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The Pencel Pressuremeter

The Pencel Pressuremeter. Sunil Sundaram Foundation Design Spring 2004. About the Pressuremeter. Instrument used to run in-situ soil loading tests by expansion of cylindrical cavity Helps in the calculation of modulus of elasticity of the soil

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The Pencel Pressuremeter

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  1. The Pencel Pressuremeter Sunil Sundaram Foundation Design Spring 2004

  2. About the Pressuremeter • Instrument used to run in-situ soil loading tests by expansion of cylindrical cavity • Helps in the calculation of modulus of elasticity of the soil • Leads to the calculation of lateral pressure acting on the piles. • Consists of two main parts • Read out unit that rests on the ground surface • This unit has both a pressure and volume reading • Corresponding pressure can be obtained with the change in volume in the cylindrical cavity • Probe inserted into the borehole

  3. Pressuremeter - Working • Filling and saturation of the control unit • Control unit should be saturated to ensure no air is trapped in the cylinder or filling lines • Calibrations • Pressure correction • Volume loss correction • Probe Insertion • Probe is connected to EW steel drill rods • Hydraulic pressure used to insert rod

  4. Pressuremeter – Working contd… • Test Execution • Valve turned to “Test” position once desired depth has been reached • Constant volume increments of 5 cm3 • Pressure measured after rest period • Rest period could vary with soil type • On completion of test, deflate probe • Remove probe or advance probe to lower level

  5. Pressuremeter – Working contd… • Interpretation • Draw the raw data curve and corrected pressuremeter curve (Pressure vs. Volume)

  6. Pressuremeter – Working contd… • Each point on the raw curve corresponds to a point on the corrected curve • V corrected = V read – V calibration • P corrected = P read – P calibration + P hydro • Dismantling and Mounting of a Pencel Probe

  7. Automation - Purpose • Current technique is very tedious and error-prone • Automation could: • Reduce human errors and to make the recording process fast • Allow evaluation of rest time required for the stabilization of soil pressure (depending on soil)

  8. Instrumentation • Linear Potentiometer • Measures displacement of a piston causing volume change • Connected in parallel with piston using mounting brackets and linkage rod • Pressure Transducer • Measures pressure corresponding to volume change • Connected in series with existing pressure gauge

  9. Instrumentation contd… • Both assemblies will be small enough to mount within the existing case • Rechargeable power supply used to keep system portable • Setup connected to the serial port of a computer • Analog pressure and volume readings will be converted to digital readings and recorded with help of Analog – Digital converter

  10. Conclusion • Recording of data process is faster • Less manpower required to conduct tests • Less human error

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