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What is a Pressuremeter?A pressuremeter is a device which is used to determine the stress strain relations of in-situ soil by pumping it into the certain depth of borehole. It is designed by Menard of France so, it is also called as Menard pressuremeter. From this relations at rest horizontal earth pressure of soil, elastic modulus of soil etc., can be determined. Pressuremeter test on soil is very quick and easy way of finding stress strain relationship of in-situ soil. The results obtained by this test are useful for the design of foundations.
Parts of PressuremeterPressuremeter contains three parts namely:
- Control unit
Procedure of Pressuremeter Test on SoilThe test procedure consists of three steps as follows:
- Drilling borehole
- Positioning of probe in the bore bole
- Conducting test
Drilling BoreholeThe Menard’s pressuremeter is not used to drill the borehole. To drill a borehole separate drilling equipment is used and preferably which causes least disturbance to the soil while drilling. The diameter of the borehole should be in between 1.03 times to 1.20 times the diameter of the probe.
1.03Dp < Dh < 1.20DpDifferent designations are there for the diameter of borehole with respect to diameter of probe and length of measuring cell (l0) and probe (L) which are tabulated below.
|Designation of borehole diameter||Diameter of probe (mm)||Length of measuring cell (l0) (mm)||Length of probe (l) (mm)||Nominal diameter of borehole (mm)||Maximum diameter of borehole (mm)|
Positioning of Probe in BoreholeAfter drilling the hole, the probe is lowered down to the required elevation using cables. The probe should be lowered slowly without disturbing the surrounding soil and the apparatus itself. After reached desired elevation, the probe is fixed using clamping device.
Conducting Pressuremeter Test on SoilAfter the positioning of probe, now it’s time to fill the cells of probe with water and gas. This action is done by using control unit of the pressuremeter. The valves of the control unit are opened which admits water into the measuring cell and gas into the guard cells respectively. Equal pressure is maintained in both the measuring and guard cells. Now, using measuring cell pressure is applied on the soil wall of borehole. The application of pressure can be done by any of the two methods as follows:
- Equivalent pressure increment method
- Equivalent volume increment method