金刚石绳锯模拟切割反应堆重混凝土试验研究

金刚石绳锯是目前国外石材开采和锯切的新技术。采用金刚石串珠绳锯对两种组分不同的重混凝土进行了模拟切割试验。根据试验结果表明:在反应堆退役过程中,推荐采用金刚石串珠绳锯对密度较小,内含金属较少的重混凝土实施拆除解体。     

An experimental research on the rock cutting process of the gage cutters for rock tunnel boring machine (TBM)

This paper proposed an experimental method to investigate the rock cutting process of TBM gage cutters based on the full-scale rotary cutting machine (RCM). The key point of this method is to reconstruct the RCM by inserting three wedges with angles of 10°, 20° and 30° respectively into the space between the cutter base and cutter box. As a result, the rock cutting process of gage cutters with tilt angles of 10°, 20° and 30° can be proceed. Using this method, rock cutting experiments were conducted with penetrations of 2 mm, 4 mm, 6 mm and 8 mm respectively. The testing results were analysed on the rock cutting force, rock debris dimension, specific energy and cutting surface profile, and it was found that: (1) the cutting forces and specific energy of the gage cutter were lower than those of the normal cutter respectively; and (2) the depth of the rock broken zone was smaller than the cutting depth. The testing results can also be used to validate corresponding numerical models and design the layout of gage cutters.     

Predicting performance of EPB TBMs by using a stochastic model implemented into a deterministic model

The current study is an attempt to address the stochastic nature of the rock excavation process by suggesting a stochastic performance prediction model implemented into a deterministic model developed for hard rock TBMs. Full-scale linear cutting experiments using constant cross-section and V-type of disc cutters are performed on two different limestone samples to provide the basic input required for the deterministic model used for estimation of instantaneous penetration rate, daily advance rate, thrust and torque requirements of TBMs. Stochastic estimation is performed by using a Monte Carlo simulation program by applying iterations to implement the probabilistic distribution of each model parameter and provide knowledge of a confidence level. Results of the suggested model are verified by measuring the field performance of two earth pressure balance (EPB) TBMs excavating competent rocks in semi-closed mode. The results indicate that the suggested model works well for prediction of instantaneous cutting/penetration rate for both TBMs and both types of disc cutters. However, an improvement on the model is required for estimation of cutterhead torque and thrust of EPB TBMs. The stochastic model implemented into the deterministic model results in almost similar predictions with the deterministic model in 50% (best guess) probability. However, the stochastic modeling provides a tool for exploring the full implications of linear cutting experiments and allows assessing the probability of occurrence and predicting variations of the TBM performance parameters, covering the uncertainties/risks.     

A Study of nozzle angle in stone surface treatment with water jets

The stone surface treatment with water jet is a recently introduced method. It is used to increase the roughness to improve its antislip properties while preserving esthetic appearance of the stone without having thermal shock, mechanical stress and the production of fumes and dust. Nozzle angle is one of the important parameters affecting treatment of surface. This study is an attempt to assess the effect of nozzle angle on surface treatment quality with water jet and to determine the most suitable nozzle angle value. For this purpose, surfaces of Sardinian Basalt samples are treated with pure water jet in six different nozzle angles (15°, 30°, 45°, 60°, 75° and 90°). The roughness is measured on all the treated surfaces by various roughness parameters. The experimental studies showed that treatment with nozzle angle between 30° and 75° gives the surfaces with similar regular variation.     

Kaiser取样偏差对深层油藏地应力测试的 影响分析

 采用Kaiser效应测定深部地层地应力时,由于油藏岩芯不规则及试件制备过程的误差等因素存在,取样时的偏差会影响地应力测量。假定0°方位和90°方位的取样方位准确而45°方位取样存在一定偏差,根据弹性力学和级数展开建立了应力测量误差分析的力学模型。采用深层均质砂岩岩芯,并变化取心角度(偏差)进行一系列Kaiser 效应试验,对比试验和小型压裂解释结果发现 Kaiser岩样偏差对地应力数值确实存在影响,其关系为二次函数;当取样偏差角度在5°以内时,应力测试误差可以忽略不计;大于5°时引起的地应力解释误差不能忽略。对于非定向钻取的全尺寸岩芯,当参考取样方位不同时,取样偏差的影响幅度不同。对于深部地层的不规则岩芯,可根据所建立的模型对Kaiser效应测试结果进行相应的误差分析。     

A development in rock cutting technology

This paper describes a novel method of rock cutting — oscillating disc cutting (ODC) — in which the forces acting on the cutting tools, and hence on the excavation machine supporting these tools, are extremely low. Four different techniques are incorporated in the cutting method to achieve this result. The importance of this novel method is that it allows very strong and/or abrasive rock to be machined easily and rapidly without suffering the high rates of tool wear and/or tool failure that are experienced by conventional cutting machines operating in these types of rock. Also the fact that the ODC method requires very low machine reaction forces means that lightweight, and therefore manoeuvrable, mining and tunnelling machines can be employed in the excavation process. In the initial sections of this paper we discuss the physics of the process of rock breakage caused by mechanical cutting tools and the wear and failure mechanisms of these tools. The arguments are given in order to introduce the thinking behind the ODC method.     

Towards the prediction of rock excavation machine performance

 Recent rock cutting laboratory experiments and field studies on the performance of rock cutting trenchers has provided a better understanding of the processes and factors affecting tool consumption and excavation rates of rock excavation machines. On the basis of this, a model has been developed to assist in the prediction of trenching rates and tool wear in various geological situations. The paper provides an overview of the set-up and results of both laboratory and field studies. It describes a basic framework model of the processes and mechanisms involved in assessing excavation rates and tool consumption and discusses how the acquired knowledge can be used to assist with predictions for future excavation works. It then considers how this knowledge could be applied by practitioners who have to work with a scarcity or absence of good quality and reliable data. Received: 29 July 1997 · Accepted: 3 January 1998     

金刚石圆锯片切割石材及有限元分析

通过XK5032C型数控铣床进行切削花岗石试验研究,主要考察了加工参数对圆锯片切削力的影响,确定了金刚石圆锯片切削花岗石时加工参数对切削力的影响规律。切削力的大小随着切削深度和进给速度的增加而增大,而随着主轴转速的增大而减小。通过ANSYS软件进行了有限元分析,研究在不同的加工参数下,金刚石圆锯片实际受力情况,分析其中的变化规律。     

Schifflerised angle sections for triangular-based communication towers

This paper is concerned with the use of Schifflerised angle sections for triangular-based lattice communication towers. The torsional-flexural buckling properties of conventional 90°, 60° and schifflerised angles are compared. The experimental results obtained from the compression tests conducted on three different sizes of schifflerised angle sections are compared with the analytical results predicted from finite element analysis and with the capacities predicted from the procedure given in the literature. The capacity of schifflerised angles are underestimated by the methods suggested in the literature. The FE model non-linear analysis predicts the failure loads closer to the test results with a variation of ?3 to 10%. The strength of schifflerised angles is 5 to 20% higher compared to conventional 90° angles. The behaviour of 60 m high three-legged triangular communication tower with schifflerised angles for leg members and conventional equal angles for all other members tested at Tower Testing and Research Station, CSIR-Structural Engineering Research Centre, Chennai is presented. NE-NASTRAN, a finite element software, is used to model the tower using beam column and plate shell elements for predicting the behaviour. The analytical and test results are compared with the codal provisions.     

Correlation of rock cutting tests with field performance of a TBM in a highly fractured rock formation: A case study in Kozyatagi-Kadikoy metro tunnel,Turkey

This paper presents and discusses detailed field and laboratory studies concerning boreability prediction of tunnel boring machines (TBMs) used in Kozyatagi-Kadikoy metro tunnels in Istanbul in a highly fractured rock formation. The determination of some design parameters and performance prediction of a tunnel boring machine (TBM) are carried out using full-scale rock cutting test. The intact rock samples having minimum sizes of 1.0 × 0.7 × 0.7 m are obtained from shale and limestone (Kartal Formation) along the tunnel line. The rock samples are subjected to full-scale laboratory rock cutting tests with different depth of cut and cutter spacing values using a constant cross section (CCS) disc cutter of 330 mm in diameter. Cutter forces, i.e., thrust force, rolling force and specific energy values are recorded for each cut. The results of the tests are first used to calculate TBM design and performance parameters such as torque and thrust requirements and cutting rates. In the second part of the research, the field performance of the TBM is recorded with the aid of data acquisition system installed within TBM and the predicted performance and design values obtained from full-scale rock cutting tests are compared with the field values. It is observed that fractured characteristics of the rock formation affect tremendously TBM performance and predicted values differ from the field data in some extend. It is believed that the results will serve as a guide for efficient selection and use of TBMs.     

Design and fabrication of the passive solar still using blue metal stone

In this paper, an attempt has been made to find out the effect of blue metal stone on heat transfer coefficient for a passive single-slope distillation system in summer climatic conditions. The experiments have been conducted on a south facing, single slope, solar still of 10° inclination of condensing cover, in summer climatic conditions for 24?h on 5 different days for three different sizes of blue metal stone from 6 to 20?mm and this is finally compared by using the basin without any absorbing material. The thermal efficiency is calculated by using the energy balance equation.     

A Two‐Dimensional Plum‐Blossom Sensor Array‐Based Multiple Signal Classification Method for Impact Localization in Composite Structures

The growing use of composite materials on aircraft structures has attracted much attention for the impact monitoring as a kind of structural health monitoring method. Uniform linear sensor array (ULSA)‐based multiple signal classification (MUSIC) technology is a promising method because of its directional scanning ability and easy arrangement of the sensor array. However, the monitoring range of ULSA‐based MUSIC method is 0°–180°, and its beamforming properties degrade at angles close to 0° and 180°. Besides, the ULSA‐based MUSIC methods proposed require the knowledge of the direction dependent velocity profile obtained by additional experiments. This article presents a novel two‐dimensional (2‐D) plum‐blossom sensor array (PBSA)‐based MUSIC method. First, the velocity propagating at the specific direction is estimated by impact signal itself using PBSA directly. Second, 2‐D PBSA‐based MUSIC method well realizes omnidirectional 0°–360° impact localization of composite structures. Experimental results show its successful performance on epoxy laminate plate and complex composite structure.     

GPGPU-parallelised hybrid finite-discrete element modelling of rock chipping and fragmentation process in mechanical cutting

Mechanical cutting provides one of the most flexible and environmentally friendly excavation methods.It has attracted numerous efforts to model the rock chipping and fragmentation process,especially using the explicit finite element method(FEM) and bonded particle model(BPM),in order to improve cutting efficiency.This study investigates the application of a general-purpose graphic-processing-unit parallelised hybrid finite-discrete element method(FDEM) which enjoys the advantages of both explicit FEM and BPM,in modelling the rock chipping and fragmentation process in the rock scratch test of mechanical rock cutting.The input parameters of FDEM are determined through a calibration procedure of modelling conventional Brazilian tensile and uniaxial compressive tests of limestone,A series of scratch tests with various cutting velocities,cutter rake angles and cutting depths is then modelled using FDEM with calibrated input parameters.A few cycles of cutter/rock interactions,including their engagement and detachment process,are modelled for each case,which is conducted for the first time to the best knowledge of the authors,thanks to the general purpose graphic processing units(GPGPU) parallelisation.The failure mechanism,cutting force,chipping morphology and effect of various factors on them are discussed on the basis of the modelled results.Finally,it is concluded that GPGPU-parallelised FDEM provides a powerful tool to further study rock cutting and improve cutting efficiencies since it can explicitly capture different fracture mechanisms contributing to the rock chipping as well as chip formation and the separation process in mechanical cutting.Moreover,it is concluded that chipping is mostly owed to the mix-mode Ⅰ-Ⅱ fracture in all cases although mode Ⅱ cracks and mode Ⅰ cracks are the dominant failures in rock cutting with shallow and deep cutting depths,respectively.The chip morphology is found to be a function of cutter velocdty,cutting depth and cutter rake angle.     

Predictive plots for conical pick performance using mechanical and elastoplastic properties of rocks

Conical picks are by far the most widely used drag type cutting tools employed on partial face rock excavation machines. The cutting force and specific energy are two important design parameters for the conical pick performance, and the rock cutting testing is considered as the promising tool for determining these parameters. In the absence of an instrumented cutting rig, researchers generally rely on empirical predictive plots. For this, this paper suggests predictive plots for estimating the cutting force and specific energy, in consideration of the cutting depth to define the cuttability with conical picks. In this context, rock cutting tests were carried out on six volcanic rock samples with varying cutting depths using the unrelieved and relieved cutting modes. The cutting force and specific energy were correlated with the uniaxial compressive strength, Brazilian tensile strength, elasticity modulus, and plasticity index. Predictive plots were proposed for different cutting depths in the unrelieved and relieved cutting modes and exponential relationships were obtained among the cuttability parameters, and mechanical and elastoplastic properties of rocks.     

A study on ceiling jet characteristics in an inclined tunnel

The characteristics of a ceiling jet of an inclined tunnel in a fire will be studied and reported in this paper. Scale modeling experiments on a ceiling jet in a model tunnel of length 3.0 m, width 0.8 m and height 1.0 m inclined at different angles of 0°, 10°, 20° and 30° were carried out. Numerical studies by large eddy simulation were then performed. Both experimental observation and numerical simulation indicated that the characteristics of the temperature and velocity fields near the upper tunnel are different from those obtained using the empirical equations reported in the literature. Another set of empirical equations for gas temperature and flow velocity along the tunnel were fitted by experimental data. These derived empirical equations are useful for estimating the temperature and flow velocity patterns for the ceiling jet in an inclined tunnel with an angle within the range 0–30°.     

1500—2000m^3／h斗轮挖掘机切割阻力的研究

文章介绍了采用缩小比例的模拟斗齿对小龙潭露天矿的原型煤、泥龙岩等进行垂直层理的直线型切割，通过对参与切割的试样物理、力学参数、切割参数的因次分析，建立无量纲方程，进行相似理论的模型试验和对诸参数组织正交试验，来预测原型斗轮的切割阻力，为设计开发斗轮挖掘机提供理论依据。最后，由整机性能测试来加以验证。     

Analysing the life index of diamond cutting tools for marble building stones based on laboratory and field investigations

Bulletin of Engineering Geology and the Environment - Cutting tool wear constitutes one of the principal parameters in the processing cost of building stone. The life index of the cutting tool is...     

Fatigue and damage properties of non-consecutive jointed mudstone samples subjected to cyclic triaxial loading

Bulletin of Engineering Geology and the Environment - Non-consecutive jointed mudstone samples with dip angles (0° is the horizontal axis) of 15°, 30°, and 45° were subjected to...     

3D mechanical modeling of soil orthogonal cutting under a single reamer cutter based on Drucker–Prager criterion

Reamers have been the major implement used to enlarge the hole size in reaming stage of horizontal directional drilling (HDD). The choice of its available structural design becomes critical to maximize the rate of penetration and minimize the tripping time, thereby decreasing the cost of operations and the risk of experiencing stability problems. Moreover, because the duration period of a HDD project is largely dependent on the reaming stage, it is crucial to study the reaming efficiency by use of the appropriate operating conditions (cutting angle and depth). In the paper, the reaming efficiency of reamer is analyzed based on the development of a 3D analytical cutting force model of soil orthogonal cutting under a single reamer cutter. Focusing on the soil orthogonal cutting mechanism under a single reamer cutter, the interaction and friction between soil and cutter and the shear action of 3D shear zone are comprehensively considered, consequently the mechanical properties are given. Based on these analyses and using the Drucker–Prager criterion given a weight to the intermediate principal stress, the analytical models are proposed. In addition, this paper presents 3D FEM simulations for the analysis of soil orthogonal cutting under a single reamer cutter. The subject has been covered in two parts. Part one deals with the verification of the analytical cutting force model, the other focuses on the assessment and selection of the criterions of shear angle. The analytical cutting force model presented provides the capability to evaluate cutter loading for utilization of a single cutter with different rake angles to cut soils, and to plot the effect of change in the rake angle. Finally, the optimum rake angle of single reamer cutter was obtained. The results of this analysis can be integrated to study reamer performance. It can also provide a guideline to the application and design of the reamer assembly for various soils.     

Transient three-dimensional window thermal effects

A model is developed, and checked experimentally, to allow reasonably accurate computer calculations for three-dimensional temperature distributions in sunlit, partly shaded windows. The time evolution of surface temperature profiles, the sideways heat flow to and from adjacent walls, and the heating due to solar absorption in the glazing can be calculated. To reduce computation time, only two layers of cells were taken for each glazing pane, and uniform heat transfer was assumed between the panes. Nevertheless, the calculations matched well with experimental temperatures obtained for nine different full-scale windows at different orientations in a rotatable test hut on 27 clear or nearly clear winter days. In some winter experiments, an average of 15% of the 24-hour heat loss through a south window went sideways to the adjacent walls, with a minimum of 10% near noon, and a maximum of 20% near midnight. Near noon, with an ambient temperature of — 7°C (20°F), the centre of the inside of a south-facing triple-glazed window was above room temperature, due to solar absorption in the glass. At the same time, the inside of the shaded edge of the glazing was below room temperature.