Rock Mechanics

The geometry and sedimentology of 49 talus slope deposits have been analysed in the French Alps to show the effects of snow avalanche activity on their characteristics. Twenty slopes are heavily avalanche-modified, 15 are snow-avalanche boulder tongues and 14 are rockfall-talus slopes. Slope angle, slope segmentation, longitudinal and sorting indices provide criteria to differentiate these deposits. Although the transition from rockfall-to avalanche-dominated slopes is gradational, a Atransitional talusB is identified with distinctive characteristics. q

... According to the results of Prikryl (2001), with increasing porosity UCS decreases logarithmically ... authors gratefully acknowledges the Hungarian Natural Research Foundation support (Grant numbers: OTKA T034603 and OTKA F 043291) and they thank Dr. I. Marek for carrying ...

Digital geoinformation for the surface and subsurface is virtually never integrated in civil engineering projects. Reasons are that the surface information is gathered by different person’s and that the subsurface information is in different formats from the surface information. Likelihood and uncertainty of subsurface models is not quantifiable. To quantify the likelihood and correctness of the subsurface information the civil engineer would have to have full access to the original data, which is not available due to the none integration of the data. In the last 10 years considerable progress has been made in use of geographic information systems but the progress in the integration of data and the addressing of likelihood of subsurface data is limited.

Compressive strength is an essential engineering parameter employed in civil and mining engineering operations. Often, uniaxial compressive strength (UCS) and point load index (Is 50) are linked for simplicity in assessing rock properties during preparatory design stage. However, a number of researches have been conducted to establish relationship between these two parameters for various rock types but few have been centered on rock strength classifications. This research focuses on using regression analysis to establish correlation factor(s) for different strength groups based on modified Rock Mass Classification Scheme for Banket conglomerates within the Tarkwaian Deposit of Ghana. The rocks were classified into strong, medium and weak group based on their strength threshold. Quantitative analysis of the strength states revealed that, the higher the strength value of the rock the higher the correlation factor. The correlation analysis disclosed a good linear relationship between the two parameters for the grouped rock strengths. The established correlation factors (k) between UCS and Is 50 for strong, medium and weak rock group

The turning of hardened steels has been applied in many cases in production. It is an important process because all manufacturers are continu¬ally seeking ways to manufacture their parts with lower cost, higher quality, rapid setups, lower investment, and smaller tooling inventory while eliminating non-value added activities. Currently, the most important problem is concerned with the properties of the surface finish. This paper investigates the effect on surface finish and tool wear in a continuous dry turning of hardened steel when using a ceramic wiper tools. This report describes about the hard turning of AISI 4340 alloy steel by varying various parameters. The hard turning parameters are: Cutting speed, Feed and Depth of cut. The main objectives of this project, study the effect of parameters such as cutting speed, feed, depth of cut on surface roughness, tool wear and cutting force during the hard turning of AISI 4340alloy steel using ceramic wiper tool and the effect of various process parameters on hard tuning and optimize the cutting parameters. The dry turning experiments were performed on hardened AISI 4340 steel material using ceramic wiper tool .AISI 4340 steel having hardness: 48 (48–52) HRC was used.

Keywords— Hard turning, surface roughness, taguchi’s method.

In any project, especially infrastructure ones such as tunnels, tests play a major role in predicting and showing the properties of the ground built on. For such construction through a rock mountain terrain, it is quite not easy to predict the engineering property of such materials. Since working with rock is a quite challenge because of the nature of rock materials, it needs a lot of care and persuasion when dealing with such. For such rock materials, it needs both of field and laboratory tests to ensure the process of obtaining the final engineering property of the materials. This paper concentrate on some of the laboratory tests required for tunnel project held in rock profile sites. Emphasizing on safety, accuracy that enquired during such tests and try to run those under risk management process by means of AHP to get the responded weights for those factors such as test procedure with average of weight (49.43%) indicates the caution to be taken during test beside major parameter...

В диссертационной работе решена актуальная научно-техническая задача прогнозирования проявлений горного давления при проведении выработки и адаптации параметров крепи к изменчивым геомеханическим процессам. В результате анализа состояния горных выработок и методов прогнозирования проявлений горного давления установлено, что выработки проектируют и сооружают в условиях неполной геомеханической информации, поэтому принимаемые решения по их креплению не всегда рациональны, выработки обладают низкой эксплуатационной надежностью, а на их ремонт затрачиваются огромные средства. Усовершенствована комплексная методика шахтных наблюдений, включающая изучение анизотропии прочностных свойств пород, регистрацию смещений пород при помощи контурных и глубинных реперов, оценку нарушенности породного массива вокруг выработки с помощью модернизированного электроемкостного интроскопа. Проведены теоретические исследования зоны влияния выработки в неравнокомпонентном поле напряжений с учетом: критерия, по которому определяется её граница, и погрешности вычисления; исходного напряженного состояния породного массива; формы выработки; площади её поперечного сечения и соотношения высоты и ширины; ориентации выработки относительно направления действия главных напряжений в породном массиве; стадии развития и размеров зоны неупругих деформаций вокруг выработки. Доказано, что в пределах области достоверного моделирования методом конечных элементов площадь дополнительно напряженных элементов связана с площадью зоны разрушения вокруг выработки линейной зависимостью. При этом граничные условия соблюдаются при площади разрушения, которая не превышает 5% от площади расчетной модели, как для выработки круглой формы, так и квадратной (с углами). Дальнейшее увеличение площади разрушенных элементов ведет к потере устойчивости модели. Для установления вида функции влияния забоя решены пространственные упругие задачи о распределении напряжений вокруг выработки круглой и квадратной форм поперечного сечения. Эта функция является множителем к компонентам начального поля напряжений при решении псевдопространственной задачи и изменяется впереди забоя по нелинейной зависимости от 1 до 2, в плоскости забоя имеет скачок до 0,6, а позади забоя возрастает по экспоненте от 0,6 до 1. В результате моделирования зоны разрушения пород вокруг незакрепленной выработки установлено, что для всех форм поперечного сечения выработки зависимость относительной площади зоны разрушения от расстояния до забоя представляет собой нелинейную функцию, зависящую от относительного показателя прочности пород, обобщенного коэффициента бокового распора и реологического параметра и изменяющуюся от нуля в месте зарождения зоны разрушения до некоторого предельного значения, которое функция принимает на границе зоны влияния забоя, определяемой процессом перераспределения поля напряжений. В результате моделирования зоны разрушения пород вокруг выработки, в которой возводится адаптивная крепь с предварительным распором, установлено, что за счет уплотнения разрушенных пород можно уменьшить площадь зоны неупругих деформаций на границе зоны влияния забоя в 1,5-2,5 раза, причем зависимость этой площади от расстояния до забоя, на котором производится распор крепи, имеет минимум, учет которого позволяет объективно назначать рациональные параметры крепи и её распора. На основе установленных закономерностей разработан метод двухэтапного прогнозирования проявлений горного давления. Предварительный приблизительный прогноз реализуется на стадии проектирования выработки на основе неполной геомеханической информации. Текущий прогноз осуществляется при проведении выработки путем сочетания компьютерного моделирования и шахтных измерений. По результатам текущего прогноза корректируется при необходимости геомеханическая модель, устанавливается отсутствовавшая информация и адаптируются параметры крепи к изменчивым геомеханическим процессам.

Some instability problems of cutting slopes were found along the main road alignment between Bandung and Majalengka, which is mostly lying on high slaking claystones. The main objective of this paper is to establish the findings of the study devoted to some slope instability problems in the claystones due to their propensity to slaking at selected locations of these cutting slopes. The slope performance analysis made during a field survey has obtained a plot of slope angles versus slope heights for the average stable conditions of the existing road slopes, which were then combined with the laboratory experiments of slaking tests, resulting in a standard chart to be suggested as a physical-based model for the cutting slope design. Based on this chart, the optimum slope design can be estimated directly from the input of lithological characteristics determined by simple and inexpensive field and laboratory tests.

—The West Bohemian seismoactive region is situated near the contact of the Moldanu bian, Bohemian and Saxothuringian units in which a large volume is occupied by granitoid massifs. The spatial distribution of P-wave velocities and the rock fabric of five representative samples from these massifs were studied. The P-wave velocities were measured on spherical samples in 132 independent directions under hydrostatic pressure up to 400 MPa, using the pulse-transmission method. The pressure of 400 MPa corresponds to a depth of about 15 km in the area under study. The changes of P-wave velocity were correlated with the preferred orientations of the main rock fabric elements, i.e., rock forming minerals and microcracks. The values of the P-wave velocity from laboratory measurements on granite samples fit the velocity model used by seismologists in the West Bohemian seismoactive region.

The problem of bearing capacity of footings on rock is the subject of some researches in the recent years. However, the authors are not aware of any published paper about the effect of nearby footings on bearing capacity of rock foundations. This paper focuses on numerical analysis of the ultimate bearing capacity of two interfering strip footings resting on a rock mass, obeying the modified Hoek–Brown failure criterion. This criterion is applicable to intact rock or heavily jointed rock masses that can be considered homogeneous and isotropic. The rock mass was assumed to behave as a perfect plastic material and obeys an associated flow rule. The effects of Hoek–Brown parameters including geological strength index (GSI), material constant for intact rock (m i), and uniaxial compressive strength of intact rock (r ci), on the bearing capacity of multiple footings were studied. For different clear spacing between the footings (S), the ratio of the failure load for an interfering new footing to that of a single isolated footing were determined. The results were compared with those available in the literature.

This is a commentary on a paper about grooved markings found on sandstone surfaces in the Pennine upland of Yorkshire, United Kingdom, of other single examples in Scotland and the U.S.A., and of numerous unsuccessful attempts to secure an archaeological or geological explanation for them. The author explains the unexplained phenomenon.

The American Rock Mechanics Association (ARMA) and the ARMA Foundation sponsored a forum on New Directions for US Rock Mechanics which was held at the Asilomar Conference Center in Pacific Grove, California, USA, during 18–20 October 1998. The goal of the Forum was to focus on: (1) a strategic vision for the future of rock mechanics in the United States; (2) the identification and delineation of critical issues facing the rock mechanics community; (3) the role of research in addressing these issues; and (4) critical areas of research in each of the topic areas addressed at the forum including examples of specific research initiatives. To a large degree, rock mechanics has been used successfully to model and predict the behavior of fractured rock masses for building large structures. However, improvements on present success, and future advances in modeling and construction, are predicated on better characterization of fractured rock masses. This will require increasing emphasis on non-linear and discontinuity-based models to reflect the mechanisms at work in fractured rock masses. For example, relevant characterization schemes, as well as field, laboratory, and logging techniques have yet to be developed for weak rock conditions and for all but the simplest fluid flow conditions.This report summarizes two days of discussion held during the Forum. It was the sense of the Forum participants that fundamental improvements in in situ rock mass characterization is of the utmost importance. Every session emphasized that obtaining valid information from large volumes of rock is the prerequisite for the effective and improved practice of rock mechanics. Research and application of remote imaging and non-destructive evaluation of the subsurface should provide a source of economically realizable data from large volumes of rock. This area should be a primary goal of future research.Associated with the question of site characterization is the degree of uncertainty associated with the data, and with the chosen interpretive model. Forum participants also recommended conducting research to find implementations of stochastic techniques, which would allow uncertainty to be dealt with in a rational manner.

The main objective of this study is to investigate the strength characteristics of Warukin Formation and suggest how to apply these results in the mining process. The study area is located in East Kalimantan of Indonesia. It consists mainly of Middle-Late Miocene sedimentary rocks of Warukin Formation. In order to characterize the rock strength, we conducted Uniaxial Compressive Strength (UCS) test respectively for 1,096 times. The average UCS of mudstone, sandstone, coal and limestone, respectively, are 3.1 MPa, 4.8 MPa, 10.6 MPa and 35.7 MPa and the average Young's Modulus () are 0.4 GPa, 1.0 GPa, 1.4 GPa and 20.7 GPa, respectively. The average UCS and of lignite, respectively, are 9.7 MPa (SD 4.0 MPa) and 0.87 GPa (SD 0.28 GPa). The average UCS and of sub-bituminous coal are 11.5 MPa (SD 5.5 MPa) and 1.80 GPa (SD 0.40 GPa), respectively. But though in the same area, UCS of sandstone and mudstone have large standard deviations. So there is a problem to use the average value as a representative value. Therefore, we have studied the relationship not only between the Needle Penetration Index (NPI) with UCS but also with. Needle Penetration Test (NPT) was conducted for 416 times. The empirical prediction equations of this study are as follows: Log UCS (kPa) = 1.089*log NPI + 2.178 (N/mm), R=85.1% Log (MPa) = 1.375*log NPI + 0.915 (N/mm), R=87.0% We have analyzed 2,472 blasting vibration data for 9 years and finally we find out that blasting vibration can be reduced based on rock strength characteristics which can be measured In-pit by NPT with suggested the empirical equations.

Use of drilled disc specimens was investigated with both numerical and experimental studies to determine direct tensile strengths of rock materials. A new loading apparatus with rods to insert into the drill holes of discs has been designed and manufactured to supply tension by using the compression test presses. In addition to the use of popular compressive presses for direct tension, elimination of the gluing in the standard direct tensile strength test method is a significant advantage to make possible both hard and soft rocks to be tested. The Brazilian test discs with the diameter of NX size and length to diameter ratio of 0.5 were used in tests. Different loading apparatus designs were analyzed and ideal angle of contact between rock and the loading rods was assessed to be 50° within various choices investigated in this study. The drilled discs were determined to fail due to the crack initiation under the condition of uniaxial tensile stress distribution at sidewalls of the hole. In addition to the drilled disc tension test, standard direct tensile strength tests were also carried out to take as reference and compare the results obtained from different methods. According to the results of both numerical and experimental studies, an equation was suggested to determine uniaxial tensile strengths of drilled disc specimens with 20 mm hole diameter and the contact angle of 50°.

This paper presents an assessment study conducted to investigate the structural condition of a drainage shaft that is part of a very large aqueduct system located in the Northeastern United States. A comprehensive three-dimensional finite-element model was generated to simulate the hydrostatic uplift pressures the shaft is subjected to. The behavior of the steel shaft cover, anchor rods, other connecting elements, and the surrounding granite rock stratum are analyzed. The finite-element model covers a large cylindrical region with a radius of 32 m around the shaft centerline to a depth of 15.2 m. The rock material was modeled on the Drucker-Prager failure criterion since the von Mises criterion is not perfectly suited for modeling the yielding of a frictional material like granite rock. A condition assessment study like the one described in this paper required an extensive finite-element model created with comprehensive software like ANSYS to investigate the load and stress distribution of uplift forces through the elements of the shaft to ensure structural integrity. The special features of ANSYS SOLID185 elements are a good fit for the simulation of the nearly incompressible rock stratum of this study. SOLID185 elements with advanced capabilities such as fracture parameter calculations, stress stiffening, creep, nonlinear stabilization, and linear perturbation are used to model the rock. Since a structural condition assessment of a drainage shaft modeled with ANSYS SOLID185 finite elements have not been discussed in detail in a technical publication before, this paper fills that gap.

Convergence-confinement method can be used to analyze rock support systems in interaction with rock mass in order to select the appropriate supports system for tunnels in rock. This method enables calculation of the charge applied to the support system and the factor of safety for the tunnel supports. The factor of safety calculated from traditional deterministic analysis methods cannot fully represent tunnel stability. There are many uncertainties in parameters used to calculate the factor of safety, and these uncertainties are not integrated in a deterministic analysis, but can be taken into account using a reliability analysis. Reliability analyses, used to calculate probability of failure for tunnel support system, is a complement of the factor of safety calculated by using deterministic analyses. In this paper, Monte Carlo Simulation is used to calculate probability of failure for tunnel support system.

The strength of jointed rock mass is strongly controlled by the degree of interlock between its constituent rock blocks. The degree of interlock constrains the kinematic freedom of individual rock blocks to rotate and slide along the block forming joints. The HoekeBrown (HB) failure criterion and the geological strength index (GSI) were developed based on experiences from mine slopes and tunneling projects in moderately to poorly interlocked jointed rock masses. It has since then been demonstrated that the approach to estimate the HB strength parameters based on the GSI strength scaling equations (called the 'GSI strength equations') tends to underestimate the confined peak strength of highly interlocked jointed rock masses (i.e. GSI > 65), where the rock mass is often non-persistently jointed, and the intact rock blocks are strong and brittle. The estimation of the confined strength of such rock masses is relevant when designing mine pillars and abutments at great depths, where the confining pressure is high enough to prevent block rotation and free sliding on block boundaries. In this article, a grain-based distinct element modeling approach is used to simulate jointed rock masses of various degrees of interlock and to investigate the influences of block shape, joint persistence and joint surface condition on the confined peak strengths. The focus is on non-persistently jointed and blocky (persistently jointed) rock masses, consisting of hard and homogeneous rock blocks devoid of any strength degrading defects such as veins. The results from this investigation confirm that the GSI strength equations underestimate the confined strength of highly interlocked and non-persistently jointed rock masses. Moreover, the GSI strength equations are found to be valid to estimate the confined strength of persistently jointed rock masses with smooth and non-dilatant joint surfaces.