Home  |  Contact Us  |  Profile  |  Client List  |  Personnel  |  News  |  Jobs  |  Publications |  Links

Our Expertise . . .

Subsidence Projects (select list)

AAI has conducted subsidence evaluations for many clients in association with underground mining of coal, trona, and miscellaneous minerals in soft and hard rock.

Amax Coal Company, Illinois, USA
   AAI personnel were retained to predict the subsidence resulting from possible longwall coal mining at the Wabash Mine, underlying the Wabash River and its flood plain on the Indiana-Illinois border. Berms to protect prime farmland from innundation had to be sited and designed and surface subsidence effects quantified, in prior employment.

Amax Coal Company, Indiana, USA
   AAI personnel were retained to develop a hazards and risk assessment map and subsidence potential and surface effects predictions for very shallow longwall coal mining in southern Illinois. The site had streams, aquifers, and shallow cover challenges to mine design, in prior employment.

BHP Billiton, New Mexico, USA

First Panel-Instrumentation----Agapito Associates, Inc. contracted to BHP Billiton to procure, install, and assist in monitoring the geotechnical instrumentation in and adjacent to the first longwall panel mined at the San Juan Mine.  BHP Billiton provided the design of the instrument arrays and worked closely with AAI engineers and technicians to establish the specifications for the instruments.  The instrumentation plan consisted of 170 encapsulated borehole pressure cells, 18 hydraulic load cells installed on cable bolts, 16 sonic probe extensometers installed in 20 ft holes with 20 magnetic anchors, 41 triple anchor tell-tales, and 45 roof to floor convergence stations.   AAI also drilled 20 feet of NX core in the roof and 10 feet into the floor at five locations.

Drilling for the borehole pressure cells and the NX coring was completed with AAI’s CP-65 drill.  Holes for the tell-tales, instrumented cable bolts and sonic probes were drilled with an Exchem Turbo drill provided by BHP.  Compressed air for powering the drills and water pumps was supplied by a compressor station on surface and piped throughout the mine.  Various instrument locations required moving the drilling equipment and supplies through man doors, across conveyor belts, and into the return ventilation.  All equipment was permissible for use in the return ventilation.  All MSHA regulations and San Juan Mine safety procedures were satisfied.  AAI technicians were issued a vehicle for transportation and were able to work unescorted.

Upon completion of instrument installation, baseline readings were taken and the monitoring phase of the project began.   AAI technicians assisted with data collection as the longwall retreat approached and passed the  instrument arrays.  Over a 90% instrument success rate was achieved.

A completion report summarizing the installation details of all instruments was prepared and delivered to BHP Billiton.

AAI technicians were on site at the San Juan Mine over a period of seven months to complete the tasks involved in the original instrumentation plan and to complete the tasks added on.  The project was completed without accidents or incidents.

Second Panel-Instrumentation----AAI designed, procured, and installed three downhole time domain reflectometry (TDR) cables for monitoring subsurface caving and ground subsidence over the second ever longwall panel at the San Juan coal mine.  Three 5-1/8-inch-diameter boreholes were drilled through the longwall horizon and 7/8-inch OD coaxial cables installed from surface to total depth.  Specially designed stainless steel cable ends (designed by AAI and Northwest Machine Works Inc. of Grand Junction, Colorado) were used to facilitate reliable cable placement and borehole grouting.  A portable, self-contained data acquisition system was constructed consisting of a Campbell Scientific, Inc. TDR100 time domain reflectometer, a CR10X-2M data logger, a BP24 12-bolt rechargeable battery with a CH100 12-volt charger/regular, and a MSC20 20-watt solar panel.  The components were installed inside a weather-tight ENCTDR100 16-inch x 18-inch enclosure and attached to a protective frame.  TDR waveforms, consisting of 2,048 sample points each, were recorded every 30 minutes as the longwall face mined past each cable location.  Analysis of the waveforms provided a detailed, high-resolution record of strata separation and upward cave propagation that was ultimately useful for geotechnical mine design and gob gas reservoir characterization.

• Mining Engineering

• Ventilation Engineering

• Highwall Mining

• Blasting & Explosives Eng.

• Solution Mining

• Rock Mechanics

• Rock Testing

• Stress Measurements

• Forensic Engineering

• Geology & Drilling Management

Project Summaries - Mineral

• Base Metals

• Coal

• Fertilizer Minerals

• Gold

• Limestone

• Oil Shale

• Trona

• Other

Project Summaries - Capability

• Backfill

• Block Caving

• Directional Drilling

• Forensics

• Geologic Studies

• Longwall

• Mine Reclamation

• Overcoring Stress Determinations

• Resource/Reserve Evaluation

• Slope Stability

• Solution Mining

Abstracts

• Coal

• Hard Rock Mining

• Industrial Minerals

• Oil Shale

• Nuclear Waste

• Numerical Modeling

• Slope Stability

• Tunnels & Tunneling

• Ventilation

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.

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.

Drummond Company, Inc., Alabama, USA
   AAI personnel conducted numerous subsidence prediction studies for expansions of the Shoal Creek Longwall Coal Mine, which in part underlies the Black Warrior River.

Energy West Mining Company, 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.

FMC Corporation, Wyoming, USA
   AAI personnel assessed the subsidence effects on the surface from longwall trona mining under a highway. The predictions were found to be accurate.

JBR Environmental Consultants, Utah, USA
   Subsidence evaluations 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.

Keystone Sanitary Landfill, Inc., Pennsylvania, USA
   AAI personnel assessed the subsidence potential for a new and, later, expanding, sanitary landfill constructed above three mined-out anthracite coal seams in Lackawanna County, Pennsylvania. The issues for permitting were leakage pathways, geomembrane liner stresses, and extent of subsidence, in prior employment.

Lodestar Energy Company, Kentucky, USA
   AAI personnel were retained by attorneys for Lodestar to investigate alleged surface subsidence damages to farm structures and farmlands above the room-and-pillar workings of the Wheatcroft Mine, developed in both the Kentucky No. 9 and 11 coal seams. No defensible indications of subsidence effects on the surface or mine closure underground could be found, in prior employment.

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.

Mirant Corporation (formerly Southern Energy, Inc.), Georgia, USA
   Working cooperatively with Harza Engineering Company, AAI was retained independently to assess the subsidence potential and surface effects of subsidence over solution-mined salt beds, 1600-ft deep, under Wyandotte, Michigan, for planning a complex of three gas-fired power generation turbines in lands formerly owned by BASF Wyandotte Company.

Molycorp, Inc., Questa Mine Subsidence Monitoring and Analysis, Questa, New Mexico, USA
   AAI completed a comprehensive subsidence study for the Questa block caving molybdenum mine for Molycorp, Inc. in support of the Mine Closure/Closeout Plan ultimately submitted to the New Mexico Energy, Minerals and Natural Resources Department-Mining and Mineral Division and the New Mexico Environmental Department. The study comprised investigation of historical block caving subsidence at the Questa Mine and elsewhere, instrumentation and monitoring of subsidence over a new block cave at Questa, core drilling, laboratory core testing, field mapping, geotechnical characterization, and, ultimately, predictive modeling of future subsidence associated with the long-term mine plan. AAI developed and implemented a program for monitoring cave development and subsidence using downhole time domain reflectometry (TDR) cables. Field mapping and ground monitoring data were applied to empirical and phenomenological models for estimating the magnitude and duration of subsidence, the long-term post-mining surface topography, subsidence-related impacts, and safe timing for mine closure reclamation activities. Numerical modeling included three types of computer codes: influence function, continuum, and discontinuum codes. A highly realistic simulation of subsidence and the complex mechanisms of caving was possible using the leading-edge, three-dimensional Particle Flow Code code. Findings of the study facilitated mine closure and reclamation planning.

Monterey Coal Company, Illinois, USA
   AAI personnel modeled the subsidence and ground disturbance expected over the planned longwall coal mine, and coupled the subsidence results with a hydrogeological model to predict the water intrusion quantities when mining underneath a near-surface aquifer. The results proved to be accurate and useful in mine planning.

Mountain Coal Company, 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 and numerical modeling analyses have been conducted and design recommendations made 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. In another project, preliminary sketches were prepared of potential shaft configurations, and studies were conducted to select a preferred option. 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. In all, three separate shafts were designed.

Plateau Mining Company, 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.

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.

Waste Management of Illinois, Inc., Illinois, USA
   AAI personnel completed subsidence prediction studies for a sanitary landfill expansion overlying decades-old room-and-pillar coal mines 600 to 900 ft deep. The study predicted surface strains and tilts to allow landfill designers to plan geomembrane liners and leachate collection systems. Existing surface subsidence features were trenched to allow inspection of any ground disruptions, in prior employment.

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.