Orange County Branch Newsletter

August 2014

Sustainability Committee

Geotechnical Sustainability


By: Jerry Diaz, PE, GE, Principal Diaz Yourman & Associates, Geotechnical Engineers

In February, 2014 the Sustainability Committee sponsored a student workshop to discuss Sustainability in Civil Engineering. I was fortunate to participate to give a geotechnical perspective.

Geotechnical considerations are significant parts of any project and can play a major role in a project’s sustainability.  We must develop a culture of sustainability in everything we do.  We can contribute a lot to sustainability by keeping our eyes open to the vast opportunities that civil/geotechnical engineers have to enhance sustainability at any stage of a project; planning, design, construction, operations and maintenance.

Looking primarily from the perspective of geotechnical engineering, sample opportunities to enhance sustainability at each stage were discussed:

Planning

Thorough geologic mapping during the planning phase enables planners to avoid   geologic hazards such as faulting, seepage, and potentially unstable areas. Preliminary geotechnical investigations and mapping can help identify the relative favorability of areas for leach fields, foundation conditions and borrow sources.  This approach was used in the initial planning and continued implementation for the Sea Ranch, a ten mile long project along the Sonoma coast, creating an environmentally attractive development with minimum grading and habitat disturbance. (Figure)

Design/ Resource Conservation (Reduce, Reuse, Recycle)

Foundation requirements can be significantly reduced by the various types of ground improvement. Ground improvement not only reduces foundation requirements for support it also improve resilience by mitigating potential earthquake damage due to liquefaction and seismic settlement.

Use natural processes to reduce engineering demands.  Wave erosion undermined the rock rip-rap slope protection for a playground fill along San Francisco bay.  Rather than designing a more robust and massive rock slope protection section, wave energy was dissipated by planting native Bay Mud vegetation in front of the slope. (Figure)

Construction

Sustainability can be improved by selection of foundation construction method.  The use of auger cast displacement piles; improves the surrounding ground by densification thus increasing the unit skin friction carrying capacity, and returns little or no spoils to the surface nearly eliminating disposal requirements. (figure)

Future

Geothermal heat transfer for heating and cooling has been in use for some time. Research and pilot projects are now being conducted to study the effectiveness and consequences of incorporating heat transfer elements into foundations and structures. It is projected that such systems could produce buildings with near net zero external energy demands for heating and cooling.  

Besides the now conventional methods of ground improvement such as stone columns and grouting, research work is now on-going in the fields of bio-chemical geotechnical engineering.  One of the aims is to achieve ground improvement through in situ bio-chemical processes, such as through enhancing the environment for the beneficial organisms.  Researchers have commented something like -- “someday we might grow a foundation”, and “the holy grail would be to mitigate liquefaction potential beneath an existing building”.

Sustainable development must be affordable now and in the future. Resilience and redundancy are critical for future affordability, particularly in the event of major emergencies such as earthquake or flood.  While vast amounts are routinely funded and spent to rebuild after major emergencies, spending for resilience and redundancy is a tough sell in the planning and design stages, but must be a major focus in our professional recommendations. 

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