Environmental Resistivity Study in Landfill Showing Lack of Signal Detection

[Janette]

Hello All,

I am a graduate student conducting a shallow subsurface geophysics study over closed landfill cells and have run into a bit of a problem with my data collection.

I have ran traverses spaced 10 m apart running E to W across cells with all traverse lines ran twice using two offset lengths of 2.5 m and 10 m. The obtainable depth of investigation is dependent upon the total array length (rope length connecting my transmitter and 4 receivers as well as all cables connecting the equipment). Therefore, the 2.5 m and 10 m offset gives a depth of investigation of approximately 7.5 m and 9 m, respectively.

I have not had any issues with date collection regarding the E to W traverses, however I have tried to run two tie-in lines running N to S across each cell which crosses over the E - W traverses. The 2.5 m offset tie-ins work just fine throughout all cells but I am unable to get the 10 m offset to collect data. I have also tried shallowing the depth of investigation by using both 7.5 m and 5 m offsets yielding the same results.

I know that the equipment is working properly while trying to collect this data, however a message comes up on the computer console which means that the first receiver is not able to lock on to the signal from the transmitter. I have read forums about the particular equipment that I am using which said that this problem arises when environmental factors restrict communication between the electrodes (transmitter and receivers). I am working in a landfill so I can only speculate as to what could possible cause a loss of or disturbance of the signal. I am also unable to collect core samples due to environmental regulations.

I have reason to believe that the liner of the cell may have caused this communication issue. When I run the tie-in lines starting well outside of the cell boundary, the equipment will collect data at all offset lengths until I reach the cell boundary. Unfortunately, there are a shortage of records kept regarding the construction of any of the older cells which I am currently working on.

Does anyone have any ideas as to what may be causing this issue or any experience in shallow surface resistivity surveying (not borehole such as in petroleum exploration) or landfill construction? Any suggestions would be greatly appreciated!

 

[Studiot]

Hello Janette, I am answering because it is a pity to see no take up of a potentially (pun intended) interesting subject.

I am sorry I can't really help as the only resistivity work I have done has been in unrestricted open fields and I know little about landfill.

Where possible it is always good to correlate one remote technique with another, such as ground penetrating radar, which is better suited to finding obstructions.

I think your comment about the cell liners is the issue to investigate.

You noted no problems parallel to one axis of a rectangular grid, but issues paralle to the other one.
How about running a 45° test?

Finally you might like to consider asking a mentor (by forum private message) to move this to the Earth sciences section, where you might find a better expert.

go well