i have done direct shear test on the low plasticity silt soil and in the result i have found value of cohesion,friction angle ,and mass density as well as bearing capacity.IS there any method to find the elastic modulus of the soil bybearing capacity or any other way through this test?
Dear Arsalan,
The elastic moduli (Tangent and Secant) can be obtained from any stress-strain plots (UCS, CBR, Triaxial etc.,). Since the failure planes are predefined in direct shear test, you will have difficulty in generalizing the linearized stress-strain portion. You can find some correlations (Refer to Geotechnique Journal, Canadian Geotechnical Journal and ASCE Journal of Geotechnical and GeoEnvironmental Engineering) relying on which you can get the modulus values. Be careful as these correlations may hold good for specific soil types (which is usually the case in most of these studies). Avoid taking data from dubious journals as their authenticity is highly questionable.
I would recommend you to take up a simple UCS test. The slope of the linearized portion of the stress-strain curve should yield elastic modulus. Having said that, if you have access to triaxial, rely on that as well. That will give you the confining effect on the resultant elastic modulus values.
Best Wishes...
Dear Arsalan..you can find detail about your request in the following textbook
Pavement Analysis and Design ..2nd edition 2004 by Huang Yang..if you wish i can forward a copy for you ..regards
Dear Arsalan,
If you have Poisson's ratio, then you can determine the Young's Modulus E from direct shear test. You can use this paper:
The Determination of Young's Modulus from the Direct Shear Test by D. K. J. Noonan, J. F. Nixon
http://www.nrcresearchpress.com/doi/abs/10.1139/t72-049#.WMZTQfLgSO1
Hi: during the shearing you are forcing the failure, which is far away from the elastic behaviour, and therefore, during shearing you are unlikely to determine a realistic value of elastic module. However, before shearing, when you apply the vertical initial stress and you measure the initial settlement, you can obtain a first approximation of the elastic modulus if you either know or estimate the Poisson's ratio, as you can obtain the vertical strain for a given vertical stress. You can repeat this for different vertical stresses, but you should get the best approximation for the lowest vertical stress. Hope this helps!
hi miss lopes answer is correct
but as you know the vertical stress in direct shear test is constant and you must repeat the test to obtain E
so i advise to plot the stress-shear strain and find the shear modulus then by this formula find the elasticity modulus
G=E/2(1+v)
tnx
In the direct shear test, the shear stresses and displacements are non-uniformly distributed within the soil specimen. As such, an appropriate height cannot be defined for the calculation of shear strains, in other words, the stress-strain relationships cannot be determined from this test, as a result, any quantity associated to stress-strain curves such as modulus of elasticity cannot be determined.
Dear Arsalan,
Arsalan Ahmad
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