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Geosense VW PIEZOMETERS, Instruction Manual

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Geosense VW PIEZOMETERS Instruction Manual Download Page 10

10 

Version 1.4 May 09 

may cause damage to the diaphragms if the water they contain is allowed to freeze. 
 
Storage areas should be free from rodents as they have been known to damage 
connecting cables. 
 
No other special requirements are needed for medium or long-term storage although 
temperature limits should be considered when storing or transporting associated 
components, such as readout equipment. 

Summary of Contents for VW PIEZOMETERS

Page 1: ...Version 1 4 May 09 I N S T R U C T I O N M A N U A L VW PIEZOMETERS...

Page 2: ...e Readings 5 2 Preparation for installation 5 3 Installation Procedures Boreholes 5 4 Installation Procedures Trenches Pockets 5 5 Installation Procedures Observation Wells or as Water Level Sensor 5...

Page 3: ...hind retaining walls Assessing soil consolidation Measurement of uplift pressures acting on structural foundations Verification of seepage patterns and models Slope stability monitoring Water level mo...

Page 4: ...iring conditions and resistant to interference from external electrical noise The MGS Geosense range of VW piezometers is supplied in various configurations to suit varying installation environments a...

Page 5: ...wire to oscillate at its resonant frequency The wire continues to oscillate for a short period through the field of the permanent magnet thus generating an alternating current sinusoidal output The fr...

Page 6: ...w Voltage Directive 73 23 EEC as amended by 93 68 EEC The Electromagnetic Compatibility Directive 2004 108 EC The Construction Products Directive 89 106 EEC Equipment description Vibrating Wire Piezom...

Page 7: ...7 Version 1 4 May 09 3 0 MARKINGS Geosense piezometers are labelled with the following information Manufacturers name address Product type Model Serial number CE mark...

Page 8: ...of Vibrating Wire Piezometers manufactured by MGS Geosense 4 2 Handling Whilst they are a robust devices VW piezometers are precision measuring instruments They and their associated equipment should a...

Page 9: ...units eg 0 03612 a calculation must be performed to convert to Hz2 1000 Linear Digits units since the calibration sheet is presented in Hz2 1000 units The Geosense Readout model VW200 displays the re...

Page 10: ...reeze Storage areas should be free from rodents as they have been known to damage connecting cables No other special requirements are needed for medium or long term storage although temperature limits...

Page 11: ...the following procedures will be required to suit specific site conditions 5 1 ZERO Pressure or BASE Readings Vibrating wire transducers differ from most other pressure sensors in that they indicate a...

Page 12: ...With the transducer still submerged in the water carefully remove the filter from the piezometer body by carefully twisting and pulling it leaving both submerged in the water 5 At the free end of the...

Page 13: ...he transducer to the water with the open end upwards but submersed 10 Obtain and record the barometric atmospheric pressure for future use It is best to use a site based reading but a local metrologic...

Page 14: ...14 Version 1 4 May 09 13 Store the piezometer in water until ready for installation or repeat the above just prior to installation Continued from page 13...

Page 15: ...th or observation well installation is probably the next most common It simply allows groundwater from any horizon to flow into the borehole to be registered by the piezometer Where a rapid response i...

Page 16: ...r to placing 5 Bentonite seal Where a sealed pocket is to be formed for the piezometer compressed and dehydrated Bentonite in the form of either pellets balls chips etc is commonly used to form the se...

Page 17: ...the installation of Vibrating Wire Piezometers Fibre measuring tape with a weight added to the end for borehole depth measurement and cable length measurement Shovel for placing and levelling fill by...

Page 18: ...nse and a gen eral understanding of the sub surface conditions There are many approaches to piezometer installation and in addition to these broad installation guidelines MGS Geosense are committed to...

Page 19: ...ole Be sure not to let the pellets balls plug or stick to the inside of the casing by checking the depth using a weighted tape Ensure that the Bentonite level always remains below the bottom of the ca...

Page 20: ...there is enough slack cable to prevent the casing pulling the piezometer back up the borehole This will have to repeated whenever casing is to be raised or removed When a section of casing is removed...

Page 21: ...maining void with Grout as shown in the grouting procedure See Section 5 6 15 The piezometer installation is now complete but the initial in situ piezometer readings have yet to be recorded Since the...

Page 22: ...se of the borehole slowly drop Bentonite pellets balls down the borehole Be sure not to let the pellets balls plug or stick to the inside of the borehole Feeding pellets balls in to the borehole too q...

Page 23: ...hould now be recorded Since the piezometric balance may have been disturbed by the installation operations a series of piezometer readings may have to be recorded so as to determine when the pressure...

Page 24: ...shed to the required elevation the rods and adaptor can be extracted leaving the piezometer in place Where drilling rods are to be used to push the piezometer only into the base of the borehole it is...

Page 25: ...occur The calibration and Zero values would then be invalidated The piezometer would not then provide any useful data 7 If necessary use hydraulic equipment rig head or jacking ram to apply gradual l...

Page 26: ...tended location referring to the marks placed on the piezometer cable Since no sand filter will be installed the piezometer must be supported in the borehole by its cable so that the grout can be plac...

Page 27: ...ively to maintain short term saturation in highly permeable tidal locations for example piezometers can be installed with their filter downwards in a small plastic container filled with saturated coar...

Page 28: ...pocket as shown 6 Coil the cable in the pocket to form a loop as shown This helps to reduce the risk of cable damage due to excessive settlement or stretching 7 Lay a section of the cable into the tr...

Page 29: ...be installed Check the elevation of the pocket to ensure that the piezometer will be installed at the correct level See sketches for level details 4 The piezometer can be either placed in the pocket a...

Page 30: ...ezometer by hand and using only light hand held machines around the cable 11 Complete the cable laying operation snaking the cable in the trench only where specified and backfill the trench with grade...

Page 31: ...eters are available In these instruments the rear of the diaphragm is vented to atmospheric pressure by a fine tube included in the special cable This removes the need for barometric compensation as b...

Page 32: ...to batch it is important to use representative samples of the material that will be used on site when preparing samples for lab testing and mix design Where the grout is to be used to backfill for a...

Page 33: ...06 portable readout 1 Connect signal cable from the sensor to the readout following the wiring colour code Conductor colours may vary depending upon the extension cable used Commonly these are RED VW...

Page 34: ...Period units e g 0 03612 or 3612 depending upon the readout used the first step to producing an engineering value is to convert the reading to Linear Digits Hz2 1000 Two examples of this calculation c...

Page 35: ...each factor or at the end of the equation 1 psi 0 7031 mH2O for example An instrument calibration sheet similar to the example in the appendix of this manual includes the following information Model...

Page 36: ...units Seconds 7 to Metres of Water mH2O using a Linear equation is given below Site Zero Reading 3235 Zero Converted to Linear Digits 9555 5 Calibration Factor for mH2O K 0 18159 Current Reading 3289...

Page 37: ...e applied Either a special barometric transducer or an additional low pressure piezometer can be used to measure atmospheric pressure The following is an example of how to carry out the correction usi...

Page 38: ...y However if a low range piezometer is suspended in a shallow standpipe or well it may be affected by day to day changes and seasonal changes in temperature In this instance temperature corrections co...

Page 39: ...rade 17 4 stainless steel There is also a Nitrile rubber O ring sealing the diaphragm and the stainless steel body It would only be necessary to resort to dissolving any build up if it either blocked...

Page 40: ...40 Version 1 4 May 09...

Page 41: ...tection Semitron Bi Polar 230V Excitation Pluck or Swept Frequency Filter Options Ceramic 3 bar air entry Sintered Stainless Steel 316 50 Micron Standard Pressure Ranges When the temperature has stabi...

Page 42: ...ilter assembly Civil engineering sites are hazardous environments and instrument cables can be easily damaged if they are not adequately protected Geosense can therefore provide the following parts th...

Page 43: ...mination please contact MGS Geosense for details Inspection estimate It is the policy of MGS Geosense that an estimate is provided to the customer prior to any repair being carried out A set charge fo...

Page 44: ...ch are determined to be defective upon inspection at the factory Shipment of defective part or parts to the factory shall be at the expense of the Purchaser Return shipment of repaired replaced part o...

Page 45: ...45 Version 1 4 May 09 VW piezometer specification Mikolit specification Bentonite specification Sample VW piezometer calibration sheet 12 0 APPENDIX...

Page 46: ...is a division of Marton Geotechnical Services Ltd Geotechnical Centre Rougham Industrial Estate Rougham Bury St Edmunds Suffolk IP30 9ND England Tel 44 0 1359 271167 Fax 44 0 1359 271168 email info m...

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