Canyon Fuel Company, SUFCO Mine, Utah, USA
A subsidence evaluation was performed for impacts of longwall
mining on archeological sites, a canyon, and associated riparian ecosystem.
Colowyo Coal, Meeker, Colorado, USA
Performed laboratory testing on core and longwall pre-feasibility
study.
Costain Coal Company, Wheatcroft Mine,
Kentucky, USA
Reviewed ground conditions and developed ground control
recommendations for longwall panel development and retreat.
Cyprus Plateau Mining, Utah, USA
A four-part study was conducted of the Willow Creek Property
including an evaluation of subsidence potential and escarpment stability, a
structural mine design for initial mining in the D-Seam, and an evaluation
of longwall support yield capacity involving block modeling. Underground
drilling and sampling was performed for coal seam rock mechanics testing. A
mining sequence study was completed.
Cyprus Shoshone Coal, Wyoming, USA
Field surveys and an integrated computer-aided analysis were conducted to compare the
stability and spontaneous combustion potential for two- and three-seam gateroad systems.
Shield performance was monitored to evaluate mechanisms of yielding and
plastic deformation of the shield canopies. Cave conditions and stress
redistributions were monitored. It was concluded that the capacities of the
shields were adequate but that inclined loads on the shields caused
differential loading, tilting, and damage to the shields. Damage could be
minimized by operator training to set the shields perpendicular to the roof
and floor.
Energy West Mining Company,
Huntington, Utah, USA
Numerous projects have been performed dating back to the early
1980s (formerly UPL). A review of existing geotechnical and geological data
was conducted to provide a basis for recommendations for the instrumentation
of longwall panels in both the Deer Creek and Cottonwood Mines. The
information developed was incorporated into numerical model analyses to
investigate bounces and to develop recommendations for design modifications
for longwall gateroads to minimize the potential for bounce occurrences.
Subsidence evaluations have been conducted to evaluate powerline
transmission tower stability during and after longwall retreat mining.
Stress measurements were conducted in the vicinity of highly stressed graben
faults. These measurements were used in numerical model calibration for
prediction of face and gateroad stability during longwall retreat of several
panels through a graben.
GENWAL Resources, Inc., Huntington,
Utah, USA
A longwall feasibility study was conducted for deep cover mining
under difficult conditions including numerical analysis, gateroad design,
longwall support capacity specifications, reserves, and productivity
analysis. A longwall panel orientation study was performed including
underground and surface fracture mapping, leading to a recommendation. A
ventilation survey and network modeling were performed leading to a new fan
recommendation.
Island Creek Corporation, Potomac Division
Island Creek Potomac Division Mines have utilized longwall
techniques for more than a decade to extract coal from the Upper Freeport
Seam. To increase productivity and reduce material costs, a study was
completed consisting of underground observations, stress determinations, and
computer-aided design.
Island Creek Corporation, Providence No. 1 Mine, Kentucky, USA
Stress determination was undertaken to evaluate the causes for
cutter roof problems and to recommend alternative mine layouts to remedy the
problems.
JBR Environmental Consultants,
Utah, USA
Subsidence eva luations were conducted of a proposed Pines Lease
coal tract in central Utah. AAI provided the technical subsidence report and
wrote the subsidence, geology, and topography portions of the EIS documents.
Kaiser Coal, New Mexico, USA
The impact of the number of gateroad entries on the stability of
longwall mining in two-seam mining was evaluated for layouts using two to
three entries and "yield" pillars based on field measurements and computer
analyses. A tailgate support system was also designed to ensure open
tailgates for access. Assistance was also provided for court hearings.
Kaiser Engineers, Newlands Underground Project
Performed preliminary geotechnical longwall design as part of a
feasibility project in conjunction with Kaiser Engineers Pty., Ltd.
Meridian Minerals, Montana, USA
A geotechnical program was implemented for the Bull Mountain
Project consisting of geologic mapping, core logging, mechanical property
testing, and computer-aided stability analyses. Based on the results, an
optimum longwall mine design was developed and face support capacity was
determined. Subsidence evaluations were also completed.
Meridian Minerals, Colorado, USA
The cavability of massive overburden strata and minimum cover
requirements for longwall mining were evaluated using a geotechnical review
and computer analyses. The impact of longwall mining on surface resources,
consisting of land, wildlife and groundwater, was also assessed.
Mettiki Coal Corporation, Maryland,
USA
Ground control inspection and recommendations for longwall coal
mine with ground control problems.
Monterey Coal Company, Carlinville,
Illinois, USA
A comprehensive ground control study for the extraction of reserves
adjacent to the No. 1 Mine was conducted. The study included reviews of
existing geotechnical data, roof support plans, and design factors. In situ
stress determinations of horizontal stresses in the immediate roof were
conducted and numerical model analyses of mine entry and pillar
orientations, cut lengths, and crosscut offset distances were performed to
determine the influence of these factors on mine opening stability.
Recommendations were developed regarding panel orientation, intersection
offsets, cut lengths, pillar and entry dimensions, and longwall shield
capacity. In addition, an outline for a practical rock mechanics program was
prepared.
Mountain Coal Company, Somerset,
Colorado, USA
Coal resources in the Mt. Gunnison/West Elk Mine are contained in
multiple seams recovered by room-and-pillar and longwall mining techniques.
Subsidence, numerical modeling analyses, installation of instrumentation,
and gob vent drilling supervision projects have been completed. Design
recommendations have been presented regarding multiple-seam extraction and pillar, entry
and longwall gateroad design to enhance mine stability and resource
recovery.
Based on review of an extensive geologic study, inspection of existing
workings, and analysis of available rock mechanics data, three-seam mine
layouts were developed for a large coal reserve with 80- to 240-ft seam
interburden and 200- to 800-ft cover depth. Designs were developed for both
room-and-pillar, longwall, and shortwall mining. The mining impact on
overlying reserves was evaluated as well as surface subsidence.
Shaft preliminary designs were completed for three shafts. Geotechnical and
hydrological data were gathered for geologic characterization of the shaft
site. Drawings, specifications, and construction methods and schedules were
developed for shaft sinking. Construction schedules and costs were estimated
and a basis of design prepared for the Owner's bid package.
Instrumentation and material characterization program was completed as part
of gateroad design studies. Instrumentation was installed in gateroad to
monitor stress change and convergence during longwall mining.
Instrumentation included borehole pressure cells and tell-tale sagmeters.
Core holes were drilled to provide samples for rock mechanics testing.
In situ stress measurements were completed.
Norwest, Hayden, Colorado, USA
A structural mine design for a pilot room-and-pillar coal mine in
northwestern Colorado was developed. Core hole data, rock strength, surface
features, and the strip mine highwall were inspected, and experience from
the nearby Twentymile longwall was used in the preliminary layout
recommendations. Pillar size recommendations for mains and panels and a
preliminary longwall layout were presented.
Pittsburgh & Midway
Coal Mining Company, New Mexico, USA
Ground control and roof stability evaluation was conducted and
recommendations made regarding top coal and room span widths developed.
Plateau Mining Company, Price, Utah,
USA
An instrumentation and monitoring program was designed for the
purpose of cave progress evaluation and mine design for a three-seam coal
mine. In addition, the existing two-seam mine layouts were evaluated, and
alternative layouts were recommended to increase safety and productivity.
Seven alternative gateroad support systems were field tested, and an optimum
support system was recommended to ensure keeping the tailgate open. The
impact of longwall mining on surface subsidence and stream flow was
evaluated for two-seam mining, and assistance was provided for mine layout
design for a newly acquired property.
Powderhorn Coal Company, Colorado, USA
An alternative layout was designed for room-and-pillar mining
to optimize productivity and safety, and an instrumentation program was
initiated to monitor ground conditions and optimize the support
effectiveness.
Raven Ridge Resources, Colorado, USA
A structural stability and subsidence evaluation was conducted for
the proposed extraction by in situ combustion of a steeply dipping coal
seam.
Soldier Creek Coal Company, Price,
Utah, USA
Three-seam structural longwall mine design and ventilation network
analyses were completed for the planned future expansion of Soldier Canyon
Mine. The work consisted of stress determinations, geologic review, and
computer-aided stability analyses. Short-term and long-term air volume
requirements were determined through development of ventilation networks and
selection of fan capacities.
Ground conditions were inspected at the intersection of two eight-entry
mains, and alternative pillar sizes, rib control, and monitoring programs
were developed for long-term stability of other mains intersections under
deep cover.
Mine conditions were reviewed and numerical model analyses conducted to
assess the potential for bounces during pillar recovery operations.
Recommendations were made regarding mining sequences, limits of extraction,
and rates of retreat to reduce the bounce potential.
Somerset Mining, Colorado, USA
Stress analysis was completed for two-seam layout evaluation
including analysis of interburden stability and room-and-pillar layouts.
Southern Utah Fuel Company, Utah,
USA
Ground control problems associated with the existing gate pillar
layout were back-analyzed to provide design input for evaluation of three
alternative gate pillar layouts.
Standard Oil Company (Ohio), Kitt
Mine, West Virginia, USA
Stress measurement and evaluation of the stability of gateroads
under high horizontal stresses were undertaken; alternative layouts were
proposed and analyzed to minimize roof instabilities.
Store Norske Spitsbergen Kulkompani, Svea Mine, Norway
Existing instabilities in room-and-chamber mining layouts were
evaluated and a change in the mine plan and mining equipment recommended.
Room-and-pillar layouts were evaluated.
Sunnyside Coal Mining Company,
Sunnyside, Utah, USA
Review of geotechnical and mine operating data was conducted to
investigate the occurrence of longwall bounces and assess the application of
de-stressing techniques to reduce the potential for bounces. In addition,
recommendations for further data acquisition, monitoring, and analyses were
developed.
Twentymile Coal Company, Colorado, USA
Mine layouts and support systems were designed for the most
productive longwall mining at Foidel Creek Mine. Assistance was provided for
the design of longwall face support and in evaluating the impact of longwall
mining on surface hydrology and subsidence. Site visits and stress
determinations were performed to verify the longwall design in cooperation
with the USBM. Recommendations were made on face length, gateroad design,
and gateroad secondary support. Support requirements for the longwall panel
cut-through were determined.
U.S. Bureau of Mines—Roof Fall Detection
Measurements of roof movements and entry closures along four
longwall panel gateroads and one room-and-pillar panel were integrated to
establish simple, practical measurements for the detection of roof
instabilities in coal mines.
U.S. Bureau of Mines—Evaluation of Roof Bolt Effectiveness
An extensive instrumentation, data collection, and statistical
analyses was conducted in an underground coal mine evaluating the influence
of roof bolt tension uniformity on ground stability. This entailed a study
of satellite imagery photos, geologic structures, roof fall, installation of
300 instrumented rockbolts, development of improved rockbolt installation,
installation of roof sag, and instrumentation for 19 crosscut advances.
U.S. Bureau of Mines—Evaluation of High Horizontal Stresses on Mine
Stability
Stress measurements were undertaken in five underground coal mines
in West Virginia to evaluate the influence of horizontal stresses on roof
and floor stability.
U.S. Steel, Somerset Coal Mine, Colorado, USA
Floor heave was evaluated and alternative mining plans were
recommended to control the heave. A shaft design study was also undertaken.
Utah Fuel Company, Utah, USA
Three-seam mine layouts were reviewed and longwall layouts
developed for good stability in mining the Upper O'Connor Seam and minimal
interaction problems in the lower seams 40 to 90 ft below under a variable
cover of 400 to 1200 ft.
Utah Fuel Company, Scofield, Utah, USA
Three layouts for room-and-pillar mining were evaluated, and a
layout was selected for optimum productivity and safety during the retreat
mining.
Utah Power and Light Company,
Utah, USA
The geologic and mining factors which contributed to coal bump
occurrence were studied, stress determinations undertaken, and computer
analyses conducted to design alternative room-and-pillar layouts and pillar
pulling sequences for coal bump control at the Des-Bee-Dove Mine.
Extensive field measurements and computer analyses were performed for the
design of longwall gateroads and main entry pillar sizes for optimum
stability and resource recovery in two- and three-seam longwall mining under
variable cover up to 2300 ft and variable interburden between 20 to 100 ft
at the Deer Creek and Wilberg Mines. Other analyses were performed for the
comparison of gateroads using two- and three-entry systems, and assistance
provided for court hearings brought up by the labor union against the use of
a two-entry system.
Computer analyses and roof monitoring were conducted for support system's
design for long-term stability of the mains with spans reaching up to 24 ft
at the Cottonwood Mine.
Whitaker Coal Corporation, Kentucky,
USA
A preliminary geotechnical longwall feasibility study was conducted
for conversion of an existing room-and-pillar mine to longwall methods.
Geotechnical information in the form of surface structural mapping, core
logs, laboratory strength tests, and underground observations were compiled
and evaluated to determine the feasibility of longwall mining. An evaluation
of gateroad stability was made by numerical modeling. A subsidence analysis
was also conducted to determine the impacts of longwall mining on existing
surface structures, groundwater, and the local topography.
Ziegler Coal, Illinois, USA
Feasibility of full-extraction mining techniques for shallow
Illinois mines was investigated for the No. 11 Mine. The work consisted of
an in-depth geotechnical review, underground observations, plate-bearing
testing, and subsidence calculations.
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