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Trang 2Handbook of Geotechnical Investigation and Design Tables
Trang 3AY?
ce oY BALKEMA - Proceedings and Monographs in Engineering, Water and Earth Sciences
Trang 4Handbook of Geotechnical Investigation and Design Tables VIETCONS Burt G Look Consulting Geotechnical Engineer
LONDON / LEIDEN / NEW YORK J PHILADELPHIA / SINGAPORE Trung tâm đào tao xây dung VIETCONS
Trang 5Taylor & Francis is an imprint of the Taylor & Francis Group, an informa business © 2007 Taylor & Francis Group, London, UK
This edition published in the Taylor & Francis e-Library, 2007
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All rights reserved No part of this publication or the information contained herein ‘may be reproduced, stored in a retrieval system, or transmitted in any form or by any ‘means, electronic, mechanical, by photocopying, recording or otherwise, without ‘written prior permission from the publishers
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Published by: Taylor & Francis/Balkema
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Library of Congress Cataloging-in-Publication Data
Look, Burt Handbook of geotechnical investigation and design tables / Burt G Look p.cm
Trang 7wi Table of Contents 29 2.10 2.11 2.12 2.13 214 245 216 247 2.18 Gradings Colour Soil plasticity Atterberg limits Structure
Consistency of cohesive soils Consistency of non cohesive soils Moisture content Origin Classification of residual soils by its primary mode of occurrence Rock classification Bl 32 3.3 34 3S 3.6 37 38 3.9 3.10 31 3.12 343 344 35 Rock description Field rock core log Drilling information Rock weathering Colour Rock structure Rock quality designation Rock strength Rock hardness
Discontinuity scale effects Rock defects spacing Rock defects description Rock defect symbols
Sedimentary and pyroclastic rock types ‘Metamorphic and igneous rock types Field sampling and testing 41 42 43 44 45 46 47 48 +9 410 411 Types of sampling Boring types Field sampling Field testing
‘Comparison of in situ tests Standard penetration test in soils Standard penetration test in rock
Overburden correction factors to SPT result
Trang 8Table of Contents vit 412 413 414 415 416 417 418 Pressuremeter test Vane shear
Vane shear correction factor Dynamic cone penetrometer tests Surface strength from site walk over Surface strength from vebicle drive over Operation of earth moving plant
5 Soil strength parameters from classification and testing su 5.2 53 54 sỹ 5.6 57 58 59 5.10 SAL $2 $3 $4 SS 5.16 517 518 s9 5.20 Errors in measurement
Clay strength from pocket penetrometer Clay strength from SPT data
Clean sand strength from SPT data
Fine and coarse sand strength from SPT data Effect of aging
Effect of angularity and grading on strength Critical state angles in sands
Peak and critical state angles in sands Strength parameters from DCP data
CBR value from DCP data
Soil classification from cone penetration tests Soil type from friction ratios
Clay parameters from cone penetration tests Clay strength from cone penetration tests Simplified sand strength assessment from cone penetration tests
Soil type from dilatometer test
Lateral soil pressure from dilatometer test Soil strength of sand from dilatometer test Clay strength from effective overburden 6 Rock strength parameters from classification and testing 61 62 63 64 65 66 67 68 69 Rock strength
Typical refusal levels of drilling rig Parameters from drilling rig used Field evaluation of rock strength
Rock strength from point load index values Strength from Schmidt Hammer
Trang 9vii Table of Contents 6.10 611 6.12 6.13 6.14 6.15 6.16
Rock strength from slope stability Typical field geologists rock strength ‘Typical engineering geology rock strengths Relative strength ~ combined considerations Parameters from rock type Rock durability Material use 7 Soil properties and state of the soil z4 72 73 74 75 76 77 78 79 7.10 71 712 713 714 715 716 AT 7.18 7419 7.20 721 722 723 724 Soil behaviour State of the soil Soil weight Significance of colour
Plasticity characteristics of common clay minerals Weighted plasticity index
Effect of grading
Effective friction of granular soils Effective strength of cohesive soils Overconsolidation ratio
Preconsolidation stress from cone penetration testing Preconsolidation stress from Dilatometer
Preconsolidation stress from shear wave velocity Over consolidation ratio from Dilatometer Lateral soil pressure from Dilatometer test
Over consolidation ratio from undrained strength ratio and friction angles
Overconsolidation ratio from undrained strength ratio Sign posts along the soil suction pF scale
Soil suction values for different materials Capillary rise
Equilibrium soil suctions in Australia Effect of climate on soil suction change Effect of climate on active zones Effect of compaction on suction Permeability and its influence § s2 83 s4 85
‘Typical values of permeability
Comparison of permeability with various engineering materials
Trang 108.6 87 88 89 8.10 8.11 8.12 8.13 8.14 81S 8.16 8.17 8.18 8.19 8.20 Table of Contents ix Effect of pressure on permeability
Permeability of compacted clays
Permeability of untreated and asphalt treated aggregates Dewatering methods applicable to various soils
Radius of influence for drawdown Typical hydrological values
Relationship between coefficients of permeability and consolidation
Typical values of coefficient of consolidation
Variation of coefficient of consolidation with liquid limit Coefficient of consolidation from dissipation tests Time factors for consolidation
Time required for drainage of deposits Estimation of permeability of rock Effect of joints on rock permeability Lugeon tests in rock 9 Rock properties 94 9.2 93 94 9.5 9.6 97 9.8 9.9 9.10 941 9.12 9.13 9.14 9.15 9.16 9.17 General engineering properties of common rocks Rock weight Rock minerals Silica im igneous rocks Hardness scale Rock hardness ‘Mudstone = shale classification based on ‘mineral proportion
Relative change in rock property due to discontinuity Rock strength due to failure angle
Rock defects and rock quality designation Rock laboratory to field strength
Rock shear strength and friction angles of specific materials
Rock shear strength from ROD values
Rock shear strength and friction angles based on geologic origin
Trang 11x Table of Contents Variability of in-situ tests 10.3 10.4 10.5 10.6 10.7 10.8 10.9 10.10 10.11 10.12 10.13 10.14 10.15 10.16 10.17 10.18
Soil variability from laboratory testing Guidelines for inherent soil variability Compaction testing
Guidelines for compaction control testing Subgrade and road material variability Distribution functions
Effect of distribution functions on rock strength Variability in design and construction process Prediction variability for experts compared with industry practice
Tolerable risk for new and existing slopes Probability of failures of rock slopes Acceptable probability of slope failures Probabilities of failure based on lognormal distribution Project reliability Road reliability values Deformation parameters 111 112 113 114 115 11.6 117 118 11.9 11.10 1111 1112 1113 1114 1115 1116 1117 1118 Modulus definitions Small strain shear modulus
Comparison of small to large strain modulus Strain levels for various applications
Modulus applications
Typical values for elastic parameters Elastic parameters of various soils ‘Typical values for coefficient of volume compressibility
Coefficient of volume compressibility derived from SPT
Deformation parameters from CPT results Drained soil modulus from cone penetration tests Soil modulus in clays from SPT values
Drained modulus of clays based on strength and plasticity
Undrained modulus of clays for varying over consolidation ratios
Soil modulus from SPT values and plasticity index Short and long term modulus
Poisson ratio in soils
Trang 12Table of Contents xỉ 11.19 Rock deformation parameters 132 11.20 Rock mass modulus derived from the intact rock modulus 133 11.21 Modulus ratio based on open and closed joints 133 11.22 Rock modulus from rock mass ratings 133 11.23 Poisson ratio in rock 134 11.24 Significance of modulus 135 12 Earthworks 137 12.1 Earthworks issues 137 12.2 Exeavatability 137 12.3 Excavation requirements 137 124 Exeauation characteristics 139 12.5 Excavatability assessment 139 12.6 Diggability index 139 12.7 Diggability classification 140 12.8 Excavations in rock 140 12.9 Rippability rating chart 141 12.10 Bulking factors 142 12.11 Practical maximum layer thickness 143 12.12 Rolling resistance of wheeled plant 143 12.13 Compaction requirements for various applications 144 12.14 Required compaction 145 12.15 Comparison of relative compaction and
relative density 146 12.16 Field characteristics of materials used in earthworks 146 12.17 Typical compaction characteristics of materials used
in earthworks 146 12.18 Suitability of compaction plant 146 12.19 Typical lift thickness 149 12.20 Maximum size of equipment based on permissible
vibration level 150 12.21 Compaction required for different height of fil 150 12.22 Typical compaction test results 150 12.23 Field compaction testing 150 12.24 Standard versus modified compaction 152 12.25 Effect of excess stones 152 l3 Subgrades and pavements 153 13.1 Types of subgrades 153 13.2 Subgrade strength classification 184 13.3 Damage from volumetrically active clays 158 Trung tâm đào tao xây dung VIETCONS
Trang 13xi Table of Contents 134 13.5 13.6 137 13.8 13.9 13.10 13.11 13.12 13.13 13.14 13.15 13.16 13.17 13.18 13.19 13.20 13.21 13.22 13.23 13.24 13.25 13.26 13.27 13.28 14 Slopes 141 142 143 144 145 146 147 14.8 149 14.10 14.11 14.12 1413
Subgrade volume change classification Minimising subgrade volume change Subgrade moisture content
Subgrade strength correction factors to soaked CBR Approximate CBR of clay subgrade
Typical values of subgrade CBR
Properties of mechanically stable gradings Soil stabilisation with additives
Soil stabilisation with cement Effect of cement soil stabilisation Soil stabilisation with lime Soil stabilisation with bitumen Pavement strength for gravels CBR values for pavements CBR swell in pavements
Plasticity index properties of pavement materials Typical CBR values of pavement materials Typical values of pavement modulus
Typical values of existing pavement modulus Equivalent modulus of sub bases for
‘normal base material
Equivalent modulus of sub bases for high standard base material
Typical relationship of modulus with subgrade CBR ‘Typical relationship of modulus with base course CBR Elastic modulus of asphalt
Poisson ratio Slope measurement
Factors causing slope movements Causes of slope failure
Factors of safety for slopes Factors of safety for new slopes Factors of safety for existing slopes Risk to life
Economic and environmental risk Cut slopes
Fill slopes
Factors of safety for dam walls
‘Typical slopes for low height dam walls
Trang 1414.14 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 14.25 14.26 14.27 14.28 14.29
Design elements of a dam walls Stable slopes of levees and canals Slopes for revetments
Crest levels based on revetment type Crest levels based on revetment slope Stable slopes underwater
Side slopes for canals in different materials Seismic slope stability
Stable topsoil slopes
Design of slopes in rock cuttings and embankments Factors affecting the stability of rock slopes Rock falls
Coefficient of restitution Rock cut stabilization measures Rock trap ditch Trenching 15 Terrain assessment, drainage and erosion 15.1 15.2 15.3 Terrain evaluation Scale effects in interpretation of aerial photos Development grades Equivalent gradients for construction equipment Development procedures Terrain categories Landslide classification Landslide velocity scales Slope erodibility
‘Typical erosion velocities based on material ‘Typical erosion velocities based on depth of flow Erosion control
Benching of slopes Subsurface drain designs
Subsurface drains based on soil types Open channel seepages
Comparison between open channel flows and seepages through soils
Drainage measures factors of safety Aggregate drains
Aggregate drainage
Trang 15xiv Table of Contents 16 7 15.24 15.25 15.26 15.27 Resistance to piping Soil filters
Seepage loss through earth dams Clay blanket thicknesses Geosynthetics 16.1 16.2 16.3 16.4 16.5 16.6 16.7 16.8 16.9 16.10 16.11 16.12 16.13 16.14 16.15 ‘Type of geosynthetics Geosynthetic properties Geosynthetic functions
Static puncture resistance of geotextiles Robustness classification using the Gerating Geotextile durability for filters, drains and seals Geotextile durability for ground conditions and construction equipment
Geotextile durability for cover material and construction equipment
Pavement reduction with geotextiles Bearing capacity factors using geotextiles Geotextiles for separation and reinforcement Geotextiles as a soil filter
Geotextile strength for silt fences Typical geotextile strengths Geotextile overlap Fill specifications 171 172 173 174 175 176 177 178 179 17.10 1711 1712 1713 1714 1715 1716 Specification development Pavement material aggregate quality requirements Backfill requirements
Typical grading of granular drainage material Pipe bedding materials
Compacted earth linings Constructing layers on a slope Dams specifications Frequency of testing Rock revetments Durability Durability of pavements Durability of breakwater Compaction requirements Earthworks control
Trang 1619 17.17 17.18 “Table of Contents xv Compaction layer thickness Achievable compaction Rock mass classification systems 18.1 18.2 18.3 184 18.5 18.6 18.7 18.8 18.9 18.10 18.11 18.12 18.13 18.14 18.15 18.16 18.17 18.18 18.19 18.20 18.21 18.22 18.23 18.24 18.25 18.26
The rock mass rating systems Rock mass rating system ~ RMR RMR system ~ strength and ROD RMR system ~ discontinuities RMR ~ groundwater RMR ~ adjustment for discontinuity orientations RMR - application RMR ~ excavation and support of tunnels Norwegian Q system
Relative block size
ROD from volumetric joint count Relative frictional strength
Active stress ~ relative effects of water, faulting, strengthistress ratio
Stress reduction factor
Selecting safety level using the Q system Support requirements using the Q system
Prediction of support requirements using Q values Prediction of bolt and concrete support
using Q values
Prediction of velocity using Q values Prediction of lugeon using Q values Prediction of advancement of tunnel using Q values
Relative cost for tunnelling using Q values Prediction of cohesive and frictional strength using Q values
Prediction of strength and material parameters using Q Values
Prediction of deformation and closure using Q values Prediction of support pressure and unsupported span using Q values Earth pressures 19.1 19.2 193 Earth pressures
Earth pressure distributions
Trang 17xvi Table of Contents
20
2
194 Variation of at rest earth pressure with OCR 19.5 Variation of at rest earth pressure with OCR
using the elastic at rest coefficient
19.6 Movements associated with earth pressures 19.7 Active and passive earth pressures
19.8 Distribution of earth pressure
19.9 Application of at rest and active conditions 19.10 Application of passive pressure
19.11 Use of wall friction
19.12 Values of active earth pressures 19.13 Values of passive earth pressures Retaining walls
20.1 Wall types 20.2 Gravity walls
20.3 Effect of slope behind walls 20.4 Embedded retaining walls
20.5 Typical pier spacing for embedded retaining walls 20.6 Wall drainage
20.7 Minimum wall embedment depths for reinforced soil structures
20.8 Reinforced soil wall design parameters 20.9 Location of potential failure surfaces for
reinforced soil walls
20.10 Sacrificial thickness for metallic reinforcement 20.11 Reinforced slopes factors of safety
20.12 Soil slope facings
20.13 Wall types for cuttings in rock 20.14 Drilled and grouted soil nail designs 20.15 Driven soil nail designs
20.16 Sacrificial thickness for metallic reinforcement 20.17 Design of facing
Trang 18215 21.6 217 21.8 21.9 2110 2111 2112 2113 2114 2115 2116 21.17 21.18 21.19 21.20 2121 21.22 21.23 21.24 21.25 21.26 21.27 21.28 21.29
Bearing capacity factors
Bearing capacity of cohesive soils Bearing capacity of granular soils Settlements in granular soils
Factors of safety for shallow foundations Pile characteristics
Working loads for tubular steel piles Working loads for steel H piles Load carrying capacity for piles Pile shaft capacity
Pile frictional values from sand End bearing of piles
Pile shaft resistance in coarse material based on N= value Pile base resistance in coarse material based on N= value Pile interactions Point of fixity Uplift on piles Plugging of steel piles Time effects on pile capacity
Piled embankments for highways and high speed trains
Dynamic magnification of loads on piled rafts for highways and high speed trains
Allowable lateral pile loads
Load deflection relationship for concrete piles in sands Load deflection relationship for concrete piles in clays Bending moments for PSC piles in stiff clays 22 Rock foundations 22.1 22.2 22.3 22.4 22.5 22.6
Rock bearing capacity based on ROD Rock parameters from SPT data Bearing capacity modes of failure Compression capacity of rock for uniaxial failure mode
Trang 19evi Table of Contents 2B 22.7 22.8 22.9 22.10 22.11 22.12 22.13 22.14 22.15 22.16 22.17 22.18 22.19 22.20
Rock bearing capacity factors
Compression capacity of rock for splitting failure Rock bearing capacity factor for
discontinuity spacing
Compression capacity of rock for flexure and punching failure modes
Factors of safety for design of deep foundations Control factors
Ultimate compression capacity of rock for driven piles
Shaft capacity for bored piles Shaft resistance roughness
Shaft resistance based on roughness class Design shaft resistance in rock
Load settlement of piles Pile refusal Limiting penetration rates Movements 23.1 23.2 23.3 23.4 23.5 23.6 23.7 23.8 23.9 23.10 23.11 23.12 23.13 23.14 23.15 23.16 23.17 23.18 23.19 ‘Types of movements Foundation movements Immediate to total settlements Consolidation settlements Typical self weight settlements Limiting movements for structures Limiting angular distortion
Relationship of damage to angular distortion and horizontal strain
Movements at soil nail walls
Tolerable strains for reinforced slopes and embankments
Movements in inclinometers
Acceptable movement in highway bridges
Acceptable angular distortion for highway bridges Tolerable displacement for slopes and walls Observed settlements behind excavations Settlements adjacent to open cuts for various support systems
Tolerable displacement in seismic slope stability analysis
Trang 2023.20 23.21 23.22 23.23
Levels of rutting for various road functions Free surface movements for light buildings Free surface movements for road pavements Allowable strains for roadways
24 Appendix — loading
24.1 Characteristic values of bulk solids 24.2 — Surcharge pressures
243 Construction loads
244 — Ground bearing pressure of construction equipment 24.5 Vertical stress changes
25 References
25.1 General - most used
Trang 21Preface
his is intended to be a reference manual for Geotechnical Engineers Its principally a data book for the practicing Geotechnical Engineer and Engineering Geologist, which
The planning of the site investigation The classification of soil and rock
‘Common testing, and the associated variability
The strength and deformation properties associated with the test results
© The engineering assessment of these geotechnical parameters for both soil and rock
‘* The application in geotechnical design for: = Terrain assessment and slopes
= Earthworks and its specifications = Subgrades and pavements = Drainage and erosion = Geotextiles = Retention systems = Soil and rock foundations = Tunnels = Movements
‘This data is presented by a series of tables and correlations to be used by experienced geotechnical professionals These tables are supplemented by dot points (notes style) explanations The reader must consult the references provided for the full explanations of applicability and to derive a better understanding of the concepts The complexities of the ground cannot be over-simplified, and while this data book is intended to be a reference to obtain and interpret essential geotechnical data and design, it should not be used without an understanding of the fundamental concepts This book does not provide details on fundamental soil mechanics as this information can be sourced from elsewhere
‘The geotechnical engineer provides predictions, often based on limited data By cross checking with different methods, the engineer can then bracket the results as often different prediction models produces different results Typical values are provided for various situations and types of data to enable the engineer to proceed with the Trung tâm đào tao xây dung VIETCONS
Trang 22xi PreRee
site investigation, its interpretation and related design implications This bracketing of results by different methods provides a validity check as a geotechnical report or design can often have different interpretations simply because of the method used Even in some sections of this book a different answer can be produced (for similar data) based on the various references, and illustrates the point on variations based ‘on different methods While an attempt has been made herein to rationalise some of these inconsistencies between various texts and papers, there are still many unresolved issues This book does not attempr to avoid such inconsistencies In the majority of cases the preliminary assessments made in the field are used for the final design, without further investigation or sometimes, even laboratory testing, This results in a conservative and non-optimal design at best, but also can lead to under-design Examples of these include:
* Preliminary boreholes used in the final design without added geotechnical investigation
Field SPT values being used directly without the necessary comecton factor, which can change the soil parameters adopted
* Preliminary bearing capacities given in the geotechnical report These allowable bearing capacities are usually based on the soil conditions only for a “typical” surface footing only, while the detailed design parameter requires a consideration of the depth of embedment, size and type of footing, location, etc
Additionally there seems to be a significant chasm in the interfaces in geotechnical engineering These are:
* The collection of geotechnical data and the application of such data For example, Geologists can take an enormous time providing detailed rock descriptions on rock joints, spacing, infills, etc Yet its relevance is often unknown by many, except t0 say thar it is good practice to have detailed rock core logging This book should assist to bridge that data-application interface, in showing the relevance of such data to design
© Analysis and detailed design The analysis isa framework to rationalise the intent of the design However after that analysis and reporting, this intent must be trans- ferred to a working drawing There are many detailing design issues that the analysis does not cover, yet has to be included in design drawings for construction purposes These are many rules of thumbs, and this book provides some of these design details, as this is seldom found in a standard soil mechanics text
Geotechnical concepts are usually presented in a sequential fashion for learning This book adopts a more random approach by assuming that the reader has a grasp of fundamentals of engineering geology, soil and rock mechanics The cross-correlations can then occur with only a minor introduction to the terminology
Some of the data tables have been extracted from spreadsheets using known formu- lae, while some date tables are from existing graphs This does mean that many users who have a preference for reading of the values in such graphs will find themselves in an uncomfortable non visual environment where that graph has been “tabulated” in keeping with the philosophy of the book title
Trang 23Preface sexi Many of the design inputs here have been derived from experience, and extrapolation, from the literature There would be many variations to these suggested values, and look forward to comments to refine such inputs and provide the inevitable exceptions, that occur Only common geotechnical issues are covered and more specialist areas have been excluded
‘Again it cannot be overstated, recommendations and data tables presented herein, including slope batters, material specifications, etc are given as a guide only on the key issues to be considered, and must be factored for local conditions and specific projects for final design purposes The range of applications and ground conditions are too varied to compress soil and rock mechanics into a cook-book approach
‘These tabulated correlations, investigation and design rules of thumbs should act asa guideline, and is not a substitute for a project specific assessment Many of these ‘guidelines evolved over many years, as notes to myself In so doing if any table inadver- tently has an unacknowledged source then this is not intentional, but a blur between experience and extrapolation/application of an original reference
Acknowledgements
acknowledge the many engineers and work colleagues who constantly challenge for an answer, as many of these notes evolved from such working discussions In the busy times we live, there are many good intentions, but not enough time to fulfil those intentions Several very competent colleagues were asked to help review this manual, had such good intentions, but the constraints of ongoing work commitments, and balancing family life is understood Those who did find some time are mentioned below
Dr Graham Rose provided review comments to the initial chapters on planning and, investigation and Dr Mogana Sundaram Narayanasamy provided review comments to the full text of the manual Alex Lee drew the diagrams Julianne Ryan provided the document typing format review
Trang 25Chapter I
Site investigation
Geotechnical involvement
‘There are two approaches for acquiring geotechnical data:
= Accept the ground conditions as a design element, ie based on the struc- ture/development design location and configuration, then obtain the relevant ground conditions to design for/against This is the traditional approach — Geotechnical input throughout the project by planning the struc~
ture/development with the ground as a considered input, ie the design, layout and configuration is influenced by the ground conditions This is the recommended approach for minimisation of overall project costs
Geotechnical involvement should occur throughout the life of the project The input varies depending on phase of project
The phasing of the investigation provides the benefit of improved quality and relevance of the geotechnical data to the project
Table 1 Geotechnical involvement
Geotechnical study for types of projects Project phase ‘Smal ‘Medium Lorge FeasibilieyAS Desktop study Desktop study Planning Desktop study! Shee Definition of needs
Preliminary engineering | investigation Site investigation ($1) | Preliminary site investigation | Detailed design Detailed ste investigation (Construction | Inspection Monitoringlinspection Monitoringlnepection
Maintenance Inspection
Impact Assessment Study (IAS)
Planning may occur before or after LAS depending on the type of project Trung tâm đào tao xây dung VIETCONS
Trang 262 Site investigation
1.2 Geotechnical requirements for the different project phases
© The geotechnical study involves phasing of the study to get the maximum benefit The benefits (~20% per phase) are approximately evenly distributed throughout the lifecycle of the project
© Traditionally (currently in most projects), most of the geotechnical effort (>90%) and costs are in the investigation and construction phases
© The detailed investigation may make some of the preliminary investigation data redundant Iteration is also part of optimisation of geotechnical investigations * The geotechnical input at any stage has a different type of benefit The Quality
Assurance (QA) benefit during construction, is as important as optimising the location of the development correctly in the desktop study The volume of testing as part of QA, may be significant and has not been included in the Table The ‘Table considers the Monitoring/Instrumentation as the engineering input and not the testing (QA) input
© The observational approach during construction may allow reduced factors of safety to be applied and so reduce the overall project costs That approach may also be required near critical areas without any reduction in factors of safety Table 12 Geotechnical requirements
Geotechnical Key Model ‘Relative (100% total) Key dota ‘Comments Study “nước Effort Benefit
Delep Geologial <i ~20% Geologelseiing MnorSlcss study model existing data, site history with sigcant (site reconnaissance)
aerial photographs planning beneficz: nd terrain Definition of needs <5% ——-~20% _Justy vestigation Safety plans and requirements and services checks
anticipated costs Physical, environmental and allowable Preliminary Geologeland I% ~20% DephrHidness — PhmingPreimimay #weslgaion geotechnical ‘model and composition Investigation of ‘ofsoils and ~20% of planned
¬ detailed ske investigation
Deniled ste Geotechnical 75% © ~20% Quandmdwe.amd - Laboratory analysis of, invesigation model characterisation of 20% of detailed crtial oF founding soil profile
Monitoring! Inspection <10% ~30% Instrumentation Cnfiems models ae required adopted or ‘QA testing assumptions Increased requirements to adjust
cefort for observational ‘design approach, Trung tâm đào tao xây dung VIETCONS
Trang 27Site investigation 3 Construction costs ~85% to 95% of total capital project costs
Design costs ~5% to 10% of total capital costs Geotechnical costs ~0.1% to 4% of total capital costs Each peaks at different phase as shown in Figure 1.1 Figure 1.1 Steps in effective use of geotechnical inpu throughout all phases ofthe project 1.3 Relevance of scale
‘© Areach stage of the project, a different scale effect applies to the investigation Table 1.2 Relevance of scale
Size study Typical scale Typical phase of project Relevance
Regional 1:100000 Regional studies GIS analysisHazard assessment Medium Large I:25000 110,000 Planning NAS Feasibiliy studies “Terrain/Risk assessment Land units(Hazard analysis
Detailed 12,000 Deailed design Detailed development Risk analysis © GIS Geographic Information Systems
14 Planning of site investigation ‘The SI depends on the phase of the project
‘© The testing intensity should reflect the map scale of the current phase of the study Trung tâm đào tao xây dung VIETCONS
Trang 284 Site investigation Table [6 Suggested test spacing
Phase of project Typical map scale Boreholes per hectare Approximate spacing las Planning 1: 10,000 15,000 01 1902 05-10 200m 100m to 400m to 200m Preliminary design Detailed design 14,000 1:2,000 (Roads) to I:2500 Sto 10 ItoS 50m to 100m 30m to 100m
121,000 (Buildings or ‘10 t0 20 20m to 30m Bridges)
* A geo-environmental investigation has different requirements The following Tables would need to be adjusted for such requirements
© 1 Hectare= 10,000 m?
1.5 Planning of groundwater investigation
Observation wells are used in large scale groundwater studies
* The number of wells required depends on the geology, its uniformity, topography and hydrological conditions and the level of detail required
The depth of observation well depends on the lowest expected groundwater level for the hydrological year
Table IS Relation between size of area and number of ‘observation points (Ridder, 1994), Sze of area under No.of groundwoter study (hectare) observation pants 100 20 1,000 40 10000 100 100000 200 1.6 Level of investigation
* The following steps are required in planning the investigation:
= Define the geotechnical category of the investigation This determines: = The level of investigation required
= Define the extent of investigation required; and "= Hirefuse appropriate drilling/testing equipment 1.7, Planning prior to ground truthing
© Prepare preliminary site investigation and test location plans prior to any ground ‘ruthing This may need to be adjusted on site
Trang 29Table 1.8 Geotechnical category (GC) of investigation Geotechnical category 1 Nature and sie of 2 Surroundings 3 Ground conditions 4 Ground water conditions 5 Seismic, 6 Cost of project 7 S\Costas capital cost % of 8 Type of sudy 3 Miimam level of expertise 10 Examples cl Srall & relatively simple ~ conventional loadings No risk of damage to neighbouring buildings, slits, te Straightforward Does nat apply to refuse, uncompacted fil |oose or highly compressible soil No excavation below water table required Non Seismic -=$05M (Aus ~ 2005) 01-05% (Qualitative investigation may be adequate Graduate civil engineer or engineering geologist lunder supervision by an experienced geotechnical specialist, Sign supports Walls <2m Single or 2-storey buildings 1 Domestic buildings; lighe structures with column loads up 2 250KN or wall loaded to 100kNIm + Seme rosds oa ‘Conventional abnormal loadings Risk of damage to neighbouring Routine procedures for field and laboratory testing Below water table, Lasting damage cannot be caused without prior warning Low seismicity 0.25%-1% Quantcatve geotechnical studies Experienced ‘Geotechnical engineer! Engineering geologist fs Industrial! commercial some buildings « Roads > km + SmalƯmedium, bridges
Services searches are mandatory prior to ground truthing
Further service location tests and/or isolations may be required on site Typically mandatory for any service within 3 m of the test location
* Utility services plans both above and below the ground are required For example, an above ground electrical line may dictate either the proximity of the borehole, Trung tâm đào tao xây dung VIETCONS http://www vietcons or Site investigation 5 oa Large or unusual Extreme risk to neighbouring Specialise tasting Extremely permeable byen, High Setamic areas >§501M (Aus - 2005) 05%-2%
Trang 306 Site investigation
ra drilling rig with a certain mast height and permission from the electrical safety authority before proceeding
« — The planning should allow for any physical obstructions such as coring of a concrete slab, and its subsequent repair after coring
Table 7 Planning checklists Tipe ems
Informative “Timing Authority so proceed, Inform all relevant stakeholders Environmental approvals Access, Site history, Physical obstructions, Positional accuracy required,
Site specific Traffic control Services checks Possible shut down of nearby operational plant safety plans Isolation: require
‘SA Management Checklists Coordination Aims of investigation understood by al Budget limits where cient needs to be advised if additional SI required 1.8 Extent of investigation
‘* The extent of the investigation should be based on the relationship between the competent strata and the type of loadingj/sensitivity of structure Usually this infor- mation is limited at the start of the project Hence the argument for a 2 phased investigation approach for all but small (GC1) projects For example in a piled foundation design:
= The preliminary investigation or existing nearby data (if available) determines the likely founding level; and
= The detailed investigation provides quantitative assessment, targeting testing at that founding level
* The load considerations should determine the depth of the investigation:
= >1.5 xwidth (B) of loaded area for square footings (pressure bulb ~0.2q where q=applied load)
= >3.0 x width (B) of loaded area for strip footings (pressure bulb ~0.2 q) « — The ground considerations intersected should also determine the depth of the
investigation as the ground truthing must provide:
= Information of the competent strata, and probe below any compressible layer
= Spacing dependent on uniformity of sub-surface conditions and type of structure
© Use of the structure also determines whether a GC2 or GC 3 investigation applies For example, a building for a nuclear facility (GC3) requires a closer spacing than for an industrial (GC2) building
Trang 31
Site investigation 7 Table I.8 Guideline to extent of investigation
Development Test spacing ‘Approximate depth of investigation Building 20m to 50m + 2B-4B for shallow footings (Pade and Strip, respectively)
1+ 3m or 3 pile diameters below the expected founding level for piles If rock ineersected ensure — N*> 100 and RQD > 25%
+ šB (building wideh) for rafts or closely spaced shallow footings [LSB below 2/30 (pile depth) for pile rafts
‘At each pier location
Embankmentz 100m to 500m asin roads 25m to 50m (critical areas) Cut Slopes 25m to 50m for H> 5m, 50m to 100m for H<5m Landslip 3 BHs or test pits ‘minimum along critical
Pavementsiroads 250m to 500m Local roads <150m 2 to 3 locations Local roads > 150m 50m to 100m {@ minimarn) Runways 250m to 500m
Pipelines 250m to 500m Tunnels 25m to 50m
Deep tunnels need special consideration
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‘+ 4B-5B for shallow footings 1 10 pile diameters in competent ‘+ Consideration of the fllowing if bedrock intersected
= 3m minimum rack coring = 3 Pile dameters below target
founding level based on =m NT> 150 = RQD> 50%
i= Moderately weathered or better 1» Medium strength or better ‘Beyond bare of compressible “lluvium ae erticalloaded/suspect
areas, otherwise asin roads ‘5m below toe of slope or 3m into bedrock below toe ‘whichever i shallower
Below slide zone As a guide (as the ‘lide zone may not be known) use 2 x height of slope or width of zone ‘of movement ‘or 3minto bedrock below toe Sm below toe of slope
whichever i shallower ‘2m below formation level ‘3m below formation level
| m below invert level
3m below invert level or I tunnel <iameter, whichever is deeper: greater ‘depths where contiguous piles for retentions ‘Target 05-15 linear m drilling per route metre of aligament
Lower figure over water or dificult ‘to access urban areas
Trang 328 Site investigation Table 1.8 (Continued)
Development Test spacing ‘Approximate depth of investigation Dams 25m to 50m 2 x heghr of dam, 5m below toe (oF of slope 3m into bedrock below
toe whichever i greater Extend to zone of low permeability
Canals 100m to 200m 3m minimum below invert level ‘oF toa zone of low permeability Culverts “<20m width (One at each end | Borehole 2B-4B but below bare of ‘compressible layer 20m-40m 40m (One at each end and I in ‘the middle with maximum spacing of 20m between boreholes (Car Parke 2Bhs for = 50 parks 3 Bhs for 50-100 22m below formation level 4 Bhs for 100-200 5 Bh for 200-400 6 Bhs for > 400 parks
Monopoles and transmission At each location Om to 20m high:D=45m 20m to 30m high:D towers 40m to 50m high:D 30m to 40m high: D
60m to 70m high: D 70m to 80m high: D
‘Applies to medium dense to dense ‘sands and sift very stif clays Based on assumption on very lightly loaded structure and lateral loads are the main considerations Reduce D by 20% to 50% ifhard clays, very dense sands or competent rock Increase D by >30% for loose sands ‘and soft clays N¢ Inferred SPT value RQD-Rock Quality Designation H-Height of slope D-Depth of investigation
Ensure boulders or layers of cemented soils are not mistaken for bedrock by penetrating approximately 3m into bedrock
© Where water bearing sand strata, there is a need to seal exploratory boreholes especially in dams, tunnels and environmental studies
Any destructive tests on operational surfaces (travelled lane of roadways) needs repair
© In soft/compressible layers and fills, the SI may need to extend BHs in all cases to the full depth of that layer
Samples/Testing every 1.5m spacing or changes in strata
Obtain undisturbed samples in clays and carry out SPT tests in granular material Trung tâm đào tao xây dung VIETCONS
Trang 33Site investigation 9 1.9 Volume sampled
‘+ The volume sampled varies with the size of load and the project
‘© Overall the Volume sampled/volume loaded ratio varied from 10* to 108 Earthen systems have a greater sampling intensity
Table 1.9 Relative volume sampled (simplified from graph in Kulhawy, 1993),
Type of development Typical volume sampled Typical vaume loaded Relative volume sampled Volume loaded Buildings 04m) 2x 10'm 1
Conerete dam Lom 5x 105m 1 Earth dam 100m? 5 10m lơ
1.10 Relative risk ranking of developments
‘© The risk is very project and site specific, ie varies from project to project, location and its size
‘The investigation should therefore theoretically reflect overall risk
Geotechnical Category (GC) rating as per Table 1.6 can also be assessed by the development risk
‘© The variability or unknown factors has the highest risk rank (F), while certainty hhas the least risk rank (A):
= Projects with significant environmental and water considerations should be treated as a higher risk development
= Developments with uncertainty of loading are also considered higher risk, although higher loading partial factors of safety usually apply
‘© The table is a guide in assessing the likely risk factor for the extent and emphasis of the geotechnical data requirements
‘© The table has attempted to subdivide into approximate equal risk categories It is therefore relative risk rather than absolute, ie there will always be unknowns even in the low risk category
1.11 Sample amount
‘The samples and testing should occur every 1.5m spacing or changes in strata Obtain undisturbed samples in clays and carry out penetration tests in granular material
© Do not reuse samples e.g do not carry out another re-compaction of a sample after completing a compaction test as degradation may have occurred
Trang 3410 Site investigation Table I.10 Risk categories
Development Risk factor considerations
Loading Emwonment Weter Ground Economic Lfe Overall
Offshore Pltforms Exthdim> Im Tunnels Power stations
Ports & coastal developments Nuclear, chemical, & biological complexes Concrete dams Contaminated land “Taling cams Mining Hydra structures Buldngs storing ‘hazardous goods Land Sub = stations Rai embankments Eanh đăng 515m Coferbms Chưnngghols >7m Railway bridges Petrol ations Road embankments Mining waste Highway bridges Transmision tines Deep basement:
Office bulings > 15 levels Earth dams <'m Apartment buldings > 15 levels Roads Pavements Public buildings Furnaces Culverts Towers Sos Heavy machinery ‘Ofice buildings 5-15 levels Warehouses, buildings High sĨ gxommx gxommx oma men Serious oa Moderate SC2 Usual SC2 ammmồaoaonàaoaongømịøø» gøomịmo onmmmm osonoanszaoầnøịøàị_ mgommo osoosmgmsøịgem>ịgoagmịøogø_ amomg m o>øøøao søao>àịgmpøoo_amomm m =0øzoooœøòomòøooòøòøøø_òøøom om>øø00o0000000000000mmm mog0m m š § 4
Trang 35Site investigation I! ° 2 Evang ‘Poa nageas groan mas
Figure 1.2 Site ground considerations Table I.11 Disturbed sample quantity
Test ‘Minimum quantity Soil sablieation 100kg
CN 40k ‘Compaction (Moisture Density Curves) 20kg Particle sizes above 20mm (Coarse gravel and above) 10kg Particle sizes les than 20mm (Medium gravel and below) 2k Particle sizes less than 6mm (Fine gravel and below) 05kg Hydrometer test ~ particle size less than 2mm (Coarse sand and below) 025kg LAerberg test 05k
1.12 Sample disturbance
© Due to stress relief during sampling, some changes in strength may occur in laboratory tests
Table |.12 Sample disturbance (Vaughan eta, 1993)
faves SEY) go eee Soft ely Low High Very large decrease Large decrease
Sif clay High Low Negligible Large inerease Trung tâm đào tao xây dung VIETCONS
Trang 3612 Site investigation 1.13, Sample size
* The sample size should reflect the intent of the test and the sample structure * Because the soil structure can be unknown (local experience guides these deci-
sions), then prudent to phase the investigations as suggested in Table 1.1 Table 1.13 Specimen size (Rowe, 1972)
oy ype Macr-fbric ‘Mass permeabily, kms Parameter Specimen size (mm) Non fissured None th aco 7
sensitivity <5 me 76 High pedals, 10-¥ zo 10% cà 00-250 sand kyers, cy oF inclusions ‘organic veins ™ ` ® 250 Sand layers >2mm 10 to 10-# a-<0.2m spacing co 7 8 Sensitivity >$ Cemented with any above 50-250 Fissured Plain fissures lớn 250 100
7 Silt or sand fsures — 10°'to 107% 250 100
L3 Jointed ‘Open jones 100
Pre-existing sip 150 or remoulded
4 Quality of site investigation
* The quality of an investigation is primarily dependent on the experience and ability of the drilling personnel, supervising geotechnical engineer, and ade- quacy of the plant being used This is not necessarily evident in a cost only consideration
‘* The Table below therefore represents only the secondary factors upon which to judge the quality of an investigation
© A good investigation would have at least 40% of the influencing factors shown, ie does not necessarily contain all the factors as this is project and site dependent
« An equal ranking has been provided although some factors are of greater importance than others in the Table This is however project speci
* The table can be expanded to include other factors such a local experience, prior knowledge of project/site, experience with such projects, etc
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Trang 37Table I.14 Quality of a detailed investigation Site investigation 13
——— Quek of ste imesigaton | Comments Good | FeNormel | Poor
Quan offerors >70% 40% to 70% | <40% | 10 factors provided herein Phasing of investigation Yes No [Refer Table 12
Seery and envionment plan Yes No_[Reter Table 17
Tesvtiecare + Buldings/Bridges aro] 10 | <to | Tess canbetorshaes exis Refer Table 1.4 for detailed design ụ "¬ nh ct 5 <5 | tests from previous phasing included cone penetration tests, ete Relevant Extent ofnvestintion ri Yes No |Refer Table 18
Dept mengaden Yee | No [Retr Tale Le
adequate to ground
Sample amounesufcientfor | ye, No | Refer Table 1
lsb esine
ee ee Yes No | Refer Table 1.13
otsamplescestinginthe | ogy] = Assuming quality samples obsained in
laboratory 20%) 10% | <I0% | very TP and every 1.5m in BH+
Sample ested a relevant This involves knowing the depth of ress range Yes No | sample (or currene overburden pressure), and expected lading Budge as %ofcapial works | 502% |<02%[Valoeshoudbe gpiiomdy hgher for dams, and erteal projects
(Table 1.16)
1.15 Costing of investigation
The cost of an investigation depends on the site access, local rates, experience of driller and equipment available These are indicative only for typical projects For example, in an ideal site and after mobilisation, a specialist Cone Penetration
‘Testing rig can produce over 200 mfday
There would be additional cost requirements for safety inductions, traffic control, creating site access, distance between test locations
The drilling rate reduces in g cavels
Trang 3814 Site investigation Table I.15 Typical productivity for costing (Queensland Australi) Dailing Sail Soft rock Hard rock Land based driling 20miday 1Smiday | 10m coring/éay
‘Cone penetration testing
(excludes dspation testing) | '@Pm/dey_| Netaprlcable | Not apleable
(Highly dependent on weather/tides/location) ng ‘Non Cyclonic Months ‘Cyclonic Month barge | Open water | Land based x 50% Land based x 30%
‘Sheltered water | Land based x 70% Land based x 50% (Dependent on weather/location) Non Cyclonic Months ‘Cyclonic Month Jack up ya
barge [Open water | Land based x 70% Land based x 50% ‘Sheltered water | Land based X 90% Lané based x 70% © Over water drilling costed on daily rates as cost is barge dependent rather than metres drilled ‘Jack up barge has significant mobilisation cost associated ~ depends on location from source
6 Site investigation costs
* Often an owner needs to budget items (to obtain at least preliminary funding) ‘The cost of the SI can be initially estimated depending on the type of project * The actual SI costs will then be refined during the definition of needs phase
depending on the type of work, terrain and existing data * A geo-environmental investigation is costed separately Table I.16 Site investigation costs (Rowe, 1972)
Type of work % of copia cost of works 1% of earthworks and foundation costs Earth dams 089-330 114-520 Railways 060-200 3s Roads 020-155 140-547 Docks 023.050 048-167 Bridges 012-050 026-130 Embankments 012-019 016-030 Buildings ‘Overall mean 005-022 07 050-200 15
Trang 39Site investigation IS © Overall the % values for buildings seem low and assume some prior knowledge of the site © Avvalue of 0.2% of capital works should be the minimum budgeted for sufficient information
‘* Thelaboratory testing for a site investigation is typically 10% to 20% of the testing costs, while the field investigation is the remaining 80% to 90%, but this varies depending on site access This excludes the professional services of supervision and reporting There is an unfortunate trend to reduce the laboratory testing, with inferred properties from the visual classification and/or field testing only 1.17 The business of site investigation
‘© The geotechnical business can be divided into 3 parts (professional, field and laboratory)
* Each business can be combined, ie consultancy with laboratory, or exploratory with laboratory testing:
There is an unfortunate current trend to reduce the laboratory testing, and base the recommended design parameters on typical values based on field soil classifications This is a commercial/ competitive bidding decision rather than the best for project/optimal geotechnical data It also takes away the fieldlaboratory check essential for calibration of the field assessment and for the development and training of geotechnical engineers
Table I.17 The three “businesses” of sie investigation (adapted from Marsh, 1999)
The services Provision of professional services Exploratory holes Laboratory testing Employ Engineers and Scientists Drillers and ftters Lab technicians Use Live in Offices Brain power and computers Rigs, plant and equipment Equipment PlantYards and workshops Laboratories and stores
QAwih — CPEng Licensed Driler,ADIA NATA Investin CPD and sofeware Plant and equipment [Lab equipment Worry about <1600 chargeable hours achieving a year per member of staff per drill ig <1600m driled a year tested per year per <1600 Plasticity Index
technician
CCPENG Chareered Professional Engineer: CPD Continuous Profesional Development: NATA Navona Associaton of Testing Authories:ADIA Australan Dring Industry Assocation