Temporary stability of steep, noncemented and lightly cemented soil slopes

2015 ◽  
Vol 52 (9) ◽  
pp. 1374-1384
Author(s):  
Poul V. Lade ◽  
Jerry A. Yamamuro
Keyword(s):  
Shear Strength ◽  
Slope Stability ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Compression Tests ◽  
Shear Strength Parameters ◽  
Strength Parameters ◽  
Dense Sand ◽  
Soil Slopes ◽  
Access To Water

Many steep soil slopes are apparently stable beyond what is indicated by slope stability analysis. The mechanism of slope stability in dilating soils is explained in detail, and the development of shear strength in such soils is demonstrated by drained and undrained tests on dense sand. It is argued that appropriate shear strength parameters for analysis of slope stability in dilating materials describe the residual strength. It is explained how reliance on peak shear strength parameters is unsafe, because the component of shear strength created by the additional effective confining pressure caused by development of suction due to inhibited dilation can be exhausted by either access to water or by drying the soil. The fleeting phenomenon of apparent additional shear strength causes super-stability of the slope. Exhaustion of the soil’s capacity to dilate results in reduction of shear strength and instability of the steep slope. It is difficult to predict the time when the soil’s capacity to dilate is exhausted and when the consequent decline in shear strength occurs. This is because this decline occurs with access to water. This is demonstrated by triaxial compression tests on saturated and partly saturated, dilating specimens.

scholarly journals Triaxial Testing on Geogrid-reinforced Granular Soils

2021 ◽  
Vol 1200 (1) ◽  
pp. 012030
Author(s):  
Tigo Mindiastiwi ◽  
Po-Kai Wu ◽  
Agus Bambang Siswanto ◽  
Mukhamad Afif Salim
Keyword(s):  
Shear Strength ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Reinforced Soil ◽  
Deviatoric Stress ◽  
Granular Soils ◽  
Peak Shear Strength ◽  
Compression Tests ◽  
Soil C ◽  
Dense Sand

Abstract Laboratory triaxial compression tests were carried out to investigate the mechanical behavior of dense sand and geogrid-reinforced granular soils. The tested sand having its mean particle size (D50) equal to 0.6 mm was adopted. Three geogrids with different longitudinal and transverse nominal strengths were used. The dimensions of the cylindrical soil specimen were 70 mm (diameter) × 160 mm (height). The relative density was equal to 70% for all tests. The reinforced sand specimens with one or two geogrid layers were sheared under effective confining pressures (σ′3) equal to 50 kPa. The test results of unreinforced sand indicate the general stress-strain behavior of dense sand when sheared, whereas the deviatoric stress reaches its peak value, after which it gradually decreases to ultimate value (σ1 - σ3)ult. The difference of effective confining pressure indicates that the peak of deviatoric stress Δσd = (σ1 - σ3) increases with the increase in effective confining pressure (σ′3), while the peak principal stress ratio (σ′1/σ′3) decreases with the increase (σ′3). The friction angle (ϕ′)and cohesion (c′), defined by analytical and graphical methods for unreinforced sand. Geogrid as reinforcement increasing peak shear strength. The increasing peak shear strength is more pronounced with a higher number of geogrid and the geogrid with higher stiffness. Increased in confining stress inside reinforced soil mass (Δσ3R) can be interpreted by cohesive reinforced soil (CR).

scholarly journals Change of soil mechanical properties due to triaxial sample size

2019 ◽  
Author(s):  
Šarūnas Skuodis ◽  
Neringa Dirgėlienė ◽  
Ieva Lekstutytė
Keyword(s):  
Shear Strength ◽  
Sample Size ◽  
Triaxial Compression ◽  
Specimen Size ◽  
Compression Tests ◽  
Shear Strength Parameters ◽  
Strength Parameters ◽  
Soil Shear Strength ◽  
Confining Pressures ◽  
Triaxial Compression Tests

Triaxial test is widely used to determine the behaviour and strength parameters of soil. Several consolidated drained triaxial compression tests were performed on two specimen sizes of sand and clay. This article investigate and compares the influence of specimen size and scale effect on the soil shear strength. The tests results show that the shear strength parameters are influenced by the clay specimen size. The results indicate that the effect of triaxial clay sample size is more significant with higher confining pressures. The second type of tests carried out on sand samples shows that sample size doesn‘t influence the results of the shear strength. Author’s show that clay analyses can be significantly affected by the choice of the specimen size used to determine shear strength parameters.

Specimen size effects on behavior of loose sand in triaxial compression tests

2015 ◽  
Vol 52 (6) ◽  
pp. 732-746 ◽  
Author(s):  
Tarek Omar ◽  
Abouzar Sadrekarimi
Keyword(s):  
Shear Strength ◽  
Size Effects ◽  
Scale Effects ◽  
Triaxial Compression ◽  
Shear Banding ◽  
Specimen Size ◽  
Triaxial Tests ◽  
Compression Tests ◽  
Shear Strength Parameters ◽  
Strength Parameters

Triaxial tests are often used to determine the behavior and strength characteristics of soils without due attention to the differences in specimen size. Several drained and undrained monotonic triaxial compression shear tests are performed in this study on three different specimen sizes of the same sand to investigate the influence of specimen size and scale effect on sand compression and shear behavior. The behavior of a sand specimen is strongly influenced by shear banding and specimen boundary conditions, which are manifested as specimen size effects in the test results of this study. The measured sand compressibility and shear strength parameters are employed to describe scale effects, and investigate specimen size effects in liquefaction triggering analysis. The results show that while larger specimens exhibit a less compressible behavior during isotropic compression, larger shear strengths and effective friction angles are mobilized in the smaller specimens during shearing. A number of geotechnical analyses can be significantly affected by variations in strength parameters of the same soil determined from different specimen sizes. While using small size specimens for determining shear strength parameters might result in an unconservative design, a large specimen size provides a more accurate representation of different soil strength conditions and field deformations.

scholarly journals Experimental Investigation into Multistage versus Conventional Triaxial Compression Tests for a C-Phi Soil

2011 ◽  
Vol 90-93 ◽  
pp. 28-32
Author(s):  
Mohamed A. Shahin ◽  
Alice Cargeeg
Keyword(s):  
Shear Strength ◽  
Simple Procedure ◽  
Triaxial Compression ◽  
Stress Path ◽  
Compression Tests ◽  
Soil Behavior ◽  
Shear Strength Parameters ◽  
Strength Parameters ◽  
Conventional Triaxial Compression ◽  
Confining Pressures

The procedure for conventional triaxial compression (CTC) test requires three separate soil specimens to be examined to failure under different confining pressures so that Mohr-Coulomb (or stress path) failure envelope can be determined and soil shear strength parameters can be obtained. An alternative procedure is the multi-stage triaxial (MST) compression test, which requires only one soil specimen to be tested at three stages of shearing with different confining pressures. There are several advantages for using MST over CTC, which apart from fewer soil specimens, include less laboratory time consumption and reduced effects of heterogeneity among the specimens tested. However, it has been argued in the literature that the advantages of using MST may be compromised by its inability to obtain reliable soil behavior or accurate shear strength parameters. In this paper, the accuracy of MST compared to CTC is investigated for a c-phi soil, and a simple procedure that can be adopted to rectify the MST results is proposed.

Mechanical Properties of Bentonite-Sand Mixtures Under Triaxial Stress Condition

1994 ◽  
Vol 353 ◽  
Author(s):  
M. Umedera ◽  
A. Fujiwara ◽  
N. Yasufuku ◽  
M. Hyodo ◽  
H. Murata
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Water Content ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Strength Properties ◽  
Compression Tests ◽  
Optimum Water Content ◽  
Triaxial Compression Tests ◽  
Optimum Water

AbstractA series of triaxial compression tests is being conducted under the drained condition on bentonite and sand mixtures, known as buffer, in saturated and optimum water content states to clarify the mechanical properties of the buffer.It was found that the mechanical properties of bentonite and sand mixtures are strongly influenced by water and bentonite contents: shear strength in a saturated state is less than that in an optimum water content state; shear strength decreases rapidly with increasing bentonite content. Strength properties are much dependent on confining pressure.

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