Interpretation of the limits in shear strength in binary granular mixtures

2001 ◽  
Vol 38 (5) ◽  
pp. 1097-1104 ◽  
Author(s):  
Luis E Vallejo
Keyword(s):  
Shear Strength ◽  
Laboratory Tests ◽  
Relative Concentration ◽  
Frictional Resistance ◽  
Glass Beads ◽  
Rock Fragments ◽  
Structural Support ◽  
Granular Mixtures ◽  
The Stability ◽  
Natural Slopes

Many natural slopes and rockfill structures are made of a mixture of rock fragments and sand-size particles. To analyze the stability of such natural slopes and rockfills, a knowledge of how rock–sand mixtures develop their shear strength is needed. Laboratory tests conducted on mixtures of glass beads of two different sizes (5 and 0.4 mm) have indicated that their shear strength depends upon the relative concentration by weight of the large and small beads in the mixtures. If the concentration by weight of the large beads is greater than 70%, the shear strength of the mixtures is controlled by the frictional resistance of the large beads. If the concentration of the large beads is less than 40%, the shear strength of the mixtures is controlled by the frictional resistance of the small beads. If the concentration of the large beads is between 40 and 70%, the shear strength of the mixture is partially controlled by the frictional resistance provided by the large beads in the mixtures. These limits are very similar to those reported for rock–sand mixtures. To date, no explanation has been put forward to account for why these limits exist. This study presents an explanation for their existence. The explanation is based on the porosity developed by the mixtures and the type of structural support provided by the coarse and fine grains.Key words: shear strength, granular mixtures, porosity, fabric, compaction.

A Slope Failure in Swelling Clay

1973 ◽  
Vol 10 (3) ◽  
pp. 531-536 ◽  
Author(s):  
G. Kassiff ◽  
I. Alpan
Keyword(s):  
Shear Strength ◽  
Laboratory Tests ◽  
Slope Failure ◽  
Climatic Conditions ◽  
Expansive Clay ◽  
Bridge Abutment ◽  
Actual Field ◽  
The Stability ◽  
Short Time ◽  
Loss Of Strength

A recent heavy rainy season in the semiarid climatic conditions of northern and central Israel caused a number of slope failures of embankments and bridge abutments in expansive clay soils.Failure of a 9 m high slope of a bridge abutment is reported. The failure occurred owing to migration of moisture into the clay a short time after the slope was completed. Soil characteristics such as plasticity, swelling potential, and shear strength are presented and discussed. The stability of the slope was analyzed using Taylor's chart and strength parameters obtained from laboratory tests. It is concluded that failure occurred owing to substantial loss of strength following swelling of the clay. Results of laboratory tests for shear strength after saturation and swelling seem to correlate well with actual field conditions in this case.

Study on Influence of Unloading of Vacuum on Stability of Embankment Improved by Vacuum Combined with Preloading

2012 ◽  
Vol 178-181 ◽  
pp. 1688-1693
Author(s):  
Ji Fu Liu ◽  
Guan Feng An ◽  
Gang Zheng
Keyword(s):  
Shear Strength ◽  
Theoretical Analysis ◽  
Safety Factor ◽  
Laboratory Tests ◽  
Soft Clay ◽  
Undrained Shear Strength ◽  
Soft Ground ◽  
Analysis Laboratory ◽  
The Stability ◽  
Undrained Shear

In order to study influence of unloading of vacuum on stability of embankment whose soft ground is improved by vacuum combined with preloading, the change of effective stress of soft clay in the improved area is analyzed when vacuum is unloaded and the undrained shear strength of soft clay in the improved area after unloading of vacuum is deduced. Changes of undrained shear strength of soil and stability of embankment owing to unloading of surcharge are also analyzed for comparison. It is shown by theoretical analysis, laboratory tests and a project that the undrained shear strength of soft clay improved by vacuum combined preloading is decreased after unloading of vacuum and the stability of embankment after unloading of vacuum should be taken into account for design. Safety factor of stability of embankment increases after unloading of surcharge since decrease ratio of load of embankment is more than decrease ratio of undrained shear strength of clay.

Slope Stability Analysis under the Condition of Seepage

2012 ◽  
Vol 204-208 ◽  
pp. 241-245
Author(s):  
Yang Jin
Keyword(s):  
Finite Element Method ◽  
Shear Strength ◽  
Slope Stability ◽  
Negative Impact ◽  
Strength Reduction ◽  
Soil Slope ◽  
Failure State ◽  
Calculation Results ◽  
The Stability ◽  
Shear Strength Reduction

The stability of soil slope under seepage is calculated and analyzed by using finite element method based on the technique of shear strength reduction. When the condition of seepage or not is considered respectively, the critical failure state of slopes and corresponding safety coefficients can be determined by the numerical analysis and calculation. Besides, through analyzing and comparing the calculation results, it shows that seepage has a negative impact on slope stability.

scholarly journals Effect of Strength Anisotropy on the Stability of Natural Slopes

2021 ◽  
Vol 710 (1) ◽  
pp. 012025
Author(s):  
Magnus T Aamodt ◽  
Gustav Grimstad ◽  
Steinar Nordal
Keyword(s):  
Strength Anisotropy ◽  
The Stability ◽  
Natural Slopes

scholarly journals LABORATORY TESTING OF LEICA AT401 LASER TRACKER

2016 ◽  
Vol 56 (2) ◽  
pp. 88 ◽  
Author(s):  
Filip Dvořáček
Keyword(s):  
Laboratory Testing ◽  
Laboratory Tests ◽  
Angle Measurement ◽  
Distance Measurement ◽  
Additive Constant ◽  
Laser Tracker ◽  
Simple Test ◽  
Absolute Distance ◽  
Warm Up ◽  
The Stability

<p>This paper describes laboratory tests on a Leica AT401laser tracker. As the newer Leica AT402 model also uses the same firmware package, most of the results should also be valid for this device. First, we present the instrument’s firmware errors and the software used for testing. The ASME B89.4.19-2006 standard for testing laser trackers is briefly presented. The warm-up effect of the instrument is inspected with respect to both angle measurement and distance measurement. The absolute distance meter (ADM) is compared with a laboratory interferometer on a 30-meter long rail and also on a bench with automated movement of the carriage of the reflector. A time series of measurements for determining the additive constant is evaluated. A simple test of the stability of the distance measurement in field conditions is introduced. Most of the tests were carried out at the Research Institute of Geodesy, Topography and Cartography (RIGTC) and at the Faculty of Civil Engineering (FCE) of the Czech Technical University in Prague (CTU).</p>

An analysis of the stability of thawing slopes, Ellesmere Island, Nunavut, Canada

2000 ◽  
Vol 37 (2) ◽  
pp. 449-462 ◽  
Author(s):  
Charles Harris ◽  
Antoni G Lewkowicz
Keyword(s):  
Shear Strength ◽  
Pore Water ◽  
Active Layer ◽  
Factor Of Safety ◽  
High Arctic ◽  
Ellesmere Island ◽  
Sensitivity Analyses ◽  
Pore Water Pressures ◽  
Hot Weather ◽  
The Stability

Active-layer detachment slides are locally common on Fosheim Peninsula, Ellesmere Island, where permafrost is continuous, the active layer is 0.5-0.75 m thick, and summer temperatures are unusually high in comparison with much of the Canadian High Arctic. In this paper we report pore-water pressures at the base of the active layer, recorded in situ on two slopes in late July and early August 1995. These data form the basis for slope stability analyses based on effective stress conditions. During fieldwork, the factor of safety within an old detachment slide on a slope at Hot Weather Creek was slightly greater than unity. At "Big Slide Creek," on a slope showing no evidence of earlier detachment failures, the factor of safety was less than unity on a steep basal slope section but greater than unity elsewhere. In the upper slope, pore-water pressures were only just subcritical. Sensitivity analyses demonstrate that the stability of the shallow active layer is strongly influenced by changes in soil shear strength. Possible mechanisms for reduction in shear strength through time include weathering of soils and gradual increases in basal active layer ice content. However, we suggest here that soil shearing during annual gelifluction movements is most likely to progressively reduce shear strengths at the base of the active layer from peak values to close to residual, facilitating the triggering of active-layer detachment failures.Key words: detachment slides, Ellesmere Island, pore-water pressures, gelifluction.

Observations on some basal failures in sheeted excavations

1970 ◽  
Vol 7 (2) ◽  
pp. 136-144 ◽  
Author(s):  
V. Milligan ◽  
K. Y. Lo
Keyword(s):  
Shear Strength ◽  
Ground Water ◽  
Groundwater Level ◽  
Soil Conditions ◽  
Remedial Measures ◽  
Factors Influencing ◽  
Water Head ◽  
The Stability ◽  
Made In

In excavations below groundwater level, instability of the base may result from the inflow of water into the excavation. The most important factors influencing the stability are the ground water and detailed soil conditions at the site.Construction problems encountered in excavations in clay strata, underlain by pervious water bearing layers, are described. The remedial measures adopted in each case are also discussed. From a study of the observations made in the case records, it is suggested that excavation in intact clays may be carried out to depths exceeding that limited by the ratio of t/h = 0.5, where t is the distance from the bottom of the excavation to the top of the water bearing stratum, and h is the water head at the top of the water bearing stratum, provided that the clay is not disturbed during construction so that the shear strength of the clay is preserved.

Sign in / Sign up

Export Citation Format

Share Document