Minutes of an informal discussion of some TC35 possibilities

 

 

Occasion: Visit by Malcolm BOLTON to Yamaguchi University, 7-8 July 2000

Others present: Masayuki HYODO, Yukio NAKATA, Adrian HYDE, Thallak SITHARAM

Objective:  Informal exchange of ideas concerning the possible future activities of TC35

 

 

1.  Malcolm Bolton (MB) explained that the Secretary General of ISSMGE had invited Secretaries of National and Regional Groups to select members of TC35, following MBfs earlier recommendation of names of core members. Although formalities would lead to some further delays, it is timely to discuss future plans.

 

2.  The website of ISSMGE now included a section on Technical Committees which included text on TC35 drafted by MB after discussions with other core members. The terms of reference of TC35 (see www.issmge.org/Technical_Committees/tc_record.cfm?TCID=35) are:

 

1. To promote co-operation and exchange of information about the behaviour of soil grains and granular interactions, so as to clarify the fundamental micro-mechanisms of the behaviour of soils.

2. To encourage a micro-structural understanding of significant macroscopic behaviours such as compressibility, anisotropy, yielding, creep, cyclic liquefaction, shear rupture and tensile fracture.

3. To open up a discussion on the use of micro-structural measurements to clarify the selection and raise confidence in the use of continuum parameters in engineering practice.

4. To co-operate with other groups to provide a focus for the physical origins of ground behaviour related to micro-structure; links will be sought with TC34 Deformation of Earth Materials, TC29 Stress-Strain Testing of Geomaterials in the Laboratory, TC26 Calcareous Sediments, TC25 Tropical and Residual Soils, TC22 Indurated Soils and Soft Rocks, and TC2 Centrifuge and Physical Model Testing.

5. To widen the scientific basis of geomechanics by linking with groups applying micro-mechanics to the study of granular materials in other fields of application such as rock mechanics, metal powders, ceramic pressings, and food processing.

6. To facilitate discussions between research workers proposing DEM numerical simulations of soil aggregates and researchers using corresponding laboratory tests, especially with regard to the observation of grain crushing and reorientation.

7. To maintain the existing working group on soil crushability, and to report progress at a workshop to be organised as part of a Satellite Conference to the 15th ICSMGE, Istanbul, in August 2001. This venue will also provide the first opportunity for a meeting of the full TC35.

8. To work towards the promotion and planning of an International Symposium on Micro-Geomechanics to be held at some time between the 15th and the 16th ICSMGE to disseminate progress across the whole field defined in these terms of reference.

 

3.  MB asked for feedback on item 7 above - the request made by Professor Kenji ISHIHARA, President of ISSMGE, that MB consider the possibility of organising a special joint meeting of TC35 gMicro-geomechanicsh with Ioannis VARDOULAKISfs TC34 gDeformation of Earth Materialsh. This led to a fruitful discussion of what contribution on soil mechanics could be made by TC35 members, which would be distinct from those of TC34 members or others. It was felt that the motivation for TC35 arises from the physical observations of soil grains, whereas the motivation for TC34 derives from mathematical models in continuum mechanics. In that case, the two TCs should be well able to collaborate around an agenda of gfundamental soil behaviourh.

 

4.  This led to a discussion on how to structure the agenda of the existing gcrushability grouph, from which TC35 has sprung, in planning future meetings. It was felt to be inadequate to base our reports on crushable soil types, and necessary to widen our scope in light of our new terms of reference. A hierarchy of more general scientific objectives was preferred, rather as indicated below.

 

Micro-Geomechanics: the scientific agenda

Properties of grains (grain size and shape, crushing stress)

Properties of a granular aggregate (specific surface, fabric, anisotropy)

Imaging of micro-structure (evolution under load, source of macroscopic strain)

Data of element tests (permeability, wave velocity, compressibility, plastic flow, strength)

Linking micro  and macro  parameters  (physical, statistical)

Micro-mechanical simulations (DEM)

Constitutive continuum models based on micro-mechanisms (dissipation, localisation)

 

The unique contributions of TC35 members, and the objectives at our meetings, would be to use observations in the upper levels of the hierarchy to throw light on the selection of appropriate soil tests, models and engineering parameters in the deeper levels of the hierarchy. Our aim should be to contribute to the discussion of gsoil constitutive modellingh from a completely fresh perspective.

 

5. Although the approach set out above has some advantages from the point of view of structuring a scientific effort, it has the disadvantage of using abstract language which distances itself from the everyday concerns of practising engineers, and from the funding objectives of companies and research councils. A prolonged discussion took place on how best to make appropriate alliances with greal-worldh organisations so that scientific advances could be funded, and so that the practical benefits of the micro-geomechanical approach could be demonstrated.

 

The brain-storming session resulted in the following list of possible applications which we recommend for further evaluation and exploitation in certain application-groups which we imagine will form from within the larger TC35 membership. Any particular member may wish to join one or more application-groups, and to contribute web pages which could be used by colleagues to assist their individual or collective approach to companies, research councils or government agencies. It should be of great advantage to each of us to be open and informative with each other, so that when we make research proposals we can gain from being able to quote

·      our membership of an international organisation

·      links with cognate research projects abroad

·     background references, micrographs, data etc to support our case.
Micro-Geomechanics:  applications in construction and the environment

 

Construction companies – minimisation of construction costs

Excavation – boring, tunnelling, water-jetting – disaggregation

Spoil handling – chemical and mechanical modification – plasticity

Pile driving – hammering, vibration, pressing-in – compressibility

Stabilisation – dynamic / vibratory compaction, stone /soil-cement columns – compaction

Grouting – compaction, hydro-fracture, intrusion – fracture, intrusion

Pipelines – laying, ploughing, burial – heterogeneity, true cohesion

 

Transport and planning authorities – minimisation of whole life cost

Road and rail beds – aggregate degradation, rutting, choking of drains – crushing

Ports and rivers – dredging – cutting

Land reclamation – compression of macro-voids, effects of heterogeneity

Brownfield sites – remediation, contaminant transport – permeability, attenuation

      

Minerals and processing companies – control of degradation

            Quarrying, processing and transport of granular materials – crushing

 

Environment agencies –  waste minimisation and re-use

Use of PFA, mine-waste, and demolition rubble – compaction, compressibility, aging

 

Construction companies – specification for heterogeneous soil and rock fills

            Sampling, testing and simulation – dilation, friction and compressibility

 

Design agencies – control of brittle, sensitive or collapsible geo-materials

            Carbonate, tropical, residual, cemented, frozen soils – structure, fracture

 

Design authorities – earthquake hazard mitigation

Liquefiable sands – characterisation

 

Heritage agencies – preservation of buried artefacts

       Past and future disturbance of archaeological remains – artefact/soil interaction

 

Petroleum engineering – enhancement of recovery

       Maintaining / enhancing hydraulic conductivity – hydraulic fracture, compaction

 

 

It is suggested that we circulate this to all members, expanding or revising it as desired. TC35 members wishing to form application-groups to exploit any of these possible practical research topics could in the first instance contact Malcolm Bolton, who would then be able to put them in contact with each other.


6.  Future meetings of TC35, or organised partly by TC35 members and approved by TC35 as an official symposium / workshop etc may include the following working suggestions.

 

December 2000?              Cambridge            Informal workshop on Micro-geomechanics

To be organised by MB with the objective of assembling the UK gteamh and stimulating activity

 

Date to be fixed in 2001?            Yamaguchi University            Symposium on crushable soils

To be organised by MH, as part of the activities of the regional association of JSSMGE.

 

24/25 August 2001?              Turkey             Satellite Conference on Fundamental Soil Behaviour

To be organised by Malcolm Bolton in conjunction with the first formal TC35 meeting, and to include TC34/35 contributions and a presentation invited from Prof Oda on the outcome of his previous committeefs work.

 

The practical constraints may force changes to these tentative plans.

 

7.  The following actions were agreed that:

·        MB should circulate these minutes for information.

·        MB and MH should then progress the meetings referred to in 6 above;

·        MB should encourage activity by writing to all members and include relevant extracts of these minutes together with a request to organise other regional meetings as appropriate;

·        AH should contact Hackmet Joer to consider how to develop appropriate web pages.

·        MB should complete the written version of his lecture to IWSC 1999, before the end of August so that YN has time to organise publication of the corresponding book prior to his departure for Cambridge at the end of  September.

 

8.  These unconfirmed minutes have been written by Malcolm Bolton.

 

Please suggest improvements!