ABSTRACT Mount Diablo Coalfield was the largest producer of coal in California from the 1860s to 1906. The now-depleted coalfield is located on the northeast limb of the Mount Diablo anticline. The mineable coal seams occur in the Middle Eocene Domengine Formation, which is predominantly composed of quartz-rich sandstone with several thin coal seams. As many as 26 mine operations were established to mine the coal, and it has been estimated that the total production exceeded 4 million tons. The coal fueled the industrial growth of the major cities of northern California. The mines closed at the turn of the nineteenth century as competition from better coals from Washington Territory and overseas entered the market. After coal mining was abandoned, sand operations were established in the early and mid-twentieth century to mine the silica-rich sandstone. The extraction methods used for sand were underground room-and-pillar mining and surface open-pit mining. The high-quality sand was used widely in the production of pottery and glass, and in foundries. Previous studies have interpreted the environment of deposition of these quartz-rich sandstone and coal deposits as barrier island with tidal channels or delta, tidal shelf, and marsh complexes along a north-south–trending shoreline. However, the excellent exposures in the sand mines display abundant evidence for their deposition in a fluvial/estuarine system. Their regional distribution indicates that they were deposited in a northeast-southwest–trending incised-valley system formed by fluvial incision during a lowstand. The incised valley was filled with fluvial and estuarine deposits made up of quartz-rich sand brought in by streams that flowed westward from the Sierra Nevada.

Abstract One of the geohazards associated with coal mining is subsidence. Coal was originally extracted where it outcropped, then mining became progressively deeper via shallow workings including bell pits, which later developed into room-and-pillar workings. By the middle of the 1900s, coal was mined in larger open pits and underground by longwall mining methods. The mining of coal can often result in the subsidence of the ground surface. Generally, there are two main types of subsidence associated with coal mining. The first is the generation of crown holes caused by the collapse of mine entries and mine roadway intersections and the consolidation of shallow voids. The second is where longwall mining encourages the roof to fail to relieve the strains on the working face and this generates a subsidence trough. The ground movement migrates upwards and outwards from the seam being mined and ultimately causes the subsidence and deformation of the ground surface. Methods are available to predict mining subsidence so that existing or proposed structures and land developments may be safeguarded. Ground investigative methods and geotechnical engineering options are also available for sites that have been or may be adversely affected by coal mining subsidence.

Abstract Old chalk and flint mine workings occur widely across southern and eastern England. Over 3500 mines are recorded in the national Stantec Mining Cavities Database and more are being discovered each year. The oldest flint mines date from the Neolithic period and oldest chalk mines from at least medieval times, possibly Roman times. The most intensive period for mining was during the 1800s, although some mining activities continued into the 1900s. The size, shape and extent of the mines vary considerably with some types only being found in particular areas. They range from crudely excavated bellpits to more extensive pillar-and-stall styles of mining. The mines were created for a series of industrial, building and agricultural purposes. Mining locations were not formally recorded so most are discovered following the collapse of the ground over poorly backfilled shafts and adits. The subsidence activity, often triggered by heavy rainfall or leaking water services, poses a hazard to the built environment and people. Purpose-designed ground investigations are needed to map out the mine workings and carry out follow-on ground stabilization after subsidence events. Where mine workings can be safely entered they can sometimes be stabilized by reinforcement rather than infilling.

Abstract Subsurface coal-mine fires occur in many mining regions, especially where coal has been previously excavated by “room-and-pillar” mining methods. The surface above these fires heats up to produce a thermal anomaly. The shape of the temperature profile over the fire zone holds clues to the depth of the underground fire. We simulated an underground coal-mine fire in the laboratory by burying a hot glass tube in a sandbox. The thermal anomaly over the tube was recorded using a forward looking infrared radiometer (FLIR TM ) camera. Numerical modeling using finite-element techniques for various combinations of tube depth and tube temperature helped to empirically derive a depth-estimation function, called the linear anomaly surface transect (LAST) function. Comparisons of the results from the LAST function with the half-anomaly-width function for depth estimation developed by Panigrahi et al. ( 1995 ) showed that the LAST function gave more accurate results for shallow subsurface coal fires ranging in depth from a few centimeters to ∼10 m. for moderate-depth coal fires, ranging in depth from 10 m to 40 m, the depths estimated by the two functions were comparable.