How often do you see news about a structural collapse or massive landslide occurring somewhere in the world? What happens after such an event occurs? Once the situation is stabilized, a selected group of experts may be brought to the site to conduct an investigation and provide opinions on possible causes of failure.
Forensic engineering is the engineering practice which determines the likely cause(s) of the failure of structures. Merriam-Webster dictionary defines a failure as an unforeseen and unplanned event or circumstance. In geotechnical engineering, failures can be related to man-made structures or natural formations. Such failures can result in significant losses that may include environmental damages, economic losses, and societal impacts, among others.
What is it like working on a forensic engineering project? It feels like solving a mystery. It starts with brainstorming about potential causative factors and continues to comprehensive analyses of each contributing mechanism to establish the likely root cause of the failure. Forensic engineers have to rely on available data, new data gathered in the investigation, their background knowledge and experience, as well as industry practices and applicable standards and codes. Often, they have to devise innovative ways to process data or to acquire new information.
By studying failures, geotechnical engineers improve their practices and analysis methodologies. Multiple failures have contributed to such improvements. In 2004, the metro tunnel along Nicoll Highway in Singapore failed. The nature of this failure illustrated the need to use representative soil properties in numerical analysis and to property update analysis based on field observations. The Vajont Dam overtopping in 1963 in Italy was one of the key failures showing the importance of conspiring pore pressures in landslide triggering, and the need for a thorough geotechnical investigation to locate any potential weak failure planes. The landslide that occurred east of Oso, Washington in 2014 showed the importance of a detailed study of site history and monitoring of field condition changes.
Historic records show that dam failures occur somewhat frequently in the US. There has been an average of 10 dam failures per year since the mid-nineteenth century, many of which are small failures with limited impact to the downstream area. However, some of the largest disasters in the US like South Fork Dam in Pennsylvania (1889), St. Francis Dam Failure in California (1928) and Buffalo Creek dam failure in 1972 each took lives of hundreds of people. Through extensive review of case studies, geotechnical engineers determined that the most frequent causes of dam failures are overtopping and seepage related causes.
Experts in the forensic geotechnical engineering field use advanced geotechnical exploration, laboratory studies, instrumentation and monitoring, and advanced analyses using digital models to understand the sequence of events leading to failure. The conclusions of the investigation are usually summarized in forensic engineering reports, which may include recommendations for remedial measures. Many reports of forensic investigations have become publicly available, and the lessons learned have been very useful to improve design methodologies, construction means and methods, and rules and regulations.
For example, the now famous case of failed apartment buildings after the Niigata earthquake in Japan in 1964 triggered much focus on geotechnical earthquake engineering. As a result, we now have much more robust methodologies to design against earthquake induced liquefaction. The Oroville spillway dam failure in 2017, triggered substantial discussion on spillway design and general industry practices in the Unites States. California state implemented new laws and regulations for classification of hazard potential of dams and emergency preparedness, which were adopted by the end of the same year.
Source: https://damfailures.org/case-study/oroville-dam-california-2017/
What makes forensic geotechnical engineering unique? It is the variety of technical issues that occur under different conditions all over the world. Forensic analyses oftentimes need state-of-the-art methodologies. This is one of the reasons they can push the envelope in improving our current standards. Forensic engineers allow us to gather and share knowledge about reasons of failures and appropriate remedial measures. With the advances in science and technology and utilizing lessons learned from past performances engineers can update standards of practice and be better prepared to face challenges of the future.
Anna Suprunenko earned her Master of Science Degree in Geotechnical Engineering from the University of New Hampshire. She has over six years of experience in slope stability and settlement analysis, interpretation of in-situ measurements, geotechnical and geophysical field testing, foundation design and advanced laboratory testing.She volunteers for the MATHCOUNTS school competition and Mass STEM Hub program to promote engineering as a field of study and profession among middle school students. She also gives back to her profession by serving on STEM Outreach Task force of ACEC-MA.
References:
Delatte, Norbert J., “Beyond Failure: Forensic Case Studies for Civil Engineers” (2009). Civil and Environmental Engineering Department Books.