Amount of Time Compacted Soil in Layers Holds Back Water

Purpose

The purpose of this experiment was to determine the effect of dirt compaction on the ability of dirt to hold water in a simulated levee.

I became interested in this idea when I read in the newspaper that New Orleans had been flooded and destroyed because a levee had broken.

The information gained from this experiment could protect people from getting their homes destroyed and being killed by floods because levees weren’t compacted in layers enough. Lots of people would care, especially engineers trying to build or protect people with levees.

Hypothesis

My first hypothesis was that the more compacted layers there were, the longer it would hold back water.

I based my hypothesis on the fact that earthen dams and levees are usually built layer by layer with compaction of each layer before the next one is added.

Experiment Design

The constants in this study were:

•    Width of PVC pipe

•    Length of PVC pipe

•    Amount of water put in PVC pipe

•    Type of water put in PVC pipe

•    Amount of dirt put in PVC pipe

        •    Type of dirt put in PVC pipe

•    Temperature where testing

•    Time brick compacted dirt

The manipulated variable was the number of layers that were compacted.

The responding variable was the amount of time it took before the dirt plug broke.

To measure the responding variables, I used a stopwatch and started it when I put the water in and stopped it when plug broke.

Materials

Procedures

1.    Build system

a.    Connect the 133cm in length of PVC pipe to the 2in PVC pipe elbow

b.    Connect PVC pipe valve to the elbow

c.    Build plugs

i.    Put 473ml of dirt in the 30.5cm length of 2in (5cm) PVC pipe

ii.    Place compactor in PVC pipe on dirt then place a 16.78kg brick

for 4 seconds on the circle to compact the dirt.

iii.    Repeat steps i. - ii. until an 8 layer plug is created with 8 compactions.

iv.    Repeat steps i. - iii. until 5 plugs are created

v.    Repeat steps i. – iv., reducing layers by half and doubling the time the brick sits on the circle compactor

1.    For the first repetition, reduce the layers to 4 and double the compaction times to 8 seconds

2.    For the second repetition, reduce the layers to 2 and double the compaction times to 16 seconds

3.    For the third repetition, reduce the layers to 1 and double the compaction times to 32 seconds

2.    Ready Experiment

a.    Place plug tube horizontally into PVC valve so that side with the dirt is away from the valve.

b.    Make sure the valve is shut

c.    Support so the long pipe is vertical

3.    Conduct Experiment

a.    Fill vertical pipe, 133cm with tap water to the top

b.    Start the stopwatch when you turn the valve

c.    Stop the stop watch when the plug breaks and record

4.    Repeat with other dirt plugs in this compaction group

5.    Repeat with other compaction groups

6.    Average results within each group

Results

The original purpose of this experiment was to determine the effect of dirt compaction in layers on the ability to hold water.

The results of the experiment were inconsistent because there is no recognizable trend. The results were low then high having no recognizable relationship.

Conclusion

My hypothesis was that the more compacted layers there were the longer it would hold back water.

The results indicate that this hypothesis should be rejected, because of the inconsistence results. The problem is that the harder you compact it the plug is compacted so great there is no path of air for it to follow instead of the plug breaking it is pushed out by the pressure. Though if you are compacting the plug little air cracks will be left. If the cracks are found by the water it will lead it out when you start to see the water come out it erodes half of the plug in one second. The problem is that the air cracks maybe harder to find.

After thinking about the results of this experiment, I wonder if the type of material used as a plug would make a difference in the time it held water. I also wonder if the amount of time the soil was being compacted would matter at all.  For example if each compaction lasted 64 seconds instead of 32, would that improve the water resistance?  What if the dirt was dry, damp, or frozen?  One could also test the amount of dirt used in the plug.  Would twice as much dirt double the time water was held?

If I were to conduct this project again I would conduct more trials probably ten or 12.  I would also test a plug with a larger number of layers, perhaps 16.

Researched by Connor H