## Understanding How Earthquakes Affect the Built Environment: Day 3

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#### Abstract

This engineering educational module on the behavior of piles in soft clays during earthquake loading seeks to introduce engineering as a viable career to 5th-8th graders and teach students how geotechnical engineers design foundations in marginal soils to minimize damage to infrastructure during earthquakes. A five-hour module is presented to simulate real-world behavior of piles in soft clays during earthquake loading, and visually show the improvement in how these same piles behave after being stabilized with a deep soil mixing technique. In this module, soft soil is simulated by using Jell-O®, piles are simulated using Slim Jims® and soil stabilization is simulated using peanut butter, marshmallows or cheese. Each student group has to design a stabilization procedure to strengthen the piles. The students compete to see who can design a pile with the least amount of deflection for the least amount of money. This five-hour module is divided into hour long segments for ease of application.

#### Introduction

Pile foundations are an integral part of many civil engineering structures, such as highway bridges, port facilities and tall buildings. Foundations can have a huge impact on an above ground structures ability to withstand earthquakes. If a foundation is built strong enough, the damage to the above ground structure will be minimal. Therefore, it is important to understand how to build foundations in areas of the world where the soil is not very strong. In some cases, it becomes necessary to improve the soil using material like cement. The interaction between the foundation and the soil is called soil-structure interaction and it is very important in geotechnical engineering, but is difficult to see because it happens underground. In order for students to fully grasp how a pile foundation in soft soil would be affected by an earthquake and how it would behave after the surrounding soil was improved, it is imperative to use simulated soil allowing students to see into the subsurface to observe pile behavior underneath the ground during an earthquake. Jell-o is used as soft clay soil because it is translucent, as well as soft enough to show adequate deflections in an unimproved pile. Slim Jims (beef jerky) are the pile material, creamy and crunchy peanut butter, small and large marshmallows, as well as sharp cheddar cheese are the stabilizing material to improve the pile performance, and Lollipops are inserted into the top of the Slim Jim piles to simulate a structure. The students compete to see who can design a pile with the least amount of deflection for the least amount of money using a predetermined cost list and an optimization equation. This module can be administered to a class size as small as 5 to as large as 35 (or more) with enough help. The larger the class, the more Jell-o has to be made. The average 2011 cost per group, including all supplies and after a shaker has been built, is roughly $10, although this cost can be offset by having each student bring in a plastic tub, a box of Jell-o and some excavating spoons.

#### Earthquake Engineering Component

The goal of this activity is to teach students about geotechnical engineering and strengthening foundations to lessen movements and therefore, damages, due to earthquakes. The model is a direct comparison to real-life examples of improving the behavior of bridges built in soft soil by using cement deep soil mixing to strengthen the existing pile foundations. In this case, the cement deep soil mixing is simulated using a variety of edible materials with different cohesive and strength properties, such as cheese, peanut butter and marshmallows. This model is relevant to the field of earthquake engineering because every year, thousands of people lose their lives due to structure collapses during and after earthquakes. Many of these collapses could be prevented by building better foundation systems.

#### Learning Objectives and Standards

Links to the National Science Standards and to individual State Science Standards are available by using this link:

http://nees.org/education/for-teachers/k12-teachers#standards

The specific learning outcomes of this module are to: 1. Learn the importance of geotechnical engineering and foundation systems in keeping structures safe during earthquakes. 2. Improve a zone of soft soil around piles to reduce movement, therefore, minimizing earthquake induced damage. 3. Gain insight into geotechnical engineering to broaden career path opportunities. 4. Improve the perceptions of engineers and the engineering profession.

The standards pertaining to Day 3 of this module are as follows:

**OAC 210:15-3-78: Standards for Inquiry, Physical, Life, and Earth/Space Science**

Process Standard 1.1. Identify qualitative and/or quantitative changes given conditions (e.g., temperature, mass, volume, time, position, length) before, during, and after an event.

Process Standard 1.2. Use appropriate tools (e.g., metric ruler, graduated cylinder, thermometer, balances, spring scales, stopwatches, computers, hand held data collection devices) to measure objects, organisms, and/or events.

Process Standard 1.3. Use appropriate International System of Units (SI) (i.e., grams, meters, liters, degrees Celsius, and seconds); and SI prefixes (i.e. milli-, centi-, and kilo-) when measuring objects, organisms and/or events.

Process Standard 3.1. Ask questions about the world and design investigations that lead to scientific inquiry. Identify testable questions based on prior knowledge, background research, or observations.

Process Standard 3.2. Evaluate the design of a scientific investigation.

Process Standard 3.3. Identify variables and/or controls in an experimental setup: independent variable and dependent variable.

Process Standard 3.4. Identify a testable hypothesis for an experiment.

Process Standard 3.5. Follow a multistep procedure when carrying out experiments, taking measurements, or performing technical tasks.

Process Standard 3.6. Recognize potential hazards and practice safety procedures in all science activities.

Process Standard 4.2. Interpret data tables, line, bar, trend, and/or circle graphs.

Process Standard 4.3. Evaluate data to develop reasonable explanation, and/or predictions.

Process Standard 4.4. Determine if results of investigations support or do not support hypotheses.

Process Standard 5.1. Ask questions that can be answered through scientific investigation.

Process Standard 5.2. Design and conduct experiments utilizing scientific processes.

Process Standard 5.3. Use the engineering design process to address a problem or need (e.g., identify a need, conduct background research, prepare preliminary designs, build and test a prototype, test and revise design, communicate results).

Process Standard 5.4. Understand the value of, and use technology to gather data and analyze results of investigations (e.g., probes, hand-held digital devices, digital cameras, software, computers, calculators, digital balances, GPS).

Process Standard 5.5. Develop a logical relationship between evidence and explanation to form and communicate a valid conclusion, and suggest alternative explanation.

**PHYSICAL SCIENCE**

Standard 2.1. The motion of an object can be measured. The position of an object, its speed and direction can be represented on a graph.

**OAC 210:15-3-46.1: MATHEMATICS: Grades 6 - 8**

Process Standard 1.1. Develop and test strategies to solve practical, everyday problems which may have single or multiple answers.

Process Standard 1.2. Use technology to generate and analyze data to solve problems.

Process Standard 1.3. Formulate problems from situations within and outside of mathematics and generalize solutions and strategies to new problem situations.

Process Standard 1.4. Evaluate results to determine their reasonableness.

Process Standard 1.5. Apply a variety of strategies (e.g., restate the problem, look for a pattern, diagrams, solve a simpler problem, work backwards, trial and error) to solve problems, with emphasis on multistep and non-routine problems.

Process Standard 2.1. Discuss, interpret, translate (from one to another) and evaluate mathematical ideas (e.g., oral, written, pictorial, concrete, graphical, algebraic).

Process Standard 2.2. Reflect on and justify reasoning in mathematical problem solving (e.g., convince, demonstrate, formulate).

Process Standard 2.3. Select and use appropriate terminology when discussing mathematical concepts and ideas.

Process Standard 3.1. Identify and extend patterns and use experiences and observations to make suppositions.

Process Standard 3.2. Use counter examples to disprove suppositions (e.g., all squares are rectangles, but are all rectangles squares?).

Process Standard 3.3. Develop and evaluate mathematical arguments (e.g., agree or disagree with the reasoning of other classmates and explain why).

Process Standard 4.1. Apply mathematical strategies to solve problems that arise from other disciplines and the real world.

#### Material List

The quantities of these items will depend on the number of students participating in the module, the size of the Jell-o container chosen as well as the format of the day For one group of 5 students, using the same size box as detailed here, with a module performed over 5 class periods on different days, the quantities of the material are:

Jell-O® tub: (1) Plastic, Dimensions: 15 X 11-1/2 X 6

Figure 1: 15" X 11-1/2" X 6" Plastic Jell-o tub with 6 Piles; Jell-O® Depth = 3"

Jell-O®: (117 ounces: Each tub contains 13-3 oz boxes = 39 ounces per tub + 12 cups or 3 liters of boiling water + 14 cups or 3.5 liters of cold water) Jell-O®: 1 tub (39 ounces)

Slim-Jims®: diameter=1 cm (0.39 inches), length=9.5 cm (3.74 inches) Jell-O®: 4

Soil (Jell-O® Stabilization) Cheese (1 block): Multiple molds can be cut out of 1 block to suffice for all three aspects of the experiment (Demonstration, Jell-O® play and Final Design) Creamy and Crunchy Peanut Butter: (8 oz of each about 1/2 of a regularly sized peanut butter container) Small and Large Marshmallows: (6 of each, depending on final designs) Lollipops Jell-O®: 4

Figure 2: Picture of the Cheese, Large Marshmallow, Slim Jim and Lollipop Used in the Module.

Excavation molds: 1 of each size

Table 1: Aluminum and Plastic Excavation Mold Dimensions.

Mold A B C D E F G D (cm) 0.84 3.00 3.00 3.63 4.88 6.15 7.75 L (cm) 8.92 3.02 6.12 4.60 6.02 10.21 10.16 V(cm3) 4.8 21.3 43 47.4 112.7 304.2 479.2

Figure 3: Excavation Molds: From left to right, G, F, E, D, C, B, A.

Earthquake Kit: 1 per group Spatulas (peanut butter placement), excavation tools (measuring spoons), excavation molds, pens, ruler, note cards, rubber gloves, wooden dowels (peanut butter placement and compaction), Slim Jims, Lollipops and a plastic container for the excavated Jell-O® (Figure 4).

Figure 4: Earthquake Module Kit for Each Group.

Shaker A simple shaker was designed and built for roughly $26 (October 2010). The shaker was made out of plywood, toilet partition, drawer pulls, a steel rod, a inch steel washer and some nuts and bolts. There was some welding involved to make the bearing of the shaker, however, this part could be manufactured with simple nuts and bolts, alleviating the need for a machine shop and welder. A variable speed cordless drill can be attached to this bearing and used to shake the system at many different frequencies depending on the speed chosen, or a hand crank could be attached to manually shake the system. The closer the hole is to the center, the smaller the amplitude, and the farther away the hole is to the center, the larger the amplitude. This is a very economical and efficient shaker to simulate earthquakes in the school setting (Figure 6).

Figure 6: Low Cost Earthquake Simulator (designed and built by Mr. Michael W. Leary, owner AM Squared Construction Services, LLC).

#### Procedure

Practicing in Groups. Explain design under constraints - simulating improvements to the soil using different improvement materials, different dimensions of improvement, different ways to place it (existing bridge or before piles), economic constraints. Students must use cost list to determine their design, and points will be awarded for economy and minimizing deflection by an optimization equation. Provide a cost list to the students. This cost list can be modified to encompass more stabilizer material or a greater difference between existing stabilizer material (Table 2). Table 2: Cost List for Stabilizer Material

Cheese: $600/50 grams Crunchy Peanut Butter: $300/50 grams Creamy Peanut Butter: $200/50 grams Small Marshmallow: $150 Large Marshmallow: $450

*As a reference, Molds C and D could hold about 50 grams of peanut butter, while Mold E was the perfect size for a large marshmallow. Mold F held about 170 grams of cheese after the hole for the pile was drilled.

Provide an optimization equation to the students. The following equation was used to determine the winner of the module with displacements in inches and cost in dollars. The group with the largest score wins.

x=(1/Displacement)^3+1000/Cost Eq. 1

*The equation to determine the winner can be altered to encompass the objectives of the module. If it is determined that cost should play a bigger factor in the final score, then the second term could be optimized to produce a larger number. In addition, the students can be asked to plot this equation and understand the effects of displacement and cost. This exercise will naturally bring some of the mathematics concepts into this module. The student groups will practice excavation, pile driving, and different ground improvement techniques and choose their final design.

#### Links and Resources

A full report on this module is given here: Cerato, A.B., Taghavi, A., Muraleetharan, K.K. and Miller, G.A. (2011). Understanding and Improving the Seismic Behavior of Pile Foundations in Soft Clays: An Educational Module. Report submitted to NEES-Comm, 80 pp. (https://nees.org/resources/2705)

#### Assessment

Jell-o Activity Day 3:

1. What stabilization material worked the best for you? Was it what you thought it would be or was it something completely different?

2. What happened to the pile when you used more stabilizing material? Did the deflections lessen? If so, about how much (e.g., if you doubled the amount of stabilizer, did the deflections decrease by 1/2)?

3. What about cost versus deflection? Did increasing the amount of stabilizer to lessen the deflections justify the cost increase? What parameter is most important in this exercise? Use the equation and cost list provided to justify your answer.

4. What parameter, deflection or cost, is most important in engineering in the real world? Why? Give examples to support your answer.

#### Extensions

This module is based on real life examples. Every structure built on this earth has some sort of foundation system, anchoring that structure to the ground. Buildings without adequate foundations in seismically active areas do not fare well. However all the public sees is the damage to the above ground structure, and thinks that if the above ground structure is made stronger it will fare better during earthquakes. While partially true, if the foundation system is not strong, no matter how strong the structure is built, it will always fail. The foundation system strength and flexibility is one of the major keys to building earthquake resistant structures, and introducing the concept of geotechnical engineering into middle schools can help to educate our future workforce.

#### Scaling

This module could also be used at various educational levels, from elementary to high school, as well as at the undergraduate level, with appropriate modifications. For example, in elementary school, the Jell-O® play (Day 3) and Jell-O® design (Day 4) could be the highlights of the module, whereas, in high school, the science behind soil stabilization could be stressed more, while still allowing the students to play with the Jell-O® and stabilization procedures.

#### Cite this work

Researchers should cite this work as follows: