FS 09. Geotechnical Investigations for Design and Construction of Airfield Pavements

63 Pages·2004·1.05 MB·English

Defence Works
Functional Standards
09
Geotechnical Investigations
for Design and Construction
of Airfield Pavements
Defence Works Services
Ministry of Defence
London: HMSO
© Crown copyright 1994
Applications for reproduction should be made to HMSO
First published 1994
ISBN 011 772813 6
NOTE: This standard reflects the current practices in Ground Investigation and supercedes
Airfield Liaison Memorandum No. 64 (1987) published by Directorate of Civil
Engineering Services, Property Services Agency (DOE). The Standard is intended
for use throughout MOD and shall be used as a guide only.
DEFENCE WORKS FUNCTIONAL STANDARD
GEOTECHNICAL INVESTIGATIONS
FOR DESIGN AND CONSTRUCTION OF
AIRFIELD PAVEMENTS
CONTENTS PAGE No
SECTION ONE - GENERAL
1 Introduction 1
2 Definitions 1
3 Scope 2
4 Responsibilities of the Designer 2
5 Design Principles 3
6 Design Practice 4
SECTION TWO - GENERAL CONSIDERATIONS OF
GEOTECHNICAL INVESTIGATIONS 5
7 Primary Objectives of Site Investigations for New
and Existing Airfield Pavements 5
8 Design Standards 6
9 Extent and Sequence of Geotechnical Investigations 7
9.1 General 7
9.2 Desk Study 7
9.3 Ground Investigations and field testing
for Maintenance and Reconstruction of
Existing Pavements 8
10 Ground Investigation and Field Testing Techniques 11
10.1 General 11
10.2 Drilling, In situ Testing and Sampling 11
10.3 Recommendations for Exploratory Hole Depths
and Spacing 15
10.4 Design Considerations 16
10.5 Remote Methods of Investigation (including Geophysical) 18
11 Design of Instrumentation and Monitoring 19
12 Geotechnical Investigation Reporting Requirements 20
12.1 General 20
12.2 Factual Reporting 20
12.3 Interpretative Reporting 20
13 Soils Classification and Evaluation 21
13.1 General 21
13.2 Soils Classification and Evaluation of Subgrade Strength 22
13.3 General Classification Tests in the Laboratory 23
13.4 Notes on Special Requirements for Testing Contaminated Soils 26
DEFENCE WORKS FUNCTIONAL STANDARD
GEOTECHNICAL INVESTIGATIONS
FOR DESIGN AND CONSTRUCTION OF
AIRFIELD PAVEMENTS
CONTENTS (Continued) PAGE No
SECTION THREE - DESIGN CONSIDERATIONS 27
14 Design Parameters 27
14.1 The Modulus of Subgrade Reaction (k) 27
14.2 The California Bearing Ratio (CBR) 27
14.3 Compaction of Subgrade 28
15 Design Guidance 31
15.1 Subsoil and Subgrade Drainage 31
15.2 Very Weak Subgrade (Except Peat) 32
15.3 Subgrade Improvement 33
15.4 Expansive Soils 33
15.5 Frost Susceptibility 34
15.6 Peat 34
15.7 Spring thaw and permafrost 35
15.8 Construction Practice 35
16 Aggregates for the Construction of Pavements 35
17 References
Tables
1 General Methods of Drilling and Sampling Techniques 12
2 Recommended Sampling Techniques 13
3 Class of Sample Quality 13
4 Recommended Chemical Sample Preservation and Storage Details 15
5 Spacing of Exploratory Holes 16
6 Sampling Frequencies 17
7 Minimum Sample Mass Required for Testing 17
8 Geophysical Methods of Investigation 18
9 Commonly Used Instrumentation 19
10 Recommended Testing 24
11 List of General Soils Testing 25
12 Relative Compaction Requirements for Subgrade 30
13 List of Recommended Aggregate Testing 36
DEFENCE WORKS FUNCTIONAL STANDARD
GEOTECHNICAL INVESTIGATIONS
FOR DESIGN AND CONSTRUCTION OF
AIRFIELD PAVEMENTS
FIGURES
1 Effect of Granular Sub-Base on the Modulus of Subgrade Reaction (k) for Rigid
Pavements
APPENDICES
A Extended Casagrande Soil Classification and CBR/k Relationship
Table A1 - The Extended Casagrande Soil Classification
Table A2 - Extended Soil Classification with Material Characteristics
Figure 2 - California Bearing Ratio versus Modulus of Subgrade Reaction
B Standard Cone Penetrometer Interpretation Charts
C Interpretation of Pavement Visual Survey Data
D CBR versus Soil Suction Curve and Soil Desiccation Potential
DEFENCE WORKS FUNCTIONAL STANDARD
SECTION ONE - GENERAL
1. INTRODUCTION
1.1 The Defence Works functional standard deals with the investigation of sites for
assessing the suitability for the construction of Airfield Pavements and their
associated structures (such as culverts, bridges, concrete trunking boxes,
maintenance areas, hangers and embankments) and of acquiring the geotechnical
and ground contamination characteristics of the site. The objectives of such
investigations are to provide information to ensure an economical design and
construction of the works by reducing to an acceptable level the uncertainties and
risk that the ground poses and ensuring the security of neighbouring land and
property.
1.2 The detailed design of ground investigation is very important for the accurate
identification and evaluation of the site conditions and pavement formations and
cannot be overemphasized.
1.3 This standard does not attempt to cover the wider economic considerations
affecting the selection of the site, neither does it cover the structural design of the
airfield pavement.
2. DEFINITIONS
2.1 Any investigation in advance of construction works, including earthworks shall
involve considering what is a soil and/or rock and their mechanics. Definitions in
terms of soils and their testing are given in BS 5930, BS 1377 and BS 6031.
Engineering geological descriptions of rocks including the recommended testing are
also given in BS 5930. Unless otherwise stated reference shall always be made to
the latest editions.
2.2 The following terms are specific to this document:
2.2.1 Site Investigation: Determination of physical characteristics of sites as they affect
design and construction of building and civil engineering works and stability of
neighbouring structures.
2.2.2 Ground Investigation: Exploration and recording of the location and characteristics
of soil and rock, and groundwater conditions.
2.2.3 Designer - The Designer of the site investigation, may be an engineer with a
consultant or a contractor. The Designer shall fulfil the requirements of the
definition of a Geotechnical Specialist in terms of qualifications and experience
(ICE Site Investigation in Construction).
2.2.4 Geotechnical Specialist - A Chartered Engineer or a Chartered Geologist with a
postgraduate qualification in geotechnical engineering or engineering geology,
equivalent to at least a MSc and with three years post chartered experience in
geotechnics or a Chartered Engineer or Chartered Geologist with at least 5 years
post-chartered experience in geotechnics. Additional specialist advice on ground
contamination should be provided by an environmental scientist, chemist or
environmental engineer with a minimum of five years relevant professional
experience.
3.0 SCOPE
3.1 This standard sets out detailed guidance, formal procedures, technical standards
and gives standard practices (where not covered by other existing standards) for
the assessment, design and construction of Airfield Pavements.
3.2 For the purpose of this standard, ground investigation shall include the following:
a) desk study
b) site reconnaissance
c) geomorphological mapping
d) procurement of ground investigation contract
e) exploratory fieldwork
f) in situ testing and sampling
g) laboratory test scheduling
h) instrumentation and monitoring
i) factual reporting
j) interpretative reporting
3.3 The use of soil and rock as construction materials is treated only briefly; and
reference should be made to BS 6031: Code of Practice for Earthworks.
4. RESPONSIBILITIES OF THE DESIGNER
4.1 Designers shall be responsible for implementing the requirements of this standard
in conjunction with current British Codes, Standards and Practices. The Designer
should ensure that:-
a) an adequate desk study with geotechnical / ground contamination site
inspection is carried out;
b) following the desk study the ground investigation is then planned, designed
and directed;
c) appropriate standards of work are then specified;
d) the work shall be properly supervised to ensure that the technical standards
are met;
e) the work is reported in accordance with technical standards.
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4.2 The Designer shall always consult with the Airfield Property Manager before
starting any works on an existing airfield and before writing any Safety
requirements specific to a particular site. The Designer shall also consider safety
aspects in accordance with the Construction (Design and Management) Regulations
1994, throughout the design process and develop these in the design of the site
investigation. These shall include but not be limited to:
(a) Effect of work on neighbouring land and structures.
(b) Protection of site staff and the public around the site.
(c) Access for materials.
(d) Access and manoeuvring space for plant.
(e) Protection of aircraft and permanent accesses during all stages of the works.
(f) Locations of existing services, including drainage, tunnels, electrical,
communication and signalling equipment.
(g) Temporary works including shoring of trial pits, scaffolding platforms for
boring rigs.
(h) Backfilling of exploratory holes and pits.
(i) Protection of monitoring installations
4.3 The Designer shall consult with all Statutory Authorities with regard to the
determination of the presence or absence of services and any special requirements
of Statutory Authorities (ie: The National Rivers Authority (NRA)).
4.4 Where Made Ground (possibly contaminated) ground is likely to be encountered,
the Designer shall carry out a Risk Assessment and COSHH Assessment in
accordance with the Management of health and safety at work regulations (1992).
Both statements shall be forwarded to the contractor at the tender stage who shall
prepare a separate and detailed COSHH statement for the site work. The Designer
shall provide the contractor with all available information concerning the
contamination of the site and development history of the site.
4.5 The British Drilling Association (BDA) Guidance Notes for the Safe Drilling of
Landfills and Contaminated Land65, DD 175 Code of Practice for the identification
of potentially contaminated land and its investigation 57, CIRIA report "A Guide
to Safe Working Practices for Contaminated Sites", and the ICE Site Investigation
in Construction Volume 455 can be used to assist in the preparation of the above
information.
5.0 DESIGN PRINCIPLES
5.1 All pavements are relatively thin constructions, in terms of civil engineering
construction, in intimate contact with the ground. The importance of the proper
application of soil mechanics principles depends upon the pavement type and their
life expectancy. For thin flexible pavements with a thin granular base the
influence of the soils is very large, whereas for a substantial reinforced concrete
pavement with a thick sub-base it will be much less so.
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