A correlation between Schmidt hammer rebound numbers with impact strength index,slake durability index and P-wave velocity

The main objective of this study was to establish statistical relationship between Schmidt hammer rebound numbers with impact strength index (ISI), slake durability index (SDI) and P-wave velocity. These are important properties to characterize a rock mass and are being widely used in geological and geotechnical engineering. Due to its importance, Schmidt hammer rebound number is considered as one of the most important property for the determination of other properties, like ISI, SDI and P-wave velocity. Determination of these properties in the laboratory is time consuming and tedious as well as requiring expertise, whereas Schmidt hammer rebound number can be easily obtained on site which in addition is non-destructive. So, in this study, an attempt has been made to determine these index properties in the laboratory and each index property was correlated with Schmidt hammer rebound values. Empirical equations have been developed to predict ISI, SDI and P-wave velocity using rebound values. It was found that Schmidt hammer rebound number shows linear relation with ISI and SDI, whereas exponential relation with P-wave velocity. To check the sensitivity of empirical relations, Student’s t test was done to verify the correlation between rebound values and other rock index properties.     

Correlation of Schmidt hardness with unconfined compressive strength and Young''s modulus in gypsum from Sivas (Turkey)

This study aims to express the relationships between Schmidt rebound number (N) with unconfined compressive strength (UCS) and Young's modulus (E_t) of the gypsum by empirical equations. As known, the Schmidt hammer has been used worldwide as an index test for a quick rock strength and deformability characterisation due to its rapidity and easiness in execution, simplicity, portability, low cost and nondestructiveness. In this study, gypsum samples have been collected from various locations in the Miocene-aged gypsum of Sivas Basin and tested. The tests include the determination of Schmidt hammer rebound number (N), tangent Young's modulus (E_t) and unconfined compressive strength. Finally, obtained parameters were correlated and regression equations were established among Schmidt hammer rebound hardness, tangent Young's modulus and unconfined compressive strength, presenting high coefficients of correlation. It appears that there is a possibility of estimating unconfined compressive strength and Young's modulus of gypsum, from their Schmidt hammer rebound number by using the proposed empirical relationships of UCS=exp(0.818+0.059N) and E_t=exp(1.146+0.054N). However, the equations must be used only for the gypsum with an acceptable accuracy, especially at the preliminary stage of designing a structure. Finally, by using the obtained Schmidt hammer rebound number from this study, unconfined compressive strength was calculated and compared with the calculated value from different empirical equations proposed by different authors. It can be said that it is impossible to obtain only one relation for all types of the rocks.     

施密特锤试验数据处理方法及其在预估岩石可钻性中的应用

本文目的在于寻求一种可靠的施密特锤数据处理方法,并探讨其用于岩石可钻性预估中的可能性。试验选择了HT100和HT225两种施密特锤,配3种冲杆(R25,R6.0和R4.5)组成了4种测定方案,在多种岩石中进行了测试。利用数理统计方法和灰色系统理论对数据的分布特征进行了分析,并提出:施密特锤试验的合理冲击点数是15点,每点至少冲击5次,舍去前两次回弹值,取15个冲击点后3次回弹平均值作为试验结果。 同时,还对回弹值和风动凿岩帆钻速V进行了回归分析,结果表明两者之间存在着良好的相关关系(在α=0.01水平上通过了F检验),据此提出了以回弹值预估凤动凿岩机钻速的计算公式。     

The Schmidt hammer in rock material characterization

The Schmidt hammer provides a quick and inexpensive measure of surface hardness that is widely used for estimating the mechanical properties of rock material. However, a number of issues such as hammer type, normalization of rebound values, specimen dimensions, surface smoothness, weathering and moisture content, and testing, data reduction and analysis procedures continue to influence the consistency and reliability of the Schmidt hammer test results. This paper presents: a) a critical review of these basic issues; and b) the results of tests conducted on granitic rocks of various weathering grades in the light of the conclusions of this review. It was found that a very good correlation exists between L and N hammer rebound values and that both hammers are fairly sensitive to the physical properties, particularly to dry density though less so to effective and total porosities. The N hammer, producing a lesser scatter in the data, proved to be more efficient than the L hammer in predicting uniaxial compressive strength and Young's modulus. The exponential form of the correlation curves was found to reflect microstructural changes during the course of weathering and the differences in the probing scales or mechanisms in the means of measuring these mechanical properties, and could be generalized to other crystalline igneous rocks. The possibility of predicting weathering grades from rebound values was also explored. The changes in the rebound values during multiple impacts at a given point produced a better indication of the weathering grade than a single impact value. It was concluded that increasing the impact energy and plunger tip diameter should significantly reduce the scatter in coarse-grained weathered rocks and hence improve the reliability of the Schmidt hammer as a rock material characterization tool.     

Fuzzy and Multiple Regression Modelling for Evaluation of Intact Rock Strength Based on Point Load, Schmidt Hammer and Sonic Velocity

Summary. Uniaxial Compressive Strength (UCS), considered to be one of the most useful rock properties for mining and civil engineering applications, has been estimated from some index test results by fuzzy and multiple regression modelling. Laboratory investigations including Uniaxial Compressive Strength (UCS), Point Load Index test (PL), Schmidt Hammer Hardness test (SHR) and Sonic velocity (V_p) test have been carried out on nine different rock types yielding to 305 tested specimens in total. Average values along with the standard deviations (Stdev) as well as Coefficients of variation (CoV) have been calculated for each rock type. Having constructed the Mamdani Fuzzy algorithm, UCS of intact rock samples was then predicted using a data driven fuzzy model. The predicted values derived from fuzzy model were compared with multi-linear statistical model. Comparison proved that the best model predictions have been achieved by fuzzy modelling in contrast to multi-linear statistical modelling. As a result, the developed fuzzy model based on point load, Schmidt hammer and sonic velocity can be used as a tool to predict UCS of intact rocks.     

多参数液动潜孔锤测试平台的研究

液动冲击回转钻进技术现已广泛应用于地质勘探领域,但在石油、地热、煤层气等其他钻井领域应用还较少。原因之一是现有的液动潜孔锤正常工作所需泵量和泵压与输出冲击功和冲击频率难以适应上述钻井领域的要求。针对这一问题,分析了冲击功与冲击力的关系,利用压电石英传感器测定液动潜孔锤的冲击功,并研制了多参数液动潜孔锤测试平台,探索液动潜孔锤结构参数对其输入、输出性能参数的影响,以适应不同领域钻井技术的要求。新研制的液动潜孔锤测试平台由数据采集和处理模块、循环动力模块和机械固定模块3个主要模块组成,实现了在尽可能不破坏液动锤结构的前提下对其输出冲击功、冲击频率及泵量、上下腔压力、背压等多个参数进行实时动态监测,进而开展液动潜孔锤理论研究,进一步提高其研究水平和适用领域。     

潜孔锤技术在三道庄钼矿采空区探测中的应用

结合高风压潜孔锤钻进技术在洛阳栾川钼业集团三道庄钼矿区采空区探测中的应用,介绍了高风压潜孔锤技术钻进塌陷区、穿越采空区施工技术。应用高风压潜孔锤钻进技术在洛钼集团三道庄钼矿进行采空区探测,摸索出了相应的钻进工艺方法,大幅度提高了成孔率,对同类型矿山采空区勘探具有参考意义。     

潜孔锤在鄂西找水勘察施工中的应用效果

为了尽快解决湖北恩施自治州部分乡镇缺水问题，我院连续4年投入少量找水勘察任务，使用空气潜孔锤钻进，取代传统岩心钻探方法，加快了勘察施工速度，积累了经验，为今后使用潜孔锤在基岩地层找水成井施工打下了基础。     

A Comparative Analysis of Cognitive Systems for the Prediction of Drillability of Rocks and Wear Factor

This paper demonstrates the applicability of cognitive systems or neural networks in predicting the drillibality of rocks and wear factor using engineering properties of rocks. Drillability of rocks is a useful guide for evaluating the suitability of drills for different ground operations. The wear factor of different materials subsequently helps in the selection of proper drills for different drilling operations. Different rocks were tested for Protodyakonov index, impact strength index, shore hardness number, Schmidt hammer number, drillability and micro bit chisels for wear factor. The data obtained from the tests were used to train and test the neural network. Results from the analysis demonstrate that cognitive systems are an effective tool in the prediction and suitability of drilling operations. Application of these predictive models can be a useful tool to obtain the value of these important parameters, they can save time and help to avoid the tedious process of instrumentation.     

TK系列液动冲击回转钻具的研制及推广应用

介绍了ＴＫ－Ａ系列正作用液动液击器和ＴＫ－Ｓ系列绳索取心冲击回转具的技术原理、主要技术性能参数及推广应用情况。     

Black crusts on travertine: factors controlling development and stability

The travertine buildings of Budapest show extensive black crust formation, which is related to high concentration of atmospheric pollution and a continental climate. Laminar black crusts, framboidal black crusts and leached white surfaces are compared. Physical properties (Schmidt hammer rebound, Duroscope rebound), mineralogical composition and elemental composition are measured. Framboidal black crusts contain more than 50% of acicular gypsum. The crust surface displays idiomorphic rosette-like gypsum crystals with particulates, calcite and gypsum crystal aggregates. The sulphur isotopic composition of the black crusts pinpoints the involvement of rain and dust in crust formation. Thick framboidal black crust has the lowest strength while thin laminar black crust and white dissolved surfaces show minor decrease in surface strength compared to unaltered travertine. The crusts adhere to the travertine surface and rarely show mechanical decay forms that are typical features of porous limestone ashlars in Budapest.     

Weathering of surface clasts as an indicator of the relative age of glacial deposits on Jameson Land, East Greenland

The relative age of glacial deposits on Jameson Land was investigated by weathering-based techniques. Two related methods, measurement of rind thickness and of Schmidt hammer rebound values. were added to a dating programme of luminescence-, amino acid- and ¹⁴C-analyses. Rind thicknesses differ significantly between areas which represent three glacial phascs, spanning a time interval from late Saale to Late Weichselian. Rebound values are more susceptible to external factors than the rind values but may, if these external factors are known, serve as a complement to the interpretation of rind development.     

Evaluation of rock mechanical behaviors under uniaxial compression with reference to assessed weathering grades

Summary  A weathering classification for granitic rock materials from southeastern Brazil was framed based on core characteristics. The classification was substantiated by a detailed petrographic study. Indirect assessment of weathering grades by density, ultrasonic and Schmidt hammer index tests was performed. Rebound values due to Schmidt hammer multiple impacts at one representative point were more efficient in predicting weathering grades than averaged single impact rebound values, P-wave velocities and densities. Uniaxial compression tests revealed that a large range of uniaxial compressive strength (214–153 MPa) exists in Grade I category where weathering does not seem to have played any role. It was concluded that variability in occurrences of quartz intragranular cracks and in biotite percentage, distribution and orientation might have played a key role in accelerating or decelerating the failure processes of the Grade I specimens. Deterioration of uniaxial compressive strength and elastic modulus and increase in Poisson’s ratio with increasing weathering intensity could be attributed to alteration of minerals, disruption of rock skeleton and microcrack augmentation. A crude relation between failure modes and weathering grades also emerged. Correspondence: Prof. T. B. Celestino, Universidade de S?o Paulo, S?o Carlos, Brazil     

First attempt to combine terrestrial cosmogenic nuclide (10Be) and Schmidt hammer relative-age dating: Strauchon Glacier, Southern Alps, New Zealand

This study provides the first attempt to combine terrestrial (in situ) cosmogenic nuclide (¹⁰Be) surface exposure dating with Schmidt hammer relative-age dating for the age estimation of Holocene moraines at Strauchon Glacier, Southern Alps, New Zealand. Numerous Schmidt hammer tests enable a multi-ridged lateral moraine system to be related to three late-Holocene ‘Little Ice Age’-type events. On the basis of cosmogenic ¹⁰Be ages, those events are dated to c. 2400, 1700, and 1100 years ago. Linear age-calibration curves are constructed in order to relate Schmidt hammer R-values to cosmogenic ¹⁰Be ages. The high explanation yielded reveals the causal link between both data sets. The potential of combining both methods in a ‘’multiproxy approach’ is discussed alongside possible future improvements. Terrestrial cosmogenic nuclide dating delivers absolute ages needed as fixed points for Schmidt hammer age-calibration curves. The Schmidt hammer technique can be used to crosscheck the boulder surfaces chosen for surface exposure dating by terrestrial cosmogenic nuclides. It should, therefore, reduce the number of samples necessary and costs.     

冲击回转碎岩机理试验研究

在模拟孔底冲击回转钻进条件的试验台上，对岩石的冲击回转碎岩机理进行了试验研究，提出了大直径潜孔钻头的合理布齿及钻进参数选择依据。     

The status of the 'Little Ice Age' in southern Norway: relative-age dating of Neoglacial moraines with Schmidt hammer and lichenometry

A Schmidt hammer was used in conjunction with lichenometry to examine the relative age of the outermost Neoglacial moraines in front of glaciers in the Jotunheimen mountains of southern Norway. Particular attention was directed at (1) the magnitude of the 'Little Ice Age' glacier expansion episode relative to any others of Neoglacial age, and (2) the potential and limitations of the Schmidt hammer in the context of Holocene glacial chronologies. Schmidt hammer R-values were measured at 34 glaciers and the sizes of the lichen Rhizocarpon geographicum agg. at 80 glaciers. Unusually low R-values and large lichens suggest the occurrence of pre- 'Little lee Age' Neoglacial moraines at only a small minority (< 10 %) of the sampled glaciers. The traditional model of relatively large southern Norwegian glaciers during the 'Little Ice Age' is substantiated and it is tentatively suggested that differences in climate or glacier type may account for a regional difference in the status of the 'Little Ice Age' between northern and southern Scandinavia. The incorporation of weathered boulders into 'Little Ice Age' moraines by glacier push mechanisms, and the altitudinally-related variation in boulder surface textures, are identified as major sources of potential error in the use of the Schmidt hammer R-values for relative-age determination of Neoglacial surfaces.     

基于CFD的高能射流式液动冲击器活塞与缸体密封特性研究

通过计算流体动力学分析与实验室测试,对SC-86H型高能射流式液动冲击器活塞与缸体密封特性进行研究,分析了活塞密封段长度、环状间隙尺寸、活塞往复运动速度、角速度以及活塞外表面螺旋槽螺距与半径等参数对射流式冲击器前后腔之间泄漏量的影响。结果表明:活塞密封段长度、环状间隙尺寸、角速度以及活塞表面螺旋槽螺距均对射流式液动冲击器性能影响较小;活塞运动速度与泄漏量近似成正比例关系;随着活塞螺旋槽半径的增大,泄漏量会明显增大。活塞回程与冲程初期阶段,活塞运动速度较小,活塞处瞬时泄漏量占进入缸体前后腔流体流量的比例较大,使活塞无法快速加速运动,尤其是当活塞杆直径较大时,回程阶段泄漏量对活塞运动的影响更显著,导致冲击器工作性能大幅下降,甚至无法工作。     

对国产旋挖钻机研制选型的几点意见

在分析旋挖钻机研制的首期市场目标和国外旋挖钻机特点的基础上，对国产钻机研制的选型、主要工艺技术参数及井下工器具配套提出了几点意见。     

Application of statistical methods for predicting uniaxial compressive strength of limestone rocks using nondestructive tests

Uniaxial compressive strength (UCS) of an intact rock is an important geotechnical parameter for engineering applications. Using standard laboratory tests to determine UCS is a difficult, expensive and time-consuming task. The main purpose of this study is to develop a general model for predicting UCS of limestone samples and to investigate the relationships among UCS, Schmidt hammer rebound and P-wave velocity (V _P). For this reason, some samples of limestone rocks were collected from the southwestern Iran. In order to evaluate a correlation, the measured and predicted values were examined utilizing simple and multivariate regression techniques. In order to check the performance of the proposed equation, coefficient of determination (R ²), root-mean-square error, mean absolute percentage error, variance accounts for (VAF %), Akaike Information Criterion and performance index were determined. The results showed that the proposed equation by multivariate regression could be applied effectively to predict UCS from its combinations, i.e., ultrasonic pulse velocity and Schmidt hammer hardness. The results also showed that considering high prediction performance of the models developed, they can be used to perform preliminary stages of rock engineering assessments. It was evident that such prediction studies not only provide some practical tools but also contribute to better understanding of the main controlling index parameters of UCS of rocks.