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00:04 Soil moisture-density relationship test is a laboratory determination of the maximum dry unit weight and optimum water content for soil types used as engineered fill for earth embankments and building pads (Standard Proctor Test, ASTM D698 / AASHTO T 99), or surfaces where heavy wheel loads create dynamic forces (Modified Proctor Test, ASTM D1557 / AASHTO T 180).
The Sand Cone Test, Rubber Balloon Test and Nuclear Density Test are three common field tests that when compared to the laboratory Proctor test results, of the same soil, a ratio of percent compaction can be determined that is reliable and accepted by infrastructure design teams and regulatory authorities.
01:18 Sand Cone Test
Sand Cone Test is an accurate and reliable ASTM and AASHTO (ASTM D1556 / AASHTO T 191) test method that requires the use of a sand cone apparatus, such as the Gilson HM-100 Sand Cone Density Apparatus.
Simply stated, the test is carried out with the apparatus and sand. The weight of the sand-filled jar and the cone are determined. A small hole is excavated on site and the sand cone apparatus is placed over the hole and onto its base plate. The stopcock is opened to allow the sand to fill the hole.
The excavated soil, and the apparatus with the sand remaining in it are collected, recorded and calculated using appropriate ASTM test specifications (Soil Moisture Test ASTM D2216, D4643, D4944, or D4959 for the excavated soil) for specified density or percentage of a maximum density.
The PROS of the Sand Cone Test are its long history of accuracy and reliable, it does not require extensive training to perform or regulatory licensing for use, its cost effective, and equipment and materials are not hazardous.
The CONS are that the Sand Cone Test it requires 30 minutes or more to complete, nearby heavy equipment must pause during testing, it is generally limited to unsaturated soils, nor soft or friable soils, and all excavated material must be carefully recovered for accurate testing.
02:56 Rubber Balloon Test
With the Rubber Balloon Test (ASTM D2167 / AASHTO T 205 (withdrawn)) an on-site hole is excavated with the soil carefully collected and set aside. A balloon density apparatus, like the Gilson HM-66 (1/20ft³ (1,600ml) capacity, for soils with 1/2in (13mm) maximum particle size) or the HM-67 (1/13ft³ (2,230ml) capacity, for soils with particle size up to 1in (25mm)) Balloon Density Apparatus is positioned over the hole, but instead of using sand to measure volume, the calibrated water vessel is pressurized, forcing a rubber membrane into the excavation. Graduations on the vessel are read to determine the hole volume.
The PROS of the Rubber Balloon Test are its long history of accuracy and reliable. It does not require extensive training to perform or regulatory permitting for use, its cost effective, multiple tests can be performed without changing density media, and equipment and materials are not hazardous.
The CONS are that the Rubber Balloon Test requires 15 to 20 minutes to complete, balloon membranes can puncture during testing of soils with appreciable amounts of rock or coarse material, it is generally limited to soil in an unsaturated condition and is not recommended for soils that are soft or that deform easily, and all excavated material must be carefully recovered for accurate testing.
04:32 Nuclear Density Test
The Nuclear Density Test (ASTM D6938 / AASHTO T 310) measures soil density using a Nuclear Density Gauge that emits radioactive particles (Density - Cesium 137 (or other), Moisture Content - Americium 241) and a sensor (Geiger-Mueller detection circuitry) that receives the particles that are either reflected by the test material or passed through it.
The PROS of the Nuclear Density Test are density and moisture tests are complete in a few minutes, digitally accurate and repeatable tests, Nuclear Density Gauges can incorporate datalogging and location reporting functions, it is an optimum test method for large projects requiring many tests per day, density and moisture content are computed automatically by the Nuclear Density Gauge, and the test can be used for a wide range of soils.
The CONS of the Nuclear Density Test are Nuclear Density Gauges are expensive, there are multiple regulatory requirements that govern usage, transportation, and handling of nuclear material, including monitoring of Nuclear Density Gauge operators for exposure, operators require advanced safety training and certification, Nuclear Density Gauges can be sensitive to harsh environments, and readings are sensitive to excessive voids within the testing area.
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26 мар 2020
