Table of Contents for Volume 1
(provides an indication of the full scope of the book)
Preface
Introduction
Layout of book
Colour coding of tables and graphs
Case studies
Acknowledgements
The case for trees
The case against trees
The nature of the problem
A multi-disciplinary approach
The extent of the problem
Summary
Case Study
Heave damage caused by root barrier - Extensive persistent deficit from poplars - Incorrect diagnosis of subsidence based on timing of damage and erroneous visual observations - Value of level distortion survey - Significance of dead roots - Heave damage can develop in summer.
Xylem
Phloem
Cambium and growth
The control of growth, and carbon economy
Leaf function and transpiration
Moisture deficits, suction and water potential
Relationship between growth and transpiration rate
Annual cycle of growth
Summary
Additional reading
Case Study 2
Oak causing damage to semi-detached house - Engineer's concern of heave - No evidence of persistent desiccation - Tree felled -Level monitoring shows 80% recovery in first winter - No subsequent damage.
Introduction
Overall shape of root system
The root:shoot ratio
Initial root growth
The fine, moisture-absorbing, roots
Factors affecting root growth
Control of root growth
Conducting roots
Structural roots
Root mortality
Root regeneration
The root as a storage organ
Summary
Additional reading
Case Study 3
Mature oak tree 1.5m from building on London clay - No external damage and no movement - Water requirements of tree provided from within bands of sand - Settlement of floor slab unrelated to tree.
Introduction
The origins of soils
Particle size
Mineralogy of clay
Water and clay minerals
Behaviour of water in sandy soils
Behaviour of clay soils;
a) moisture release
b) shrinkage
Behaviour of soils of intermediate structure
Soil moisture deficit
Soil moisture deficits and soil shrinkage
Soil cracking
Shrinkage and swelling potential
Relevance of plasticity index to soil shrinkage in the field
Soil permeability
Relationship between gravimetric and volumetric moisture content
Water potential and moisture content
Summary
Case Study 4
Bungalow underpinned after subsidence in 1976 - Cypress trees felled - Subsequent damage diagnosed as settlement of underpinning caused by softening of soil - Such explanation inconsistent with damage - Monitoring demonstrates heave - Engineers negligent and liable - Heave continuing and bungalow demolished.
Chapter 5. Seasonal Changes in Soil Moisture Content
Introduction
Seasonal development of soil drying
Seasonal development of moisture deficit
Seasonal fluctuations of soil moisture deficit
Soil drying by evergreen vegetation
Soil drying by grass
Soil drying in absence of vegetation
Seasonal fluctuations in water table
Influence of soil type on seasonal moisture deficits
Effect of pruning on seasonal changes
Summary
Case Study 5
Single storey school building on Boulder Clay - Damage caused by various adjacent poplars - Initial tree felling stabilised parts of building - Additional felling and eventually hedge removal required for complete stability - Level monitoring essential to demonstrate effects of tree removal.
Chapter 6. Persistent Moisture Deficits
Assumed persistent deficits
Development and maintenance of persistent deficit
Recovery from persistent deficit
Recovery from persistent deficit as result of overmaturity
Factors conducive to development of persistent deficit
Effect of pruning on persistent deficit
Summary
Case Study 6
Extensive damage to old house near horse chestnuts and vigorous young Turkey oak tree - Persistent deficit from oak tree allowed to develop - TPO imposed - Trees felled - Monitoring shows long-term recovery from effect of oak tree, but rapid recovery from horse chestnuts.
Chapter 7. Interaction Between Trees and Buildings
Introduction
0 Soil movements
Seasonal movements
Influence of foundation load
Effect of dynamic foundation movement
Movements caused by persistent deficits
The effect of the development of a persistent deficit on a building
Heave as result of building on a pre-existing persistent deficit
Angular distortion and damage
Influence of building on soil permeability
Influence of building on root growth
Exclusion of rainfall by buildings and other impermeable surfaces
Summary
Case Study 7
Terrace of 3 properties - Central one underpinned - 28mm seasonal movements continue - Damage exacerbated - Dynamic settlement - Level monitoring essential for diagnosis - Oak tree felled to restabilise most of building - Minor continuing predicted recovery.
Chapter 8. Influence of the Weather
Introduction
Evolution of MORECS Versions 1.0 and 2.0
Available water content
SMD modelling for different crops
Comparison between years
Comparison of SMD in different areas
Comparison between calculated and actual SMD
Limitations of calculated SMD
Global warming and climate change
Summary
Case Study 8
Crack in flank wall allegedly consistent with involvement of adjacent lime tree - Timing of crack movement inconsistent with seasonal soil movements - Gravel soil - Level monitoring confirms no foundation movements occurring.
Chapter 9. Comparative Effects of Different Species, and of Individual Trees and Groups
Phenotypic variation
Intra-specific variation
Is inter-specific variation to be expected?
Criteria for comparing effect of different species on soil and buildings
Rank order based on radial spread of roots
Rank order based on propensity to cause damage
Rank order based on 'water demand'
Stock / scion interaction
The effects of rows and groups of trees
Shrubs
Summary
Case Study 9
Hedgerow, including vigorous oak tree, closely adjacent to flank wall - Previous underpinning inadequate - Level monitoring demonstrates 11mm seasonal movement - Selective felling and pruning reduce amplitude to less than 2mm - Further damage prevented.
Chapter 10. Other Forms of Damage by Tree Roots
Direct Physical damage
Mechanism of damage
Reaction of roots to mechanical impedance
Calculation of forces causing direct damage
Studies on damage to pavements and kerbs
Direct root penetration of brick walls
Diagnosis of physical damage
Prevention and repair of direct damage
Remedial action to trees to prevent damageDamage to drains and underground services
Root invasion of drains
Role of roots in initiating damage
Prevention and repair of damage to drains
Damage to other underground services
Summary
Additional reading
Case Study 10
Bulbous base of tree trunk in contact with wall causing direct damage - No distortion where adequate lateral restraint from floor joists and foundations - Removal of encroaching tissue allowed wall to be rebuilt and retention of tree.
Chapter 11. Strategy for Investigating Damage
Causes of Damage
Objectives of investigation
Scope of investigations
The role of monitoring
Cost effectiveness of investigation
Reviewing the results of investigations
Summary
Case Study 11
Long history of minor damage - Site conditions make underpinning impractical - Felling Monterey cypress stabilises front corner - Continuing movements of rear corner stabilised after pear tree is felled.
Chapter 12. Site Investigations I) The Building
Objectives
History of site
Analysis of damage to the building
History of damage
Recording of cracks
Severity of damage
Measurement of the distortion of the building
Methods of measuring levels:
i) Water level
ii) Optic level
Levelling staff
Presentation of level results
Interpretation of level surveys
Verticality survey
Foundation depth and construction
Foundation load
Drain and services survey
Summary
Case Study 12
Property suffered damage in 1975 and 1976 - Underpinned in 1978 but further damage - Level distortion survey sufficient to indicate wrong part of building underpinned - Subsequent investigation confirmed extensive poor quality fill - Tree incorrectly implicated.
Chapter 13. Site Investigations II) The Soil
Introduction
Geological Survey maps
Boreholes
Assessment of soil conditions
Inspection for fine root activity
Particle size analysis
Classification of soil shrinkage
Moisture content determination
Soil suction
Field determination of shear strength
Assessment of desiccation
Limitations in assessment of desiccation:
i) by comparison of profiles
ii) from soil classification tests
Summary
Additional reading
Sources of equipment
Case Study 13
Bungalow built close to overmature oak tree - Dieback of tree allows soil to rehydrate and heave - Subsequent recovery of tree starts seasonal movements and damage - Tree eventually felled - Monitoring shows restability achieved with minimal further heave.
Chapter 14. Site Investigations III) The Tree
Objectives
Introduction
Botanical nomenclature
Identification
Relevance of root identification
Methods for root identification
Age and condition of roots
Measurement of size of tree
Determination of age and growth rate
Interpretation of patterns of radial growth
Water requirements derived from increment cores
Other indications of growth rate
Safety and condition of the tree
Summary
Additional reading
Case Study 14
Previous incorrect diagnosis of subsidence rather than heave - Unsuitable underpinning design - Continuing damage - Level monitoring demonstrates seasonal and ongoing heave movements - Interpretation complicated by lack of deep datum.
Chapter 15. Monitoring Building Movement
Introduction
When to monitor
When to start monitoring
Methods of level monitoring
Equipment for level monitoring
Location of monitoring stations
The use of a datum
Timing and frequency of readings
Calculation and presentation of results
Significance of extent of changes in level
Crack monitoring
Monitoring of soil moisture content
Summary
Additional reading
Case Study 15
Partial underpinning of semi-detached building - Ineffective root severance - Continuing seasonal movement of rest of building of up to 38mm amplitude - Angular distortion and damage made worse by underpinning - Close correlation between moisture deficit and building movement.
Chapter 16. Heave and Recovery - Diagnosis and Prediction
Introduction
A persistent moisture deficit - the essential pre-requisite for heave
Factors influencing amount, rate and duration of heave or recovery
The initiation of heave
The diagnosis of heave
Diagnosis of recovery movements
Relevance of determining age of tree and age of building
Prediction of risk and duration of heave or recovery if trees are felled
Simple guidelines for heave prediction
Quantitative prediction of heave or recovery
Measurement of swelling potential
Remedies for heave damage
Summary
Case Study 16
Seasonal movements of reinforced raft on piles - Defective piles - Estimate of major heave potential - No allowance for heave in foundation design - Engineer liable for defective design - No options for tree management.
Chapter 17. Remedial Action After Damage
Tolerating the damage
Restabilising the soil and foundations by controlling the water uptake of the tree
Tree felling to stop water uptake
Tree felling in stages
Tree pruning to control water uptake
Control of size by plant growth regulators
Watering tree to reduce damage
Root barriers to control root spread
Root severance
Accelerated recovery by watering-in
Allowing natural recovery
Checking the efficacy of remedial action
Stabilising the foundations by underpinning
The choice of action
Superstructure repair
Summary
Additional reading
Address
Case Study 17
Block of flats with independent deep foundations for flank wall - Severe subsidence from closely adjacent tree- Polythene around foundations preventing seasonal recovery - Trees felled and recovery accelerated by watering-in, providing rapid and effective remedy.
Chapter 18. Prediction and Prevention of Damage
Introduction
The prediction of damage
Prevention of damage
i) a) for new buildings near existing trees
i) b) for new buildings without existing trees
ii) for existing buildings with existing trees
A method of risk prediction
Efficacy of Subsidence Risk Factor (SRF)for predicting damage
Implications of subsidence risk assessment
Preventative pruning in identifiable high risk situations
iii) if tree planting near existing buildings
Implications of future changes in risks of damage
Summary
Case Study 18
Bungalow on sloping site with extensive fill, suffered extensive damage in 1980 - Insufficient funds for full remedial scheme - Partial underpinning - Further damage - Level monitoring confirms continued movements including underpinned areas - Lack of datum prevents distinction between heave or slope instability.
Chapter 19. The Legal Framework
Statutory controls on tree work
Introduction
The objective of TPO's
Objecting to a TPO
Determining whether a tree is covered by a TPO
Exemptions to a TPO
Application for consent for tree work
Appeals against decision of LPA
Compensation in respect of TPO's
Obligation to replant
Trees in Conservation Areas
Planning ConditionsLegal liability for damage
Extent and cause of damage
Legal limitation and the time of events
Foreseeability and the scope of duty
Liability for underpinning against heave
Summary
Case Study 19
Victorian property on steeply sloping London Clay site - Trees closely adjacent down-slope - Long history of damage - Crack monitoring demonstrates seasonal and progressive movements - Removal of trees produces no benefit - Seasonal movements apparently caused by natural drainage.
Chapter 20. A Revised Role for the Professions
Introduction
A role for insurers
A role for loss adjusters
A role for structural engineers
A role for arboriculturists
A role for surveyors and valuers
A role for soil scientists
A role for planners
A role for building control
A role for architects and for builders
Summary
Semi-detached house with reinforced raft foundations on Kimmeridge Clay - Comparison of level distortion surveys indicates about 30mm seasonal movement - Root barrier inappropriate - Trees felled - Level monitoring showed slight continuing recovery.
References
Cross Reference of Botanical and Common Names
Index