HomeMy WebLinkAbout31-3400-Aggregate-Piers_Rev_1Dennis Yarmouth Middle School
Dennis Yarmouth Regional District
Perkins Eastman DPC, #71011
January 19, 2021
100% Construction Documents
31 3400 Aggregate Piers
1 of 10
31 3400 - AGGREGATE PIERS
PART 1 – GENERAL
1.0 DESCRIPTION:
A. Work should consist of designing, furnishing and installing aggregate pier
ground improvement to the lines and grades designated on the foundation plan
and as specified herein. Ground improvement is to be installed below footings,
slabs, stairways, and other ancillary structures as indicated on the drawings.
B. Aggregate pier ground improvement as referenced in this specification should be
constructed by either vibro-piers or vibro stone columns (vibro-compaction) or
Rammed Aggregate Pier systems. Other aggregate pier installation systems
provided by other installers can be taken in review by the Contractor with
approval by the Geotechnical Engineer.
C. The aggregate piers should be constructed foot by foot as an aggregate column
to be used in ground improvement capable of supporting structural units:
concrete grade slab, wall and column footing loads.
1.1 WORK INCLUDED:
A. Provision of all equipment, material, labor, engineering and supervision to design
and install aggregate piers. Design should rely upon subsurface information
presented in the project geotechnical report. Footing excavation, subgrade
preparation and load transfer platform installation following aggregate pier
installation is not included.
B. The aggregate pier design and installation should utilize the methods and
standards presented in this specification as minimum guidelines.
C. Some procedures and tests given may be appropriate for displacement systems
such as geopiers and not appropriate for non-displacement systems such as
commonly installed by Hayward Baker and HB Fleming. Alternate testing or
field observation can be offered by the aggregate pier installer in those cases.
1.2 RELATED INFORMATION:
A. Site geotechnical information provided by the project geotechnical engineering
firm, Geotechnical Partnership, Inc. of Swampscott, MA:. “Design Phase
Geotechnical Report Proposed Dennis-Yarmouth Intermediate School 296
Station Avenue South Yarmouth, Massachusetts” dated 18 February 2020.
B. Drawings and General Provisions of the Contract, including General and
Supplemental Conditions, and Division 1 Specifications, apply to the work in this
specification.
C. Refer also to related specification sections relevant to earthwork or earth moving,
construction dewatering and excavation support and protection as applicable.
Dennis Yarmouth Middle School
Dennis Yarmouth Regional District
Perkins Eastman DPC, #71011
January 19, 2021
100% Construction Documents
31 3400 Aggregate Piers
2 of 10
1.3 APPROVED INSTALLERS:
A. Potential aggregate pier installers should be approved by the Geotechnical
Engineer prior to bid opening.
B. Installers of aggregate pier ground improvement systems should have a
minimum of 3 years of installation experience and completed at least 15 projects.
C. As presently understood the following specialty firms would be considered
acceptable project bidders: Geopier, Hayward Baker, Subsurface
Constructors and HB Fleming.
1.4 REFERENCE STANDARDS:
A. Aggregate pier design:
1. “Control of Settlement and Uplift of Structures Using Short Aggregate
Piers,” by Evert C. Lawton (Assoc. Prof. Dept. of Civil Eng., Univ. of
Utah), Nathaniel S. Fox (President, Geopier Foundation Co., Inc.), and
Richard L. Handy (Distinguished Prof. Emeritus, Iowa State Univ.,
Dep’t. of Civil Eng.), reprinted from IN-SITU DEEP SOIL IMPROVE-
MENT, Proceedings of sessions sponsored by the Geotechnical
Engineering Division/ASCE in conjunction with the ASCE National
Convention held October 9-13, 1994, Atlanta, Georgia.
2. “Settlement of Structures Supported on Marginal or Inadequate Soils
Stiffened with Short Aggregate Piers,” by Evert C. Lawton and
Nathaniel S. Fox. Geotechnical Special Publication No. 40: Vertical and
Horizontal Deformations of Foundations and Embankments, ASCE, 2,
962-974.
3. “The Design of Vibro Replacement,” H.J. Priebe. Ground Engineering;
London; December 1995.
4. Ground Improvement (3rd Ed.), edited by Klaus Kirsch and Alan Bell.
CRC Press; 2013
B. Load (Modulus) Testing:
1. ASTM D 1143 – Pile Load Test Procedures
2. ASTM D 1194 – Spread Footing Load Test
C. Materials and Inspection:
1. ASTM D 1241 – Aggregate Quality
2. ASTM D 422 – Gradation of Soils
1.5 SUBMITTALS:
A. All design calculations and plans submitted should be stamped by a
Massachusetts licensed Professional Engineer.
B. Professional liability insurance: the aggregate pier designer should have
Errors and Omissions design insurance for the work. The insurance policy
should have a minimum coverage of $1 million per occurrence.
C. The submitted aggregate pier design should be in accordance with the current
version of the Massachusetts State Building Code including addenda.
Dennis Yarmouth Middle School
Dennis Yarmouth Regional District
Perkins Eastman DPC, #71011
January 19, 2021
100% Construction Documents
31 3400 Aggregate Piers
3 of 10
D. The following aggregate pier design information is to be provided to the
Geotechnical Engineer and the Structural Engineer for review in advance of
installer mobilization on-site:
1. Aggregate pier design calculations [individual ungrouted pier allowable
capacity (min. = 50 kips), improved ground net allowable soil bearing
pressure (min. = 4 kips per square foot), pier lengths, pier diameter, and
settlement of footings and lowest level slabs (total settlement ≤ 1 in.;
differential settlement between adjacent footings ≤ ½ in.)] for:
a. Piers supporting footings (wall and column)
b. Lowest level concrete slab(s)
c. Special features (elevators, ramps, exterior walls)
d. Uplift piers [if required by the Structural Engineer]
2. Aggregate piers can be designed to higher allowable capacities than
given above provided final design calculations provide confirmation of
the values selected.
3. An aggregate pier design layout plan superimposed upon the building
foundation plan showing footings and slabs as provided by the Structural
Engineer.
4. Illustrative aggregate pier layout plan installation notes and pier sections
relevant to support of footings, concrete floor slabs, and special features.
E. Daily aggregate pier progress reporting: the installer should furnish a complete
and accurate record of daily aggregate pier installation to the Geotechnical
Engineer’s on-site quality assurance representative. The record should include
pier location, installed length, built pier aggregate volume and diameter and
pier top elevation. Any unusual conditions encountered during installation should
be reported.
F. Installation equipment: the type and size (capability) of aggregate pier
installation equipment to be utilized should be provided.
1.6 GENERAL SEQUENCE OF WORK:
A. Anticipate the following sequence of construction:
1. Installation of work area equipment support and protection.
2. Excavation to an acceptably level, compacted working base elevation.
3. Survey for pier layout.
4. Possible pier pre-drilling or spudding if obstructions are found.
5. Aggregate pier installation to proceed from within the working base.
1.7 SITE PREPARATION:
A. General Contractor responsibilities:
1. Remove any observed existing pavement, sidewalk, buried foundations,
utilities and solid waste at exposed working base level.
2. Provide acceptably level compacted working base work area
3. Provide working base in such condition that the aggregate pier
installation work can proceed in-the-dry.
4. Provide a source of potable water during aggregate pier installation to
help keep aggregate stone dust levels down and also, if grouted piers
are called for in the design (grouted piers are not expected on this
project).
Dennis Yarmouth Middle School
Dennis Yarmouth Regional District
Perkins Eastman DPC, #71011
January 19, 2021
100% Construction Documents
31 3400 Aggregate Piers
4 of 10
5. Clearly mark and verify all existing utilities in and adjacent to the work
area (including decommissioned ones).
6. Share utility data with the aggregate pier installer prior to aggregate pier
installation start-up.
1.8 AGGREGATE PIER SURVEY LAYOUT AND PIER INSTALLATION LOCATION:
A. General Contractor is required to provide field location of each aggregate pier by
both flagging and whisker pin.
B. Clearly number all flags at all design aggregate pier locations as determined by
the project aggregate pier location plan.
C. Flags and whisker pins lost or destroyed during the aggregate pier installation
period must be re-installed and re-marked by the General Contractor.
D. Aggregate piers must be installed by the pier installation contractor within six (6)
inches of plan locations.
E. The Architect and Structural Engineer should note that it is possible that some
initial foundation footing plan dimensions may need to be increased from that
shown on the original foundation plan to be able to encompass the number and
spacing of aggregate piers required to be installed at a given location.
1.9 OBSTRUCTIONS:
A. Aggregate pier installer responsibility:
1. Aggregate pier installer must make a reasonable attempt to drive through
an encountered obstruction either utilizing:
a. Maximum and sustained crowd pressure on the aggregate pier
mandrel or probe; or
b. Augering or use of a spudding tool down-hole.
B. If aggregate pier installer efforts to drive through an obstruction are unsuccessful
the General Contractor must:
1. Provide personnel and equipment to remove encountered obstructions.
2. Backfill as necessary to level grade with like materials or appropriate
engineered fill as determined by the system designer.
3. Loosen tight, isolated surficial ground areas.
C. Added (initially unplanned) aggregate piers may be required to bridge found
underground utility locations traversing the area of work or obstructions.
1.10 REQUIRED FIELD TESTING:
A. The aggregate pier installer must provide all personnel and equipment necessary
to undertake the required testing during installation.
B. Aggregate pier soil modulus compression test:
1. Test should be performed in general accordance with ASTM D1143 (pile
load testing) with modifications as given by the installer’s shop
drawings and accepted by the Geotechnical and Structural Engineers.
Dennis Yarmouth Middle School
Dennis Yarmouth Regional District
Perkins Eastman DPC, #71011
January 19, 2021
100% Construction Documents
31 3400 Aggregate Piers
5 of 10
2. Purpose of the test is to verify the values of pier and soil modulus used in
project design.
3. Location of test: a non-production aggregate pier installed near the
deepest and/or weakest portion of the subsoil profile to be improved
determined by the designer and the Geotechnical Engineer.
4. Test set-up: as given on the installer’s shop drawings to be submitted for
review by the Geotechnical Engineer.
5. Shop drawings should clearly show:
a. Standard for top of installed pier surface (e.g. circular concrete
bearing pad of equal diameter).
b. Hold-down: by uplift piers, helical piles, or other methods
c. Two sleeved tell tale rods at base of pier to measure bottom
movement.
d. Reference beam and dial gauges (3 top; 2 tell tale).
5. Load jack and jack calibration sheet should likewise be submitted to the
Geotechnical Engineer prior to testing.
6. Design Stress (DS): as given in the installer’s submittal as reviewed and
approved by the Geotechnical Engineer and adjusted to actual installed
pier diameter (as determined from pier installation by on-site aggregate
volume calculations).
7. Perform base compression (stabilization) test (proof level; see below)
during test pier formation for use as a measurement reference standard
for production aggregate piers. [Vibro-piers and vibro stone columns may
suggest alternatives; e.g. pre-augered shaft hole depth measurement
and visual inspection]
8. Modulus test loads:
a. Load increments, at approx. 17% DS each at 15 min. hold each.
b. Hold load:
i. 1 hour at 117% DS (top deflection < 0.01 in. / hour ).
ii. Hold load to max. = 4 hr., if needed.
c. Maximum test load: 150% DS;
d. Rebound loads: approx. 33% DS at 5 min. hold each.
9. Design values from modulus test, as applicable:
a. Revised Design Stress: top of pier stress inflection point on
stress-deflection curve from modulus test.
b. Revised Design Load = Revised Design Stress / Pier Area
(requires diameter calculation from installation stone volumes
(e.g. spoil cone, pier shaft)).
10. Telltale deflection during the test should be ≤ 20% of measured top
deflection.
C. Aggregate pier base compression (stabilization) tests [vibro-pier and vibro stone
columns suggest use of alternate]:
1. Test to be performed on pier base bulb or on the pier shaft within
the bottom ⅓ of design shaft length.
2. Apply static crowd (downward vertical) pressure with mandrel system or
probe (with vibratory hammer off) to the top of the last 1 foot lift
compacted:
a. Pre-determined crowd pressure (measured in atmospheres); or
b. 75% of value determined from soil modulus test
3. Test duration and frequency:
a. 1 minute (performance level) on 15% of production piers
Dennis Yarmouth Middle School
Dennis Yarmouth Regional District
Perkins Eastman DPC, #71011
January 19, 2021
100% Construction Documents
31 3400 Aggregate Piers
6 of 10
b. 3 minutes (proof level) on at least the 1st 6 piers installed on-site
4. Acceptable measured movement of mandrel shaft with respect to ground
reference device during testing:
a. < approx. 1 in.; or
b. ≤ (1.5) x (mandrel movement measured during proof level base
compression test as part of modulus test procedure).
D. Pier shaft diameter determination:
1. Measured from stone volumes utilized and calculated:
a. To construct the pier shaft; and
b. In the remaining stone cone above the top of shaft upon
aggregate pier completion.
2. Pier shaft diameter must be ≥ twenty (20) inches for displacement piers
and ≥ 30 inches for non-displacement piers in all cases.
E. Uplift Test: to be specified separately if uplift piers are required for this project.
ASTM D-3687 will be used to determine loads, durations and unloads.
PART 2 – MATERIALS
2.1 AGGREGATE PIERS:
A. Aggregate utilized for this project: ¾ in. clean, open-graded, hard durable
crushed stone (particularly appropriate for aggregate piers requiring grouting or
expected to be in groundwater):
1. Type I, Gradation B with less than 5% passing No. 40 sieve, less than
2% passing No. 200 sieve. (ASTM D-1241-68 with given modifications);
or
2. No. 57 stone with less than 5% passing No. 40 sieve, less than 2%
passing No. 200 sieve; or
3. Other stone mix selected by the installer (designer) with less than 5%
passing No. 40 sieve, less than 2% passing No. 200 sieve which
successfully is used in the modulus test.
B. Aggregate piers used on this project are expected to be ungrouted. No
grouted piers are anticipated. Aggregate mix specified can vary from those given
above with approval of the Geotechnical Engineer.
2.2 GROUT:
A. Subsurface conditions at the new building locations do not require grouted piers.
B. Cement for grouted piers: Type I Portland Cement
C. Potable water: e.g. about 3 gallons per linear foot of grout or 0.4 CF grout per
linear foot of 20 in. nom. dia. pier installed.
D. Grout used by the installer should be pre-approved by the system designer.
PART 3 - INSTALLATION:
3.1 PIER EMBEDMENT:
Dennis Yarmouth Middle School
Dennis Yarmouth Regional District
Perkins Eastman DPC, #71011
January 19, 2021
100% Construction Documents
31 3400 Aggregate Piers
7 of 10
A. Required pier base bulb formation embedment depth into top of medium dense
clean glacial sand soil layers (refer to the geotechnical report, particularly the
boring logs and Figure 4A, Figure 4B and Figure 4C of the geotechnical report):
1. Maximum embedment: up to 5 ft., unless otherwise specified
2. Minimum embedment = 3 ft., unless otherwise specified
3. No embedment = where bedrock is encountered (see logs of borings)
3.2 PIER DIMENSIONS:
A. Individual required design aggregate pier lengths:
1. As estimated from subsurface data and given in the installer’s submittal
as approved by the Geotechnical Engineer. Soil layers (refer to
geotechnical reports, particularly boring logs, subsoil profiles and
soil layer summary tables.
2. As adjusted on-site during installation based upon observed mandrel or
probe behavior during aggregate pier installation.
B. Nominal pier diameter is twenty (20) inches for displacement piers and 30 inches
for non-displaement piers. Installed compacted shaft diameter can be greater in
practice.
C. Pier installer is responsible for installation of the piers to the diameters, depths
and manner (grouted, ungrouted) required in the project design.
3.3 PIER INSTALLATION:
A. Pull-push:
1. For displacement piers utilize proper mandrel pull-push ratio to build the pier
in 1 foot compacted lifts to at least the nominal diameter;
2. For non-displacement piers (vibro-piers, vibro compacted columns) probes
should not be withdrawn more than 2 feet after penetration to the required
depth with redriving in to the treated depth at approximately 12 to 18 inch
intervals to observe resistance to penetration and amperage build up. During
re-driving, the probe tip shall penetrate to within 1 foot of the previous re-
driving depth. Built pier diameters should at least equal the nominal
diameter.
B. Crowd pressure (stress) on the pier base during base construction should:
1. Conform to installer submittal and associated review by the Geotechnical
Engineer.
2. Approach the design value from modulus test (if less than design
submittal determination).
PART 4 – QUALITY ASSURANCE DURING PIER INSTALLATION AND FOLLOW-ON
EARTHWORK RELEVANT TO AGGREGATE PIERS
4.1 QUALITY ASSURANCE:
A. Geotechnical Engineer or Testing Agency should provide on-site Quality
Assurance services as geotechnical consulting during aggregate pier installation
to verify:
1. Installed length, compaction and diameter of each aggregate pier.
2. Soil modulus test results.
3. On-going base compression proof and performance test results.
Dennis Yarmouth Middle School
Dennis Yarmouth Regional District
Perkins Eastman DPC, #71011
January 19, 2021
100% Construction Documents
31 3400 Aggregate Piers
8 of 10
4. Vibration monitoring:
a. Seismograph recording of vibrations at nearest structure(s) to
the individual installed pier should be provided.
b. Duration of monitoring should at minimum be the first 3 days of
installation. Longer monitoring can be required if it is decided by
the Architect that additional monitoring is warranted due to
sensitivity of adjacent structures or neighbors.
c. In no case should a peak particle velocity of 0.5 inches per
second be exceeded during an individual pier installation.
If it is the vibratory hammer should be adjusted so that this value
is not exceeded.
d. If neighborhood sensitivity to installation occurs even with a
0.5 inches per second limit, this limit should be reduced on-site
as necessary until a reasonable vibration level in terms of
neighborhood sensitivity is reached. 0.3 inches per second is
frequently utilized in this case.
B Daily or interval summary field reports should be provided.
C. Geotechnical Engineer or Testing Agency should provide on-site quality
assurance services during foundation footing excavation, slab base preparation
and construction of any required load transfer platforms below footings.
1. In particular the Geotechnical Engineer or Testing Agency will verify
proper treatment of tops of installed aggregate piers during earthwork.
Review and document placement of load transfer platforms if included in
design. Daily field or interval summary reports will be provided.
2. To aid in the pier installer’s ability to bond/guarantee the installed
aggregate piers and improved subsoils the Geotechnical Engineer or
Testing Agency will provide a general Quality Assurance summary letter
to the pier company summarizing the observed aggregate pier
installation and subsequent structural unit related earthwork.
4.2 GENERAL CONTRACTOR RESPONSIBILITIES:
A. Avoid pier prepared area loading by use of construction equipment or by material
stockpiling until all aggregate piers have been installed.
B. Provide positive drainage to protect the site from wet weather and surface
ponding of water both during and following aggregate pier installation.
C. If early installation of footings is to be undertaken:
1. Determine appropriate lateral separation of foundation work from the
aggregate pier installation work with the pier installer in advance of start-
up (vibration issue for Geopiers; vibration not an issue for non-
displacement piers (vibro-piers and vibro stone columns)).
2. In particular determine proper lateral separation of any construction
dewatering equipment (sumps, well points) from grouted aggregate pier
installation and areas of any installed grouted piers undergoing curing.
D. Allow set-up time for any grouted aggregate piers underground as required by
the pier installer before re-commencing normal site construction activities.
E. Concrete slab support aggregate piers:
Dennis Yarmouth Middle School
Dennis Yarmouth Regional District
Perkins Eastman DPC, #71011
January 19, 2021
100% Construction Documents
31 3400 Aggregate Piers
9 of 10
1. Place a minimum 12 inch thick layer of engineered fill (crushed stone or
structural fill) over the slab pier installation area to protect the installed
aggregate pier tops and provide a slab cushion:
a. Compact the exposed pier tops prior to placing the fill layer.
b. Grade fill layer so as to prevent surface water ponding.
c. Compact.
2. Avoid excavation next to a pier within a 1H:1V zone as measured from
the top of the adjacent pier. Remediation of a damaged or undermined
pier by such excavation shall be required in consultation with the pier
installer. No charge to the Owner for the remedial work shall occur.
F. Footing support aggregate piers:
1. Undertake footing excavations with an excavator equipped with a bucket
blade or a smooth-edged bucket.
2. Excavation depth: design footing embedment plus load transfer platform
(or surface backfill) height (thickness).
3. Tops of exposed excavated footing piers and adjacent soils must be
thoroughly compacted prior to placement of the load transfer platform
elements.
4. Avoid accumulation of standing water in the excavation.
5. Avoid excavation next to a pier within a 1H:1V zone as measured from
the top of the adjacent pier. Remediation of such excavation shall be
required in consultation with the installer and shall incur no charge to the
Owner.
6. Construction of any load transfer platform should be undertaken upon
the compacted, dewatered, excavated base at each footing location as
follows:
i. Materials: as approved by the installer’s designer
1. Geotextiles such as geogrids and structural fabrics (e.g.
Mirafi 140N)
2. Aggregate: clean ¾ in. crushed stone with <10% passing
the #4 sieve and <8% passing the #50
ii. Place the structural fabric on the prepared subgrade to the limits
shown on the installer’s plan.
iii. Place a lift of aggregate and thoroughly compact. Lift thickness to be
determined as part of the installer’s system design.
iv. If indicated by the installer’s load transfer platform design place a
layer of geogrid. This would then be followed by placement and
compaction of another layer of aggregate.
v. The base structural fabric previously placed would then be wrapped
up the sides of the excavation to terminate on top of the load transfer
platform and beneath the physical design limits of the individual
footing.
7. Water can not be allowed to accumulate in footing excavations.
Appropriate excavation dewatering equipment should be on-site and in
working condition in advance of excavation work.
8. All aspects of excavation, subgrade preparation and load transfer
platform installation should be observed and documented by the
Geotechnical Engineer or Testing Agency.
G. Establish a mutually agreeable soil removal and replacement protocol with the
installer should weak cohesive soil such as loam, peat or organic silt or other
readily compressible material be found at footing or lowest level slab or elevator
pit slab bearing depth.
Dennis Yarmouth Middle School
Dennis Yarmouth Regional District
Perkins Eastman DPC, #71011
January 19, 2021
100% Construction Documents
31 3400 Aggregate Piers
10 of 10
H. Spoil generated from non-displacement pier augering is expected to range from
1 cu. yd. to 2 cu. yd. per installed pier. Disposition of this spoil material should
be part of the General Contractor’s site earthwork planning.
END OF SECTION 31 3400