Group Meeting on May 2nd

Meeting goals for tonight are to figure out why some images are not showing up on the site, finish the blog for the blog check, final report drafting and when and where to test next.

Drying the Soil

As mentioned previously, the testing needs to be done while the soil is drier. It does not need to be entirely dried out, as in nature it is possible for a rainstorm to occur before the soil has dried from previous precipitation, but the soil should be around the natural state in which we obtained it. (The soil from southern New Jersey should be very dry, while the soil from Pennsylvania woods is naturally dense). Due to our time constraints we decided to speed the process by using a hair dryer to take moisture out of the soil. With this in mind our next rain simulation will only be done when absolutely necessary.

Blow Drying the Soil:
We took 2-3 "garden-shovel-fulls" at a time in a separate plastic container. We placed the lid over half of the box and used flexible cardboard to keep soil from escaping out the back and the remainder of the top of the box.

Here are some before and after pictures of the soil.

Applied Load Test

This weekend the team decided to conduct a test with only a load applied to the slope (no other factors tested). The slope was built at approximately a 45 degree angle, steeper than built before. At this point in the project, we want the slope to fail so that we can test our solutions to fix that same kind of slope. We placed two bricks on the top of the slope which created a load of approximately 98 N. After watching for 30 minutes, there was no change or collapse in the slope.

The problem with this test was that the soil was still wet from our previous rain simulation. The moisture in the soil caused it to be very closely packed which would prevent it from failure under our tests. The next applied load test will be conducted when the soil is dried out.

Possible Toe Wall Structures

During lab this week we brainstormed ideas for the toe wall, taking into account that the wall may need than just a single layer of bricks in terms of thickness and height.

Full-Scale Grid Materials

In our initial tests of the intra-soil grid we plan to use small, biodegradable planters and pots as materials. However, because of the obvious difference in size between our small scale-models and a full-scale implementation of this grid, we researched different materials that could be used on a full-size grid. We discovered that bamboo is both biodegradable and strong enough for our purposes. Bamboo plates (these for example: http://www.webstaurantstore.com/bambu-063200-9-disposable-square-bamboo-plate-25-pack/999063200.html), which would be structurally similar to the walls of a grid, are already on the market. The grid would be held in place by biodegradable stakes, such as the ones sold here: http://www.arbico-organics.com/product/biodegradable-ground-stakes/garden-tools-supplies. 

Goals for Week 5 Lab

The goals for the lab this week is to start to design the intra soil grid system, work on the toe wall design with the materials we have and to plan out the rest of the week for meeting up.

Rain Simulation Improvements and First Simulation

This week we tried to focus on improving the rain simulation because it is one of the most important aspects of the project. It is the main factor we are considering in our study of soil erosion, therefore it is necessary for our tests to be completed. The team may have to make a trip for more materials, but this weekend we worked with the materials we have already purchased.

The first new material tested was an old t-shirt. First, we tried the t-shirt over the double layered screen but observed that the t-shirt absorbed the water instead of allowing the water to travel through it in a randomized pattern. Our next test was with one layer of the t-shirt, however this was still not an accurate simulation.

The next method we tried was the double layered screen by itself. We had tried this before but wanted to retest it because the materials were with us at the time. We discovered that if the screen was raised above the surface of the bin and the water was poured from a height above the screen, the water was more droplet like and random close to that of rain. We concluded that the height gave the water the droplet like effect while the screen having two layers made it more random. The following video is shown with the screen approximately 32 inches from the surface of the bucket and the water being poured from approximately 16 inches from the screen.

We are still open for testing new ways but after discovering this method was close to ideal we decided to simulate it on our test slope. The test slope has none of the proposed methods to slow soil erosion in place. Initially the length of the slope was 7.25 inches, the bottom leg was 6.50 inches, and the height was 4 inches. The average angle calculated was 30.46 degrees. After the rain simulation the slope length was 7.50 inches, the bottom leg was 6.75 inches and the height was 3.75 inches. These gave an average calculated angle of 28.30 degrees. These minor changes were not visible at first glance of the slope, but they coincide with the effects of soil erosion. The only visible change we saw initially was that the top edge of the slope appeared to be more round than edge-like from before. The following video gives a closer look than what we observed during testing. While watching if you focus on the edge of the slope the soil can be seen sliding down from the "rain."

This method of rain simulation is not finalized but the test was done to see what improvements can be made. Our next tasks are to make the rain fall consistent and determine the proper rate of rainfall.