Ground Subsidence, Collapse, and Heave - Geotechnical Engineering Investigation - page 886

Original ground surface

FIGURE 10.45
Site grading and foundation solutions at Menlo
Park, California. (From Meehan, R.L. et al., Proc.
ASCE J. Geotech. Eng. Div., 101, 1975. With
permission.)

Subsurface
drain

Drains

Piers

Buttress key

soil mixed with lime. Protection against surface water infiltration is provided at the pave-
ment edges, adequate underdrainage is provided, and pavement cracks are sealed.

Solutions at Menlo Park
Site Grading
The procedures cited in Meehan et al. (1975) to correct the problems described in Section
10.6.3 called for the stripping of the shallow, surface soils, and keying fills into slopes in a
series of steps. Subsurface drains were provided to prevent water migration into the
expansive weathered rock as illustrated in Figure 10.45.
Foundation support was provided by drilled piers taken to depths of 20 to 30 ft, or to the
sandstone if shallower — a satisfactory but costly solution for homes.
Lime injected into closely spaced holes was not successful in reducing heave, and at times
the situation was aggravated because the lime was added with water.
Pavements were treated by ripping the subgrade to a depth of about 5 ft, injecting
a lime slurry into the loosened claystone, then recompacting the surface before paving
or repaving. New streets were constructed with “full-depth” asphaltic concrete with
typical thicknesses of 5 in. laid directly on the subgrade. When Meehan et al. (1975)
published their paper, the success history of the treatments for pavements was about
2 years.

Possible Solutions for Kansas City
For the problems in the pyritic shales in Kansas city (see Section 10.6.3) , several possible
solutions appear feasible:

Immediate coating of the shale after excavation with bitumen or a comparable
airtight substance

●

Removal of the shales beneath the floor areas and replacement with concrete to
some moderately substantial depth, but with consideration given to the phe-
nomenon reported for the shales in Ottawa (see Section 10.6.3)

●

Bypass the old mine pillars as roof support with concrete supports founded
beyond the active zone of the shale

●

References

Allen, D. R., Subsidence, Rebound and Surface Strain Associated with Oil Producing Operations,
Long Beach, California, Geology, Seismicity and Environmental Impact , Special Publishing.,
Association of Engineering Geology, University Publishers, Los Angeles, 1973.