The Schmidt Hammer, originally designed for testing the hardness of concrete in 1948, was first used in a geomorphological context in the 1960s. Since then the advantages and disadvantages of the device for measuring rock characteristics have become apparent, and the Schmidt Hammer has been used for an increasing range of purposes, including the study of various weathering phenomena, the relationships between rock strength and landform, and for relative dating of a range of Holocene features. Readings of rock hardness have often been found to correlate well with other measures of rock character, such as uniaxial compressive strength and Young’s Modulus of Elasticity.

The Schmidt Hammer in geomorphological research

Rapid, field-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. Copyright © 2010 John Wiley & Sons, Ltd.

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

Volcanic rocks from the Bodrum Peninsula have been studied to establish a relationship between the uniaxial compressive strength (UCS), Young’s modulus (E) and Schmidt hammer rebound number (N). Test results obtained on andesites, basalts and tuffs have been assessed statistically and the parameters obtained correlated. Regression equations were established between N, E and UCS.

Correlation between Schmidt hardness, uniaxial compressive strength and Young’s modulus for andesites, basalts and tuffs

Prediction of geomechanical parameters using soft computing and multiple regression approach

http://digital.csic.es/bitstream/10261/115491/1/IJRMMS_2013_61_296.pdf

Non-destructive testing for the assessment of granite decay in heritage structures compared to quarry stone

An attempt has been made to correlate the uniaxial compressive strength and Young's modulus of gabbros and basalts with Schmidt hammer rebound number, the point load strength index, Is(50) and the degree of weathering. Sixty three samples of gabbro and thirty of basalt from the ophiolitic complex of Pindos zone (Northern Greece) have been collected by core drilling and tested accordingly. The results have been processed using techniques from the statistical software SPSS. Some of the equations produced show relatively high correlation coefficients, all significant at a significance level higher than 95%. The equations establish reliable prediction models for the uniaxial compressive strength and modulus of elasticity of the above rock types by means of simple tests which can be carried out in the field.

Correlating uniaxial compressive strength with schmidt hardness, point load index, Young's modulus, and mineralogy of gabbros and basalts (northern Greece)

D. Stamoulis

Papers

Correlating uniaxial compressive strength with schmidt hardness, point load index, Young's modulus, and mineralogy of gabbros and basalts (northern Greece)