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https://nap.nationalacademies.org/catalog/27432/critical-issues-in-transportation-for-2024-and-beyond

ELECTRO-OSMOTIC STABILIZATION OF SOILS

A REVIEW IS PRESENTED OF THE PRINCIPLES OF PRACTICAL APPLICATIONS OF ELECTRO-OSMOSIS WITH PARTICULAR ATTENTION TO THE STABILIZATION OF NATURAL AND EXCAVATION SLOPES IN FINE-GRAINED SOILS, CONSISTING OF THREE PARTS: A DISCUSSION OF PRINCIPLES OF ELECTRO-OSMOTIC FLOW THROUGH CAPILLARIES, A DESCRIPTION OF VARIOUS PHENOMENA WHICH RESULT WHEN APPLYING ELECTRO-OSMOSIS TO COMPRESSIBLE, FINE-GRAINED MATERIALS, AND A PRESENTATION OF PRACTICAL APPLICATIONS IN EARTHWORK AND FOUNDATION ENGINEERING. THE AUTHOR REVIEWS THIS THEORY AND RESEARCH INTO ELECTRO-OSMOSIS STABILIZATION OF SOILS, FROM THE TIME OF HIS FIRST EXPERIMENT WITH PASSING ELECTRIC CURRENT THROUGH A SAMPLE OF CLAY. AN ATTEMPT TO STUDY THE EFFECTS OF ELECTRO-OSMOSIS ON COMPRESSIBLE, FINE-GRAINED MATERIALS, USED THE FOLLOWING TESTS: (1) ELECTRODES WERE COMPLETELY SURROUNDED BY THE MATERIALS TO BE TESTED, OR ARE IN CONTACT WITH THE ENDS OF THE SPECIMEN WHICH HAVE NO ACCESS TO FREE WATER, (2) THE ELECTRODES WERE IN CONTACT WITH THE ENDS OF THE SAMPLE TO BE TESTED WITH FREE WATER ACCESSIBLE THROUGH THE ELECTRODES TO THE END FACES OF THE SAMPLE, AND WITH EXTERNAL PRESSURE APPLIED TO THE SAMPLE THROUGH THE ELECTRODES, THUS COMBINING ELECTRO-OSMOSIS WITH AN ORDINARY CONSOLIDATION TEST, (3) THE ELECTRODES WERE IN CONTACT WITH THE ENDS OF THE SAMPLE TO BE TESTED, WITH FREE WATER ACCESSIBLE THROUGH THE ELECTRODES TO THE END FACES OF THE SAMPLE, BUT WITHOUT APPLICATION OF EXTERNAL PRESSURE, AND (4) THE ELECTRODES WERE SEPARATED FROM THE END FACES OF THE SAMPLE BY SPACE FILLED WITH WATER SO THAT THE SPECIMEN HAS ENTIRELY FREE ENDS. THIS SYSTEM IS TERMED AN OPEN SYSTEM AND THE FIRST ONE IS REFERRED TO AS A CLOSED SYSTEM. TEST RESULTS OF THESE TWO SYSTEM TESTS ARE DESCRIBED. OBSERVATIONS WHEN TESTING CLOSED SYSTEMS SHOW: (1) PROGRESSIVE DECREASE IN WATER CONTENT AND CORRESPONDING PROGRESSIVE CONSOLIDATION OF THE CLAY STARTING AT THE CATHODE, (2) THE RATE OF DISCHARGE OF WATER AT THE CATHODE IS CONTINUOUS FOR MANY WEEKS AT ALMOST CONSTANT RATE AND FINALLY DROPS OFF GRADUALLY, WITH THE CORRESPONDING DECREASE IN THE ELECTRIC CURRENT, AND (3) FOR A VERY SHORT PERIOD AFTER THE START OF THE TEST, WATER DISCHARGES AT THE ANODIC FACE. WHEN TESTING OPEN SYSTEMS, IT IS OBSERVED THAT THE ENDS OF A CLAY SAMPLE ARE FREE AND SEPARATED FROM THE ELECTRODES BY A SPACE FILLED WITH WATER. THE PHENOMENA THAT START AT THE CATHODE ARE VERY SIMILAR TO THOSE DESCRIBED FOR THE CLOSED SYSTEM. HOWEVER, AT THE ANODIC PHASE, DEPENDING ON THE MAGNITUDE OF THE POTENTIAL GRADIENT, THE CLAY EITHER SWELLS INTENSIVELY OR DISINTEGRATES BY PROGRESSIVE SLAKING. IN CONTRAST TO THE INSTABILITY AT THE ANODIC PHASE, THE CATHODIC PHASE REMAINS PERFECTLY STABLE AND THE STRENGTH OF THE CLAY AT THAT END INCREASES BECAUSE OF PROGRESSIVE CONSOLIDATION. IT IS SHOWN THAT BY MEANS OF ELECTRO-OSMOSIS ONE CAN MOVE WATER IN THE PORES OF FINE-GRAINED SOILS MUCH MORE EFFECTIVELY THAN BY GRAVITY, AND THAT COMPRESSIBLE FINE-GRAINED SOILS CAN BE CONSOLIDATED.

  • Supplemental Notes:
    • Vol 39, No 1, PP 51-83, 11 FIG, 8 PHOT, 19 REF
  • Authors:
    • Casagrande, A
  • Publication Date: 0

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  • Accession Number: 00231378
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Aug 15 2004 2:41AM