Total Transportation System Solutions (T2S2)

PURPOSE OF THE EXPERIMENT:

The purpose of the experiment is to determine the bearing capacity of pudding and gelatin.  These materials were selected because they behave similar to certain types of highly plastic soils and are easy to make.  The structure to be supported is a multi-layer cake.  Because the properties of pudding and gelatin are similar to some plastic soils, understanding their properties helps us understand the properties of those soils.

PROCEDURE:

A large rectangular pan is filled to the top with pudding, and a second identical pan is filled to the top with gelatin.  The cake is weighed and placed on the pudding and gelatin.  Cake is then incrementally added by the ounce to each pan until the foundation material (i.e. pudding and gelatin) is displaced and spills over the edge of the pan.  The amount of cake required to displace the foundation material is then recorded as the maximum amount of weight that can be supported by the pudding and gelatin.  Using the value of the maximum weight, and the dimensions of the area of the foundation pan, the bearing capacity for each foundation material is then calculated.

RESULTS:

Load carrying capacity:  Pudding - 6.93 pounds per square foot

    Gelatin - 14.79 pounds per square foot

One cubic foot of concrete weighs 145 pounds.  In order for this cubic foot of concrete to be supported by the pudding and the gelatin without sinking, its dimensions would be:

4.57 ft x 4.57 ft x 0.58 in for the pudding

3.13 ft x 3.13 ft x 1.22 in for the gelatin

A footing that is large and thin is called a spread footing.  The concept behind a spread footing is that it spreads out the weight over a large area.  For the pudding, the spread of one cubic foot of concrete is 20.88 square feet.  (For a cubic foot of concrete on rock, the dimensions are 1 foot x 1 foot x 1 foot, with a spread of 1 square foot).  The spread of one cubic foot of concrete on gelatin is 9.80 square feet.  In other words, for highly plastic materials like pudding and gelatin, the footing has to cover an area 20.88 and 9.80 larger than a traditional footing on rock.  Theoretically, it is possible to build structures on pudding and gelatin, but given the magnitude of the area required to spread the footing, is it practical?

CONCLUSIONS:

If pudding and gelatin can support weight, then highly plastic soils, can too, if the foundations are designed property and the weight is spread out.  The concept of the spread footing is crucial in cities built in swampy areas or on top of filled in bodies of water, such as Mexico City, was sits atop a filled in lake.  Before constructing a building, it is critical to have good soil data in order to ensure the proper foundation is used and the long-term stability and viability of the structure being built.

CLEAN UP:

Because the foundations and structure materials are edible, not only is this experiment educational, it is delicious, too.  All materials tested were eaten after the completion of the experiment, thus eliminating any need for special disposal procedures.  Disposal of the materials required a bowl, a spoon, and an appetite.

OVERVIEW:

Many soils have a high plasticity index.  The problem with highly plastic soils is that their load-carrying capacity is less than their non-plastic counterparts, meaning that traditional foundation design may result in settlement of and significant damage to a structure.  To help avoid this, it is important to understand the nature of plastic soils and design foundations appropriately.  To simulate the performance of these soils, we tested a stucture made of cake on a foundation of pudding and gelatin, and determined the load-bearing capacity and the size of a spread footing needed to support one cubic yard of concrete.  Like pudding and gelatin, plastic soils can support concrete, as long as the properties of the soils are understood and the appropriate foundation design used.

CITE AS:

Schrader, M.H., and Schrader, G.M. (2018) Piece of cake! A delicious materials experiment.  Total Transportation System Solutions