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Value of Laboratory Experiments for Code Validations

Description: Numerical codes have become indispensable for designing underground structures and interpretating the behavior of geologic systems. Because of the complexities of geologic systems, however, code calculations often are associated with large quantitative uncertainties. This papers presents three examples to demonstrate the value of laboratory(or bench scale) experiments to evaluate the predictive capabilities of such codes with five major conclusions: Laboratory or bench-scale experiments are a very cost-effective, controlled means of evaluating and validating numerical codes, not instead of but before or at least concurrent with the implementation of in situ studies. The design of good laboratory validation tests must identifj what aspects of a code are to be scrutinized in order to optimize the size, geometry, boundary conditions, and duration of the experiments. The design of good and sometimes difficult numerical analyses and sensitivity studies. Laboratory validation tests must involve: Good validation experiments will generate independent data sets to identify the combined effect of constitutive models, model generalizations, material parameters, and numerical algorithms. Successfid validations of numerical codes mandate a close collaboration between experimentalists and analysts drawing from the full gamut of observations, measurements, and mathematical results.
Date: December 14, 1998
Creator: Wawersik, W.R.
Partner: UNT Libraries Government Documents Department

Instrument to Measure the Initial Deformation of Rock Around Underground Openings

Description: Report issued by the Bureau of Mines over development of the tunnel stress relaxation gage. As stated in the introduction, "this report summarizes development and modification of a tunnel stress relaxation gage (TSR) designed to measure initial and long-term deformation around underground excavations" (p. 1). This report includes tables, illustrations, and photographs.
Date: 1978
Creator: Beus, Michael J.; Phillips, Earl L. & Waddell, Galen G.
Partner: UNT Libraries Government Documents Department

Concrete and Rock Core Tests, Major Rehabilitation of Starved Rock Lock and Dam, Illinois Waterway, Chicago District, Phase II Compliance, Scour Detection: Final Report

Description: Abstract: Drilling for laboratory testing of concrete and foundation rock was carried out for the U. S. Army Engineer District, Chicago, as part of a major rehabilitation program at the Starved Rock Lock and Dam. The structures are on the Illinois Waterway. This report covers the work accomplished during the Phase II program entitled "Compliance and Scour Detection."
Date: April 1980
Creator: Stowe, Richard L. & Pavlov, Barbara A.
Partner: UNT Libraries Government Documents Department

Structural Analysis of a Mechanized LHD Trench Undercut Caving System

Description: Abstract: This U. S. Bureau of Mines (USBM) report presents results of stress analyses and field observations to investigate the effects of elevated trench drifts on the structural stability of rock mass zones surrounding a production draw drift in a mine utilizing a mechanized load-haul-dump (LHD) trench undercut panel caving system. A two-dimensional boundary-element mine stress model was developed to predict the locations and extent of damaged rock mass zones surrounding draw drifts where adjacent, parallel trench drifts are either elevated or not elevated above the LHD production draw drift level. A Mohr-Coulomb shear-failure criterion was obtained directly from in situ borehole shear test data. Hoek-Brown shear-failure parameter values were computed from borehole-shear and triaxial test data. A procedure is described to estimate these parameters when a rock mass rating (RMR) value and triaxial data on intact samples exist, and no borehole shear test data exist. Results indicate that trench drifts, elevated to the level equal to the height of the LHD production draw drift, would not minimize material damage nor significantly enhance the stability of rib and crown pillar zones surrounding production draw drifts in the mechanized LHD trench undercut caving panel investigated at this mine.
Date: 1995
Creator: Jude, Charles V.
Partner: UNT Libraries Government Documents Department

Concrete and Rock Core Tests, Major Rehabilitation of Starved Rock Lock and Dam, Illinois Waterway, Chicago District, Phase I, Rehabilitation: Final Report

Description: Abstract: Drilling for laboratory testing of concrete and foundation rock was carried out for the U. S. Army Engineer District, Chicago, as part of a major rehabilitation program at the Starved Rock Lock and Dam.
Date: September 1978
Creator: Stowe, Richard L.; Pavlov, Barbara A. & Wong, Ging S.
Partner: UNT Libraries Government Documents Department

Estimates of frequency-dependent compressibility from a quasistatic double-porosity model

Description: Gassmann's relationship between the drained and undrained bulk modulus of a porous medium is often used to relate the dry bulk modulus to the saturated bulk modulus for elastic waves, because the compressibility of air is considered so high that the dry rock behaves in a drained fashion and the frequency of elastic waves is considered so high that the saturated rock behaves in an undrained fashion. The bulk modulus calculated from ultrasonic velocities, however, often does not match the Gassmann prediction. Mavko and Jizba examined how local flow effects and unequilibrated pore pressures can lead to greater stiffnesses. Their conceptual model consists of a distribution of porosities obtained from the strain-versus-confining-pressure behavior. Stiff pores that close at higher confining pressures are considered to remain undrained (unrelaxed) while soft pores drain even for high-frequency stress changes. If the pore shape distribution is bimodal, then the rock approximately satisfies the assumptions of a double-porosity, poroelastic material. Berryman and Wang [1995] established linear constitutive equations and identified four different time scales of ow behavior: (1) totally drained, (2) soft pores are drained but stiff pores are undrained, (3) soft and stiff pores are locally equilibrated, but undrained beyond the grain scale, and (4) both soft and stiff pores are undrained. The relative magnitudes of the four associated bulk moduli will be examined for all four moduli and illustrated for several sandstones.
Date: September 16, 1998
Creator: Berryman, J. G. & Wang, H. F.
Partner: UNT Libraries Government Documents Department

Concrete and Rock Tests, Major Rehabilitation and Compliance, Lockport Lock, Illinois Waterway, Chicago District: Final Report

Description: Abstract: A crack survey , drilling, field and laboratory testing of concrete, and laboratory testing of foundation rock were carried out as part of a major rehabilitation and compliance program at Lockport Lock.
Date: April 1980
Creator: Stowe, Richard L.; Ragan, Steve A.; Campbell, Roy L.; Pavlov, Barbara A.; Thornton, Henry T., Jr. & Wong, Ging S.
Partner: UNT Libraries Government Documents Department

Development and testing of a Mudjet-augmented PDC bit.

Description: This report describes a project to develop technology to integrate passively pulsating, cavitating nozzles within Polycrystalline Diamond Compact (PDC) bits for use with conventional rig pressures to improve the rock-cutting process in geothermal formations. The hydraulic horsepower on a conventional drill rig is significantly greater than that delivered to the rock through bit rotation. This project seeks to leverage this hydraulic resource to extend PDC bits to geothermal drilling.
Date: January 1, 2006
Creator: Black, Alan (TerraTek, Inc.); Chahine, Georges (DynaFlow, Inc.); Raymond, David Wayne; Matthews, Oliver (Security DBS); Grossman, James W.; Bertagnolli, Ken (US Synthetic) et al.
Partner: UNT Libraries Government Documents Department

Fluid Assisted Compaction and Deformation of Reservoir Lithologies

Description: The compaction and diagenesis of sandstones that form reservoirs to hydrocarbons depend on mechanical compaction processes, fluid flow at local and regional scales, and chemical processes of dissolution, precipitation and diffusional solution transport. The compaction and distortional deformation of quartz aggregates exposed to reactive aqueous fluids have been investigated experimentally at varying critical and subcritical stress states and time scales. Pore fluid compositions and reaction rates during deformation have been measured and compared with creep rates. Relative contributions of mechanical and chemical processes to deformation and pore structure evolution have been evaluated using acoustic emission (AE) measurements and scanning electron microscope (SEM) observations. At the subcritical conditions investigated, creep rates and acoustic emission rates fit transient logarithmic creep laws. Based on AE and SEM observations, we conclude that intragranular cracking and grain rearrangement are the dominant strain mechanisms. Specimens show little evidence of stress-enhanced solution transfer. At long times under wet conditions, the dominant strain mechanism gradually shifts from critical cracking at grain contacts with high stress concentrations to fluid-assisted sub-critical cracking.
Date: February 13, 2002
Creator: Kronenberg, A.K.; Chester, F.M.; Chester, J.S.; Hajash, A.; He, W.; Karner, S. et al.
Partner: UNT Libraries Government Documents Department

Fluid transport properties of rock fractures at high pressure and temperature. Progress report, July 1, 1978--June 30, 1979. [Lamont-Doherty Geological Observatory, July 1, 1978--June 30, 1979]

Description: Accomplishments during the first 30 months of work on the fluid transport properties of rock fractures at high pressure are discussed in detail in this report and by Kranz et. al in Int. J. Rock Mech. Min. Sci. (1979). The following results are discussed in this report. Fracture permeability is highly sensitive to initial surface roughness. Changes in permeability are found to be proportional to (BdP/sub f/ - adP/sub c/), where b/a < 1. When absolute aperture is used to calculate permeability, permeability measured by the pulse decay is constant between confining pressures of 300 b and 3 kb; this suggests that the cross-sectional area of the joint aperture varies linearly with confining pressure. Increasing pore pressure forces joints open only when the effective pressure across the joint has been reduced to less than 500 b. Dissolution in chemically active fluids affects joint permeability. 9 figures.
Date: May 1, 1979
Creator: Engelder, T. & Scholz, C.
Partner: UNT Libraries Government Documents Department

Summary of Test Results for Daya Bay Rock Samples

Description: A series of analytical tests was conducted on a suite of granitic rock samples from the Daya Bay region of southeast China. The objective of these analyses was to determine key rock properties that would affect the suitability of this location for the siting of a neutrino oscillation experiment. This report contains the results of chemical analyses, rock property measurements, and a calculation of the mean atomic weight.
Date: October 12, 2004
Creator: Onishi, Celia Tiemi; Dobson, Patrick & Nakagawa, Seiji
Partner: UNT Libraries Government Documents Department

Critical Chemical-Mechanical Couplings that Define Permeability Modifications in Pressure-Sensitive Rock Fractures

Description: This work examined and quantified processes controlling changes in the transport characteristics of natural fractures, subjected to coupled thermal-mechanical-chemical (TMC) effects. Specifically, it examined the effects of mineral dissolution and precipitation mediated by mechanical effects, using laboratory through-flow experiments concurrently imaged by X-ray CT. These were conducted on natural and artificial fractures in cores using water as the permeant. Fluid and mineral mass balances are recorded and are correlated with in-sample saturation, porosity and fracture aperture maps, acquired in real-time by X-ray CT-imaging at a maximum spatial resolution of 15-50 microns per pixel. Post-test, the samples were resin-impregnated, thin-sectioned, and examined by microscopy to define the characteristics of dissolution and precipitation. The test-concurrent X-ray imaging, mass balances, and measurements of permeability, together with the post-test microscopy, were used to define dissolution/precipitation processes, and to constrain process-based models. These models define and quantify key processes of pressure solution, free-face dissolution, and shear-dilation, and the influence of temperature, stress level, and chemistry on the rate of dissolution, its distribution in space and time, and its influence on the mechanical and transport properties of the fracture.
Date: April 25, 2007
Creator: Elsworth, Derek; Grader, Abraham & Brantley, Susan
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

Development of a Numerical Simulator for Analyzing the Geomechanical Performance of Hydrate-Bearing Sediments

Description: In this paper, we describe the development and application of a numerical simulator that analyzes the geomechanical performance of hydrate-bearing sediments, which may become an important future energy supply. The simulator is developed by coupling a robust numerical simulator of coupled fluid flow, hydrate thermodynamics, and phase behavior in geologic media (TOUGH+HYDRATE) with an established geomechanical code (FLAC3D). We demonstrate the current simulator capabilities and applicability for two examples of geomechanical responses of hydrate bearing sediments during production-induced hydrate dissociation. In these applications, the coupled geomechanical behavior within hydrate-bearing seducements are considered through a Mohr-Coulomb constitutive model, corrected for changes in pore-filling hydrate and ice content, based on laboratory data. The results demonstrate how depressurization-based gas production from oceanic hydrate deposits may lead to severe geomechanical problems unless care is taken in designing the production scheme. We conclude that the coupled simulator can be used to design production strategies for optimizing production, while avoiding damaging geomechanical problems.
Date: June 1, 2008
Creator: Rutqvist, Jonny; Rutqvist, J. & Moridis, G.J.
Partner: UNT Libraries Government Documents Department

Coupled Analysis of Change in Fracture Permeability during the Cooling Phase of the Yucca Mountain Drift Scale Test

Description: This paper presents results from a coupled thermal, hydrological and mechanical analysis of thermally-induced permeability changes during heating and cooling of fractured volcanic rock at the Drift Scale Test at Yucca Mountain, Nevada. The analysis extends the previous analysis of the four-year heating phase to include newly available data from the subsequent four year cooling phase. The new analysis of the cooling phase shows that the measured changes in fracture permeability follows that of a thermo-hydro-elastic model on average, but at several locations the measured permeability indicates (inelastic) irreversible behavior. At the end of the cooling phase, the air-permeability had decreased at some locations (to as low as 0.2 of initial), whereas it had increased at other locations (to as high as 1.8 of initial). Our analysis shows that such irreversible changes in fracture permeability are consistent with either inelastic fracture shear dilation (where permeability increased) or inelastic fracture surface asperity shortening (where permeability decreased). These data are important for bounding model predictions of potential thermally-induced changes in rock-mass permeability at a future repository at Yucca Mountain.
Date: June 1, 2008
Creator: Rutqvist, Jonny; Rutqvist, J.; Freifeld, B.; Tsang, Y.W.; Min, K.B. & Elsworth, D.
Partner: UNT Libraries Government Documents Department

A Phased Array Approach to Rock Blasting

Description: A series of laboratory-scale simultaneous two-hole shots was performed in a rock simulant (mortar) to record the shock wave interference patterns produced in the material. The purpose of the project as a whole was to evaluate the usefulness of phased array techniques of blast design, using new high-precision delay technology. Despite high-speed photography, however, we were unable to detect the passage of the shock waves through the samples to determine how well they matched the expected interaction geometry. The follow-up mine-scale tests were therefore not conducted. Nevertheless, pattern analysis of the vectors that would be formed by positive interference of the shockwaves from multiple charges in an ideal continuous, homogeneous, isotropic medium indicate the potential for powerful control of blast design, given precise characterization of the target rock mass.
Date: July 1, 2006
Creator: Gertsch, Leslie & Baird, Jason
Partner: UNT Libraries Government Documents Department

Efficient Displacement Discontinuity Method Using Fast Multipole Techniques

Description: The Displacement Discontinuity method has been widely used in geomechanics because it accurately captures the behavior of fractures within a rock mass by explicitly accounting for discontinuities. Unfortunately, boundary element techniques require the interactions between all pairs of elements to be evaluated and traditional approaches to the Displacement Discontinuity method are computationally expensive for large problem sizes. Approximate summation techniques, such as the Fast Multipole Method (FMM), calculate the interactions between N entities in time proportional to N. We have implemented a modified Fast Multipole approach which performs the necessary calculations in optimal time and with reduced memory usage. Furthermore, the FMM introduces parameters which can be selected to give the desired trade-off between efficiency and accuracy. The FMM approach permits much larger problems to be solved using desktop computers, opening up a range of applications. We present results demonstrating the speed of the code and several test cases involving rock fracture in compression.
Date: February 18, 2000
Creator: Morris, J.P. & Blair, S.C.
Partner: UNT Libraries Government Documents Department