Micromechanical modeling of thermal spallation in granitic rock

Walsh, Stuart; Lomov, I.

doi:10.1016/j.ijheatmasstransfer.2013.05.043

Cited by 60 publications

(30 citation statements)

References 33 publications

(49 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Although the primary geomorphic processes that lead to spalling vary with target lithology and local climate, candidate processes typically include oscillations in near‐surface moisture and rock‐surface temperature. For porous rocks located in temperate regions, spalling may be facilitated through the freezing of pore water, the hydration of clays, the crystallization, and subsequent hydration of salts [ Matsuoka , ; Matsuoka and Murton , ] or thermal stresses [ Aldred et al ., ; Collins and Stock , ; Eppes et al ., ; McFadden et al ., ; Walsh and Lomov , ]. In the polar desert environment of the Transantarctic Mountains, where the climate is exceedingly cold and dry, the detachment of millimeter‐thick flakes from exposed rock surfaces is thought to arise in part from thermal stress weathering [ Campbell and Claridge , ; Hall , ], although no detailed quantitative studies have yet examined the process in this end‐member environment.…”

Section: Introductionmentioning

confidence: 99%

Thermal stress weathering and the spalling of Antarctic rocks

et al. 2017

View full text Add to dashboard Cite

Using in situ field measurements, laboratory analyses, and numerical modeling, we test the potential efficacy of thermal stress weathering in the flaking of millimeter‐thick alteration rinds observed on cobbles and boulders of Ferrar Dolerite on Mullins Glacier, McMurdo Dry Valleys (MDV). In particular, we examine whether low‐magnitude stresses, arising from temperature variations over time, result in thermal fatigue weathering, yielding slow crack propagation along existing cracks and ultimate flake detachment. Our field results show that during summer months clasts of Ferrar Dolerite experience large‐temperature gradients across partially detached alteration rinds (>4.7°C mm−1) and abrupt fluctuations in surface temperature (up to 12°C min−1); the latter are likely due to the combined effects of changing solar irradiation and cooling from episodic winds. The results of our thermal stress model, coupled with subcritical crack growth theory, suggest that thermal stresses induced at the base of thin alteration rinds ~2 mm thick, common on rocks exposed for ~105 years, may be sufficient to cause existing cracks to propagate under present‐day meteorological forcing, eventually leading to rind detachment. The increase in porosity observed within alteration rinds relative to unaltered rock interiors, as well as predicted decreases in rind strength based on allied weathering studies, likely facilitates thermal stress crack propagation through a reduction of fracture toughness. We conclude that thermal stress weathering may be an active, though undervalued, weathering process in hyperarid, terrestrial polar deserts such as the stable upland region of the MDV.

show abstract

Section: Introductionmentioning

confidence: 99%

Thermal stress weathering and the spalling of Antarctic rocks

et al. 2017

View full text Add to dashboard Cite

show abstract

“…Their relatively weak rock mass strength (< 60 in Table a, b) and slope‐parallel schistosity provide, in contrast to competent, anaclinal rockwalls, multiple densely spaced detachment zones; this has been shown for exfoliated granitic rocks . The repetition of summer temperature variations as observed in all MTL records in our study sites must therefore be assumed to be an additional mechanism for granular bedrock disintegration . This means that the small, flake‐like particles detected on the upper talus segments (Figures c) need not exclusively derive from seasonal freeze–thaw in the upper meters of the bedrock, as predicted in Figure , but can also result from slow near‐surface thermal fatigue …”

Section: Interpretation and Discussionmentioning

confidence: 64%

“…16 The repetition of summer temperature variations as observed in all MTL records in our study sites must therefore be assumed to be an additional mechanism for granular bedrock disintegration. 78,79 This means that the small, flake-like particles detected on the upper talus segments ( Figures 5, 10c) need not exclusively derive from seasonal freeze-thaw in the upper meters of the bedrock, as predicted in Figure 8, but can also result from slow near-surface thermal fatigue. 80 With respect to the paraglacial timescale, our observations raise some final questions: Does repeated thermal cycling during summer play a significant role in long-term sediment production and deposition, even given its slow and microscale operation?…”

Section: Figure 10mentioning

confidence: 85%

Linking rock weathering, rockwall instability and rockfall supply on talus slopes in glaciated hanging valleys (Swiss Alps)

Meßenzehl

Viles

Otto

et al. 2018

Permafrost & Periglacial

View full text Add to dashboard Cite

In high‐alpine valleys undergoing glacier retreat, the spatial distribution of talus slopes and their sediments have been frequently used as a proxy for rockfall activity. However, within this ‘sediment‐dominated’ research focus, the deglaciated source rockwalls are often portrayed in an oversimplified way. Here, we investigate 12 rockwall‐talus systems in three glaciated hanging valleys in the Swiss Alps and explore the role of source rockwalls on the spatial pattern of talus slopes and their paraglacial rockfall activity. Data from field‐based talus slope surveys, rockwall geotechnical studies, rock temperature monitoring, frost cracking modeling and GIS‐based topoclimatic analyses are evaluated by ergodic reasoning in a principal component analysis to identify patterns of rockwall‐talus systems with respect to their topoclimatic, rock mechanical and paraglacial controls. The results show that four main factors (frost cracking, permafrost probability, rockwall morphometry and mechanical preconditioning by rock mass strength and joint orientation) combine to dictate the paraglacial and spatial variability of sediment production, rockfall activity and block size. Our study demonstrates that more emphasis must be given to source rockwalls as their instability and weathering are directly linked to landform and material characteristics of talus deposits.

show abstract

“…In particular, the idealized, semi-infinite body assumed under the Preston model [1,2] does not exist in reality: for example, the surface is not flat but roughened (particularly after spallation); the solid body may develop additional fractures as a consequence of the spallation; and the stress-state is non-uniformly distributed. Surface roughness, grain size distribution, and thermal conductivities therefore serve to generate local stress concentrations that trigger the onset of spallation [36,37]. Likewise, inter-granular boundaries are frequently sites of spall fracture initiation [7] (Figure 4).…”

Section: Resultsmentioning

confidence: 99%

Modeling Thermally Induced Failure of Brittle Geomaterials

Walsh¹

2013

View full text Add to dashboard Cite

Geothermal power promises clean, renewable, reliable and potentially widely-available energy, but is limited by high initial capital costs. Widespread adoption of geothermal energy will require access to deeply buried geothermal sources in granitic basement rocks at high temperatures and pressures. Exploiting these resources necessitates novel methods for drilling, stimulation, and maintenance, under operating conditions that are difficult or impossible to test in laboratory settings. In such environments, physically rigorous numerical modeling tools are vital to highlight potential risks, guide process optimization and reduce the uncertainties involved in these developing technologies.A drilling technology with the potential to reduced the costs associated with geothermal power is Thermal Spallation Drilling (TSD) -a novel drilling technique in which small particles (spalls) are released from the rock surface by rapid heating. While TSD has the potential to improve drilling rates of brittle granitic rocks that are typical for geothermal wells, the coupled thermomechanical processes involved in TSD are poorly described, making system control and optimization difficult for this drilling technology.The project examined the factors influencing thermal spallation of hard basement rocks. Under the project, high-resolution simulations employing Lawrence Livermore's GEODYN code were used to model spallability of different rock types as a function of grain size distribution and depth, at conditions appropriate for geothermal wells. Data collected from these simulations was used to provide qualitative information on the rocks and conditions best suited to Thermal Spallation Drilling and related rock reduction technologies. The results of the simulations were analyzed to extract parameters for future validation of empirical models describing thermal spallation at the borehole scale.

show abstract

Micromechanical modeling of thermal spallation in granitic rock

Cited by 60 publications

References 33 publications

Thermal stress weathering and the spalling of Antarctic rocks

Thermal stress weathering and the spalling of Antarctic rocks

Linking rock weathering, rockwall instability and rockfall supply on talus slopes in glaciated hanging valleys (Swiss Alps)

Modeling Thermally Induced Failure of Brittle Geomaterials

Contact Info

Product

Resources

About