共查询到20条相似文献，搜索用时 715 毫秒
1.
In this paper, an experimental study on the cut depth, which is an important cutting performance indicator in the abrasive waterjet (AWJ) cutting of rock, was presented. Taguchi experimental design of an orthogonal array was employed to conduct the experiments. A variety of nine types of granitic rocks were used in the cutting experiments. The experimental data were used to assess the influence of AWJ operating variables on the cut depth. Using regression analysis, models for prediction of the cut depth from the operating variables and rock properties in AWJ machining of granitic rocks were then developed and verified. The results indicated that the cut depths decreased with increasing traverse speed and decreasing abrasive size. On the other hand, increase of the abrasive mass flow rate and water pressure led to increases in the cut depths. Additionally, it was observed that the standoff distance had no discernible effects on the cut depths. Furthermore, from the statistical analysis, it was found that the predictive models developed for the rock types had potential for practical applications. Verification of the models for using them as a practical guideline revealed a high applicability of the models within the experimental range used. 相似文献
2.
This paper presents an experimental and statistical study on the kerf width, used instead of the width of the cut in abrasive waterjet (AWJ) cutting. Pre-dimensioned granitic rocks were sampled for the experimentations designed by using Taguchi orthogonal arrays. The effects of the AWJ operating variables on the kerf width were studied and the rock properties were correlated with the kerf widths. Additionally, predictive models for the kerf widths were developed using multi-variable regression analysis and the developed models were verified through some statistical tests. The results demonstrated that the standoff distance and the traverse speed have significant effects on the kerf widths. The results also showed that water absorption, unit weight, microhardness, the maximum grain size of rock-forming minerals, and mean grain size of the rock have significant correlations with the kerf widths of the tested rocks. Furthermore, the modeling results revealed that the predictive models derived from rock properties, can be successfully used as a practical guideline. 相似文献
3.
Chiara Origliasso Marilena Cardu Vladislav Kecojevic 《Rock Mechanics and Rock Engineering》2014,47(2):757-770
The purpose of this research was to evaluate the production rate (PR) and cutting performance of surface miners (SM) based on rock properties and specific energy (SE). We use data from equipment manufacturers and experimental data in this study and propose a new method and equations to determine both the PR and the cutting speed of SM. The unconfined compressive strength (UCS) of the rock, its abrasivity, and the machine’s engine power are the three most important factors influencing the PR. Moreover, the cutting depth, UCS, and engine power have a significant impact on the cutting speed. We propose a new method and equations to determine the energy required to cut a volume unit and a surface unit, i.e., specific energy, and establish the relationship between SE, UCS, and PR. The results of this study can be used by surface miner operators to evaluate the applicability of the machines to a specific mine site. 相似文献
4.
高压水射流的破岩效果对高压水射流辅助掘进机破岩技术至关重要。为提升隧道掘进机工况下高压水射流辅助破岩的效率,开展大线速度下超高压水射流破岩试验,分析喷嘴移动线速度、射流压力和喷嘴直径对破岩效果的影响规律,并探究加磨料和射流形式对破岩效果的影响。试验结果表明,随喷嘴移动线速度增加,高压水射流的切割深度和切割宽度均近似线性减小;随射流压力增加,切割深度近似线性增大,压力从200 MPa提高到280 MPa,切割深度增加了72%～82%;喷嘴直径从0.35 mm增大到0.60 mm,切割深度增加了60%～85%。大线速度下加磨料后射流变发散,加磨料的切割深度小于纯水的切割深度,加磨料的切割宽度大于纯水的切割宽度。砂管束流射流模式的能量利用率更高,砂管束流的切割深度比长线射流的切割深度大35%～42%,砂管束流的切割宽度比长线射流的切割宽度大78%～85%。基于Crow切割岩石理论,通过试验数据回归分析,得到大线速度下超高压水射流切割深度半理论半经验预测模型,可为高压水射流辅助掘进机破岩技术中射流切割参数优化提供参考依据。研究成果对提升隧道掘进机工况下超高压水射流辅助破岩的效率是很有意义的。 相似文献
5.
空化水射流破碎岩石的机理研究 总被引：9，自引：1，他引：8
在不同泵压和淹没压力条件下,针对不同类型的空化喷嘴,对空化水射流的空泡云特性和破碎岩石机理进行了一系列实验研究,探讨了空化水射流的空泡云与冲蚀能力之间的相互关系。优化空化喷嘴结构和工作条件以减小泵压,从而降低输入能量。空泡云的可视化研究显示缩放形喷嘴产生的空化云的长度和宽度比收敛形喷嘴的大。研究表明,空化水射流切割破碎岩石主要是由空泡的溃灭引起的,空泡云的长度等于靶距与切割深度之和;在切割破碎岩石时冲蚀效果只在开始几秒内发生,冲蚀深度并不随时间而增大。 相似文献
6.
借助连续-非连续单元法(CDEM),对牙轮钻单齿压入破岩的机制进行了探讨,研究了加载过程中破碎体积及破碎坑的演化规律,分析了岩体凝聚力和内摩擦角对单齿破岩体积及破碎坑形态的影响。数值计算结果表明,破碎坑基本上呈半椭球体,其宽深比仅受内摩擦角控制,随着内摩擦角的增加,破碎坑的宽深比减小。破碎坑的宽度、深度及单齿破岩体积可用齿压F、钻齿半径r、凝聚力c及内摩擦角? 表征,基于数值计算结果给出了破碎坑的宽度、深度及单齿破岩体积定量表述的公式;基于相关理论公式,考虑各个同时与岩石接触的几个齿轮对岩石的损伤是相互影响的,引入单齿破岩体积的修正系数,建立了牙轮钻的工作参数（轴压、转速、进尺速度等）与岩体凝聚力及内摩擦角的函数关系。在鞍千矿南采区进行了牙轮钻随钻测试的现场试验,获得了不同岩性下的单齿破岩体积,并就近取样测试了岩体的凝聚力及内摩擦角。当修正系数取0.363时,现场测试结果与基于数值计算得到的单齿破岩体积基本一致,从而证明了数值计算及相关理论推导的正确性。研究成果可以为岩体强度的动态测试提供依据。 相似文献
7.
This paper presents an experimental study on the sawing of granitic rocks by circular diamond sawblades. The influence of the operating variables and rock properties on the specific energy were initially investigated and analyzed. To determine the most significant operating variables and rock properties influencing the specific energy, statistical analyses were then employed and the models were built for the estimation of specific energy depending on the operating variables and the rock properties. Moreover, the derived models were validated through statistical tests such as the determination coefficient, t-test, F-test, and residuals. The results indicated that the specific energy decreased with the decreasing of peripheral speed and the increasing of traverse speed, cutting depth, and flow rate of cooling fluid, respectively. It was concluded that, rather than the physico-mechanical properties, the mineralogical properties were the dominant rock properties affecting the specific energy. Additionally, the peripheral speed was statistically determined as the most significant operating variable affecting the specific energy. The peripheral speed was followed by the cutting depth, traverse speed, and flow rate of cooling fluid with respect to their level of significance on the specific energy. Furthermore, the model results revealed that the developed models have high potentials as a guidance for practical applications. 相似文献
8.
The competency of any TBM in any geological condition is determined by a rock or rock mass breakage process. A 12.24 km long tunnel between Maroshi and Ruparel College was excavated by Brihanmumbai municipal corporation (BMC) to improve water supply system of greater Mumbai, India, using open-type hard rock tunnel boring machines (TBMs). In this paper an attempt has been made to establish the relationship between rock mass characteristics i.e. RMR and UCS of the Deccan trap rocks and TBMs performance characteristics for 5.83 km long Maroshi–Vakola tunnel section of the Maroshi–Ruparel college tunnel project. To analyze the effect of variable rock mass conditions on the TBM performance, the operating parameters i.e. thrust force, torque and RPM of the machine, were recorded and intact rock strength was determined. The effect of rock mass properties on machine penetration rate (PR) and the relation with other operational parameters were analyzed. The rock strength affects the rock behaviour under compression. When the rolling cutters indent the rock, the stress exerted must be higher than the rock strength i.e.; the rock strength is directly relevant to the performance of TBM. Studies show that the penetration rate decreases with increase in uniaxial compressive strength (UCS). The comparison of measured penetration rate with empirical model developed by Graham, in which, the penetration rate is computed using UCS and average thrust per cutter, showed good agreement with coefficient of determination (R2), i.e. 0.97. The study shows that the TBM performance was maximum in rock mass rating (RMR) range from 40 to 75, while slower penetration was recorded both in very poor and very good rock masses. 相似文献
9.
10.
Mahmoud Behnia Ahmad Rahmani Shahraki Zabihallah Moradian 《Geotechnical and Geological Engineering》2018,36(4):1975-1989
Many surface and underground structures are constructed in heterogeneous rock formations. These formations have a combination of weak and strong rock layers. Due to the alternation of the weak and strong layers, selecting the equivalent and appropriate geomechanical parameters for these formations is challenging. One of these problems is choosing the equivalent strength (i.e., uniaxial compressive strength) of intact rock for a group of rocks. Based on the volume of weak and strong parts and their strength, the equivalent strength of heterogeneous rocks changes. Marinos and Hoek (Bull Eng Geol Environ 60(2):85–92, 2001) presented the “weighted average method” for defining the uniaxial compressive strength (UCS) of heterogeneous rock masses based on the volume of weak and strong parts. Laubscher (1977) used the volume ratio of the strength of a weak part to a strong part (UCS weak/UCS strong) to determine the equivalent strength. In this study, the two methods are compared and their validity is evaluated by experimental data and numerical analyses. The geomechanical parameters of two heterogeneous formations (Aghajari and Lahbari) in the west of Iran were estimated using these methods. The results of the present study obtained through numerical analyses using particle flow code are compared with those of previous studies and discussed. Laboratory and numerical results show UCS decrease and approach to weak strength with an increasing in volume of weak part. When strength ratio of strong to weak rock increase, equivalent strength decrease more severely. The findings show that Laubscher’s method gives more appropriate results than the weighted average method. 相似文献
11.
Wear Performance of Saw Blades in Processing of Granitic Rocks and Development of Models for Wear Estimation 总被引：1，自引：0，他引：1
This study investigates the wear performance of diamond circular saw blades in cutting of granitic rocks. An alternative wear measuring method is developed to measure the reduced blade radius without taking the blade off the machine. The effect on and contribution to the specific wear rate (SWR) of each operating variable are determined, and the SWR is correlated with rock properties. Morphologies of wearing surfaces of segments and rocks are also evaluated using scanning electron microscopy (SEM). Depending on both operating variables and rock properties, prediction models are developed for estimation of the SWR. Results show that the SWR increases with an increase in the peripheral speed and the traverse speed, while it decreases with an increase in the cutting depth and the flow rate of the cooling fluid. The peripheral speed, and the microhardness and proportions of minerals such as quartz, plagioclase, and feldspar are statistically determined as the significant variables affecting the SWR. Finally, it is disclosed that models developed for estimation of SWR have great potential for practical applications. 相似文献
12.
近年来,南海西部海域部分油田的下第三系地层机械钻速较慢,严重影响了勘探开发进度,为了降低钻井成本,增加钻井时效,必须掌握该海域难钻地层的特征及破碎机制。首先开展了岩屑矿物组分测定,结合录井资料,掌握了南海西部海域难钻地层的岩性特征。在对难钻地层的破坏强度、硬度、塑性系数、可钻性、研磨性等相关参数室内试验的基础上,建立了该地层岩石力学参数的预测模型,并基于30口测井的资料建立了难钻地层抗钻特性剖面和南海西部海域三维可钻性剖面,揭示了区域难钻地层的分布情况及抗钻特性;为解决难钻地层的工艺技术难题,还进行了难钻地层PDC钻头的破岩机制试验研究,研究了PDC钻头牙齿齿形、钻压和转速对破岩效率的影响。研究发现：北部湾盆地建议提高钻头的攻击性,并采用高转速的动力钻具复合钻进方式;珠江口盆地应提高钻头复合片的耐磨性,采用较高钻压和合理顶驱转速,为更好地控制钻井成本和提高钻井综合经济效益提供技术指导。 相似文献
13.
Abdolazim Azimian 《Acta Geotechnica》2017,12(2):321-333
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. 相似文献
14.
In-situ Rock Spalling Strength near Excavation Boundaries 总被引：2，自引：0，他引：2
It is widely accepted that the in-situ strength of massive rocks is approximately 0.4 ± 0.1 UCS, where UCS is the uniaxial compressive strength obtained from unconfined tests using diamond drilling core samples with a diameter around 50 mm. In addition, it has been suggested that the in-situ rock spalling strength, i.e., the strength of the wall of an excavation when spalling initiates, can be set to the crack initiation stress determined from laboratory tests or field microseismic monitoring. These findings were supported by back-analysis of case histories where failure had been carefully documented, using either Kirsch’s solution (with approximated circular tunnel geometry and hence σ max = 3σ 1 ?σ 3) or simplified numerical stress modeling (with a smooth tunnel wall boundary) to approximate the maximum tangential stress σ max at the excavation boundary. The ratio of σ max /UCS is related to the observed depth of failure and failure initiation occurs when σ max is roughly equal to 0.4 ± 0.1 UCS. In this article, it is suggested that these approaches ignore one of the most important factors, the irregularity of the excavation boundary, when interpreting the in-situ rock strength. It is demonstrated that the “actual” in-situ spalling strength of massive rocks is not equal to 0.4 ± 0.1 UCS, but can be as high as 0.8 ± 0.05 UCS when surface irregularities are considered. It is demonstrated using the Mine-by tunnel notch breakout example that when the realistic “as-built” excavation boundary condition is honored, the “actual” in-situ rock strength, given by 0.8 UCS, can be applied to simulate progressive brittle rock failure process satisfactorily. The interpreted, reduced in-situ rock strength of 0.4 ± 0.1 UCS without considering geometry irregularity is therefore only an “apparent” rock strength. 相似文献
15.
Accurate laboratory measurement of geo-engineering properties of intact rock including uniaxial compressive strength (UCS) and modulus of elasticity (E) involves high costs and a substantial amount of time. For this reason, it is of great necessity to develop some relationships and models for estimating these parameters in rock engineering. The present study was conducted to forecast UCS and E in the sedimentary rocks using artificial neural networks (ANNs) and multivariable regression analysis (MLR). For this purpose, a total of 196 rock samples from four rock types (i.e., sandstone, conglomerate, limestone, and marl) were cored and subjected to comprehensive laboratory tests. To develop the predictive models, physical properties of studied rocks such as P wave velocity (Vp), dry density (γd), porosity, and water absorption (Ab) were considered as model inputs, while UCS and E were the output parameters. We evaluated the performance of MLR and ANN models by calculating correlation coefficient (R), mean absolute error (MAE), and root-mean-square error (RMSE) indices. The comparison of the obtained results revealed that ANN outperforms MLR when predicting the UCS and E. 相似文献
16.
针对岩石透明条件差,磨料射流冲击岩石的损伤机制不易观察等问题,运用SPH和FEM耦合算法,并引入J-H-C含损伤本构模型描述磨料射流冲击下岩石的损伤场的演化机制。研究结果表明,磨料射流侵彻岩石的深度与磨料射流中磨料的浓度与磨料形状有关;岩石在磨料水射流作用下的沿径向和轴向损伤是呈阶梯式的,距离冲击表面越近,损伤曲线的梯度越大,损伤演化的阶梯形式越不明显;距离冲击表面越远,损伤曲线的梯度越小,损伤演化的阶梯形式越明显。 相似文献
17.
为了验证高能激光技术能够辅助隧道掘进机(tunnel boring machine,简称TBM)盘形滚刀（以下简称滚刀）实现高效破岩,以滚刀破岩过程中基本的运动形式——侵岩为研究对象,参照17 inch（432 mm）工程用滚刀,按1:8的比例制备了缩尺比例滚刀压头（以下引述为滚刀压头）,开展了以孔孔距（2、3、4、5 mm）、刀孔距（3、4、5、6、7 mm）为变量的激光辅助滚刀压头侵岩L20(4×5)正交试验以及无激光作用的对照组试验。试验研究结果表明：随着刀孔距的增加,滚刀压头的破岩量与岩石破碎块度均增加,而垂直力和比能耗均降低,最优刀孔距为6 mm;随着孔孔距的增加,破岩量、垂直力和岩石侵入难度系数均降低,而岩石破碎块度和比能耗均增加,最优孔孔距为3 mm。与传统滚刀回转滚压破岩方式相比,在激光辅助作用下,可促进岩石张拉裂纹的产生,提高了滚刀侵岩效率。所提出的激光辅助滚刀耦合破岩模式在未来TBM极硬岩层隧道掘进中具有一定的应用前景。 相似文献
18.
Characterization of Strength of Intact Brittle Rock Considering Confinement-Dependent Failure Processes 总被引：1，自引：0，他引：1
As technologies for deep underground development such as tunneling underneath mountains or mass mining at great depths (>1,000 m) are implemented, more difficult ground conditions in highly stressed environments are encountered. Moreover, the anticipated stress level at these depths easily exceeds the loading capacity of laboratory testing, so it is difficult to properly characterize what the rock behavior would be under high confinement stress conditions. If rock is expected to fail in a brittle manner, behavior changes associated with the relatively low tensile strength, such as transition from splitting to the shear failure, have to be considered and reflected in the adopted failure criteria. Rock failure in tension takes place at low confinement around excavations due to tensile or extensional failure in heterogeneous rocks. The prospect of tensile-dominant brittle failure diminishes as the confinement increases away from the excavation boundary. Therefore, it must be expected that the transition in the failure mechanism, from tensile to shear, occurs as the confinement level increases and conditions for extensional failure are prevented or strongly diminished. However, conventional failure criteria implicitly consider only the shear failure mechanism (i.e., failure envelopes touching Mohr stress circles), and thus, do not explicitly capture the transition of failure modes from tensile to shear associated with confinement change. This paper examines the methodologies for intact rock strength determination as the basic input data for engineering design of deep excavations. It is demonstrated that published laboratory test data can be reinterpreted and better characterized using an s-shaped failure criterion highlighting the transition of failure modes in brittle failing rock. As a consequence of the bi-modal nature of the failure envelope, intact rock strength data are often misinterpreted. If the intact rock strength is estimated by standard procedures from unconfined compression tests (UCS) alone, the confined strength may be underestimated by as much as 50 % (on average). If triaxial data with a limited confinement range (e.g., σ3 ? 0.5 UCS due to cell pressure limitations) are used, the confined strength may be overestimated. Therefore, the application of standard data fitting procedures, without consideration of confinement-dependent failure mechanisms, may lead to erroneous intact rock strength parameters when applied to brittle rocks, and consequently, by extrapolation, to correspondingly erroneous rock mass strength parameters. It follows that the strength characteristics of massive rock differ significantly in the direct vicinity of excavation from that which is remote with higher confinement. Therefore, it is recommended to adopt a differentiated approach to obtain intact rock strength parameters for engineering problems at lower confinement (near excavation; e.g., excavation stability assessment or support design), and at elevated confinement (typically, when the confinement exceeds about 10 % of the UCS) as might be encountered in wide pillar cores. 相似文献
19.
Irfan Celal Engin Fatih Bayram Nazmi Erhan Yasitli 《Rock Mechanics and Rock Engineering》2013,46(4):755-766
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
20.
Sefer Beran Çelik 《Arabian Journal of Geosciences》2017,10(19):426
One of the most important quality and design parameters of natural rock materials is uniaxial compressive strength (UCS). UCS value of a building stone determines its application area such as cladding, roofing, facing, and coverings. In rock mechanics and engineering practice determination of UCS values of rock materials is suggested on core specimens whereas in construction and building stone sector, cubic specimens are suggested. In this experimental study, the effect of cubic specimen size on UCS values of some carbonate rocks which are being used as dimension stones are investigated. A total of 299 cubic specimens at five different edge sizes (3, 5, 7, 9, and 11 cm) from limestone, marble, and travertine are prepared. Chemical, petrographic analyses and physical properties of specimens are determined and after that UCS tests are carried out. It is observed that as the specimen sizes increase from 3 to 11 cm, average UCS values decrease about 7% for the tested carbonate rocks. In the light of this finding, results of UCS tests could be interpreted considering cubic specimen sizes for the same rock types in various fields. 相似文献