Sair Kahraman

Dominant rock properties affecting the penetration rate of percussive drills

Abstract Percussive blast hole drills were observed in eight rock types at an open pit mine and three motorway sites. The net penetration rates of the drills were calculated from the performance measurements. Rock samples were collected from the drilling locations and the physical and mechanical properties of the rocks were determined both in the field and in the laboratory. The penetration rates were correlated with the rock properties. The uniaxial compressive strength, the Brazilian tensile strength, the point load strength and the Schmidt hammer value exhibit strong correlations with the penetration rate. Impact strength shows a fairly good correlation with penetration rate. Weak correlations between penetration rate and both elastic modulus and natural density were found. Any significant correlation between penetration rate and P-wave velocity was not found. It was concluded that, among the rock properties adopted in this study, the uniaxial compressive strength, the Brazilian tensile strength, the point load strength and the Schmidt hammer value are the dominant rock properties effecting the penetration rate of percussive drills. Theoretical specific energy as defined by different research workers is proved also to be well correlated with penetration rate of percussive drills which verifies basic theoretical works on the subject. In addition, the point load and the Schmidt hammer test can practically be used in the field as a predictive tool for the estimation of penetration rate.

Prediction of the penetration rate of rotary blast hole drills using a new drillability index

Abstract Rotary blast hole drills were observed in several formations at different open pit mines and quarries. Rock samples were collected as near as possible to drilling locations and mechanical and physical properties of the total 22 rock samples were determined. Indentation tests were carried out on the block samples from the same formations. A new drillability index for the prediction of the penetration rates of rotary blast hole drills and the mechanical and physical properties of the rock formations was defined from force-indentation curves of indentation tests. A penetration rate model for rotary for blast hole drills was developed using this drillability index. It was seen that the model was valid for the formations having uniaxial compressive strength over 40 MPa and especially for carbonaceous rocks. The drillability index exhibits a significant correlation with the proportionality constant k defined in the model. It is also seen that significant correlations exist between the drillability index and rock properties suggesting that the proposed model may be used universally to estimate the penetration rate of rotary blast hole drills.

Review of Ground Characterization by Using Instrumented Drills for Underground Mining and Construction

In underground mining, many miners are injured or lose their lives because of roof/pillar instability each year, and this is a persistent safety risk. Characterization of overlying strata is important for the design of safe and cost-effective ground support systems. Entry roof characterization can be performed by geological back-mapping of the ground using various methods such as geophysical logging, borescoping, rock mass rating, and intelligent roof bolt drilling systems. This paper offers a brief review of mine roof characterization methods, followed by an introduction to and discussion of roof characterization methods using instrumented roof bolters. A brief overview of the various instrumentation systems developed for roof bolt drills is presented. The results of the preliminary study and initial testing indicate that, despite recent improvements in the area of ground characterization by instrumented drills, there are still several issues that must be addressed to improve the efficiency and accuracy of existing systems. A summary of suggested improvements is provided.

Predicting the strength and brittleness of rocks from a crushability index

Uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), and brittleness are widely used in rock engineering applications. However, preparing the test samples for the standard tests may not always be possible for weak or soft rocks. On the other hand, only rock fragments may be available to estimate the rock strength in some cases such as drilling. Therefore, developing some models for estimating the rock strength and brittleness from rock fragments will be useful. In this study, a crushability index (CI) was described from the crushing test, and the possibility of predicting UCS, BTS, and brittleness from this index was investigated. Strong and significant linear correlations were found between the CI and UCS, BTS, and one of the brittleness concepts. It was concluded that the UCS, BTS, and some brittleness concepts of rock could be estimated from the CI. The suggested method is especially useful for the drilling industry and for the cases where there are not enough samples for the standard tests. However, the study is a preliminary study on limited rock types and further study is required by including the number of different rock types.

The usability of the Cerchar abrasivity index for the evaluation of the triaxial strength of Misis Fault Breccia

The development of some predictive models for the geomechanical properties of fault breccias will be useful for geo-engineers, because the preparation of smooth specimens from the fault breccias is usually tedious and expensive. In this study, simple and multiple regression analysis were applied to the data pertaining to Misis Fault Breccia to develop predictive models for the differential stress (Δσ) from non-destructive methods including the Cerchar abrasivity index (CAI). As a result of simple regression analysis, strong relations between Δσ and indirect properties were not found. The CAI was included in the best multiple regression model for the prediction of Δσ. The significance of derived models was statistically tested. It was concluded that the CAI is a useful property for the prediction of Δσ of Misis Fault Breccia.

A preliminary study on the conversion factor used in the prediction of the UCS from the BPI for pyroclastic rocks

Preparing desired smooth specimens from pyroclastic rocks is difficult and time consuming for some standard tests such as uniaxial compressive strength (UCS) test, since they are weak or soft rocks. For this reason, the development of some equations is important for predicting the UCS of pyroclastic rocks. A linear correlation was suggested for the prediction of UCS from block punch index (BPI) test for a wide range of rock in the literature. The UCS–BPI conversion factor for this correlation is 5.1. In this study, the relation between UCS and BPI was investigated for pyroclastic rocks. Twenty-eight different samples of pyroclastic rocks were collected from the Cappadocia Region of Turkey. The UCS and BPI tests were carried out on the oven-dried samples in the laboratory. The test results were analyzed using the method of least squares regression. The linear regression analysis showed that the UCS–BPI conversion factor for the tested rocks was 3.1. This value is fairly lower than the suggested value. On the other hand, the correlation coefficients of power law functions are higher than that of the linear functions. Concluding remark is that the UCS–BPI conversion factor for the pyroclastic rocks is lower than the suggested general conversion factor and the UCS–BPI relation is best represented by the power law function.

An assessment on the indirect determination of the volumetric block proportion of Misis fault breccia (Adana, Turkey)

Volumetric block proportion (VBP) directly affects the strength of geologically complex rocks such as bimrocks (block-in-matrix rocks). Since the direct determination of VBP is difficult in most cases, some prediction methods were suggested. In this study, the VBP of Misis fault breccia, which is a type of bimrock, was determined by image analysis techniques and its predictability from P- and S-wave velocity, and density was investigated. Regression analysis showed that there is no relation between VBP and S-wave velocity. However, there is a weak relation between VBP and P-wave velocity. On the other hand, VBP was strongly correlated with density. It was concluded that P- and S-wave velocity may not be a measure of VBP of breccias. However, density is a good measure of VBP, because the relation between VBP and density is strong and statistically significant.

Electrical impedance spectroscopy measurements to estimate the uniaxial compressive strength of a fault breccia

Fault breccias are usually not suitable for preparing smooth specimens or else the preparation of such specimens is tedious, time consuming and expensive. To develop a predictive model for the uniaxial compressive strength (UCS) of a fault breccia from electrical resistivity values obtained from the electrical impedance spectroscopy measurements, twenty-four samples of a fault breccia were tested in the laboratory. The UCS values were correlated with corresponding resistivity values and a strong correlation between them could not be found. However, a strong correlation was found for the samples having volumetric block proportion (VBP) of 25–75%. In addition, it was seen that VBP strongly correlated with resistivity. It was concluded that the UCS of the tested breccia can be estimated from resistivity for the samples having VBP of 25–75%.

Estimating the Wet-Rock P-Wave Velocity from the Dry-Rock P-Wave Velocity for Pyroclastic Rocks

Seismic methods are widely used for the geotechnical investigations in volcanic areas or for the determination of the engineering properties of pyroclastic rocks in laboratory. Therefore, developing a relation between the wet- and dry-rock P-wave velocities will be helpful for engineers when evaluating the formation characteristics of pyroclastic rocks. To investigate the predictability of the wet-rock P-wave velocity from the dry-rock P-wave velocity for pyroclastic rocks P-wave velocity measurements were conducted on 27 different pyroclastic rocks. In addition, dry-rock S-wave velocity measurements were conducted. The test results were modeled using Gassmann’s and Wood’s theories and it was seen that estimates for saturated P-wave velocity from the theories fit well measured data. For samples having values of less and greater than 20%, practical equations were derived for reliably estimating wet-rock P-wave velocity as function of dry-rock P-wave velocity.

Indirect Methods to Predict the Abrasion Resistance and Slake Durability of Marbles

Marble has been widely used as building materials since ancient times. Abrasion resistance and slake durability are the important characteristics of marbles. The prediction of these marbles properties will be useful from indirect methods especially for preliminary studies. In this study, the predictability of the Bohme abrasion resistance (BA) and the slake durability (SDI) of marbles were investigated from the indirect methods such as point load index (IS50), Shore hardness index (SHI), impact strength index (ISI), and ultrasonic velocity (Vp). The evaluation of the test results showed that the SDI were correlated well to the Vp, and moderately correlated to the IS50. But, the SDI was correlated weakly to both the ISI and SHI values. On the other hand, all indirect tests values were strongly or very strongly correlated to the BA values. Some multiple regression equations were also derived for the estimation of the SDI and the BA. It can be concluded that the SDI of the tested and similar marbles can be predicted from the Vp, and IS50 values. The correlations between the SDI and both SHI and ISI values should be further investigated. Another conclusion is that dry Vp, ISI, SHI and IS50 values can be used for the prediction of the BA values of the tested and similar marbles.