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electrical piezometers

1. ELECTRICAL PIEZOMETERS User Manual Electrical Piezometers INDEX Introduction Pag 4 Description Pag 5 Filters saturation Pag 6 Preliminary checks Pag 7 Installation Pag 8 Multipoint piezometer Pag 10 Drive in piezometer Pag 12 Removable piezometer Pag 12 Taking measurements Pag 13 Data management Pag 13 Troubleshooting Pag 15 Maintenance Pag 15 Appendix 1 Pag 16 Information contained herein are property of SISGEO S r l This document is subject to change without notification and is subject to be returned upon request No part of this User s Manual may be reproduced in any form without SISGEO s S r l written permission SISGEO S r l Electrical piezometers_EN_ 01_13 Page 2 of 16 Notes on the use of product Symbols Identification SISGEO S r l Electrical Piezometers For a safe and efficient use of the instrument please read carefully the following instructions before starting any operation Any use of the instrument other then the one described in this manual shall be considered at user s full responsibility The same applies for any unauthorized modifications In addition to the hereby listed standards the user must comply with the provisions of the current legislation on the matter of personal safety and health of persons in the workplace SISGEO is not responsible for any trouble breakdowns accidents etc due to the lack of knowledge and or confidence or non compliance
2. lt 200kPa is necessary during the assembly to connect the piezometer to a readout to check the induced pressure and screw slowly the holder on the piezometer in order to avoid overpressures that could damage it Electrical piezometers_EN_ 01_13 Page 6 of 16 Preliminary checks SISGEO S r l Electrical Piezometers Filter saturation and assembly in SLIM piezometers cod PK20xxx For the saturation follow the instruction in the paragraph of LAE filters For the assembly push and turn the holder on the piezometer body In case of HAE filters the operation could take a few minutes The saturation is successful when the liquid leaks from the filter surface In case of HAE filters and for instruments with low full scale lt 200kPa is necessary during the assembly to connect the piezometer to a readout to check the induced pressure and screw slowly the holder on the piezometer in order to avoid overpressures that could damage it Before the installation is recommended to check the instrument connecting it to a readout see Taking measurements The read value has to be similar to the zero value written on the Calibration Report The possible differences could be due to height barometric pressure and for the VW type temperature This operation is possible with saturated or unsaturated filter Please remember that the Calibration Report shows the conditions during the test and it is issued at 115 m s l The a
3. ays to obtain a reliable zero value Example Piezometer 700kPa digit readings S 4 9128digit kPa A 5 222e 07 B 1 955e 01 C 1 886e 03 Lo 7357digit L 6667digit Using Linear factor Li Lo S 6667 7357 4 9128 140 4494 Polynomial factor L1 x A Lix B C Lo x A Lox B C 559 39 419 44 139 95kPa Temperature measure Using a SISGEO readout the temperature is read directly in C If measured the thermistor resistance value must be converted using the formula or the table shown in appendix 1 If the piezometer is installed in an environment with uneven temperature is necessary to correct pressure value already processed using the follow equation P T To K where P correct pressure T excercise temperature To zero temperature K temperature factor can be found on the piezometer calibration certificate Add the obtained correction to the pressure value found with the previous formula Piot P Pr Example K 0 154344kPa C Ti 28 C TO 15 C PT 28 15 x 0 154344 2 006kPa Ptot 139 95 2 006 141 956kPa Electrical piezometers_EN_ 01_13 Page 14 of 16 Troubleshooting Maintenance SISGEO S r l Electrical Piezometers Considering its special application eventual malfunctioning have to be found along the cable Vibrating wire piezometers Unstable measure Cable shield not connected Connect the shield Electromagnetic fields generated by e
4. easuring sensor membrane Thermistor only with VW type Electric cable for the connection with the readout Conical filter tip drive in type Piezometer push in rod drive in type Conical filter tip removable type A ee ee S The filter is an important element and its choice depends on the use and the ground type The sintered stainless steel or vjon filters have a porosity of ca 40Um are called Low Air Entry LAE and are used for most standard applications Their saturation is performed easily on site Ceramic filters have a low porosity and shall keep the saturation of the hydraulic chamber also if submitted to negative pressures suction They are employed when the piezometer is in dry conditions for a long time The ceramic filters are called High Air Entry HAE The saturation of this kind of filters is not easy and has to be done with a suitable device Electrical piezometers_EN_ 01_13 Page 5 of 16 Filters saturation SISGEO S r l Electrical Piezometers Filters saturation and assembly The purpose of filters saturation is to remove the air in filters pores and replace it with water in order to have a faster answer to pressure variations and more accurate measures moreover it prevents ground particles to obstruct filter pores The air entry is the pressure necessary to force the air through a porous filter completely saturated This value is commonly used in geotechnical field and it is pro
5. eters Appendix 1 THERMISTOR TEMPERATURE CONVERSION Resistance to temperature equation 1 A B LnR C LnR 2732 Where T temperature in C LnR natural Log of the thermistor resistance A 1 4051x10 coefficents calculated over the 50 to 70 C span B 2 369x10 C 1 019x10 SISGEO S r l Electrical piezometers_EN_ 01_13 Page 16 of 16
6. hrough the construction and working Pores of compacted unsaturated material contains both water and air and in fine grained soil the pressure difference between the pore water pressure and pore air pressure can be significant For clay embankments piezometers must have an HAE filter to ensure pore water pressure measure and not air In granular materials as sand gravel and rock fill you can use a LAE filter To install proceed as follows ju 4 i mpacted by i Before through and after the installation check the piezometer Dig a trench ca 50 cm width and 30 40 cm deep Saturate the piezometer as previously described For installation in coarse material insert the piezometer in a geotextile bag filled with sand If the piezometer has an HAE filter and has to be installed in an unsaturated ground assemble only the filter without using the geotextile bag In coarse ground dig a hole and insert the piezometer Close the hole with the filling material compacting manually In case of an embankment with big size materials we recommend to cover the hole with saturated sand compacted by hands For installation in unsaturated grounds fix the piezometer in trench wall or dig a little hole and fix the piezometer Lay out the electric cable within the trench in a snake like mode to avoid damages during the embankment settlemen
7. ngines Identify and remove the cause generator antennas welders or high voltage Shield the signal cable lines nearby Grounding not well done Provide efficient grounding Wire not detected Cable cut or damaged Measure the resistance Repair the cable between conductor Red and Black 1509 Cable splicing kit available at 10 Please consider cable length The SISGEO conductor resistance for model OWE116000 is ca 88 Q km Wiring not correct Make proper wiring Resistive piezometers Unstable measure Wiring not correct Make proper wiring OmA measure Cable cut or damaged Repair the cable Overrange Cable splicing kit available at measure SISGEO After sales assistance for calibrations maintenance and repairs is performed by SISGEO s service department The authorization of shipment shall be activated by RMA Return Manufacturer Authorization Fill in the RMA module clicking on http www sisgeo com en assistance repairs Send back the instrument equipment with the complete accessories using suitable packaging or even better the original ones The shipping costs shall be covered by the sender Please return to the following address with suitable delivery document SISGEO S r l Via F Serpero 4 F1 20060 MASATE MI On the delivery document is mandatory to indicate the RMA code received Technical assistance e mail assistance sisgeo com Electrical piezometers_EN_ 01_13 Page 15 of 16 Electrical Piezom
8. ntonite Electrical Piezometers Electrical piezometers are largely used in civil and foundations engineering to monitor groundwater level and to measure pore water pressure Electrical piezometers called closed circuit type are installed in borehole embankments or directly by drive in if the ground features allow the operation How it works the membrane deforms due to water pressure causing the variation of an electric signal measured with a measuring device SISGEO uses two kind of sensors e Vibrating wire e Resistive In the vibrating wire piezometers VW the membrane deformation causes the tension variation of a steel wire stretched between the membrane and the instrument body The vibration frequency is collected from a measuring device This instrument moreover includes a thermistor to measure the temperature The resistive piezometers have a ceramic membrane with molded starin gauge that change their resistance and the electric signal according to membrane deformations due to water pressure The VW piezometers assure an high reliability for long term measures the resistive allow high insulation for example in industrial plants and the possibility to take dynamic measures Electrical piezometers_EN_ 01_13 Page 4 of 16 Description SISGEO S r l Electrical Piezometers Electric piezometer consists in 1 Stainless steel cylindrical body Hydraulic chamber Filter holder and filter M
9. portional both to pores diameter and the fluid used for the saturation Typical values of low air entry are the ones between 3 and 30KPa while typical values of high air entry are the ones higher than 100KPa SISGEO recommends to perform the saturation on site just before the installation LAE Filters Usually the filter must be left in a bucket full of water for at least 24 hours The saturation is better if the water has been previously de aired bringing it to boil for at least 10 minutes and then left to cool Take a bucket with clean water then e submerge the filter holder with the filter e submerge the piezometer turned up and fill the hydraulic chamber e screw the filter holder on the piezometer working underwater Follow the same operations for the assembly in case of saturated filters supplied by Sisgeo HAE Filters using SISGEO saturation device e Remove the air from the chosen fluid usually distilled water bringing it to boil or vacuum until the air bubbles will disappear e fill in the saturation device e screw the filter holder with the filter on the saturation device e screw slowly the saturation device and handle it until you could read on the gauge the value of ca 3 5Bar e wait until filter s surface is not covered with fluid s drops e unscrew the filter holder and screw it on the piezometer working underwater in a bucket In case of HAE filters and for instruments with low full scale
10. t with coarse ground protect the cable with a conduit Cover the cable with fine material in consecutive layers of 5 10 cm each and compact by hands Arrange some bentonite pellets in regular intervals along the cable in order to avoid water leaks and compact manually Mark piezometer position and protect cable end from water seepage Electrical piezometers_EN_ 01_13 Page 11 of 16 SISGEO S r l Electrical Piezometers Drive in piezometer installation Drive in piezometer both ceramic and vibrating wire is a special version suitable to be pushed directly in soft grounds The drilling equipment must tighten the push in rods on the perimeter Otherwise it will be necessary to have a rod with a groove for the cable To install proceed as follows e Arrange the instrument according to usual procedures e Protect the end of the cable with some tape and insert the first push in rod assembled on the first rod The installation can be started from the bottom of the borehole or from the ground level Well y D By in iee a EEEE eee H ji mi m ht ae F Hope ate sae aa Sete saat Se E F i hy eh he ie 5 5 ee a oH He re FE Drive in piezometer Bentonite Concrete bentonite Push in rod mixture e For installation from borehole bottom lower in the hole the push in rods with the piezometer e Connect the piezometer to the readout and check non stop the overpressure val
11. te Black From 5 to 8 piezometers using a multicore cable code OWE1320000 o w w thermistor Thermistor ppt brown white Brown Black RoseyBlack e vew white vetiow Grey White Grey oes ek Buesak Rose WhiteRose ooo oa oo os oo o e O White Violet Yellow Black Orange White Orange Black Red Black White Blue White Green es tight tue wnite tight bue Green White Do not split the conductors to avoid confusion with the colors Note to obtain reliable measures with mA piezometers we recommend a warm up time not less than 10 seconds For automatic measures connect the instrument to a datalogger SISGEO S r l Electrical piezometers_EN_ 01_13 Page 13 of 16 Data management SISGEO S r l Electrical Piezometers The following formulas allow to convert the electrical measures into engineering values Linear factor gt Leng Lete S kPa Polynomial factors Leng Leie X A Leie X B C kPa Leng Engineering reading Lelee electric reading S sensitivity factor A B C polynomial conversion factors S A B C factors are stated on DTE Calibration Report The exercise readings refer to the initial reading zero reading AP pa Li Lo Lo Zero reading kPa L Exercise reading kPa Zero reading shall be taken carefully once the installation is performed and the instrument is in operating conditions For many applications is necessary to wait a few d
12. the drilling a little above the ground level This solution has to be used also during the installation steps Tools needed during installation depth meter pestle bentonite pellets bucket To install proceed as shown in the picture HS LiTE Bentonite T sealing F234 HO oy Docs a ay Hc Eas a8 q 8 a J 5 Ay 2 Q J 100cm Lining casing LN OF OER A OY ap a OI eal RAS a0 2 ee Owe Piezometer Electrical piezometers_EN_ 01_13 Page 8 of 16 SISGEO S r l Electrical Piezometers Suggestions Identify the installation depth on piezometer cable starting from the membrane position engraved on the steel body Before through and after the installation check piezometer measurement Wash the borehole until it leaks clear water Fill in the geotextile bag with sand and insert the piezometer with the saturated filter then put everything in a plastic bag filled with water and dip it in the casing full of water Now break the plastic bag pull out the piezometer and drop it slowly These operations must be carried out always underwater fine sand or gravel ca 2mm Carry out the bentonite cap in several times ca 25 30cm each time Compact with a pestle Pay attention to the cable Verify cap solidity and depth with a depth meter Approximate quantities for the grout mixture 100 of water 50Kg of concrete and 5Kg of bentonite Cable shall always be covered
13. tmospheric pressure lowers approximately 0 1kPa every 10m height We advise to leave the VW model temperature to stabilize for at least 20 minutes before taking any measure The acceptable differences between the measured value and the one shown on the Calibration Certificate with equal conditions are e Extensometer model 1 of full scale 0 16mA e VW model 100digits For low full scale values is necessary to consider the barometric pressure value Indeed on a transducer of 0 2MPa a barometric pressure variation of 50mbar 0 005MPa is like 2 5 of full scale 1 millibar is 1cm of water level Electrical piezometers_EN_ 01_13 Page 7 of 16 Installation SISGEO S r l Electrical Piezometers Installation in boreholes Installation procedures must be defined according to the grounds and the purpose of the measures In general terms you can use the following procedure Boreholes can be executed with continuous core or non core drilling We always recommend to steady the walls with a temporary casing with an internal diameter not less than 85mm 1 piezometer for borehole 110mm 2 piezometers for borehole Avoid the use of mud To install two piezometers in the same borehole are needed two filters and two caps pay attention to stratigraphy and thickness of layers SISGEO recommends to install maximum two piezometers for each borehole To stabilize the bottom of the hole without ground water water level must be kept within
14. to avoid casual damages and protect the end from wet With an higher impermeable soil layer the bentonite sealing should be carried out at the same level of the layer in order to restore the continuity Electrical piezometers_EN_ 01_13 Page 9 of 16 SISGEO S r l Electrical Piezometers Multipoint Piezometer Lately as a result of studies is taking over a new installation method called fully grouted This method is very easy and fast It doesn t expect to use gravel and bentonite to create filter and sealed zones but a mixture of water cement bentonite inside the borehole with the right proportions according to the installation The mixture is injected straight to the drilling This allows to install more piezometers in the same hole and also to install the piezometers in combination with an inclinometer casing Approximately the proportions in weight of the grout mixture are cement 1 water 2 5 bentonite 0 3 We recommend to mix in advance water and cement and then add the bentonite Measures can be taken only after 28 days This kind of installation is suitable with multipoint piezometers where is possible to install up to 8 piezometers in the same borehole P1 P2 P3 Electrical piezometers_EN_ 01_13 Page 10 of 16 SISGEO S r l Electrical Piezometers Installation in fills and embankments Piezometers can be installed in embankments or in core dams to measure the pore water pressure t
15. ues resulting from the push to avoid damages to the sensor if necessary stop and wait for the excessive pressure to disperse e Push in until the chosen depth e Disconnect the piezometer protect cables end with some tape and pull out the rods avoiding any stretch on the electric cable e Connect the piezometer and check the good functioning Close the hole with bentonite balls or a mixture of water concrete and bentonite e Wait until the values are stable and the overpressure is dispersed to take the zero reading Removable piezometer with conic filter tip installation e Lower the piezometer and the weights within the pipe using the kevlar wire within the electric cable e Insert the piezometer in the Casagrande filter previously installed e If the Casagrande filter is double tube you must lower in the 2 tube the steel rod with conic cap and O Ring using the steel wire Electrical piezometers_EN_ 01_13 Page 12 of 16 Electrical Piezometers Taking Manual readings are taken connecting the conductors to a readout according to the measurements following scheme Resistive piezometers rea toop Signal 4 20mA current loop Vibrating wire piezometers VW For the multipoint piezometers From 1 to 4 piezometers using a multicore cable code OWE1160000 P w w thermistor thermistor pea brown White Brown White Green P vew _white Yertow White Grey White Blue Rose White Rose res Whiteyre Whi
16. with with the requirements contained in this manual Check that the instrument has not been damaged during the transport Verify that the package includes all items as well as any requested optional accessories if anything is missing please promptly contact the manufacturer The user must strictly follow all the operations described in this manual Maintenance or repair of the instrument is allowed only to authorized operators These operators must be physically and intellectually suitable For information about instrument or order spare parts request please always specify data written on the identification label When replacing parts always use ORIGINAL SPARE PARTS The manufacturer reserves the right to make changes without prior notice for any technical or commercial requests We ll try anyway to keep the manuals updated in order to reflect product s revisions updates This symbol will be used used to catch reader s attention on the manual Pay special attention to the following instruction Instruments can be identified From a production lot number written on the Compliance Certificate From a serial number s n engraved indelibly on the instrument From a label on the instrument From a label on the cable Electrical piezometers_EN_ 01_13 Page 3 of 16 Introduction SISGEO S r l 280 cm Measure panel Support head assembly Bentonite Piezometer Electric cable Sand Piezometer Be

electrical piezometers

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