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1 Engineering characterization of earthen construction materials Charles Augarde School of Engineering Durham University.

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Presentation on theme: "1 Engineering characterization of earthen construction materials Charles Augarde School of Engineering Durham University."— Presentation transcript:

1 1 Engineering characterization of earthen construction materials Charles Augarde School of Engineering Durham University

2 2 Introduction This is an introduction to some of the research work taking place at Durham in earthen construction materials My background: local authority civil engineer for six years in Manchester... got a bit bored... did an MSc and a PhD and ended up as an academic at Durham (there since 2001). Most of my research is in computational mechanics Got into earthen things about six years ago.

3 3 EBUK relevant research areas 1. Characterization of earthen construction materials at the material level What is new? We come from the geotechnical engineering POV We come from the geotechnical engineering POV With respect, not all past characterization work has been rigorous With respect, not all past characterization work has been rigorous 2. Historic rammed earth structures, their history, conservation and the lessons they teach us for modern build What is new? Crossover with archaeologists Crossover with archaeologists We bring structural knowledge and seek help for new build We bring structural knowledge and seek help for new build

4 4 EBUK relevant research areas 1. Characterization of earthen construction materials at the material level What is new? We come from the geotechnical engineering POV We come from the geotechnical engineering POV With respect, not all past characterization work has been rigorous With respect, not all past characterization work has been rigorous 2. Historic rammed earth structures, their history, conservation and the lessons they teach us for modern build What is new? Crossover with archaeologists Crossover with archaeologists We bring structural knowledge and seek help for new build We bring structural knowledge and seek help for new build

5 5 1. Characterization What is the source of strength in these materials (generally compacted earthen materials are our primary interest) What is the source of strength in these materials (generally compacted earthen materials are our primary interest) How do the materials “work” on an engineering level How do the materials “work” on an engineering level Why is this important? Wider acceptance and use flows from better understanding via things like design codes Why is this important? Wider acceptance and use flows from better understanding via things like design codes

6 6 Sources of strength The sandcastle problem The sandcastle problem Suction is one source Suction is one source We can measure suction We can measure suction Tensiometers Tensiometers

7 Suction is the key to many interesting geotechnical engineering problems 7 (Figure above after Wheeler et al., 2003) Meniscus water Air Bulk water “Pendular” and “funicular” regimes

8 Unsaturated soils testing lab 8 Long track record in this at Durham led by David Toll Requires environmental control Complex kit – e.g. double – wall triaxial cells

9 Measuring suction Tensiometers – high capacity (up to 1.5MPa of suction) Tensiometers – high capacity (up to 1.5MPa of suction) Filter paper method (for higher suctions: drier mixes) Filter paper method (for higher suctions: drier mixes) 9 1 – Pressure transducer; 2 – Water reservoir; 3 – Ceramic disc with high air entry value. 312

10 10 Some results Mix from Aykley Heads, Durham RE wall (Rivergreen Developments) Mix from Aykley Heads, Durham RE wall (Rivergreen Developments) Details are in a soon-to-appear Géotechnique paper Details are in a soon-to-appear Géotechnique paper

11 RE testing 11 Tests done at constant water content, unconfined

12 12 Getting drier These results show how suction varies during testing

13 13 Other work in the lab Work done via PhD, MSc and Undergraduate projects at Durham Modes of wetting and drying in compacted earth materials, suction changes are hysteretic Modes of wetting and drying in compacted earth materials, suction changes are hysteretic Stabilisers from “wastes” – Basic Oxygen Slag (BOS) Stabilisers from “wastes” – Basic Oxygen Slag (BOS) Strength between lifts in rammed earth Strength between lifts in rammed earth The use of geogrids The use of geogrids New tests for compacted earth materials New tests for compacted earth materials

14 14 Other work More stabiliser = higher suction

15 15 Other work in the lab Inter-lift strength in rammed earth Inter-lift strength in rammed earth Reinforcement with geo grids Reinforcement with geo grids

16 Tests for compacted earth materials

17 17 What’s happening right now? Q: how does the way you build create the microstructure? Q: how does the way you build create the microstructure? Ingredients: earth, water, time, compaction procedure,... Ingredients: earth, water, time, compaction procedure,...

18 18 EU FP7 bid, Feb 08 Durham (Me), Nottingham (Matthew Hall), CRATerre (Hugo Houben), EPSCI Paris (Henri Van Damme), Technische Universität Berlin (Klaus Rückert), University of Natural Resources and Applied Life Sciences, Vienna (Wei Wu) + industrial partners: Earth Structures (Europe) Ltd (UK), Pitance PLC, (France), Natur und Lehm GMBH (Austria)

19 19 2. Historic rammed earth Collaboration between Engineering and Archaeology Collaboration between Engineering and Archaeology Paul Jaquin Paul Jaquin What can we learn from old structures? What can we learn from old structures? What are robust methods of conserving historic RE? What are robust methods of conserving historic RE?

20 20 Historic rammed earth Paper just out on historical background, based on part of Paul’s thesis

21 21 Acknowledgements Dr Paul Jaquin, Ex-PhD student, Now appearing at RambollWhitbybird Civil Engineering consultants, Edinburgh Dr Chris Gerrard, Dept of Archaeology, Durham University Students MSc: Cindy McChlery MEng: Tom Horncastle, Tom Howard, Steven Perkins PhD: Chris Beckett Thank you for listening. Please pay us a visit. Papers available from me or at (under construction as they say...)


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