The walls were built inside transparent plastic boxes, bought from office supply stores (Figure 1), which measured approximately 22.5 in (length) × 12.75 in. (height) × 15.5 in. (width). The face of the wall was approximately 6 in. from one end of the box. While building the wall with poster board facing, we used two wooden pieces (approx. 1 in. × 1 in.) to keep the board in place while the wall was constructed. The wooden pieces were stuck to the inside wall of the container using scotch tape (Figure 2). The pieces were removed after the wall was completed and before loading (Figure 3). We avoided the sidewall leakage by using paper towel flaps along the sides and the bottom of the poster board facing (Figure 2). These flaps were attached to the poster-board facing, but not connected to the container walls.
The walls of the containers were sufficiently rigid to hold the soil and the imposed load without significant buckling (Figure 3). The transparent wall allowed viewing from the side (Figure 4). The use of these containers helped avoid spilling sand on the floor when the walls failed.
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Figure 1. Container and tools, including paper towel roll, used in wrap-around wall |
Figure 2. Poster-board wall in progress. [Note the wooden pieces outside the facing and the paper towel flaps on both sides of the wall, along the container] |
Figure 3. Completed wall being tested. [Note the wooden pieces are removed before loading] |
We used play sand, purchased from Home Depot. Initially, the sand was quite moist as it came out of the bags and had to be thoroughly dried (air drying over several days in flat trays was sufficient). However, even play sand had sufficient fines that caused dust and we had to issue dust masks for the students.
The soils were stored in 15 gallon plastic containers (Figure 5), from which they were transferred into the model container.
The wrap-around walls (Figures 4 and 5) proved to be extremely strong, even when quite nominal quantities of paper was used. Several colleagues from other schools, with prior experience on this project had warned about this. We used “regular” paper towels (single-ply) that come in rolls. We are going to try experiments with other, weaker papers to identify a more acceptable (=less strong) material.
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Figure 4. Wrap-around wall, after construction |
Figure 5. Wrap-around wall, after construction |
For additional information on this work, please contact Anirban De.
