The Big Picture

6.1.1 How Do Geotechnical Engineers Miss the Big Picture?

About three years ago I was involved in a post mortem geotechnical investigation of extensive soil damage to a large expensive home, see Section 1.3, Figures 1.3.1 and 1.3.2. During my first visit to the site, I followed the Terzaghi Method and explored the geology of the area around the home. My first pass involved walking a 1500-foot radius circle around the damaged home. From the vantage point of distance, I noticed that the site had steeply dipping bedrock with alternating bands of sandstone and expansive clay shale crossing beneath the home site. This situation set the home up for differential foundation support conditions. Reviewing the geotechnical report provided for this home, I saw evidence that they did not identify the differential support conditions, nor did they identify the presence of expansive clay shales. My question is: why did the geotechnical engineers miss an obvious geologic condition? During a lunch meeting with our semi-retired, senior geologist, Mr. Jerry Lindsey, I asked him to consider his 60+ years of experience in the geo-industry and write down his “explanation” for why geotechnical engineers often miss obvious geologic hazards. The following material with some of my editing is Jerry's answer.

6.1.2 The Big Picture – What a Soils Engineer Should Know about the Geologic Setting before Going to the Job Site

Geotechnical engineers should keep in mind that the “geo” in geotechnical ...

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