Instruction Manual Model 1280 (Model A6) Borehole Extensometer No part of this instruction manual may be reproduced, by any means, without the written consent of Geokon, Inc. The information contained herein is believed to be accurate and reliable. However, Geokon, Inc. assumes no responsibility for errors, omissions or misinterpretation. The information herein is subject to change without notification. Copyright © 2002, 2006 by Geokon, Inc.
Warranty Statement Geokon, Inc. warrants its products to be free of defects in materials and workmanship, 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. Upon examination by Geokon, if the unit is found to be defective, it will be repaired or replaced at no charge.
TABLE of CONTENTS 1. INTRODUCTION ..........................................................................................................................................................1 2. PRELIMINARY REQUIREMENTS ..........................................................................................................................1 3. INSTALLATION..........................................................................................................................................................
1 1. INTRODUCTION The Model A6 Multiple Position Borehole Extensometer, (MPBX), is made up of three or four basic components: • Borehole anchors, these may be either groutable or hydraulic types. The groutable type is usually recommended for downward directed boreholes or for holes that must remain sealed. Special equipment will be required for grouting boreholes directed upwards. Hydraulic anchors can be used anywhere and are particularly suited for use in upward directed boreholes.
2 2.4 List of Installation Tools Required Note: Installation Tool kits may be purchased as an accessory. They may include the following: 1. Two pair of Vise Grips 2. Adjustable wrenches 3. Screw Drivers 4. Allen Wrenches 5. Hacksaw 6. Files 7. Tape measure 8. Marking Pens 9. Loctite adhesive 10. PVC Cement 11. PVC Primer 12. Hydraulic hand-pump with pressure gage and fittings (Hydraulic Anchors). 13. Portland cement (N0 2) (Groutable Anchors). 14. Quick Setting Cement 15.
3 3. INSTALLATION 3.1 Standard Groutable System with Manual Readout – Downward Directed Boreholes. A typical system is shown in figure 1 Figure 1 3.1.1 Normally, the MPBX is shipped pre-assembled and coiled for shipment. Care should be taken when removing the tape holding the coils. Release one coil at a time and keep a tight grip on the rest of the coils so that they cannot suddenly break free and uncoil violently. Do not cut the tapes bundling the rod/tubes together.
4 3.2 Standard Groutable System with Manual Readout – Upward Directed Boreholes Upward directed boreholes require special grouting techniques. 3.2.1 Normally, the MPBX is shipped complete and pre-assembled and coiled for shipment. Care should be taken when removing the tape holding the coils. Release one coil at a time and keep a tight grip on the rest of the coils so that they cannot suddenly break free and uncoil violently. Do not cut the tapes bundling the rod/tubes together.
5 3.2.7 After the first-stage grout plug has set up, reconnect the grout pump and pump grout until grout is seen exiting the vent tube. (Excessive grout pressures should be avoided since there is a danger of blowing out the plug). When grout is seen issuing from the vent line stop pumping, close the Gate Valve, and disconnect the pump. (In fractured ground there may be some leakage into the fractures causing the top anchor to become un-grouted.
6 4. ADJUSTING ANCHOR DEPTHS Occasionally, unforeseen site conditions may require the anchor depths to be adjusted. This will require the rods and tubes to be either lengthened or shortened. 4.1 Shortening the rods and tubes – groutable and hydraulic anchors Figure 3 4.2 4.1.1 With the MPBX uncoiled on a flat surface, measure the amount to be shortened, from the hose barb on the anchor along the ½ inch O.D. poly tubing then mark the tubing. Next, with a sharp knife, cut only the tubing at this mark.
7 4.2.3 Connect the fiberglass extension rod to the threaded end of the fiberglass rod at the MPBX head end. Use Locktite on the threads. Push the extension rod into the MPBX head until the tip is positioned at the same depth as before. Slide new ferrules and nut onto the fiberglass rod and then tighten the Swagelok fitting on the anchor so that it grips the rod. 4.2.
8 Connectors. The extension rods are designed to hold the ends of the fiberglass rods in their correct positions relative to the head of the MPBX while the anchors and rods are being installed inside the borehole. Without them the friction and pull of the anchors during installation could move the rod tips by an unacceptable amount. 5.2 5.1.3 After the installations have been made as per the instructions of Section 3, the extension rods and Temporary Swagelok Connectors are removed.
9 5.2.3 After uncoiling the fiberglass rods and poly tubing, the poly tubing, (if not already connected), is connected to the Tube Mount with Hose Barbs after a specified amount of the uncoiled tubing has been removed. The amount to be removed is such that when the installation is completed the tip of the fiberglass rod will be in the correct position relative to the Reference Surface. Numbers stamped on the Tube Mount ensure that the anchors are connected in the proper sequence. 5.2.
10 Manual readings are best taken using a dial indicator, although, depth micrometers have also been used. To take manual readings simply poke the stem of the indicator through the holes in the Cap on the MPBX Head assembly until the tip bears against the underlying Swagelok Cap. With the collar of the dial indicator held flush against the MPBX Cap or the Reference Surface take a reading on the indicator.
11 7.1.1 The first task is to calculate the measured displacements between the head and each anchor. This can easily be done for each anchor, by subtracting the initial reading, R0 from each of the subsequent readings. When this is done we have a table of figures as shown in Table2. 12/01/00 Anchor 3 (Depth 20 mtrs) millimeters 0.00 Anchor 2 (Depth 10 mtrs) millimeters 0.00 Anchor 1 (Depth 3 mtrs) millimeters 0.00 12/02/00 0.82 0.81 0.76 12/03/00 0.92 0.91 0.86 12/05/00 1.02 0.97 0.
12 Table 3. Movement of the Instrument Head and Anchors Relative to Anchor 3 in Stable Ground 7.1.3 The data shown in Table 3 could be plotted and shown in a graph similar to the one shown in Figure 6. M ovem ent of the Ins tru ment He ad a nd Anchors Re lati ve t o Stable G round 6.0 Instru m en t H ea d A nch or # 1 A n ch or #2 Me asured D ispla cem ent (m illi mete rs) 5.0 4.0 3.0 Bla sting in A rea 2.0 Initia l R ea ding (R 0 ) Heav y R ain 1.0 0.
13 M o v e m e n ts O c c u rrin g in E a c h In te r- A n ch o r Z o n e 2 .5 H ea d to A nc ho r # 1 A nc ho r # 1 to A nc ho r # 2 A nc h or # 2 to A nc h or # 3 M e as ure d Disp lac em ent (m illim eters ) 2 .0 1 .5 1 .0 0 .5 0 .0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 D e ce m b er 2 00 0 Figure 7 Movements Occurring in Each Inter-Anchor Zone 7.
14 9 Is there a source of electrical noise nearby? Most probable sources of electrical noise are motors, generators, transformers, arc welders and radio transmission towers. Make sure the shield drain wire is connected to ground whether using a portable readout or datalogger. If using the GK-401 Readout connect the clip with the green boot to the bare shield drain wire of the pressure cell cable. If using the GK-403 connect the clip with the blue boot to the shield drain wire.
15 Internal Wiring Red Black Red Black Red Black N/C N/C N/C Geokon Cable #04-375V9 (Violet) Red Black of Red White Black of White Green Black of Green Blue Black of Blue Shields (5) Function / Description Gage 1+ Gage 1Gage 2+ Gage 2Gage 3+ Gage 3Thermistor Thermistor Ground Four Transducers Internal Wiring Red Black Red Black Red Black Red Black N/C N/C N/C Five Transducers Geokon Cable #05-375V12 (Tan) Red Black of Red White Black of White Green Black of Green Blue Black of Blue Yellow Black of Yel
16 Internal Wiring Red Black Red Black Red Black Red Black Red Black Red Black N/C Geokon Cable #06-500V7 (Orange) Red Black of Red White Black of White Green Black of Green Blue Black of Blue Yellow Black of Yellow Blue Black of Blue Shields (7) Function / Description Gage 1+ Gage 1Gage 2+ Gage 2Gage 3+ Gage 3Gage 4+ Gage 4Gage 5+ Gage 5Thermistor Thermistor Ground Seven Transducers Internal Wiring Red Black Red Black Red Black Red Black Red Black Red Black Red Black N/C N/C N/C Geokon Cable #012-625V
17 Appendix 2. Using a Pull-in Anchor in Deep Boreholes For deep boreholes oriented horizontally, upwards, or inclined downwards at a large angle to the vertical it may not be possible, due to the flexibility of the extensometer assembly, and friction against the walls of the borehole, to push the assembly all the way into the borehole. To overcome this problem a pull-in anchor should be used. This pull-in anchor comprises a Bladder type Hydraulic Anchor of the same type as the other anchors.
