Gold River, CA, United States
Gold River, CA, United States

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Zhao H.,Agapito Associates , Inc. | Hardy M.P.,Agapito Associates , Inc. | Yu B.,Agapito Associates , Inc.
50th US Rock Mechanics / Geomechanics Symposium 2016 | Year: 2016

Creep plays an important role in mine design and ground control for potash solution mining. In order to predict the temporal evolution of underground caverns during and after solution mining, the long-term creep behavior of sylvinite and halite, i.e., secondary or steady-state creep rate, must be known. To date, however, only limited secondary creep test data for sylvinite and halite have been published. Additional laboratory compression creep tests results for sylvinite and halite samples from seven different potash projects worldwide were compiled in this paper. The influence of deviatoric stress, confining pressure, and temperature on secondary creep rate was evaluated based on these recent test data. Because the individual test conditions were originally designed to meet the specific needs of each project, the test conditions for the creep tests varied. The study in this paper is not a scientific study, however, it may be useful in regard to prediction of creep behavior of sylvinite and halite from potash deposits. This paper presents the results of those creep tests; summarizes the influence of deviatoric stress, confining pressure, and temperature on secondary creep rate, and; discusses an application of the creep test data to numerical modeling of potash deposits for mine design and ground control. Copyright 2016 ARMA, American Rock Mechanics Association.


Layton J.,Skyline Mines | Mohanty S.,Agapito Associates , Inc.
50th US Rock Mechanics / Geomechanics Symposium 2016 | Year: 2016

This paper outlines the analysis methods and results used in a geotechnical evaluation performed on the stability of two declines at the Skyline Mine. The Lower O'Connor-A (LOA) seam has been displaced by a fault within the study area at the mine. The declines have been driven in relatively thin interburden and connect the existing mains in the LOA seam to the mains in the same coal seam in the proposed underlying mine level. The primary objective of the study was assess the roof and rib stability of both the declines and the connecting crosscut, while establishing a viable brow thickness above the decline entrance. The impact of driving the declines on the stability of the mains pillars in the proximity of the decline in the upper and lower levels were analyzed, while concurrently evaluating the effect of multi-seam mining in the lower level mains pillars. The study was performed using a combination of numerical modeling tools, LAMODEL and FLAC3D. The study results indicated likely rib and roof stability within the declines and crosscut, as well as the pillars in the vicinity of declines in both the mining levels. Copyright 2016 ARMA.


Burnham A.K.,American Shale Oil LLC | Day R.L.,American Shale Oil LLC | Hardy M.P.,Agapito Associates , Inc. | Wallman P.H.,American Shale Oil LLC
ACS Symposium Series | Year: 2010

American Shale Oil LLC (AMSO) is one of three companies holding an Oil Shale RD&D Lease in Colorado from the U.S. Bureau of Land Management. AMSO is pursuing a unique strategy of recovering shale oil initially from the 2000-ft-deep illitic oil shale below the saline zone in order to isolate production from protected sources of ground water. Our method of heat distribution is also unique. We use refluxing oil to transport heat to the retort boundary, which will advance by thermo-mechanical fragmentation (spalling) due to the compressive stress caused by heating externally confined oil shale with an internal free surface. Heat is provided from a horizontal heater in an "L" shaped well using a downhole burner. Our commercial concept is to use panels of parallel horizontal heater and production wells about 2000-ft long and about 100-ft apart. Each well would produce about a million barrels over 2 to 4 years. Such an approach will disturb only about 10% of the land surface area. © 2010 American Chemical Society.


Zhao H.,Agapito Associates , Inc. | Yu B.,Agapito Associates , Inc. | Hardy M.P.,Agapito Associates , Inc. | Cakmakci G.,Eti Soda
49th US Rock Mechanics / Geomechanics Symposium 2015 | Year: 2015

Sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3) are extracted through solution mining at Eti Soda's Beypazari trona deposits in Turkey. Eti Soda will drill nineteen vertical wells and ten directional wells to develop ten new caverns, with an average depth of about 450 meters (m). This paper discusses methodology for evaluating stability of surface and production casings for the new wells during solution mining. The methods used for this study include: 1) numerical modeling and 2) the method prescribed by the American Petroleum Institute/International Organization for Standardization (API/ISO). The API/ISO method is more suitable for evaluating casing integrity while a casing is being run or shortly after it has been cemented. The numerical modeling method can analyze complicated loading conditions on a casing during solution mining. The numerical modeling method was used as the primary method for evaluation of deformation and stresses of casings for the new wells. The API/ISO method was used as an ancillary method to check the competency of the selected casings based on the modeling results. This study guides the selection of casings for the new wells that have enough strength to withstand most loadings during solution mining without an excessive degree of capacity and durability. Copyright 2015 ARMA, American Rock Mechanics Association.


Conover D.,Agapito Associates , Inc. | Ross T.,Agapito Associates , Inc. | Bigby D.,Golder Associates
Proceedings - 29th International Conference on Ground Control in Mining, ICGCM | Year: 2010

Extensive arrays of telltale roof monitoring instruments were recently installed in a Mexican copper mine and a large underground mined storage facility in the eastern U.S. The data were used to evaluate roof stability during development and retreat mining and after installation of supplemental supports. Both manual-reading and automated systems were employed and consisted of up to 64 instruments. This paper will discuss the practical issues involved with installation and monitoring, including reliability and maintenance. Examples will be given for telltale response in relation to known events affecting roof stability, including nearby pillar extraction roof caving, installation of supplemental cable bolts, and separation of the immediate roof layer. The strategy for processing the large quantity of data, presenting the data for review, monitoring the system remotely, and identifying and reporting critical events will be described.


Mohanty S.,Agapito Associates , Inc. | Vandergrift T.,Agapito Associates , Inc.
48th US Rock Mechanics / Geomechanics Symposium 2014 | Year: 2014

A study to evaluate the impact of operational pressure cycles on the long-term stability of underground hydrocarbon storage caverns in Singapore was performed. As the stored products are withdrawn for consumption and subsequently replenished during operations, frequent storage pressure variations inside the caverns are anticipated. This study evaluated whether such storage pressure fluctuations, which tend to affect rock mass strength and support strength with the passage of time, will have a significantly negative effect on the overall stability and operational life of the caverns. The study assessed the impact of pressurization and depressurization cycles on the global stability of the storage caverns using numerical models, while assuming progressive weakening of the rock mass and rock support. A sensitivity analysis was also performed to evaluate the response of the cavern rock mass to variations in a set of critical input parameters. The results of the sensitivity analysis were also used to identify an appropriate minimum operating pressure (mOP) criterion. Copyright © 2014 ARMA.


Friedman J.P.,Agapito Associates , Inc. | Mohanty S.,Agapito Associates , Inc. | Rahe J.H.,Rahe Engineering Inc.
47th US Rock Mechanics / Geomechanics Symposium 2013 | Year: 2013

This paper discusses the development of an adit-plug system for sealing historical mine adits located within the Tailings Storage Facility basin at the El Boleo project in Santa Rosalía, Mexico. The historical workings could possibly intersect proposed new mine workings that may allow future tailings to migrate from the TSF into the new mine workings, and eventually to areas outside the TSF creating potential instability and safety concerns. In order to seal the historical workings within the TSF limits, a plug system was designed to incorporate multiple barriers to minimize tailings migration and water inflow into the adits. The plug system includes a structural reinforced concrete plug, shotcrete liners around the plug, and a compacted, structural-fill buttress placed above and in front of the plug. Analytical methods, including an empirical summation-of-forces approach and three-dimensional numerical modeling, have been used to evaluate the global stability of the adit-plug system. Results of the analyses are presented. Copyright 2013 ARMA, American Rock Mechanics Association.


Mohanty S.,Agapito Associates , Inc. | Vandergrift T.,Agapito Associates , Inc.
Tunnelling and Underground Space Technology | Year: 2012

A novel approach for the analysis of the long term stability of an underground propane gas storage cavern in sedimentary rock formations is discussed in this paper. The cavern is located in Midwestern United States and is currently used to store propane at pressures of 130 pounds per square inch gauge (psig) or 0.9. MPa. It has been in service for more than three decades. An evaluation was performed of its long term potential for continued storage of liquefied petroleum gas. Numerical models with weakened peripheral elements to account for the possible deterioration of cavern pillars were developed using a boundary element code (LaModel) in order to simulate the current cavern conditions. Additional analyses were performed to study the effects of the de-pressurization, re-pressurization and pressure-testing procedures typically required to as part of the storage cavern re-commissioning process. The floor stability of the cavern, which has a layer of moisture-sensitive claystone, was also assessed. The analysis results indicated that the cavern was likely to remain competent for 30 more years of service life. © 2012 Elsevier Ltd.

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