COMPOSITE “HELICAL”
PIPE PILE - CHPP SYSTEM
TM
INFORMATION MANUAL
Method for Estimating the Theoretical Ultimate
Axial Capacity of a Large Diameter Helical Pipe Pile
The Engineering Calculations presented in this
manual are widely used and universally accepted as
time proven methods to calculate the overall capacity
of (2) specifically different types of piles. Combining
the two methods is proving to be an accurate and an
acceptable means to formulate the capacity of the
CHPP System. Adding the end bearing capacity of
multiple helical discs along with the developed skin
friction of the large diameter pipe piles outer wall to
the soils is working. Performed load tests are proving
that this Calculation Method can be used to estimate
Ultimate Capacities for Tension / Compression Loads.
“We have to do them,” no doubt about it!
“Piling Load Tests” are the only true way of verifying and
proving the overall performance of a selected piling system
to the specific site and soil conditions.
“Good Soil Boring Information from the Geotechnical
Engineers,” is absolutely necessary to properly design any
type of pile. This includes the Composite “Helical” Pipe Pile.
Installing a “Helical Test Probe” is another valuable form or way of gathering
site and soil information prior to engineering, load testing or project pile
installations. Used in conjunction with soil boring information provided by the
Geotechnical Engineer, a selected square shaft helical anchor / pile configuration
can be installed to provide very useful, “real-time installation reactions” of the
helical disc performance in the variable soil conditions. By recording the
installation torque values at every foot of installation depth, a chart can be
generated showing the increase or decrease in the soil strengths along with the
compression and tension capacity of the Helical Anchors Point Bearing Capacity
at the various depths. This information is extremely useful in estimating the
required installation depth of the “Composite Helical Pipe Pile.”
U.S. PATENT NO. 6,814,525 (4) PATENTS PENDING U.S. & INTERNATIONAL
Page 1 of 16
“ Piling Load Tests” provide valuable design
information. They also provide a high level of
assurance to all parties involved that the correct
piling system is being considered for the project.
The Innovative Design of the Composite “Helical” Pipe Pile
System allows for widespread uses in many unique situations
and locations for new construction or renovations projects.
Information Manual Index
Pages 3– 6 Section 1
Individual Plate Capacity (IPC) Method for
Determining Helical Disc Ultimate Capacity
Pages 7– 8 Section 2
Method of Determining Friction (Adhesion)
Soil Reaction to Pipe Pile Surface Area
Pages 9 - 10
ENERGY STRUCTURES INC. “PILECAP”
Composite Helical Pipe Pile Capacity in Soil
Calculation Program Example w/Data Chart
Pages 11
Load Test Example “ N.O. Fairfield Resort”
Pages 12 - 13
Product Specifications and Detail Drawings
w / Catalog Numbering System
Page 14 - 15
“This is Not Rocket Science By Any Means”
Very Brief Installation Process & Information
Page 16
Last Pages
Installation Photos Reagan Ranch Visitor Center
General Information Brochures
Page 2 of 16
WR Document No. 050627
Rev.: August 16, 2005
Section 1 - Individual Plate Capacity (IPC) Method
A Method for Estimating the Theoretical Ultimate Axial Capacity of a Helical Screw Pile, Adapting
Terzaghi’s General Bearing Equation
_______________________________________________________________________________________________
Parameters:
1.
This method addresses only the theoretical ultimate helix / soil bearing capacity. Friction (adhesion) between
the pile’s surface and the soil is discussed in Section 2 (page 7) of this document.
2.
The minimum spacing between any two helixes shall be 3 times the diameter of the smaller helix. If the
distances between helixes are significantly less than 3 diameters, the ultimate theoretical capacity of the pile
may be reduced. In these cases, the pile manufacturer shall provide the appropriate de-rating factors.
3.
The IPC method assumes that the mechanical capacity of the pile assembly exceeds the design load by an
appropriate safety factor.
4.
The IPC method assumes that the pile will behave as a deep foundation, i.e. the top helix will be installed to a
depth equal to at least 5 times its diameter.
5. The ultimate capacity of an individual helix is equal to the product of the effective bearing stress capacity of the
soil times the projected area of the helix. The ultimate theoretical pile capacity is simply the sum of the
individual helix capacities.
6.
The equations shown below assume soils of medium plasticity and sensitivity and do not apply to highly sensitive
soils. Highly sensitive soils should always be avoided with helical screw piles. This can often be accomplished
by increasing the depth of the pile beyond the sensitive strata as indicated by the boring logs. If this cannot be
accomplished, full-scale load testing will be required to determine the theoretical ultimate pile capacity and the
specified installation torque for the pile
Terzaghi’s General Bearing Equation
[Equation 1.1]
qult(g) = Ah x ((c x Nc) + (q x Nq) + (.5 x UW x B x Nb))
Where:
Ah = Project Area of the Helix
qult(g) = Ultimate geotechnical bearing capacity of an individual helix. The upper limit of this term is the
minimum ultimate mechanical capacity of the helix as rated by the pile manufacturer.
c = Cohesion of soil adjacent to the helix
Nc, Nq, Nb = Bearing Capacity Factors
Nc = 9 for clay soils of medium plasticity and sensitivity with a friction angle of 0.0 degrees.
Nq values are shown below. Charts 1.1 and 1.2
q = Effective overburden pressure
UW = Effective Unit Weight of the soil.
B = Base Width
For helical screw pile foundations, the base width term (.5 x UW x B x Nb) is relatively small and can be
neglected with little error. Eliminating the Base Width Factor from equation 1.1 results in the following
general equation (see Equation 1.2) for determining the ultimate capacity of an individual helix.
©Copyright 2005 Energy Structures Inc.
Page 3 of 16
qult(g) = Ah x ((c x Nc) + (q x Nq))
(1)
(2)
[Equation 1.2]
(3)
The ultimate theoretical pile capacity (excluding pile/soil friction) is the sum of the individual
helix capacities as determined from Equation 1.2. This equation includes the following three
terms:
Term (1) - The projected area of the helix (Ah)
Term (2) - [Cohesion Term - Clay] The effective ultimate soil stress capacity that will be
provided by the soil’s cohesion.
Term (3) - [Depth/Friction Term - Sand] The ultimate soil stress capacity that will be
provided by a combination of the effective overburden pressure (q) and the friction angle of
the soil. Overburden pressure (q) is the product of the average effective unit weight of the
soil times its depth and is referred to as the depth term.
Nq is a function of the friction angle of the cohesionless soil and is referred to as the friction
term. Chart 1.1 is based on the Meyerhof equation for Nq. This curve shown in Chart 1.1 has
been modified for helical screw pile applications.
The effective bearing stress capacities of the soil (i.e. the sum of terms 2 and 3 of Equation 1.2) are
determined from data extracted from geotechnical reports and boring logs. The IPC method averages the
soil’s strength parameters for an axial distance of 3 helix diameters from each helix in the direction of load.
Using this method, computer programs such as ESI’s “PileCap” calculates the theoretical ultimate capacity of
each helix for each foot of penetration. The results are then summed and the theoretical ultimate pile capacity
is determined for each foot of penetration for both tension and compression loading. Results are shown on a
chart that plots Ultimate Compressive and Tension Capacities against Depth for the selected helix
configuration. In soils with abrupt changes in strength, the ICP method requires additional consideration by the
engineer. In these types of soils, simply averaging the soil strength for 3 diameters may give incorrect values
of the helix capacity. This is one of many reasons that only an experienced engineer should apply these or
other theoretical methods for determining the capacity of any type of pile.
Cohesive Soil (Friction Angle = 0.00 degs)
Eliminating item 3 (depth/friction term) from Equation 1.2 yields the following equation:
qult(g) = Ah x (c x Nc)
Where:
Nc = 9 for clay soils of medium plasticity and sensitivity with a friction angle of 0.0 degrees.
So:
qult(g) = Ah x (c x 9)
[Equation 1.3]
Most boring logs include blow counts N (ASTM D 1586) but often do not include cohesion
values. In this case, the following equation may be used for clays of medium plasticity to
estimate their cohesion. Equation 1.4 is based on empirical studies and should be used with
caution. We recommend using tested values of cohesion when at all possible.
c (ksf) = N/8
[Equation 1.4]
Where: N = Blow Count Value per ASTM D1586 Standard Penetration Test
©Copyright 2005 Energy Structures Inc.
Page 4 of 16
Cohesionless Soils (c = 0.00)
Eliminating item 2 (Cohesion Term) from equation 1.2 yields the following equation:
qult(g) = Ah x (q x Nq)
See Note 6.
[Equation 1.5]
Where:
q = Effective overburden pressure is defined as the average unit weight of the soil times
its depth. The effective unit weight of soil at or below the water table will equal its
saturated unit weight minus the unit weight of water.
Nq = Bearing Capacity Factor for Cohesionless Soil – Nq is a function of the internal
friction angle of the soil. Chart 1.1 shows this relationship. Soil boring reports and bore
logs often do not provide the soil’s friction angle, but usually will provide the N blow
counts. In this case Chart 1.2 shows an approximate relationship between N blow count
and Nq. This chart is based on empirical data and should be used with caution. We
recommend using friction angle whenever possible.
Chart 1.1
Bearing Capacity Factor (Nq) for Cohesionless Soils
Nq vs. Friction Angle
100
80
60
Nq
40
20
0
0
5
10
15
20
25
30
35
40
45
50
Angle of Internal Friction (degrees)
Chart 1.2
N vs Nq
120
100
80
Nq 60
40
20
0
0
10
20
30
40
50
60
70
N (spt blow count)
© Copyright 2005 Energy Structures Inc.
Page 5 of 16
Mixed or c - ISoils
Typically the IPC method assumes that the soil stratum at a particular depth is either
cohesive (friction angle = 0.00 degs) or cohesionless (cohesion = 0.00). If the soil
stratum includes both cohesive properties and friction properties it is referred to as a
mixed or c - IОsoil. The bearing stress capacity of this type soil can easily be
determined from equation 1.2, but very accurate values of c, Nc and Nq are
necessary. Mixed or c - Isoils should be approached with caution. We recommend
that the engineer be familiar with this type of soil and the jobsite soil conditions.
An alternate approach:
Notes:
If the engineer cannot determine the expected soil behavior (i.e. cohesive or
cohesionless), he should perform the calculations for both types of soils and choose
the lesser capacity. An appropriate safety factor should then be applied.
1. The reliability of these methods or other theoretical methods to predict ultimate pile capacities is
dependent upon the quality of the soil data and their interpretation by the engineer.
2. Only experienced engineers should apply these methods or other theoretical methods.
3. Theoretical ultimate pile capacities (as determined by this or any other method) are based on empirical
equations and should always be verified by full-scale load testing.
4. All piles shall be installed to a specified installation torque value recommended by the design engineer.
Ultimate torque values not to exceed mechanical ratings set by the manufacture’s guidelines or
specifications.
5. Theoretical ultimate pile capacity is defined here as the minimum load which will cause continuous
deflection (creep) without an increase in load.
6. Designing Helical Screw Piles for Cohesionless Soils
As shown in Equation 1.5, the theoretical ultimate helix capacity is directly proportional to the effective
overburden pressure (q). The effective unit weight of soil at or beneath the water table is equal to its
in-situ unit weight minus the unit weight of water. For this reason a rise in water table can
significantly reduce pile capacity. If a rise in water table can occur after construction is completed,
the engineer should take the following steps.
x
Preliminary Design - Assuming the highest possible water table and using the IPC method
described above, to design the pile.
x
Check Preliminary Design at the lowest possible water table depth - Assuming the lowest possible
water table depth that can be expected during construction, determine the theoretical ultimate pile
capacities (and the expected installation torques) for each foot of installation. The pile capacities
(and installation torques) at the lower water table will be greater. This increase can be significant
and may require a pile with greater torsional capacity and/or different helix configuration than
originally proposed. Modify the preliminary pile design if/as required.
x
Final Design and Check – Assume the highest water table and determine the theoretical ultimate
capacity of the final pile configuration.
© Copyright 2005 Energy Structures Inc.
Page 6 of 16
Section 2 – A Method of Determining Friction (Adhesion) between Soil and the Pipe Pile’s Surface
Naval Facilities Engineering Command, “Foundations & Earth Structures”, Design Manual 7.02,
September 1986
——————————————————————————————————————————————————————
Skin friction between the soil and a typical Helical Screw Anchor with shaft sizes of 3.5” OD or less is relatively
small when compared to the total helix capacity, and for this reason friction can be neglected with little error.
But for deep piles with larger sections (i.e. 6” or larger), friction becomes more significant. A convenient
method of estimating this friction (or adhesion) is shown in the Naval Design Manual 7.02 and is discussed
below.
The estimated ultimate axial capacity of a Composite Pile (Friction + End Bearing) such as the
Composite “Helical” Pipe Pile CHPP ™ can be shown by the following equation:
QT = QH + QF
Where:
QT = Total theoretical axial capacity
QH = Sum of individual helix capacities as discussed above.
QF = Total friction (adhesion) between the soil and pile surface as discussed below.
Cohesive Soils
QF = CA x (Pi x D) x L
Where:
CA = Adhesion based on the soil’s cohesion as shown on the table (shown below) in the Navy Design
Manual Figure 2 – p. 7.2-196.
D = Pile diameter
L = Length of Pile subjected to adhesion or friction.
RECOMMENDED VALUES OF ADHESION – For Steel Piles
Consistency of Soil
Cohesion, C (psf)
Adhesion, CA (psf)
Very Soft
0 - 250
0 - 250
Soft
250 - 500
250 - 460
Med. Stiff
500 - 1000
460 - 700
Stiff
1000 - 2000
700 - 720
Very Stiff
2000 - 4000
720 - 750
© Copyright 2005 Energy Structures Inc.
Page 7 of 16
Cohesionless (Granular) Soils
QF = q x K x TAN (fa’) x Pi x D x L
Where:
q = Effective overburden stress (i.e. vertical stress) acting on length “L”. The Naval Manual referenced
above limits q to its value at a depth of 20 x B. It should be noted on the calculation sheets if greater
values of q are applied.
K = Coefficient of Lateral Earth Pressure – Ratio of horizontal to vertical effective stress. Values of K0
are generally recommended here. Unless other information is provided, a value of K = 1.0 is often
used in the above equation.
fa’ = Friction Angle between the soil and pile surface. (Not to be mistaken as the internal angle of
friction of the soil.) For Steel Piles the Naval Manual recommends 20 degrees, but unless otherwise
noted we recommend that fa’ be set to a more conservative value of 14 degrees. This assumes a silty
sand, gravel or sand mixed with silt or clay as referenced in Bowles – Foundation Analysis and Design
– Fourth Edition.
Note:
1. Usually the top portion of a pile will be in disturbed soil and will not contribute significantly to the
friction. For this reason, the upper section of the pile is often ignored when determining friction.
For helical screw piles, the top 5 ft. of the pile is often disregarded.
© Copyright 2005 Energy Structures Inc.
SEISMIC RETROFIT– EARTHQUAKE UPGRADE
Ronald Reagan Ranch Visitors Center Building Santa Barbara, California
Page 8 of 16
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ESTIMATED CAPACITY OF THE
ORIGINALLY PROPOSED HAMMER
DRIVEN 8” AND 10” OPEN ENDED
SEGMENTED STEEL PIPE PILES
+
(15) Tons @ 50’Depth
“ THE COMPOSITE “HELICAL” PIPE PILE – CHPP ™ SYSTEM” is
THE PREFERED PILING SYSTEM FOR THE PROPOSED (9) STORY “FAIRFIELD RESORTS COMPLEX.”
The scope of the work is to install “CHP PILES” to approximately 55 ft. deep in the old existing (6) story masonry
brick building that is now resting on corbeling brick footings and cypress mats. At the same time additional piles
are to be installed to the same depth in a rear adjoining older building site for a proposed New (9) Story Structure.
Once the existing (6) story building has been underpinned and it’s structural load’s have been transferred to the,
“Newly installed CHPP Deep Pile Foundation (3) additional floors are to be constructed on top.” Thus making the
(2) joined building’s into, “The Proposed (9) Story (134 Resident) Fairfield Resorts La Belle Maison Complex.”
Page 11 of 16
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“THIS IS NOT
ROCKET SCIENCE
BY ANY MEANS”
DESIGNED USING
S.W.A.G.E. TECHNOLOGY
Installation Information
The Composite “Helical” Pipe Pile System is very simple!
It’s design started with a need and evolved with time and plenty of effort. A lot
of thought was given to making the product as they say, “user friendly or kiss.”
It is a helical anchor transitioning to a much larger diameter, segmented thin
wall steel pipe, that is bolted together, and used as a casing. The installation
process is easy. Simply screw a selected industry standard helical anchor lead
unit into the ground. Bolt the helical lead unit to the pipe casing transition unit.
Insert the square internal drive mandrel into the upwardly facing squared female
upset end of the transition unit. Engage the hydraulic drive head to rotate the
pipe into the ground. Stop the pipe at the desired height (or elevation) and install
an extension unit by placing the male end of the extension unit into the again
upward facing female end of the installed transition unit. Install the (4) provided
extension unit connection bolts w/ washers through the aligned and matching
punched holes to the internal welded nuts, located inside of the square male end
of the pipe. Engage the bolts in the nuts and tighten them with an electric impact
pulling the flat sides together. Once again install the square internal drive
mandrel into the square ended female upset end of the extension. Engage the
hydraulic drive head to rotate the pipe into the ground once again. Continue
these same steps until the predetermined depth or the desired installation torque
has been reached per the Engineers Specifications.
Once the pipe pile is installed properly into the ground, the pipe is cut to the
correct elevation. This installed pipe is now a hollow, debris free, unobstructed
avenue. It can be inspected with a flash light. The depth and diameter of the pile
can be checked with a measuring tape to determine the exact amount of cement
that is needed. Steel reinforcing or post tension cables can be installed inside the
open pipe if needed. Low cost concrete can be placed inside the pipe casing at
any time from a cement delivery truck.
THE COMPOSITE HELICAL PIPE PILE IS VERY SIMPLE,
WHEN COMPARED WITH OTHER HELICAL TYPE SYSTEMS.
There are no specially formulated grout (recipes) with additives or high speed
mixing procedures required. There are no regimented grout placement processes
during the installation. There is no measuring and calculating to verify (justify)
that the “guesstimated exact amount” of liquefied, super-flowable, and very
expensive grout is going down the hole or “NOT.”
And when all of the above does not work, there is no having to stick a “pig”
on the slender shaft and screw him into the earth. “hoping he will help hold
back Mother Nature .” (Possibly) this may allow the calculated exact amount of
“gravity fed” grout per the specifications to flow more “freely” down the
perfect non - dimensional dirt hole while mixing with the surrounding soils!!???
Page 14 of 16
Advantages of the
Special note:
Environmentally Friendly
Perfect for Marine Type
Applications
The Composite “Helical”
Pipe Pile System can be
installed in Bayous,
Rivers, Lakes, or
Ponds and filled
with cement
if needed.
U.S. PATENT NO. 6,814,525
(4) PATENTS PENDING
U.S. & INTERNATIONAL
Composite “Helical”
Pipe Pile-CHPP ™
SYSTEM
x
“High Capacity” Large Diameter Steel Pipe Pile
x
The installed hollow pipe casings interior can be
inspected using a flashlight with its overall depth
and dimensions checked with a measuring tape.
x
No bending or buckling concerns as associated with
slender shaft helical anchors.
x
Good lateral resistance as compared to others.
x
Sections can be supplied in any length required.
Short bolted sections can be used for installations
in areas with low head clearance such as inside
buildings, oil refineries, and chemical plants.
x
10’ Foot Sections can be carried by (2) men.
x
No spoils will result from the installation of the
CHPP. Very little disturbance to the work area.
x
No vibration or noise. The CHPP can be installed
near existing structures, or next to operating
machinery and equipment, also in populated areas.
x
Post Tension cables, rebar cage, or high strength
threaded rods /bars can be installed if needed.
x
The CHPP system will accommodate any type of
grout. Grout / concrete can be supplied directly
from a standard cement delivery truck at any time
during construction or after construction. No stand
by is required. Also the pipe casing can be left
unfilled for lighter loads if required.
x
Standard equipment normally used for the
installation of standard helical screw anchors can
usually be used to install the CHPP.
x
Personnel experienced in the installation of
standard helical screw anchors can install the
CHPP with minimum training. Certification or
instructions usually requires one day.
x
Installation time and material cost for the CHPP is
usually less than that of similar piles.
x
Straightforward installation procedures are
provided to minimize installation time and cost.
Installation process is simple!
No complicated procedures or
Special Mix Recipes to “Muck up.”
x
Page 15 of 16
President Ronald Reagan’s Ranch Visitors Center Building
“Seismic Retrofitting” is being done to the older existing building using
(104) Composite “Helical” Pipe Piles-CHPP installed to 32’ depth with an
ultimate capacity of 130 kips per pile. Original design called for (270)
3.5” Pipe HS Type Anchors to a depth of 40’ with an ultimate capacity of
only 70 kips. Using the CHPP System reduced the number of piles by (166).
This reduction in the number of piles will impact the overall project costs.
Product Sales and Information Please Contact:
John Burnett
Data Cell Systems, Inc.
308 Woodland Drive, LaPlace, LA 70068
Office: (985) 651-7001 Fax: (985) 651-7009
John Burnett Cell Phone# (985) 855-0739
CHPP - INFO REV.1 8/22/2005 HTF Distributors, LLC.
www.data-cell.com
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