S-12-0004 Attachment1B_Desert View_Retaining Wall Design_Technical Scope of Work.pdf

Section J - Retaining Wall Design

Technical Scope of Work

SECTION 1: GENERAL TECHNICAL NOTES FOR

DRILLED SHAFT/SOLDIER PILE AND MSE

RETAINING WALL

1.01 Description:

The work shall consist of furnishing and constructing drilled shaft, soldier pile retaining walls, mechanically stabilized earth retaining wall systems, and installing tieback anchors in accordance with this technical scope of work and in reasonably close conformity with the lines, grades, and dimensions shown on the Richards, Sorensen grading plans, undated and on sheets C-602 through C-

610.

1.02 Work Included:

A. Construction of drilled shafts and soldier pile retaining wall systems in accordance with the construction sequencing shown on the construction plans.

B. Excavating drilled shafts and placement of steel soldier piles and placement of concrete in portions of the retaining wall below grade as specified herein and as shown on the construction drawings.

C. Placement of treated wood lagging, installation of weep holes, and placement of drainage materials as part of subsurface drainage systems as shown on the construction drawings.

D. Placing, moisture conditioning and compaction of wall backfill.

E. Excavating and drilling tie-back anchor drill holes as specified herein and as shown on the construction drawings.

F. Furnishing, placing and grouting anchor bar tendons into drill holes.

G. Furnishing structural geogrid reinforcement and geotextiles as shown on the construction drawings.

B. Furnishing segmental block units and geotextiles as shown on the construction drawings.

C. Storing, cutting and placing structural geogrid reinforcement as specified herein and as shown on the

H. Furnishing, placing and compacting suitable backfill material as specified herein and as shown on the

1.03 Reference Documents:

A. American Association of State Highway and

Transportation Officials (AASHTO):

M-85 Standard Specification for Portland Cement.

M-288 Standard Specification for Geotextiles

T-99 Moisture-Density Relations of Soils Using a

5.5 Pound Rammer in a 12-inch Drop.

T-180 Moisture-Density Relations of Soils Using a

10 Pound Rammer in a 18-inch Drop.

T-289 Determining pH of Soil for Use in Corrosion

Testing

B. American Society for Testing and Materials Standards

(ASTM):

A53 / A53M-07 Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-Coated, Welded and Seamless

A-82 / A-82M Standard Specification for Steel Wire, Plain, for Concrete Reinforcement

A-123 / A-123M Standard Specification for Zinc

(Hot Dip Galvanized) Coatings on Iron and

Steel Products

A500/A500M-09 Standard Specification for Cold-

Formed Welded and Seamless Carbon Steel

Structural Tubing in Rounds and Shapes

A615/A615M-09b Standard Specification for

Deformed and Plain Carbon-Steel Bars for

Concrete Reinforcement

A775/A775M-07b Standard Specification for Epoxy-

Coated Steel Reinforcing Bars

A992/A992M-06a Standard Specification for

Structural Steel Shapes

C-33 Specification for Concrete Aggregates

C-94 Specification for Ready-Mixed Concrete

C-109 Test Method for Compressive Strength of

Hydraulic Cement Mortars

C-140 Methods of Sampling and Testing Concrete

Masonry Units

C-150 Specification for Portland Cement

C-231 Test Method for Air Content of Freshly

Mixed Concrete by Pressure Method

C-260 Specification for Air-Entraining Admixtures for Concrete

C-494 Specification for Chemical Admixtures for

Concrete

C-595 Specification for Blended Hydraulic Cements

C-618 Specification for Coal Fly Ash and Raw or

Calcined Natural Pozzolan for Use as an

Admixture in Portland Cement Concrete

C-642 Test Method for Specific Gravity, Absorption, and Voids in Hardened Concrete

C-685 Specification for Concrete Made by

Volumetric Batching and Continuous Mixing

C-1372 Standard Specifications of Segmental

Retaining Wall Units

D-698 Method for Laboratory Compaction

Characteristics of Soils Using Standard Effort

D-732 Shear Strength of Plastic by the Punch Tool

Method

D-790 Flexural Properties Testing of Plastic

C-1240 Specification for Silica Fume for Use in

Hydraulic Cement Concrete and Mortar

D-422 Method for Particle Size Analysis of Soils

D1248-05 Standard Specification for Polyethylene

Plastics Extrusion Materials For Wire and

Cable

D-1557 Method for Laboratory Compaction

Characteristics of Soils Using Modified Effort

D-1556 Method for Density and Unit Weight of Soil in-Place by the Sand Cone Method

D-1785 Specification for Rigid Poly (Vinyl

Chloride)(PVC) Plastic Pipe, Schedules 40, 80, and 120

D-2922 Methods for Density of Soil and Soil-

Aggregate In Place by Nuclear Methods

D-3785 Standard Performance Specification for

Woven Necktie and Scarf Fabrics

D-3966 Method of Testing Piles under Lateral Load

D-4101 Standard Specification for Propylene Plastic

Injection and Extrusion Materials

D-4253 Methods for Maximum Index Density and

Unit Weight of Soils Using a Vibratory Table

D-4254 Methods for Minimum Index Density and

Unit Weight of Soils and Calculation of

Relative Density.

D-4595 Tensile Properties of Geotextiles by The

Wide-Width Strip Method

D-4632 Standard Test Method for Grab Breaking

Load and Elongation of Geotextiles

D4833 Standard Test Method for Index Puncture

Resistance of Geomembranes and Related

Products

D-6637 Standard Test Method for Determining

Tensile Properties of Geogrids by the Single or Multi-Rib Tensile Method

D-6706 Standard Test Method for Measuring

Geosynthetic Pullout Resistance in Soil

C. Nevada Department of Transportation (NDOT) –

Standard Specifications for Road and Bridge

Construction, 2001

D. Federal Highway Administration (FHWA)

FHWA-NHI-00-043 FHWA Mechanically Stabilized

Earth Walls and Reinforced Soil Slopes Design and Construction Guidelines, March 2001

FHWA-IF-99-015 Geotechnical Engineering Circular

No. 4, Ground Anchors and Anchored

Systems, June 1999.

E. AASHTO – Standard Specifications for Highway

Bridges, 17 th Edition, 2002.

F. Caldwell, Richards, Sorensen, Grading Plans, undated.

G. Terracon Consultants, Inc., Geotechnical Engineering

Report, Desert View Overlook Rehabilitation –

Retaining Wall and Parking Area, Project No.

64085048, dated January 8, 2010.

H. Where specifications and reference documents conflict, the Engineer shall make final determination of the applicable document.

I. Terracon has completed engineering design of the proposed retaining walls based upon the information provided to us as outlined above.

1.04 Special Provisions:

A. The designs presented herein are based on wall profile, soil parameters, foundations conditions and loadings stated in documentation as outlined in

Section 1.03, Items F and G, and Section 4.01.

B. The contractor shall be responsible for the cost of all means of subsoil improvement; cost of additional subsoil exploration; and for all labor tools, equipment and incidentals necessary to complete the work.

C. The contractor shall be responsible for complying with all federal, state and local requirements for execution of the work, including local building inspection and current OSHA excavation regulations.

D. Prior to undertaking any grading or excavation of the site, the Contractor shall confirm the location of proposed retaining walls, drilled shafts and all underground features, including utility locations within the area of construction.

E. All work undertaken in the construction of the retaining walls is subject to the quality control/assurance and special inspection provisions outlined in Section 3.27.

F. Terracon has completed engineering design of the proposed retaining walls, including internal stability and local external stability where applicable, based upon the information provided to us as outlined above. Any deviations to the design conditions as provided for in the plans and specifications, and as outlined herein, should be brought to the attention of the Terracon for modification of this plans accordingly.

SECTION 2: MATERIALS

2.01 Definitions:

A. Drilled Shaft/Soldier Pile Wall –consisting of a combination of steel reinforced, concrete filled drilled shafts, wood lagging and other materials as indicated on the plans.

B. Steel Piles—steel W sections of the strength, size and weight shown on the plans.

C. Reinforced Concrete Panel Lagging – pre-cast reinforced concrete panel as shown on the structural

D. Anchor Bars - Anchor bars shall be a deformed, epoxy coated Grade 75 steel bar as designated on the drawings, or other approved bar type.

E. Unbonded Anchor Length (Free Stressing Length) -

The design length of the tendon that is not bonded to the surrounding ground or grout during stressing.

F. Bonded Anchor Length - design length of the anchor tendon without bondbreaker which is grouted and so bonded to the surrounding structure or ground.

G. Lock-Off Load - The prestressing force in an anchor immediately after transferring the load from the jack to the stressing anchorage.

H. Bondbreaker – A sleeve placed over the anchor tendon in the unbounded anchor length to ensure unobstructed elongation of the tendon during stressing.

I. Plastic Sheath - A smooth or corrugated pipe or tube protecting the prestressing steel in the unbounded anchor length against corrosion.

J. Trumpet - Device to provide corrosion protection in the transition length from the anchorage to the free stressing length.

K. Epoxy Coating – a fusion bonded electrostatically applied coating.

L. Centralizers – a PVC or steel pipe or tube attached to anchors sized to allow tremie pipe insertion to bottom of the drill hole.

M. Steel End Plates - The center hole diameter within the steel plate shall be 0.2 inches greater that the anchor bar diameter.

N. Washers and Lock-off Nuts - Washers and nuts shall be provided by the anchor bar supplier.

O. Anchor Grout – Neat cement or sand/cement mixture.

P. Subsurface Drain – a combination of drainage composite, geotextiles filter and weep holes to provide for internal drainage behind the wall facing.

Q. Structural Geogrid – a Tensar geogrid formed by a regular network of integrally connected tensile elements with apertures of sufficient size to allow interlocking with surrounding soil, rock, or earth and function primarily as reinforcement.

R. Geotextile – a spun-bound non-woven engineering fabric intended for tensile reinforcement with high filtration and permeability characteristics.

S. Segmental Concrete Facing Units – A Tensar MESA block standard segmental concrete facing, machine made from portland cement, water and mineral aggregates.

T. Cap Unit – a Tensar Mesa segmental concrete cap unit.

U. Unit Fill – granular fill which is within the segmental concrete facing units.

V. Post Foundation System- a 12‖ diameter post fence foundation system, used to facilitate fence/ railing installation.

W. Bedrock - Intact bedrock that is slightly weathered to fresh and having few or no blast induced fractures.

X. Reinforced Backfill – compacted soil which is within the reinforced soil volume as outlined on the plans.

Y. Leveling Pad – a level compacted gravel upon which the first course of segmental concrete facing units are placed.

Z. Foundation Soil – compacted or in-situ soil beneath the entire wall.

AA. Engineer – Terracon Consultants, Inc. (Phoenix)

BB. Geotechnical Engineer – Terracon Consultants, Inc.

(Las Vegas)

2.02 Drilled Shafts:

A. The drilled shafts shall be of the minimum diameter, depths and spacing as shown on the plans.

B. The drilled shafts shall be located at a horizontal center to center distance of seven (7) feet, except if otherwise shown on plans.

C. The drilled shafts shall be continuously reinforced with the steel piles (W-sections) for the entire depth as shown on the plans.

D. All drilled shaft excavations shall be filled with concrete to final grade of the type and strength specified herein.

2.03 Portland Cement Concrete for Drilled Shafts:

A. Portland Cement conforming to NDOT 2001

Standard Specification shall be used.

1. Portland cement concrete shall be Class D having a minimum net compressive strength of 4,000 psi at 28 days of age.

2. Aggregates used shall be normal weight conforming to NDOT Standard Specification.

2.04 Steel Piles:

A. The steel piles shall be ASTM A992 Grade 50, epoxy coated of the size, shape and weight as specified on the plans.

B. The epoxy coating shall be an ASTM A775 fusion bonded electrostatically applied coating.

C. The coating shall be a minimum of 0.016 inches (0.4

mm) in thickness.

2.05 Reinforced Concrete Panel:

A. The reinforced concrete panel shall be as shown on the structural plans.

2.06 Anchor Tendon Bars:

A. The tendons used for tie back anchors shall be ASTM

A615, Grade 75, Number 9 deformed steel bar or as shown on plans.

B. The tendons shall be new, straight, undamaged continuous without splices or welds.

C. The tendons shall be threaded a minimum of 6-inches

(150 mm) on the wall anchorage end to allow proper attachment of steel plate and nut.

D. The threading may be continuous spiral deformed ribbing provided by the bar deformations (continuous threadbars) or may be cut into a reinforcing bar. If threads are cut into a reinforcing bar, provide the next larger bar size from that shown on plans.

2.07 Epoxy Coating:

A. The epoxy coating, when required, shall be an ASTM

A775 fusion bonded electrostatically applied coating

(purple epoxy).

B. The coating shall be a minimum of 0.01 inches (0.3

mm) in thickness.

C. The coating at the wall anchorage end of the epoxy-coated bars may be omitted over the length provided for threading the nut against the bearing plate.

2.08 Trumpet:

A. A Trumpet device shall be installed to provide corrosion protection in the transition length from the anchorage to the free stressing length as shown on

B. The trumpet shall be fabricated from a steel pipe or tube or from PVC pipe.

C. Steel pipe or tube shall conform to the requirements of ASTM A 53 for pipe or ASTM A 500 for tubing.

D. Steel trumpets shall have a minimum wall thickness of 1/8 inch for diameters up to 3 inches and 3/16 inch for larger diameters. PVC pipe shall conform to

ASTM D 1785, Schedule 40 minimum.

E. PVC trumpets shall be positively sealed against the bearing plate and aligned with the tendon to prevent cracking during stressing.

2.09 Bondbreaker:

A. The bondbreaker shall be fabricated from a smooth plastic tube or pipe having the following properties:

1. Resistant to chemical attack from aggressive environments, grout, or corrosion inhibiting compound;

2. Resistant to aging by ultra-violet light;

3. Fabricated from material nondetrimental to the tendon;

4. Capable of withstanding abrasion, impact, and bending during handling and installation;

5. Enable the tendon to elongate during testing and stressing; and

6. Allow the tendon to remain unbonded after lock-off.

2.10 Sheath:

A. A sheath shall be used as part of the corrosion protection system for the unbonded length portion of the tendon.

B. Plastic sheath used in the unbonded length of the anchors shall be 3-inch pipe.

C. The sheath shall be fabricated from one of the following:

1. A polyethylene tube pulled or pushed over the prestressing steel. The polyethylene shall be Type

II, III, or IV as defined by ASTM D 1248 (or approved equal). The tubing shall have a minimum wall thickness of 1/16 inch.

2. A hot-melt extruded polypopylene tube. The polypropylene shall be cell classification B55542-

11 as defined by ASTM D 4101 (or approved equal). The tubing shall have a minimum wall thickness of 1/16 inch.

3. A hot-melt extruded polyethylene tube. The polyethylene shall be high density Type III as defined by ASTM Dl248 (or approved equal).

The tubing shall have a minimum wall thickness of 1/16 inch.

4. Steel tubing conforming to ASTM A 500. The tubing shall have a minimum wall thickness of

3/16 inch.

5. Steel pipe conforming to ASTM A 53. The pipe shall have a minimum wall thickness of 3/16 inch.

6. Plastic pipe or tube of PVC conforming to ASTM

D 1784 Class 13464-B. The pipe or tube shall be

Schedule 40 at a minimum.

7. A corrugated tube conforming to the requirement of the tendon bond length encapsulation.

2.11 Centralizers:

A. Centralizers shall be manufactured from Schedule 40

PVC pipe or tube, steel or other material not detrimental to the anchor steel bar. Wood shall not be used as a material for fabricating centralizers.

B. The centralizer shall be securely attached to the anchor bar.

C. Centralizer Sizing

1. The centralizer shall be sized to position the nail bar within 1 inch (25mm) of the center of the drill hole.

2. The centralizer shall allow the tremie pipe to be inserted to the bottom of the drill hole.

3. The centralizer shall allow grout to flow freely up the drill hole.

2.12 Face Drain

B. Drainage Geotextile for drain strip shall consist of

AASHTO M288 Class 2 material meeting the following minimum Filtration/Hydraulic properties:

1. Permittivity – 0.2 per second

2. AOS – No. 60 (.25 mm)

C. Face drain shall consist of prefabricated vertical geocomposite drainage strip such as Contech C-Drain

11K or approved equal.

2.13 Structural Geogrids:

A. The primary reinforcement shall be Tensar UX1100HS as shown on the plans, or geogrid of equivalent long term design strength, consisting of regular grid structure of select high density polyethylene or polypropylene resin.

Geogrid

Type

Ultimate

Strength

(lb/ft)

Long Term Design

Strength (lb/ft)

UX1100MSE 3970 1157

B. The manufacturer shall furnish the Engineer with written certification that all purchased resin used to produce the structural geogrid is virgin resin.

2.14 Geotextiles:

A. The geotextile shall be Contech C-60NW as shown on the plans, or equivalent, consisting of spun-bound 100% continuous filament polyester needle punched engineering fabric.

B. The minimum physical properties of the geotextile will include the following:

1. Tensile Strength (ASTM D4632) – 160 lbs.

2. Burst Strength (ASTM D3786) - 280 psi.

3. Puncture Strength (ASTM D4833) - 85 lbs.

4. Permeability – 0.24 cm/sec.

C. The manufacturer shall furnish the Engineer with written certification that all geotextile used for construction meets or exceeds the minimum properties required.

2.15 Segmental Concrete facing Units:

A. The segmental concrete facing units shall be Tensar

Mesa Standard block system manufactured by a licensed Mesa Retaining Wall Systems Representative.

B. All concrete wall units including cap units shall have a minimum net 28-day compressive strength of 4,000 psi. The concrete units shall have the required freeze/thaw protection with a maximum absorption rate of 8 percent in southern climates, and 6 percent in northern climates.

1. Cementatious materials used in the manufacture of the units shall be Type I or Type II Portland cement in accordance with ASTM C-150.

2. All aggregates used in the manufacture of the units shall be normal weight conforming to ASTM C-33.

3. Other Constituents - Air entraining agents, coloring pigments, integral water repellents, finely ground silica, and other constituents shall be previously established as suitable for use in segmental concrete retaining wall units and shall conform to applicable

ASTM Standards or shall be shown by test or experience not to be detrimental to the durability of the segmental concrete facing units or any material customarily used in masonry construction.

C. Exterior dimensions of units may vary in accordance with ASTM C-1372. Mesa Standard units shall have a minimum of 1 square foot face area each. Segmental concrete facing unit dimensions shall not differ more than ± 1/8 inch (3.2 mm) from the manufacturer's published dimensions.

D. Mesa Standard block units with unit fill shall provide a minimum of 150 psf of wall face area. Fill which is placed within the dimensions of the units may be considered as 80% of the effective weight.

E. Mesa units shall have angled sides capable of concave and convex alignment curves with a minimum radius of 3-1/2 feet.

F. Mesa units shall be interlocked with non-corrosive

Mesa Connectors.

G. Finish and Appearance

1. All units shall be sound and free of cracks or other defects that would interfere with the proper placing of the unit or significantly impair the strength or permanence of the construction. Minor cracks incidental to the usual method of manufacture, or minor chipping resulting from shipment and delivery, are not grounds for rejection.

2. The exposed surfaces of units shall be free of chips, cracks or other imperfections when viewed from a distance of 10 feet under diffused lighting.

H. Sampling and Testing

1. Sample and test units for compressive strength and absorption in accordance with the applicable provisions of ASTM Method C-140. Compressive strength test specimens shall conform to the saw-cut coupon provisions of section 5.2.4 of ASTM C-

140 with the following exceptions:

a. Coupons shall have a minimum thickness of 1-

1/2 inches (38.1 mm).

I. Color

1. Block samples, indicating available colors, shall be provided to the owner/developer for color selection prior to construction.

2.16 Mesa Segmental Block Unit Shear Connectors:

A. Connectors: High-density polyethylene or polypropylene with fiberglass inclusions.

1. Use MESA DOT connectors (19 teeth and 8 flags) to connect the geogrid to Standard facing units and

MESA Standard connectors to serve as alignment and shear connectors between facing courses that do not require geogrid reinforcement. One DOT connector shall be used per facing unit with the four teeth at each end of the connector driven through the geogrid apertures into the connection slots of the facing unit and the four flags at each end extending into the core of the overlying facing unit. Two Standard connectors shall be driven into the connector slots of all facing units that are not connected to geogrid.

2.17 Base Leveling Pad Materials and

Drainage/Unit Fill for Block:

A. Base Leveling Pad Material: Material for leveling pad shall consist of compacted sand, gravel crushed rock or any combination thereof (use soil types GP, GW, SW, SP or SM), a minimum of 8 inches in thickness, constructed to the minimum dimensions shown on the

B. Drainage/Unit Fill: Fill for units shall consist of clean

1‖ minus free-draining well graded crushed stone or granular fill, meeting the requirements of the following gradation tested in accordance with NDOT Test

Method No. Nev. T206:

Sieve Size Percent Passing 1 inch

3/4 inch ......................... 75-100

No. 4 ............................... 0 - 10

No. 50 ............................... 0 – 5

C. Pea gravel shall not be used in any portion of the base leveling pad or drainage/unit fill.

2.18 Reinforced Backfill:

A. Reinforced backfill shall be per NDOT Standard specification and shall meet the following gradation as determined in accordance with NDOT Test Method No.

Nev. T206:

Sieve Size Percent Passing 3 inch

No. 40 ............................... 15-60

No. 200 ............................. 0 – 15

The plasticity index of the fine fraction shall be less than

6 as determined by Test Method No. Nev. T212.

B. Reinforced material shall exhibit an effective (drained) angle of friction of not less than 34°, determined in accordance with AASHTO T-236. The test shall be run on the portion finer than the No. 10 sieve. The sample will be compacted at optimum moisture content to 95% of the maximum dry density as determined in accordance with the requirements of AASHTO T99, Method C and D at optimum moisture content.

C. The material shall have a magnesium sulfate soundness loss of less than 30% after four cycles or a sodium sulfate soundness loss of less than 15% after five cycles when tested according to AASHTO T104.

D. A certificate of compliance and test report by an

AASHTO accredited laboratory, certifying that the MSE backfill material complies with requirements shall be provided. A minimum of two samples at two different locations must have these two tests conducted. The test results shall be provided to the Engineer.

Granular backfill shall also conform to the following requirements based on usage:

Test Requirements Test Method pH Value 5.0 to 9.5 Nev. T238

Resistivity 3000 ohm.cm

Min.

Nev. T235

Chlorides 100 ppm Max. -

Sulphates 200 ppm Max. -

When the Resistivity is 5,000 ohm.cm or more, the Chlorides and Sulfates requirements are waived

E. USCS soil types CL, CH, ML, MH, SC, and pea gravel shall not be used in any portion of the wall backfill including retained materials placed beyond the reinforced zones.

F. All reinforced backfill materials shall also have the minimum engineering properties shown in Section 4.01, Item A.

G. All imported backfill materials shall be approved by the

Engineer prior to construction.

H. Test results of all proposed imported backfill materials shall be submitted to the Engineer for approval prior to construction.

2.19 Post Foundation System:

A. Post foundation system used for handrail shall be a high density polyethylene sleeve and cap with a minimum average wall thickness of 0.050 inch such as Sleeve-

ItTM 1224R or equivalent. Average wall thickness shall be determined by averaging the wall thickness at two locations approximately 60 degrees apart at the top and bottom of the sleeve halves.

B. Cantilever base shall be 62ksi steel with the exposed portion of the base coated with proprietary PVC plastisol.

C. Two struts will be furnished for each unit. Exposed portions of struts shall be coated with proprietary PVC plastisol.

2.20 Delivery, Storage, and Handling:

A. Structural Geogrid and Geotextiles

1. Contractor shall check to ensure that the proper materials have been received upon delivery.

2. All geogrids and geotextiles shall be stored above -

20°F (-29°C).

3. Contractor shall prevent mud, wet cement, epoxy, and like material which may affix themselves to the gridwork, from coming in contact with the geogrid material.

4. Rolled geogrid material may be laid flat or stood on end for storage.

5. Geogrids shall be stored according to manufacturer's recommendations.

B. Segmental Block Facing Units

1. Contractor shall check to ensure that the proper materials have been received upon delivery.

2. Store products in manufacturer's unopened packaging until ready for installation.

3. Prevent excessive mud, water, fluid concrete, epoxy, or other deleterious materials from coming in contact with and affixing to retaining wall materials.

4. Facing units shall be stacked horizontally versus being stood on end.

C. Anchor Tendon

1. Tendons shall be handled and stored in such a manner as to avoid damage or corrosion. Damage to the prestressing steel, the corrosion protection, and/or the epoxy coating as a result of abrasions, cuts, nicks, welds and weld splatter will be cause for rejection by the Engineer. The prestressing steel shall be protected if welding is to be performed in the vicinity. Grounding of welding leads to the prestressing steel is forbidden.

Prestressing steel shall be protected from dirt, rust, or deleterious substances. A light coating of rust on the steel is acceptable. If heavy corrosion or pitting is noted, the Engineer shall reject the affected tendons.

2. The Contractor shall use care in handling and storing the tendons at the site. Prior to inserting a tendon in the drill hole, the Contractor and the

CQA Inspector shall examine the tendon for damage to the encapsulation and the sheathing. If, in the opinion of the CQA Inspector, the encapsulation is damaged, the Contractor shall repair the encapsulation in accordance with the tendon supplier's recommendations. If, in the opinion of the CQA Inspector, the smooth sheathing has been damaged, the Contractor shall repair it with ultra high molecular weight polyethylene tape. The tape should be spiral wound around the tendon to completely seal the damaged area. The pitch of the spiral shall ensure a double thickness at all points.

3. Banding for fabricated tendons shall be padded to avoid damage to the tendon corrosion protection.

Upon delivery, the fabricated anchors or the prestressing steel for fabrication of the tendons on site and all hardware shall be stored and handled in such a manner to avoid mechanical damage, corrosion, and contamination with dirt or deleterious substances.

4. Prestressing steel shall not be exposed to excessive heat (i.e., more than 230°C).

SECTION 3: EXECUTION

3.01 Drilled Shaft/Steel Pile Installation:

A. Construction of the drilled shaft shall be per applicable portions of NDOT Standard Specification as referenced on item 1.03C and as described herein, whichever is more stringent.

B. The drilled shaft excavations shall be performed by an appropriate drilling method per NDOT Standard

Specification. The drill holes shall be at least 24 inches diameter. Drill holes shall be located by survey and field staked. Field stakes shall include the pile designation (e.g. P1), the ground elevation and the required depth of drilling. The drill hole shall be clean of loose soil or rock prior to installation of pile.

Provide temporary steel casing as required to maintain clean shaft excavations.

C. The Contractor shall ensure that the sidewalls of the predrilled holes (i.e., shafts) do not collapse during drilling. Uncased shafts may be used where the sides and the bottom of the shaft are stable and may be visually inspected prior to placing the soldier pile and concrete. Casing or slurry shall be used where the sides of the shaft require additional support.

D. Loose material shall be removed from the bottom of the shaft. No more than 1 foot of standing water, if any, shall be left in the bottom of the shaft prior to beginning soldier pile installation.

E. The soldier pile shall be placed in the shaft without difficulty and aligned prior to general placement of concrete. The Contractor may place up to 2 feet of concrete at the bottom of the shaft to assist in aligning the soldier pile. The soldier pile shall be blocked or clamped in place at the ground surface, prior to placement of concrete.

F. Piles shall be within 1 percent of plumb and tops of piles shall be within 2 inches of the location shown on the construction drawings. Pile section shall be oriented as shown on the construction drawings.

G. After loose material is removed and the pile is adequately braced, embed the pile with concrete as shown on the Drawings. Vibrate the concrete to ensure displacement of voids. Place drilled shaft concrete using procedures that minimize contact with the steel piling and to prevent segregation of the concrete.

H. Splicing of piles shall not be permitted, unless approved in writing by the Engineer. All structural welding of steel and steel reinforcement shall be performed by certified welders qualified to perform the type of welding. All piles shall be cut-off to a true plane at the elevations shown on the Contract

Drawings. All cutoff lengths shall remain the property of the Contractor and shall be properly disposed of offsite.

I. Anchor-pile connection welding and workmanship shall be inspected by the Contractor’s qualified superintendant prior to installation of tieback anchors.

Connection locations shall be within a vertical tolerance of +/-4 inches.

J. For shafts constructed without casing or drilling slurry, concrete (either structural or lean-mix backfill) may be placed by free-falling the concrete from the ground surface down the shaft and around the soldier pile. If casing is used, the placement of concrete shall begin prior to casing removal. Remove the casing while the concrete remains workable. For shafts constructed using slurry, concrete shall be placed using the tremie method from the bottom of the shaft.

The tremie pipe shall be withdrawn slowly as the level of the concrete rises in the shaft and the level of the tremie pipe outlet shall never exceed the height of the slurry.

3.02 Reinforced Concrete Panel Lagging:

A. Place reinforced concrete panel lagging inside the flanges of the exposed solider piles as shown on

B. Insure all lagging are in contact at the face of the steel piles. Lagging shall overlap pile flanges at least 2.0 inches. After installation of lagging, the edge of the pile flanges shall be spray paint marked to aid in visual monitoring of movement of lagging.

C. Concrete lagging shall be placed from the top-down in sufficiently small lifts immediately after excavation to prevent erosion of materials into the excavation.

Excavation should be done carefully to prevent the formation of voids behind lagging.

D. Prior to lagging placement, the soil face shall be smoothed to create a contact surface for the lagging.

Gaps behind the lagging shall be backfilled with drainage/unit fill (Section 2.17, Item B) and compacted prior to applying any loads to the ground anchors.

E. A gap shall be maintained between each vertically adjacent lagging board for drainage between adjacent lagging sections. Lagging face shall not be placed in tight contact to adjacent lagging. The maximum spacing between lagging face shall be less than 1/2 inches. The lagging face may be installed by using spacers to permit adequate drainage.

F. Lagging may be wedged back to provide tight soil-to-lagging contact. Voids behind lagging should be filled with sand-water slurry.

G. Where ―running‖ sand is encountered, care must be taken to minimize soil loss. In this case, lagging may need to be installed one board at a time.

H. Place drain system behind concrete panel as lagging is being placed.

3.03 Wall Drainage Construction:

A. Upon completion of excavation and during lagging placement, a wall drainage network shall be constructed as shown on the Plans, specified herein, or as required by the Engineer to suit the site conditions. The drainage network shall consist of installing geocomposite drain strips and PVC connection pipes as shown on the Plans or as directed by the Engineer.

B. Geocomposite drain strips shall be centered between the columns of piles as shown on the Plans. The drain strips shall be at least 18-inches wide and placed with the geotextile side against the ground. Secure the strips to the wood lagging. Drain strips will be continuous and splices shall be made with a 12-inch minimum overlap such that the flow of water is not impeded.

C. Connection pipes shall be as shown on the Plans.

Connection pipes shall be solid PVC pipe installed to direct water from the geocomposite drain strips to the exposed face of the wall. Connect the connection pipes to the drain strips using prefabricated drain grates as shown on the Plans.

D. Drain grates shall be installed per the manufacturer's recommendations. The joint between the drain grate and the drain strip and the discharge end of the connector pipe shall be sealed to prevent shotcrete intrusion.

E. Weepholes shall be provided through the timber lagging to drain water from behind the facing. Install as shown on the Plans. Use PVC pipe to form the weephole through the timber. All weep holes should be extended through the timber lagging. Cover the end of the pipe contacting the soil with a drainage geotextile.

3.04 Anchor Installation:

A. Contractor’s specialty subcontractor responsible for anchor installation shall ensure that the anchor bar supplier reviews all of the related anchor materials and design load requirements on the construction drawings. Install anchors to the specifications of the anchor bar supplier and the requirements herein.

B. Prior to installation of anchors, the excavation in front of the wall shall not be more than 2 feet lower than the anchor-pile connection point. The wall excavations shall not resume until after the tiebacks are tensioned and accepted.

C. Anchors shall be installed at locations and alignments shown on the construction drawings. The anchor inclination tolerance is +/-2 degrees. The unbonded length and bonded length shall not be less than specified on the construction drawings. Anchor bars shall be free of oil or grease coatings.

D. Field cutting shall be performed solely with a portable band saw or abrasive cutoff wheel.

E. The Contractor is solely responsible for developing the required grout body along the entire bonded length of the anchor.

F. Centralizers shall be placed at maximum 10-foot intervals along the anchor bar.

G. Plastic sheathes and bondbreakers shall be placed the full length within the unbonded length of the anchor, as specified on the construction drawings.

Additionally, trumpets shall be installed for corrosion protection in the transition length from the anchorage to the anchor unbonded length

3.05 Anchorage Installation

A. The anchor bearing plate, the flange stiffeners, the anchor head or nut shall be installed perpendicular to the tendon, within plus/minus three (3) degrees and centered on the bearing plate, without bending or kinking of the prestressing steel elements. Wedge holes and wedges shall be free of rust, grout, and dirt.

B. The stressing tail shall be cleaned and protected from damage until final testing and lock-off. After the anchor has been accepted by the Engineer, the stress tail shall be cut to its final length according to the tendon manufacturer's recommendations.

C. The corrosion protection surrounding the unbonded length of the tendon shall extend up beyond the bottom seal of the trumpet or 5 inches into the trumpet if no trumpet seal is provided. If the protection does not extend beyond the seal or sufficiently far enough into the trumpet, the

Contractor shall extend the corrosion protection or lengthen the trumpet.

D. The corrosion protection surrounding the unbonded length of the tendon shall not contact the bearing plate or the anchor head during testing and stressing. If the protection is too long, the Contractor shall trim the corrosion protection to prevent contact.

E. After anchor testing and lock-off, the trumpet should be filled with grout and a cover placed. Grout levels in the trumpet and cover must be verified after the grout has set to ensure complete filling. If complete grout filling is not obtained, regrouting of the trumpet shall be performed to obtain the complete filling as required.

3.06 Stressing, Load testing, and Acceptance

A. Each ground anchor shall be tested. No load greater than ten (10) percent of the design load can be applied to the ground anchor prior to testing. The maximum test load shall be no less than 1.33 times the design load and shall not exceed 80 percent of the specified minimum ultimate tensile strength (SMTS) of the prestressing steel of the tendon. The test load shall be simultaneously applied to the entire tendon. Where applicable, stressing of single elements of multi-element tendons shall not be permitted.

B. After 72 hours of grout cure time and after the final grout has reach a compressive strength of 3,000 psi, each anchor shall be tested and tensioned to 80 percent of the design load (DL) shown on the

3.07 Stressing Equipment

A. The testing equipment shall consist of:

1. A dial gauge or vernier scale capable of measuring to the nearest 0.001 inches shall be used to measure the ground anchor movement. The movement-measuring device shall have a minimum travel equal to the theoretical elastic elongation of the total anchor length at the maximum test load and it shall have adequate travel so the ground anchor movement can be measured without resetting the device at an interim point.

2. A hydraulic jack and pump shall be used to apply the test load. The jack and a calibrated primary pressure gauge shall be used to measure the applied load. The jack and primary pressure gauge shall be calibrated by an independent firm as a unit. The calibration shall have been performed within forty-five (45) working days of the date when the calibration submittals are provided to the

Engineer. Testing cannot commence until the

Engineer has approved the calibration. The primary pressure gauge shall be graduated in 35 psf increments or less. The ram travel shall be at least 6 in and preferably not be less than the theoretical elongation of the tendon at the maximum test load. If elongations greater than 6 inches are required, restroking can be allowed.

3. A calibrated reference pressure gauge shall also be kept at the site to periodically check the production

(i.e., primary pressure) gauge. The reference gauge shall be calibrated with the test jack and primary pressure gauge. The reference pressure gauge shall be stored indoors and not subjected to rough treatment.

4. The Contractor shall provide an electrical resistance load cell and readout to be used when performing an extended creep test.

5. The stressing equipment shall be placed over the ground anchor tendon in such a manner that the jack, bearing plates, load cells and stressing anchorage are axially aligned with the tendon and the tendon is centered within the equipment.

3.08 Load Testing Setup

A. Dial gauges shall bear on the pulling head of the jack and their stems shall be coaxial with the tendon direction. The gauges shall be supported on an independent, fixed frame, such as a tripod, which will not move as a result of stressing or other construction activities during the operation.

B. Prior to setting the dial gauges, the Alignment Load

(AL) shall be accurately placed on the tendon. The magnitude of AL depends on the type and length of the tendon.

C. Regripping of strands, which would cause overlapping wedge bites, or wedge bites on the tendon below the anchor head, shall be avoided.

D. Stressing and testing of multiple element tendons with single element jacks is not permitted.

E. Stressing shall not begin before the grout has reached adequate strength.

3.09 Verification Performance Tests

A. Five (5) percent of the ground anchors or a minimum of three (3) ground anchors, whichever is greater, shall be performance tested in accordance with the procedures described below. The Engineer shall select the ground anchors to be performance tested. The remaining ground anchors shall be tested in accordance with the proof test procedures (see Section 3.10).

B. The verification performance test shall be made by incrementally loading and unloading the ground anchor

(cycled loading) in accordance with the schedule provided below. The load shall be raised from one increment to another immediately after recording the ground anchor movement. The ground anchor movement shall be measured and recorded to the nearest 0.001 inches with respect to an independent fixed reference point at the alignment load and at each increment of load. The load shall be monitored with the primary pressure gauge. The reference pressure gauge shall be placed in series with the primary pressure gauge during each performance test. If the load determined by the reference pressure gauge and the load determined by the primary pressure gauge differ by more than ten (10) percent, the jack, primary pressure gauge and reference pressure gauge shall be recalibrated at no expense to the Owner. At load increments other than the maximum test load, the load shall be held just long enough to obtain the movement reading. The maximum test load in a performance test shall be held for ten (10) minutes. A load cell shall be used to monitor small changes in load during constant load-hold periods.

C. Steps for the Verification Performance Test:

Cycle Step Load

1 .......................................... AL*

2 ................................... 0.25DL*

3 ..................................... 0.50DL

4 ..................................... 0.75DL

5 ..................................... 1.00DL

6 ..................................... 1.20DL

7 ..................................... 1.33DL

Where AL is the alignment load and DL is the design load.

1. Hold load for 10 minutes while recording movement at specified times. If the total movement measured during the load hold exceeds the specified maximum value then the load hold should be extended to a total of 60 minutes.

2. In the Cycles 1 through 6, the minimum cycle load shall be equal to the alignment load (AL). The minimum cycle load for step 7 shall be 0.25DL

3. The jack shall be adjusted as necessary in order to maintain a constant load. The load-hold period shall start as soon as the maximum test load is applied and the ground anchor movement, with respect to a fixed reference, shall be measured and recorded at 1 minute, 2, 3, 4, 5, 6 and 10 minutes.

If the ground anchor movement between one (1) minute and ten (10) minutes exceeds 0.04 inches, the maximum test load shall be held for an additional 50 minutes. If the load hold is extended, the ground anchor movement shall be recorded at

15 minutes, 20, 30, 40, 50 and 60 minutes.

4. During the hold times, the anchor load shall not be allowed to deviate more than 50 psi. The load shall always be returned to the specified test load prior to taking the movement reading. Two deflection gauges shall be used together to measure anchor bar movement. It is important that a void be left between the top of the grout and the soldier pile to allow for movement of the grout column during testing.

3.10 Proof Tests

A. The proof test shall be performed by incrementally loading the ground anchor in accordance with the following schedule. The load shall be raised from one increment to another immediately after recording the ground anchor movement. The ground anchor movement shall be measured and recorded to the nearest 0.001 inches with respect to an independent fixed reference point at the alignment load and at each increment of load. The load shall be monitored with the primary pressure gauge. At load increments other than the maximum test load, the load shall be held just long enough to obtain the movement reading.

B. Test load equipment and procedures shall conform to the requirements of the ―Recommendation of

Prestressed Rock and Soil Anchors‖ by the Post

Tensioning Institute. Tensioning steps shall be performed as follows and the results recorded on a test report.

C. Proof Test Schedule:

Step Load

1 ............................................ AL

2 ..................................... 0.25DL

3 ..................................... 0.50DL

4 ..................................... 0.75DL

5 ..................................... 1.00DL

6 ..................................... 1.20DL

7 ..................................... 1.33DL

8 ........... Reduce to lock-off load

9 ............................. AL (optional

10 Adjust to lock-off load (0.80 DL)

The maximum test load in a proof test shall be held for ten (10) minutes. The jack shall be adjusted as necessary in order to maintain a constant load. The load-hold period shall start as soon as the maximum test load is applied and the ground anchor movement with respect to a fixed reference shall be measured and recorded at 1 minute, 2, 3, 4, 5, 6 and 10 minutes. If the ground anchor movement between one (1) minute and ten (10) minutes exceeds 0.04 inches, the maximum test load shall be held for an additional 50 minutes. If the load hold is extended, the ground anchor movements shall be recorded at 15 minutes, 20, 30, 40, 50 and 60 minutes.

During the hold times, the anchor load shall not be allowed to deviate more than 50 psi. The load shall always be returned to the specified test load prior to taking the movement reading. Two deflection gauges shall be used together to measure anchor bar movement. It is important that a void be left between the top of the grout and the soldier pile to allow for movement of the grout column during testing.

D. Procedure: Lock-off load shall be as specified and performed by tightening the lock-off nut such that the jack pressure gauge reading decreases suddenly by about 5 percent.

E. The Engineer may require the Contractor to replace some or all of the installed production anchors between a failed proof test anchor and the adjacent passing proof test nail.

3.11 Extended Creep Tests

A. The Owner shall determine if extended creep testing is required and select those ground anchors that are to be creep tested. If creep tests are required, at least two (2) ground anchors shall be creep tested. The stressing equipment shall be capable of measuring and maintaining the hydraulic pressure within 7.3 psf.

3.12 Ground Anchor Acceptance Criteria

A. A performance-tested or proof-tested ground anchor with a 10 minute load hold shall be acceptable if the:

(1) ground anchor resists the maximum test load with less than 0.04 inches of movement between 1 minute and 10 minutes; and (2) total elastic movement at the maximum test load exceeds 80 percent of the theoretical elastic elongation of the unbonded length.

B. A performance-tested or proof-tested ground anchor with a 60 minute load hold shall be acceptable if the:

(1) ground anchor resists the maximum test load with a creep rate that does not exceed 0.08 in the last log cycle of time; and (2) total elastic movement at the

C. A ground anchor creep testing is acceptable if the: (1) ground anchor resists the maximum test load with a creep rate that does not exceed 0.08 inches in the last log cycle of time; and (2) total elastic movement at the

3.13 Procedures for Anchors Failing Acceptance

Criteria

A. Anchors that do not satisfy the minimum apparent free length criteria shall be either rejected and replaced at no additional cost to the Owner or locked off at not more than 50 percent of the maximum acceptable load attained. In this event, no further acceptance criteria are applied.

B. Re-groutable anchors which satisfy the minimum apparent free length criteria but which fail the extended creep test at the test load may be post-grouted and subjected to an enhanced creep criterion. This enhanced criterion requires a creep movement of not more than 0.04 inches between 1 and 60 minutes at test load. Anchors which satisfy the enhanced creep criterion shall be locked off at the design lock-off load.

Anchors which cannot be post-grouted or re-groutable anchors that do not satisfy the enhanced creep criterion shall be either rejected or locked off at 50% of the maximum acceptable test load attained. In this event, no further acceptance criteria are applied. The maximum acceptable test load with respect to creep shall correspond to that where acceptable creep movements are measured over the final log cycle of time.

C. In the event that an anchor fails, the Contractor shall modify the design and/or construction procedures.

These modifications may include, but are not limited to, installing additional anchors, modifying the installation methods, reducing the anchor design load by increasing the number of anchors, increasing the anchor…