ECMM109 1
ECMM109
UNIVERSITY OF EXETER
COLLEGE OF ENGINEERING, MATHEMATICS
AND PHYSICAL SCIENCES
ENGINEERING
Advanced Geotechnical Engineering
Module Convenor: Prof. A. A. Javadi
Duration: TWO HOURS + 30 minutes upload time
May 2021
Answer ALL questions.
This is an OPEN BOOK/NOTE examination.
ECMM109 2
Questions 1-4 are multiple choice questions (select one answer only and
show your working)
Question 1 (4 marks)
Figure Q1 shows the Mohr circle at failure for an undrained triaxial test. What
is the excess pore pressure at failure
Figure Q1
(a) 71.4 kPa
(b) 81.4 kPa
(c) 91.4 kPa
(d) 101.4 kPa
Question 2 (4 marks)
From the data in Figure Q1, what are the values of effective normal stress and shear
stress on the failure plane
(a) n
′ = 20.3 kPa, = 19.5 kPa
(b) n
′ = 25.3 kPa, = 19.5 kPa
(c) n
′ = 29.3 kPa, = 20.5 kPa
(d) n
′ = 34.3 kPa, = 20.5 kPa
σ, σ (kPa)
160
‘=35°
110
cu=25τ (kPa)
ECMM109 3
Question 3 (5 marks)
For a soil element with normal and shear stresses as shown in Figure Q3, the
major and minor principal stresses will be:
(a) 418 kN/m2 and 184 kN/m2
(b) 617 kN/m2 and 223 kN/m2
(c) 818 kN/m2 and 184 kN/m2
(d) 918 kN/m2 and 223 kN/m2
Question 4 (5 marks)
In Figure Q3, the inclined plane EF makes an angle of 30
o
to the horizontal.
The normal and shear stresses on the plane EF are:
(a) n = 401 kN/m2 and = 98 kN/m2
(b) n = 401 kN/m2 and = 196 kN/m2
(c) n = 441 kN/m2 and = 98 kN/m2
(d) n = 441 kN/m2 and = 196 kN/m2
Figure Q3
E
y=600 kN/m2
x=240 kN/m2
xy=80 kN/m2
F
ECMM109 4
Question 5 (12 marks)
Figure Q5 shows 4 stress paths: CD and CF starting from point C, and AB and AE
starting from point A. The starting points A and C are both on the current yield locus
yl 1. Discuss in detail and compare the 4 stress paths in q,p’ and v,p’ spaces (Figures
(a) and (b)). Also comment in detail on the separation of strains into elastic and plastic
components in the 4 stress paths CD, CF, AB and AE.
Figure Q5
ncl
yl 2
(a)
(b)
yl 2
yl 1
yl 1
ECMM109 5
Question 6 (35 marks)
A clay soil has the following fundamental constants:
0.87
0.10
0.18
‘ 1 2.5 at
‘ 1 2.8 at =
=
=
= =
= = M
p kPa
p kPa N
