geotechnical
TRANSCRIPT
Copyright of RSK
Geotechnical and environmental considerations when redeveloping deep-filled and former landfill sites
15 April 2023 1
Peter Witherington Managing Director
Copyright of RSK 15 April 2023 2
Introduction
Significant constraints:
Social
Economic
Environmental
Engineering
Copyright of RSK 15 April 2023 3
BRE 424 Charles and Watts
Copyright of RSK 15 April 2023 4
The problem of deep fill
Received little research attention
“…the heterogeneous nature of many waste fills makes characterisation and analysis difficult, and it is easy to understand why the attention of geotechnical engineers has usually focussed on more promising and better behaved natural soils…”
BRE reaction:
Monitoring of field performance
Characterising fills on the basis of observed performance
Assessing the effectiveness of various ground-treatment techniques
Dr J. A. Charles, 2008 Rankine Lecture, ‘The engineering behaviour of fill materials: the use, misuse and disuse of case histories’
Copyright of RSK 15 April 2023 5
Settlement mechanisms
Applied loading is rarely the problem…
However, we must address
Self weight
Change of groundwater level
Collapse settlement
Decomposition of biodegradable material
Chemical decomposition
Copyright of RSK 15 April 2023 6
How to investigate properties
Conventional investigation is of little use.
Difficulty of
Drilling
Sampling
In situ testing
Laboratory testing
Need for
Long-term monitoring of
surface settlement
groundwater level
Large and medium-size loading tests
Copyright of RSK 15 April 2023 7
Treatment methods
“With non-engineered fills the unexpected is only too likely to occur. Ground treatment before construction can mitigate or forestall the effects of the unexpected.”
Consider
Engineered backfilling
Dynamic compaction
Vibro compaction
Pre-loading (surcharging)
Pre-inundation
Copyright of RSK
Opportunity?
15 April 2023 8
Copyright of RSK
Opportunity!
15 April 2023 9
Copyright of RSK
Opportunity?
15 April 2023 10
Copyright of RSK 15 April 2023 11
Three centuries of mining
Copyright of RSK
Opportunity!
15 April 2023 12
Copyright of RSK
Investigations: instrumentation
15 April 2023 13
Copyright of RSK 15 April 2023 14
Load tests
Copyright of RSK 15 April 2023 15
Load tests
Copyright of RSK 15 April 2023 16
Load tests
Copyright of RSK
And?
15 April 2023 17
Copyright of RSK
How about other sites?
Research in 1980/90’s jointly with BRE into the performance and Stiffened End Slabs (SES)
• Light and Heavy
• Types of Made Ground:
• Type A – Engineered Made Ground (any age)
• Type B - Cohesive Made Ground >50 years old or Granular >20 years old
• Type C – Cohesive Made Ground 20-50 years old of granular <20 years old
• Type D cohesive made ground <20 years old
• Methods of SI
• Specifications for Loading tests
• Skip tests
• Large Loading tests
15 April 2023 18
Copyright of RSK
Former Gravel pit and Landfill on South Coast
15 April 2023 19
Copyright of RSK
A site in the South East
15 April 2023 20
Copyright of RSK 15 April 2023 21