Two specimens were prepared from sand collected from the same area. Set the cell pressure to $100$kPa and the back pressure to $100$kPa.

After saturation was achieved by applying $90$ kPa, isostatic consolidation was performed by fixing the back pressure and increasing the cell pressure to $300$ kPa. this

For the specimens prepared in this way, one was subjected to a CD test $($consolidation drainage test$)$ and the other was a CU test $($consolidation undrainage test$).$

carried out. If shear failure occurred in the sample subjected to the CD test when the sequential stress was given at $500$ kPa, the CU test was performed.

What is the sequential stress required to destroy the sample subjected to $?$ However, the excess pore pressure coefficient of this sand sample is

Assuming A$=0\mathrm{.}8,$ B$=1\mathrm{.}0,$ the CU test process is expressed as a stress path.