Use the CPT data presented in the reader to calculate the friction angle of the clayey silt layer that extends from z $=15$ to z $=20\mathrm{.}2$ meters. Answer: The mid layer point is at z $=17\mathrm{.}6$ meters. At that point, vo $=350$ kPa, and $\text{'}$vo $=184$ kPa. The by$-$eye average qt for that layer is $1000$ kPa. The net cone tip resistance is qnet $=$ qt vo $=1000350=650$ kPa, which means that Qtn $=4\mathrm{.}79$ and $\text{'}=25$ deg. Qt $=\frac{qt-vo}{{}^{\text{'}}}vo$ Normalized cone resistance, Qtn The cone resistance expressed in a non$-$dimensional form taking account of the in$-$situ vertical stresses and where the stress exponent $($n$)$ varies with soil type and stress level. sep $14,2015$