共查询到20条相似文献，搜索用时 421 毫秒
1.
This paper proposes a new method using centroid sliding pyramid (CSP) to identify the removability and stability of fractured hard rock in tunnel and slope engineering. The new method features two geometrical and topological improvements over the original key block method (KBM). Firstly, all the concave corners are considered as starting points of cutting process when a concave block is divided into a set of convex blocks in the original KBM. Only the concave corners formed by two joint planes are used for partitioning a concave block in the presented method and concave corners with free planes are excluded. Secondly, joint pyramid for removability computation in the original KBM is generated using all of the joint planes, while CSP is calculated only from the joint planes adjoining the free planes. The cone angle θ of CSP is the vectorial angle formed by the two candidate sliding surfaces of this CSP. Removability analysis of a block is transformed into calculating the cone angle of CSP. The geometrical relationship is simplified, and data size for removability computation is reduced compared with the original KBM. The provided method is implemented in a computer program and validated by examples of fractured rock slopes and tunnels. 相似文献
2.
Local and Spatial Joint Frequency Uncertainty and its Application to Rock Mass Characterisation 总被引：1，自引：1，他引：0
Stability is a key issue in any mining or tunnelling activity. Joint frequency constitutes an important input into stability
analyses. Three techniques are used herein to quantify the local and spatial joint frequency uncertainty, or possible joint
frequencies given joint frequency data, at unsampled locations. Rock quality designation is estimated from the predicted joint
frequencies. The first method is based on kriging with subsequent Poisson sampling. The second method transforms the data
to near-Gaussian variables and uses the turning band method to generate a range of possible joint frequencies. The third method
assumes that the data are Poisson distributed and models the log-intensity of these data with a spatially smooth Gaussian
prior distribution. Intensities are obtained and Poisson variables are generated to examine the expected joint frequency and
associated variability. The joint frequency data is from an iron ore in the northern part of Norway. The methods are tested
at unsampled locations and validated at sampled locations. All three methods perform quite well when predicting sampled points.
The probability that the joint frequency exceeds 5 joints per metre is also estimated to illustrate a more realistic utilisation.
The obtained probability map highlights zones in the ore where stability problems have occurred. It is therefore concluded
that the methods work and that more emphasis should have been placed on these kinds of analyses when the mine was planned.
By using simulation instead of estimation, it is possible to obtain a clear picture of possible joint frequency values or
ranges, i.e. the uncertainty. 相似文献
3.
一种新的岩石节理面三维粗糙度分形描述方法 总被引：1，自引：0，他引：1
研究并提出一种新的岩石节理面三维粗糙度分形描述方法。首先,基于激光扫描数据将节理表面离散成三角网,并建立与剪切方向相关的三维均方根抵抗角的计算方法。其次,运用分形数学理论,提出一种新的基于三维均方根抵抗角的节理面粗糙度分形描述方法。最后,采用新方法对天然玄武岩节理和花岗岩张拉型节理的粗糙特性进行分析。研究结果表明,提出的新方法能够较全面地反映节理面的三维几何形貌信息,并能描述节理粗糙度的各向异性特性。研究成果为进一步建立岩石节理面的三维剪切强度公式和剪切本构理论奠定了基础。 相似文献
4.
水文频率分析计算过程中,水文极值样本系列容量一般都较小、代表性不高,使得水文设计值估计具有不确定性。利用Bootstrap方法,研究样本抽样不确定性对水文设计值的影响。与传统水文频率分析方法相比,基于Bootstrap方法不仅可提供设计值的点估计和区间估计,同时能够对设计值的不确定性进行定量评价。此外,基于Bootstrap技术,结合矩法、权函数法及线性矩法,设置3套方案,分析了该方法在不同参数估计方法间的有效性。以南通市1970-2011年共42年的年降雨量数据资料为例,对所提方法进行实例应用分析,结果表明,从期望设计值、90%置信区间及最终设计值角度而言,基于所提方法的设计成果受参数估计方法的选取影响不大,且可回避规范中B值诺莫图通用性较差及误差显著问题。 相似文献
5.
节理中接触面积的存在使得渗流曲折效应更加明显,将对渗流产生显著影响。为了研究节理接触面积对节理渗流的影响,建立节理渗流概念模型,推导得到了节理渗流的接触面积影响系数;然后在节理渗流计算公式中引入该影响系数,得到了考虑接触面积影响的渗流计算公式。同时,由于接触面积的存在使得渗流曲折因子的计算更为复杂,在获得节理隙宽分布的基础上提出了计算节理渗流曲折因子的五点比较法。然后以人工大理岩节理试件为研究对象,在获得其三维表面形貌的基础上,一方面对其进行不同接触状态下5级法向应力作用下的渗流试验;另一方面,在根据节理试件的三维表面形貌数据计算节理的渗流平均曲折因子和接触面积比的基础上,分别采用考虑接触面积影响的渗流计算公式和Zimmerman计算公式对节理试件在不同法向应力作用下的渗流体积流量进行计算,并将计算结果与实测值进行比较。结果表明：考虑接触面积影响的渗流计算公式计算结果与实测值吻合较好,从而验证了考虑接触面积影响的渗流计算公式的正确性,而Zimmerman计算公式高估了节理的渗流流量。 相似文献
6.
7.
Summary The geometry of the rock joint is a governing factor for joint mechanical and hydraulic behaviour. A new method for evaluating
the aperture distribution, based on measurement of joint surfaces and three dimensional characteristics of each surface, is
developed. This method allows one to determine and visualize the aperture distribution under different normal stresses and
shear displacements, which is difficult to observe experimentally. A new laser scanner system is designed and developed for
joint surface measurements. Special attention is paid to both surfaces’ data gained by measurements and processing, such as
x-y coordinate table modification, data referencing, and matching between upper and lower surfaces. The surfaces of an artificial
joint in granite are measured, processed, analyzed and three dimensional approaches are carried out for surface characterization.
Parameters such as “asperity’s heights”, “slope angles”, and “aspects” distribution at micro scale, local concentration of
elements and their spatial localization at local scale are determined by Geographic Information System (GIS). These parameters
are used for joint surfaces matching and its real behavior quantitative analysis. The upper surface is brought down to make
contact with the lower surface and the distance between the two surfaces is evaluated from the joint mean experimental aperture,
which is obtained from normal and shear tests. Changes of aperture distribution at different normal stresses and various shear
displacements are visualized and interpreted. Increasing normal load causes negative changes in aperture frequency distribution
which indicates high joint matching. However, increasing shear displacement causes a rapid increase in the aperture and positive
changes in the aperture frequency distribution, which could be due to un-matching, surface anisotropy and spatial localization
of contact points with proceeding shear.
Author’s address: Mostafa Sharifzadeh, Department of Mining, Metallurgy and Petroleum Engineering, Amirkabir University of
Technology, Hafez 424, Tehran 15875-4413, Iran 相似文献
8.
Observed frequencies of joint orientations are subject to error due to sampling bias. This error should be corrected before statistical inference is made on the distribution of orientation. Corrections (weighting functions) are developed for sampling bias in orientation for finite joints of different sizes and shapes intersecting rectangular exposures. Chi-square goodness-of-fit procedures available for hemispherical normal and bivariate normal distributions are modified to make them applicable for both raw data and data corrected for sampling bias. The aforementioned corrections and procedures were applied to a joint orientation cluster to study the effect of (a) joint orientation, (b) joint size and (c) joint shape, on the statistical distribution of the orientation. The influences of all these aforementioned factors were found to be significant. However, at present, joint sizes and shapes are not measured in field joint surveys. Therefore, it is suggested to make attempts to obtain joint sizes and shapes in field joint mapping surveys. Since the currently available probability distributions are not adequate to represent all joint orientation distributions, it is suggested either to look for new probability distributions or to develop procedures to use empirical distributions in modelling orientation distributions. 相似文献
9.
H. H. W. Herda 《Rock Mechanics and Rock Engineering》2006,39(2):147-158
Summary. A computational algorithm which uses depth data from a reference plane to a rock fracture surface in calculating a new three-dimensional
joint roughness coefficient is presented. Two independent sets of fracture data are investigated. The new coefficient is compared
to Barton’s 2D joint roughness coefficient JRC. A measure indicating corrupt data is discussed. The algorithm is also used
to show that, in general, rock roughness is only a local variable, not a directional one. 相似文献
10.
卫星气象产品、气候模式预测数据通常与地面观测数据存在偏差,为保证数据的可靠性和合理性,需要对其进行偏差校正,但偏差校正过程往往受具体区域气象特征、方法本身假定等因素的影响,导致修正效果不佳。为此,本文提出一种广义联合偏差修正方法,相较于现有研究最常用的单变量QM修正方法以及固定多变量修正顺序的JBC修正方法,该方法充分考虑到流域尺度降水和气温双变量的时空相关性,并结合其对径流的主导作用对变量修正顺序进行动态调整,实现了QM法和JBC法的优势互补。在澜沧江-湄公河流域的应用表明：考虑降水、气温相关性可显著改善降水和温度极值的修正效果,尤其是5、6月份,修正后气象与实测数据的纳什系数提升了0.5以上;考虑气象要素的修正次序显著降低了修正后的降水和温度频率分布及均值偏差;利用修正后的气象数据驱动分布式水文模型时,部分月份的径流模拟精度提升了54.3%。 相似文献
11.
针对目前节理岩体损伤变量定义中大多仅考虑节理长度、倾角等几何性质,而未考虑节理抗剪强度等力学性质的不足,基于断裂力学中的由于单个节理存在引起的附加应变能增量与损伤力学中的损伤应变能释放量相关联的观点,推导出了在双轴应力下含单条非贯通闭合节理岩体的损伤变量计算公式,并根据断裂力学理论对双轴压缩荷载下的单个节理尖端应力强度因子计算方法进行了研究,得出了应力强度因子KⅠ、KⅡ的计算公式;同时考虑多节理间的相互作用,给出了单组单排及单组多排非贯通节理尖端应力强度因子计算公式,由此建立了相应的节理岩体双轴压缩损伤本构模型,并利用该模型进行了相应的算例分析。结果表明：对含单条非贯通闭合节理的岩体而言,当节理倾角小于其内摩擦角时,岩体强度与完整岩石相同,岩体损伤为0,而后随着节理倾角增加,岩体强度、损伤随节理倾角的变化分别呈开口向上及向下的抛物线,当节理倾角约为60°时,岩体损伤最大,强度最低。随着节理长度增加,岩体损伤增加,而随着节理内摩擦角的增加,岩体损伤则减小;对含单组单排非贯通闭合节理的岩体而言,当节理总长度一定时,随着单条节理长度的减小及节理条数的增加,岩体损伤则逐渐减小,但其减小幅度与节理条数并不呈线性关系。 相似文献
12.
Spatial interpolation has been frequently encountered in earth sciences and engineering.A reasonable appraisal of subsurface heterogeneity plays a significant role in planning,risk assessment and decision making for geotechnical practice.Geostatistics is commonly used to interpolate spatially varying properties at un-sampled locations from scatter measurements.However,successful application of classic geostatistical models requires prior characterization of spatial auto-correlation structures,which poses a great challenge for unexperienced engineers,particularly when only limited measurements are available.Data-driven machine learning methods,such as radial basis function network(RBFN),require minimal human intervention and provide effective alternatives for spatial interpolation of non-stationary and non-Gaussian data,particularly when measurements are sparse.Conventional RBFN,however,is direction independent(i.e.isotropic)and cannot quantify prediction uncertainty in spatial interpolation.In this study,an ensemble RBFN method is proposed that not only allows geotechnical anisotropy to be properly incorporated,but also quantifies uncertainty in spatial interpolation.The proposed method is illustrated using numerical examples of cone penetration test(CPT)data,which involve interpolation of a 2D CPT cross-section from limited continuous 1D CPT soundings in the vertical direction.In addition,a comparative study is performed to benchmark the proposed ensemble RBFN with two other non-parametric data-driven approaches,namely,Multiple Point Statistics(MPS)and Bayesian Compressive Sensing(BCS).The results reveal that the proposed ensemble RBFN provides a better estimation of spatial patterns and associated prediction uncertainty at un-sampled locations when a reasonable amount of data is available as input.Moreover,the prediction accuracy of all the three methods improves as the number of measurements increases,and vice versa.It is also found that BCS prediction is less sensitive to the number of measurement data and outperforms RBFN and MPS when only limited point observations are available. 相似文献
13.
压制地震资料中工业电干扰的 余弦逼近法的改进及应用 总被引：1，自引：0，他引：1
在对实际资料分析的基础上, 笔者提出对工业电干扰频率进行精细扫描、标准余弦信号超采样及深层振幅统计等方法对目前常用的余弦逼近法进行改进, 理论分析及实际资料的处理结果对比表明了改进后的方法更实用、精度更高。 相似文献
14.
由于结构面粗糙度具有各质异性、各向异性、非均一性和尺寸效应等特征，结构面粗糙度系数（JRC）取值具有不确定性，工程中广泛采用统计方法来分析结构面粗糙度性质，然而以往研究往往忽略样本数不足对统计结果的影响。针对结构面粗糙度统计测量时无法确定合理样本数的问题，分别提出基于变异系数级比分析及简单随机抽样原理的最小样本数确定方法。以实际工程岩体结构面表面数据为研究对象，对比分析两种方法在系列尺寸下确定的统计测量最小样本数。实例分析表明：小尺寸样本的变异系数（CV）值明显大于大尺寸样本，且CV值随取样尺寸的增大而减小，取样尺寸为10～50 cm的CV值基本稳定在0.31～0.47之间，取样尺寸为60～100 cm的CV值基本稳定在0.21～0.31之间；最小样本数与取样尺寸基本满足幂函数关系，且最小样本数随取样尺寸的增大而减少；系列尺寸下级比分析方法在允许误差为±2%时确定的最小样本数与简单随机抽样原理在最大允许误差为10%、置信度为95%时计算的最小样本数是一致的，相似度大于0.997。该研究方法可为工程岩体中定量获取结构面粗糙度统计测量最小样本数提供依据，保证了JRC（结构面粗糙度系数）统计测量结果的准确性，对工程岩体稳定性评价中结构面力学参数的准确获取具有重要意义。 相似文献
15.
This work deals with the joint simulation of copper grade (as a continuous regionalized variable) and rock type (as a categorical variable) in Lince–Estefanía deposit, located in northern Chile. The region under study is heterogeneous, containing three main rock types (intrusive, andesite and breccia bodies) with different copper grade distributions. To perform joint simulation, the multi-Gaussian and pluriGaussian models are used in a combined form. To this end, three auxiliary Gaussian random fields are considered, one for simulating copper grade, up to a monotonic transformation, and two for simulating rock types according to a given truncation rule. Furthermore, the dependence between copper grade and rock types is reproduced by considering cross correlations between these Gaussian random fields. To investigate the benefits of the joint simulation algorithm, copper grade and rock types are also simulated by the traditional cascade approach and the results are compared. It is shown that the cascade approach produces hard boundaries, that is, abrupt transitions of copper grades when crossing rock-type boundaries, a condition that does not exist in the study area according to the contact analysis held on the available data. In contrast, the joint simulation approach produces gradual transitions of the copper grade near the rock-type boundaries and is more suited to the actual data. 相似文献
16.
Estimating species diversity: Comparison of two algorithms 总被引：2，自引：0，他引：2
Pascal de Caprariis 《Mathematical Geology》1984,16(3):237-248
Two approaches to estimating the number of species in a lithologic unit are compared. An empirical model of the sampling process, which involves fitting the equation of a rectangular hyperbola to the data from a collector's curve, is compared with a logarithmic model derived from a statistical theory of sampling. The two approaches give equally accurate estimates of species richness when organisms are randomly dispersed but the logarithmic model generally requires more sampling than the hyperbolic model. 相似文献
17.
This paper deals with two shortcomings of the smooth-joint contact model (SJCM) used in the particle flow code (PFC). The first shortcoming is the increase of the shear strength of the joint when the shear displacement of the joint exceeds a specific value that is related to the particle size. This problem is named as the interlocking problem, which is caused by the interlocking particles. It occurs due to a shortcoming of the updating procedure in the PFC software related to the contact conditions of the particles that lie around the intended joint plane during high shear displacements. This problem also increases the dilation angle and creates unwanted fractures around the intended joint plane. To solve this problem two new approaches are proposed in this paper: (1) joint plane checking (JPC) approach and (2) joint sides checking (JSC) approach. These approaches and the regular approach are used to model: (a) the direct shear test using the PFC2D and PFC3D, (b) the biaxial test on a sample having a persistent joint with a dip angle varying from 0° to 90° at an interval of 15° using the PFC2D and (c) the polyaxial test on two samples, one of them having a joint with a dip direction of 0° and the dip angle varying from 0° to 90° at an interval of 15°, and the other sample having a joint with a dip angle of 60° and the dip direction varying from 0° to 90° at an interval of 15° using the PFC3D. All numerical results show that the JPC and JSC approaches can solve the interlocking problem. Also, they proved to be more consistent with the theory compared to the regular approach. However, the JPC approach leads to a slightly softer joint. Therefore, the JSC approach is suggested for jointed rock modeling using the PFC. The other shortcoming of the SJCM dealt within this paper is its inability to capture the non-linear behavior of the joint closure varying with the joint normal stress. This problem is solved in this paper by proposing a new modified smooth-joint contact model (MSJCM). MSJCM uses a linear relation between the joint normal stiffness and the normal contact stress to model the non-linear relation between the joint normal deformation and the joint normal stress observed in the compression joint normal stiffness test. A good agreement obtained between the results from the experimental test and the numerical modeling of the compression joint normal test shows the accuracy of this new model. 相似文献
18.
Indirect determination of weighted joint density (wJd) by empirical and fuzzy models: Supren (Eskisehir, Turkey) marbles 总被引：1，自引：0，他引：1
Correct block size assessment is the most important stage for rock quarry management. Although volumetric joint count (Jv) and weighted joint density (wJd) were proposed for this purpose, simple prediction method for these indices is not encountered in literature. Due to the fact that some rock masses such as marbles contain less discontinuity, collection of representative amount of data from in situ line surveys for statistical assessments is highly difficult. For this reason, the main targets of the present paper are to apply photoanalysis approach for collecting additional discontinuity data and to obtain some simple statistical and fuzzy models for predicting weighted joint density to evaluate block size in engineering practice for marbles around Supren (Eskisehir, Turkey). In addition, a new and simple approach to predict volumetric decrease caused by chemical weathering is introduced. For these purposes, extensive field and photoanalysis studies were performed and the data obtained from both field and photoanalysis studies were assessed by regression and fuzzy approaches. The results revealed that the prediction performance of the fuzzy inference system is higher than that of the regression equation. 相似文献
19.
基于三维扫描与打印的岩体自然结构面试样制作方法与剪切试验验证 总被引：1，自引：0，他引：1
无法大量制作表面形态完全一致的含自然结构面的剪切试样一直是困扰岩石结构面力学试验深入研究的难题之一。借助最新发展的3D打印和表面快速扫描技术,提出了岩石自然结构面试样制作新方法。该方法采用三维扫描仪获得岩石自然结构面表面形态的高精度点云数据,然后通过逆向工程软件重构自然结构面的表面形态和含自然结构面的虚拟剪切模型,进而通过3D打印技术制作含自然结构面的PLA（绿色环保材料聚乳酸）塑材模具,最后借助PLA结构面模具在制样盒内通过相似材料浇筑成型出剪切试样,从而实现批量制作结构面形貌完全一致的相似材料结构面剪切试样,满足多种组合试样方案下岩石自然结构面的深入分析。采用这一方法针对3种岩石自然结构面进行了批量制作和剪切试验测试表明：（1）浇筑制作成试样的结构面表面高程与原始结构面高程之间的误差分析显示,岩石自然结构面可以高精度地复制到剪切试样中;（2）相同剪切试验条件下多个剪切试样的剪切位移-剪切力曲线的重合度非常高,表明制作的结构面剪切样的一致性好且试验结果离散性小;（3）通过剪切结构面试样在剪切前后的表面形态扫描分析发现,相同试验条件下自然结构面的剪切破坏形态具有非均匀性。 相似文献
20.
Xing Zhang 《Geotechnical and Geological Engineering》1993,11(2):107-124
Summary Based on an extension to a model originally proposed by Zhang (1990), a method for estimating the shear strength of a jointed rock mass containing two joint sets is developed. Compared to the original method in which only a single en-echelon joint set was considered, the new method has the following advantages: (1) it allows a much more realistic joint pattern to be incorporated; (2) the effects of joint connectivity and intersection angle between joint sets on shear strength are included. Use of the new method is demonstrated by application to the calculation of the stability of slopes in jointed rock. The importance of joint connectivity, joint persistence and joint set intersection angle on slope stability, as predicted by the model, is revealed. 相似文献