PART I -
GENERAL
Scope:
This section covers compaction with
Sand/Cement/Flyash grout including the installation of injection pipes.
General:
The responsibilities of the Contractor
include project control, supervision, labor, materials and equipment to
accomplish the following items of work:
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Submit a detailed grouting plan to
the Owner or Owners representative for review prior to beginning of
work.
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Install Grout Pipes
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Monitor ground and existing structure
movements during grouting operations.
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Perform grouting program under the
supervision of personnel experienced in grouting for settlement
control.
Quality Control:
Quality control shall be the
responsibility of the grouting Contractor. Due to the specialized nature
of the grouting operation required to perform the specified
stabilization, proposals will only be accepted from pre-qualified
grouting Contractors. To apply for pre-qualification, the grouting
Contractor shall submit a list of compaction grouting projects
undertaken in the past five years. At least three of the grouting
projects specified shall be of equivalent difficulty and/or scope. No
Contractor will be considered acceptable without a minimum of five years
experience in compaction grouting.
Cylinders must be taken by the Contractor
daily or when the mix design changes. Cylinders shall be 3" x
6". Three cylinders shall be taken and marked with the date and
time of day taken. Cylinders shall be broken at 7 and 28 days with the
remaining cylinder being held. A testing laboratory certified by the
Owner shall test cylinders.
The work plan must be submitted to the
Owner for review and comments a minimum of 5 calendar days prior to
commencement of work in the field. The work-plan shall contain the
following:
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The proposed mix design.
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Hole layout and spacing
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System used to monitor movement of
surface or structures.
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Estimate of the duration of the
work time in the field.
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Grout pump manufacturer, model
number and pressure capacities.
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Refusal criteria.
The intent of the grouting is to produce
a 15% improvement in the density of the base material within the limits
shown on the drawing.
The location of the compaction grouting
is shown on the drawings.
The subsurface investigation report and
soil samples obtained during the subsurface investigation may be
examined by contacting the Owner, a minimum of two days in advance of
the day of examination.
Part 2-
PRODUCTS
Equipment:
The equipment used to mix and pump grout
shall be specifically designed for this purposed. Because of the high
pressure involved all equipment, including hoses, couplings, gauges and
pipes, shall be able to operate to the maximum requirements stated in
these specifications. The mixing and grout pump system shall be designed
to provide continuous flow of the grout mixture without interruption
during any single hookup for a specific stage due to inadequate batching
or pump feed capacity.
Grout mixing system:
The grout mixing system shall be capable of thoroughly mixing grout
over the specified range. Grout shall either be supplied by transit
mix or mixed on site. For each batch of transit mixed grout, a ticket
shall be issued by the mix plant stating the amount of Sand, Cement,
Flyash, Water any additives, the time mixed, amount of water added at
the site, time the truck has fully discharged. Any grout over 3 hours
old shall be wasted unless it can be demonstrated that extended hold
time has no detrimental effect. On site mixing systems shall be
capable of precisely measuring, recording, and mixing all materials.
Grout Pump System:
The grout pump shall include a positive displacement type pump with
variable speed capabilities. The grout pump shall have the capability
of injecting grout at a pressure of 800 psi. The pump shall have a
minimum capacity of .05 cfm and maximum of up to 5 cfm. Pumps shall be
equipped with remote controls for operation in vicinity of the probe
collar to control the injection process.
Grout Delivery System.
The grout delivery system shall consist of hoses, couplings, and pipes
compatible with the equipment used for this work and shall be capable
of withstanding the pressures delivered by the pump. Pressure gauges
shall be provided at the pump discharge and at the top of the
injection pipe to monitor pressure.
Pressure Gauges.
All pressure gauges shall be adequately protected form the grout with
suitable gauge savers to provide accurate pressure reading on a
continuous basis and shall be calibrated to a Master Gauge prior to
use.
Grout Injection Volume
measurement System. There shall be a reliable
mechanical means of measuring the quantity of grout pumped in every
stage to within 0.25 cf.
Materials:
Sand:
Sand shall conform to ASTM C-33
Cement.
Cement (if used) shall be Type I or Type II Portland and free of
contamination. Cement shall be either supplied in water resistant
paper bags or in bulk. Cement containing lumps shall be rejected or
screened to remove lumps.
Flyash. Flyash
(if used) shall conform to ASTM C-618 and be either Class C or Class
F.
Lime.
Lime (if used) shall be hydrated agricultural lime. Lime shall be
supplied in water resistant paper bags or in bulk. Lime containing
lumps shall be rejected or screened to remove lumps.
Water.
Water shall be clean and free from contamination. Volume shall be as
necessary to achieve the desired slump.
Admixtures.
Admixtures such as a superplastizer or a pumping aid may be added to
increase set time or improve pumpability.
PART 3 -
EXECUTION
Grout Pipe Installation:
The grout pipes shall be installed
utilizing the primary and secondary sequence. The adjacent primary grout
pipes shall be grouted prior to installing or injection into the
secondary pipes. The Secondary pipes shall be used to verify the
densification of the soil strata.
The pipes shall be either drilled or
driven. The end of the pipe must be sealed to prevent strata from
entering the pipe during installation. The injection pipes shall be
installed to prevent grout leakage and/or premature upward movement of
the casing during injection of high-pressure compaction grout.
Pipes shall be steel of sufficient
diameter and wall thickness to allow the grout to be placed over the
range of slumps and to the pressures as specified.
Grout Injection:
Grout shall be mixed on site or provided
from a transit mix grout truck. The slump of the mix shall not exceed 3
inches. Grout shall be injected at a rate not to exceed 4.0 cfm unless
authorized by the Owner.
Grouting pressure shall be continuously
monitored at the surface connection to the injection pipe with a
suitable protected gauge. A grid pattern for primary injection pipes
shall be established and the grout shall be injected beginning at the
lower depth of the grouting limits as shown on the plans.
The grouting process shall progress in
stages within each injection pipe using the bottom up method. The bottom
up method stages start at the bottom of the grouting pipe, at least 1 ft
into the underlying dense material, progressing upward at 2 ft maximum
intervals. The ground surface and adjacent structures shall be monitored
at all times during grout injection for surface movement (heave).
Pre-established monitor points on any structure shall be monitored
during grout injection.. Grout injection shall cease for any given stage
when movement is detected or when maximum injection pressure is reached
or when a sudden drop in pressure is noted. Pressure shall drop when the
injection pipe is raised or the pipe will be considered plugged and
shall be removed and reinstalled or cleaned out by a wash hose from the
surface.
After completion of primary grouting, a
secondary grid pattern, split spacing the first grid pattern injection
points, shall be established. Grouting in secondary holes shall proceed
as described for primary holes. Quantities for the secondary stage shall
be compared with grout injected during the primary stage to ensure the
subsurface material is becoming densified. The Owner shall be notified
of the quantities placed in the secondary holes before further split
spacing or an area is determined complete.
The compaction grout pumping rates and
pressures shall be carefully controlled.
Any hole lost due to Contractor
negligence or error shall be replaced at not charge to the Owner.
Testing and Quality Control. The
Contractor shall pay the cost of sampling and testing.
All daily drilling, grouting and testing
reports shall be submitted to the Owner within 24 hours. A level control
system will be installed and operated by the Contractor for use during
grouting. Changes in elevation of the control points shall be tabulated
and submitted to Owner at the completion of the project.
Drilling reports shall contain at least
the following information: Name of driller, type of drill, method used,
date, location of hole, tip depth or elevation of injection pipe.
Grouting reports shall contain at least
the following information: Name of grouting technician, grout mix,
quantity injected per stage, date, rate of pumping, beginning and final
pressure obtained in each stage. The reason for refusal, such as refusal
pressure, movement of the surface, movement of a structure.
Protection or Work Area
and Cleanup:
During the work operations the Contractor
shall take such precautions as may be necessary to permit drill
cuttings, equipment exhaust, oil, wash water and grout from defacing
and/or damaging the surrounding area.
The Contractor shall furnish such pumps
as may be necessary to care for wastewater and grout from his operations
and shall clean up all waste resulting from his operations.
Measurement and Payment:
Mobilization/Demobilization will be
measured as lump sum. Eighty percent will be paid when all equipment is
on site. The remaining twenty percent will be paid after all equipment
is removed from site, the site is restored, and all reports, including
drilling, grouting, and elevations, are received by the Owner.
Injection pipes shall be measured by each
pipe installed to the depth indicated on the Plans. Payment will be made
for each pipe successfully installed. Pipes that become plugged shall be
removed and replaced at no charge to the Owner.
Grout shall be measured by the Cubic Yard
successfully placed. Grout shall be paid for by the Cubic Yard
successfully placed.
Grout wasted at the direction of the
Owner as a result of grout hole refusal will be paid at the cost
specified. Measurement and payment will be made by the cubic yard.
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Item #
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Item Unit
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Mobilization
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ls
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Injection Pipes Installed
|
ea
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Grout Placed
|
cy
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Grout Wasted
|
cy
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