S n o w

C o v e r

S t a b i l i t y,

A v a l a n c h e

I n i t ia t i o n

a n d

F o r e c a s t i n g

sionallywithin an adjacent range (e.g.moderate to easy-
moderate). It is not common forscores fromdifferent op-
erators to spread over three ranges (e.g. easy to easy-mod-
erate to moderate). This variability of compression scores
isroughlycomparabletorutschblockvariabilitywhere
repeatedscores vary within 1 of 7 steps, two-thirds of the
time (Jamieson and Johnston,1993).

EFFECT OF SLOPE INCLINATION

To assessthe effect of slope inclination on compression
scores,same-daycomparisonswereconductedonfour
slopes where the inclination varied from as low as 0º to as
much as 40º. At each slope, 3 to 5 compression tests were
done at 3 to 5siteswith different slope inclinations.The
compression scores (numberof taps tocause failure) for
each site are givenin Table 3.Theresultsfor3ofthe4
slopes are also shown in Figure 4 along with the depth of
the weak layerat each site.The scoreson 96-02-13 and
96-02-14showatendencytodecreasewithincreasing
slope inclination except for at the steepest sites where the
increase may have been due to the observed increase in
depth of the weak layer.Only 3tests were done ateach
site on 96-02-09 (Table 3 and Figure 4) and 96-01-24 (Ta-
ble 3) and an effect of slope inclination on these compres-
sion scores is not apparent. More tests per site are recom-
mendedforfuturestudiesofslopeeffects.

EFFECT OFVARYING CROSS-SECTIONAL AREA OF
THE COLUMN

During the winter, seven trials were conducted in which
crosssectionsofcolumnsrangedfrom20x 20cmto
40 x 40 cm as shown in Tables 4a and 4b and Figure 5. (In
several cases,more than 30 taps were applied to prevent
the distribution from being truncated.) The figure clearly
shows the mean number of taps increasing with the length

range marked by the whiskers approximately two-thirds
of the time. Using the leftmost boxand whiskerin Figure
3 as an example, two-thirds of the scores obtained by Op-
erator 1 on 95-12-28 forthe shallow layer (FC DF 1) prob-
ably lie between 4 and 7 taps.More importantly, most of
the scores obtained forthe shallow layerbyboth opera-
tors are in the easy range. Similarly, the for the second set
of comparisons on 95-12-28,most of the scores lie in the
moderate-hardrange.Forthecompressionscorescom-
pared on 96-03-06, most of the scores range between mod-
erate andmoderate-hard. For the compression scores com-
pared on 96-03-14, most of the scores range between easy
and easy-moderate. Compression scores obtained from dif-
ferent operators generally fall in the same range, orocca-

Compression

Tests-Slope

Effects

Purcells,MonasheesWinter1995-96

SlopeInclination(º)

Figure 4 Effect of slope inclination on compression scores. The depths (cm) of the
weak layers are marked beside the points.

77