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Geokon 4855 Instruction Manual

Pile tip pressure cell
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Instruction Manual
Model 4855
Pile Tip Pressure Cell
No part of this instruction manual may be reproduced, by any means, without the written consent of Geokon
®
.
The information contained herein is believed to be accurate and reliable. However, Geokon
®
assumes no responsibility for errors,
omissions or misinterpretation. The information herein is subject to change without notification.
Copyright © 2003-2019 by Geokon
®
Doc REV F, 05/1/19

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Summary of Contents for Geokon 4855

  • Page 1 Instruction Manual Model 4855 Pile Tip Pressure Cell No part of this instruction manual may be reproduced, by any means, without the written consent of Geokon ® The information contained herein is believed to be accurate and reliable. However, Geokon ®...
  • Page 3 Geokon or any breach of any warranty by Geokon shall not exceed the purchase price paid by the purchaser to Geokon for the unit or units, or equipment directly affected by such breach. Under no circumstances will Geokon reimburse the claimant for loss incurred in removing and/or reinstalling equipment.

  • Page 5: Table Of Contents

    TABLE of CONTENTS 1. INTRODUCTION ..............................1 1.1 T ............................1 HEORY OF PERATION 1.2 P ..................1 RESSURE ESIGN AND ONSTRUCTION 2. INSTALLATION ..............................3 2.1 P ............................3 RELIMINARY ESTS 2.2 P ........................... 3 RESSURE NSTALLATION 2.3 C ........................
  • Page 6 FIGURES 1 - S ......................1 IGURE HOWING A RESSURE 2 - C ............................4 IGURE ONCRETE 3 - L GK-404 ........................6 IGURE ONNECTOR TO 4 - L – R ....................... 7 IGURE EADINGS EADINGS TABLES 1 - S ...........................11 ABLE AMPLE...

  • Page 7: Introduction

    1. INTRODUCTION 1.1 Theory of Operation The ability of cast-in-place piles to support a load relies on friction along the pile and on end bearing. The load distribution along the pile can be measured by embedding strain gauges at different depths along the pile and by comparing the measured strains at different depths with the strains at the top of the pile, very close to the applied load, which are assumed to be equivalent to 100% of the applied load.
  • Page 8 (An alternative method, using a pinch tube and remote crimping device, is also available). The vibrating wire sensors are standard Geokon Model 4500H transducers inside all-welded housings. The sensors are hermetically sealed and are connected via waterproof connectors to an electrical cable leading to the surface.

  • Page 9: Installation

    2. INSTALLATION 2.1 Preliminary Tests It is always wise, before installation commences, to check the cells for proper functioning. Each cell is supplied with a calibration sheet, which shows the relationship between readout digits and pressure and shows the initial no load zero reading. The transducer’s electrical leads (usually the red and black leads) are connected to a readout box and the zero readings given on the sheet is now compared to the current zero readings.

  • Page 10: Figure 2 - Concrete Cone

    A concrete cone is constructed and attached to the under-surface of the load cell in the following manner: The load cell is manufactured at Geokon so that it has threaded lugs welded to the underside. Pieces of rebar, supplied with the load cell, are threaded at one end and are threaded into the lugs so that they form two circles of rebars;...

  • Page 11: Cable Installation And Splicing

    Splice kits recommended by Geokon incorporate casts which are placed 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 itself in strength and electrical properties. Contact Geokon for splicing materials and additional cable splicing instructions.

  • Page 12: Taking Readings

    20 hours on two AA batteries. It is designed for the readout of all Geokon vibrating wire gauges and transducers; and is capable of displaying the reading in either digits, frequency (Hz), period (µs), or microstrain (µε). The GK-404 also displays the temperature of the load cell (embedded thermistor) with a resolution of 0.1 °C.

  • Page 13: Gk-405 Readout Box

    Connecting Sensors with Bare Leads: Attach the GK-403-2 flying leads to the bare leads of a Geokon vibrating wire sensor by connecting each of the clips on the leads to the matching colors of the sensor conductors, with blue representing the shield (bare).

  • Page 14: Gk-403 Readout Box (Obsolete Model)

    Connecting Sensors with Bare Leads: Attach the GK-403-2 flying leads to the bare leads of a Geokon vibrating wire sensor by connecting each of the clips on the leads to the matching colors of the sensor conductors, with blue representing the shield (bare).

  • Page 15: Data Reduction

    4. DATA REDUCTION 4.1 Pressure Calculation The basic units utilized by Geokon, and displayed on the readout box Channel B, for measurement and reduction of data from a Pile Tip Pressure Cell are "digits". Calculation of digits is based on the following equation: Digits = �...

  • Page 16: Troubleshooting

    Gauges should not be opened in the field. Should difficulties arise, consult the following list of problems and possible solutions. Return any faulty gauges to the factory. For additional troubleshooting and support contact Geokon. Symptom: Pressure Cell Readings are Unstable ...

  • Page 17: Table 1 - Sample Resistance

    Vibrating Wire Sensor Lead Grid - SAMPLE VALUES Black White Green Shield infinite infinite infinite ≅180Ω Black infinite infinite infinite ≅180Ω 3000Ω at White infinite infinite infinite 25°C 3000Ω at Green infinite infinite infinite 25°C Shield infinite infinite infinite infinite Table 1 - Sample Resistance Vibrating Wire Sensor Lead Grid - SENSOR NAME/## : Black...

  • Page 18: Appendix A. Specifications

    APPENDIX A. SPECIFICATIONS A.1 Pressure Cells Model: 4855 2 MPa (300 psi), 3. MPa (450 psi), 5 MPa (750 psi), Ranges: 7.5 MPa (1100 psi), 10 MPa (1500 psi), 20 MPa (3000 psi) Sensitivity: 0.025% FSR Accuracy: 0.10% FSR 0.25% FSR (standard) Linearity: 0.1% FSR (optional)

  • Page 19: Appendix B. Thermistor Temperature Derivation

    APPENDIX B. THERMISTOR TEMPERATURE DERIVATION Thermistor Type: YSI 44005, Dale #1C3001-B3, Alpha #13A3001-B3 Resistance to Temperature Equation: A+B ( LnR ) +C(LnR) -273.15 °C Equation 4 - Resistance to Temperature Where; T = Temperature in °C. LnR = Natural Log of Thermistor Resistance. A = 1.4051 ×...

  • Page 20: Appendix C. Attaching The Pressure Cell To The Rebar Cage

    APPENDIX C. ATTACHING THE PRESSURE CELL TO THE REBAR CAGE The eyebolts are threaded into the three lugs welded to the top plate. The three hooks and chains supplied with the cell are then hooked to the eyebolts and used to lift the cell and position it close to the bottom of the rebar cage, (within two meters).

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