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  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

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

Pressuremeter – Working contd… Test Execution  Valve turned to “Test” position once desired depth has been reached  Constant volume increments of 5 cm 3  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

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

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

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)

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

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

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