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Bentonite Handbook: Lubrication for Pipe Jacking

Bentonite Handbook: Lubrication for Pipe Jacking

Steffen Praetorius, Britta Schößer

ISBN: 978-3-433-60652-0 March 2017 228 Pages

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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.

Acknowledgement  VII

Foreword  IX

List of symbols used  XV

I. Greek symbols  XV

II. Latin symbols  XV

1 Basics  1

1.1 Basics and technical implementation of bentonite lubrication systems  1

1.2 Annular gap lubrication in pipe jacking  5

1.3 Preliminary remarks about the ground 6

2 Bentonite and bentonite suspensions   9

2.1 Composition and structure 9

2.2 Hydration behaviour   10

2.3 Card house structure and thixotropy  11

2.4 Yield point, viscosity and gel strength  12

2.5 Stability 17

2.6 Usual types of bentonite   19

3 Additives 21

3.1 Polymers  21

3.2 Types of polymer additives   24

3.3 Overview of polymer additives and their functions   27

4 Correct preparation of bentonite suspensions  29

4.1 Mixing   29

4.2 Mixing equipment 33

4.3 Mixing instructions  34

4.4 Hydration tank 35

5 Properties of the suspension and measurement processes  37

5.1 Viscosity: Marsh funnel   37

5.2 Yield point: ball-harp rheometer  40

5.3 Viscosity and gel strength: Rotational viscometer  42

5.4 Filtrate water and thickness of filter cake: filter press  43

5.5 Density 45

5.6 Water hardness: test strips 46

5.7 pH value  46

5.8 Conductivity 46

5.9 Temperature  47

6 Ground and groundwater 49

6.1 Geology of solid rock 49

6.2 Geology of soils 65

6.3 Stability and stand-up time   85

6.4 Hydrogeology  88

6.5 Influence of various rock properties on the use of bentonite  99

6.6 Contamination in the ground, groundwater or mixing water  100

7 Bentonite suspensions for annular gap lubrication  105

7.1 Size of the annular gap  105

7.2 Vertical position of the pipe string in the driven cavity  107

7.3 Functions of the lubricant in the annular gap 111

7.4 Adaptation of the bentonite suspension to the ground 119

7.5 Rheological parameters of the bentonite suspension 124

7.6 Suspension quantities 132

7.7 Time-dependant loss volumes 147

7.8 Lubrication strategies 148

8 Lubrication technology  155

8.1 Arrangement and spacing of the lubrication points in the pipe string 155

8.2 Number and arrangement of the injection fittings per lubricating point in the pipe cross-section   156

8.3 Non-return valves  157

8.4 Lubrication circuit   158

8.5 Interaction between the support pressure at the face and the annular gap pressure  159

8.6 Bentonite supply in the starting area  160

8.7 Lubricant pressure, lubricant quantity and pressure losses   161

9 Reporting 163

9.1 Which parameters should be documented for bentonite lubrication?  163

9.2 Forms  163

10 Lists of the required injection quantities  167

10.1 Explanation of the lists  167

Literature 197