Geotechnical Engineering Circular No. 9 Design, Analysis, and Testing of Laterally Loaded Deep Foundations that Support Transportation Facilities
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Soldier Rev B
| 3.3.4 Laboratory Testing Laboratory tests are used to estimate geotechnical parameters of soils and rock for use in laterally loaded deep foundation analyses. Index testing consisting of sieve tests (ASTM D) and Atterberg limit determination (ASTM D) should be performed on recovered samples to verify field classifications and aid in characterization of subsurface conditions. Data regarding the gradation of coarse grained soils fines content, percentage of fine or coarse grains, etc) should be considered when correlating engineering parameters for such soils. This is discussed in more detail in subsequent sections. Tests for undrained shear strength of cohesive soils and unconfined compressive strength of rock should also be performed. The undrained shear strength, S u , is a key design parameter used in the design of deep foundations in cohesive soils. Several in-situ tests can be used to estimate this parameter however, laboratory tests are more commonly performed and are often more economical. Laboratory tests for estimating the undrained shear strength of cohesive soils must be performed only on undisturbed samples. The most common laboratory tests to estimate the undrained shear strength of soils are the unconfined compression (UC) tests (ASTM D, the consolidated-undrained (CU) triaxial test (ASTM D, and the unconsolidated-undrained (UU) triaxial test (ASTM D. The CU and UU tests are preferred to the UC tests because the use of confining pressures more closely models the in-situ condition. Descriptions of these tests and the interpretation of UU and CU test results can be found in detail in Chapter 5 of GEC 5 (Loehr et al. 2016). 38 The compressive strength of intact rock (q u or σ ci ) can be evaluated using the unconfined compressive strength test that is conducted on intact rock core specimens (ASTM D. In this test, rock specimens of regular geometry, generally rock cores, are used. After the rock core specimen is cut to a length-to- diameter ratio between 2.5 and 3.0 and the specimen ends are machined-flat, the specimen is placed in a loading frame and loaded. Unconfined compression tests can be used to determine the deformation properties of the intact rock, but correlations with rock mass classifications are needed to estimate the deformation properties of the fractured and weathered rock mass. Discussion on the use of these and other tests in relation to the development of geotechnical parameters for the analysis of laterally loaded piles/shafts is included in subsequent sections. Download 6.03 Mb. Share with your friends:
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