What’s Wrong with Commodity Geotechnical Reports

FHWA NHI-01-031 NHI Course No. 132031
Subsurface Investigations— Geotechnical Site Characterization, May 2002

A couple of weeks ago, I was using a geotechnical report to develop a critical parameter for design of a particular foundation system. Like so many geotechnical reports I see, this report had many of the signs of being the product of commodity geotechnical services, as is often practiced when materials testing agencies offer geotechnical engineering. When geotechnical services are provided at the lowest possible cost, the effort to perform a subsurface exploration and provide a report must be reduced to the minimum, using the lowest-cost staff available. There is no budget for detailed analysis of data or development of site-specific recommendations by senior staff. The report is similar as to form as those provided a higher cost, but the substance and the level of service that produced it are not the same.

Interestingly, the services and reports provided by commodity geotechnical firms have a lot of the same short-comings. Perhaps this should not come as a surprise. To be competitive, these firms will have to use a lot of the same means to reduce the price of their services as similarly situated firms. This price competition on increasingly similar products and services is the essence of commoditization. Reaching the end of the process is to be a true commodity and be indistinguishable, except on price. While commodity geotechnical services are less expensive, they often increase cost overall by incentivizing excessive conservatism in design, leading to higher cost of construction and also by increasing uncertainty during construction, leading to higher risk of claims and delays.

Having had a lot of experience reading and using geotechnical reports, as well as experience producing them, the signs of commodity geotechnical services are quickly recognizable to me. They reflect a lack of thought and attention to detail in scoping the subsurface exploration, collection and presentation of data and development of recommendations. Here are a few common problems: Continue reading

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Delaware Earthquake or Earthquakes Can Happen Anywhere

As reported by the United States Geological Survey and various news organizations, a magnitude 4.1 earthquake occurred outside Dover Delaware on November 30, subjecting much of the mid-Atlantic region to weak to light shaking. Assuming the magnitude is not revised down, it would be tied for the largest magnitude earthquake in Delaware history. No damage or injuries have been reported as of this writing.

For anyone who thinks that it is “common sense” that earthquakes cannot happen in their area, this should serve as a reminder: earthquakes can happen anywhere.  In the Central and Eastern United States (CEUS), earthquakes are not directly caused by plate tectonic activity, and are, consequently, more infrequent and harder to predict.  However, much of the CEUS is subject the moderate earthquake hazards and a few locations are subject to high hazards. Take a look at the hazard map below produced by USGS.  Continue reading

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Should Temporary Structures be Designed with Higher Allowable Stresses?

Traditionally, designers of temporary structures for use in construction had little guidance binding on their designs. Some owners, particularly infrastructure operators, provided standards and guidelines that permitted increased allowable stresses for certain temporary conditions. Sometimes the increased allowable stresses were limited to new materials or were subject to other stipulations. However, this practice came from a time when codes were much simpler and, in some respects, more conservative than they are now. Should increased allowable stresses still be used in the design of temporary structures, or is this practice anachronistic?

The answer is not simple and depends on who you ask. Different professional approach temporary works in very different ways. Structural Engineers are typically squeamish about construction means and methods and are often very conservative about soils and other loads commonly supported by temporary structures. Some structural engineers will, incorrectly, claim that a structure has “failed” if the computed factor of safety is below design code values. Geotechnical engineers typically view factors of safety to be a matter of judgment and some deprecate codes and standards and structural design generally. Thus geotechnical engineers will take a more aggressive approach to temporary structures, but may take risks unwittingly, especially when considering elements and systems that are not in contact with soil. Construction engineers are often highly risk-tolerant, but use simple and typically conservative methods for their temporary structures designs. It is hard to find consensus as to design approach, much less a standard of care among such disparate perspectives. Continue reading

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The Lost Art of Foundation Engineering

When I began my career, my first job title was “foundation engineer”. The title was an anachronism, even at the time, but the scope of my work was consistent with the domain of foundation engineer going back to the early 20th century, at least. I was involved in geotechnical subsurface investigation and classification, development of design parameters, structural design of foundation elements, earth-retaining systems and underground structures and construction consideration for these systems. Foundation problems have always been subject to uncertainty due to the inability to specify and fully observe the subsurface conditions. Therefore, foundation engineering has always relied on empiricism and judgment to provide reliable predictions about foundation performance.

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Profile and Practice Overview

Richard J. Driscoll, Consulting Engineer (RJDCE) provides consulting structural and foundation engineering services to owners, design professionals, contractors and other construction project stakeholders in the northeast and mid-Atlantic regions. The practice specializes in managing the technical challenges and risks associated with foundation systems, below-ground structures, existing structures and construction in the urban environment. RJDCE utilizes a broad base of experience and knowledge to assist stakeholders balance performance, cost and risk on projects subject to uncertainty.

For more information, see RJDCE’s new Profile and updated  Practice_Overview.

Richard J. Driscoll, Consulting Engineer - Profile
Profile
Richard J. Driscoll, Consulting Engineer - Practice Overview
Practice Overview

 

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Why Does the Construction Industry Love Silos?

Have you ever noticed how much the construction industry seems to love silos? Not the kind of silos that hold grain and other bulk materials, but metaphorical silos within organizations in which subgroups have different asymmetric information and interests and limited points of communication with each other. The resulting “silo mentality” is a result of poor information sharing and hierarchical communication, specialization and conflicting incentives. This may lead to subgroups working at cross-purposes and counter to the goals of the organization as a whole.

In the construction industry, the organizations are typically ad hoc, assembled for a particular project. The subgroups include the owner, the architect, engineers, the contractor and subcontractors. On simple projects, the hierarchy might be rather flat. An architect and contractor report to the owner, each of who has one tier of subs. However, larger and more complex project may have a few more tiers. For example, the excavation contractor might have a specialty foundation contractor, who might, in turn, have an engineer. A project organization of this complexity is bound to develop a few silos.

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Another Deck Failure…No Injuries, This Time

I often find a lot of owners want to cut corners when constructing or repairing deck structures (decks, porches, balconies, etc.) by neglecting code requirement or working without permits, among other things. They assume that these structures require less care because they are accessory to and thus less important to the building. The reality is that decks are among the most dangerous types of structures in terms of injuries and deaths associated with them.

Photo Credit: DC Fire & EMS (Twitter @dcfireems)

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Obtaining Value Using Consultants on A/E/C Projects

Last week, I made a hastily planned out-of-town trip for a consulting engagement at a client’s office. The client had gathered several engineering and construction practitioners from around the country, along with several of the client’s staff to help them plan a new project. A few of us made brief presentations about our past work as it applied to the problem at hand and the remainder of the work day comprised a series of interesting and wide-ranging discussions of various aspects of the project.

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What Nate Silver Can Teach Engineers

Nate’s Silver’s book, The Signal and the Noise (The Penguin Press, New York, 2012) was released in the run-up to the 2012 election. Silver and FiveThirtyEight.com project were well on their way to accurately predicting most of the electoral college and senate results and there was a good deal of interest and controversy in the political media regarding his work. The book is fundamentally about making predictions in an environment of uncertainty. Silver uses examples from a variety of disciplines including weather, baseball, economics and gambling to illustrate why some predictions fare better than others. However, the lessons can be applied to anyone whose field puts them in the prediction business. And engineers, whether they realize it or not, are in the prediction business. After all, engineering analysis and design of engineered systems require making predictions about the performance of a system, typically with uncertain loads and initial conditions and with the stakes being the health, welfare and safety of the public.

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How to Double Your Foundation’s Bearing Capacity

A few days ago, I saw a brief case study from a foundation contractor’s who had installed a proprietary pile system for a building in Northwest Washington, DC. Being somewhat familiar with the subsurface conditions and typical building heights in the area, I immediately doubted whether a deep foundation system was necessary. You will have to forgive my skepticism about this sort of thing; I have seen it a lot, and it seems to be getting more prevalent.

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