Large Block Test Final Report

Lin, Weiren

doi:10.2172/15005871

Cited by 3 publications

(7 citation statements)

References 30 publications

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“…A Large Block Test (LBT) was conducted at Fran Ridge, near Yucca Mountain in 1997 and 1998 [ Lin et al , 2001; Blair , 2001; Wagner , 2002]. The LBT was designed to investigate rock mass behavior in response to controlled boundary conditions.…”

Section: Development Of Conceptual Understanding and Modelsmentioning

confidence: 99%

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Multiphysics processes in partially saturated fractured rock: Experiments and models from Yucca Mountain

Rutqvist

Tsang

2012

Reviews of Geophysics

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The site investigations at Yucca Mountain, Nevada, have provided us with an outstanding data set, one that has significantly advanced our knowledge of multiphysics processes in partially saturated fractured geological media. Such advancement was made possible, foremost, by substantial investments in multiyear field experiments that enabled the study of thermally driven multiphysics and testing of numerical models at a large spatial scale. The development of coupled‐process models within the project have resulted in a number of new, advanced multiphysics numerical models that are today applied over a wide range of geoscientific research and geoengineering applications. Using such models, the potential impact of thermal‐hydrological‐mechanical (THM) multiphysics processes over the long‐term (e.g., 10,000 years) could be predicted and bounded with some degree of confidence. The fact that the rock mass at Yucca Mountain is intensively fractured enabled continuum models to be used, although discontinuum models were also applied and are better suited for analyzing some issues, especially those related to predictions of rockfall within open excavations. The work showed that in situ tests (rather than small‐scale laboratory experiments alone) are essential for determining appropriate input parameters for multiphysics models of fractured rocks, especially related to parameters defining how permeability might evolve under changing stress and temperature. A significant laboratory test program at Yucca Mountain also made important contributions to the field of rock mechanics, showing a unique relation between porosity and mechanical properties, a time dependency of strength that is significant for long‐term excavation stability, a decreasing rock strength with sample size using very large core experiments, and a strong temperature dependency of the thermal expansion coefficient for temperatures up to 200°C. The analysis of in situ heater experiments showed that fracture closure/opening caused by changes in normal stress across fractures was the dominant mechanism for thermally induced changes in intrinsic fracture permeability during rock mass heating/cooling and that fracture shear dilation appears to be less significant. Significant effort was devoted to predicting the long‐term stability of underground excavations under (mechanical) strength degradation and seismic loading, perhaps one of the most challenging tasks within the project. We note that such long‐term strength degradation is actually an example of a chemically mediated process governed by underlying (microscopic) stress corrosion and chemical diffusion processes. In the Yucca Mountain Project, such chemically mediated mechanical changes were considered implicitly through model calibrations against laboratory and in situ heater experiments at temperatures anticipated to be experienced by the rock. A possible future research direction would be to simulate such processes mechanistically in a complete coupled THMC framework where C denotes chemical processes.

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Section: Development Of Conceptual Understanding and Modelsmentioning

confidence: 99%

“…(b) Schematic three‐dimensional perspective of the LBT showing heaters and boreholes for monitoring of displacements [ Blair , 2001]. (c) Mapped fractures [ Lin et al , 2001].…”

Section: Development Of Conceptual Understanding and Modelsmentioning

confidence: 99%

Multiphysics processes in partially saturated fractured rock: Experiments and models from Yucca Mountain

Rutqvist

Tsang

2012

Reviews of Geophysics

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“…The highest temperature measured in the block reached 142°C at ∼5 cm below the heater plane. (For a comprehensive description of the design, construction, instrumentation, and data collection systems, the reader is referred to Lin et al [2001]. )…”

Section: Advances In Modeling and Their Application To In Situ Field mentioning

confidence: 99%

“…The NUFT simulator [ Nitao , 1995, 1998], which incorporates all the TH processes listed in Table 1, was used. Lin et al [2001] summarize the comparison of simulation results to the temperature data. As with the single‐heater test and drift scale test, the model captured, in general, the dominant effect of heat conduction and the more subtle signature of convection in the data.…”

Section: Advances In Modeling and Their Application To In Situ Field mentioning

confidence: 99%

“…In the middle and late 1990s, with the construction of the Exploratory Studies Facility, an underground testing laboratory at Yucca Mountain located within a tunnel 8 m in diameter and 8 km in length, the Department of Energy Yucca Mountain Project developed a unified thermal testing strategy, initiating three large‐scale field tests, all conducted in the welded, fractured rock that will host the repository. The three tests are the single‐heater test [ Tsang and Birkholzer , 1999; Tsang et al , 1999], the drift scale test [ Birkholzer and Tsang , 2000; Mukhopadhyay and Tsang , 2003], and the large‐block test [ Lin et al , 2001; Mukhopadhyay and Tsang , 2002].…”

Section: Introductionmentioning

confidence: 99%

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Modeling of thermally driven hydrological processes in partially saturated fractured rock

Tsang¹,

Birkhölzer²,

Mukhopadhyay³

2009

Reviews of Geophysics

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[1] This paper is a review of the research that led to an indepth understanding of flow and transport processes under strong heat stimulation in fractured, porous rock. It first describes the anticipated multiple processes that come into play in a partially saturated, fractured porous volcanic tuff geological formation when it is subject to a heat source such as that originating from the decay of radionuclides. The rationale is then given for numerical modeling being a key element in the study of multiple processes that are coupled. The paper outlines how the conceptualization and the numerical modeling of the problem evolved, progressing from the simplified to the more realistic. Examples of numerical models are presented so as to illustrate the advancement and maturation of the research over the last 2 decades. The most recent model applied to in situ field thermal tests is characterized by (1) incorporation of a full set of thermal-hydrological processes into a numerical simulator, (2) realistic representation of the field test geometry in three dimensions, and (3) use of site-specific characterization data for model inputs. Model predictions were carried out prior to initiation of data collection, and the model results were compared to diverse sets of measurements. The approach of close integration between modeling and field measurements has yielded a better understanding of how coupled thermal hydrological processes produce redistribution of moisture within the rock, which affects local permeability values and subsequently the flow of liquid and gases. The fluid flow, in turn, will change the temperature field. We end with a note on future research opportunities, specifically those incorporating chemical, mechanical, and microbiological factors into the study of thermal and hydrological processes.

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Liquid phase structure within an unsaturated fracture network beneath a surface infiltration event: Field experiment

Glass

Nicholl

Ramirez

et al. 2002

Water Resources Research

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[1] We conducted a simple field experiment to elucidate structure (i.e., geometry) of the liquid phase (water) resulting from ponded infiltration into a pervasive fracture network that dissected a nearly impermeable rock matrix. Over a 46 min period, dyed water was infiltrated from a surface pond while electrical resistance tomography (ERT) was employed to monitor the rapid invasion of the initially dry fracture network and subsequent drainage. We then excavated the rock mass to a depth of $5 m, mapping the fracture network and extent of dye staining over a series of horizontal pavements located directly beneath the pond. Near the infiltration surface, flow was dominated by viscous forces, and the fracture network was fully stained. With increasing depth, flow transitioned to unsaturated conditions, and the phase structure became complicated, exhibiting evidence of fragmentation, preferential flow, fingers, irregular wetting patterns, and varied behavior at fracture intersections. ERT images demonstrate that water spanned the instrumented network rapidly on ponding and also rapidly drained after ponding was terminated. Estimates suggest that our excavation captured from $15 to 1% or less of the rock volume interrogated by our infiltration slug, and thus the penetration depth from our short ponding event could have been quite large.

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Large Block Test Final Report

Abstract: This report has been reproduced directly from the best available copy.

Cited by 3 publications

References 30 publications

Multiphysics processes in partially saturated fractured rock: Experiments and models from Yucca Mountain

Multiphysics processes in partially saturated fractured rock: Experiments and models from Yucca Mountain

Modeling of thermally driven hydrological processes in partially saturated fractured rock

Liquid phase structure within an unsaturated fracture network beneath a surface infiltration event: Field experiment

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