共查询到20条相似文献，搜索用时 718 毫秒
1.
目前关于锥形PDC齿的研究主要集中于数值模拟、现场及室内试验,而关于其切削力学特性的理论分析未见相关报道。通过数值模拟阐述了锥形PDC齿拉伸剪切破岩机理,以及切削载荷分布特性;根据能量平衡原理,推导了锥形PDC齿切削载荷理论公式。结果表明,相比于常规PDC齿,锥形PDC齿破岩过程更加稳定,其切削载荷受岩石性质、齿的形状参数、切削深度以及切削角度的影响,且切削载荷随着锥顶半径、切削角度以及吃入岩石深度的增加而增加。研究成果可为锥形PDC齿及钻头的设计提供理论支撑。 相似文献
2.
Deniz Tumac 《Rock Mechanics and Rock Engineering》2014,47(2):703-715
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.
Effects of Rock Properties on Specific Cutting Energy in Linear Cutting of Sandstones by Picks 总被引：4，自引：2，他引：4
Summary. Specific cutting energy (SE) has been widely used to assess the rock cuttability for mechanical excavation purposes. Some
prediction models were developed for SE through correlating rock properties with SE values. However, some of the textural
and compositional rock parameters i.e. texture coefficient and feldspar, mafic, and felsic mineral contents were not considered.
The present study is to investigate the effects of previously ignored rock parameters along with engineering rock properties
on SE. Mineralogical and petrographic analyses, rock mechanics, and linear rock cutting tests were performed on sandstone
samples taken from sites around Ankara, Turkey. Relationships between SE and rock properties were evaluated using bivariate
correlation and linear regression analyses.
The tests and subsequent analyses revealed that the texture coefficient and feldspar content of sandstones affected rock cuttability,
evidenced by significant correlations between these parameters and SE at a 90% confidence level. Felsic and mafic mineral
contents of sandstones did not exhibit any statistically significant correlation against SE. Cementation coefficient, effective
porosity, and pore volume had good correlations against SE. Poisson’s ratio, Brazilian tensile strength, Shore scleroscope
hardness, Schmidt hammer hardness, dry density, and point load strength index showed very strong linear correlations against
SE at confidence levels of 95% and above, all of which were also found suitable to be used in predicting SE individually,
depending on the results of regression analysis, ANOVA, Student’s t-tests, and R2 values. Poisson’s ratio exhibited the highest correlation with SE and seemed to be the most reliable SE prediction tool in
sandstones. 相似文献
4.
Estimating the Peak Indentation Force of the Edge Chipping of Rocks Using Single Point-Attack Pick 总被引：1，自引：0，他引：1
This article establishes a new model for estimating the peak indentation force of the edge chipping of rocks when using a
conical or a pyramidal point-attack pick. The investigation points out that the existing formulation in the literature is
based on an inappropriate stress assumption and equilibrium, and hence leads to incorrect cutting force estimations. The new
model developed in this study is based on an analysis of the penetration force and energy dissipation using fracture mechanics,
similarity of chip geometry, and edge chipping tests on four different rock materials. It is found that the peak indentation
force and the depth of cut follow a power law, that the new model can reasonably estimate the experimental measurements, and
that it provides useful information for the shape optimization of point-attack picks in mechanical excavation. 相似文献
5.
根据截齿侵入岩石的断裂特征和相关试验数据,分析了破岩机制及不同截线间距对破岩效果的影响。在单刀旋转截割试验平台上,以不同切削深度和截线间距进行组合试验,并结合比能耗、粗度指数及截割载荷3个评价指标,对截线间距进行优化,研究截割该类型砂岩时截线间距与切削深度的最佳比值。试验结果表明,岩石在单齿旋转截割作用下的破碎过程大致可以分为初始压碎区细粒岩屑生成、密实核形成并储能、各向裂纹的扩展与连通、断裂体崩落、二次压碎区细粒岩屑生成5个阶段,且岩屑的断裂是以拉伸为主并伴随着挤压和剪切的共同作用;在最佳截割条件下,粗度指数较高,岩屑成块率增加,且比能耗低。通过分析岩石破碎过程及对截线间距的优化,可为掘进机破岩机制研究及截齿布置提供参考。 相似文献
6.
Non-ideality in mineral solid solutions affects their elastic and thermodynamic properties, their thermobaric stability, and the equilibrium phase relations in multiphase assemblages. At a given composition and state of order, non-ideality in minerals is typically modelled via excesses in Gibbs free energy which are either constant or linear with respect to pressure and temperature. This approach has been extremely successful when modelling near-ideal solutions. However, when the lattice parameters of the solution endmembers differ significantly, extrapolations of thermodynamic properties to high pressures using these models may result in significant errors. In this paper, I investigate the effect of parameterising solution models in terms of the Helmholtz free energy, treating volume (or lattice parameters) rather than pressure as an independent variable. This approach has been previously applied to models of order–disorder, but the implications for the thermodynamics and elasticity of solid solutions have not been fully explored. Solid solution models based on the Helmholtz free energy are intuitive at a microscopic level, as they automatically include the energetic contribution from elastic deformation of the endmember lattices. A chemical contribution must also be included in such models, which arises from atomic exchange within the solution. Derivations are provided for the thermodynamic properties of n-endmember solutions. Examples of the use of the elastic model are presented for the alkali halides, pyroxene, garnet, and bridgmanite solid solutions. Elastic theory provides insights into the microscopic origins of non-ideality in a range of solutions, and can make accurate predictions of excess enthalpies, entropies, and volumes as a function of volume and temperature. In solutions where experimental data are sparse or contradictory, the Helmholtz free energy approach can be used to assess the magnitude of excess properties and their variation as a function of pressure and temperature. The formulation is expected to be useful for geochemical and geophysical studies of the Earth and other planetary bodies. 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.
为了解决竖井冻土开挖难度大、人工挖掘效率低的问题,研究发明了一种新型重力式竖井掘进机,该掘进机利用截齿连续滚动向下、行走式掘进冻土,在竖井冻土掘进中具有较好的适应性,而截齿侵入深度是影响掘进冻土效率的重要因素。先采用三维软件建模,通过霍普金森压杆冲击试验,结合HJC压缩损伤模型原始参数,优化得到冻土本构模型参数;再利用有限元分析软件耦合,模拟截齿在不同侵入深度下滚动掘进冻土,得到冻土在不同凹陷破坏深度下的截齿三向力、冻土应力和应变的变化规律,便于直观研究截齿掘进冻土过程,寻求最优截齿侵入深度。仿真结果表明：随着截齿侵入深度增加,截齿三向力变大,冻土凹陷面积扩大,冻土应力向下无边界扩展递减;冻土与截齿接触区域应力、应变最大,远离截齿作用时冻土区域的应力、应变逐渐递减,其变化规律与截齿连续滚动掘进冻土特征相关;当冻土单轴抗压强度为9 MPa时,截齿滚动掘进冻土过程存在最优截齿侵入深度,为4 cm,此时冻土破坏特征明显,截齿滚动掘进冻土效率最高且能耗低。 相似文献
9.
冻土机械切削破碎机理的研究进展 总被引：1，自引：1，他引：0
冻土开挖困难、破碎效率低是高寒地区工程建设、地基施工等面临的技术难题。冻土机械切削破碎是冻土开挖的主要方法,其机理研究是提高冻土破碎效率的前提和基础。首先总结了温度、含水率、围压等对冻土复杂力学特性的影响,进而调研分析了冻土机械切削破碎的典型切削力学模型,发现冻土切削机械破碎模式不仅与冻土力学特性密切相关,也与切削参数和刀具结构直接相关,冻土切削过程中存在着最优的切削前角（30°~60°）,且深切削和浅切削时冻土内部受力方式存在差异也会导致破坏形式的不同;温度、含水率、围压所造成的冻土力学性能变化会直接导致冻土破坏过程和切削破碎机理的改变,冻土强度随着温度降低表现出先升高然后保持稳定的特性,随着含水率升高呈现出先升高后降低的趋势,冻土破碎存在脆性、塑脆过渡及塑性等不同破坏形式。通过系统总结冻土切削破碎机理研究进展,进一步明确了冻土力学性质主要影响因素、变化特点及其切削破坏损伤特征,为冻土机械切削破碎的切削参数和切削具结构优化提供了设计依据。 相似文献
10.
结合外载碎岩基本现象,对旋挖碎岩基本过程进行分析,得出其在回转钻进情况下的螺旋破碎的碎岩形式。然后根据岩石破碎时的压入条件,以单个截齿为研究模型,得出轴向压力的理论计算公式,继而参考库伦纳维的内摩擦理论,得出了切削力的理论计算公式。根据不同钻具形式,将单个截齿的计算公式扩展,得到了旋挖钻机压力和扭矩参数的计算公式。将轴向力与切削力计算公式中在特定工况下的影响因子简化,得出了旋挖钻机钻进过程中进尺速度与切削力的理论关系。最后利用LS-DYNA动态分析软件模拟了单个截齿在不同侵深条件下的切削力变化曲线,并将曲线与同等工况下理论计算的曲线进行对比,得出单个截齿的入岩参数理论计算公式。可为入岩旋挖钻机设计提供参考。 相似文献
11.
12.
A two dimensional non-linear finite element simulation model has been developed using a mathematical model for progressive
rock failure for understanding the mode and sequence of rock failure under a drag pick cutter. Rock cutting simulation has
also been done using linear elastic modeling using local stability factor contouring. It has been observed from the simulation
results that during negative rake angle cutting the chipping occurs by shear failure of the elements. Whereas, in positive
rake angle cutting, some elements were observed to fail in shear and some under tension. The predicted peak cutting force
using the developed models was found to be up to 25% higher than the experimental values. The effect of input parameters such
as rake angle, flank wear, depth of cut and rock properties on the predicted peak cutting force has been studied, verified
from earlier experimental studies and compared with some earlier proposed theories on rock cutting. The elastic stress analysis
model based on the stability factor contouring method has also been found to be an effective tool to bracket the expected
peak cutting force for a given operational and rock parameters but failed to simulate the effect of pick geometry (rake angle)
correctly. The non-linear simulation model using progressive rock element failure is superior to elastic linear stress analysis
model by simulating the correct trends for all the rock and machining parameters. 相似文献
13.
为研究岩石切削过程中刀具的力学特性以及刀具平均峰值作用力的预测,基于断裂力学和有限元理论建立了岩石切削的数值模型。模拟分析岩石对刀具的反作用过程,得到不同力学特性岩石和刀具作用条件下刀具所受的反作用力,结果表明,冲击速度在一定范围内对刀具平均峰值作用力影响较小;岩石体积呈阶跃性递减,刀具作用力大小与崩落岩石碎片体积变化一致。对模拟、实验以及已有理论计算得到的刀具平均峰值作用力进行线性回归分析,研究结果表明,数值方法计算结果与实验结果、Goktan[1]理论计算结果的线性相关系数分别为0.812、0.930,相关性较好,表明所建数值模型用于模拟岩石切削是正确和可靠的。 相似文献
14.
M. Mirahmadi M. Tabaei M. Soleiman Dehkordi 《Geotechnical and Geological Engineering》2017,35(5):1991-2002
The specific energy (SE) is the most important parameter to estimate the energy consumption in tunnel boring machines (TBMs). It is defined as the amount of required energy to excavate a unit volume of rock mass which used to predict the performance of TBMs. Several models are used to estimate the SE based on different parameters such as the rock mass properties, disc cutter dimensions and cutting geometry. The aim of this work is to propose new relations between the SE and the strain energy of rock mass (W) using the geological mappings of rock mass and TBM operational parameters from Amir-Kabir Water Transferring Tunnel of Iran. W is an appropriate criterion to estimate SE because it is a function of different parameters such as rock mass behavior, pre and post failure properties and peak and residual strains. In this study, to increase the correlation coefficient of relation between the mentioned parameters, the rock mass is classified in two methods, in the first method according to the geological strength index (GSI) all data is classified in three classes such as weak, fair and good and in the second method using the drop to deformation modulus ratio (η) the classification of data is performed in three classes such as η < 0.05, 0.05 ≤ η < 10 and η ≥ 10. The results show that there are direct relations between both parameters. It is suggested to estimate SE in all rock mass classes using the proposed relations based on GSI classification. 相似文献
15.
锥形聚晶金刚石复合片(polycrystalline diamond compact,PDC)齿是一种具有较强抗冲击性和耐磨性的新型PDC齿,在坚硬、强研磨性和软硬交错地层中取得了非常好的钻井提速效果。为了揭示锥形齿破碎硬岩机制,开展锥形齿破碎花岗岩试验与数值模拟研究,分析了切削深度和前倾角对锥形齿切削力和破岩比能的影响规律,采用高速摄像机和透明K9玻璃观测了锥形齿作用下岩屑形成过程及微裂纹萌生与扩展过程,通过数值模拟分析了破岩过程中岩石应力响应与损伤演化特性,结合对切削槽和大尺寸块体岩屑表面形貌及断口微观特征分析,建立了锥形齿破碎花岗岩机制模型。结果表明,锥形齿破碎花岗岩的过程可以分为挤压成核和块体崩裂两个阶段,前倾角对岩石破碎过程影响较小,切削深度的影响显著;锥形齿周围的裂纹主要由压实核、纵向裂纹和横向裂纹组成,纵向裂纹和横向裂纹扩展的最大深度分别为切削深度的6.69倍和4.53倍;齿尖周围压应力集中,岩石发生压剪破坏,压应力区外围形成弧形条带状拉应力区,并在齿尖及压应力区边界处诱导出拉伸微裂纹;微裂纹向齿前扩展形成弧形拉伸主裂纹,发生块体岩屑崩裂,提高破岩效率,向岩石内部扩展劣化... 相似文献
16.
Certain rock properties that depend on intergranular fracture and frictional sliding appear to be independent of rock type. This relationship is true for the rock-on-rock frictional sliding coefficient. The generalization has been widely applied to geomechanical modelling of upper crustal strength. Porous sandstones can be relatively weak and poorly cohesive, hence susceptible to deformation involving grain fragmentation and pore collapse. The critical state theory is commonly applied to describe such behaviour. Previous work showed that the yield surface is substantially independent of rock type when mean stress and differential stress are normalized by the grain crushing pressure, implying that the critical state line is rock type-independent and equivalent to the frictional sliding criterion. We test these hypotheses using previously published data for a range of porous sandstones augmented by new experimental results on Hollington and Berea sandstones deformed to large strains to define the critical state line over a wide range of pressures for each rock type. Results confirm the rock type-independence of the critical state line and show that it is nearly equivalent to frictional sliding. These relationships point to a simple procedure for estimating approximately the mechanical properties of sandstones based only on petrographic characteristics. 相似文献
17.
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
18.
Estimation of Rock Cuttability from Shore Hardness and Compressive Strength Properties 总被引：6，自引：1，他引：6
Summary Shore hardness has been used to estimate some mechanical and physical properties of rocks for many years. This study differs
from previous studies in a way that it is directly oriented to rock cuttability. Two Shore hardness values (SH
1 andSH
2) and a coefficient of deformation value (K) have been measured for 30 different rock samples. In the first stage of the study, optimum specific energy values for 16
different rock samples obtained from full-scale cutting tests were correlated with the Shore hardness values of the same rock
samples changingSH
1 values from 9 to 66 andSH
2 values from 25 to 83, with deformation coefficient values changing from 26 to 195. In the second stage, the performance of
a roadheader used in the Kü?üksu (Istanbul) tunnel was recorded in detail and the instantaneous cutting rate of the machine
was determined. Then, the relationship between Shore hardness values, deformation coefficient and the instantaneous cutting
rate of the machine was determined for different formations encountered. It is concluded that there is a relationship between
Shore hardness values, optimum specific energy and compressive strength, which may be used to estimate the rock cuttability
and the instantaneous cutting rates of roadheaders within certain limits of reliability. 相似文献
19.
Michael Hood 《Geotechnical and Geological Engineering》1985,3(2):91-111
Summary A review of the benefits of assisting mechanical tools, notably drag bits, with moderate pressure waterjets suitably directed with respect to the bit is given. These benefits include reduced bit forces, especially the bit normal force, reduced bit wear, reduced dust make, and reduced incidence of frictional sparking. The research work that has been conducted to date to investigate this phenomenon has been empirical in nature. Experiments are described that extend the data bank of this empirical knowledge. In addition, experiments aimed at gaining a better understanding of the fundamentals of the rock fragmentation process with this hybrid cutting method are outlined.Results from the first of these experimental series are used to make recommendations as to the position of the jet with respect to the bit, the stand-off distance between the nozzle exit and the bit/rock interface, and the jet energy. In addition, preliminary findings are reported regarding the increase necessary in the jet energy when the bit velocity is increased. Results from the second test series are discussed in the context of rock fracture behaviour induced by mechanical bits acting alone. The likely influence of waterjets on these fracture processes is analysed. It is concluded that, in terms of the bit force reductions, a dominant influence of the jets when used in conjunction with sharp drag bits, is continuous removal of the rock debris that forms ahead of the advancing bit. The observed reductions in bit wear and incidence of frictional sparking are attributed to reduced heat loading of the bit during the cutting operation. Reductions in the dust make are attributed to effective wetting of the fine rock particles before they become entrained in the airstream. 相似文献
20.
As the use of mechanical excavation in tunneling and mining activities expands, so has the use of disc cutters in various ground conditions. The impact of moisture content on rock behavior and rock excavation by disc cutters is examined in this study. This was done through a series of full-scale cutting tests using a 292 mm (11.5 in.) disc cutter in a moderate strength sandstone. The muck from the cutting tests was used to determine coarseness index (CI) and absolute size constant (x′). x′ was calculated using Rosin–Rammler distribution (or Weibull) curve, a statistical technique to look at the fragmented rock products. This approach is very popular among the mineral-processing professionals for the evaluation of the particle sizes of the comminution products. x′ and CI show a reasonable correlation with the specific energy of cutting and production rate. Both of these indicators were found to be dependent on the cut spacing and the interaction between the adjacent cuts, as anticipated. This paper explains the background information on this topic, reviews the laboratory testing, and offers analysis of the results of grain size distribution and its relationship with specific energy and cutting geometry. It should be noted that the experimental program was limited to only one rock type and additional testing on the other rock types is required to expand the results of the current study. 相似文献