Monday was another very productive day. We completed testing on the Lake Superior sand and F-50 sand using the constant head method, however those k-values obtained were not all that similar with the k-values obtained using the falling head method. We felt that the constant head method, had a larger chance of error, so we are going to proceed with the falling head method.

Due to this decision, in the afternoon, we ran more tests on the Lake Superior sand to get a total of 10 k-values and average them. We decided on this because the more trials we have, the better our statistics will turn out. Each time we placed the column into the sand we would record the level of how far the column was in the sand, the height of the water, the initial and final heights the water drops, and the time. We would run three tests without removing the column and take the average of those three tests. Then we would take the column out, wait 5 minutes for the sand to settle and repeat that procedure until we had 10 k-values. After testing the Lake Superior sand with that method, we then did the same for the F-65.

While Jessica and I were performing those experiments, David was experiencing the joys of Matlab by testing what would happen when we have two layers of sand. From the computer simulations, we will soon be trying out what happens in the lab setting when we put two layers of various sands in the cylinder. Hopefully what we find out that the lab will be similar to the computer simulations on Matlab.

As one might expect, the MODFLOW calculations for the K values when the column is put through two layers of different sands is in between the values for the two separate sands. Also the deeper the column is pushed into the second(bottom) layer the more of an effect it has on shifting the K value away from the value of the first(top) layer. We also discovered that boundaries effect the calculated K value through MODFLOW to a greater degree than what we observed in our previous testing. We plan to use the specific K values we are determining from our sands to input as layers in MATLAB and try and replicate the results in the lab.

ReplyDelete