Related Manuals for Geokon 4800 Series
Summary of Contents for Geokon 4800 Series
- Page 1 Model 4800 Series VW Earth Pressure Cells Instruction Manual ©2021, GEOKON. All rights reserved. Document Revision: Z | Release date: 06/23/21...
- Page 3 WARRANTY STATEMENT warrants its products to be free of defects in materials and workmanship, GEOKON under normal use and service for a period of 13 months from date of purchase. If the unit should malfunction, it must be returned to the factory for evaluation, freight prepaid.
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Page 5: Table Of Contents
TABLE OF CONTENTS 1. INTRODUCTION ............................1.1 THEORY OF OPERATION ....................... 1.2 EARTH PRESSURE CELL DESIGN ..................1.3 EARTH PRESSURE CELL CONSTRUCTION ..............1.3.1 MODEL 4800 EARTH PRESSURE CELLS ................. 1.3.2 MODEL 4810 CONTACT ("FAT BACK") PRESSURE CELL ..........1.3.3 MODEL 4815 HYDRAULIC LOAD CELL ................... - Page 6 A.1 EARTH PRESSURE CELLS ....................... A.2 STANDARD TEMPERATURE THERMISTOR ............. APPENDIX B. THERMISTOR TEMPERATURE DERIVATION ....... APPENDIX C. TEMPERATURE EFFECT ON EARTH PRESSURE AND CONCRETE STRESS CELLS ............C.1 FORMULAS ............................C.2 EXAMPLES ............................. APPENDIX D. IMPROVING CALCULATED PRESSURE ACCURACY...
- Page 7 FIGURES FIGURE 1: STRESS REDISTRIBUTION, WEAK SOIL WITH STIFF CELL ......1 FIGURE 2: STRESS REDISTRIBUTION, STRONG SOIL WITH STIFF CELL ......2 FIGURE 3: STRESS REDISTRIBUTION, STIFF SOIL WITH WEAK CELL ......2 FIGURE 4: MODEL 4800 RECTANGULAR EARTH PRESSURE CELL ......3 FIGURE 5: MODEL 4800 CIRCULAR EARTH PRESSURE CELL ........3 FIGURE 6: MODEL 4810 CONTACT PRESSURE CELL .............4 FIGURE 7: MODEL 4815 HYDRAULIC LOAD CELL ............4...
- Page 8 TABLES TABLE 1: RATIOS FOR TWO GROUT MIXES..............8 TABLE 2: 4830 WIRING CHART..................13 TABLE 3: ENGINEERING UNITS MULTIPLICATION FACTORS........17 TABLE 4: EARTH PRESSURE CELL SPECIFICATIONS...........21 TABLE 5: 3KΩ THERMISTOR RESISTANCE ..............22 TABLE 6: TYPICAL VALUES OF VARIOUS CELL PARAMETERS ........25...
- Page 9 EQUATIONS EQUATION 1: TERZAGHI’S PRINCIPLE OF EFFECTIVE STRESS........1 EQUATION 2: DIGITS CALCULATION ................17 EQUATION 3: CONVERT DIGITS TO PRESSURE ............17 EQUATION 4: TEMPERATURE CORRECTION ..............18 EQUATION 5: 3KΩ THERMISTOR RESISTANCE............. 22 EQUATION 6: EXPANSION OF LIQUID FOR A 1° C TEMPERATURE RISE ....23 EQUATION 7: COMPRESSION OF LIQUID..............
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Page 11: Introduction
"sheltered" by the cell and therefore does not experience the full soil pressure. This can be represented schematically as shown in Figure 1. Mean Stress Cell FIGURE 1: Stress Redistribution, Weak Soil with Stiff Cell MODEL 4800 SERIES VW EARTH PRESSURE CELLS | INTRODUCTION | 1... -
Page 12: Earth Pressure Cell Design
In general, Earth Pressure Cells use an all welded construction; this GEOKON means the space confining the oil is entirely metal and does not require any o- 2 | INTRODUCTION | GEOKON... -
Page 13: Earth Pressure Cell Construction
FIGURE 4: Model 4800 Rectangular Earth Pressure Cell Pressure Cell Transducer Housing Instrument Cable (4 conductor, 22 AWG) 9" 230 mm Top View Side View FIGURE 5: Model 4800 Circular Earth Pressure Cell MODEL 4800 SERIES VW EARTH PRESSURE CELLS | INTRODUCTION | 3... -
Page 14: Model 4810 Contact ("Fat Back") Pressure Cell
Model 4815 Hydraulic Load Cell has been used for the measurement of loads in piles and of concentrated loads on tunnel linings. The pressure transducer housing is connected directly and perpendicular to the thick back plate. FIGURE 7: Model 4815 Hydraulic Load Cell 4 | INTRODUCTION | GEOKON... -
Page 15: Model 4820 Earth Pressure "Jackout" Cell
A thread is provided on the end of the cell to allow for installation using lengths of pipe or drill rods. FIGURE 9: Model 4830 Push-In Pressure Cell MODEL 4800 SERIES VW EARTH PRESSURE CELLS | INTRODUCTION | 5... -
Page 16: Installation
In such situations, the internal soil stresses go around the cell instead of through it. The cell will then register only a very low pressure, which does not change much as the loads increase. This situation occurs frequently. 6 | INSTALLATION | GEOKON... -
Page 17: Figure 10: Model 4800 Earth Pressure Cell Installation
In earth embankments, it is convenient to install in trenches. By doing so, adequate MODEL 4800 SERIES VW EARTH PRESSURE CELLS | INSTALLATION | 7... -
Page 18: Installation Of Model 4810 Contact ("Fat Back") Pressure Cell
Protect the cable from damage during concrete placement and vibration by tying it to adjacent rebar. See Figure 11. 8 | INSTALLATION | GEOKON... -
Page 19: Figure 11: Attachment Of Model 4810 To Concrete Form
See Figure 12 below. Pipe Straps & Conduit Concrete Nails (4 places) Zone with large aggregate removed Mortar Pad Side View Front View FIGURE 12: Model 4810 Contact Pressure Cell Installation MODEL 4800 SERIES VW EARTH PRESSURE CELLS | INSTALLATION | 9... -
Page 20: Installation Of Model 4815 Hydraulic Load Cell
The reaction plate is attached to the other side of the double-acting hydraulic jack. The jack is attached firmly to the rebar cable and arranged so that the plates are 10 | INSTALLATION | GEOKON... -
Page 21: Installation Of Cells To Measure Earth Pressure At The Base Of Footings, Floor Slabs, Pavements, Etc
The cell registers only a very low pressure, which does not change as the loads increase. MODEL 4800 SERIES VW EARTH PRESSURE CELLS | INSTALLATION | 11... -
Page 22: Installation Of Push-In Pressure Cells To Measure Lateral Earth Pressures
To prevent this, readings should be taken as the sensor is pushed. When the indicated pressure approaches 150% of full scale the pushing operation should be terminated until the sensor output comes back within its calibrated range. 12 | INSTALLATION | GEOKON... -
Page 23: Cable Installation And Splicing
GEOKON around the splice and are then filled with epoxy to waterproof the connections. When properly made, this type of splice is equal or superior to the cable in MODEL 4800 SERIES VW EARTH PRESSURE CELLS | INSTALLATION | 13... -
Page 24: Electrical Noise
Take the initial readings while the cell is in position, prior to covering it with fill and pouring the concrete. Again, it is imperative that initial readings at zero load are taken! 14 | INSTALLATION | GEOKON... -
Page 25: Taking Readings
20 hours continuously on two AA batteries. It is designed for the readout of all vibrating wire instruments, and is GEOKON capable of displaying the reading in digits, frequency (Hz), period (µs), or microstrain (µε). The GK-404 also displays the temperature of the transducer (embedded thermistor) with a resolution of 0.1 °C. -
Page 26: Connecting Sensors With 10-Pin Bulkhead Connectors Attached
48.5Ω per km (14.7Ω per 1000') at 20 °C. Multiply these factors by two to account for both directions. Look up the temperature for the measured resistance in Appendix B. 16 | TAKING READINGS | GEOKON... -
Page 27: Data Reduction
DATA REDUCTION 4.1 PRESSURE CALCULATION The digits displayed by the Models GK-404, GK-405, and GK-406 GEOKON readouts on channel B are based on the equation: 3 – ---------------- - digits or digits ----------- - Period 1000 EQUATION 2: Digits Calculation Note that in the above equation, the period is in seconds;... -
Page 28: Temperature Correction
If a correction for these fluctuations is required, then it is necessary to record the initial barometric pressure (S ) and the barometric pressure at the time of each reading (S ) and subtract the change (S ) from the calculated pressure reading. 18 | DATA REDUCTION | GEOKON... -
Page 29: Figure 19: Sample Model 4800 Calibration Sheet
FIGURE 19: Sample Model 4800 Calibration Sheet MODEL 4800 VW EARTH PRESSURE CELLS | DATA REDUCTION | 19... -
Page 30: Troubleshooting
Refer to the expected resistance for the various wire combinations below. Vibrating Wire Sensor Lead Resistance Levels 180Ω Red/Black Green/White 3000 at 25 °C Any other wire combination will result in a measurement of infinite resistance. 20 | TROUBLESHOOTING | GEOKON... -
Page 31: Appendix A. Specifications
Section 1.1. Consult the factory for other sizes available. Consult the factory for alternate cable types. A.2 STANDARD TEMPERATURE THERMISTOR Range: -80 to +150° C Accuracy: ±0.5° C MODEL 4800 SERIES VW EARTH PRESSURE CELLS | SPECIFICATIONS | 21... -
Page 32: Appendix B. Thermistor Temperature Derivation
166.7 58.3 21.89K 2872 582.6 162.0 56.8 20.70K 2750 562.8 157.6 55.6 19.58K 2633 543.7 153.2 18.52K 2523 525.4 149.0 17.53K 2417 507.8 145.0 16.60K 2317 490.9 141.1 TABLE 5: 3KΩ Thermistor Resistance 22 | THERMISTOR TEMPERATURE DERIVATION | GEOKON... -
Page 33: Appendix C. Temperature Effect On Earth Pressure And Concrete Stress Cells
(E) and Poisson’s ratio (), is given by: At the center of the cell: 2PR 1 v – ------------------------------ EQUATION 9: Deformation at the Center MODEL 4800 SERIES VW EARTH PRESSURE CELLS | TEMPERATURE EFFECT ON EARTH PRESSURE AND CONCRETE STRESS CELLS | 23... -
Page 34: Equation 10: Deformation At The Edge
P = 1.5 EKD/R psi / °C EQUATION 14: Total Embedment And for contact pressure cells: P = 3 EKD/R psi / °C EQUATION 15: Total Embedment for Contact Pressure Cells 24 | TEMPERATURE EFFECT ON EARTH PRESSURE AND CONCRETE STRESS CELLS | GEOKON... -
Page 35: Examples
For the same cell, filled with mercury instead of oil: Concrete: P = 5.8 psi / Completely rigid medium: P = 650 psi / MODEL 4800 SERIES VW EARTH PRESSURE CELLS | TEMPERATURE EFFECT ON EARTH PRESSURE AND CONCRETE STRESS CELLS | 25... - Page 36 [4] Fujiyasu, Y. and Orihara, K. “Elastic Modulus of Weathered Rock.” Proc. of the 5 Intl. Symp. on Field Measurements in Geomechanics - Singapore 1999. p 183. 26 | TEMPERATURE EFFECT ON EARTH PRESSURE AND CONCRETE STRESS CELLS | GEOKON...
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Page 37: Appendix D. Improving Calculated Pressure Accuracy
It should be noted that where changes of earth pressures are being monitored it makes little difference whether the linear coefficient or the polynomial expression is used. MODEL 4800 SERIES VW EARTH PRESSURE CELLS | IMPROVING CALCULATED PRESSURE ACCURACY | 27... - Page 40 GEOKON Phone: +1 (603) 448-1562 GEOKON is an ISO 9001:2015 48 Spencer Street Email: info@geokon.com Lebanon, New Hampshire Website: www.geokon.com registered company 03766, USA...