ABSTRACT
This paper presents engineering experiences with limestone problems in Berks County, Pennsylvania. Berks County is located in the Great Valley section of the Valley and Ridge Province of the Appalachian Mountains. Considerable areas of Berks County, covering the City of Reading and its suburbs, are underlain by limestone of Cambrian and Ordovician Ages. Numerous industries of various sizes, including Carpenter Technology, AT&T, Dana Corporation, Vanity Fair Corporation, Rockwell International Corporation and Meridian Bank, are located in Reading. With all these industries, Berks County has remained a rural agricultural area, but in recent years numerous housing developments, industrial complexes (warehouses and office buildings), and shopping centers were constructed. This heavy construction required the developers, contractors, and engineers to address the sinkhole potential within limestone/karst areas and its effect on their structures. Engineers are required to estimate allowable bearing pressures and settlements using classical soil mechanics principles, to evaluate the sinkhole potential at particular sites, and to assist the contractors to develop proper construction procedures which will avoid creating situations that augment possible sinkhole occurrences.
Evaluation of sinkhole potential in an area requires careful field and office investigations. Rational investigative procedures with properly implemented grading and drainage systems, including stormwater detention basins designed for proper hydraulics, consistent with the site geological conditions, reduce the occurrence of sinkholes. The implementation of a proper drainage system and maintaining a well graded site, both during and after construction, are the best preventive measures against sinkhole occurrences. Foundation types, generally used, and economically feasible, will be discussed. Both shallow and deep foundations are used in limestone areas; sometimes ground improvements are implemented before foundations are constructed.
