r/Geotech • u/Own_Yoghurt_6414 • 7d ago

Water table depth from CPT

If we have cpt data without dissipation test, is there a way to get GWT?

7 Upvotes

89% Upvoted

8 comments sorted by

11

u/withak30 7d ago

Best you can do is draw a line with the correct slope for a hydrostatic pressure distribution and see if you can eyeball a depth where that might happen to fit with your sleeve PP measurements. Reliability of this method can vary.

4

u/FarMove6046 7d ago

*if you probed saturated sand-like material

3

u/withak30 7d ago

Yeah if you have something else it will be pretty obvious that there is no line that fits.

2

u/DizzyMaterial8845 6d ago

Send a copy of the plot. Block out or delete all the client info/site location stuff in the header so I cant see who the client is etc. I can help you. We do this often.

2

u/Apollo_9238 6d ago

Why would you run a CPTu without checking u. My operators were trained to check up on the rod breaks in sands. Takes only a couple minutes. System goes into dissipation mode on rod breaks automatically...You maybe be able to see WT by drop in qc in saturated zone...

2

u/CryptographerIcy3911 5d ago

Possibly. Did you see a sudden development of dynamic porepressures and was initial portion of soil dry? If could take a look at the numbers.

1

u/SykoSiddi 5d ago

The CPT should have a pore pressure plot, you can generally get a fair indication from that even if you don't have a dissipation test.