Introducing Soil Property Evaluation in Geotechnical Engineering – Some Food for Thought

A first course in geotechnical engineering usually includes a laboratory component where students touch, examine, and test different soils. The astute instructor provides samples and simple demonstrations to help illustrate new and important concepts related to soil behavior. In addition, instructors encourage students to develop a sense of proportion and perspective when considering geologic materials. How large are gravel, sand, silt, and clay particles? What is the consistency of soft clay or loose sand? Developing perspective can be challenging since many students have not yet worked with earth materials nor have they considered soils as important elements of construction. In these cases, analogies and comparisons with familiar everyday 'things' prove helpful in improving student learning, developing a sense of proportion, and generating interest in a new topic. In this paper, we present some food for thought when addressing soil property evaluation in geotechnical engineering instruction. Specifically, we summarize the results of a laboratory test program designed to assess the "engineering behavior" of different foods. Specific tests we performed and foods we examined include measured consistency of common grocery store items using the liquid limit device, torvane, pocket penetrometer, and triaxial test apparatus; frictional resistance of grain-like foods using direct shear test equipment; particle size and particle size distribution of various food items; particle shape of various soft and hard candies; and others. We present our test results with interesting graphics, photographs, and illustrations that are ready for use as props by other instructors. In addition, we reflect on lessons learned while testing food in the geotechnical laboratory. The food analogies presented in this paper can serve as a lighthearted yet engaging introduction to soil mechanics and soil property evaluation in a first course on geotechnical engineering.