Abstract The Pittsburgh region has long been recognized as one of major landslide activity. This results from the geology and geomorphic processes shaping the region. The underlying bedrock of flat-lying interbedded strong and weak sedimentary strata has been acted upon by erosion, stress relief, and mass wasting, including creep and landsliding processes, to produce masses of marginally stable colluvial rock and soil on many of the steep hillsides common to the region. Landsliding often involves re-activation of such rock and soil masses. Recent landsliding is often triggered by heavy precipitation and by human activities, i.e., slope excavation, fill placement, and changes in long-established patterns of surface and subsurface drainage. This field trip has four stops, all within 20 mi of downtown Pittsburgh. Each stop is along a transportation corridor (railroad, local road, and two along an interstate highway). Each stop has various sized examples of the types of landslides common to the region. Most of these examples involve reactivation of unrecognized colluvial landslide masses.

Abstract The Pittsburgh region has long been recognized as one of major landslide activity. This results from the geology and geomorphic processes shaping the region. The underlying bedrock of flat-lying interbedded strong and weak sedimentary strata has been acted upon by erosion, stress relief, and mass wasting, including creep and landsliding processes, to produce masses of marginally stable colluvial rock and soil on many of the steep hillsides common to the region. Landsliding often involves re-activation of such rock and soil masses. Recent landsliding is often triggered by heavy precipitation and by human activities, i.e., slope excavation, fill placement, and changes in long-established patterns of surface and subsurface drainage. This field trip has four stops, all within 20 mi of downtown Pittsburgh. Each stop is along a transportation corridor (railroad, local road, and two along an interstate highway). Each stop has various sized examples of the types of landslides common to the region. Most of these examples involve reactivation of unrecognized colluvial landslide masses.

Abstract Coal mining probably results in a greater disturbance to the geologic conditions of an area than any other form of mining. This is due primarily to the nature of the coal deposits, which are commonly extensive, covering large areas and consisting of multiple seams extending over significant vertical intervals. Surface mining results in the disturbance of the ground surface and shallow subsurface materials over large areas. Reclamation of these mines generally results in subdued versions of the original landforms, rerouted drainage systems, and disrupted subsurface materials. Underground mines may be far more extensive, creating nearly continuous subsurface workings, which may result in postmining effects such as subsidence, mine pools, mine fires, and the accumulation of gases. Both mining types also affect surface and underground water, generally resulting in the deterioration of water quality and often capturing surface flow and changing, at least temporarily, groundwater levels. The following description concerns coal mining in the conterminous United States, although the changes in geologic conditions could be applicable in any coal mining region in the world.

Abstract Today, engineering geologists in private industry occupy key positions in the planning, design, and construction of many different kinds of engineering works. Since the beginning of this century, it typically has been the practice of engineering-construction companies to rely on outside consultants for projects requiring geological expertise. However, with the end of World War II and the rapid development of the early 1950s, engineering-construction companies in North America began to hire geologists as staff members. A recent survey of the older major engineering-construction companies by Bechtel (1986) established that about half of the firms support engineering geology staffs in-house, while half rely solely on consultants, either individuals or specialty groups. Furthermore, many of the companies that retain engineering geologists in-house occasionally supplement their staff input with the services of outside consultants for a variety of reasons, including fulfilling contractual obligations, enhancing the work capabilities in a specific geographic area, or reinforcing expert opinions in controversial situations. Today, some of the major engineering-construction companies that support their own in-house geoscience experts include Bechtel Civil, Inc.; EBASCO Services, Inc.; Fluor Engineers, Inc.; Harza Engineering Company; Morrison-Knudsen Engineering Company; United Engineers and Constructors; and Stone and Webster Engineering Corporation. Bechtel was one of the first engineering companies to hire staff geologists. In the early 1950s, they hired Ben Warner, Victor L. Wright, Robert J. Farina, and Charles P. Benziger to work on a project-by-product basis. However, lack of permanent job status and associated benefits, as well as the inability in those days to advance professionally within the company ranks, was not encouraging to the geologists or beneficial to the company, and consequently, many of these geologists moved on to other professional situations.

Abstract Underground coal mining has occurred beneath eight million acres of land in the United States, two million acres of which have been affected by subsidence. Most of this mining has taken place in the eastern half of the United States (east of the 100th meridian) where thousands of acres in urban areas are threatened by subsidence. Early mining was not as efficient as today. Unrecovered coal pillars, often of variable size and spacing, remain to support the overlying strata for an indefinite period of time after mining has ceased. Roof collapse, crushing of pillars, or punching of pillars into the floor is now resulting in sinkhole or trough subsidence tens or even hundreds of years after mining. In areas of active mining, where nominal total extraction is practiced, subsidence is essentially contemporaneous with mining. Limited observational data on ground movements over total extraction mines–room and pillar and longwall–suggest subsidence over deep longwall mines in Europe is similar in general respects, but different in detail, to subsidence in the United States. Ground deformations resulting from subsidence have often been assumed to cause damage to structures in terms of simple tension and compression transferred by friction and adhesion to the undersides of foundations. Differential settlement, intensified pressure on subgrade walls, and other modes of soil-structure interaction are of equal significance in the eastern United States.