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1.
Mono-wire block cutting machines that cut with a diamond wire can be used for squaring natural stone blocks and the slab-cutting process. The efficient use of these machines reduces operating costs by ensuring less diamond wire wear and longer wire life at high speeds. The high investment costs of these machines will lead to their efficient use and reduce production costs by increasing plant efficiency. Therefore, there is a need to investigate the cutting performance parameters of mono-wire cutting machines in terms of rock properties and operating parameters. This study aims to investigate the effects of the wire rotational speed (peripheral speed) and wire descending speed (cutting speed), which are the operating parameters of a mono-wire cutting machine, on unit wear and unit energy, which are the performance parameters in mono-wire cutting. By using the obtained results, cuttability charts for each natural stone were created on the basis of unit wear and unit energy values, cutting optimizations were performed, and the relationships between some physical and mechanical properties of rocks and the optimum cutting parameters obtained as a result of the optimization were investigated.  相似文献   

2.
Shore hardness has been used to estimate several physical and mechanical properties of rocks over the last few decades. However, the number of researches correlating Shore hardness with rock cutting performance is quite limited. Also, rather limited researches have been carried out on predicting the performance of chain saw machines. This study differs from the previous investigations in the way that Shore hardness values (SH1, SH2, and deformation coefficient) are used to determine the field performance of chain saw machines. The measured Shore hardness values are correlated with the physical and mechanical properties of natural stone samples, cutting parameters (normal force, cutting force, and specific energy) obtained from linear cutting tests in unrelieved cutting mode, and areal net cutting rate of chain saw machines. Two empirical models developed previously are improved for the prediction of the areal net cutting rate of chain saw machines. The first model is based on a revised chain saw penetration index, which uses SH1, machine weight, and useful arm cutting depth as predictors. The second model is based on the power consumed for only cutting the stone, arm thickness, and specific energy as a function of the deformation coefficient. While cutting force has a strong relationship with Shore hardness values, the normal force has a weak or moderate correlation. Uniaxial compressive strength, Cerchar abrasivity index, and density can also be predicted by Shore hardness values.  相似文献   

3.
Cutting performance of diamond wire saw is a key factor influencing mine planning, production scheduling, and equipment selection for dimension stone quarries. It is normally measured in terms of cutting rate. Rock samples collected from various granite and marble quarries in India were tested in laboratory to determine their physico-mechanical properties. Cutting rate of diamond wire saw was measured in the field studies during the actual cutting process in quarries. Using these laboratory determined properties and the cutting rate, a multiple linear regression model has been developed to predict the cutting rate of diamond wire saw. Physico-mechanical properties of rocks determined in laboratory are used as independent variables and cutting rate as predictor variable in the regression model. The study indicates that the cutting rate increases with a decrease in most of the hardness and strength parameters of rock. The final model is tested for its goodness of fit indicating a significant linear relation between cutting rate and physico-mechanical properties, namely tensile strength, slake durability index, and Cerchar hardness index with regression coefficient of 94%. The resulting model can be used suitably for different types of hard to medium hard and soft dimension stones. The generalized model for estimating the cutting rate becomes a handy tool for mining engineers to work out operating efficiency, expenses, planning etc. of the dimension stone block cutting.  相似文献   

4.
The aim of this paper is to obtain, from a numerical study using the discrete element method, quantitative information on the behaviour of a rockfill dam, particularly the effect of rock ageing on the movements of the dam. A numerical model is defined at three different scales: the block scale, the elementary representative volume scale and the dam scale. The model uses the discrete element code PCF2D, considering breakable clusters of 2D balls. Three rock-ageing laws, taking into account the time-evolving resistance for blocks, are proposed. The different parameters are determined from experimental data of laboratory tests performed on rock blocks. The relevance of the model seems acceptable, considering that the displacements obtained in the simulations are in the same order of magnitude as the displacements measured on the actual dam.  相似文献   

5.
In a processing plant, natural stone can be cut by methods such as circular sawing (CS), frame sawing (FS), water jet cutting (WJC) and abrasive water jet cutting (AWJC). The efficiency of cutting systems can be compared using various parameters. In this study, the specific energy values were determined and compared to evaluate the efficiency of rock-cutting methods. Rock-cutting experiments were performed on 12 different types of rock samples using a circular sawing machine and an AWJC machine. The experimental results showed that the specific energy values in AWJC were generally higher than in CS. In addition, the relationships between specific energy values and rock properties were explained in this study. The Shore hardness and abrasion resistance were found to be strongly related to the specific energy values, and according to these parameters prediction charts of specific energy values were created.  相似文献   

6.
土石混合体是由软弱的土颗粒与刚度较大、强度较高的块石混合而成,因此土石混合体边坡失稳时,其滑动面受块石-土形成的细观结构特征影响,导致边坡稳定性分析存在诸多困难。本文基于一典型的土石混合体边坡,建立颗粒离散元数值模型,通过室内试验标定土体细观参数,结合强度折减法分析土石混合体边坡与纯土体边坡破坏模式及滑面形态的差别。结果表明:块石的存在使得土石混合体边坡的接触力链分布极不均匀,块石的存在使接触力链形成闭环,增大了滑动面积,对边坡有加固作用;土石混合体边坡的滑面发展趋势总倾向于穿过块石间的缝隙,滑面的发展与块石分布状况相关联;当块石含量达到20%以上时,边坡稳定性显著提高;块石含量达到30%~50%时,滑坡以局部块体运动为主,无法形成连续的滑动面。研究成果可为土石混合体边坡的变形破坏机理分析提供依据与参考。  相似文献   

7.
深基坑稳定性问题是重要的工程问题,其中,有效支护结构是保证基坑工程顺利实施的基础。本文引入离散元法,提出了基坑及支护结构建模和数值模拟方法。采用紧密堆积离散单元构建模型初始地层,引入了离散单元团簇模型来构建表面较为光滑的管桩。以南京某深基坑工程为例,采用三维离散元模拟软件MatDEM3D构建几何模型,并根据土体的力学性质设定相应单元的力学参数。数值模拟中,通过预平衡操作实现土层的压实,进而模拟了基坑开挖过程中土体和管桩的变形。将数值模拟结果与实测监测数据进行了对比分析,评价了基坑支护结构的有效性。这种基坑离散元数值模拟方法在基坑开挖过程的稳定性预判和支护结构的有效性评价上具有潜在的应用前景。  相似文献   

8.
Numerical modeling of stress-permeability coupling in rough fractures   总被引：2，自引：0，他引：2  
A numerical model is described for coupled flow and mechanical deformation in fractured rock. The mechanical response of rock joints to changes in hydraulic pressure is strongly influenced by the geometric characteristics of the joint surfaces. The concept of this work is to combine straightforward finite element solutions with complex and realistic fracture surface geometry in order to reproduce the non-linear stress-deformation-permeability coupling that is commonly observed in fractures. Building on the numerous studies that have expanded the understanding of the key parameters needed to describe natural rough-walled fractures, new methods have been developed to generate a finite element mesh representing discrete fractures with realistic rough surface geometries embedded in a rock matrix. The finite element code GeoSys/Rockflow was then used to simulate the coupled effects of hydraulic stress, mechanical stress, and surface geometry on the evolving permeability of a single discrete fracture. The modeling concept was experimentally verified against examples from the literature. Modeling results were also compared to a simple interpenetration model.  相似文献   

9.
朱爱军  曾祥勇  邓安福 《岩土力学》2009,30(8):2495-2500
数值流形方法是包含流形元、有限元及DDA在内的数值方法体系,建立流形元与DDA块体的接触方程,则可实现流形方法框架下的连续介质和散体系统共同作用模拟。针对填石路堤工程,编制了大型数值计算程序,采用块体随机生成、块体粒径控制及块体自然堆积的方法建立散体系统的DDA模型,对路堤的分层铺设、碾压及工后沉降变形等进行模拟分析。通过算例表明,在数值流形方法框架下,采用流形元与DDA共同作用的方法,可以很好地对同时存在连续变形和散体大变形的体系进行计算分析,其对该类问题的模拟更接近分析对象的实际情况,有助于从根本上揭示分析对象变形的细观机制和规律,并能考察更多因素对工程问题的影响。  相似文献   

10.
This paper addresses one of the most challenging problems in mining rock engineering—the interaction between block cave mining and a large overlying open pit. The finite element modeling/discrete element modeling (FEM/DEM) approach was utilized in the analysis of block caving-induced step-path failure development in a large open pit slope. The analysis indicated that there is a threshold percentage of critical intact rock bridges along a step-path failure plane that may ensure the stability of an open pit throughout caving operations. Transition from open pit to underground mining at Palabora mine presents an important example of a pit wall instability triggered by caving. Using combined FEM/DEM-DFN (discrete fracture network) modeling, it was possible to investigate the formation of a basal failure surface within an open pit slope as a direct result of cave mining. The modeling of Palabora highlighted the importance of rock mass tensile strength and its influence on caving-induced slope response.  相似文献   

11.
The objective of this research was to use numerical models based on mechanical approaches to improve the integration of the protective role of forests against rockfall into block propagation models. A model based on the discrete element method (DEM) was developed to take into account the complex mechanical processes involved during the impact of a block on a tree. This modelling approach requires the definition of many input parameters and cannot be directly integrated into block propagation models. A global sensitivity analysis identified the leading parameters of the block kinematics after impact (i.e. block energy reduction, trajectory changes, and rotational velocity): the impact velocity, the tree diameter, and the impact point horizontal location (i.e. eccentricity). Comparisons with the previous experimental and numerical studies of block impacts on trees demonstrated the applicability of the DEM model and showed some of the limitations of earlier approaches. Our sensitivity analysis highlights the significant influence of the impact velocity on the reduction of the block’s kinetic energy. Previous approaches usually also focus on parameters such as impact height, impact vertical incidence, and tree species, whose importance is only minor according to the present results. This suggests that the integration of forest effects into block propagation models could be both improved and simplified. The DEM model can also be used as an alternative to classical approaches for the integration of forest effects by directly coupling it with block propagation models. This direct coupling only requires the additional definition of the location and the diameter of each tree. Indeed, the input parameters related to the mechanical properties of the stem and the block/stem interaction in the DEM model can be set to average values because they are not leading parameters. The other input parameters are already defined or calculated in the block propagation model.  相似文献   

12.
Discrete numerical modelling of rockfill dams   总被引：1，自引：0，他引：1  
The aim of this study is to obtain quantitative information on the behaviour of rockfill used in embankment dams, and particularly on the influence of block breakage on the displacement field, from a numerical analysis using the Distinct element method. A methodology is set up to define the resistance of the 2D particles so that the same probability of breaking blocks may be reproduced as in a 3D material. The model uses the discrete element code PFC2D (Itasca Consulting Group Inc., PFC2D (Particle Flow Code in Two Dimensions), Version 3.0, 2002) and considers breakable clusters of 2D balls. The different parameters are determined from experimental data obtained from laboratory tests performed on rock blocks. The model is validated by comparing the results of the simulation of shearing tests with actual triaxial tests on rockfill material published in the literature. The numerical analysis of block crushing in an actual dam is proposed in the last part of this paper. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

13.
A State-of-the-Art Review of Stone/Sand-Column Reinforced Clay Systems   总被引：1，自引：0，他引：1  
This paper presents a state-of-the-art review of published research papers and reports that focus on the modeling, testing, and analysis of soft clays that are reinforced with sand/stone columns in relation to bearing capacity and settlement considerations. The review is presented in chronological order to shed light on the development of this field of research in the last 40+ years. The objective of the study is to assemble published results from field, laboratory, and numerical investigations of sand/stone columns in clay in one resource to provide future researchers and designers with easy access to information and data. The majority of the reviewed papers include an experimental component that is based on field or laboratory scale tests (1-g, triaxial, or centrifuge) conducted on clay specimens reinforced with partially or fully penetrating, encased or ordinary, stone or sand columns that were installed as single columns or as column groups. Some papers included numerical experiments that were based on finite element models, while others presented analytical solutions for modeling the response of the composite system. A compilation of the important findings from physical, numerical, and analytical models in addition to a summary table that facilitates access to information from various research efforts are presented in the paper.  相似文献   

14.
基于DDEM的自然崩落采矿法崩落规律的数值模拟   总被引：1，自引：1，他引：0  
姜增国  杨保仓 《岩土力学》2005,26(2):239-242
利用DDEM（可变形离散单元法）原理和方法,研究了自然崩落法矿体崩落规律。针对具体地质条件和赋存情况及矿岩物理力学性质,采用计算机数值模拟分析了自然崩落法的崩落规律,得出了DDEM在用于模拟矿块自然崩落法中崩落规律和分析其崩落机理时是较适合的结论,不仅可以从力学角度对崩落的力学机理进行研究,而且能直观地用图形给出矿体在崩落过程中的具体形态变化,有效地指导放矿,现场试验验证效果良好。  相似文献   

15.
Due to the diverse and complex structure of soil and the variety of foam-modifier materials that are used, it is difficult to provide a model to predict the laboratory behavior of modified soils. For example, several studies have shown independently that the amount of the foam-modified soil depends on several factors, such as the internal friction angle and normal stiffness. Of late, modeling by numerical methods has become popular in engineering sciences and the modeling of complex material behavior is possible with the help of numerical methods. In this research, the performance and efficiency of the numerical method in the modeling of laboratory tests such as the slump test and the uniaxial compressive strength test were investigated and it was found that numerical modeling performs very well in predicting the results of these tests for foam-modified sand samples. In order to achieve this goal, the slump test and the uniaxial compressive strength test were performed in the laboratory on several modified sand samples in order to obtain the laboratory results for these samples. Then, numerical simulation of these experiments was carried out using PFC3D software. The results of numerical modeling were compared with the experimental results, and good agreement was observed. Finally, after calibration of the numerical model using the experimental results, the effect of changes in the internal friction angle and the normal stiffness of the modified sand in the amount of the slump was investigated. According to the results of this sensitivity analysis, it was determined that by increasing both effective parameters the amount of the slump of foam-modified sand decreases and that the parameters are the most important factors in controlling the slump value.  相似文献   

16.
数值模拟是一种利用电子计算机,通过数值计算和图像显示的方法,研究工程问题、物理问题乃至自然界各类问题的方法。随着高性能计算的不断发展,数值模拟方法在沉积盆地构造变形研究中的应用不断扩大,学术界和工业界将数值模拟方法广泛应用于盆地构造变形特征与变形机制的定量研究,取得了丰硕的成果。本文在系统分析前人数值模拟成果的基础上,阐述了有限元、有限差分、边界元和离散元四种常用数值模拟实验方法的特征和应用。同时,本文对近年来数值模拟方法在沉积盆地褶皱冲断构造变形中的研究进展进行了分类总结,重点介绍这一方法在构造特征与变形机制研究中取得的成果,为数值模拟方法在盆地构造变形领域应用的不断扩大和深入提供参考。最后,本文对数值模拟技术在目前应用中面临的问题和未来的发展方向提出了一些看法和建议。  相似文献   

17.
Due to the low permeability of many shale reservoirs, multi-stage hydraulic fracturing in horizontal wells is used to increase the productive, stimulated reservoir volume. However, each created hydraulic fracture alters the stress field around it, and subsequent fractures are affected by the stress field from previous fractures. The results of a numerical evaluation of the effect of stress field changes (stress shadowing), as a function of natural fracture and geomechanical properties, are presented, including a detailed evaluation of natural fracture shear failure (and, by analogy, the generated microseismicity) due to a created hydraulic fracture. The numerical simulations were performed using continuum and discrete element modeling approaches in both mechanical-only and fully coupled, hydro-mechanical modes. The results show the critical impacts that the stress field changes from a created hydraulic fracture have on the shear of the natural fracture system, which in-turn, significantly affects the success of the hydraulic fracture stimulation. Furthermore, the results provide important insight into: the role of completion design (stage spacing) and operational parameters (rate, viscosity, etc.) on the possibility of enhancing the stimulation of the natural fracture network (‘complexity’); the mechanisms that generate the microseismicity that occurs during a hydraulic fracture stimulation; and the interpretation of the generated microseismicity in relation to the volume of stimulated reservoir formation.  相似文献   

18.
The cutting operations of dimension stone at quarries produce a large amount of fines that, in turn, cause a negative environmental impact over local surface waters. This article presents a detailed analysis of the mobilized contamination associated with runoff waters in a large granite quarry (～200 ha) which is located in Porriño (Galicia, NW Spain), the most important production centre of dimension stone in Spain. There, an intensive monitoring survey was developed in order to characterize the hydrology of the system as well as the release and transport of pollutants. This was accomplished by means of different control sections for the flow and by the collection of 52 random water samples. Automatic samplers were also used to collect 192 water samples associated with runoff generated by significant rain events. For each of the samples collected, a wide battery of analytic determinations was performed, including solid loads, turbidity, organic pollution, nutrient and selected metals. Upon careful examination it has been possible to obtain different parameters related to the contamination control, like the “event mean concentration” (EMC), maximum concentrations and specific sediment loads. Moreover, a comprehensive statistical study including parameter correlation and cumulative probability analyses helped to understand the pollutant mobilization behaviour within the quarry system. It can be concluded that mobilized contamination shows the anomalous presence of some metals, whose concentrations are in excess when compared to the natural rock. This excess metal amount must be attributed to an anthropogenic source associated to mining and cutting operations.  相似文献   

19.
张坤  李东庆  陶坤  陈继  童刚强 《冰川冻土》2014,36(4):976-986
气候变暖背景下,块石路基及通风管-封闭块石基底复合路基成为多年冻土区高等级公路冷却路基的主要结构形式. 为探明不同直径块石层的渗流特征和规律,开展了立方排列球体室内风洞试验,一方面获得了渗透率和惯性阻力系数及其与球体直径间的统计关系;另一方面得到了球体层内部压力梯度与渗流速度呈二次非线性关系. 基于该试验得到的参数和关系,采用多孔介质中流固耦合传热模型,通过有限体积法模拟了柴木铁路块石路基的降温效果,并利用实测数据验证了模型及参数的可靠性. 在此基础之上,以青藏高等级公路特殊路基为原型,使用该传热模型开展了封闭块石基底路基和通风管-块石复合路基长期冷却降温效果的数值模拟研究. 结果表明：封闭块石基底路基和通风管-封闭块石复合路基在研究期内均有降温效果,可以提高路基下人为上限,而块石夹层路基在一定时期内可以提高冻土上限,但下部土体温度升高,长期降温效果较差.  相似文献   

20.
Summary A number of field and laboratory tests have been carried out on more than 15 coal seams of compressive strengths ranging from 19 MPa to 44 MPa to evolve methods which would help in the selection of suitable coaling machines for hard coal seams. The effect of physico-mechanical properties on cuttability were studied in the laboratory for all these coal seams to identify the relevant parameters affecting the specific energy of coal cuttability. These data were subjected to regression analysis to find the best fit for estimation of laboratory specific energy of coal samples on the basis of simple laboratory and field tests for the strength parameters. Field studies were also conducted over a large number of active mechanized coal faces to study in situ cuttability along with the geo-mining conditions of the site. The field and the laboratory data so generated were correlated and an attempt is made to establish a relationship for estimating the field specific energy for a particular capacity of coaling machines by considering the geo-mining domain of the field in totality.  相似文献   

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