Field works. Example 13.

Geophysical imaging for taliks


The survey area is situated in Krasnoyarsk territory

Geophysical survey was carried out for localization of talik zones to the depth 15m in summer season.

For investigation of geoelectric structure of the area was used electrotomography method. The results of processing were geoelectric model along the axis of gas pipe line.

From point 12+22 to point 13+13 there is two-layer structure, which thickness is quite constant. Upper, thawed loam has thickness 2-3m and resistivity 50-400 Ωm. Deeper, there is a frozen loam (resistivity 700-1500 Ωm).

From point 13+13 to point 14+45 to the near-surface part is observed conducting layer (resistivity 30-80 Ωm) thickness about 9m, represents thawed loam and sand. Deeper, there is soil with resistivity 100-200 Ωm correspond frozen loam.

From point 14+45 to point 18+12 (The left bank of r. Solonaya) section is detected as two-layer model. Upper, thawed loam has resistivity 100-300 Ωm and thickness 1-2m. At the base of the model there are layers of frozen loam and sand, which have resistivity values varies in a wide range (from 300 to 5000 Ωm). It should be noted that upper boundary of cryolithic zone determine by drilling data and geophysical data is disagreements to 9 m between point 14+36 to point 14+45. Probably, it is so because a talik zones affect on the data. This talik zones locate near the line of actual profile. Geoelectric section is unstable on account presence the talik zones of near-surface section. It is determine from point 15+00 to point 15+18 (thickness up 5m) and from point 17+16 to point 17+34 (thickness up 5m).

Geophysical imaging for talik's zones

Electrotomography survey allows to solve the main engineering-geological problem – identification of talik zones in permafrost, which compose the survey area. On geological model are determined engineering-geological complexes and local irregularities. Irregularities due to the seasonal process and talik zones.

Electrotomography data were processed with the use of ZondRes2D.