Journal of Performance of Constructed Facilities

This paper will focus on the legal liability issues facing the professional engineer engaged in the design and construction administration of facilities built on expansive soils. These legal liability issues will be discussed from the perspectives of the geotechnical, civil, and structural engineer to alert those professionals to the legal ramifications of their daily activities. By focusing on these legal aspects facing the engineers that are involved in the process of building on expansive soils, hopefully litigation can be avoided or successfully defended. Attention to the legal ramifications of engineering is mandated by today’s litigious environment in the construction industry, especially when designing and administering the construction of facilities built on expansive soils.

Field measurements of foundation movements in central Mississippi have revealed design issues involving expansive soils. At one building, field measurements of the first floor slab at 14 locations show that heaving occurred at a steady rate during part of an extensive drought. The steady rate was maintained throughout the final 21.5 months of a 23.5-month study period following a record drought that occurred at the beginning of the study. The average change in the movement rate was 2.9 mm (0.11 in.) per year over the last 21.5 months. Median movement rates for all the pins varied from 25 mm (0.98 in.) per year to 1.8 mm (0.07 in.) per year excluding the measurements made during the first part of the drought. Elevation surveys at another facility show how the rate of heave is influenced by geologic variations. These surveys also show how the depth of clay (from the surface) influenced heave and how differential movements of a structure are produced from these variations in geology. Design procedures for kind of movement are discussed.

The San Francisco Bay Area, California has experienced significant population growth over the last 60 years. The design practices for residential foundations have evolved substantially over this period, as a result of improved geologic characterizations, better engineering understandings of foundation performance, building code changes, and project litigation. The majority of residential foundations are constructed on expansive soils and bedrock, with the primary movement as a result of swell due to wetting of materials in an arid environment. A survey of design practice of practicing geotechnical engineers in the bay area was conducted using a written questionnaire and telephone interviews to compile data regarding the most commonly used design procedures, design details, drainage recommendations, and construction monitoring practices. The results of this survey are compiled and presented in this paper. Three primary foundation systems were identified in the survey as being commonly used in the bay area—rigid footing grids, drilled piers, and mats/slabs. To illustrate problems that have occurred with each of these foundation systems, case histories are presented for recent bay area expansive soil projects for each of these three foundation types.

Construction on expansive soils is challenging and thus prone to some problems and litigation. The engineering community makes extensive use of local experience and empirical procedures to address these problems. Although there has been extensive study of expansive soils and foundations on expansive soils, data related to performance of residential structures are limited in general and limited in the Phoenix area, in particular. In this study, an overview of the Phoenix Valley, Arizona, geotechnical practice and foundation performance related to residential structures on expansive clays, was developed through surveys and interviews with geotechnical engineers, structural engineers, and homebuilders. Using data obtained from files of Phoenix area geotechnical firms and government agencies, the existing Natural Resource Conservation Service map showing expansive soil locations throughout the Phoenix region was updated through the use of correlation developed in this study relating expansion index to common soil index properties such as Atterberg limits and percent passing the No. 200 sieve. Files of forensic investigations linked to expansive soil regions were made available for this study by several geotechnical engineering firms, and Phoenix Valley areas where forensic investigations have been identified, were mapped for comparison to regions identified in the updated map as having expansive soils. Comparison of the forensic investigation map to the updated map of expansive clay locations revealed that most of the forensic investigations were in regions identified with clays labeled as high to moderately high expansion potential, with a few forensic investigations in regions of medium expansion potential. Finally, unsaturated flow analyses were conducted for an Arizona expansive clay profile for two very different landscaped conditions of well-irrigated turf and desert landscape. The results of the numerical analyses were consistent with the reported observations and modes of failure identified through the surveys and interviews conducted with engineering and homebuilder professionals, including the finding that site drainage was found to be extremely important to good foundation performance, regardless of the type of landscape selected.

Construction of buildings using a slab on grade and belled drilled piers to support column loads in central Mississippi has performed poorly. Similar buildings where the first floor was poured on 15.2 cm (6 in.) cardboard box forms have not fared much better. The first floor of this building was a slab on grade that was dowelled to a grid of grade beams. The grade beams were dowelled to drilled piers. The top of the expansive Yazoo clay varied from 1.8 to 3.66 m (5.9–12 ft) deep. High swell pressures developed under the slab and began to lift the building. A frame analysis showed that foundation movements were significantly changing the stresses of the structural steel frame. About half of the drilled piers of the building were found to be damaged near the connection with the grade beam. Two piers had separations of 10.2 and 8.9 cm (4 and 3.5 in.). During the foundation repair, the building frame was releveled and eight damaged piers were replaced. Recommendations to reduce the risk of this kind of damage were made.

Eudora Welty house was built in the Belhaven District in Jackson Mississippi in 1925. The foundation rests on a surficial nonexpansive 1.5 m (5 ft) clay subgrade overlying highly expansive clays, locally known as Yazoo clay. The house has undergone extensive foundation movement and foundation repairs were made in 1979 and in 2002. Foundation repairs for a portion of Miss Welty’s house were first commissioned in 1979 directly by the renowned and widely acclaimed 1973 Pulitzer winning author. Later, after her passing in 2001, the State of Mississippi, to whom the house had been transferred, and the Eudora Welty Foundation commissioned the restoration of the house. The restoration included extensive foundation repairs. Robert Ewing had the distinct honor and pleasure of meeting with Miss Welty in 1979, and upon her request, of designing and implementing foundation repairs for the rear of the house. The underpinning work performed by Ewing in 1979 and that designed by him in 2002 are described. Fifty drilled piers and more than 100 jacks were used in the underpinning and final restoration of the house. The Eudora Welty House was first declared a Mississippi Landmark by the State. In 2005 the Eudora Welty house was placed on the National Register of Historic Places. Because of Miss Welty’s influence on our national literary heritage and because she did all the writing from her upstairs bedroom, her house was designated to be a National Historic Landmark.

This paper examines the background, history, and results of multiple investigations associated with pyrite-based expansive soils spanning almost 40 years in conjunction with a private elementary school located in western Pennsylvania. The school was initially designed in 1960. Original construction was completed in September 1961 and the first signs of distress, which were primarily related to slab heave, were reported in early 1962. One wing of the school, a 1965 classroom addition (1965 addition) with different structural and foundation systems, did not experience any expansive soil-related damages and served as a valuable comparison throughout multiple subsequent investigations. Pyritic soil material in the subgrade in conjunction with oxygen-rich groundwater was determined to be the cause of soil movement and building distress. Expansive soil-related problems at the school continued for decades despite an investigation, civil court action, and judgment in the late 1960s followed by a remediation program in the 1970s and 1980s. Following a second round of investigations and litigation in the late 1990s, all of the original classroom, office, and gymnasium building sections, with the exception of the 1965 addition, were demolished in late 2000 and early 2001 based on safety concerns and economic evaluation. Investigation and monitoring to confirm subgrade conditions continued throughout the demolition process. As a part of this paper, the history of this case dating back to one of the early identifications of pyrite as an expansive element of concern in building construction, including one of the earliest comprehensive identifications of the complete chemical-microbiological oxidation process is presented. The initial 1960s investigation and conclusions are identified as well as the series of engineering, procedural, and construction errors that took place during and after the first remediation process that led to ongoing soil expansion and structural damage, including misguided actions and misunderstandings that complicated and delayed a final resolution in this case. Today, the industry is more familiar with the potential for pyrite-related construction problems, nevertheless, the paper incorporates lessons learned for avoiding problems and in particular, the procedural failures that led to the eventual need to abandon and demolish the school facility.