$13\mathrm{.}4$ During a subsoil exploration program, undisturbed normally consolidated silty clay

samples were collected in Shelby tubes from location $A$ as shown in Figure $13\mathrm{.}62.$

Figure $13\mathrm{.}62$

Details

Following are the results of four drained, direct shear tests conducted on the clay samples

with each having a diameter of $63\mathrm{.}5mm$ and height of $32mm.$

a$.$ Determine the drained angle of friction for the silty clay soil.

b$.$ Determine the shear strength of the clay in the field at location $A.$

Problem $13\mathrm{.}4$ Part $($a$)$

The area of the specimen $A=$

$($Express your answer with five decimal places, e$.$g$.,0\mathrm{.}12345$;

unit: $m^2)$

Test $1$:

The normal stress at failure, sigma$\_1=$

$k\frac{N}{m^2}$

The shear stress at failure, tau$\_$f$1=$

$k\frac{N}{m^2}$

$($Express your answer with one decimal place$)$

Problem $13\mathrm{.}4$ Part $($a$)$

Test $2$:

The normal stress at failure, sigma$\_2=$

$k\frac{N}{m^2}$

The shear stress at failure, tau$\_$f$2=$

$k\frac{N}{m^2}$

$($Express your answer with one decimal place$)$

Problem $13\mathrm{.}4$ Part $($a$)$

Test $3$:

The normal stress at failure, sigma$\_3=$

$k\frac{N}{m^2}$

The shear stress at failure, tau$\_$f$3=$

$k\frac{N}{m^2}$

$($Express your answer with one decimal place$)$

Question $9$

Problem $13\mathrm{.}4$ Part $($a$)$

Test $4$:

The normal stress at failure, sigma$\_4=$

$k\frac{N}{m^2}$

The shear stress at failure, tau$\_$f$4=$

$k\frac{N}{m^2}$

$($Express your answer with one decimal place$)$