Moving Sarsen Stones on Ice

Bearing Capacity of Freshwater Ice
Gold Formula
The most accepted ice capacity guideline, developed by Dr. Lorne Gold of the National Research Council of Canada. Dr. Gold dedicated most of his professional career to ice related engineering studies.

Ice Capacity Using the Gold Formula

P= allowable load capacity of the ice in kilograms.
H= Blue or natural ice thickness in centimeters
W= White ice (flood ice) thickness in centimeters
For solid blue ice:
P= 7.03 X H2
For blue and white ice combined:
P= 7.03 X (H + 1/2W)2

METRIC
Depth
(Cms) Capacity (Kgs)
2 = 28
4 = 112
6 = 253
8 = 450
10 = 703
12 = 1,012
14 = 1,378
16 = 1,780
18 = 2,278
20 = 2,812
22 = 3,403
24 = 4,049
26 = 4,752
28 = 5,512
30 = 6,327
32 = 7,199
34 = 8,127
36 = 9,111
38 = 10,151
40 = 11,248
42 = 12,401
44 = 13,610
46 = 14,876
48 = 16,197
50 = 17,575
52 = 19,000
54 = 20,499
56 = 22,046
58 = 23,649
60 = 25,308
62 = 27,023
64 = 28,795
66 = 30,623
68 = 32,507
70 = 34,447
72 = 36,443
74 = 38,496
76 = 40,605
78 = 42,771
80 = 44,992
82 = 47,270
84 = 49,604
86 = 51,994
88 = 54,440
90 = 56,943
92 = 59,502
94 = 62,117
96 = 64,788
98 = 67,516
100 = 70,300

So a 50 tonne sarsen stone would need continuous good ice of 85cm depth. Flooded marsh land and flowing rivers and ice on the edge of a channel are not "good" ice and so a greater depth would be needed.

Upto 75 large stones were moved so these conditions would have to have been met repeatedly for them to have been skidded down the frozen River Avon.