A number of technical and professional factors motivated organization of this workshop.  The motivations listed below are far from inclusive and only present initial ideas by the organizers prior to the workshop (which were greatly expanded by the workshop).

The harnessing and use of biological processes in engineering have significantly advanced society.

Society has directly benefited from research advances in which biological processes were instrumental in providing viable solutions to long-standing engineering problems.  New solutions have provided more efficient, environmentally friendly, and/or economic solutions relative to traditional treatments that utilize man-made materials.  An example of this is Microbial Enhanced Oil Recovery (MEOR), where microbial activity has been used to either mobilize adsorbed oils or to plug large pore spaces via calcite cementation, which in turn enables additional production of oil from a well before abandoning it.  Other examples include the stabilization of metals including radioactive wastes, development of biological shields for zonal remediation of hazardous wastes or reactive landfill liners, environmental stabilization of contaminated soils, encapsulation of hazardous, reactive materials, and other contaminants in natural soils and acid mine tailings.  However, the changes that occur in soils from the geotechnical aspect are often not investigated due to the focus on environmental remediation.

Biological processes influence the performance of geotechnical systems.

Natural biological processes have been shown to alter the properties and behavior of both natural soil deposits and of man-made soil deposits created during construction.  One of the most common examples of this is “bio-engineering” techniques that are implemented for near surface stabilization of slopes (Gray and Sotir 1996).  Live vegetative materials, or fascines, are integrated into the slope surface and their natural anchoring systems – roots – provides additional stability, enabling construction at higher slope grades than that possible with conventional construction techniques.  Less widely recognized is the role that biological processes can have in the failure of geotechnical systems.  For example, Mitchell and Santamarina (2005) cited biologic activity as a critical component in the 1984 embankment failure of Carsington Dam in Derbyshire, England, and in the long term stability of a high rock pile near an open pit mine in northern New Mexico. 

Geotechnical processes influence natural biological processes.

Largely unrecognized by geotechnical engineers is the influence geotechnical construction processes can have on biological processes.  For example, soil compression during agricultural treatment (compaction by a smooth drum roller in geotechnical terminology) initiates a fundamental shift in biological processes (from aerobic to anaerobic metabolism), which creates conditions harmful to plant roots and an environment that is conducive to the release of greenhouse gasses (Flynn et al., 2005).  Soil compression (due to mechanical compaction) also alters the balance between water stress and mechanical impedance that roots experience, affecting plant growth. 

Understanding of nature has matured to where these biological processes can be controlled.

The biological sciences have advanced well beyond on the age of observation.  Today many biological processes have been characterized and understood to a degree that the process can be controlled.  Some examples include the microbial degradation of organic matter in waste waters, the use of microorganisms in the bioremediation of hazardous substances in groundwater, soils, and air, creation of bioreactors, microbial activity controlling agricultural and food production, etc.

There is potential to replace manufactured materials used in many geosystems with natural treatment processes that will provide economic and environmental benefits.

In recent decades the frequency and volume of manufactured materials, such as geosynthetics and grouts, introduced into the subsurface as part of geotechnical systems has increased dramatically.  The addition of these materials, while beneficial from an engineering performance perspective, might not necessarily be advantageous for the environment.  For example, materials for grouting, which can create artificially high in situ pH levels, have in some cases contaminated the subsurface and lead to toxic conditions.  Examples of this include paralysis of cows in Sweden, contamination of groundwater in France resulting human death, and threatening of aquatic fish habitat in the Sacramento River.  Alternative, natural biologically – based treatment methods could meet the same engineering requirements without environmental concerns.

A workshop for scientists and engineers from different disciplines provides an opportunity to stimulate new understanding.

The role of biological processes in the engineering behavior of soils, and vice-versa, are inherently interdisciplinary questions.  If experts remain within the confines of their traditional disciplines and do not engage beyond their discipline minimal progress can be made in exploring and developing this field.  A forum such as a workshop that brings these people together has the strong potential to stimulate new understanding of old problems as well as new discoveries.  For example, the embankment failure of Carsington Dam (cited above) was unexplainable considering only geotechnical aspects, but can be explained when biological processes are also considered.  Similarly, soil scientists hypothesize that the surfactants that roots produce alter rates of soil water uptake, but without geotechnical understanding they have not been able to quantify if this is indeed the case and whether it affects soil strength.  Furthermore, exposure to other disciplines will also expose experts to the research and analysis tools in other fields that may be useful for their research. 

Biological Processes in Geotechnical Engineering is a “high priority” for the National Academy of Sciences.

In the 2006 report from the National Academy of Sciences entitled “Geological and Geotechnical Engineering in the New Millennium: Opportunities for Research and Technological Innovation” the role of biological processes in geotechnical engineering will be cited as a critical research thrust and opportunity for the future (National Research Council (2006).  The recognition of the role of biological processes has also been recently highlighted in the ASCE G-I GeoStrata (2005) magazine, which dedicated the September/October 2005 issue to “Bio-Geo: In-situ Processes”. 

Recent research studies demonstrate the role of biological activity in geosystem performance and the ability to modify soil properties with biological processes.

The emerging importance of the role of biological process in geotechnical engineering has been highlighted by a recent ASCE journal paper by Mitchell and Santamarina (2005) in which the authors establish a foundation for this new area.  They sequentially define and describe “biological constituents, characteristics, and processes within a soil”, provide “examples of how microbiological conditions and processes may influence engineering properties and behavior of earth materials”, review “geomicrobiological processes that appear particularly promising for further study”, and identify “relevant references to aid in obtaining in-depth background and understanding of many of the points”.  The recent publication of a paper such as this (with basic definitions) emphasizes the infancy of this field and simultaneously highlights the increasing recognition of the importance of this emerging field.

Recent laboratory studies by interdisciplinary groups have demonstrated that biological processes can be harnessed and used to modify the behavior of soil.  DeJong et al. (2006), using the microorganism Bacillus pasteurii, successfully cemented a loose sand specimen with calcite (Figure 1a).  Testing of the specimens revealed that the strength of the soil had been substantially improved and that specimen collapse under shear was prevented (Figure 1b).  Banagan et al. (2005) explored the improvement of soil properties using bio-films, observing and increase in strength and a decrease in permeability.

Figure 1a: SEM image of microbially induced calcite cementation by Bacillus pasteurii Figure 1b: Improved shear response of biologically treated sand

The harnessing and use of biological processes in engineering have significantly advanced society. 

Research advances that have used biological processes have provided solutions to engineering problems that have improved society.  New solutions have provided more efficient, environmentally friendly, and/or economic solutions relative to traditional treatments that utilize man-made materials.  An example of this is Microbial Enhanced Oil Recovery (MEOR), where microbial activity has been used to either mobilise adsorbed oils or to plug large pore spaces via calcite cementation, which in turn enable additional production of oil from a well before abandoning it.  Other examples of how biological process can alter environmental materials to a degree significant for engineering applications are the stabilisation of metals including radioactive wastes, development of biological shields for zonal remediation of hazardous wastes or reactive landfill liners, environmental stabilisation of contaminated soils, encapsulation of hazardous, reactive materials, and other contaminants in natural soils and acid mine tailings.  However, the changes that occur in soils from the geotechnical aspect are often not investigated due to the focus on environmental remediation.

References

Banagan, B.L.*, Wertheim, B.M.*, Roth, M.J.S., and Caslake, L.F. Increasing Sand Strength Through the Addition of Bacteria.  Poster Presentation at the 105th General Meeting of the American Society for Microbiology, Atlanta GA, June 2005.

DeJong, J.T., Fritzges, M.B., and Nusslein, K. (2006) “Microbially Induced Cementation to Control Sand Response to Undrained Shear”.

Mitchell, J.K. and Santamarina, J.C. (2005) “Biological Considerations in Geotechnical Engineering”, ASCE Journal of Geotechnical and Geoenvironmental Engineering, Vol. 131, No. 19, pp. 1222-1233.

National Research Council (NRC) (2006) Geological and Geotechnical Engineering in the New Millennium:  Opportunities for Research and Technological Innovation, Committee on Geological and Geotechnical Engineering in the New Millennium;  Opportunities for Research and Technological Innovation, Committee on Geological and Geotechnical Engineering, ISBN: 0-309-65331-2, 222 pages.