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Shear Strength of Soils by Triaxial Test
Published in Bashir Ahmed Mir, Manual of Geotechnical Laboratory Soil Testing, 2021
Generally, a triaxial compression test is applicable to all types of soils. A triaxial shear test can be conducted on undisturbed saturated clayey soils or reconstituted soil specimen for determination of undrained shear strength as per requirement. However, neither undisturbed soil specimen can be collected nor compaction test can be conducted in case of cohesionless (sandy soils). Therefore, a relative density test (Test No. 10) is a pre-requisite for preparation of a remolded specimen for sandy soils for conducting of triaxial shear test, whereas the compaction test (Test No. 9) is a pre-requisite for remolded c-ϕ soils and c-soils.
Effects of frequency and CSR on dynamic properties of marine clay in drained condition
Published in Marine Georesources & Geotechnology, 2022
Hao Liu, Si Yan, Jie Yin, Jiang-Qiao Fan, Yong-Hong Miao, Fan-Bo Zhou
Marine clay was obtained from a depth of about 2.5 m below the surface. The sampling site is located at Lianyungang Port, Jiangsu province, China, by the coastline of the Yellow Sea. The groundwater table is about 1.5 m deep. Table 1 shows the basic physical properties of marine clay. The natural water content of the test sample was in the range of 46.6% to 48.5% per ASTM D2216, and the unit weight γ ranged from 17.9 to 18.4 kN/m3 per ASTM D7263. The specific gravity of the sample measured according to ASTM D854 was 2.71. Atterberg limits were measured following ASTM D4318. LL and plastic limit (PL) were 52.9 and 28.1, respectively, with a related plasticity index (PI = LL − PL) of 24.8. Figure 1 shows the grain size distribution curve, where there is more than 50% of grain with a particle size finer than 0.075 mm. After referring to the unified soil classification system, the soil sample was classified as high plastic clay (CH). The undrained shear strength of Lianyungang soft soil measured by the triaxial shear test was 21.85 kPa and the sensitivity was 3.47, similar to existing studies (Guo et al. 2022a, 2022b).
Prediction of the shear strength parameters from easily-available soil properties by means of multivariate regression and artificial neural network methods
Published in Geomechanics and Geoengineering, 2022
Mojtaba Mohammadi, Seyed Mahmoud Fatemi Aghda, Mehdi Talkhablou, Akbar Cheshomi
The soil samples were obtained from Isfahan city. Geotechnical databases of the Isfahan city will be used to investigate the relationship between the SS parameters and other properties of the soils of the region. The depths of soil samples are mainly lower than 100 cm. The laboratory tests have been conducted according to ASTM (1997) specifications. More than 300 experiments have been done on about 108 samples. Figure 1 presents the sampling locations. The experiments included the triaxial shear test (TST), Atterberg limits and determination of dry density (D) and percentages of gravel (G), sand (Sa), silt (Si), and clay (C). Regarding the same resource of soils (soil deposit of the Zayandeh – Rood), the shape characteristics, consolidation history, and state of the ground are the same for all samples. Also, grain size distribution and Atterberg limits tests are more important parameters for SS properties (Kayadelen et al. 2009, Khanlari et al. 2012) and are used as input parameters for SS prediction.
The effect of spudcan footprints on the vertical bearing capacity of adjacent pile foundations
Published in Ships and Offshore Structures, 2021
Chao Liang, Run Liu, Haiyang Zhang, Chengfeng Li, Yu Yuan, Tianming Cao
The confining pressure in the test is 100 and 150 kPa. The unloading ratio R is defined as follows: where σ3 is the confining pressure and Δσ is the change value of the confining pressure after consolidation is complete. When the unloading ratio Δσ = 0, the test is equivalent to the conventional triaxial shear test. During the test, the saturated soil sample was first consolidated under a predetermined confining pressure. After the consolidation was complete, the confining pressure was reduced to different target values according to the unloading ratio R. After the pore pressure was stable, a shear test was performed. Three sets of parallel tests were conducted for each test. The deviatoric stress when the axial strain of the test soil reached 15% was selected as the failure strength. The ratio of the soil failure strength under the unloading triaxial shear test to the conventional triaxial shear test is used as the strength residual rate fr, namely, where τi is the unloading triaxial shear strength value at different unloading ratios and τ0 is the conventional triaxial shear strength value. The test results are shown in Figure 5.