Characterization of Effective Parameters in Abrasive Waterjet Rock Cutting

The rock cutting performance of an abrasive waterjet is affected by various parameters. In this study, rock cutting tests are conducted with different energy (i.e., water pressure, traverse speed, and abrasive feed rate), geometry (i.e., standoff distance), and material parameters [i.e., uniaxial compressive strength (UCS)]. In particular, experimental tests are carried out at a long standoff distance (up to 60 cm) to consider field application. The effective parameters of the rock cutting process are identified based on the relationships between the cutting performance indices (depth, width, and volume) and parameters. In addition, the cutting efficiency is analyzed with effective parameters as well as different pump types and the number of cutting passes considering the concept of kinetic jet energy. Efficiency analysis reveals that the cutting depth efficiency tends to increase with an increase in the water pressure and traverse speed and with a decrease in the standoff distance and UCS. Cutting volume efficiency strongly depends on standoff distance. High efficiency of cutting volume is obtained at a long standoff distance regardless of the pump type. The efficiency analysis provides a realistic way to optimize parameters for abrasive waterjet rock excavation.     

Prediction of the Cut Depth of Granitic Rocks Machined by Abrasive Waterjet (AWJ)

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.     

Effects of Rock Properties on Specific Cutting Energy in Linear Cutting of Sandstones by Picks

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.     

岩石切削机理模型分析及实验研究

切削机理模型是研究岩石钻进切削过程中的切削力以及切削热的基础。在分析岩石切削机理模型的基础上,基于摩尔理论和裂纹扩展理论,分析中硬岩石切削状态,认为在中硬岩石切削过程中岩石存在着脆性切削和延展性切削2种方式,在此基础上得到新的中硬岩石切削机理模型。以砂岩、大理岩和花岗岩为钻进对象,开展微钻实验研究。结果表明：切削过程为岩石在刀具的扭矩和推进力作用下发生破坏,导致小岩屑、大切屑不断循环产生的过程,小大切屑形成主要源于岩石挤压变形和裂纹生成扩展。实验结果与岩石切削机理表现出较好的一致性。     

Surface Miners: Evaluation of the Production Rate and Cutting Performance Based on Rock Properties and Specific Energy

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.     

Experimental Study on Rock Failure Characteristics of Ejective Rock Burst Based on Energy Compensation

Geotechnical and Geological Engineering - Rock burst is a typical type of dynamic geological disaster in the process of underground engineering excavation under high in-situ stress. Based on the...     

基于模型约束的Kirchhoff积分法叠前深度成像

与时间域偏移方法比较,叠前深度偏移成像方法能够适应剧烈横向速度变化、陡倾角反射的地震资料。本文通过研究Kirchhoff叠前深度偏移方法成像原理,首先建立初始速度模型;然后在初始速度模型中加入了目标地质体--盐丘作为层位,对初始速度模型进行优化,在层位的约束下通过多次迭代计算,对优化前后的两个速度模型求取旅行时差更新初始速度模型;最后利用更新后的初始速度模型进行Kirchhoff积分法叠前成像。叠前时间偏移和模型约束下的Kirchhoff积分法叠前深度偏移成像结果显示,后者成像具有更高的信噪比和分辨率。     

Analytical Model of Stress Field and Failure Depth in Multilayered Rock Masses of Mining Floor Based on the Transfer Matrix Method

Accurate calculation of stress distribution and failure depth of coal seam floor is the key to the floor water inrush risk evaluation. In consideration of the fact that the floor rock masses are multilayered distribution due to deposition, this paper presents a mathematical model for calculating stress field and failure zones in the floor strata caused by coal mining. By the application of the Fourier transform, the transfer matrix describing the relationship between the abutment pressure of stope and the stresses in arbitrary depth of multilayered rock masses is derived in the transformed domain. Then, the actual solution in the physical domain can be obtained by the inversion of Fourier transform through a MATLAB program. Finally, numerical examples are presents to verify the model and study the influence of the layered rock mass properties on the stress distribution and failure depth of mining floor.     

Experimental and Statistical Evaluation of Cutting Methods in Relation to Specific Energy and Rock Properties

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.     

基于模糊层次分析法的岩石可爆性评价模型

提出了应用模糊层次分析法评价岩石可爆性的数学模型，阐述了该方法的基本原理和计算方法并结合实例说明了该方法的应用。     

Predicting the Building Stone Cutting Rate Based on Rock Properties and Device Pullback Amperage in Quarries Using M5P Model Tree

One of the key parameters that affect the selection of equipment and the cost estimation of dimension stone quarries is the rock cutting rate or production rate. In this study, the M5P tree algorithm is used to determine the relationship between the hard rock sawability and its factors especially the physical and mechanical characteristics of rock. To achieve the research goal, a variety of eleven types of hard dimension stone were selected and nine major physical and mechanical characteristics of rock including uniaxial compressive strength, Young’s modulus, Brazilian tensile strength, equivalent quarts content, grain size, Mohs hardness, point load test, density and P-wave velocity of these samples were evaluated. The cutting rate of diamond wire for all of the Workpiece was measured at different pullback amperage with a fully instrumented cutting platform in laboratory. All operational parameters of cutting process were entirely controlled. Thus, a database containing 99 datasets was provided and it has been used for analyses. The obtained results from the pruned and unpruned tree models showed a significant relationship between cutting rate and its factors. In the end, the results of M5P tree method were compared with statistical analyses (i.e., linear and nonlinear regression). The coefficient of determination be equal with 0.92, 0.86, 0.77 and 0.63 for unpruned tree, pruned tree, linear and nonlinear regression method respectively. This comparison showed that the both method of M5P tree technique have a better performance in predicting the cutting rate rather than the statistical regression methods.     

工程岩爆灾害判别的RBF-AR耦合模型

岩爆是深部高地应力区地下岩体工程中的主要工程地质灾害之一,其发生及烈度预测是一个复杂的不确定系统问题。为了有效预测和判别深部工程岩爆灾害,在总体考虑岩爆各影响因素的基础上,选取地下工程中岩体完整性指数、岩石单轴抗压强度、岩石单轴抗拉强度、围岩最大切向应力、围岩抗压强度与其抗拉强度的比值、围岩切向应力与围岩抗压强度比值、弹性能量指数、岩爆倾向性指数作为岩爆预测的评判指标,提出了一种基于非线性参数优化的RBF-AR岩爆预测模型。在终南山隧道竖井岩爆判别中,利用RBF-AR法进行计算,计算结果与实际情况完全一致,表明该模型在岩爆预测中的可行性和有效性。     

基于三维数字地质模型的地质空间动态剪切分析技术

基于三维数字地质模型的地质空间剪切分析是"玻璃国土"建设所面临的关键技术之一。其难点包括复杂三维数据环境中的高效实体布尔运算方法,以及相关三维实体语义信息的实时查询处理。采用基于BSP树的多边形合并与分解技术,实现三维空间实体的布尔运算与矢量剪切;采用多线程实现不同要素集合的并行裁剪运算,并在三维空间数据库引擎的支持下,进一步提升地上地下一体化信息处理和语义查询效率。以武汉市规划信息系统为例,实现了地下硐室和隧道动态开挖过程的三维地质空间剪切分析,并结合水利水电工程地下厂房设计和矿山三维巷道设计实例,说明了基于三维数字地质模型的地质空间分析的综合应用效果。     

基于HPSO算法的岩石非定常蠕变本构模型辨识

复合微粒群优化(HPSO)是一类随机全局优化技术,具有搜索能力强、收敛速度快、搜索精度高的优点.针对岩石蠕变本构模型非定常参数的辨识问题,利用FLAC软件自带的fish语言实现了HPSO算法对非定常参数的辨识.该方法从非定常参数的随机值出发,以蠕变过程中试件变形的实验值与计算值的误差大小作为适应度函数来评价参数的品质,...     

岩石爆破不同掏槽形式的对比分析

在对不同掏槽形式进行对比分析的基础上,结合工程实例,试验分析了不同掏槽形式下的爆破效果,认为斜眼掏槽和直眼掏槽都存在各自的缺陷,提出采用和推广准直眼掏槽方式的建议。     

Analysis of Rock Damage Characteristics Based on Particle Discrete Element Model

Rock is a heterogeneous medium that is composed of minerals of various sizes. Under the action of external loads, the generation, propagation and coalescence of microdefects in the rock mass determines the macroscopic deformation and fracture of rock. To understand the damage law of rock and to reveal the evolution of dynamic failure, a uniaxial compression model was established based on particle flow code. Acoustic emission and energy characteristics of rock damage were analyzed, and the damage constitutive models of rock were discussed. During rock uniaxial compression, acoustic-emission events undergo a relatively quiet, sudden increase and sharp decrease for three periods, which corresponds to the compaction and elastic deformation stage, yield stage and post-peak stage in the stress–strain curve. Before the yield stress is reached, the proportion of bond and strain energies is larger. Friction energy accounts for a small proportion of the total energy, and a reciprocal relationship exists between them. The constitutive model that is based on friction energy can better reflect the variation in stress and strain, then the constitutive model based on acoustic-emission parameters.     

基于岩石物理模型的碳酸盐岩储层微观孔隙特征分析方法

碳酸盐岩储层的微观孔隙结构普遍具有类型复杂和纵向变化快的特征。由于地球物理资料尺度的限制,现有的解释手段不能有效刻画这些关键特征。笔者采用临界孔隙度模型作为理论依据,建立了微观孔隙结构与宏观弹性参数响应之间的定量关系;以岩石物理实验数据为约束,提出了一种基于概率统计学的方法估算储层关键参数并识别岩石孔隙类型。在YS1井的应用表明：新方法有效挖掘了声波测井数据中隐含的微观信息,参数预测结果达到较高的精度（平均相对误差小于10%）,可以为优质储层段的划分提供可靠的参考依据。