Table 1. Borehole soil log.*
Depth to
Thickness
bottom of layer
of layer
Layer
(m)
(ft)
(m)
(ft)
Soil type
1
3.4
11
3.4
11
Medium sand
2
4.9
16
1.5
5
Fine gravel
3
5.8
19
0.9
3
Medium sand
4
7.6
25
1.8
6
Medium sand and water
5
7.9
26
0.3
1
Clayish fine sand
6
23.2
76
15.2
50
Medium sand and water
7
23.5
77
0.3
1
Blue clay
8
23.8
78
0.3
1
Medium and sand water
9
24.4
80
0.6
2
Blue clay
10
24.7
81
0.3
1
Brown clay
11
27.4
89
2.7
9
Medium sand and water
12
29.3
96
1.8
6
Clean sand and water
13
30.5
100
1.2
4
Medium sand and water with
clay trace in water
*From Hal Carlson, Jim's Well Drilling, Grayling, Michigan.
presence of the frost layer. For recordings made
m apart. The measured first arrival travel times for
close to the hammer source, the first arrival was a
the P- and S-wave refraction experiments along
wave traveling directly through the frost layer, at
with least-squares line fits are shown in Figures 8
a speed of about 590 m s1. Fortunately, this arrival
and 9.
was highly attenuated and died out within a few
Analysis of the travel times indicates a surface
meters. We were able to pick the travel times of the
layer 4.8 m thick with a P-wave velocity of 290
m s1, underlain by a layer with a velocity of 1660
later-arriving refracted waves after this first ar-
m s1 that is identified as the water table. The shear
rival and use them in the analysis. The P-wave
velocity of the thin snow layer was measured at
wave data reveal a surface layer with a velocity of
about 100 m s1 by a short line of geophones placed
150 m s1, 12 to 15 m thick, sloping downward at an
above and below the snow cover and spaced 0.25
angle of about 9 degrees to the north, above a layer
Table 2. Physical properties of borehole soil samples.
Percentage of soil type
Moisture
Sample
Depth
Density
content
Gravel
Sand
Sand
Sand
(kg m3)
no.
(m)
(ft)
Description
(%)
fine
coarse
medium
fine
Clay
1
1.5
5
Sand
1.38
3.7
7.6
1.8
34.5
63.5
0.3
2
3.0
10
Sand
1.45
3.4
4.6
2.0
33.0
63.9
1.0
3
4.0
13
Sand and gravel
1.56
2.8
18.2
10.2
35.7
35.6
1.1
4
6.1
20
Sand (below
1.45
3.4
0.4
0.3
12.9
86.7
0.4
water table)
5
13.7
45
Sand
1.45
19.2
0.0
0.2
10.0
88.1
1.7
6
22.9
75
Blue clay
--
23.2
0.0
0.1
7.1
53.4
39.4
7
24.4
80
Brown clay
--
6.8
0.0
0.1
4.4
35.5
60.0
8
30.5
100
Sand with clay
1.73
19.4
0.0
0.0
15.0
75.7
9.4
The percentage of gravel, sand, and clay in each sample was determined from the grain size measurements. According to the unified
soil classification scheme, soils with grains smaller than 9.5 mm but larger than 2 mm are classified as fine gravel. Sand has grain sizes
less than 2 mm and greater than 0.076 mm and is further divided into coarse, medium, and fine at the 0.59 mm and 0.25 mm sizes.
Grains less than 0.076 mm can be either silt or clay, but are assumed here to be clay based on field observations of the samples.
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