Geotech – Assignment

Assignment # 1:                                                                                                                  Marks : 100
Q.1 The critical state line or steady state line for Sydney sand in e*-log(p¢) is given by the following equation:
(1)
Using the concept of critical state concept, identify whether the following site would be liquefied due to cyclic instability. Plot the graph for y* vs depth with a y*=0 line.                                          [Marks: 25]
Fig. 1: Soil profile for question 1
 

1. 2: Based on “CPT modified data” estimate liquefaction potential and plot the three graphs as given in “Example liquefaction resistance SPT”. [Marks: 50]

Note, use Q and F for soil classification and show iterations for exponent “n” in I_c calculation.
Assume, g=20kN/m³, water table 1.0m below the surface, a_max=0.10g and Mw=7.0
Any other parameter may be assumed as SPT example.
 
Q.3: Use Been et al. (1987) approach to calculate y from CPT data and estimate liquefaction potential under critical state soil mechanics.                                                                                      [Marks: 25]
Produce a plot as in Q.1.
What are current assumptions for this approach and how can be overcome?