New construction projects are rooted in the soil. Construction of projects begins with a foundation. As important as foundations are to a project they are often out of sight and out of mind. When foundation related issues surface they can become serious and costly. In addition to effects on foundations, soils issues can impact the construction process, and threaten projects that rely on retaining walls. What are some geotechnical issues and concerns to keep in mind when planning designing, and constructing a project?
The early stages of planning and design of a construction project include a geotechnical investigation. Based on that investigation a foundation type is selected and designed. The nature and scope of the investigation can vary. When an adequate geotechnical investigation is not performed settlement problems can arise.
Thoughts on geotechnical investigations:
- Skimp on a Geotechnical Report Now, Pay for it Later
- What are the elements of a good, quality geotechnical investigation?
From a professional liability claims experience viewpoint, geotechnical issues were not the most frequent type of issue to come up. This, perhaps, because selective underwriting avoided insuring this kind of risk. But when they did come up, they were often quite costly. Sometimes issues became apparent during construction leading to project delays and cost overruns. The more costly claims involved the need to perform remedial foundation work on completed projects. These varied from the need to make repairs to many residences in a subdivision to the need to strengthen foundations or floor slabs at costly university or commercial buildings. Occasionally the problems arose from manufacturing or warehousing structures that involved unusual floor loads.
The issues could involve project owner decisions to save money on geotechnical investigations by authorizing a less detailed investigation than recommended. Also, failing to recognize the degree to which soil conditions at a proposed construction site can unexpectedly vary, a geotechnical engineer can underestimate the level of detail needed. Are a few borings adequate? Or should many borings be performed? How deep should the borings be? Can information developed for an adjacent site be relied on where there is an expectation of geologic uniformity?
The decisions made as to an appropriate level of geotechnical investigation can be an important element of risk management for a construction project.
One of the frequent construction related issues is who should pay for additional costs due to unanticipated conditions at the construction site. Geotechnical investigation issues arise when unexpected rock has to be removed at additional cost by the contractor or when unexpected groundwater needs to be managed at additional cost to allow construction to proceed.
Both of these can become costly problems that delay the progress of a construction project.
- Denial of Recovery for Unforseen Subsurface Conditions at water main and sewer construction project.
- Unexpected rock at wastewater treatment plant project.
- Unexpected rock at Department of Transportation bridge construction project.
- Construction Dewatering and Groundwater Control.
- Groundwater issues at a wastewater storage and treatment project.
Damage to Adjacent Structures
A different kind of geotechnical investigation and evaluation related problem involves damage to adjacent structures when construction takes place in a built up area. The problems may not necessarily be geotechnical in nature. Protecting the adjacent foundation from damage during excavation is the concern. The distance between the excavation and the nearby foundation combined with soil conditions can become important elements in determining what steps need to be taken to protect that foundation from damage.
- Deformations and damage to buildings adjacent to deep excavations in soft soils
- Business Owners Can File Property Damage Claims Due to Adjacent Construction
- Protecting Adjacent Foundations - the Law
- Overview of Temporary Structures Failures in Construction
Planners, designers, and contractors need to be generally aware of the problem, understand the possible consequences of inadequate investigation and preparation, and explore the options for avoiding damage to adjacent and nearby structures when proceeding with an excavation.
Retaining wall failures may be one of the most frequent kinds of geotechnical related liability issues. Many retaining walls are built to adapt buildings to their natural and often not level surroundings. Failures can be attributed to inadequate anchoring, drainage, or failure to properly address how the soil will load the retaining wall. The consequences of inadequate retaining wall design can range from nuisance to the closing down of an entire shopping center due to soil movement. Litigation is often settled thus avoiding making public the issues that arose in connection with this kind of problem.
- Six Reasons Retaining Walls Fail
- Cause and Origin of Retaining Wall Failure
- Lawsuit Involving Retaining Wall Failure
- Collapsed Retaining Wall Prompts Suit
When structure or site settlement issues arise, one of the issues that frequently comes up is the adequacy of compaction after the soil has been disturbed. The concern is so important that detailed standards, specifications, and testing procedures have been developed. These can become the subject of thorough scrutiny when liability issues arise. Following are sources of further information relevant to soil compaction issues
- Soil Compaction Handbook
- Soil Compaction: Providing a Base for Construction
- Soil: The Other Half of the Foundation
- Project Halted Due to Soil Compaction Problems
Geotechnical issues have been involved in class action lawsuits arising out of home deterioration issues. Entire subdivisions have been built in areas with the expansive soils that cause the problems.
- Damage caused by the destructive shrink-swell cycle of what experts call expansive soils
- Did the Earth Move for You, Too?
- Expansive Soils Destroy Homes in Colorado
- Colorado Class Action Lawsuit
The causes and consequences of retaining wall failures vary. The design of retaining walls needs to take into account knowledge of soil characteristics and structural design principles. All too often retaining walls are constructed by stacking railroad ties or concrete blocks without much consideration of soil and structural science. This can lead to problems.
Where the stakes are higher, as when a costly commercial development is built adjacent to a slope that will need a retaining wall to keep it in place, a more disciplined engineering design is important. Even when soil science and structural design are employed, costly failures can occur. Soil science is not as precise as structural or hydraulic analysis. Interpretations and opinions as to the best solution to a problem can vary. Retaining wall design can be a risky enterprise.
The variable characteristics of soils and performance of designs adapting structures to those characteristics also create problems in the context of construction activity. Unexpected soils conditions can lead to delays and increased costs as well as damage to structures adjacent to the construction. Sometimes the problems caused by variable or inadequately addressed soil conditions do not manifest themselves for a long time as when damaging settlement is detected sometimes years after the project is completed. Geotechnical issues can be regional such as when seismic considerations come into play. Understanding and providing for geotechnical hazards is an important part of any design service or project risk management program.
The objective of this blog is to share information about issues that architects, engineers, and their attorneys encounter. If you have any ideas or suggestions for specific topics to address, or if you would like to contribute an article for publication please let me know at firstname.lastname@example.org.
This article expresses ideas for consideration and should not be taken as recommendations applicable to any specific situation. When making a decision on how to address a specific situation consulting with an experienced attorney is strongly recommended.
© 2017 John Wersyn, All Rights Reserved