RS-13-009, Clinton, Unit 1, Updated Safety Analysis Report, Revision 15, Chapter 2 - Site Characteristics, Figures 2.5-1 Through 2.5-299
| ML13016A312 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 01/10/2013 |
| From: | Exelon Generation Co |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| RS-13-009 | |
| Download: ML13016A312 (336) | |
Text
Triaxial Compression Test Unit CLINTON POWER STATION UPDATED SAFETY ANALYSIS REPORT Figure 2.5-299 Sheet 1 of 2 UNCONFINED COMPRESSION AND TRIAXIAL COMPRESSION TESTS (METHOD)
NOTES FOR FIGURE 2.5-299 Methods of Performing Unconfined Compression and Triaxial Compression Tests The shearing strengths of soils are determined from the results of unconfined compression and triaxial compression tests. In triaxial compression tests the test method and the magnitude of the confining pressure are chosen to simulate anticipated field conditions.
Unconfined compression and triaxial compression tests are performed on undisturbed, or remolded samples of soil, approximately six inches in length and two and one-half inches in diameter. The tests are run either strain-controlled or stress-controlled. In a strain-controlled test the sample is subjected to a constant rate of deflection and the resulting stresses are recorded. In a stress-controlled test the sample is subjected to equal increments of load with each increment being maintained until an equilibrium condition with respect to strain is achieved.
Yield, peak, or ultimate stresses are determined from the stress-strain plot for each sample and the principal stresses are evaluated. The principal stresses are plotted on a Mohr's circle diagram to determine the shearing strength of the soil type being tested.
Unconfined compression tests can be performed only on samples with sufficient cohesion so that the soil will stand as an unsupported cylinder. These tests may be run at natural moisture content or on artificially saturated soils.
In a triaxial compression test the sample is encased in a rubber membrane, placed in a test chamber, and subjected to a confining pressure throughout the duration of the test. Normally, this confining pressure is maintained at a constant level, although for special tests it may be varied in relation to the measured stresses. Triaxial compression tests may be run on soils at field moisture content or on artificially saturated samples.
The tests are performed in one of the following ways: Unconsolidated-undrained: The confining pressure is imposed on the sample at the start of the test. No drainage is permitted and the stresses which are measured represent the sum of the intergranular stresses and pore water pressures. Consolidated-undrained: The sample is allowed to consolidate fully under the applied confining pressure prior to the start of the test. The volume change is determined by measuring the water and/or air expelled during consolidation. No drainage is permitted during the test and the stresses which are measured are the same as for the unconsolidated-undrained test. Drained: The intergranular stresses in a sample may be measured by performing a drained, or slow, test. In this test, the sample is fully saturated and consolidated prior to the start of the test. During the test, drainage is permitted and the test is performed at a slow enough rate to prevent the buildup of pore water pressures. The resulting stresses which are measured represent only the intergranular stresses. These tests are usually performed on samples of generally non-cohesive soils, although the test procedure is applicable to cohesive soils if a sufficiently slow test rate is used.
An alternate means of obtaining the data resulting from the drained test is to perform an undrained test in which special equipment is used to measure the pore water pressures. The differences between the total stresses and the pore water pressures measured are the intergranular stesses.
CLINTON POWER STATION UPDATED SAFETY ANALYSIS REPORT Figure 2.5-299 Sheet 2 of 2 UNCONFINED COMPRESSION AND TRIAXIAL COMPRESSION TESTS (METHOD)