As second graders wrap-up their geotechnical engineering unit, they are putting everything they've learned into action!  As geotecnical engineers, they must recommend a location where the TarPul should be built.  They want the TarPul to hold a lot of weight and be built in safe, strong soil that is unlikely to erode.  

However, sometimes the closest locations to where there is a need are too dangerous, and the community must be educated about how the soil conditions could be changed...at a cost.  Just because soil compaction strengthens the soil doesn't mean it's free.  Second graders are weighing all the options and testing their ideas.   They are then using all the data to communicate their final decision!

With Suman's Field Map in hand, second graders spent time "dissecting" the map so that they can better understand where the TarPul could be built.  We used the key to help us evaluate every possible site, focusing on these three questions:

1.  What type of soil does the site have on each side of the river?
2.  How does the shape of the river at each site affect the soil's ability to erode?
3.  How far is the site from the village to the school and clinic?

We'll be focusing on these questions as we test each possible location and ultimately make a recommendation as to where we should build the TarPul.  Go geotechnical engineers! 

With the model TarPuls in hand, second graders began collecting data on soil compaction.  Beginning with soil that was not compacted, students tested the number of washers a TarPul could hold until it fell into the "river."  They then compacted the soil once, and recorded the number of washers it could now hold.  We began looking for patterns in the data, noticing if the number of washers increased, decreased, or stayed the same as the soil was compacted more.  Awesome job second grade! 

Second graders know that some soil types are better than others.  They also know that there are stronger, more stable solutions to keep a structure in the earth.  But what happens when the soil we have at a site isn't the strongest?  How can we change it to make it stronger?

Using clay as a model for soil particles, second graders saw how compacting the soil changes the soil's shape and structure.  Compacting the soil means to push down on it.  

Check out the results of our soil compaction demonstration below!

After their initial houses failed an earthquake test, second graders planned out, tested, and improved their earthquake-resistant house designs.   Using what they know about soil and forces, they had limited materials to make sure their houses stayed standing during an earthquake.  Using the engineering design process, students were allowed to improve their designs to guarantee the safety of those inside the house.  Check out how creative they were with limited supplies!

While geotechnical engineers do not build houses, second graders are building paper houses.  These paper houses are going to be used as part of an earthquake test.  Geotechnical engineers may help those who build houses decide where to build a house.

We're using observational skills to see what happens to the houses before, during and after an earthquake.  After we see what happens to the houses, we'll make recommendations to improve the houses' structures and see if they can withstand an earthquake!

Below you'll see student work showcasing how their house reacted before, during, and after a model earthquake.  They'll be focusing on how to make improvements to the house so that it doesn't fall over during another earthquake...if one should happen.  Second graders made connections to the technical drawing skills they've been learning in art.  Notice the use of arrows and ghost drawings to show movement!

Before we decide to build anything anywhere, it is important to know what is below the surface of the Earth.  Even if a site "looks good" it is important to compare it to another site to see if we indeed have the best choice.  See how second graders compared two different sites by taking core samples at each location.  Can you see the differences between the two sites?  Which site would you choose to build on?  Why?

So before we build the TarPul somewhere, shouldn't we know what's below the topsoil?  If it's just soil that has a good chance of eroding when a flood comes, should we build it there?  Or should we look for another spot?  

Using a simple technology called a core sample, second graders discovered that this simple device can tell you so much.  The clear tube is inserted into soil.  Pushing down hard, the layers of soil collect in the tube.  When the tube is removed from the soil, the tube's transparency reveals the layers in the soil.  The photo to the right shows what eight different spots look like at one site.  Can you tell which layers are topsoil, sand, clay and bedrock?

As we discover more about soil and its layers, we'll be able to make more informed decisions regarding where to build the TarPul, just like a real geotechnical engineer would do!  How awesome!

We've officially started our engineering story, Suman Crosses the Karnali River.  The problem became apparent to us immediately, when Suman's grandmother, Ajee, became sick and had to cross the river during monsoon season.

Becoming experts at soil in science, second graders had a chance today to refresh their memory on three types of soil:  clay, sand, and topsoil.  Some of these earth materials erode quickly and others do not.  Some are stronger to build a bridge into over others.  

Second graders also learned a technology that is very important to the people in Nepal--the TarPul.  TarPul literally translates to "Wire Bridge," and people pull themselves across the river holding onto the wires that the small cable car is suspended from. Because they are high off the ground, the people will not come in contact with the rising water during a flood.  What an awesome technology!  

Why do geotechnical engineers have to know about soil?  Why do they need to know about erosion?  These are some important questions that second graders are investigating.

Using a small tray of soil, second graders saw Mrs. Brinza create a flood in a small LEGO village (house, bridge, and school).  The effects were devastating!  Much of the soil washed away because the water's force was strong enough to do so.  As the soil eroded, it was deposited farther downstream.  This meant that the bridge and house were about to collapse and that the school had large amounts of soil in front of it that were once not there.

Erosion from both wind and soil are REAL problems geotechnical engineers face as they decide where they can recommend structures to be built.