Building a Tarpul

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Students will learn how soil affects a building structure.

Big Idea

Students construct a mini tarpul and experiment with different soils until they can create a sturdy functional tarpul.

Using the Engineering Process

10 minutes

Understanding how the compaction of soil plays a role in holding up a structure is really defined in this little activity.  To be prepared for this lesson, you need to teach Learning About Geotechnical Engineering Through Literature so that students have an understanding of a TarPul. 

Materials You Need for each team of three:

  • Small paper cup
  • String
  • Two peanut butter size jars or wide mouth pint canning jars 
  • pencils
  • Paper clips 
  • Pennies or washers
  • A small bag of potting soil and sand: 1.5 cups per container
  • Fish Gravel
  • Sharpie Marker
  • Paper
  • Ruler

Directions for preparation: Fill half of the containers with gravelly soil. The other half should be filled with sand. ( The students will test which soil is better for holding up the TarPul.) Don't compact the soil, but mark the line where the soil or sand is on the jar. Then mark it 1/4 " below the soil line, and again at 1/2 " below. There will be three tests run and students will compact the soil down to these lines and make observations.

I open the lesson today by referring back to our lesson when we studied Suman Crosses the Karnali River, by asking: Can you define the problem that Suman's village faced involving the river?"

I allow students to share their thoughts as they told me that the river would flood and they could not get across it very easily, if at all in the rainy season. 

I ask: What had to be considered before building the TarPul? 

Students reply that the TarPul was on poles and they need to figure out a place where it could be built safely. 

I ask: What kind of soil do we find near rivers? 

Students respond by telling me that sand, rocky sand and mud are near rivers. We talk about our own Nippersink Creek and the types of soil we notice when we go to the park to play in it. We talk about that there were safe places to wade and then if you went too far, the bottom got really mucky. Then someone says something about avoiding it because you could get really stuck there.

I ask students how the engineer figured out how to build the TarPul safely?

They talk about him taking core samples and looking at a map. We review how river bends were bad places to put bridges and TarPuls because it will flood out at that spot.

I tell them that I want to help them understand a TarPul a little better by creating a model. 

They are excited to move on! 

We Begin!

30 minutes

I write the questions:

What important things must we consider before we build a structure like a TarPul along a river bank? 

How do models help us understand how real structures work?

What can be tested by building a model of a TarPul?

What variables did we control?

I read each question and explain to the students that we need to consider these questions as we work. When we are all done, we will revisit them and use our data to answer the questions. I also encourage them to write any questions they are having in their minds in their notebook. 

Demonstrate: I show students how to compact the soil so they understand what that is about. I show them how they need to rebuild the TarPul each time by repeating the compacting process and inserting the pencils again. I explain what materials they need to gather, holding up each one.  I have laid them out on the lab counters, easily accessible. I remind them of their lab manners, safety and team respect. 

Developing a Chart: To address my student's need to develop and organize data, I create this TarPul Test Sheet. We look at the data sheet together. I ask them to read the directions out loud once in their group and stop to ask any questions. I tell them that they need to look at my drawing of the TarPul for reference. 

As soon as they are ready, I encourage them to begin.They quickly set to work, setting up their TapPuls. 

When they are completed and the chart is all done, I gather them around me to discuss their observations and describe their charts. 

Wrapping it Up!

15 minutes

I wrap up the lesson by gathering them around after they are all done. I ask: "What did you notice about the amount of weights?" Students share their data. I also asked if there was change as they inserted the pole after compaction? Students share that the pole was harder to insert.

Then I return to the questions on the board from the beginning of the lesson and ask if they had considered any of them as they worked. I also ask if there are any questions they noted in their notebooks that they wanted to share? 

I ask them if they thought if they were really building a TarPul, would they need to compact the soil? Would it be more than 1/4" or a 1/2" ? I ask them to explain that.

Then, I ask them to finish up their sheets by answering all of the questions on the back. I want them to brainstorm ways of improving their TarPul to increase the amounts of weight it could carry. What would they do?

Students return to their desks to work until it was time to stop. I assign their worksheet for homework.