Predicting the sawability of carbonate rocks using multiple curvilinear regression analysis

Performance measurements of large-diameter circular saws were conducted on 13 different carbonate rocks in marble factories located in Turkey. Rock samples were collected from the factories for laboratory tests. Cohesion, friction angle, uniaxial compressive strength, tensile strength, Schmidt hammer value, point load strength, impact strength, Los Angeles abrasion loss and P-wave velocity values were determined in the laboratory. Slab production and rock properties were evaluated using multiple curvilinear regression analysis and estimation models were developed. Advancing rate of saw, saw diameter, depth of cut, tensile strength and impact strength were included for the best model. Alternative and more universal models were developed, including each rock property in turn together with the rotational speed of the saw. The developed models were verified by statistical tests.It was concluded that the slab production of carbonate rocks using large-diameter circular saws can reliably be estimated using one of the developed models. The models which include Schmidt hammer value, point load strength, impact strength and P-wave velocity have practical and economical advantages for the stone industry.     

A field index to determine the strength characteristics of crushed aggregate

The suitability of a simple technique to determine the strength characteristics of aggregates is reviewed. The results indicate that the strength characteristics of aggregates – in terms of crushing, impact and abrasion values – can be estimated and predicted from simple and quick tests for rock strength such as the Schmidt hammer and point load. The rocks and aggregates used in this work were of igneous, sedimentary and metamorphic origin and of different types, ages and degrees of weathering. More than 110 rocks and aggregate samples were tested according to British Standard and ASTM. The laboratory tests included the Schmidt hammer and point load for rock material while the crushing impact and Los Angeles abrasion test were undertaken on the aggregates. Regression analyses were performed and empirical relationships between the strength of rocks (in terms of their compressive strength and point load indices) and aggregates (in terms of their crushing, impact and abrasion values) were developed. Relatively strong relationships were obtained between the compressive strength of the rock and the crushing and impact value of the aggregate, while moderately strong relationships were obtained for the Los Angeles abrasion values. Electronic Publication     

Correlation between slake durability and rock properties for some carbonate rocks

The paper reports a study to assess the relationship between slake durability indices and uniaxial compressive strength, Schmidt hardness, P-wave velocity, modulus of elasticity, effective porosity, water absorption and dry and saturated unit weight for seven types of carbonate rocks obtained from south west Turkey. It was found that the dry unit weight, saturated unit weight and Schmidt hardness gave the best relationship with first cycle slake durability (r = 0.99) while uniaxial compressive strength has a strong relationship with fourth cycle slake durability (r = 0.94). The results showed little difference in the correlation coefficients obtained after the fourth cycle. It is concluded that, for the rocks studied, the first and fourth cycles provide sufficiently good data on the durability for preliminary engineering/design works and that the second to fourth cycle results could be estimated using the first cycle slake durability index (r = 0.99–0.97).     

Multifactorial fuzzy approach to the sawability classification of building stones

The performances of circular sawing with diamond impregnated tools were evaluated in stone processing plants located in some areas of Turkey. Samples were collected from these factories for the laboratory tests. Uniaxial compressive strength, tensile strength, Schmidt hammer value, point load strength, impact strength, Los Angeles abrasion loss and P-wave velocity were determined in the laboratory. Performance measurements and stone properties were evaluated by using the multifactorial fuzzy approach which is a special case of multiple objective multifactorial decision making for the sawability classification of building stones. Using three different decision functions, the sawing performances of diamond saws were classified into three categories: excellent, good and poor. It is possible to evaluate the sawability and select a suitable diamond saw for a new building stone by only some stone properties testing using the developed fuzzy classification system.     

Estimating the unconfined compressive strength of intact rocks from Equotip hardness

In order to utilize the Equotip hardness tester, originally developed in the field of metallic engineering, as an indirect method to predict the unconfined compressive strength (UCS) of rock, laboratory tests were undertaken to establish the UCS, Equotip hardness (L-value) and porosity of nine rock types. Using existing data from Verwaal and Mulder (Int J Rock Mech Min Sci Geomech Abstr 30:659–662, 1993) and the results of laboratory tests, an equation relating UCS (MPa) and L-value obtained from single impacts (L _s) and porosity (n %) was derived, which provides a close approximation of the UCS value. An equation to relate UCS and Equotip hardness is also presented, although this is less accurate. It is considered Equotip testing has advantages over the commonly used Schmidt hammer test.      

Estimation of uniaxial compressive strength from point load strength,Schmidt hardness and P-wave velocity

Uniaxial compressive strength is considered one of the most important parameters in the characterization of rock material in rock engineering practice. The study investigated correlations between uniaxial compressive strength and point load index, P-wave velocity and Schmidt hardness rebound number together with the effects of core diameter size. A total of 150 core samples at five different diameters (54, 48, 42, 30 and 21 mm) were obtained from sandstone, limestone and cement mortar. Ten saturated samples at each diameter (length:diameter ratio 2:1) were prepared from each of the three materials. The best correlations were found between uniaxial compressive strength and point load or Schmidt hammer values. The closest relationship was observed for the 48 mm diameter cores.      

Predicting the physico-mechanical properties of rocks from electrical impedance spectroscopy measurements

Electrical resistivity values of eight different samples cored from a fault breccia were measured using an impedance analyser. The uniaxial compressive strength, elastic modulus, point load strength, Schmidt hammer value, P-wave velocity, density and porosity values of the samples were determined in the laboratory. Electrical resistivity values were correlated with the corresponding physico-mechanical properties using the method of least-squares regression and the derived equations were checked by the t and F-test. A strong logarithmic relation between uniaxial compressive strength and resistivity was found. The relation between elastic modulus and resistivity is significant and follows a logarithmic function. Density was linearly, and porosity was exponentially correlated with resistivity.It may be concluded that electrical resistivity can be used as a representative measure of rock properties, particularly for characterizing rocks for which regularly shaped specimen are difficult to obtain. However, the effect of different rock types on the correlations must be further investigated. Additionally, the effect of certain minerals on the rock's resistivity must be taken into account, especially when testing dry or partially saturated rocks.     

Dominant rock properties affecting the penetration rate of percussive drills

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.     

Determination of mechanical properties of rocks using simple methods

Statistical equations have been determined for estimating the mechanical properties of rocks using non-destructive and indirect test methods. Nineteen different rock types were tested to obtain the relationships between Shore hardness, point load index, sound velocity, Schmidt hardness and porosity and uniaxial compressive strength, indirect tensile strength and abrasion resistance. Results of regression analyses showed satisfactory correlations.      

Index properties of weathered rocks: inter-relationships and applicability

 The paper describes the change in physical and strength properties due to weathering of three crystalline rocks – granite, basalt and quartzite. It draws attention to the relationship between unconfined compressive strength and other measurements such as the point load index, the Brazilian tensile strength and the Schmidt hammer rebound number. The strength recorded is negatively related to the porosity which is considered an important indicator of the weathering state. Received: 13 December 1997 · Accepted: 30 April 1998     

Predicting uniaxial compressive strength,modulus of elasticity and index properties of rocks using the Schmidt hammer

The Schmidt hammer test is a non-destructive method which can be used in both laboratory and field to provide a quick and relatively inexpensive measure of rock hardness. The study investigated the relationship between the Schmidt hardness and modulus of elasticity, uniaxial compressive strength and index properties of nine types of rock including travertine, limestone, dolomitic limestone and schist. The empirical equations developed indicated the Schmidt hardness rebound values have a reliable relationship with the uniaxial compressive strength of rock (r = 0.92). Comparing the results with those reported by other researchers, it is concluded that no single relationship can be considered reliable for all rock types. Whilst the equations developed in this study may be useful at a preliminary stage of design, they should be used with caution and only for the specified rock types.      

Prediction of mechanical behaviour from mineralogical composition of Sakesar limestone,Central Salt Range,Pakistan

Petrographic and mechanical properties of early Eocene Sakesar limestone have been investigated to establish the relationship between these parameters. Microscopic study revealed the presence of micrite (51.38%), sparite (12.90%), dolomite (12.95%), and allochems (20.88%) in the limestone samples. The strength parameters such as unconfined compressive strength (UCS), point load test (PLT), and Schmidt rebound hammer values (R _n ) were determined in the rock mechanics laboratory. Regression analyses were carried out to establish correlation between limestone constituents and the strength parameters. The UCS and other mechanical properties showed moderate inverse relationship with sparite and allochems, whereas micrite and dolomite indicate a positive correlation with UCS. To get significant correlations for cumulative micrite + dolomite and sparite + allochems, percentages and strength parameters were arranged in decreasing order. The fixed threshold for the cumulative values of micrite and dolomite were ≥80, 70–80, 60–70, 50–60 and <50%. Percentage of these constituents and the corresponding mechanical parameters were arranged on these thresholds. The cumulative modal constituents of the limestone were plotted against the mechanical parameters. Correlation among these values allowed developing equations for prediction of mechanical behaviour from mineralogical composition of Sakesar Limestone with more than 95% accuracy.     

Classification of geological and engineering properties in weak rock: a case study of a tunnel in a fault zone in southeastern Korea

Given that the rock mass classifications of weak rocks observed in tunnels are evaluated only as ‘poor rock mass’ or grades IV–V using existing rock mass classification methods, a new scheme is needed that would better distinguish the various geological properties of weak rocks. In this study, geological and engineering properties of weak rocks were classified based on the analysis results of a total of 55 faces in a tunnel that passes through a fault zone in southeastern South Korea. Geological observations, point load tests, and Schmidt hammer tests were conducted to analyze the properties of the weak rocks. Through this analysis, the weak rocks were classified into two weathering types: ‘disintegrated rocks’ and ‘decomposed rocks’. This division is based on the tectonic mechanisms and parameters necessary to determine the engineering geological properties of individual rock-weathering types according to their geological properties. The ‘disintegrated rocks’ have been physically weathered by brittle deformation and are classified into three subtypes using the rock quality designation (RQD) and joint set number (J_n), which can characterize the discontinuity properties of the rocks. Point load tests were conducted on these individual subtypes to calculate the point load index (Is₍₅₀₎). The resultant values are clearly related to the assigned three subtypes. The ‘decomposed rocks’ have been chemically weathered by ductile deformation and are classified into five subtypes based on the results of Schmidt hammer tests conducted on faces and Is₍₅₀₎ values calculated using the average of the Schmidt hammer values. The geological properties of the individual subtypes of the ‘disintegrated rocks’ and ‘decomposed rocks’ are clearly related to their engineering properties. Based on these results, rock mass classification diagrams are proposed that can be simply and easily applied to weak rocks.

     

Investigation of engineering properties for usability of Lefke stone (Osmaneli/Bilecik) as building stone

Lefke stone is a sandstone that has been widely used in mosques, madrasas, churches, and houses as building stone. The geological features and engineering properties of Lefke stone outcropped in the southern part of Osmaneli/Bilecik were investigated in field and laboratory studies. Samples acquired during the fieldwork were tested to determine the physical, mechanical, durability, and hygrothermal properties in the laboratory. The mean physico-mechanical properties of Lefke stone yielded apparent density of 2.38 g/cm³, specific gravity of 2.68 g/cm³, total porosity of 11.26%, 2.93% water absorption by weight, uniaxial compressive strength of 94 MPa, flexure strength of 11.45 MPa, a 3.90 MPa point load strength, 4.5–5 Mohs hardness, and field Schmidt hammer rebound value of 36. According to durability tests, Lefke stone is resistant to CaCl₂ salt mist but has low resistance to SO₂ aging. Salt crystals placed in the discontinuities of the rock caused slight crack growth. The stone’s resistance to crystallization of sodium sulphate salt is low, and an increase in the volume of salts crystallized in the rock results in low corner strengths. A capillary water-absorption value of 0.0016 kg/m².h places Lefke stone into the category of very low water absorption capacity and permeability. The water vapor diffusion resistance factor (μ) less than 1 indicates that the sandstone has high breathability. Its performance in historical buildings, field observations, and values obtained through laboratory tests confirm that Lefke sandstone can be used as a building stone.

     

The influence of mineralogical textural and chemical characteristics on the durability of selected sandstones in Istanbul, Turkey

 The paper describes the analyses and geotechnical testing of sandstones taken from a road cutting to the north east of Istanbul, Turkey. Samples were carefully selected in the field in order to obtain material representative of the complete weathering profile. Although unconfined compressive strength, point load index values and Schmidt hammer rebound numbers were obtained, the slake durability test provided the closest correlation with weathering grade. Received: 4 February 1998 · Accepted: 15 June 1998     

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

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, I_s(50) and the degree of weathering. Sixty three samples of gabbro and thirty of basalt from the ophiolitic comlex 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.     

Evaluation of empirical estimation of uniaxial compressive strength of rock using measurements from index and physical tests

The uniaxial compressive strength(UCS) of rock is an important parameter required for design and analysis of rock structures,and rock mass classification.Uniaxial compression test is the direct method to obtain the UCS values.However,these tests are generally tedious,time-consuming,expensive,and sometimes impossible to perform due to difficult rock conditions.Therefore,several empirical equations have been developed to estimate the UCS from results of index and physical tests of rock.Nevertheless,numerous empirical models available in the literature often make it difficult for mining engineers to decide which empirical equation provides the most reliable estimate of UCS.This study evaluates estimation of UCS of rocks from several empirical equations.The study uses data of point load strength(Is(50)),Schmidt rebound hardness(SRH),block punch index(BPI),effective porosity(n) and density(ρ)as inputs to empirically estimate the UCS.The estimated UCS values from empirical equations are compared with experimentally obtained or measured UCS values,using statistical analyses.It shows that the reliability of UCS estimated from empirical equations depends on the quality of data used to develop the equations,type of input data used in the equations,and the quality of input data from index or physical tests.The results show that the point load strength(Is(50)) is the most reliable index for estimating UCS among the five types of tests evaluated.Because of type-specific nature of rock,restricting the use of empirical equations to the similar rock types for which they are developed is one of the measures to ensure satisfactory prediction performance of empirical equations.     

A new testing method for indirect determination of the unconfined compressive strength of rocks

A new testing method for the indirect determination of unconfined compressive strength (UCS) of rock core samples is presented. As known, there exist several methods for indirect estimation of UCS, such as point load index (I_s), Schmidt hammer, sonic velocity, block punch strength test, etc. Although the point load index testing method is widely used to estimate UCS, there are many problems and limitations related to this method as reported in the recent literature. The “core strangle test” (CST) proposed in this paper overcomes some of these deficiencies and limitations. The principle of this test depends on the “strangle” type of loading a core along a circle perpendicular to the core axis. In the first stage of this study, blocks of different types of rocks having the strength in a range from weak to strong were collected and cored for UCS, point load index and CST tests. These tests were then conducted and relationships between UCS with I_s(50) and CST were empirically explained and discussed.     

Seasonal variation and impact factors of available phosphorus in typical paddy soils of Taihu Lake region,China

Phosphorus loss from soil can play an important role in eutrophication of aquatic bodies. The seasonal variation of available phosphorus in soil profiles of three major paddy soils (Bai soil, Huangni soil and Wushan soil) during wheat and rice growth seasons was studied in the Taihu Lake region of China. The results were as follows: the available phosphorus contents differed in the three paddy soils. Available phosphorus content in Bai soil was the lowest in these soils. The available phosphorus content decreases rapidly with depth from the soil surface and reach the minimum value at approximately 45 cm before increasing slightly near the groundwater. The contents of available phosphorus were higher in February (tillering and shooting period of wheat) and in September (full heading time of rice) than in other months. The total phosphorus content strongly affects available phosphorus content in the studied soils. During the period of wheat cultivation, they show a typical power function relationship with correlation coefficient r = 0.6492** (n = 13), a significant positive linear correlation. In addition, available phosphorus content has a remarkable positive linear correlation with organic matter content, r = 0.9111** (n = 13), and a remarkable negative linear correlation with pH value, r = ?0.5945* (n = 13). In Wushan soil, there is a negative linear correlation between clay content and available phosphorus content, r = ?0.9289* (n = 4). Therefore, total phosphorus content, organic matter content and pH value are major impact factors on available phosphorus content in these soils.     

Estimation of strength and deformation properties of Quaternary caliche deposits

The aim of this study was to develop and evaluate statistical models for predicting the uniaxial compressive strength (UCS) and average Young’s modulus (E _av) for caliches, using some index and physical properties. The caliche samples, from Adana, southern Turkey, were of low strength and difficult to sample. X-ray diffraction and microscopy were undertaken and the following physical parameters established: unit weight, apparent porosity, Schmidt rebound number, Shore hardness, P-wave velocity, slake durability, point load, uniaxial compressive strength and average Young’s modulus. Simple and linear regression variable selection analyses were performed. The best relationships were obtained for UCS with P-wave velocity and unit weight and for average Young’s modulus with P-wave velocity, porosity and slake durability. Empirical equations are proposed, although it is emphasised that these may only be applicable for caliche of a similar geological character.