Using the data in the table:

a$.$ Plot the vertical effective consolidation stress versus void ratio on both arithmetic and semi$-$log graphs. For the arithmetic graph, constrain the vertical axes to $0\mathrm{.}55$ and $0\mathrm{.}95$ ; and the horizontal to $0$ to $1,500$kPa; for the semi$-$log graph, use the same vertical axis constraints, but use $10$ kPa and $10,000$kPa to ease interpretation. Plot the data points only, and draw in a smooth curve by hand. Plot each graph on a full sheet of paper with void ratio oriented on the long axis.

b$.$ Determine the Coefficient of Compressibility, $a_v,$ and Compression Index, $C_c,$ over the stress ranges of $(320$ to $640$ kPa $)$ and $(640$ to $1280$ kPa $).$ Compare these two sets of values. Which approach $,$ or $C_c)$ would you feel more comfortable using in a design setting and why?

c$.$ Determine the Recompression Index starting at $1280$ kPa $($i$.$e$.,$ use the first and last data points of the unload cycle, not the load cycle. The unload cycle is not affected by sample disturbance, whereas the load cycle almost always is$...).$

d$.$ Determine the preconsolidation stress using the Casagrande method.

$\backslash$table$[[$Pressure $($kPa$),$Void Ratio,Pressure $($kPa$),$Void Ratio$],[20,0\mathrm{.}864,1280,0\mathrm{.}602],[40,0\mathrm{.}853,320,0\mathrm{.}628]]$

ECE $3424$ Soil Mechanics

$\backslash$table$[[80,0\mathrm{.}843,80,0\mathrm{.}663],[160,0\mathrm{.}830,20,0\mathrm{.}704],[320,0\mathrm{.}785,0,0\mathrm{.}801],[640,0\mathrm{.}696,,]]$