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Vertical (wick) Drain Installation Specifications

The following are suggested specifications for the installation of prefabricated plastic vertical soil drains

A. Description

The Contractor shall furnish all necessary labor, equipment, and materials and perform all operations necessary for the installation of vertical drains in accordance with the details shown on the plans and with the requirements of these specifications. The drains shall consist of a band-shaped plastic core enclosed in a suitable filter material and shall be spaced and arranged as shown on the plans or as otherwise directed by the Engineer.

B. Material

The vertical drain shall be a prefabricated type made up of a polypropylene drainage core wrapped in a filter made of a non-woven fabric of continuous filaments of 100% polypropylene similar to the product known as AMERDRAIN 407, or approved equal. The core shall be fabricated with suitable drainage channels.

The drain shall be of United States manufacture and have the following minimum properties:

Drain      
Weight 0.8 oz/ft  75 gm/m  
Width  3.8 inches  95 mm  
Thickness  1/8 inch  3 mm  
Discharge capacity 1.5 gpm 90x10-6m3/sec  ASTM D4716
Core      
Tensile strength 175 lbs 750N ASTM D1621
 Fabric      
 Grab tensile strength  120 lbs 530N  ASTM D4632
 Elongation at break   >70 %  >70 %  ASTM D4632
 Trapezoidal tear  50 lbs 220N  ASTM D4533
 Puncture strength  38 lbs 160N  ASTM D4833
 Mullen burst  130 psi 900kPa  ASTM D3786
 Specific Gravity  0.95  0.95  
 Flow rate  70 gpm/ft2  3,000 lpm/m2  ASTM D4491
 Permeability 0.02 cm/sec  0.02 cm/sec  ASTM D4491

The Contractor shall submit drain samples and indicate the source of the proposed materials prior to delivery to the site and shall allow sufficient time for the Engineer to evaluate the material.

C. Equipment

Drains shall be installed with approved modern equipment of a type which will cause a minimum of disturbance of the subsoil during the installation operation.

The prefabricated drains shall be installed using a mandrel or sleeve that will be advanced through the soil to the required depth. Constant load or constant rate of advancement methods are the preferred methods. The equipment shall be capable of exerting at least 12 tons of vertical force (static crowd) to the mandrel. A vibrator with an eccentric moment of at least 1500 in-lbs (165 Nm) shall be available for use in areas where constant load or constant rate of advancement methods cannot install the drains to the design depths. Drains which cannot be installed to design penetration using only static methods must be advanced with the use of the vibrator to be considered for compensation. A drain may be abandoned before reaching design penetration when the rate of installation is less than 6 inches(15 cm) per second with the full static force and maximum vibrator output. Use of falling weight impact hammers or jetting will not be allowed.  The mandrel shall protect the prefabricated drain material from tears, cuts, and abrasions during installation and shall be withdrawn after installation of the drain. The mandrel shall be rectangular in shape and of minimum cross sectional area not to exceed 10 in2(50 cm2).Small quantities of water will be allowed into the mandrel to add in anchoring.

At least two weeks prior to the installation of drains, the contractor shall submit to the Engineer for his review and approval, details of the sequence and method of installation. Approval by the Engineer will not relieve the Contractor of his responsibility to install drains in accordance with these specifications.

D. Construction Requirements

Prior to the installation of drains within the designated area the Contractor shall demonstrate that his equipment, method and materials produce a satisfactory installation in accordance with these specifications. For this purpose, the Contractor will be required to install trial drains at locations designated by the Engineer. Payment will be at the bid price per linear foot(meter) for the drains. Payment will not be made for installing unsatisfactory trial drains.

As a minimum experience requirement, the contractor shall have successfully completed three vertical drain installation projects. The three projects shall be identified by project name, location, project description, size, completion date, and contract manager.

Approval by the Engineer of the method and equipment used to install the trial drains shall not constitute, necessarily, acceptance of the method for the remainder of the project. If at any time, the Engineer considers that the method of installation does not produce a satisfactory drain, the Contractor shall alter his method and/or equipment as necessary to comply with these specifications.

Drains will located, numbered and staked out by the Engineer. The contractor shall take all reasonable precautions to preserve the stakes. The location of the drains shall not vary by more than 6 inches(150mm) from the locations indicated on the drawings or as directed by the Engineer.

Drains shall be installed from the working surface to the depth shown on the drawings, or to such a depth where the soil resists a reasonable effort at further penetration. The Engineer may vary the depths, spacing, or the number of drains to be installed, and may revise the plan limits for this work as necessary.

The equipment shall be carefully checked for plumbness prior to advancing each drain, and must not deviate more than 1 inch per foot(80mm/m) from the vertical.

Drains that are out of their proper location by more than 6 inches(150 mm) or drains that are damaged in construction, or drains that are improperly completed shall be rejected by the Engineer, and no compensation will be allowed for any materials furnished or for any work performed on such drains.

The contractor shall provide the Engineer with suitable means of making a linear determination of the quantity of drain material used.

During installation of the drain, the contractor shall provide suitable means of determining the depth of the drain.

Splices or connections in the drainage material shall be done in a workmanlike manner and so as to insure continuity of drain material. There should be a 4-8 inch(100-200 mm) length of drain material protruding above the natural ground surface at each drain location. The drain material shall be cut neatly at its upper end.

The Contractor shall be permitted to use auguring or other methods to loosen stiff upper soils prior to the installation of the drains, provided that such auguring does not extend more than 2 feet(600 mm) into the underlying highly compressible soils.

Where obstructions are encountered below the working surface which cannot be penetrated using normal and accepted procedures, the Contractor shall complete the drain from the elevation of the obstruction to the working surface and notify the Engineer's representative. At the direction of the Engineer, the Contractor shall then install a new drain within 18 inches(500mm) from the obstructed drain. The Contractor shall be paid for all obstructed drains at the contract unit price unless the drain is improperly completed.

The Contractor shall observe precautions necessary for protection of instrumentation devices. After instrumentation devices have been installed, the Contractor shall replace at his cost any equipment that is damaged or becomes unreliable as a result of his negligence.

E. Method of Measurement

Vertical drains will be measured by the linear foot (meter) for the full length of drain material complete and in place.

F. Basis of Payment

Payment for drains will be made at the contract unit price per linear foot (meter), which price shall be full compensation for the cost of furnishing the full length of drain material, installing the drain, and shall also include the cost of furnishing all tools, materials, labor and equipment  to complete the required work as per project specifications. No direct payment will be made for unacceptable drainage drains or for any delays or expenses incurred through changes necessitated by improper or unacceptable material or equipment, but the costs of such shall be included in the unit price bid for this work.

For additional information installing vertical drain, other GTA contracting services, or for assistance with your next ground improvement project fax us at (770) 719-1907 or email us at RussJoiner@msn.com

 

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