1138 



Subsurface Geologic Methods 



PROBLEM 



METHOD 



RESULTS 



(4A) 

 MATERIALS - PRECLASSIFICATION 



GRADE LINE 



(48) 

 RESIST 1 V I T Y 



D C POWER- ^ ,-AMPS 



VOLTS . 



S |~1 . 



RESISTIVITY: 2TTA i OHM. Ft 



measure: RESISTIVITY OF EARTH 

 MATERIALS WITH INCREASING 



DEPTH BY EXPANDING "A" 



SPACING. 



(4C) 

 RESISTIVITY DEPTH CURVES 

 RESISTIVITY 



Q I i_L Q_i--i--j 



GRADE LINE 



RESISTIVITY CURVES SHOW 

 LAYER DEPTHS AND CHARACTER 

 OF MATERIAL UNDER ABOVE 

 CONDITIONS. 



(5A) 

 DAM SITE -BED-ROCK PERMEABILITY 



V 



y 



(5B) 

 RESISTIVITY 



SEE ABOVE 



(5C) 

 RESISTIVITY VS. PERMEABILITY 



RESISTIVITY MEASUREMENTS 

 MADE IN DRILL HOLES 



^- DRILL 

 HOLE 



5 

 £ 10 



UJ 



t- 15- 



UJ 



*20 



I" 

 030 



35 



LITERS/M/MIN 



^_ 



DRILL HOLE RESISTIVITY 

 MEASUREMENTS RELATE TO 

 BED ROCK PERMEABILITY 



(6A) 

 TUNNEL SITE ROCK SOUNDNESS 



(6B) 

 RESISTIVITY 



SEE ABOVE 



(6C) 



PROFILE 



resistivity 



resistivity: high low medium 



/ 



FIXED SPACING RESISTIVITY 

 traverses on SURFACE 

 ALONG TUNNEL LINE 



rock: 



hard-i soft] fair i hard 



0"'' AS FOUND 



LOW < 4c X iqS ohm. cm 



MEDIUM 40 • 70 OHM CM 

 HIGH > 70 OHM CM. 



Figure 597. Resistivity methods applied to engineering geology. 



