Use and influence of bentonite in bored pile construction
Series/doc. No
Report
Report PG 3
Year
1977
Abstract
The Report explains what bentonite is, how it works, and indicates how construction techniques could, in practice, have significant influence over the final behaviour of a load bearing unit. The introduction of the Report also deals with a variety of subjects; the extraction of bentonite from natural earth deposits, its structure, the stabilising action of the slurry, the effects of suspension contamination, filter cake formation, the displacement of suspension from a borehole by concrete, the technique of placing concrete by tremie, the selection of appropriate concrete mixes for this type of work, and the effects of bentonite on the bond between steel and concrete.
ISBN
9780860170310
Subject(s)
Civil engineering and public utilities
Earthworks/foundations/piling/retaining walls
Bearing piles
Bored piles
Supplement
Civil & Structural. To subscribe to The Construction Information Service please telephone Customer Care on +44 1344 328300
Publisher History
CIRIA was formerly known as the Construction Industry Research and Information Association. They are a member-based research and information organisation who publish reports and technical papers covering building and civil engineering as well as transport and utilities infrastructure.
Table Of Contents
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List of illustrations
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7
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List of tables
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8
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Summary
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9
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1 Introduction
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10
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2 Bentonite: its use and behaviour in the construction of bored piles
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13
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2.1 Bentonite material
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13
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2.2 Bentonite suspension
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13
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2.3 Specification for bentonite material
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15
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2.4 Extraction and processing of bentonite
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15
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3 The stabilizing action of bentonite suspension in a borehole
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16
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3.1 Caving of an open unsupported borehole
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16
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3.2 The stabilizing action of bentonite
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16
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3.3 Filter cake formation
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17
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3.4 Effect of suspension composition on filter cake formation
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19
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3.5 The capacity of bentonite suspension to keep detritus in suspension
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20
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4 Displacement of bentonite suspension by concrete
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21
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4.1 Pile formation
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21
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4.2 Displacement of bentonite suspension from the face of the borehole
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21
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4.3 Displacement of bentonite suspension and detritus from the base of the pile bore
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24
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4.4 Displacement of bentonite suspension from reinforcing bars
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25
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4.5 Specification for bentonite suspension
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27
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4.6 Concrete mix design
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29
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4.7 Concreting (tremie operation)
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31
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5 Laboratory tests on the influence of bentonite on skin friction
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33
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5.1 The contribution of various researchers
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33
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5.2 Summary
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35
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6 Effect of bentonite on ultimate shaft friction
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37
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6.1 Factors affecting the shaft friction of piles
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37
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6.2 Analysis of the results of pile tests
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39
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6.3 Results of pile load tests
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41
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7 Effect of bentonite on base resistance
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60
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7.1 The displacement of bentonite suspension for a pile base
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60
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7.2 Case histories
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60
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7.3 Summary
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65
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8 Analysis of other pile load tests
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67
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8.1 Results of tests subjected to further analysis
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67
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8.2 Results of tests not subjected to further analysis
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68
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8.3 Summary
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68
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9 Contract work carried out in the construction of piles and diaphragm wall elements using bentonite suspension
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69
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9.1 Record of work carried out
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69
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9.2 Views expressed on the process of forming piles under bentonite
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70
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10 Conclusions and recommendations
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71
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Acknowledgements
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72
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References
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73
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Appendix 1
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78
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