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Micro Piles |
Pressure Grouting |
Rock Anchors |
Permeation Grouting
Soil Nailing |
Compaction Grouting |
Micropiles |
Injection Grouting |
Chemical Grouting
Our
techniques apply when adding new structures:
especially
rock anchor,
microfine cement,
soil nailing,
micropile
installations for
foundation support.
We
specialize in
slope stabilization,
anchors,
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foundation repair
and support,
grouting,
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micropile installations, and
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architecture of buildings, bridges,
water plants, sewage plants, tunnels,
sinkholes,
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shoring,
underpinning,
agriculture, and
roads
construction. We
are experienced in these applications:
micro piles,
sinkhole repair,
permeation grouting, pressure
grout,
soil nails,
chemical grouting,
micropiles,
compaction grout, and
rock anchors.
Our specialties are
rock anchor,
acrylamide and
compaction grouting,
mini piles,
sinkhole repair,
micropiles,
acrylamide grouting, and
soil nailing.
We will continue to dedicate ourselves to
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insurance mortgage, in our performance, in our
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Driven Piles
JULY
1997
CALTRANS FOUNDATION MANUAL
7-47
CONDITION
DESCRIPTION
1
Loose submerged fine uniform sand. Driving temporarily produces a quick
condition. Retap will probably not indicate capacity.
2
Cohesive soil. Driving temporarily breaks down the soil structure, causing it
to lose a part of it’s compressive strength and shear value. Retap should
indicate increased capacity.
3
Saturated coarse grained pervious material. May display high driving
resistance, but on retap will lose capacity as compared to the initial driving.
This could be due to changes in pore water pressure within the soil mass.
The Standard Specifications provide that the “s” value (inches/blow averaged over the last
few blows) in the ENR formula can be measured when the pile is retapped after a set period.
As in the case of attempting to define the term “refusal”, there are as many interpretations
of acceptable retap criteria as there are interpreters. Interpretations vary from no pile
movement with maximum hammer energy to once or twice the required blow count in one
foot of retap to the minimum blow count in 1 to 3 inches of retap.
When acceptable retap criteria is defined within the context of the Special Provisions, it will
be apparent that the last of the above interpretations (minimum blow count measured over
the initial several inches of retap) complies with the intent of the specifications. This
statement is based on the specification requirement that application of the ENR formula is
the basis of acceptance and, in this formula, pile penetration is measured over the last few
blows. This is not to suggest that all pile inspection be directed toward measuring pile
penetration this way. In fact most engineers prefer to use the more conservative approach
and determine the penetration by counting the number of blows per foot or half foot.
The point of the above is to emphasize the purpose of the retap, which is to measure the
ground “take-up” that has taken place over a given period. Hence, the effort needed to get
the pile moving is of prime importance and should be the prime consideration when
determining acceptability of the piles. Most engineers will argue that once the “take-up”
resistance is overcome (the pile “breaks loose”), the pile will display characteristics identi-
cal to those when it was driven initially.
The Standard Specifications do not specify elapsed time before attempting a retap. Hence,
trial and error methods have to be employed. On contracts where soft driving in clay
materials is anticipated, specific retap guidelines are frequently given in the Special
Provisions. The period is usually set at a minimum of 12 hours unless bearing is obtained
sooner. In addition, only a fixed percentage of the piles are retapped (10% or a minimum of