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rstewart8

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## Homework Statement

Two consolidated and drained (CO) triaxial compression tests (tests A and 8)

were conducted on dense dry sand at the same void ratio. Test A had a cell

pressure of 150 kPa, while in test B the cell pressure was 600 kPa (u=OkPa).

These stresses were held constant throughout the test. At failure, they had

maximum principal stress differences of 600 and 2550 kPa, respectively. You

are asked to:

a) Plot the Mohr circles for both tests at initial conditions and at failure.

b) Determine shear strength of this soil.

c) Determine the shear stress on the failure plane at failure for both tests?

d) Determine the orientation of the failure plane in each specimen (use

equations or graphical solution).

e) Determine the orientation of the major principal plane at failure.

f) Determine the orientation of the plane of maximum shear stress at failure

g) If these soil samples were tested in direct simple shear, would the soil

exhibit compression or dilation?

## The Attempt at a Solution

] by Ryan Stewart, on Flickr

**<< Fixed up image by Mentors >>**

**B. Determine the Shear Strength of the Soil**τ = (Ơ1 - Ơ3)/2 Sin(2θ)

=(2550)/2 * Sin (66.4 *2)

=935.5 KPa

**C. Determine the shear stress****Sample B**

θ = 45 + ∅/2

=45 + 42.8/2

θ=66.4

Cos∅ = Ơn/r

Ơn = Cos∅ x r

= Cos (180-2θ) x 1875

= 1273.95 KPA

τ = c + Ơn tan (2θ)

= 0 + 1273.95 x tan (2 x 66.4)

= 1375.7 KPA

This is as far as I've gotten just wanted to make sure I was on the correct path before continuing.

Thanks for any help!

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