Bentonite Handbook: Lubrication for Pipe Jacking

Description

Pipe jacking is a construction process for the no-dig laying of pipes. Successful pipe jacking demands low skin friction between the ground and the jacked pipe. This is achieved with bentonite lubrication. The bentonite slurry fed into the annular gap fulfils several purposes.

It stabilises the annular gap by supporting the surrounding ground and reduces friction contact between ground and jacked pipe. The Bentonite Handbook deals comprehensibly with the relevant aspects of annular gap lubrication: starting with the ground conditions, which are of decisive importance for lubrication, through the rheological properties of the bentonite slurry to the technical components of lubrication technology and lubrication strategy. The use of standardised measuring apparatus is described as well as mixing equipment and the automatic lubrication system. Overview tables with calculations and suggested values for bentonite consumption quantities depending on the prevailing ground conditions and the pipe jacking parameters complete the recommendations.

Table of Contents

1. Acknowledgement  VII
2. Foreword  IX
3. List of symbols used  XV
   1. Greek symbols  XV
   2. Latin symbols  XV
4. Basics  1
   1. Basics and technical implementation of bentonite lubrication systems  1
   2. Annular gap lubrication in pipe jacking  5
   3. Preliminary remarks about the ground  6
5. Bentonite and bentonite suspensions  9
   1. Composition and structure  9
   2. Hydration behaviour  10
   3. Card house structure and thixotropy  11
   4. Yield point, viscosity and gel strength  12
   5. Stability  17
   6. Usual types of bentonite  19
6. Additives  21
   1. Polymers  21
   2. Types of polymer additives  24
   3. Overview of polymer additives and their functions  27
7. Correct preparation of bentonite suspensions  29
   1. Mixing  29
   2. Mixing equipment  33
   3. Mixing instructions  34
   4. Hydration tank  35
8. Properties of the suspension and measurement processes  37
   1. Viscosity: Marsh funnel  37
   2. Yield point: ball-harp rheometer  40
   3. Viscosity and gel strength: Rotational viscometer  42
   4. Filtrate water and thickness of filter cake: filter press  43
   5. Density  45
   6. Water hardness: test strips  46
   7. pH value  46
   8. Conductivity  46
   9. Temperature  47
9. Ground and groundwater  49
   1. Geology of solid rock  49
   2. Geology of soils  65
   3. Stability and stand-up time  85
   4. Hydrogeology  88
   5. Influence of various rock properties on the use of bentonite  99
   6. Contamination in the ground, groundwater or mixing water  100
10. Bentonite suspensions for annular gap lubrication  105
    1. Size of the annular gap  105
    2. Vertical position of the pipe string in the driven cavity  107
    3. Functions of the lubricant in the annular gap  111
    4. Adaptation of the bentonite suspension to the ground  119
    5. Rheological parameters of the bentonite suspension  124
    6. Suspension quantities  132
    7. Time-dependant loss volumes  147
    8. Lubrication strategies  148
11. Lubrication technology  155
    1. Arrangement and spacing of the lubrication points in the pipe string  155
    2. Number and arrangement of the injection fittings per lubricating point in the pipe cross-section  156
    3. Non-return valves  157
    4. Lubrication circuit  158
    5. Interaction between the support pressure at the face and the annular gap pressure  159
    6. Bentonite supply in the starting area  160
    7. Lubricant pressure, lubricant quantity and pressure losses  161
12. Reporting  163
    1. Which parameters should be documented for bentonite lubrication?  163
    2. Forms  163
13. Lists of the required injection quantities  167
    1. Explanation of the lists  167
14. Literature  197

Author(s) Description

Steffen Praetorius is a graduate geologist and deputy manager of research and development in the Utility Tunnelling department of Herrenknecht AG. In addition to research projects and geotechnical considerations, his duties also include technical and user-specific questions about the use of bentonite in tunnelling.

Dr. Britta Schößer is a researcher and lecturer at the Ruhr University, Bochum at the Chair of Tunnelling and Construction Management. The investigation of bentonite suspensions for construction use in utility construction and tunnelling belong to her specialist areas.