Proposed ASTM Standard Method

Transcription

1 Proposed ASTM Standard Method AUTHORS: Jack Fowler, PhD., P.E., Geotec Associates, 5000 Lowery Road, Vicksburg, MS, 39180, , Tom Stephens, Vice President, TC Mirafi, 365 S. Holland Drive, Pendergrass, GA, 30567, , Standard Test Method for Determining the Flow Rate of Suspended Solids from a Geotextile Containment System for Dredged Material 1,2 1. Scope 1.1 This test method is used to determine the flow rate of suspended solids through a geotextile container used to contain dredged material The results for the sediment that pass through the geotextile container are shown as the percent total suspended solids in milligrams per liter or parts per million The flow rate is the average rate of passage of a quantity of dredged material and water through the bag over a specific time period. 1.2 This test method requires several pieces of specified pieces of equipment, such as an integrated water sampler and an analytical balance, a geotextile container, a wooden frame to hold the geotextile container, and clean containers to collect the dredged material sediment and a representative sample of dredged material from the proposed dredge area. 1.3 The values stated in SI units are the standard, while the inch-pound units are provided for information. The values expressed in each system may not be exact equivalents: therefore, each system must be used independently of the other, without combining values in any way. 1.4 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices for contaminated dredged materials and determine the applicability of regulatory limitations prior to use. 2. Referenced Documents 2.1 ASTM Standards D 123 Terminology Relating to Textiles Material 3 D 653 Terminology Relating to Soil, Rock, and Contained Fluids 4 D 4439 Terminology for Geosynthetics 4 D 4759 Practice for Determining the Specification Conformance of Geosynthetics 4 Preliminary proposal, ASTM Section D on Navigation Dredging May 20, 1993.

2 2.2 American Public Health Association (APHA) Standard: 208D Total Nonfilterable Residue Dried at C (Total Suspended Matter) 5 3. Terminology 3.1 Definitions: dredged material-see proposed standard for dredged material terminology filtration-see filter filter-see Terminology D geosynthetic, n-a planar product manufactured from polymeric material used with foundation soil, rock, earth, or any other geotechnical engineering related material as an integral part of a man-made project, structure, or system. (See Practice D 4759.) geotextile, n-any permeable textile material used with foundation, soil, rock, earth, or any other geotechnical engineering related material, as an integral part of a manmade project, structure, or system performance property, n-a result obtained by conducting a performance test performance test, n-in geosynthetics, a laboratory procedure which simulates selected field conditions which can be used in design For definitions of other terms relating to geosynthetics, refer to Terminology D For definitions of textile terms, refer to Terminology D 123. For definitions of soil terms, refer to Terminology D Descriptions of Terms Specific to This Standard: flow rate, FR [L 3 T -1 ], n-the volume of fluid per unit time, expressed as an average, which passes through a geotextile container of specified dimensions funnel, n-an apparatus that directs a liquid into a container geotextile container, n-a bag, tube, sock, or container designed and fabricated from a combination or layers of permeable non-woven and woven geotextile fabric to retained the maximum percent of fine grained dredged material for subsequent drainage and consolidation of the contained semi-fluid materials. 4. Summary of Test Method 4.1 A geotextile container is constructed by sewing one or more layers of geotextile together to form a container that will support and contain a measured amount of saturated dredged material The time and amount of sediment that flows through the geotextile container collected at given time intervals and is measured. The amount of sediment passing the geotextile container is determined as the total suspended solids and the flow rate are calculated from these measured values. 4.2 Dredged material from the area to be dredged should be used in this test method. 5. Significance and Use 5.1 This test method is used to determine percent total suspended solids of sediment

3 passing through the geotextile container over a specified time period. 5.2 This test method may be used to design geotextile container systems that contain fine grained dredged materials to meet special environmental requirements of regulatory agencies in determining the amount dredged material sediment passing a geotextile and the flow rate for specific dredged material conditions The designer can use this test method to determine the quantity of fine grained dredged material sediment that may pass through the geotextile container into the environment. 5.3 This test method is intended as an index test for performance evaluation, as the results will depend on the specific dredged materials evaluated and the location of the geotextile container below or above water. It is recommended that the user or a representative perform the test to pre-approved products, because geotextile manufacturers are not typically equipped to handle or test fine grained dredged materials requirements. 5.4 This test method provides a means of evaluating geotextile containers with different dredged materials under various conditions that simulate the conditions that exist with geotextile contained dredged material. The number of times this tests is repeated depends on the users and the site conditions. 6. Apparatus 6.1 Wooden Frame, shown in Fig Geotextile Container with eight evenly space metal grommets, 45 inch inside circumference, 65 inch length, approximate capacity filled about 56 inch deep is about 175-L (40 gal), shown in Fig Three shallow 3 inch deep, 24 inch diameter aluminum pan (Hot water heater drip pan) shown in Fig Integrated Water Sampler, 6 a 500-ml (0.13-gal) device used to collect integrated samples of water. 6.5 Two Large 55 gallon containers approved for contaminated dredged material when required. 6.6 Stopwatch. 6.7 Stirrer, such as a stirring rod on a portable electric drill. 6.8 Dredged Material from the proposed dredge area. 6.9 Gooch Crucible Membrane Filter Apparatus Vacuum Pump.

4 6.12 Sediment free water, prepared from water obtained from the proposed dredged area to soak geotextile containers, do not use distilled water. 7. Sampling 7.1 Geotextile Container Lot Sample for Geotextile Container-Divide the product into lots and take the lot samples as directed in Practice D Geotextile Container Sample-After first discarding a minimum of 1 m (3.3 ft) of geotextile from the end of the roll, cut sufficient lengths to fabricate the number of containers for the appropriate number of tests. If holes or damaged areas are evident, then damaged areas should be discarded and additional material used. No fabric should be used within 0.2 m (6 in.) of a selvedged edge. 7.2 Dredged Material-Obtain representative samples from the proposed dredge area at the Atterberg limits, in situ water content, consistency, density, grain size and depth that is representative of the soils and is significant to the design of geotextile containers for fine grained dredged material. The size and number of samples required is dependent upon the number of tests to be performed. Samples should be representative of the bulked dredged material density, water content, and consistency obtained in the geotextile container after the dredging and placement operation. 8. Procedure 8.1 Geotextile containers provided by the manufacturer are constructed by sewing one or more geotextile layers of geotextile together to form a container 45 inches inside circumference and 64 inches long as shown in Fig. 1. A selvedged edge is provided along the circumference of the container opening. Eight 1/2 inch diameter metal grommets are evenly spaced about one inch from the selvedged edge. Fabric seams are constructed by two double lock stitches to contain the dredged material, as it would be in the prototype. 8.2 Pre-wet the geotextile container by soaking the geotextile in pre-filtered water from the proposed dredge area. Do not use distilled water or water from another source. 8.3 Attach the wet geotextile container to the sheet metal pipe with 3/8 inch galvanized bolts, washers and nuts through the eight evenly spaced metal grommets as shown in figure 1. The bottom of the container should have a clearance of about 6 to 8 inches above the floor of the platform to accommodate removal the aluminum collection pans as they fill with sediment and water. 8.4 After the soaked geotextile container has drained of free water, a dry shallow 3 inch deep, 24 inch diameter aluminum metal collector pan (Hot water heater drip pan) is placed under the geotextile container to collect water and sediment by gravity flow. 8.5 Obtain about 150 to 190 liters (40 to 50 gallons) of the site specific dredged material in a 208 liter container (55 gallon). Thoroughly agitate the dredged materials with the stirrer for one minute to mix in free decant water to obtain a uniform consistency that would be representative of dredged material after excavation and placement. Immediately pour this mix through a funnel attached to the geotextile container and start the stopwatch simultaneously.

5 8.6 As the shallow aluminum pans fill about half full (about 3 gallons) with water and sediment they should be removed and the time and quantity recorded. The water and sediment sample should then be carefully placed, with all visible sediment, in approved clean glass containers marked with the time, quantity and order in which they were collected and recorded. 8.7 Water and sediment should be collected from the drainage of the dredged material in the shallow aluminum pans for about one week or until drainage has slowed to less than one inch depth in the pan per day or 24 hours. This completes the filtrate sample collection phase of the test. 8.8 At the completion of the sample collection, agitate the collected filtrate in each container with a stirrer until the mixture is uniformly mixed. After one minute of mixing, obtain a depth-integrated suspended solids sample from the mixture while continuing the agitation. NOTE 5-With the sampler specified in 6.4, a rate of sampling that requires 30 s to reach the bottom of the container and 30 s to return to the surface is ideal. This sampling procedure allows collection of a sample over the full depth of the mixture. 8.9 Place a glass fiber filter disk either on a membrane filter apparatus or in the bottom of a suitable Gooch crucible. Apply a vacuum and wash the disk with three successive 20-ml portion of distilled water. Continue suction to remove all traces of water from the disk Carefully remove the filter disk from the membrane filter apparatus and transfer to an aluminum or stainless steel planchet. If a Gooch crucible is used, remove the crucible and filter disk combination Dry the filter disk for at least 1 hour in an oven at 103 to C Store in a desiccator until cooled to room temperature Weigh the filter disk to an accuracy of g Place the filter disk in the membrane filter apparatus and return it or the Gooch crucible to the vacuuming and filtering apparatus Under the vacuum, filter the sample of water collected in Repeat 8.9 through Calculation 9.1 Calculate total suspended solids, as follow: (A - B) x 1000 S s = (1) C where: S s = suspended solids, ppm, A = weight of dry filter plus dry residue, and B = weight of dry filter, and C = sample volume of suspended material, ml

6 9.2. Calculate the flow rate, F DM, of the dredged material sediment and water for each sample collected for the geotextile container using Eq 2: Q p F DM = (2) t p where: Q p = Quantity of dredged material sediment and water collected in the aluminum pans for each sample t p = time measured in minutes for each sample collected Correct the flow rate to 20 0 C using Eq 3: F DM U T F 20 o C = U 20 o C where: U T ratio of viscosity of water at temperature T to = viscosity of water at 20 o C (see Fig. 2) o U 20 C 10. Report 10.1 The report of total suspended solids and flow rate should include the following information: State that the specimen were tested as directed in this test method. Describe the type of geotextile and seams tested and the sampling method used, The number of specimens tested and the direction(s) tested (if applicable), The type of dredged material, initial volume, weight, and height of material used and any data showing pertinent physical properties of the dredged material soil such as gradation curve, Atterberg limits, in situ moisture content, density, consistency, depth of sample, bulking factors, etc., Complete test data including temperature of the water, recorded flow rates, length of test, and suspended solids content for each dredged material and water sample collected and total average values for all tests A statement of any deviation from the described test method. 11. Precision and Bias 11.1 Precision-The precision of the procedure in this test method for measuring suspended solids and flow rate for geotextile containers for a dredged material containment systems is being established Bias-The procedure in this test method for measuring suspended solids and flow rate of a geotextile container system may be bias because of different geotextile

7 container geometries, container surface area, container volume, type of dredged material, or whether the container is submerged or not submerged. The test method described is simply an index test to determine relative difference in flow rate and suspended solids with the use of various geotextile systems and various types of dredged materials. The sediments determined for submerged containers would be much less than for non-submerged containers, because the pressure gradient and flow rate is very small for submerged containers, and is caused only by the slow release of pore water pressure during sedimentation and consolidation of the dredged material. 12. Keywords 12.1 flow rate; suspended solids; geotextile container; dredged material; contaminated dredged material; 1 This proposed test method will be under the jurisdiction of ASTM Committee D-35 Geosynthetics and is the direct responsibility of Subcommittee D on Permeability and Filtration and ASTM Section D on Navigation Dredging. 2 The definition for "dredged material" is being considered in ASTM Section D on Navigation Dredging May 20, Annual Book of ASTM Standards, Vol Annual Book of ASTM Standards, Vol Available from American Public Health Association (APHA), 1015 Eighteenth St. NW, Washington, DC The US DH-48 integrated water sampler has been found to be satisfactory. It is available from the Federal Inter-Agency Sedimentation Project, St. Anthony Falls Hydraulic Laboratory, 3rd Avenue S.E., Minneapolis, NM 55414

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