PORE WATER PRESSURE MEASUREMENT IN FIELD INVESTIGATIONS

MEASUREMENT OF PORE WATER PRESSURE IN CONNECTION WITH FIELD INVESTIGATIONS IS TREATED IN PRINCIPLE. IT IS SHOWN THAT THE ACCURACY AND SENSITIVITY IN MEASUREMENTS, TOGETHER WITH THE VOLUME FACTOR OF THE INSTRUMENT AND THE EQUIVALENT FILTER DIAMETER, DETERMINE THE POSSIBILITY OF MEASURING VARIABLE PRESSURES, AND GOVERN THE TIME LAGS. THE DEVELOPMENT OF PORE WATER PRESSURE METERS IS DESCRIBED. THIS DEVELOPMENT RESULTS IN A SYSTEM OF INTERCHANGEABLE PARTS (LONG FILTER, SHORT FILTER, OIL-FILLED PICK-UP, ELECTRO PNEUMATIC PICK-UP, RECORDING INSTRUMENTS, AND A PRECISION INSTRUMENT). DISTURBANCES DUE TO TEMPERATURE CHANGES AND GAS BUBBLES ARE ELIMINATED. IT IS RECOMMENDED THAT THE SMALLEST ACCURACY AND SENSITIVITY IN MEASUREMENTS BE ESTIMATED BEFORE STARTING PORE PRESSURE MEASUREMENTS. IT IS ADVISABLE TO ESTIMATE THE GREATEST PROBABLE CHANGE IN PORE PRESSURE WITH THE TIME AND PERMEABILITY OF THE SOIL. IT IS DESIRABLE TO USE QUICK-RESPONSE MEASURING SYSTEMS, SINCE ERRORS DUE TO GREAT TIME LAGS ARE LEAST PROBABLE IN THESE SYSTEMS. IN CLAYS THIS CALLS FOR CLOSED MEASURING SYSTEMS RATHER THAN FOR ORDINARY OPEN PIPES, BECAUSE, IF THE FILTERS ARE GREATER THAN A DEFINITE SIZE, IT IS EASIER TO DECREASE THE MEASUREMENT TIME LAGS BY REDUCING THE VOLUME FACTOR OF THE INSTRUMENT THAN BY INCREASING THE FILTER AREA.

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Filing Info

  • Accession Number: 00234460
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Aug 12 1994 12:00AM