The effect of rock moisture on Schmidt hammer rebound: tests on rock samples from Marion Island and South Africa

Sumner, Paul; Nel, Werner

doi:10.1002/esp.402

Cited by 103 publications

(62 citation statements)

References 13 publications

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“…allow for any movements of the rock upon impact of the Schmidt hammer, which might result in inconsistency of R−values (Sumner and Nel 2002). Silt or single grains of fine sand, if found on the analyzed surface, were re− moved, and micro−roughness was measured in three smoothest lichen−free spots (thirty measurements per test site) parallel to striation in order to omit visible mi− cro−erosional features on the run of the profilometer (Fig.…”

Section: Methodsmentioning

confidence: 99%

Rock surface micro−roughness, Schmidt hammer rebound and weathering rind thickness within LIA Skálafellsjökull foreland, SE Iceland

Dąbski¹

2014

Polish Polar Research

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Glacially abraded basaltic rock surfaces found within a Little Ice Age (LIA) fore− land of Skálafellsjökull (SE Iceland) were studied at eight sites of different age applying different weathering indices. They include surface micro−roughness parameters measured with the Handysurf E35−B electronic profilometer -a new tool in geomorphology, Schmidt hammer rebound (R−values) and weathering rind thickness. Values of these indices ob− tained from study sites exposed to subaerial weathering for more than ca. 80 years are sig− nificantly different than those from younger moraines closer to the glacier snout. Despite a wide scatter of readings within each study site, there is a significant correlation between the ages and the values of the indices. It is concluded that the micro−roughness parameters pro− vided by the Handysurf E35−B profilometer, Schmidt hammer R−values and weathering rind thickness are robust indices of rock surface deterioration rate in short time−scales. There is mounting evidence that rock surface undergoes relatively rapid weathering during first decades since deglaciation.

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Section: Methodsmentioning

confidence: 99%

Rock surface micro−roughness, Schmidt hammer rebound and weathering rind thickness within LIA Skálafellsjökull foreland, SE Iceland

Dąbski¹

2014

Polish Polar Research

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“…The block mass of the rock to be tested is signifi cant, and the test cannot be used on small, light blocks. Sumner and Nel (2002) suggest that block weight should exceed 25 kg for accurate and consistent rebound determinations, whilst Demirdag et al (2009) have found experimentally that cubic blocks should have at least 11 cm edges. Finally, there may be between-hammer variation and deterioration of hammer performance with age.…”

Section: The Classic Schmidt Hammermentioning

confidence: 97%

“…This may present particular problems for the testing of heritage structures and surfaces such as rock art panels. The test is sensitive to moisture contents, especially in weak rocks (Sumner and Nel, 2002). The block mass of the rock to be tested is signifi cant, and the test cannot be used on small, light blocks.…”

Section: The Classic Schmidt Hammermentioning

confidence: 99%

The use of the Schmidt Hammer and Equotip for rock hardness assessment in geomorphology and heritage science: a comparative analysis

Viles

Goudie

Grab

et al. 2011

Earth Surf Processes Landf

205

171

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Rapid, fi eld-based measurements of rock hardness are of use in investigating many geomorphological and heritage science problems. Several different methods are now available for taking such measurements, but little work has been done to assess their comparability and strengths and weaknesses. We review here the capabilities of two types of Schmidt Hammer (Classic N type and Silver Schmidt BL type) alongside two types of Equotip (standard type D and Piccolo) for investigating rock hardness in relation to rock weathering on various types of sandstone and limestone, as well as basalt and dolerite. Whilst the two Schmidt hammers and the two Equotips show comparable results when tested at 15 individual sites, interesting differences are found between the Equotip and Schmidt Hammer values which may reveal information about the nature of weathering on different surfaces. Operator variance is shown to be an issue in particular for the Equotip devices, which also exhibit higher variability in measurements and necessitate larger sample sizes. Carborundum pre-treatment also has varying effects on the data collected, depending on the nature of the surface studied. The Equotip devices are shown to be particularly useful on smaller blocks and in situations where edge effects may affect Schmidt Hammer readings. We conclude that whilst each device contributes to geomorphological research, they do not necessarily produce comparable information. Indeed, using Schmidt Hammer and Equotip in combination and looking at any differences in results may provide invaluable insights into the structure of the near-surface zones and the nature of weathering processes.

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“…Measurements recording an R value of <10 were assigned the value 9. In order to minimise the influence of technique error, the precautions outlined by Day and Goudie (1977), Day (1980), McCarroll (1987, 1989 and Sumner and Nel (2002) were adhered to and a sampling strategy was adopted following that of Anderson et al (1998).…”

Section: Schmidt Hammermentioning

confidence: 99%

Periglacial trimlines and nunataks of the Last Glacial Maximum: the Gap of Dunloe, southwest Ireland

Rae

Harrison

Mighall

et al. 2004

J Quaternary Science

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During the last main phase of glaciation (26-13 ka) an ice-cap developed in southwest Ireland and ice, from a dispersal centre in the vicinity of Kenmare, flowed north through the Gap of Dunloe in the Macgillycuddy's Reeks. On surrounding hillsides a weathering limit separates icemoulded bedrock, on low ground, from frost-weathered terrain above. Assessment of bedrock dilation joint characteristics, Schmidt hammer R-value data and clay-sized mineral contents of basal soil samples, demonstrate significant contrasts in the degree of weathering above and below this limit. The weathering limit declines in altitude along former ice flow-lines and is confluent with morainic deposits on the eastern side of the Gap. This supports the assertion that the high-level weathering limit is a periglacial trimline that marks the former maximum upper limit of the body of ice which occupied the Gap of Dunloe during the Last Glacial Maximum (LGM). Reconstruction of the former ice-surface profile from periglacial trimline limits on the eastern side of the Gap yields a mean estimate for basal shear stress of 106.5 kPa. This value suggests that the ice mass which occupied the Gap of Dunloe at the LGM was warm based and flowed on a bedrock substrate.

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The effect of rock moisture on Schmidt hammer rebound: tests on rock samples from Marion Island and South Africa

Cited by 103 publications

References 13 publications

Rock surface micro−roughness, Schmidt hammer rebound and weathering rind thickness within LIA Skálafellsjökull foreland, SE Iceland

Rock surface micro−roughness, Schmidt hammer rebound and weathering rind thickness within LIA Skálafellsjökull foreland, SE Iceland

The use of the Schmidt Hammer and Equotip for rock hardness assessment in geomorphology and heritage science: a comparative analysis

Periglacial trimlines and nunataks of the Last Glacial Maximum: the Gap of Dunloe, southwest Ireland

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