Consolidation test

Consolidation tests are made on saturated silts and clays to determine the rate of volume change under constant load. 

Consolidation tests are made on undisturbed samples whose water content, specific gravity and initial void ratio have been determined. Static loads are instantaneously applied, and maintained until consolidation has decreased to negligible amounts. Consolidation versus time data are accumulated during this period. Data from one of a series of increasing loads are plotted to give a curve such as shown in Figure 2.9. 

A 20-foot-thick clay stratum is overlain by several feet of sand, and underlain by a thick deposit of coarse to fine sand. Laboratory consolidation tests show Cv = 0.02in /minute, for the proposed future loading conditions. Estimate the time for 90% consolidation. 

A site consists of 66 feet of organic, clayey silt having high plasticity (OH soil) which is to be consolidated for eventual placement of large oil storage tanks. The soil is underlain by mixed strata of sand and silt. Consolidation tests have given, at loads equivalent to 3000 pounds per square... 

In the cement concrete industry the recommended practice is to consolidate low slump mixes by vibration and high slump mixes with hand tools. For example, ASTM Method C 192 (6) specifies consolidating test specimens by vibration if the slump is less than 1 in. Relationships between workability and ease of placing sand-asphalt-sulfur mixes are being evaluated on various field projects to assess the workability requirements for mix placement with various types of equipment. 

Direct measurements of permeabilities in unconsolidated marine sediments are difficult, and only few examples are published. They confine to measurements on discrete samples with a specially developed tool (Lovell 1985), to indirect estimations by resistivity measurements (Lovell 1985), and to consolidation tests on ODP cores using a modified medical tool (Olsen et al. 1985). These measurements are necessary to correct for the elastic rebound (MacKillop et al. 1995) and to determine intrinsic permeabilities at the end of each consolidation step (Fisher et al. 1994). In Section 2.4.2 a numerical modeling and inversion scheme is described which estimates permeabilities from P-wave attenuation and dispersion curves (c.f. also section 3.6). 

The conclusion of excellence, however, is reserved for consolidants dissolved in polar solvents. When toluene was used as the solvent, very little adhesive quality remained for AYAT and Acryloid B72. The use of toluene-ethanol as solvent reduced the shear strength for Butvar B98 by a relatively small amount, compared to ethanol alone as the solvent. These results agree with previous consolidation tests, in which the improvement factor tended to be larger for polar solvents than for nonpolar solvents (12), The poor adhesion of systems with nonpolar solvents may in part result from the superior penetration of nonpolar solvents, leaving little or no adhesive on the surfaces to be bonded. 

Towhata, 1., Kuntiwattanakul, P., Seko, I. Ohishi, K. 1993. Volume change of clays induced by heating as observed in consolidation tests. Soils and Foundations 33(4) pp. 170-183. 

We assume mesoscale and microscale domains are periodic (Figure 5). Let ar , and jc be coordinate systems defined in macro-domain 2o, meso-domain Qi and micro-domain If we perform a laboratory seepage/consolidation test on a typical Japanese bentonite, Kunigel VI, the macroscale specimen is of scale lO m, the mesoscale quartz grains are of lO m, and the microscale clay minerals are of 10 m. So, we estimate the scale factor =10 , and introduce the relations x = x°/z, x = x /e. 

Specimens that require more advanced test techniques (i.e., triaxial and consolidation test) are typically sent to shore-based laboratories. Samples for these tests are selected on... 

Laboratory tests can be classified into two groups (1) shipboard testing including Torvane, laboratory miniature vane shear (ASTM D4648), pocket penetrometer, and fall cone penetrometer and (2) shore-based tests, which includes the above as well as triaxial tests (ASTM D4767) direct simple shear, dynamic, and cyclic tests, consolidation tests (ASTM D4186, ASTM D2435) and the usual array of index property tests, and special tests appropriate... 

The parameters used in defining the consolidation characteristics of a soil are best illustrated with reference to a laboratory consolidation test. The test can be conducted either with or without back pressure. Use of back pressures insures that the sample is completely saturated. A schematic illustration of a back pressure consolidation test cell is... 

The existing state of consolidation in marine soils can also be predicted by use of a non-desfructive measurement technique (Richards and Chaney, 1997). Using this technique void ratio (e) versus log o relationships can be determined directly. A flowchart of the process is presented in Figure 6.17. Results of the sedimentation consolidation curve from both the nondestructive method and the conventional consolidation test is presented in Figure 6.18 for a site in the Bauer Deep, east of fhe East Pacific Rise and west of Callao. 

To extrapolate a field virgin curve from the laboratory consolidation curve, Schmertmann (1955) provided alternate methods to determine the preconsolidation pressure (1) from water content data, (2) from the void ratio reduction pattern in a given consolidation test. 

Permeability can also be determined from the normal consolidation test. The permeability of a saturated sample undergoing consolidation under a load is used to model the dissipation of pore pressure with time (Terzaghi, 1925,1943). The coefficient of permeability (k) is a function of the coefficients of consolidation (Q) and volume compressibility (mj which arise from one-dimensional consolidation theory. 

Comparison of permeability values measured in the laboratory, and computed from consolidation tests have been reported by Nickerson (1978) and Olsen and Daniel (1979). In addition, Nickerson and Olsen and Daniel both show that the direct determination of permeability gives higher values than back-calculating values from consolidation tests. Nickerson suggests that the discrepancy between the direct determination of permeability in the laboratory and back calculated from the consolidation test are due to the variation of hydraulic gradients and/or the formation of a filter cake at the sediment-porous stone interface during consolidation. Olsen and Daniel (1979) attribute at least part of the discrepancy to the fact that Terzaghi s consolidation theory makes no adjustment for the structural viscosity (creep) of the soil. However permeability derived from one-dimensional consolidation tests may provide sufficiently accurate information for preliminary analyses. 

Schmertmann 1. ICUtriax. i e Conduct consolidation test and Assumes that strength versus water content relationships and consolidation curves for normally consolidated clays will always be parallel. In addition appreciable errors in strer th may result from a small error in fixing the slope of the field strength curve. Other problems are based on predicting Schmertmann (1956)... 

B. Pushed Driven Pushed clay 0.71 0.99 0.71 0.75 samples than the conventional wire-line percussion method Observed that SHANSEP is very sensitive to quality of consolidation test samples... 

Results of consolidation tests on NC sediments when plotted as the log of the effective stress (o ) versus void ratio (e) resulted in a straight line. 

For the first method, it has been foimd most realistic to use the constrained deformation modulus (m) as determined from the reloading curve in the consolidation test. In the second method the sum of initial and consolidation settlements are calculated using E = 150 S and t) = 0.1. The relationship is obtained from Butler (1975) by the back-calculation of actually measured values. The consolidation settlement is then found by subtracting the initial settlement. 

Imai, G. 1979. Development of a new consolidation test procedure using seepage forces. SoUs and Foundation, 19(3) 45-60. 

Soil deformation One-dimensional and compression BS 1377 tests and consolidation tests ... 

Strength and compressibility parameters may be assessed from triaxial and consolidation tests results carried out on extruded samples that have been reconstituted to specified compaction requirements i.e. proctor test requirements. Collapsed type settlement may be estimated by repeating the consolidation test on saturated samples for each load increment. 

Particle contact relations evolution analysis before and after the consolidation test... 

After the consolidation test, the particles has rearranged, which makes some particles contact with each other and the pores size become smaller. And the pore size distribution... 

Oedometer Consolidation Test Apparatus - Oedometer Cell... 

Consolidation tests are commonly performed to (1) evaluate the compressibOity of soil samples for the calculation of foundation settlement (2) investigate the stress history of the soils at the boring locations to calculate settlement as weU as to select stress paths to perform most advanced strength tests (3) evaluate elastic properties from measured bulk modulus values and (4) evaluate the time rate of settlement. Consohdation test procedures also can be modified to evaluate if foundation soils are susceptible to coUapse or expansion, and to measure expansion pressures under various levels of confinement. Consohdation tests include incremental consohdation tests (which are performed at a number of discrete loads) and constant rate of strain (CRS) tests where load levels are constantly increased or decreased. CRS tests can generally be performed relatively quickly and provide a continuous stress-strain curve, but require more sophisticated equipment. 

Ichikawa Y, Kawamura K, Theramast N, Kitayama K (2(X)4) Secondary and tertial consolidation of bentonite clay consolidation test, molecular dynamics simulation and multiscale homogenization analysis. Mech Mater 36 487-513... 

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