A new unsaturated direct shear apparatus for measuring shear strength of unsaturated soils Part 1

2010 ◽  
pp. 665-670
Author(s):  
E Hefzi ◽  
S Yasrebi ◽  
A Mirzaii
Keyword(s):  
Shear Strength ◽  
Unsaturated Soils ◽  
Direct Shear ◽  
Direct Shear Apparatus

Determination of the shear strength parameters of an unsaturated soil using the direct shear test

1988 ◽  
Vol 25 (3) ◽  
pp. 500-510 ◽  
Author(s):  
J. K. M. Gan ◽  
D. G. Fredlund ◽  
H. Rahardjo
Keyword(s):  
Shear Strength ◽  
Unsaturated Soils ◽  
Testing Procedure ◽  
Direct Shear ◽  
Shear Tests ◽  
Direct Shear Tests ◽  
Wide Range ◽  
Practical Engineering ◽  
Direct Shear Apparatus

Multistage direct shear tests have been performed on saturated and unsaturated specimens of a compacted glacial till. A conventional direct shear apparatus was modified in order to use the axis-translation technique for direct shear tests on unsaturated soils. The soil can be subjected to a wide range of matric suctions. The testing procedure and some typical results are presented. Nonlinearity in the failure envelope with respect to matric suction was observed. Suggestions are made as to how best to handle the nonlinearity from a practical engineering standpoint. Key words: shear strength, unsaturated soils, negative pore-water pressures, soil suction, direct shear.

A method for determination of ϕb for statically compacted soils

1996 ◽  
Vol 33 (2) ◽  
pp. 272-280 ◽  
Author(s):  
S Y Oloo ◽  
D G Fredlund
Keyword(s):  
Shear Strength ◽  
Unsaturated Soils ◽  
Direct Shear Test ◽  
Shear Test ◽  
Strength Parameter ◽  
Direct Shear ◽  
Compacted Soils ◽  
Shear Strength Parameter ◽  
Direct Shear Apparatus

The unsaturated shear strength parameter, ϕb, is usually determined using triaxial of direct shear apparatus that have been modified to allow for the control and (or) measurement of pore-air and pore-water pressures. A fairly high level of expertise is required for the characterization of ϕb using these modified apparatus. A simple procedure for determining ϕb for statically compacted soils at different water contents is presented along with a method of analysis. The tests can be performed on a conventional direct shear apparatus. The unsaturated shear strength parameter, ϕb, obtained using the proposed procedure is shown to be comparable to that obtained using the modified direct shear test. Since the proposed procedure utilizes standard laboratory direct shear equipment and takes a relatively short time to complete, it offers an easy and convenient alternative for the determination of ϕb for statically compacted soils. Key words: shear strength, matric suction, unsaturated soils, statically compacted soils, direct shear test.

scholarly journals Modelling shear strength of compacted soils

2019 ◽  
Vol 92 ◽  
pp. 15007
Author(s):  
Sam Bulolo ◽  
Eng Choon Leong
Keyword(s):  
Shear Strength ◽  
Unsaturated Soils ◽  
Soil Mechanics ◽  
Published Data ◽  
State Variables ◽  
Compacted Soils ◽  
Earth Structures ◽  
Unsaturated Soil Mechanics ◽  
Coulomb Failure Criterion ◽  
Direct Shear Apparatus

Compacted soils constitute most engineering projects such as earth dams, embankments, pavements, and engineered slopes because of their high shear strength and low compressibility. The shear strength of compacted soils is a key soil parameter in the design of earth structures but it is seldom determined correctly due to their unsaturated state. The shear strength of compacted soils can be better evaluated under the framework of unsaturated soil mechanics. Saturated and unsaturated tests were conducted on compacted specimens using conventional direct shear apparatus under constant water content condition. Tests were conducted at different water contents and net normal stresses. The main objective of this study is to develop a shear strength model for compacted soils. Initial matric suction was measured before the test using the filter paper method. The two-stress state variables together with the extended Mohr-Coulomb failure criterion for unsaturated soils were used to obtain a lower bound model of the shear strength. The model was demonstrated using published data.

A Modified Osmotic Direct Shear Apparatus for Testing Unsaturated Soils

2012 ◽  
Vol 36 (1) ◽  
pp. 20120092 ◽  
Author(s):  
A. Hamidi ◽  
G. Habibagahi ◽  
M. Ajdari
Keyword(s):  
Unsaturated Soils ◽  
Direct Shear ◽  
Direct Shear Apparatus

Study on Shear Strength Experiments Base on the Modified Direct Shear Apparatus for Unsaturated Soils

2013 ◽  
Vol 438-439 ◽  
pp. 1176-1180 ◽  
Author(s):  
Gao Feng Chen ◽  
Ying Fa Lv ◽  
Zhi Huai Huang ◽  
Yan Chang
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Moisture Content ◽  
Friction Angle ◽  
Soil Samples ◽  
Direct Shear ◽  
Shear Strength Parameters ◽  
Strength Parameters ◽  
General Internal ◽  
Direct Shear Apparatus

The unconsolidated-undrained fast shear tests of saturated-unsaturated remolded soil samples under different moisture content which is 1.1%, 10.1%, 14.9%, 19.9%, 24.2%, 29.9%, 37.7% respectively, and normal stress which is 50kPa, 100kPa, 200kPa, 300kPa, 400kPa respectively, were studied by the modified SDJ-1-type strain direct shear apparatus and U.S. Lab VIEW data acquisition system. The shear strength parameters of unsaturated soil samples, i.e. general cohesion and general internal friction angle were obtained based on Mohr-Coulomb strength theory. The test results showed that the general cohesion firstly increased and then reduced with the moisture content increasing, and the general internal friction angle increased with the moisture content decreasing. The function between the general shear strength parameters and the moisture content was studied. The concept of general shear strength parameters was proposed in the paper, and would provide a simple and practical method to obtain the strength parameters for engineering practice.

scholarly journals Effect of temperature on the shear strength of soils and the soil–structure interface

2016 ◽  
Vol 53 (7) ◽  
pp. 1186-1194 ◽  
Author(s):  
Neda Yavari ◽  
Anh Minh Tang ◽  
Jean-Michel Pereira ◽  
Ghazi Hassen
Keyword(s):  
Shear Strength ◽  
Soil Structure ◽  
Shear Behaviour ◽  
Effect Of Temperature ◽  
Temperature Control System ◽  
Direct Shear ◽  
Ultimate Shear Strength ◽  
Direct Shear Tests ◽  
Direct Shear Apparatus ◽  
Concrete Interface

In the present work, the shear behaviour of soils and the soil–concrete interface is investigated through direct shear tests at various temperatures. A conventional direct shear apparatus, equipped with a temperature control system, was used to test sand, clay, and the clay–concrete interface at various temperatures (5, 20, and 40 °C). These values correspond to the range of temperatures observed near thermoactive geostructures. Tests were performed at normal stress values ranging from 5 to 80 kPa. Results show that the effect of temperature on the shear strength parameters of soils and the soil–concrete interface is negligible. A softening behaviour was observed during shearing of the clay–concrete interface, which was not the case with clay specimens. The peak strength of the clay–concrete interface is smaller than the ultimate shear strength of clay.

Application of suction stress for estimating unsaturated shear strength of soils using direct shear testing under low confining pressure

2010 ◽  
Vol 47 (9) ◽  
pp. 955-970 ◽  
Author(s):  
Byeong-Su Kim ◽  
Satoru Shibuya ◽  
Seong-Wan Park ◽  
Shoji Kato
Keyword(s):  
Shear Strength ◽  
Unsaturated Soils ◽  
Confining Pressure ◽  
Direct Shear ◽  
Shear Testing ◽  
Soil Water Retention ◽  
Overburden Pressure ◽  
Suction Stress ◽  
Saturated State ◽  
Direct Shear Testing

The primary objective of this study is to evaluate effects of suction on shear strength of unsaturated soils under low confining pressure and to examine the relationships between suction, shear strength behavior, and volumetric deformation using newly developed direct shear testing equipment for compacted weathered granite soils. The soil-water retention curves (SWRCs) of unsaturated soils were obtained under various overburden pressures. To analyze test results from the direct shear test under unsaturated conditions, a new method, suction stress–SWRC method (SSM), is proposed to determine the suction value for each overburden pressure and the suction stresses. As a result, it has been found that the stress states at the peak shear strength point are on the same failure line for the saturated state when the suction stress is treated as a component of confining pressure. The relationship between stress ratio and dilatancy for the saturated state can be extended to the unsaturated state. It is also noted that the estimated unsaturated shear strengths using the SSM agree well with the measured values from laboratory testing.

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