Problem $1$

A site has been selected for a light commercial development $($i$.$e$.$ strip mall$).$ A subsurface investigation of the property

shows the presence of a high plasticity clay $(LL=85\frac{,}{P}$I $=57)$ extending to depths ranging from $10$ to $15$ feet. Rather

than select another site, the owner needs a plan to remediate the high plasticity clay and maximize bearing capacities for

shallow foundations.

The strip mall $($i$.$e$.$ building$)$ will have a length of $250$ feet and a depth $($width$)$ of $60$ feet. The foundation of the building

will consist of square and strip $($continuous$)$ footings. Local codes require that shallow foundations bear a minimum of $2$

feet below finish grade. The local codes also require that shallow foundations come to bear on a minimum of $3$ feet of

low plasticity material. Given the highly plastic nature of the in situ soil, any low plasticity material $($placed or treated$)$

should extend a minimum of $10$ feet from the building perimeter.

The developer owns a lot nearby $($within $5$ miles$)$ which has low plasticity silty clay on it which can be used as

engineered fill. The developer also owns a grading company that can over excavate the high plasticity clay and replace it

with the silty clay from his nearby property. The cost to over excavate and replace the high plasticity clay is $$12\mathrm{.}00$ per

cubic yard and will require approximately $5$ working days to accomplish.

The properties of the borrow material to be used as fill are as follows:

Low Plasticity clay in situ void ratio, $e_0=0\mathrm{.}55$

Low plasticity clay specific gravity, $G_s=2\mathrm{.}65$

Low plasticity clay compacted void ratio, $e=0\mathrm{.}39$

Low plasticity clay compacted unconfined compressive strength, $q_u=2200psf$

Low plasticity clay compacted angle of internal friction, ${}^{\text{'}}=10$

An earthwork contractor in a nearby town has equipment that can be used to chemically treat the high plasticity clay.

This contractor can remove the high plasticity clay and potentially stabilize it with $6\%$ by weight of lime$.$ The cost to

chemically treat the high plasticity clay is $$12\mathrm{.}50$ per cubic yard and will require $10$ working days to complete.

The properties of the chemically treated material are as follows:

Lime treated clay compacted void ratio. $e=0\mathrm{.}65$

Lime treated clay specific gravity, $Gs=2\mathrm{.}63$

Lime treated clay compacted unconfined compressive strength, $qu=1800psf$

Lime treated clay compacted angle of internal friction, ${}^{\text{'}}=7$

As the geotechnical engineer, you are assigned the following tasks:

Choose the most economical method to remediate the high plasticity clay that will provide the maximum shallow

foundation bearing capacities.

Estimate the minimum quantity of high plasticity clay that is to be remediated $($removed and replaced or chemically

treated$)$

Specify the plan dimensions of the area to be remediated

Specify the depth of high plasticity clay to be remediated

Determine the allowable bearing capacity of the shallow foundations anticipated for the building.