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Contents
1. 6 Section 4 Frequency of 7 Section 5 Data Interpretation 8 5 01 Press re 5 s ini Mex 8 5 02 Pore Pressure c ila ea Tider 8 5 03 Data Reductiont ee ip da OE 8 Figure 1 Push In Pressure Cell Piezometer 11 Figure 2 Installing With Drill Rig Example Only 12 Figure Jack in Installation 13 Figure 4 Jack In Installation from a tunnel 13 Figure 5 Hydraulic Jack in Installation 14 Figure 6 Typical Time Vs Total Stress Chart 15 Figure 7 Conversion 16 Figure 10 EU Declarati2. e e O ee uz uu 77 000 OOL Dissipation of earth pressures measured by push in spade pressure cells in London Clay after Tedd and Charles 1983 User Manual 15 Figure 7 Conversion Table Pressure Stress amp Modulus of Elasticity 10 197 10 000 9 869 102 2 335 2 7500 6 9 145 04 20886 0001 h 0 0100 ni X 0 1022 0 3352 7 5006 0 0 14504 20 886 9 807 x 1 0 9807 09678 10 017 32866 73556 09139 14 223 20481 0 100 1000 11 0197 1 0 9869 10 215 33 515 75006 0 9320 14 504 2088 6 0 1013 101 33 1 0332 1 0132 1 10 351 33 959 76002 0 9444 14 696 21162 9 788 x 9 983 x 9 789 x 9 661 x 9 124 x si 9 7885 93929 9 799 hos 1 32808 73424 P 14198 20445 2 983 x 3 043 x 2 984 x 2 945 x 2 781 103 29835 ga ga 03048 22377 2721 0 43275 62 316 1 333 1 3595 1 333 1 315x 1 362 x 4 469 x 1 243 x 1 934 x 10 01933 1035 hos hoe 10 1102 1 103 i9 2 7846 0 1073 107 3 1 0942 1 0730 1 0589 10 960 35 960 1804 78 1 15 562 22400 6 895 x 7 031 x 6 895 x 6 805 x 6 426 x Di 6 895 7 021 0529 07043 23108 51714 9 5 144 00 4 788x 4 788 4 883 x 4 788 x 4 725x 4 891 1 605 4464x 6 944x 10 10 10 107 107 10 10 10 10 User Manual 16 Figure 8 Sample Calibration Certificate User Manual itmsoil Bell Lane Uckfield East Sussex t 44 0 1825 765044 e sales itmsoil com TN22 1QL Unite
3. 0 08 0 10 223 0 801 115 0 11 0 09 221 0 900 364 0 04 0 00 219 0 998 524 0 15 The zero reading should be established on site by the user on installation The site value of C must be calculated using the formula C BRO The instrument detailed hereon has as applicable been tested and calibrated in accordance with procedures which are part of our 1809001 2008 Quality Management System and unless otherwise indicated performs within 0 05 as specified Thus the In Certified By Line Manager 17 Figure 10 EU Declaration of Conformity DECLARATION OF CONFORMITY WITH COUNCIL DIRECTIVE 73 23 EEC as Amended by 93 68 EEC Date of Issue 12 October 2006 Doc Ref 06 Directive 12123 Low Voltage Directive as amended by 83 58 EEC Conforming Apparatus All Vibrating Wire Instruments Manufactured by Soil Instruments Ltd see pages 3 10 of Technical File Manufacturer Soil Instruments Ltd Responsible Person Chris Rasmussen Sail Instruments Ltd Bell Lane Uckfield East Sussex TN22 1QL Standards Referenced Annex of 1 a 2 b 2 2 d 3 b amp 3 Directive Technical File Soil Instruments Ltd EU Low Voltage Directive 7 3 23 EEC as 68 EEC Technical Documentation Issue 1 October 2006 Vibrating VVire Instruments We hereby certify that the apparatus described above conforms with the protection requirements of 72 23
4. Low Voltage Directive as amended by 93 68 EEC on the approximation of the laws of the Member States relating to Low Voltage Equipment Signed jan Signatory Chris Rasmussen Technical Director User Manual 18 Appendix A Troubleshooting Guide If a failure of any vibrating wire transducer or the electrical cable is suspected the following steps can be followed The transducers themselves are sealed and cannot be opened for inspection The Troubleshooting Flowchart should also be followed if any instrument failures are suspected The steps below and the Troubleshooting Flowchart are applicable generally to any vibrating wire instrument STEP 1 Before any of the following steps are followed the portable data logger should be used to verify the stability of the reading and the audio signal from the portable logger should be heard An unstable wildly fluctuating reading from a transducer or an unsteady audio signal are both indications of possible problems with instruments or their related electrical cables If a portable data logger is giving faulty readings or audio signals from all transducers a faulty readout unit must be suspected Another readout unit should be used to check the readings from the transducers and Soil Instruments should be consulted about the faulty readout unit STEP 2 The resistance across the two conductors of the electrical cable should be checked This can be done using a multimeter device acr
5. pipes are turned in a clockwise direction until the adaptor disconnects at the extension pipe User Manual Section 4 Frequency of Observations Observations on the pressure cell piezometer should be taken very soon after installation even before grouting has been carried out minutes rather than hours Several readings should be taken during the first day and a reading every day for the subsequent 3 to 4 days A reasonable number of readings during the first 10 days after installation will ensure the pressure cell is functioning properly in the short term and provide a typical pressure time dissipation curve see Figure 6 The frequency of observations in the long term will depend on the reason for the installation If only a knowledge of the in situ stresses is required and no changes are expected then weekly readings for about a month after the first 10 days will probably be sufficient The cell could be removed and installed elsewhere On removing a cell it is important to check that the initial pre set zero is the same as that on installation Where pressure cells have been installed permanently to monitor changes in earth pressure such as adjacent to a retaining wall frequency of readings will depend on the construction operations Frequent readings between construction operations will give confidence in the observations User Manual Section 5 Data Interpretation 5 01 Pressure Measurements Original In Situ Pressures The acti
6. are as above User Manual RO is the Linear base or zero reading Please note that the sign of the re calculated value of C should be the same as the original value of C so if the original is negative then the recalculated value should also be negative Conversion to engineering units other than the units of calibration would best be done after conversion using a factor calculated using the same principles as stated in the last paragraph of the Period unit section Please see conversion factors in Figure 7 User Manual 10 Figure 1 Push In Pressure Cell Piezometer e o on oO en a f I j _ I E Es o E e AN 8 AN EE i b 1 I E 2 1 CD ID Double Coupling Piezometer Transducer User Manual Cell Transducer Pressure 11 Figure 2 Installing With a Drill Rig Example Only User Manual Figure 3 Jack in Installation User Manual 13 Figure 5 Hydraulic Jack in Installation User Manual 14 Figure 6 Typical Time Vs Total Stress Chart Total stress RN m2 25 N W 3 Q e Q Q Be o o e OOL 669845 8 410220 5595 BOI119A 0001 sojnulul Jo uonejjeisur JUIS u 000 OL gunssald uepanqJ4aAQ
7. ationship between the square of the measured frequency and the applied force Engineering units of measurement maybe derived from the frequency based units measured by vibrating wire readouts in 3 traditional ways From Period units and from Linear f 2 1000 units using two methods a simple Linear equation or a Polynomial equation Calculation using Period units The following formula is used for readings in Period units E K 10 7 P0 2 10 7 P1 2 Where E is the Pressure in resultant Engineering units K is the Period Gauge Factor for units of calibration from the calibration sheet PO is the Period base or zero reading P1 is the current Period reading User Manual 8 This method of calculation is used by the Soil Instruments Vibrating Wire loggers models RO 1 VW 1 or 2 and with serial numbers starting VL or TVL internal processors for calculating and displaying directly on the loggers LCD screen the required Engineering based units The loggers require Period base or zero reading units for entering into their channel tables to calculate and display correctly the required engineering units If an Engineering based unit is required other than the units of calibration then the correct K factor will have to be calculated using the standard relationship between Engineering units For example if the units of calculation required were in KGF Cm and the calibration uni
8. bsequent calculations Having taken the zero reading with the pressure cell piezometer down the borehole and lowered it to the bottom of the borehole the cell is advanced such that the centre of the active part of the cell is at least 0 5m below the bottom of the borehole Before pushing the pressure cell piezometer ensure the push in adaptor and the cap is connected on the upper end of the installation pipes to allow the cables to come out of the pipes and to allow the pushing load to be applied to the installation pipes The force required to install the pressure cell piezometer 0 5 1m beyond the end of the borehole in a clay having a shear strength of approximately 150 mN m is between about 1 5 and 2 tonnes Most of the reaction required however is to push the boss of the cell and the installation pipes into the ground Various methods of pushing the pressure cells piezometer into position have been used The cell needs to be pushed in steadily Often the drill used to bore the hole can be used to apply the necessary pushing force Such an arrangement is shown in Figure 2 If the drilling rig is not suitable i e a shell and auger rig or if the borehole was hand augered the arrangement shown in Figure 3 could be used This consists of a cross beam which is anchored to ground pickets via two pull lifts User Manual 3 03 Horizontal Hole Installation procedure for horizontal holes is much the same as for vertical holes however the prob
9. cable can then be spliced in accordance with recommended procedures User Manual 19 R is very high R less than 800 soil INSTRUMENTS Bell Lane Uckfield East Sussex t 44 0 1825 765044 e info itmsoil com TN22 1QL United Kingdom f 44 0 1825 744398 w www itmsoil com Soil Instruments Ltd Registered in England Number 07960087 Registered Office 5th Floor 24 Old Bond Street London W1S 4AW User Manual 20
10. d Kingdom f 44 0 1825 744398 w www itmsoll com VIBRATING WIRE INSTRUMENTS CALIBRATION CERTIFICATE Instrument Type Vibrating Wire Pressure Cell Instrument Range 0 00 to 1000 0 kPa G E in KP Period Gauge Factor K 4521 6290000 Linear Gauge Factor G kPa digit 0 4521600 Polynomial Gauge Factor A 0 000001984967000 Polynomial Gauge Factor B 0 4311532000 Polynomial Gauge Factor C 2839 456000 Serial No 025083 Calibration Date 23 11 2006 Ambient Temperature 119C Barometric Pressure 981 mbar Calibration Technician David Manville Calibration Equipment Oil Deadweight Calibrator Serial No 19462 Vibrating Wire Logger Serial No 635 Regression Zero 6400 5 Applied Reading Reading Calculated kPa Period 1000 Linear 0 00 3955 0 6393 0 3 402 100 00 4021 9 6182 0 98 808 200 00 4096 8 5958 0 200 093 300 00 4173 9 5740 0 298 664 400 00 4255 9 5521 0 397 688 500 00 4345 0 5297 0 498 972 600 00 4439 8 5073 0 600 257 700 00 4539 8 4852 0 700 185 800 00 4647 9 4629 0 801 017 900 00 4763 0 4408 0 900 945 1000 00 4885 9 4189 0 999 969 Formulae Linear E G R0 R1 Polynomial ARV Error FS Linear Calculated Error FS Linear Increment Polynomial Polynomial 0 34 0 0 1 967 0 20 0 12 211 0 98 208 0 18 0 01 224 0 200 184 0 02 0 13 218 0 299 237 0 08 0 23 219 0 398 555 0 14 0 10 224 0 499 943 0 01 0 03 224 0 601 132 0 11 0 02 221 0 700 771
11. essure cell piezometer vertically point facing downwards in a water filled container to immerse the filter and leave for at least 24 hours Incline the pressure cell piezometer at approximately 30 from horizontal with the tip pointing upwards Fill dosing syringe with de aired water and attach it to bleed screw A Inject water until it trickles out of bleed point B Turn the pressure cell piezometer vertically point facing upwards and shake vigorously to displace any air which may be trapped near the diaphragm of the piezometer transducer Inject water to displace entrapped air insert and tighten bleed screw B check beforehand that O ring is still fitted to bleed screw Lay the pressure cell piezometer horizontally disconnect dosing syringe and insert and tighten bleed screw A Store the pressure cell piezometer under water to keep the ceramic filter fully saturated until time of installation 2 03 Zero Check and Calibration Calibration values for the pressure cell and piezometer transducers are supplied by the factory The pre set base is the fluid pressure in the oil within the pressure cell The pre set base is affected by ambient temperature and barometric pressure thus this should be borne in mind when checking the base Prior to installation of the cells it is vital to record the Base Reading or site Zero since it will be the value to which all others will be compared Place the cell in an area where a constant temperature exist
12. lem of supporting the weight of the installation pipes does not exist The arrangement for pushing the pressure cell piezometer into position will depend upon the circumstances Two arrangements for pushing the pressure cell piezometer into position in horizontal boreholes are shown in Figures 4 and 5 In Figure 4 the pressure cell piezometer is being installed from a 5 metre diameter bored tunnel into London clay at a depth of 9 3m The borehole was hand augured and had a diameter of 100mm The pressure cell piezometer was pushed into position using an 8 tonne capacity double acting hydraulic jack fixed to an Acrow prop Reaction for the jack was provided by the opposite wall of the tunnel Using this arrangement the one pressure cell was pushed up to 2m beyond the end borehole generating a maximum thrust of 3 5 tonnes In Figure 5 the pressure cell piezometer is being pushed into the side of a sea cliff of glacial till 3 04 Vertical Hole Recoverable installing pipes amp permanent installation To enable recovery of the installing pipes the pressure cell piezometer is supplied with a 500mm long protective pipe with a left handed thread at its upper end A re usable adaptor threaded left hand and right hand this must be ordered separately connects the extension pipe to the installing pipes Installation of the pressure cell piezometer is generally as described in 3 20 After the pressure cell piezometer has been pushed in the installing
13. ng to prevent water coming up inside the installing pipe Bentonite pellets and water can also be put down the inside the first 0 5m of the installing pipe again to seal the pipe Sealing the installation pipe prevents it from acting as a drain and ensures a fast response of the piezometer to changes in the pore water pressure in the soil A mark on the upper end of the first installation pipe should be made to indicate the orientation of the pressure cell It is essential to mark the subsequent installation pipes to ensure the correct orientation of the pressure cell is maintained Lower the pressure cell and first length of installing pipe down the borehole and support it Connect subsequent lengths of installing pipe making sure the orientation is maintained When installing pressure cells to depths greater than about 6m the weight of the installing pipes necessitates the use of a pipe clamp to hold the lower pipes while screwing on the next one An arrangement for lowering the pressure cell and pipes such as an overhead pulley system is also required WARNING Before the pressure cell piezometer is lowered below water in the borehole or is pushed into the ground a zero reading on the pressure cell and piezometer must be taken This reading is necessary since the pressure cell is temperature sensitive and the temperature at the surface may well be different to that in the ground This reading then becomes the zero reading which is used in all su
14. on of Conformity 18 Appendix A Troubleshooting Guide 19 2 User Manual Section 1 Introduction 1 01 Description of Equipment The Push In Pressure Cell consists of a pointed rectangular spade shaped oil filled chamber formed from two sheets of steel welded around the edge The dimensions of the active part of the pressure cell are approximately 100 x 200mm by 6 4mm thick The oil filled cell is connected by a short length of steel tube to a Vibrating Wire Transducer thus forming a sealed hydraulic system The cell is welded to a support plate and connector boss onto which the installation pipes are attached A porous filter disc is incorporated in the support plate and is connected to a second Vibrating Wire Transducer thus providing an integral piezometer The two Vibrating Wire Transducers are mounted in parallel behind the spade cell and are protected within the protective pipe Each transducer is fitted with PVC sheathed screened electrical cable which extends beyond the top of the borehole to enable future termination or extensions 1 02 Applications The Push In Pressure Cell piezometer is suitable for measuring total earth pressures in clay soils up to shear strength of approximately 300 kN m The incorporation of a Vibrating Wire Piezome
15. on of pushing the pressure cell piezometer into the ground initially generates high pressures locally around the cell In a clay soil these excess pressures dissipate rapidly at first but it is usually about 10 days after installation before the cell registers a stable equilibrium value Due to the method of installation this value is likely to be larger than the original in situ pressures in the undisturbed ground It is suggested that where the pressure cell piezometer is pushed into soft and very soft clays the magnitude of the over read is very small and may be ignored However in firm and stiff clays it appears that it over reads by a small but significant amount Based on work by Tedd and Charles 1983 it is suggested that the over read should be taken as half the undrained shear strength of the clay Pressure Changes Pressure changes measured by Push In Pressure Cell piezometers appear to be sensible and agree with other methods of measuring pressure in clay soils Tedd et al 1984 1985 Measured changes of pressure should therefore be regarded as actual changes without any correction being applied 5 02 Pore Pressure Observations from the piezometers generally give reliable and sensible results It can take up to a week before reliable results are obtained 5 03 Data Reduction The mathematical relationship between the frequency of vibration of a tensioned wire and the force applying the tension is an approximate straight line rel
16. oss the two exposed conductors if the cable has not been connected to a terminal cabinet or can be done just as easily across the two conductors if the instrument has been connected to such a terminal or datalogger The resistance across the two conductors should be approximately of the order of 1200 to 1800 The majority of this resistance will come from the transducer say approximately 1300 Before proceeding to Steps 3 and 4 the continuity should be checked between conductors and earthing screen of the electrical cable If continuity exists a damaged cable is confirmed STEP 3 If the resistance across the two conductors is much higher than the values quoted in STEP 1 or is infinite a severed cable must be suspected STEP 4 If the resistance across the two conductors is much lower than the values quoted in STEP 1 say 800 or less it is likely that cable damage has occurred causing a short in the circuit STEP 5 If the resistance is within the values quoted in STEP 1 i e 1200 to 180Q AND no continuity exists between conductor and earth screen and on checking the reading from the transducer it proves to be still unstable or wildly fluctuating it must be assumed that the integrity of the circuit is good A faulty transducer could be suspected if neighbouring construction activities do not account for the anomaly Soil Instruments should be consulted If the point at which the cable is damaged is found the
17. s A good option is to place the cell in a drum full of water However the constant temperature should be as close to the ground temperature as possible since the oil filled cell will be affected by thermal expansion When the temperature gradients that can exist in the cell have been removed 3 or 4 hours perhaps reading on the 2 transducers should be recorded in a Period format The readings should be noted on the calibration sheet supplied by the factory See the Vibrating Wire Readout Logger operating manual for operating details User Manual Section 3 Installation of the Pressure Cell Piezometer 3 01 Drilling the borehole The borehole into which the pressure cell is installed should be at least 100mm diameter but preferably 150mm diameter It should be drilled to within 0 5m to 1 0m of where the cell is to be installed The method of drilling e g shell and auger rotary or hand augering should ensure that the borehole stays open Casing may be required to prevent the borehole collapsing in poor ground 3 02 Vertical Hole Permanent installing pipes amp recoverable cell Having drilled the borehole and prepared the instrument installation can now take place Remove the 500mm long protective pipe and feed the cables through the first length of the installing pipe and screw the pipe onto the double coupling at the pressure cell piezometer A thread sealing compound such as Boss White or PTFE Tape should be put onto the coupli
18. soil INSTRUMENTS Vibrating Wire Push In Pressure Cell Piezometer User Manual eee Man 157 3 0 2 06 08 2018 Phillip Day Andy Small Chris Rasmussen Manual No Revision Date Originator Checked Authorised for Issue User Manual Contents Section 1 1 3 1 01 Description Of Equipment a a EERE KKR KRA RR nnn nnn 3 1 02 Applications ts Dite o eee bela es CS d a 3 Section 2 Preparation of the 4 2 01 Checking for correct Operation u u tee da d pia 4 2 02 De airing the Piezometer iaio live dn a 4 2 03 Zero Check and Calibratio M a 4 Section 3 Installation of the Pressure Cell Piezometer 5 3 01 Brilling the borehole exa a pers 5 3 02 Vertical Hole Permanent installing pipes amp recoverable CEll 5 3 03 Horizontal Hole fasce vee 6 3 04 Vertical Hole Recoverable installing pipes amp permanent installation
19. ter in the instrument enables pore water pressure to be measured and therefore the effective stress can be determined The cells can also be installed permanently and used to monitor changes in earth pressure associated with for example construction of an excavation When installed in vertical boreholes total horizontal stresses are measured by the pressure cell They are often installed in stiff clay behind and in front of retaining walls in soft puddle clay cores of old embankment dams and in glacial till adjacent to sea cliffs The cells have also been installed in horizontally drilled boreholes from tunnels and cliff faces In these situations both horizontal and vertical stresses can be measured by the appropriate orientation of a number of cells The cells may be used as a site investigation tool to measure the in situ stresses in the ground prior to any disturbance In this case the cells need only be left in for a few weeks User Manual Section 2 Preparation of the Equipment 2 01 Checking for correct operation This is achieved by connecting the pressure cell and piezometer to the Vibrating Wire Readout Logger and taking a set of readings in F 1000 Units The readings on the pressure cell should be stable See the Vibrating Wire Readout Logger operating manual operating details 2 02 De airing the Piezometer Refer to Figure 1 Unscrew the double coupling to reveal bleed screw A Remove bleed screws A and B Place the pr
20. ts were kPa we can find out that 1kPa is equal to 0 01019 so we would derive the factor for KGF Cm by multiplying the factor for kPa by 0 01019 Please see conversion factors Figure 7 Calculation using Linear units The following formula is used for readings in Linear units E G RO R1 Where E is the resultant Engineering unit G the linear Gauge factor for the units of calibration from the calibration sheet RO is the Linear base or zero reading R1 is the current Linear reading Again the Linear gauge factor for units other than the units of calibration would need to be calculated using the same principles as stated in the last paragraph of the Period unit section Linear unit calculation using a Polynomial equation Linear units maybe applied to the following polynomial equation for calculation of Engineering units to a higher order of accuracy E AR1 2 BR1 C Where E is the resultant Engineering unit A B and C the Polynomial Gauge factors A B and C from the instrument s calibration sheet Ri is the current Linear reading The value C is an offset value and relates to the atmospheric pressure experienced by the pressure cell at the time of calibration This figure will have changed at the time of installation due to changes in altitude or barometric pressure so C should be re calculated at the installation time as follows ARO 2 BRO Where A and B
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