STABILITY OF SLOPES IN CLAYSHALES INTERBEDDED WITH COLUMBIA RIVER BASALT

THE COLUMBIA PLATEAU IN THE NORTHWESTERN PART OF THE UNITED STATES COMPRISES MORE THAN 200,000 SQUARE MILES OF MIOCENE AND PLIOCENE BASALT FLOWS. THIS SERIES OF BASALT FLOWS, WHICH IS KNOWN COLLECTIVELY AS THE COLUMBIA RIVER BASALT, IS OF INTEREST TO SOILS ENGINEERS PRIMARILY BECAUSE OF NUMEROUS CLAY-SHALE INTERBEDS. WHERE A THICK CLAY-SHALE INTERBED IS EXPOSED IN A VALLEY WALL, SUCH AS IS COMMON ALONG THE COLUMBIA RIVER AND ITS TRIBUTARIES, IT IS PARTICULARLY SUSCEPTIBLE TO SLOPE STABILITY PROBLEMS. IN 1964, FOR INSTANCE, NINE CUTS FAILED DURING RELOCATION CONSTRUCTION OF A HIGHWAY AND TWO RAILROADS NEAR ARLINGTON, OREGON, BY THE U. S. ARMY CORPS OF ENGINEERS. THE STABILITY OF THESE SLOPES IS DICTATED BY THE PRESENCE AND ORIENTATION OF FRACTURES WITHIN THE CLAY SHALES. THESE FRACTURES ARE THE RESULT OF INTERNAL SHEARING MOVEMENTS RELATED TO THE PREVIOUS GEOLOGICAL HISTORY OF UPLIFT AND FOLDING OF COLUMBIA RIVER BASALT. ADEQUATE SLOPE STABILITY ANALYSIS REQUIRES INVESTIGATION OF THE FRACTURES THROUGH A COMBINATION OF GEOLOGICAL INTERPRETATION AND A SELECTIVE SOIL TESTING PROGRAM. /AUTHOR/

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Filing Info

  • Accession Number: 00235830
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jan 26 1971 12:00AM