An undrained triaxial compression strength test was conducted on clayey silt soils and the following test results are obatined.
$\sigma_{3}kN/m^{2}$ 17 44 56
$\sigma_{1}kN/m^{2}$ 157 204 225
$U kN/m^{2}$ 12 20 22

Draw the associated Mohr's circles and determine the values of the shear parameters considering the (a) total stress and (b) effective stresses.

1 Answer

Mohr Circle

Total Stress

  • For a solution with total stresses, draw Mohr circles C 1 ​ ,C 2 ​ and C 3 ​ for each of the specimens using the corresponding principal stresses σ 1 ​ and σ 3 ​ .
  • Draw a Mohr envelope tangent to these circles as shown in Fig.Now from the figure Hence,
  • C=48kN/m^2 ; phi = 15°.

Effective Stress Parameters

  • The effective principal stresses may be found by subtracting the pore pressures u from the total principal stresses as given below.

  • As before draw Mohr circles C'1 ,C'2 and C'3 for each of the specimens as shown in Fig.

  • C'=46kN/m^2 and Phi'=20°.

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