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Target Values of Compacted Gravel for Pipelines

A successful buried pipe installation depends on obtaining the proper soil support for the pipe. The amount of support depends on the level of compaction of the soil. A Target Value is used to evaluate the level of compaction of the soil. Typically, the Target Value is the percent compaction of the soil. To obtain the percent compaction, an in-place density test is compared to a laboratory test that determines the maximum dry density of the soil (e.g. percent standard Proctor). However, the density of gravel-size cohesionless materials used for pipe bedding, embedment, and backfill is difficult to measure in the field and in the laboratory. Materials such as pea gravel, crushed rock, and recycled concrete present unique measurement problems, particularly in pipeline trenches. For these materials, the Target Value can be a property of the soil that is more convenient to measure than density. Tests using devices to measure soil properties such as stiffness, modulus, or impact resistance are now available and can be used in combination with a Control Strip. A Control Strip is a test section that is compacted before construction begins and is used to establish control values that are used to evaluate the level of compaction. One of the measurement devices is selected and employed during the construction of the Control Strip and is used to establish a Control Strip Maximum (CSM) value. The CSM then serves as a reference for the Target Value. ASTM has recently adopted several such procedures to measure the in-place properties of soils that can be used to evaluate compaction. These include the Clegg Hammer, the GeoGauge, the Time Domain Reflectometer, the 18 lb Dynamic Cone Penetrometer, and the 5 lb Dynamic Cone Penetrometer. A Control Strip can also be used with devices that measure density, such as nuclear gauges, without establishing calibration curves necessary to get the exact value. In some circumstances, the Target Value could even be a wet density. For some cohesionless soils, determining the percent compaction (or the percent Relative Density) may still be the most appropriate method. A new ASTM procedure using a vibrating hammer has been developed to measure the maximum density of cohesionless soils. This test is intended to replace the vibrating table method and can be used to determine either percent compaction or percent Relative Density.

Language

  • English

Media Info

  • Media Type: Digital/other
  • Features: References;
  • Pagination: pp 491-500
  • Monograph Title: Pipelines 2011: A Sound Conduit for Sharing Solutions

Subject/Index Terms

Filing Info

  • Accession Number: 01380429
  • Record Type: Publication
  • ISBN: 9780784411872
  • Files: TRIS, ASCE
  • Created Date: Aug 21 2012 5:09PM