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Micro Piles |
Pressure Grouting |
Rock Anchors |
Permeation Grouting
Soil Nailing |
Compaction Grouting |
Micropiles |
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Chemical Grouting
Our
techniques apply when adding new structures:
especially
rock anchor,
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soil nailing,
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installations for
foundation support.
We
specialize in
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anchors,
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architecture of buildings, bridges,
water plants, sewage plants, tunnels,
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shoring,
underpinning,
agriculture, and
roads
construction. We
are experienced in these applications:
micro piles,
sinkhole repair,
permeation grouting, pressure
grout,
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chemical grouting,
micropiles,
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rock anchors.
Our specialties are
rock anchor,
acrylamide and
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Footing Foundations
JULY
1997
4-11
Figure 4-10: Bearing Capacity Factors for Cohesive Soil
The general bearing capacity equation can also be used to give a field estimate of the
ultimate bearing capacity of temporary footings, such as falsework pads. For granular soils,
a relationship between the standard penetration resistance, N, and the bearing capacity
factors, N
.
and N
q
, is shown in Figure 4-9. For cohesive soils, the relationship between N
and the angle of internal friction, ø, is shown in Figure 4-9. The value of ø determined from
Figure 4-9 can then be used to determine the bearing capacity factors, N
.
, N
c
, and N
q
, as
shown in Figure 4-10. Values for ø, q
u
, N, and
.
can be approximately determined using the
tables for granular and cohesive soils shown in Appendix A. Values for N can also be
determined from the Log of Test Borings.
Settlement
The allowable bearing capacity for granular soils will almost always be governed by
tolerable settlement. When the Structure Foundations Branch of the Office of Structural
Foundations recommends spread footings for bridge structures, they specify net allowable
bearing pressures that will produce no more than
1
/
2
inch of maximum settlement or
1
/
2
inch of differential settlement between footings. These allowable bearing pressures are
generally 25% to 33% of the ultimate bearing capacity as determined by the general bearing
capacity formula.
Frequently bridge fills are constructed on unstable foundation material. When this occurs,
the Structure Foundations Branch will specify that the foundation area be pre-loaded with a
surcharge for a specified length of time, known as a settlement period, prior to the start of