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Subsidence at the Weeks Island SPR Facility

Description: The elevation change data measured at the Weeks Island SPR site over the last 16+ years has been studied and analyzed. The subsidence rate is not constant with time and while the subsidence rate may have increased slightly during the past several years, recently the rate has increased more dramatically. The most recent increase comes at a time when the Strategic Petroleum Reserve (SPR) storage mine had been emptied of oil and was in the process of being refilled with brine. Damage to surface structures that has been observed during the past 12-18 months is attributed to the continued subsidence and dtierential subsidence across structures. The recent greater subsidence rates were unanticipated according to analysis results and will be used to aid further subsidence model development.
Date: January 1, 1999
Creator: Bauer, S.J.
Partner: UNT Libraries Government Documents Department

Inversion of synthetic aperture radar interferograms for sourcesof production-related subsidence at the Dixie Valley geothermalfield

Description: We used synthetic aperture radar interferograms to imageground subsidence that occurred over the Dixie Valley geothermal fieldduring different time intervals between 1992 and 1997. Linear elasticinversion of the subsidence that occurred between April, 1996 and March,1997 revealed that the dominant sources of deformation during this timeperiod were large changes in fluid volumes at shallow depths within thevalley fill above the reservoir. The distributions of subsidence andsubsurface volume change support a model in which reduction in pressureand volume of hot water discharging into the valley fill from localizedupflow along the Stillwater range frontal fault is caused by drawdownwithin the upflow zone resulting from geothermal production. Our resultsalso suggest that an additional source of fluid volume reduction in theshallow valley fill might be similar drawdown within piedmont faultzones. Shallow groundwater flow in the vicinity of the field appears tobe controlled on the NW by a mapped fault and to the SW by a lineament ofas yet unknown origin.
Date: July 1, 2006
Creator: Foxall, B. & Vasco, D.W.
Partner: UNT Libraries Government Documents Department

PREDICTION OF SURFACE SETTLEMENT DUE TO THE DISPLACEMENT OF SOFT ZONES

Description: In areas composed of coastal plain sediments, soft zones subjected to partial overburden may be present in the subsurface. During or after a seismic event, these soft zones may be compressed. The resulting displacement due to the deformation of the soft zones will propagate to the ground surface and cause the surface to settle. This paper presents a method to predict the settlement at the surface due to the propagation of the displacement from the soft zones. This method is performed by discretizing the soft zones into multiple clusters of finite sub-areas or subspaces. Settlement profile at the ground surface due to the displacement of each sub-area or subspace is computed assuming the shape is a normal distribution function. Settlement due to the displacement of the soft zones can then be approximated by adding the settlements computed for all the sub-areas or subspaces. This method provides a simple and useful tool for the prediction of the settlement profile and the results are consistent with those obtained from the finite difference analysis.
Date: March 3, 2008
Creator: Li, W
Partner: UNT Libraries Government Documents Department

Subsidence events in the Krafla area: Preliminary report based on tilt and distance measurements

Description: In the inflation-deflation sequence of the Krafla magma chamber since its beginning in 1975, 10 deflation or subsidence events have been identified until July 1978. The tilt and distance measurements relating to these subsidence events are discussed in some detail. All of these subsidence events are associated with horizontal magma flow along the N-S trending fissure zone, which goes through the central part of the suggested Krafla caldera to form a dike 3 to 5 meter wide, 80 km long and 1.0 to 2.5 km high from the bottom to the top. The total volume of magma, which flowed out of the Krafla magma chamber during these 10 events, is estimated as 392 x 10{sup 6} m{sup 3}, whereof 318 x 10{sup 6} m{sup 3} are estimated to have flowed northwards, 72 x 10{sup 6} m{sup 3} southwards and about 2 x 10{sup 6} m{sup 3} came to the surface as basaltic lava.
Date: December 1, 1978
Creator: Tryggvason, Eysteinn
Partner: UNT Libraries Government Documents Department

Geomechanical analyses to investigate wellbore/mine interactions in the Potash Enclave of Southeastern New Mexico.

Description: Geomechanical analyses have been performed to investigate potential mine interactions with wellbores that could occur in the Potash Enclave of Southeastern New Mexico. Two basic models were used in the study; (1) a global model that simulates the mechanics associated with mining and subsidence and (2) a wellbore model that examines the resulting interaction impacts on the wellbore casing. The first model is a 2D approximation of a potash mine using a plane strain idealization for mine depths of 304.8 m (1000 ft) and 609.6 m (2000 ft). A 3D wellbore model then considers the impact of bedding plane slippage across single and double cased wells cemented through the Salado formation. The wellbore model establishes allowable slippage to prevent casing yield.
Date: April 1, 2010
Creator: Ehgartner, Brian L.; Bean, James E. (Sandia Staffing Alliance, LLC, Albuquerque, NM); Arguello, Jose Guadalupe, Jr. & Stone, Charles Michael
Partner: UNT Libraries Government Documents Department

An informal expert judgment assessment of subsidence mitigation options for low-level radioactive waste management sites on the Nevada Test Site

Description: An assessment of options to mitigate the effects of subsidence at low-level radioactive waste disposal sites on the Nevada Test Site was conducted using an informal method of expert judgment. Mitigation options for existing waste cells and future waste cells were identified by a committee composed of knowledgeable personnel from the DOE and DOE-contractors. Eight ranking factors were developed to assess the mitigation options and these factors were scored through elicitation of consensus views from the committee. Different subsets of the factors were applied respectively, to existing waste cells and future waste cells, and the resulting scores were ranked using weighted and unweighted scores. These scores show that there is a large number of viable mitigation options and considerable flexibility in assessing the subsidence issue with a greater range of options for future waste cells compared to existing waste cells. A highly ranked option for both existing and future waste cells is covering the waste cells with a thick closure cap of native alluvium.
Date: March 1, 1999
Creator: Crowe, B.M.; Leary, K.; Jacobson, R.; Bensinger, H. & Dolenc, M.
Partner: UNT Libraries Government Documents Department

RCRA Post-Closure Monitoring and Inspection Report for CAU 91: Area 3 U-3fi Waste Unit, Nevada Test Site, Nevada, for the Period October 1999-October 2000

Description: This annual Neutron Soil Moisture Monitoring report provides an analysis and summary for site inspections, meteorological information, and neutron soil moisture monitoring data obtained at the U-3fi Resource Conservation and Recovery Act Unit, located in Area 3 of the Nevada Test Site, Nye County, Nevada, during the October 1999 to October 2000 period. Inspections of the U-3fi Resource Conservation and Recovery Act Unit are conducted to determine and document the physical condition of the concrete pad, facilities, and any unusual conditions that could impact the proper operation of the waste unit closure. The objective of the neutron-logging program is to monitor the soil moisture conditions along the 128-meter (m) (420-feet [ft]) ER3-3 monitoring well and detect changes that maybe indicative of moisture movement in the regulated interval extending between 73 to 82 m (240 to 270 ft) or to detect changes that maybe indicative of subsidence within the disposal unit itself. Physical inspections of the closure were completed in March and September 2000 and indicated that the site is in good condition with no significant findings noted. The directional survey which is required to be completed every five years was run in the ER3-3 casing to determine if subsidence was occurring in the U-3fi emplacement borehole. Small changes were noted which are attributed to initial settling of the sand pack stemming. No evidence of subsidence within the emplacement borehole was observed. The subsidence survey for the October 1999 to October 2000 monitoring period indicated an increase in elevation of 0.244 centimeters (cm) (0.008 ft) compared to the previous year, July 1999. All changes in subsidence survey data taken to date are so small as to be at the survey instrument resolution level and it is not clear if they represent subsidence or measurement error. There is no clear evidence for ...
Date: February 1, 2001
Creator: Emer, D. F.
Partner: UNT Libraries Government Documents Department

Analysis of subsidence data for the West Hackberry site, Louisiana

Description: The elevation change data measured at the West Hackberry SPR site over the last 14+ years has been studied and a model utilized to project elevation changes into the future. The subsidence rate has decreased with time due to instituting maintenance of higher operating pressures for caverns (since about 1990) and the normal decrease in creep closure rate of caverns with time. However, the subsidence at the site is projected to continue. As a result, low lying regions exist and the extents of these regions are projected to increase with time. These low lying regions are susceptible to inundation with water from Black Lake and/or hurricane storm surges. This work may assist DOE in planning the construction and location of mitigative measures for flood control.
Date: August 1, 1997
Creator: Bauer, S.J.
Partner: UNT Libraries Government Documents Department

The dominant processes responsible for subsidence of coastal wetlands in south Louisiana

Description: Wetland loss in coastal areas of Terrebonne and Lafourche Parishes, Louisiana, largely results from two subsurface processes: (1) consolidation of recently deposited Holocene deltaic sediments and (2) active growth faulting. Locally, settlement is high where the thickness of valley fill is great and in broad interdistributary basins where the thickness of consolidation-prone, peaty soils is great. The delta cycle is identified as the fundamental sedimentologic unit that constitutes the lower delta plain. Peaty soils from the waning phase of the delta cycle are identified as the deltaic facies most subject to consolidation settlement. Data indicate direct relationships between the thickness of deltaic sediments in individual delta cycles, and the thickness of peaty soils capping these cycles, with present patterns of coastal tract land loss. In addition, active growth faulting is correlated with new areas of interior tract wetland loss. Consolidation and faulting largely explain the curious nature of wetland loss patterns in south Louisiana. Subsidence in The Netherlands has been attributed to similar causes, i.e. thick deposits of consolidation-prone sediments that accumulate on the downthrown sides of basin margin faults.
Date: December 31, 1995
Creator: Kuecher, G.J.
Partner: UNT Libraries Government Documents Department

Sinkhole progression at the Weeks Island, Louisiana, Strategic Petroleum Reserve (SPR) site

Description: A sinkhole measuring 11 m (36 ft) across and 9 m (30 ft) deep was first observed in alluvium overlying the Weeks Island, Louisiana, salt dome in May 1992, but it was about a year old, based on initial surface appearance and subsequent reverse extrapolation of growth rates. A second and much smaller sinkhole was identified in early 1995, nearly three years later. Their position directly over the edges of the SPR oil storage chamber, a former room-and-pillar salt mine, caused apprehension. The association of sinkholes over mines is well established and this occurrence suggested that groundwater influx undoubtedly was causing salt dissolution at shallow depth, and associated collapse of soil at the surface. Leaks of groundwater into other salt mines in Louisiana and elsewhere led to flooding and eventual abandonment (Coates et al., 1981). Consequently, much attention has been and continues to be given to characterizing these sinkholes, and to mitigation. This paper summarizes current engineering geologic concepts, and briefly describes diagnostic and risk mitigation efforts being conducted by the US Department of Energy, operator of the Strategic Petroleum Reserve (Bauer et al., 1994).
Date: November 1, 1995
Creator: Neal, J.T.; Bauer, S.J. & Ehgartner, B.L.
Partner: UNT Libraries Government Documents Department

THE REMEDIATION OF ABANDONED IRON ORE MINE SUBSIDENCE IN ROCKAWAY TOWNSHIP, NEW JERSEY

Description: This report represents the thirteenth Technical Progress Report issued in connection with the subsidence remediation projects undertaken by Rockaway Township in Morris County, New Jersey. This report provides a summary of the major project work accomplished during this semi annual reporting period and contemplated for the subsequent reporting period. This report is issued as part of the project reporting provisions set forth in the Cooperators Agreement between the United States Government--Department of Energy, and Rockaway Township. The purpose of the Cooperators Agreement is for the Department of Energy to provide technical and financial assistance in a coordinated effort with Rockaway Township to develop and implement a multi-phased plan to remediate ground stability problems associated with abandoned mining activity. Primarily during the 1800's, extensive iron ore mining and prospecting was undertaken in Rockaway Township, part of the Dover District Mining region in Morris County. The abandoned mining activity has resulted in public safety hazards associated with ground collapse and surface subsidence features evolving in both developed and undeveloped areas within Rockaway Township. At the Green Pond Mine site at the Township's Jacobs Road Compost Storage Facility, construction was completed during this reporting period and surface monitoring began. Surface monitoring was conducted periodically at the Mt. Hope Road subsidence work area and adjacent areas after the January 2000 construction effort.
Date: December 1, 2003
Creator: Gartenberg, Gary
Partner: UNT Libraries Government Documents Department

Analysis of Subsidence Data for the Big Hill Site, Texas

Description: The elevation change data measured at the Big Hill SPR site over the last 10 years has been studied and a model utilized to project elevation changes into the future. The subsidence rate at Big Hill is low in comparison with other Strategic Petroleum Reserve sites and has decreased with time due to the maintenance of higher operating pressures and the normal decrease in creep closure rate of caverns with time. However, the subsidence at the site is projected to continue. A model was developed to project subsidence values 20 years into the future; no subsidence related issues are apparent from these projections.
Date: June 1, 1999
Creator: Bauer, Stephen J.
Partner: UNT Libraries Government Documents Department

THE REMEDIATION OF ABANDONED IRON ORE MINE SUBSIDENCE IN ROCKAWAY TONWSHIP, NEW JERSEY

Description: This report represents the tenth Semi-Annual Technical Progress Report issued in connection with the subsidence remediation projects undertaken by Rockaway Township in Morris County, New Jersey. This report provides a summary of the major project work accomplished during this reporting period and contemplated for the subsequent reporting period. This report is issued as part of the project reporting provisions set forth in the Cooperators Agreement between the United States Government-Department of Energy, and Rockaway Township. The purpose of the Cooperators Agreement is for the Department of Energy to provide technical and financial assistance in a coordinated effort with Rockaway Township to develop and implement a multi-phased plan to remediate ground stability problems associated with abandoned mining activity. Primarily during the 1800's, extensive iron ore mining and prospecting was undertaken in Rockaway Township, part of the Dover District Mining region in Morris County. The abandoned mining activity has resulted in public safety hazards associated with ground collapse and surface subsidence features evolving in both developed and undeveloped areas within Rockaway Township. At the Green Pond Mine site at the Township Compost Storage Facility, engineering continued during this reporting period toward development of the Construction Plans and Technical Specifications for the remediation work. At the Mt. Hope Road subsidence, surface monitoring was conducted periodically at the work area and adjacent areas after the January 2000 construction effort.
Date: February 1, 2003
Creator: Gartenberg, Gary
Partner: UNT Libraries Government Documents Department

Hulin Geopressure-geothermal test well: First order levels

Description: The purpose of this survey was to level through and establish elevations for existing benchmarks along LA Highway No. 685 from Erath, Louisiana south to the well site. The leveling was performed in April 1991, and was accomplished using procedures and equipment identical to that used by the National Geodetic Survey for First Order Class I Leveling. The leveling began on benchmark NGS T-361 located in Erath, Louisiana and the published elevation of 5.271 feet was used for this survey. On this survey a new benchmark, HU-18 was set on a concrete slab in the well site to observe the subsidence of the ground surface. Also, benchmark No.8 could not be found. A two hour search was made with no results. At this leveling it was noted that an error was made. A metric D.E. was used for the well head elevation instead of feet. This error has been corrected in this report.
Date: April 1, 1991
Partner: UNT Libraries Government Documents Department

Brazoria County Re-Leveling Pleasant Bayou Geopressured Well Site

Description: The purpose is to conduct first order leveling surveys as part of an ongoing environmental monitoring program for geopressured-geothermal test wells. The scope is to Conduct First Order, Class I, leveling to monitor subsidence of previously installed and leveled bench marks, established by the National Geodetic Survey (NGS) and Vernon F. Meyer and Associates, Inc., in the area of the Pleasant Bayou geopressured test well. All leveling surveys to conform to NGS standards and specifications.
Date: July 1, 1984
Partner: UNT Libraries Government Documents Department

Seismological evidence for Lateral magma intrusion during the July 1978 deflation of the Krafla volcano in NE-Iceland

Description: The July 1978 deflation of the Krafla volcano in the volcanic rift zone of NE-Iceland was in most respects typical of the many deflation events that have occurred at Krafla since December 1975. Separated by periods of slow inflation, the deflation events are characterized by rapid subsidence in the caldera region, volcanic tremor and extensive rifting in the fault swarm that transects the volcano. Earthquakes increase in the caldera region shortly after deflation starts and propagate along the fault swarm away from the central part of the volcano, sometimes as far as 65 km. The deflation events are interpreted as the result of subsurface magmatic movements, when magma from the Krafla reservoir is injected laterally into the fault swarm to form a dyke. In the July 1978 event magma was injected a total distance of 30 km into the northern fault swarm. The dyke tip propagated with the velocity of 0.4-0.5 m/sec during the first 9 hours, but the velocity decreased as the length of the dyke increased. Combined with surface deformation data, these data can be used to estimate the cross sectional area of the dyke and the driving pressure of the magma. The cross sectional area is variable along the dyke and is largest in the regions of maximum earthquake activity. The average value is about 1200 m{sup 2}. The pressure difference between the magma reservoir and the dyke tip was of the order of 10-40 bars and did not change much during the injection.
Date: July 1, 1978
Creator: Einarsson, Pall & Brandsdottir, Bryndis
Partner: UNT Libraries Government Documents Department

Final state of the Strategic Petroleum Reserve (SPR) Weeks Island Mine

Description: This report documents the decommissioning and abandonment activities at the Weeks Island Strategic Petroleum Reserve (SPR) site, Iberia Parish, Louisiana, that were concluded in 1999. These activities required about six years of intense operational, engineering, geotechnical, and management support efforts, following initiation of site abandonment plans in 1994. The Weeks Island SPR mine stored about 72.5 million bbl of crude oil following oil fill in 1980--1982, until November 1995, when the DOE initiated oil drawdown procedures, with brine refill and oil skimming, and numerous plugging and sealing activities. About 98% of the crude oil was recovered and transferred to other SPR facilities in Louisiana and Texas; a small amount was also sold. This document summarizes recent pre- and post-closure: conditions of surface features at the site, including the sinkholes, the freeze wall, surface subsidence measurements and predictions; conditions within the SPR mine, including oil recovery, brine filling, and the Markel Wet Drift; risk assessment evaluations relevant to the decommissioning and long-term potential environmental impacts; continuing environmental monitoring activities at the site; and, an overview on the background and history of the Weeks Island SPR facility.
Date: February 1, 2000
Creator: MOLECKE,MARTIN A.
Partner: UNT Libraries Government Documents Department

THE REMEDIATION OF ABANDONED IRON ORE MINE SUBSIDENCE IN ROCKAWAY TOWNSHIP, NEW JERSEY

Description: This report represents the sixth Semi-Annual Technical Progress Report issued in connection with the subsidence remediation projects undertaken by Rockaway Township in Morris County, New Jersey. This report provides a summary of the major project work accomplished during this reporting period and contemplated for the subsequent reporting period. This report is issued as part of the project reporting provisions set forth in the Cooperators Agreement between the United States Government--Department of Energy, and Rockaway Township. The purpose of the Cooperators Agreement is for the Department of Energy to provide technical and financial assistance in a coordinated effort with Rockaway Township to develop and implement a multi-phased plan to remediate ground stability problems associated with abandoned mining activity. Primarily during the 1800's, extensive iron ore mining and prospecting was undertaken in Rockaway Township, part of the Dover District Mining region in Morris County. The abandoned mining activity has resulted in public safety hazards associated with ground collapse and surface subsidence features evolving in both developed and undeveloped areas within Rockaway Township. At the White Meadow Mine site, after amended specifications were prepared and continued negotiations took place with the Property Owner, the property ownership was transferred during the reporting period. As a result in the change in property ownership, the remediation project was then to be done by the new Property Owner out of the responsibility of Rockaway Township under this Cooperators Agreement. At the Mt. Hope Road subsidence, surface monitoring was conducted at the work area and adjacent areas after the January 2000 construction effort. At the Green Pond Mine site at the Township Compost Storage Facility, no additional field work was undertaken during this reporting period subsequent to the previous completion of the geophysical survey. With the termination of the White Meadow Mine project, work began toward development of ...
Date: April 1, 2001
Creator: Gary Gartenberg, P.E., P.P.
Partner: UNT Libraries Government Documents Department

THE REMEDIATION OF ABANDONED IRON ORE MINE SUBSIDENCE IN ROCKAWAY TOWNSHIP, NEW JERSEY

Description: This report represents the seventh Semi-Annual Technical Progress Report issued in connection with the subsidence remediation projects undertaken by Rockaway Township in Morris County, New Jersey. This report provides a summary of the major project work accomplished during this reporting period and contemplated for the subsequent reporting period. This report is issued as part of the project reporting provisions set forth in the Cooperators Agreement between the United States Government--Department of Energy, and Rockaway Township. The purpose of the Cooperators Agreement is for the Department of Energy to provide technical and financial assistance in a coordinated effort with Rockaway Township to develop and implement a multi-phased plan to remediate ground stability problems associated with abandoned mining activity. Primarily during the 1800's, extensive iron ore mining and prospecting was undertaken in Rockaway Township, part of the Dover District Mining region in Morris County. The abandoned mining activity has resulted in public safety hazards associated with ground collapse and surface subsidence features evolving in both developed and undeveloped areas within Rockaway Township. At the Green Pond Mine site at the Township Compost Storage Facility, research and preliminary design was performed during this reporting period toward development of the engineering plans and Technical Specifications for the remediation work. At the White Meadow Mine site, the remediation project was conducted last reporting period by others, out of the responsibility of Rockaway Township under this Cooperators Agreement. At the Mt. Hope Road subsidence, surface monitoring was conducted at the work area and adjacent areas after the January 2000 construction effort.
Date: April 1, 2001
Creator: Gary Gartenberg, P.E., P.P.
Partner: UNT Libraries Government Documents Department

THE REMEDIATION OF ABANDONED IRON ORE MINE SUBSIDENCE IN ROCKAWAY TOWNSHIP, NEW JERSEY

Description: This report represents the fourth Semi-Annual Technical Progress Report issued in connection with the subsidence remediation projects undertaken by Rockaway Township in Morris County, New Jersey. This report provides a summary of the major project work accomplished during this reporting period and contemplated for the subsequent reporting period. This report is issued as part of the project reporting provisions set forth in the Cooperators Agreement between the United States Government--Department of Energy, and Rockaway Township. The purpose of the Cooperators Agreement is for the Department of Energy to provide technical and financial assistance in a coordinated effort with Rockaway Township to develop and implement a multi-phased plan to remediate ground stability problems associated with abandoned mining activity. Primarily during the 1800's, extensive iron ore mining and prospecting was undertaken in Rockaway Township, part of the Dover District Mining region in Morris County. The abandoned mining activity has resulted in public safety hazards associated with ground collapse and surface subsidence features evolving in both developed and undeveloped areas within Rockaway Township. During this reporting period the Engineering Design for remediation of the surface safety hazards associated with the White Meadow Mine was completed. Construction Plans and Technical Specifications were completed and competitive bids were solicited by the Township for completion of the work. The electrical resistivity survey analysis and report was completed for the Green Pond Mines site at the Township Compost Storage Facility. The geophysical survey results confirmed evidence of abandoned mining activity at the Green Pond Mine site which was previously identified. During this reporting period, the time frame of the Cooperative Agreement between the Township and the Department of Energy was extended. An additional site of subsidence with in the Township related to abandoned mining activity at Mount Hope Road was selected by Rockaway Township to be considered ...
Date: October 1, 1999
Creator: Gartenberg, Gary
Partner: UNT Libraries Government Documents Department

Microseismic monitoring of the Sweet Lake, Louisiana, MagmaGulf-Technadril/D.O.E./Amoco Fee No. 1 Geopressured/Geothermal Energy Test Well Program: Final Report, 20 May 1980-31 May 1984

Description: The overall objective of the project was to study the seismic effects of fluid withdrawal from deep reservoirs and its subsequent reinjection closer to the surface. This effort included the design and installation of a hardware system and development of a study approach to monitor dynamic deformation in the Gulf Coast environment. Over the long term, insight gained into the ground deformation process (specifically ground subsidence) may potentially allow the integration of observations of individual phenomena into predictive tools for future use in ground subsidence studies. The value of a seismic monitoring network as a predictive tool can only be evaluated by an integrated program to study ground and instrument performance with time. Integrating extended real time monitoring of potential seismic precursors to significant displacements may represent the first integrated study of subsidence undertaken in the Gulf Coast region.
Date: May 31, 1984
Partner: UNT Libraries Government Documents Department

Evaluation of European empirical methods for subsidence in US coal fields

Description: The purpose of this study was to assess the applicability of European subsidence methods for the emerging US longwall practice. Subsidence prediction in Europe has typically used either graphical methods (United Kingdom) or mathematical methods. The mathematical methods utilize either profile or influence functions. The graphical methods were developed in the United Kingdom (UK) by the National Coal Board (NCB) from subsidence data obtained from numerous mines. Although a large data base in the United States (US) is not available, the methods can be tested against some recent measurements of subsidence of an essentially flat deposit mined at a depth of 189 m in the Illinois Coal Basin. While the total predicted subsidence by the NCB method is approximately correct, the profile shapes are not well matched. On the other hand, the profile functions, which are fundamentally independent of orientation with respect to mining, give quite accurate representation of the measured profiles. Of the antisymmetric forms tried, a trigonometric form was slightly preferably because it predicted strains that were conservative, i.e., always somewhat greater than the measured values. These results suggest that much of the European subsidence experience is applicable to US practice. Consistent values of the parameters were found for profiles with similar initial conditions or similar orientations for two longwall panel results. It should be noted that the actual profiles were always somewhat more complex than the profile functions could adequately handle and that the development curves showed time-dependent effects as well. The magnitude of these time-dependent effects, while possibly small compared to the time-independent or instantaneous subsidence, are of importance and must eventually be incorporated into a proper analysis.
Date: April 1, 1980
Creator: Munson, D.E. & Eichfeld, W.F.
Partner: UNT Libraries Government Documents Department