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VW2100 Vibrating Wire
Piezometer
Instruction Manual
All efforts have been made to ensure the accuracy and
completeness of the information contained in this document. RST
Instruments Ltd reserves the right to change the information at any
time and assumes no liability for its accuracy.
Copyright © 2019. RST Instruments Ltd. All rights reserved.
Document Number: ELM0005P
Release Date: July 10, 2019
ELM0005P
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Summary of Contents for RST Instruments VW2100-DP
- Page 1 RST Instruments Ltd reserves the right to change the information at any time and assumes no liability for its accuracy. Copyright © 2019. RST Instruments Ltd. All rights reserved. Document Number: ELM0005P Release Date: July 10, 2019...
- Page 2 Prepared Approved Corrected typo in Table 7-1 (0.05% changed to 0.5%); 10-Jul-2019 Corrected linear equation in Section 4.4.1 to include F factor; corrected minor typos throughout; added Revision Table; reworded Section 4.3 for clarity. ELM0005P RST Instruments Ltd. Page ii...
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Page 3: Table Of Contents
VW2100 Vibrating Wire Piezometer Instruction Manual ABLE OF ONTENTS ......................5 NTRODUCTION Model VW2100 ....................6 Model VW2100-DP ................... 6 ..................6 IBRATING RINCIPLE ......................7 ALIBRATION Field Calibration Check ..................8 ....................9 EADING ROCEDURES VW Instrument Readings .................. 9 Initial Inspection and Check Readings............... - Page 4 VW2100 Vibrating Wire Piezometer Instruction Manual B : C ............ 30 PPENDIX ASAGRANDE TYLE ILTER SSEMBLY C : VW2100-DP (D ........... 31 PPENDIX RIVE OINT IEZOMETER D : U PPENDIX SING THE ECOND RDER OLYNOMIAL TO MPROVE THE CCURACY OF THE ...................
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Page 5: Introduction
All parts of the sensor, other than the actual Vibrating Wire are machined from a high-grade stainless steel, selected for its low yield and high corrosion resistance. ELM0005P RST Instruments Ltd. Page 5... -
Page 6: Model Vw2100
VW2100-DP ODEL The RST VW2100-DP Vibrating Wire Piezometer is designed to be driven into unconsolidated fine grain material such as sand, silt, or clay. The external housing is a thick-walled cylinder fitted with a pointed shoe at one end. The opposite end is fitted with a male thread adapter at the cable entry, which fits standard “EX”... -
Page 7: Calibration
The following general information is contained in the Calibration Record sheet: • Model, Serial, and Manufacturing Numbers; • Pressure Range; • Temperature and Barometric Pressure at time of Calibration; ELM0005P RST Instruments Ltd. Page 7... -
Page 8: Field Calibration Check
Ensure the entire space between the instrument diaphragm and the filter stone is filled with water. Refer to Appendix B for more detailed information on the saturation of VW2100 piezometers with Casagrande style filters, and VW2100-DP piezometers. Lower the piezometer to depth in a vertical, water filled borehole using the cable markings to accurately control and set the depth. -
Page 9: Reading Procedures
B-Unit reading without any external pressure being applied. Vibrating wire piezometers are acutely sensitive to pressure changes at zero point as there is no zero-point hysteresis to overcome. The determination of vibrating wire instrument ELM0005P RST Instruments Ltd. Page 9... - Page 10 Surface tension effects within the pore spaces of the filter could affect the zero readings if the filter stone is only partially saturated. This can be a problem particularly at low pressures (less than 350 kPa). Remove the filter ELM0005P RST Instruments Ltd. Page 10...
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Page 11: Pressure Equation (Using The Vw2106 Readout)
, S = Initial and Current Barometric pressure readings in mbar Example for a 350 kPa Range Piezometer CF = 0.11594 kPa/B-Unit = 8776 B-Unit L = 7200 B-Unit = - 0.03413 kPa/ºC = 22.9 ºC T = 5.0 ºC F = 0.1 kPa/mbar ELM0005P RST Instruments Ltd. Page 11... -
Page 12: Second Order Polynomial Equation
= Temperature Correction Factor in kPa/ºC (From the VW Piezometer Calibration Record sheet in each individual sensor) = Initial and current temperature readings in (ºC) = Barometric Pressure Constant = 0.1 kPa/mbar = Initial and Current Barometric pressure readings in mbar ELM0005P RST Instruments Ltd. Page 12... -
Page 13: Installation
Ground fault currents from this type of equipment can easily damage the sensitive low voltage vibrating wire piezometers. Additional steps must be performed on site to ensure complete isolation and adequate grounding of the instrumentation circuits if ELM0005P RST Instruments Ltd. Page 13... -
Page 14: Filter Saturation
24 hours). This will fill the space above the piezometer diaphragm with water. • While keeping the piezometer submerged, slowly replace the filter housing onto the inverted piezometer end, allowing the water to be forced out through the filter sinter. ELM0005P RST Instruments Ltd. Page 14... -
Page 15: High Air Entry Ceramic Filters
Boil the filter assembly in de-aired water for 30 minutes to force all air out of the filter and to saturate the filter material. Place the filter into de-aired water when boiling is completed. ELM0005P RST Instruments Ltd. Page 15... -
Page 16: Two Bar (Or Higher) High Air Entry Filters
After saturation, the transducer must be kept in a sealed container of de-aired water until ready for installation. If de-aired at the factory, a special plastic cap is ELM0005P RST Instruments Ltd. Page 16... -
Page 17: Installation In Full
The granular backfill should contain the same moisture content and be compacted to the same density as the surrounding fill. Care must be exercised to not subject the piezometer instrument to damage during compaction work. ELM0005P RST Instruments Ltd. Page 17... -
Page 18: Installation In Boreholes
The piezometer installation will have to proceed with multiple small withdrawals of the drill casing to minimize the risk of losing the installation if the borehole walls are considered to be unstable or likely to cave or collapse. This method is described ELM0005P RST Instruments Ltd. Page 18... - Page 19 Lower the piezometer into the hole and take the initial readings, as described in Section 4.3. Raise the drill casing 15 cm and backfill the hole around the piezometer with fine, clean sand. Repeat until the sand is 30 cm above the top of the piezometer. ELM0005P RST Instruments Ltd. Page 19...
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Page 20: Fully Grouted Method
The final mix point has to be carefully monitored to ensure that the completed grout remains pumpable. Although the grout mix has a target bentonite content, it may be ELM0005P RST Instruments Ltd. Page 20... - Page 21 Later tremie grouting outside the PVC pipe will result in the piezometers being fully grouted in- place. ELM0005P RST Instruments Ltd. Page 21...
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Page 22: Piezometers Drive In Soft Ground
RIVE ROUND RST Model VW2100-DP is designed to be pushed into place from the surface in soft soil. For deeper installations where driving from the surface would not be possible, the piezometer may be pushed into place from the bottom of a pre-drilled borehole. -
Page 23: Cable Identification
Cover cable completely with a 150 mm lift of 10 mm minus select material. Completely backfill the trench with selected material. Compact it with light hand operated equipment. ELM0005P RST Instruments Ltd. Page 23... -
Page 24: Lightning Protection
(Surge 4C) is damaged by a surge event, the user may easily service the components or replace the board. A connection is made between this enclosure ELM0005P RST Instruments Ltd. Page 24... -
Page 25: Troubleshooting
Check the VW2106 Readout Unit with another vibrating wire piezometer to confirm that the VW2106 Readout Unit is working. The vibrating wire piezometer may have been over-ranged or physically damaged. Inspect the diaphragm and housing for any obvious damage. Contact RST Instruments if necessary. VW P IEZOMETER EADING... -
Page 26: Thermistor Reading Is Too Low
The vibrating wire piezometer may have been over-ranged or physically damaged. Inspect the diaphragm and housing for any obvious damage. Contact RST Instruments if necessary. HERMISTOR EADING IS If the calculated temperature from the thermistor resistance reading is unrealistically low, it is very likely that there is an open circuit or poor connection in the thermistor wiring which is resulting in excessive resistance. -
Page 27: Specifications
Coil Resistance Diaphragm Displacement <0.001 cc @ FS NTC 3k Ω @ 25°C Thermistor Type Filter 50 micron sintered stainless steel (High air entry alumina ceramic filter available for 1, 3 and 5 MPa versions) ELM0005P RST Instruments Ltd. Page 27... -
Page 28: Ervice And Epair
0.7, 1, 2, 3, 5, 7.5 42mm φ x 319mm environment and secondary corrosive protection ERVICE AND EPAIR The product contains no user-serviceable parts. Contact RST for product service or repair not covered in this manual. ELM0005P RST Instruments Ltd. Page 28... -
Page 29: Elm0005P
VW2100 Vibrating Wire Piezometer Instruction Manual : VW2100 C ALIBRATION HEET ELM0005P RST Instruments Ltd. Page 29... - Page 30 Note that with a low-pressure range piezometer (70 kPa), readings must be taken with a readout box while carefully pushing the filter housing on so as not to over-range the sensor. To maintain saturation, the unit should be stored under water until installation. ELM0005P RST Instruments Ltd. Page 30...
- Page 31 Remove the piezometer from the water and slide the wires through the adapter pipe. The unit should be kept under water to maintain saturation if the piezometer is not being installed immediately. Thread the adapter pipe onto the VW2100-DP piezometer. Install the piezometer. ELM0005P RST Instruments Ltd.
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Page 32: C Alculated P Ressure
Linear Equation or the Second Order Polynomial Expression is used. ELM0005P RST Instruments Ltd. Page 32... - Page 33 EMPERATURE where: Temperature in °C Ln(R) = Natural Log of Thermistor Resistance 1.4051 x 10 (coefficient calculated over the -50 to +150°C span) 2.369 x 10 1.019 X 10 IGURE HERMISTOR ESISTANCE VERSUS EMPERATURE ELM0005P RST Instruments Ltd. Page 33...
- Page 34 Simeoni, L., De Polo, F., Caloni, G., Pezzetti, G. (2011); Field Performance of Fully Grouted Piezometers`, Proc 8 International Symposium on Field Measurements in Geomechanics, Berlin. A-15 Contreras, I.A., Grosser. A.T., Ver Strate, R.H. (2012); `Update of the Fully-Grouted Method for Piezometer Installation``, Geotechnical Instrumentation News, Episode 70 ELM0005P RST Instruments Ltd. Page 34...
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