Building the Test Slope

The idea of the test slope is to find a "control value." The initial angle of the slope will be measured. Then, a load will be applied and the rain simulation will be run. After this, the new angle will be measured to see how much soil "erodes" with none of our proposed methods in place yet. 

So far, two slopes have been built and tested with an applied load but not yet with the rain simulator, as we are in the process of finalizing this design. (It has been an ongoing task to optimize its performance). 

Slope 1

The first slope created can be seen in the picture below. 

After taking measurements of the slope length, the height of the soil, and the bottom leg an average angle of 42.89 degrees was found. After applying a load, none of the soil moved. We observed that we may have packed the slope more tightly than would naturally occur in nature. It is also important to note that in a natural environment a slope would be free on the edges. 

Slope 2

We packed the soil in the second slope more loosely than that of the first. 

We took the same measurements and redid our calculations. This time the slope angle was calculated to also be around 40 degrees, it was 42.40. This was not done intentionally. However after applying the same weight, noting happened to the slope.

Improvements to be Made

• Finalize the rain simulation technique to also use in testing.
• Line the two remaining sides of the plastic container to cause less sliding.
• Line the container with a material with greater friction.
• Test using different soil types - ones that may be dryer or pack loosely because these are the types of soil that erode more easily.

Rate of Rain Fall Test Proposition

We need to be able to simulate a set amount of rain fall for each test for consistency of data. A good range for our purposes should be between 1 and 2 inches/hour, but closer to 1 in/h would be better. 2 inch is the cusp of severe rain. To measure this I propose that we take a small beaker/test tube and place it in our rain test box. We run the rain simulation for 10 mins and measure the depth of the rain in the beaker. Then that value is multiplied by 6 (there are 6 intervals of 10 mins in 1 hour) which should give us the rainfall/hour. We should then run the test again to make sure that the data can be replicated.  

Goal of Week 4 Lab

For today's lab, we decided to focus on the planning aspects of the project and make sure that everything can work together and we have all the pieces. It'll also allow us more time to test the project and each aspect rather than wait for one to finish testing to start the next piece.

New Sketches!

The above picture contains the original drawings of what we thought the rain maker system would look like as well as a brainstormed design for the toe wall. The toe wall design pictured above is a grid type design that gets its strength from its multiple square shapes and the screws that run  

through the diagonal of each rectangle. Each node on the corners of the square doubles as a joint. As a result, the shape can be adjusted to fit curvature and lengths of hills. This also means that the wall can be added onto if necessary. Once this design this design is put into the ground, it cannot be adjusted.

The above sketch contains images of the rainmaker system as it was in the last lab. It is comprised of a 2 layer plastic screen made taught through a wood and metal square. 2 sides of the square are made from metal and the other 2 sides are made from wood.The metal sides are parallel to each other and double as sliders so that the square can lengthen in to a rectangle. This also allows us to put additional fabrics in between the two screens to create a more realistic rain effect.  The fabrics we considered for this purpose are paper towel, weed block,  and cheese cloth. we also considered leaving the screens bare but this requires lifting it above the bin at a certain height.

Lastly on this page, there is a model of  our control test with limitations of this particular design.

This last page contains a few more designs that were thought of during the lab period. The first two are made of brick with the second requiring the cutting of said bricks to increase surface area and therefore increasing friction between the bricks. The third design consists of using a biodegradable material that will be layered together and weaved through several posts and placed into a thin trench around the hill.

Rain Simulation Testing

The design for the "Rain Simulation" altered again during our trip for materials at Home Depot. While there we found a screen that could be double layered and felt that it would work sufficiently as water "filter" to simulate rain instead of just pouring water. Here were a few of the methods we tested:

The Very Initial Design (Cheese Cloth as a Barrier)

Cheese cloth between the layers of screen.
Note: The entire screen was not covered in this test, but was later on.

As seen in the video, the cheese cloth did not give an even distribution of water as it fell. In other tests with cheese cloth it was too absorbent and did allow enough water to fall through at once.

Using Only the Screen

Screen purchased from Home Depot to use in rain simulation.

In our opinion this method worked better than the cheese cloth. While the water was still not as distributed as we would have liked, it offered a better solution. 

Using Weed Block

Originally we bought weed block to line the bins so the soil would not be directly on its plastic container. As the rain simulating testing continued we tried to see what other materials were available, and weed block was one. We decided to try it because we felt it was thick enough to keep the water from being a constant stream.

Weed block between the layers of screen.

                                      

The weed block was by far the material that distributed the water the best. There were still some larger streams of water, but relative to the other materials they were much smaller. Weed block was also the only material that showed improvement by seeing "drops" of water come off of the screen. We thought we might be able to adjust this by pouring the water from a greater height.

                                     

The screen at a higher point above the container did have more "drop-like" water effects. As of right now, the weed block will be the material to use between the layer of screens.

Issues/Problems

1. The screen tended to droop in the center which was also a cause of a water stream instead of droplets. This effect can be seen with all three test cases which is why it was not a fault with one in particular.
2. The method of pouring water was also not the best it could be. We are looking into a material that could sit on the outer layer of the screen initially. This outer layer would pool the water until removed. When removed, the simulated rain can fall in all places at once rather than directly under where we are pouring. 
3. The height of the screen should stay consistent, therefore a structure may be built to keep the screen at a designated distance from the top of the container. 

Soil Density/ Water Content Concern

The properties of soil can vary greatly depending on the water content, and if we don't account for that our data can be extremely erratic. I thought of a process to dry to soil post testing. We could lay it out on a large sheet of the weed block and apply pressure with some paper towels. Then we let it dry in the sun, and maybe finish it off with hair dryer. What do you guys think?

Weekend Update

On Sunday, April 10th, the group went down to Home Depot to get supplies for the project. With that, we can start testing the project and achieve results that will help us make the best project