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VW2100 Vibrating Wire Piezometer  

Instruction Manual 

 
 

ELM0005P 

RST Instruments Ltd. 

 

Page iii  

 

 

T

ABLE OF 

C

ONTENTS

 

1  I

NTRODUCTION

 ............................................................................................................ 5

 

1.1  Model VW2100 ................................................................................................. 6

 

1.2  Model VW2100-DP ........................................................................................... 6

 

2  V

IBRATING 

W

IRE 

P

RINCIPLE

 ........................................................................................ 6

 

3  C

ALIBRATION

 .............................................................................................................. 7

 

3.1  Field Calibration Check ..................................................................................... 8

 

4  R

EADING 

P

ROCEDURES

 ............................................................................................... 9

 

4.1  VW Instrument Readings .................................................................................. 9

 

4.2  Initial Inspection and Check Readings............................................................... 9

 

4.3  Initial Readings ................................................................................................. 9

 

4.4  Pressure Equation (Using the VW2106 Readout) ........................................... 11

 

4.4.1  Linear Equation ..................................................................................... 11

 

4.4.2  Second Order Polynomial Equation ...................................................... 12

 

5  I

NSTALLATION

 ........................................................................................................... 13

 

5.1  Filter Saturation ............................................................................................... 14

 

5.2  Low Air Entry Sintered Stainless-Steel Filters ................................................. 14

 

5.3  High Air Entry Ceramic Filters ......................................................................... 15

 

5.3.1  One Bar High Air Entry Filters ............................................................... 15

 

5.3.2  Two Bar (or Higher) High Air Entry Filters ............................................. 16

 

5.4  Installation in Full ............................................................................................ 17

 

5.4.1  Compacted Clay ................................................................................... 17

 

5.4.2  Granular Materials ................................................................................ 17

 

5.5  Installation in Boreholes .................................................................................. 18

 

5.5.1  Sand/Bentonite Method......................................................................... 18

 

5.5.2  Fully Grouted Method ........................................................................... 20

 

5.6  Piezometers Drive In Soft Ground ................................................................... 22

 

5.6.1  Installation............................................................................................. 22

 

5.7  Cable Identification ......................................................................................... 23

 

5.8  Cable Routing ................................................................................................. 23

 

5.8.1  Transition from Vertical Borehole to Horizontal Trench ......................... 23

 

5.8.2  Horizontal Cable Runs .......................................................................... 23

 

5.9  Lightning Protection ........................................................................................ 24

 

6  T

ROUBLESHOOTING

 .................................................................................................. 25

 

6.1  VW Piezometer Fails to Give a Reading ......................................................... 25

 

6.2  VW Piezometer Reading Unstable .................................................................. 25

 

6.3  Thermistor Reading is Too Low ...................................................................... 26

 

6.4  Thermistor Reading is Too High ...................................................................... 26

 

7  S

PECIFICATIONS

........................................................................................................ 27

 

8  S

ERVICE AND 

R

EPAIR

 ................................................................................................ 28

 

A

PPENDIX 

A

 

:

 

VW2100

 

C

ALIBRATION 

S

HEET

 ................................................................... 29

 

Summary of Contents for VW2100

Page 1: ...ained 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 Doc...

Page 2: ...ii REVISION TABLE Rev Revision History Date Prepared By Approved By P Corrected typo in Table 7 1 0 05 changed to 0 5 Corrected linear equation in Section 4 4 1 to include F factor corrected minor typ...

Page 3: ...Entry Ceramic Filters 15 5 3 1 One Bar High Air Entry Filters 15 5 3 2 Two Bar or Higher High Air Entry Filters 16 5 4 Installation in Full 17 5 4 1 Compacted Clay 17 5 4 2 Granular Materials 17 5 5...

Page 4: ...ESSURE 32 APPENDIX E THERMISTOR TEMPERATURE DERIVATION 33 APPENDIX F REFERENCES 34 LIST OF FIGURES Figure 1 1 Vibrating Wire Piezometer 0 7 MPa 5 Figure E 1 Thermistor Resistance versus Temperature 33...

Page 5: ...cy of the vibrating wire which is proportional to the pressure being applied to the vibrating wire transducer diaphragm Additionally the VW2106 readout unit will display the transducer temperature dir...

Page 6: ...er Model VW2100 PT 1 2 MODEL VW2100 DP 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...

Page 7: ...ndividually calibrated in the laboratory before shipment Each vibrating wire piezometer is calibrated over its full working pressure range A Linear Calibration Factor CF is established by using the ca...

Page 8: ...on on the saturation of VW2100 piezometers with Casagrande style filters and VW2100 DP piezometers 1 Lower the piezometer to depth in a vertical water filled borehole using the cable markings to accur...

Page 9: ...NGS It is strongly recommended that the instruction manual for the RST VW2106 Readout Unit be read thoroughly before proceeding Failure to become familiar with the function and operation of the VW2106...

Page 10: ...ature and or barometric pressure which will impact the reading accuracy of the vibrating wire piezometers through their intended range Initial zero readings are generally obtained immediately prior to...

Page 11: ...verted to the actual pressure changes using equations in Sections 4 4 1 and 4 4 2 which include corrections for temperature and barometric pressure changes 4 4 1 Linear Equation EQUATION 1 LINEAR EQUA...

Page 12: ...vidual sensor B Polynomial Gauge Factor B in kPa B Unit Second Order Polynomial Expression derived from the VW Piezometer Calibration data for each individual sensor C Polynomial Gauge Factor C kPa Se...

Page 13: ...loped by various agencies and technical specialists Appendix F provides a list of references The following instructions summarize the generally accepted practice for Filter saturation Cable identifica...

Page 14: ...nt Decreased response times due to pressure changes which means increased sensor sensitivity Ensure hydraulic continuity between the pore water and the piezometer diaphragm in unsaturated soils which...

Page 15: ...ble for use on vibrating wire piezometers if salts or other precipitates are clogging the stainless sinter filter Screens are less likely to become clogged by precipitates and other debris found in so...

Page 16: ...e assembled piezometer with the filter housing facing downward at the bottom of a vacuum chamber The vacuum chamber is to have an inlet port at the bottom to later allow introduction of de aired water...

Page 17: ...of the trench Make sure it rests on a bed of hand placed and lightly compacted screened clay Ensure that the cable does not come into direct contact with itself or other cables in the area Always main...

Page 18: ...e carried out in The general method described below will have general applicability to most installations However the Field Engineer must be aware of the unique conditions that may be present in the s...

Page 19: ...cing the bentonite chips until the bentonite level is 30 cm below the required piezometer elevation 3 Pull the drill casing as the bentonite is set in place Be very careful not to bridge or plug the d...

Page 20: ...as taken from the two above technical papers and outlines the basic concepts and methodology of the Fully Grouted Method When using the fully grouted method it is very important that proper filter sat...

Page 21: ...th PCV pipes should break Install piezometers attached to a PVC plastic tremie pipe inside a casing or hollow stem auger Leave in place while casing or auger stem is pulled out Downhole grouting may b...

Page 22: ...dix C which outlines the steps required to saturate a drive point piezometer filter 2 Prepare the rods to be used downhole Lay a sufficient number of rods for the push side by side alternating between...

Page 23: ...ed path as it goes from a vertical to a horizontal position At the collar of the borehole prepare a large radius circular transition path within a cushion of screened sand 5 bentonite mix hand compact...

Page 24: ...on This is especially important prior to backfilling any trenches 5 9 LIGHTNING PROTECTION All RST Model 2100 Vibrating Wire Piezometers have highly reliable surge lightning protection incorporated in...

Page 25: ...is very high or infinite the cable is possibly broken or cut If the resistance is very low the gauge conductors may be shorted 2 Check the VW2106 Readout Unit with another vibrating wire piezometer to...

Page 26: ...t be performed to return the function of the wire connection to normal It is recommended that an RST ELSPLICE4 Electrical Cable Splice Kit for Vibrating Wire Cables be used to ensure a strong and wate...

Page 27: ...7 5 10 MPa Over range 1 5 x FS Temperature Range 20 C to 80 C Resolution 0 025 FS Accuracy 0 1 FS Non Linearity 0 5 FS Zero Stability 0 02 FS year Thermal Zero Shift 0 05 FS C Frequency Range 1200 35...

Page 28: ...W2100 DPC CT Drive point model with drop off shoe 0 07 0 175 0 35 0 7 1 2 3 MPa 50 8mm tip 33 4 body x 130mm VW2100 DPE Drive point model with extension rod 31 8mm x 127mm VW2100 L Low pressure unvent...

Page 29: ...VW2100 Vibrating Wire Piezometer Instruction Manual ELM0005P RST Instruments Ltd Page 29 VW2100 CALIBRATION SHEET...

Page 30: ...he sealing screw is pointing upwards 4 Allow the air within the piezometer to escape Gently tap and move the piezometer around underwater 5 Replace the sealing screw underwater after all the air has b...

Page 31: ...ensure that all air is removed from the inside of the piezometer housing 5 While the piezometer is still immersed in the water thread the drive point back on The drive point should be hand tightened...

Page 32: ...r a Vibrating Wire pressure transducer which has a comparatively low non linearity In this case there will only be a very small difference between the pressure value calculated by the Linear Equation...

Page 33: ...3001 B3 Alpha 13A3001 B3 Resistance to Temperature Equation EQUATION E 1 CONVERT THERMISTOR RESISTANCE TO TEMPERATURE where T Temperature in C Ln R Natural Log of Thermistor Resistance A 1 4051 x 10 3...

Page 34: ...Engineers London pp A5 55 A 7 General Electric 1976 Transient voltage suppression manual G E Semiconductor products Department Syracuse New York A 8 Baker C 1978 Surge Protection for Instrumentation...

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