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 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.