Part 1 — General
1.1 Section Includes
A.Prefabricated vertical drains (PVDs) for accelerating the required duration of primary consolidation in soft, compressible plastic soils.
1.2 RELATED SECTIONS Not Used
1.3 References
A.ASTM D 3786: Bursting Strength of Textile Fabrics-Diaphragm Bursting Strength Tester Method
B.ASTM D 4491: Water Permeability of Geotextiles by Permittivity
C.ASTM D 4533: Trapezoid Tearing Strength of Geotextiles
D.ASTM D 4595: Tensile Properties of Geotextiles by the Wide-Width Strip Method
E.ASTM D 4632: Grab Breaking Load and Elongation of Geotextiles
F.ASTM D 4716: Determining the (In-plane) Flow Rate per Unit Width and Hydraulic Transmissivity of a Geosynthetic Using a Constant Head
G.ASTM D 4751: Determining Apparent Opening Size of a Geotextile
H.ASTM D 4833: Index Puncture Resistance of Geomembranes and Related Products
1.4 Definitions
A.Artesian Groundwater Conditions – Subsurface conditions that contain a hydrostatic head elevation that is higher than the ground surface Prefabricated Vertical Drains
1.5 Submittals
A.Manufacturer’s literature for review including the following:
1.Physical and mechanical properties of the PVD
2.List of projects of similar conditions where the PVD has been installed.
B.Samples for verification
1.Two unspliced PVDs at least 3 ft long
2.Two spliced PVDs long enough to include the splice plus 1 ft of unspliced drain on both sides of the splice
C.Work plan for review detailing at least the following:
1.Type of PVD and splicing instructions
2.PVD installation equipment and method
3.Method of determining the depth of the advancing PVD, and final depth installed
4.Anchor system and contingencies for failed anchorage
5.Installation map, including locations and depths and sequence
6.Equipment, grout materials, and work plan for the sealing of penetration holes where artesian groundwater conditions are encountered.
a.Grout materials may include a low permeability mixture of bentonite, water, portland cement, and other additives.
D.A daily summary report for information describing the PVDs installed the previous day. Include at least the following:
1.PVD type
2.Location and length of each PVD installed to the nearest 1 ft
3.Working ground elevation
4.Specific location and depth for:
a.PVDs installed using vibration, and the depths where vibration was used during installation of each of those drains.
1.6 Quality Assurance
A.Replace PVDs that are more than 6 inch from design plan location or are damaged or improperly installed.
1.Leave in-place existing PVDs that are replaced. Prefabricated Vertical Drains
Part 2 — Products
2.1 Prefabricated Vertical Drain
A.A PVD consists of a drainage core enclosed in or integrated with a geotextile jacket.
B.Provide PVDs meeting the following requirements:
1.Weight of at least 0.8 oz/ft
2.Width of at least 3.8 inch
3.Thickness of at least 1/8 inch
4.Aspect ratio (width divided by thickness) less than 40
5.Discharge capacity of at least 1.5 gallons per minute at 50 psi and 25 percent compression according to ASTM D 4716
6.Spliced sections must maintain structural and hydraulic continuity of the drain C Drainage Core
1.Polyethylene or polypropylene plastic material fabricated to promote continuous drainage along the axis of the vertical drain
2.Provide a tensile strength of 225 lbs according to ASTM D 4595.
D.Geotextile Jacket
1.A synthetic nonwoven geotextile of 100 percent heat-set continuous filament polypropylene
2.Meet the properties listed in Table 1. Table 1 Geotextile Jacket Minimum Properties Minimum Average Property Test Method Roll Value Grab Tensile Strength 120 lbs ASTM D 4632 Trapezoidal Tear 50 lbs ASTM D 4533 Puncture Strength 38 lbs ASTM D 4833 Mullen Burst Strength 130 psi ASTM D 3786 Elongation at Break ≥50% ASTM D 4632 Permittivity 0.45 sec-1 ASTM D 4491 Apparent Opening Size (AOS) ≤70 sieve ASTM D 4751 Prefabricated Vertical Drains
E.Label or tag PVDs delivered to the site so that the information for sample identification and other quality control purposes can be read from the label.
1.As a minimum, identify each roll by the manufacturer as to lot or control numbers, individual roll number, date of manufacture, manufacturer, and product identification of the jacket and core.
F.Wrap PVD roll in heavy paper, burlap, plastic, or similar heavy-duty protective covering during shipping.
1.Protect the PVD from sunlight, mud, dirt, dust, debris, and other detrimental substances during shipping and onsite storage.
2.2 Pvd Drainage Layer
A.Clean sand and/or fine gravel meeting the gradation requirements of Table 2 Table 2 PVD Drainage Layer Gradation Sieve Size Percent Passing 2 inch 100 ½ inch 65-100 No. 4 50-100 No. 10 40-70 No. 40 10-40 No. 200 0-5
2.3 Installation Equipment
A.Use a mandrel or sleeve sufficiently stiff to prevent wobble or deflection and provide a vertical installation without significantly disturbing the subsoil during installation.
1.Use a mandrel or sleeve that has a maximum cross-sectional area of 12.2 in2.
2.Use of a standard “foot” is allowed, provided that the largest surface area is less than 12.5 in2.
B.Use a mandrel or sleeve with an anchor system at the bottom to permit the installation of the drain and to anchor the drain tip at the required depth at the time of mandrel withdrawal.
1.Use anchors with dimensions that conform as closely as possible to the dimensions of the mandrel so as to minimize soil disturbance. Prefabricated Vertical Drains
2.Use one 8 inch long piece of No. 4 reinforcing steel as the primary anchoring method.
a.A 9 inch long piece of No. 4 reinforcing steel may be used as the anchoring method if the 8 inch long reinforcing is insufficient.
b.A 4 inch by 7 inch sheet metal plate with a sheet metal bale may be used as the anchoring method if both the 8 inch and 9 inch long pieces of reinforcing steel fail to anchor the drain tip.
C.Provide a vibrator with an eccentric moment of at least 500 in-lbs
Part 3 — Execution
3.1 General
A.Place PVD drainage layer before installing PVDs.
B.Install PVDs according to the authorized work plan.
C.Locate, number, and stake PVD installation locations.
1.Preserve the stakes
2.Re-stake as needed
3.Do not vary the as-installed location of the PVDs by more than 6 inch from the locations shown in the work plan.
D.Do not use installation techniques requiring driving or jetting.
1.Use only limited amounts of injected water to facilitate anchoring PVDs, where necessary.
3.2 DEMONSTRATION PVDs
A.Install a demonstration PVD in each work area before installing production PVDs to demonstrate that equipment, methods, and materials produce a satisfactory installation.
1.The Geotechnical Engineer of Record evaluates demonstration PVD installation at each work area regarding penetration depths, the need for vibration to reach design penetration depths, anchorage of the PVDs, and the presence of artesian groundwater conditions.
B.Alter the method and equipment as necessary to comply with these specifications if at any time the method of installation does not produce satisfactory PVDs. Prefabricated Vertical Drains
3.3 Pvd Installation
A.Plumb equipment for installing PVDs prior to installing each drain.
1.Do not deviate from vertical more than 5.0 inch in 10 ft during installation of drain.
B.Advance the mandrel with constant pressure.
1.Use vibratory installation methods only in cases where design penetration cannot be achieved by using the full static force available to the mandrel.
2.Do not raise the mandrel until the PVD has reached its target depth.
a.Do not raise and lower the mandrel during advancement.
C.Splice or connect the PVD material to provide continuity of the drain.
1.Splice PVD material by stapling.
2.Only one splice is permitted per each PVD
D.Extend PVDs from the surface of the PVD drainage layer to the depth shown in the authorized work plan.
1.Provide at least 4 inch of PVD material protruding above the PVD drainage layer surface at each drain location.
2.Cut the PVD material neatly at the surface of the PVD drainage layer.
E.Predrill or spud through existing embankments or through obstructions before installing the PVD.
1.Refer to this Section, Article 3.4 for more information.
3.4 Pre-Drilling
A.Use auguring, spudding, or other methods to loosen the soil and clear obstructions.
1.Do not penetrate the auger more than two ft into the underlying compressible soil.
B.Penetrate overlying fill material and man-made obstructions as necessary to satisfactorily install the PVDs.
C.Use augers sized as follows if auguring is the selected method:
1.Outside diameter at least equal to the largest horizontal dimension of the mandrel, shoe, or anchor but no larger than 3 inch more than the smallest outside mandrel, shoe or anchor diameter. Prefabricated Vertical Drains
D.Installation obstructions
1.Immediately notify the Engineer prior to installing any other drains if an obstruction is encountered.
2.Attempt to install PVDs within 2 ft of the obstructed location at the direction of and under the review of the Engineer.
3.Document an obstruction clearance procedure in writing for the obstruction encountered and install the drains accordingly.
3.5 Artesian Groundwater Conditions
A.Coordinate with the Engineer when artesian groundwater conditions are encountered to determine the need for sealing the PVD penetration hole.
B.Follow the authorized work plan to seal the penetration hole as necessary.
3.6 Pvd Drainage Layer Compaction
A.Compact the PVD drainage layer using at least two passes with a vibratory compactor after completing installation of PVDs. Prefabricated Vertical Drains
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Source: Utah Standard Specifications for Road and Bridge Construction, 2027 Edition. Pages 342–348 of 1,343. View official source ↗