Page 249 - Safety Memo

Table 1 | Site Conditions That Affect Rock/Soil
Slope Stability
No No This is a silt Type B But check Table 1
Condition Requirement
Soil is fractured/unstable Downgrade to Type B.
dry rock.
Soil is fractured/unstable Downgrade to Type C. Is the soil cohesive? Does the soil exhibit: Medium or greater plasticity? Medium or greater toughness? Medium or greater dry strength? Slow reaction during dilatancy test?
submerged rock.
Soil is cemented (caliche, Classify as Type A.
hardpan, etc.) large enough to be seen with the naked eye? Type A But check Table 1
Soil is fissured. Downgrade from Type A to Are at least 50% of the grains (by mass)
Type B. s
Soil is subject to vibration. Downgrade from Type A to ≥ 1.5 t
Type B.
Soil has been previously Downgrade from Type A to Type B But check Table 1
disturbed. Type B. Yes This is a clay Estimate the unconfined compressive strength. 0.5 – 1.5 tsf
Soil is submerged or water is Downgrade from Type A to
freely seeping through the Type C. Illustration 5
sides of the excavation. Downgrade from Type B to No
Type C. Type C
≤ 0.
Soil profile is layered with Downgrade from Type A to
the layers dipping into the Type C.
excavation on a slope of Downgrade from Type B to
four horizontal or steeper. Type C. 16" No a sand This is Type C
Is soil submerged or is water freely seeping through the side of the excavation? Yes Are at least 50% of the visible grains (by mass) larger than 3 / No Type C

Start Here Yes Type C Yes This is a gravel Are grains angular? Yes Type B But check Table 1

56 Cal/OSHA Pocket Guide for the Construction Industry June 2019 Cal/OSHA Pocket Guide for the Construction Industry | June 2019 57