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Geokon 4800 Series Instruction Manual

Vw earth pressure cells

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Instruction manual (42 pages)

Table Of Contents

Table of Contents

Table of Contents
Introduction
Theory of Operation
Figure 1: Stress Redistribution, Weak Soil with Stiff Cell
Equation 1: Terzaghi's Principle of Effective Stress
Earth Pressure Cell Design
Figure 2: Stress Redistribution, Strong Soil with Stiff Cell
Figure 3: Stress Redistribution, Stiff Soil with Weak Cell
Earth Pressure Cell Construction
Model 4800 Earth Pressure Cells
Figure 4: Model 4800 Rectangular Earth Pressure Cell
Figure 5: Model 4800 Circular Earth Pressure Cell
Model 4810 Contact ("Fat Back") Pressure Cell
Model 4815 Hydraulic Load Cell
Figure 6: Model 4810 Contact Pressure Cell
Figure 7: Model 4815 Hydraulic Load Cell
Model 4820 Earth Pressure "Jackout" Cell
Model 4830 Push-In Pressure Cell
Figure 8: Model 4820 Jackout Load Cell
Figure 9: Model 4830 Push-In Pressure Cell
Installation
Preliminary Tests
Pressure Cell Installation
Inside Fills and Embankments
Figure 10: Model 4800 Earth Pressure Cell Installation
Installation of Model 4810 Contact ("Fat Back") Pressure Cell
Table 1: Ratios for Two Grout Mixes
Figure 11: Attachment of Model 4810 to Concrete Form
Figure 12: Model 4810 Contact Pressure Cell Installation
Installation of Model 4815 Hydraulic Load Cell
Installation of Model 4820 Jackout Pressure Cell in Slurry Trenches
Figure 13: Model 4815 Hydraulic Load Cell Measuring Loads
Installation of Cells to Measure Earth Pressure at the Base of Footings, Floor Slabs, Pavements, Etc
Figure 14: Model 4820 Jackout Pressure Cell Installation
Installation of Push-In Pressure Cells to Measure Lateral Earth Pressures
Figure 15: Model 4800-1-1P Earth Pressure Cell Installation
Cable Installation and Splicing
Table 2: 4830 Wiring Chart
Electrical Noise
Initial Readings
Taking Readings
Operating the Gk-404
Gk-405 Vibrating Wire Readout
Figure 16: Gk-404 Readout
Figure 17: Lemo Connector to Gk-404
Figure 18: Gk-405 Readout
Connecting Sensors with 10-Pin Bulkhead Connectors Attached
Connecting Sensors with Bare Leads
Operating the Gk-405
Measuring Temperatures
Data Reduction
Pressure Calculation
Table 3: Engineering Units Multiplication Factors
Equation 2: Digits Calculation
Equation 3: Convert Digits to Pressure
Temperature Correction
Barometric Correction
Equation 4: Temperature Correction
Figure 19: Sample Model 4800 Calibration Sheet
Troubleshooting
Appendix A. Specifications
Earth Pressure Cells
Standard Temperature Thermistor
Table 4: Earth Pressure Cell Specifications
Appendix B. Thermistor Temperature Derivation
Table 5: 3Kω Thermistor Resistance
Equation 5: 3Kω Thermistor Resistance
Appendix C. Temperature Effect on Earth Pressure and Concrete Stress Cells
Formulas
Figure 20: Radius (R) and Thickness (D)
Equation 6: Expansion of Liquid for a 1° C Temperature Rise
Equation 7: Compression of Liquid
Equation 8: Expansion of Liquid
Equation 9: Deformation at the Center
Equation 10: Deformation at the Edge
Equation 11: Difference in Deformation
Equation 12: Average Total Expansion of the Cell
Equation 13: Combined Equations
Equation 14: Total Embedment
Equation 15: Total Embedment for Contact Pressure Cells
Examples
Table 6: Typical Values of Various Cell Parameters
Appendix D. Improving Calculated Pressure Accuracy
Equation 16: Pressure Calculation with Second Order Polynomial
Equation 17: "Linearity (%F.s.)" on Calibration Sheet
Equation 18: Calculating C Using the Zero Pressure Reading

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Model 4800 Series

VW Earth Pressure Cells

Instruction Manual

Document Revision: Z | Release date: 06/23/21

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Geokon 4800 Series Instruction Manual

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