-08-1986	0.102
16-09-1986	0.111
16-09-1986	0.105
16-09-1986	0.107

Table L-4: The angle of internal friction as a function of the pore percentage.

Pore percentage	Cell pressure kPa	Angle of internal friction
Saturated undrained		After the flushing
44.7%	100	33.5^o
44.9%	200	33.3^o
44.5%	400	32.8^o
42.6%	100	35.0^o
42.1%	200	35.5^o
42.2%	400	34.8^o
39.8%	100	38.6^o
39.9%	200	38.3^o
39.6%	400	37.9^o

Figure L-1: The PSD of the 105 μm sand.