5.1 Information concerning magnitude of compression and rate-of-consolidation of soil is essential in the design of earth structures and earth supported structures. The results of this test method may be used to analyze or estimate one-dimensional settlements, rates of settlement associated with the dissipation of excess pore-water pressure, and rates of fluid transport due to hydraulic gradients. This test method does not provide information concerning the rate of secondary compression.
5.2 Strain Rate Effects:
5.2.1 It is recognized that the stress-strain results of consolidation tests are strain rate dependent. Strain rates are limited in this test method by specification of the acceptable magnitudes of the base excess pressure ratio during the loading phase. This specification provides comparable results to the 100 % consolidation (end of primary) compression behavior obtained using Test Method D2435.
5.2.2 Field strain rates vary greatly with time, depth below the loaded area, and radial distance from the loaded area. Field strain rates during consolidation processes are generally much slower than laboratory strain rates and cannot be accurately determined or predicted. For these reasons, it is not practical to replicate the field strain rates with the laboratory test strain rate.
5.3 Temperature Effects:
5.3.1 Temperature affects the rate parameters such as hydraulic conductivity and the coefficient of consolidation. The primary cause of temperature effects is due to the changes in pore fluid viscosity but soil sensitivity may also be important. This test method provides results under room temperature conditions, corrections may be required to account for specific field conditions. Such corrections are beyond the scope of this test method. Special accommodation maybe made to replicate field temperature conditions and still be in conformance with this test method.
5.4 Saturation Effects:
5.4.1 This test method may not be used to measure the properties of partially saturated soils because the method requires the material to be back pressure saturated prior to consolidation.
5.5 Test Interpretation Assumptions—The equations used in this test method are based on the following assumptions:
5.5.1 The soil is saturated.
5.5.2 The soil is homogeneous.
5.5.3 The compressibility of the soil particles and water is negligible.
5.5.4 Flow of pore water occurs only in the vertical direction.
5.5.5 Darcy's law for flow through porous media applies.
5.5.6 The ratio of soil hydraulic conductivity to compressibility is constant throughout the specimen during the time interval between individual reading sets.
5.5.7 The compressibility of the base excess pressure measurement system is negligible compared to that of the soil.
5.6 Theoretical Sol
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