共查询到20条相似文献，搜索用时 531 毫秒
1.
《Journal of Structural Geology》2001,23(2-3):247-258
We introduce new estimators for fracture trace intensity, trace density and mean trace length that exploit the use of circles as efficient sampling tools. A fracture trace is the commonly observed surface expression of a fracture, i.e. the intersection of a fracture with an exposed surface such as a rock pavement or a mine drive wall. Trace intensity, trace density and mean trace length estimators are derived and shown to form a self-consistent set of two-dimensional fracture abundance measures. The intensity estimator n/4r uses the number, n, of intersections between fracture traces and a circular scanline of radius r. The density estimator m/2πr2 uses the number, m, of trace endpoints inside a circular window. The mean trace length estimator (n/m)πr/2 uses the ratio of the number of trace intersections on the circle to the number of endpoints in the circle.The circular sampling tools and estimators described here eliminate most sampling biases due to orientation and also correct many errors due to censoring and length bias that plague established scanline and areal measurement techniques. Performance of the estimators is demonstrated by comparison with areal samples of a synthetic fracture trace population with known intensity, density and mean trace length. The estimators are also applied successfully to a natural rock pavement with two orthogonal fracture sets, one of which is severely censored. Because the new circle-based estimators only require counts of trace–circle intersections and/or trace endpoints, they are more time-efficient than current methods for estimating geometric characteristics of fracture traces. 相似文献
2.
The equations that exist in the literature to estimate corrected mean trace length and corrected two-dimensional density of a rock discontinuity set using area sampling technique are critically reviewed. The discontinuity traces appearing in an outcrop in Yingxiu area in China are used along with rectangular windows to calculate the corrected mean trace length and two-dimensional density using Kulatilake and Wu’s equations. Similarly, circular windows are used along with Mauldon’s and Zhang and Einstein’s equation to calculate the mean trace length and Mauldon’s equation to calculate the two-dimensional density for the same discontinuity sets using the same outcrop discontinuity trace data. For both parameters, the predictions based on the rectangular window methods were found to be more accurate than that based on the circular window methods. 相似文献
3.
Estimating the Mean Trace Length of Rock Discontinuities 总被引：24，自引：1，他引：23
Summary Rock discontinuities appear as traces on exposures such as natural outcrops or tunnel walls. Discontinuity size which has
important effects on rock mass behavior is related to trace length.
This paper presents a technique for estimating mean trace length from the observations made on finite, circular sampling
windows. The method takes sampling errors into account and it requires, like existing methods using rectangular sampling windows,
that the numbers of discontinuities with both ends censored, with one end observed and one end censored, and with both ends
observed be known. Knowledge of the lengths of the observed traces and the distribution of trace lengths is not required.
A major advantage of the proposed method over the existing methods is that it does not need sampling data about the orientation
of discontinuities, i.e. the proposed method is applicable to traces with arbitrary orientation distributions.
To check the validity of the proposed method, theoretical relations between the mean trace length and the mean diameter of
circular discontinuities, respectively for lognormal and negative exponential distributions of the diameter of discontinuities,
are derived. The proposed method is then applied to analyze data simulated with the FracMan code, and the predicted results
are compared to the corresponding theoretical solutions. The results show that the proposed method is satisfactory. Comparisons
of the predicted mean trace length with the mean of observed trace lengths show that it is important to consider sampling
biases when estimating mean trace length. 相似文献
4.
J.-J. Song 《Rock Mechanics and Rock Engineering》2006,39(2):131-146
Summary. Mauldon (1998) suggested end-point estimators of areal frequency and mean trace length for a planar sampling window which
were recently proved to be unbiased maximum likelihood estimators by Lyman (2003). The present paper is to expand the concept
and applicability of the end-point estimators to those for a general non-planar sampling window. The generalized end-point
estimators are verified and its applicability for variable discontinuity orientation is checked by Monte Carlo simulation.
Standard deviation of estimation error and estimation efficiency of areal frequency and mean trace length are also considered. 相似文献
5.
节理迹线中点密度是描述岩体露头节理分布特征的重要指标。由于露头或测窗尺寸的限制、节理迹长的差异以及露头面和节理面夹角的变化,常规的迹线中点密度计算方法通常包含尺寸、截长和角度误差。本文首先介绍了截长、尺寸和角度误差的修正原理,继而将角度误差修正系数引入到关联点密度计算方法中,提出了凸面测窗条件下同时修正截长、尺寸和角度误差的迹线中点密度计算方法。利用三维节理网络建模技术,模拟生成不同方位、不同大小和不同形状的测窗,系统分析了尺寸、截长和角度误差对迹线中点密度的影响,验证了新方法的有效性。最后,针对我国高放废物地质处置北山坑探设施的硐口岩体露头,实现了节理迹线中点密度分析。上述算例和应用表明,新方法可以有效地修正截长、尺寸和角度误差,可以为估算岩体节理分布密度提供更为可靠的依据。 相似文献
6.
Estimation of mean trace length of discontinuities 总被引：18，自引：0，他引：18
Summary Trace lengths of discontinuities observed on finite exposures are biased due to sampling errors. These errors should be corrected in estimating mean trace length. A technique, which takes into account the sampling errors, is proposed for estimating the mean trace length on infinite, vertical sections from the observations made on finite, rectangular, vertical exposures. The method is applicable to discontinuities whose orientation is described by a probability distribution function. The method requires that the numbers of discontinuities with both ends observed, one end observed, and both ends censored be known. The lengths of observed traces and the density function of trace length are not required. The derivation assumes that midpoints of traces are uniformly distributed in the vertical plane. Also independence between trace length and orientation is assumed. Data on a Pennsylvania shale in Ohio, U. S. A., were used as an example.Notations
dip direction
-
direction of sampling plane
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acute angle between dip direction and sampling plane
-
dip angle
-
A
apparent dip angle
-
mean density of trace mid-points per unit area
-
mean trace length
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D
diameter of discontinuity
-
f (.),g (.)
probability density function
-
h
height of rectangular window
-
estimator of mean trace length
-
m
sample size, number of discontinuities intersecting window
-
m
0
number of discontinuities intersecting window with both ends censored
-
m
2
number of discontinuities intersecting window with both ends observed
-
n, N
expected number of discontinuities intersecting the window
-
n
0,N
0
expected number of discontinuities intersecting the window with both ends censored
-
n
2,N
2
expected number of discontinuities intersecting the window with both ends observed
-
Pr (.)
probability
-
w
width of rectangular window
-
x
trace length 相似文献
7.
Fracture Length Estimation from Borehole Image Logs 总被引：1，自引：0，他引：1
Sait Ismail Özkaya 《Mathematical Geology》2003,35(6):737-753
We describe a method to estimate fracture length for circular fractures from borehole image logs. The relative frequency of fractures, which have complete circumference trace on image logs is related to fracture length. A simple functional relationship can be derived for the relative frequency of complete fracture traces in terms of average fracture inclination to borehole, borehole diameter and fracture length. This formulation however, tends to underestimate fracture length because a constant length is assumed. A more accurate length estimate can be obtained by assuming that fracture length is linearly correlated to fracture aperture or spacing. Cumulative frequency distribution of fracture aperture and spacing can be obtained from borehole image logs. The problem then transforms itself to finding the scaling factor between fracture length and aperture (or spacing) from the relative frequency of fractures with complete traces. The product of the scaling factor and average fracture spacing (or aperture) gives the average fracture length. 相似文献
8.
从不连续面与窗口交切的充要条件出发,推导了窗口法不连续面剖面测量的平均迹长估算公式,实例分析表明用雇在算的平均迹长与实测平均迹长吻合较好。 相似文献
9.
不连续面平均速长概率估值法及其应用 总被引：4，自引：1，他引：4
在进行不连续面3-D网络模拟过程中, 不连续面的大小是一个重要的参数, 该数据主要来源是在现场露头上测量不连续面出露的迹长。由于取样中不可避免的偏差而使结果有误差, 在进行平均迹长估计时取样的误差必须予以校正, 本文介绍一种用概率的方法考虑取样误差通过有限2-D露头上测量的不连续面数据求算无限2-D空间平均迹长的技术。该方法可以借助计算机进行处理。 相似文献
10.
11.
WEI Xiang GUO Ying CHENG Hanlie MENG Xiangdong CHENG Mingqian YANG Ting XU Chunmei 《《地质学报》英文版》2019,93(2):362-372
Geological and hydrological characteristics, joint geometric features, rock physical and mechanical properties and rock mass quality are studied in the Beishan area, preselected for China’s high-level radioactive waste (HLW) disposal engineering. A comprehensive survey method is developed to study joint geometric features in the outcrop and samples from borehole BS06 into the Xinchang rock mass were tested. The optimal joint sets are determined by rose diagrams and equal-area lower hemisphere plots of joint poles. Results show that: 1) the distribution of joint occurrence obeys a normal distribution, while the distribution of joint spacing obeys a negative exponential distribution; 2) concentric circular and tangent circular sampling windows are applied to study the trace length and the trace midpoint density. Results indicate that tangent circular sampling window is more stable and reasonable; 3) Beishan granite shows high density, low porosity and high strength based on many laboratory tests and the physical properties and mechanical properties are closely related; and 4) a synthesis index, Joint Structure Rating (JSR), is applied to evaluate the quality of rock mass. Through the research results of rock mass characteristics, the Xinchang rock mass in the Beishan preselected area has the favorable conditions for China’s HLW disposal repository site. 相似文献
12.
The Planar Shape of Rock Joints 总被引：1，自引：1，他引：0
Knowing the planar shape of discontinuities is important when characterizing discontinuities in a rock mass. However, the
real discontinuity shape is rarely known, since the rock mass is usually inaccessible in three dimensions. Information on
discontinuity shape is limited and often open to more than one interpretation. This paper discusses the planar shape of rock
joints, the most common discontinuities in rock. First, a brief literature review about the shape of joints is presented,
including some information on joint-surface morphology, inferences from observed trace lengths on different sampling planes,
information based on experimental studies, and joint shapes assumed by different researchers. This review shows that joints
not affected by adjacent geological structures such as bedding boundaries or pre-existing fractures tend to be elliptical
(or approximately circular but rarely). Joints affected by or intersecting such geological structures tend to be rectangular.
Then, using the general stereological relationship between trace length distributions and joint size distributions developed
by Zhang et al. (Geotechnique 52(6):419–433, 2002) for elliptical joints, the effect of sampling plane orientation on trace lengths is investigated. This study explains why
the average trace lengths of non-equidimensional (elliptical or similar polygonal) joints on two sampling planes can be about
equal and thus the conclusion that rock joints are equidimensional (circular) drawn from the fact that the average trace lengths
on two sampling planes are approximately equal can be wrong. Finally, methods for characterizing the shape and size of joints
(elliptical or rectangular) from trace length data are recommended, and the appropriateness of using elliptical joint shapes
to represent polygonal, especially rectangular, joints is discussed. 相似文献
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15.
RobertD.JACOBI 《《地质学报》英文版》2003,77(4):491-503
2-D and 3-D densities of fractures are commonly used in mining safety design, natural gas and oil production in fractured reservoirs, and the characterization of subsurface flow and transportation systems in fractured rocks. However, many field data sets are collected in 1-D frequency (f) (e.g., scanlines and borehole data). We have developed an ARC/ INFO-based technology to calculate fracture frequency and densities for a given fracture network. A series of numerical simulations are performed in order to determine the optimal orientation of a scanline, along which the maximum fracture frequency of a fracture network can be obtained. We calculated the frequency (f) and densities (both D1 and D2) of 36 natural fracture trace maps, and investigated the statistical relationship between fracture frequency and fracture density D1, i.e. D1=1.340f+ 0.034. We derived analytical solutions for converting dimensional density (D1) to non-dimensional densities (D2 and D3) assuming that fracture length distribution f 相似文献
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17.
靶窗的确定对海相页岩气储层增产改造具有重要意义。以川南长宁地区龙马溪组海相页岩气储层为研究对象,开展氩离子抛光扫描电镜、巴西圆盘实验和压裂施工统计,分析矿物颗粒粒径和断裂韧性、地应力对裂缝在水力压裂时能否快速穿透、稳定扩展、充分转向等方面的影响。针对现有方法未充分考虑储层压裂品质的情况,简化计算流程,分别采用声波、密度、伽马和矿物含量等建立脆延性指标,采用优化后的应力与应力差耦合模型建立应力差异指标,形成基于储层缝网可压性理论、根据测井解释曲线形态判别的靶窗预测方法。研究结果表明,脆延性指标和应力差异指标曲线呈现叠合度较高的Ⅰ类双"波谷"的层位最有利于开发,其次为Ⅱ类连续交错叠置的层位,最后为Ⅲ类不连续交错的层位。对长宁地区评价井、建产井的验证与实践表明,靶窗对应的指标多呈现双"波谷"形态,但靶窗对应的层位具有差异,区内自西向东靶窗呈现1小层—2小层—1小层的演化趋势。实现不同井区差异化靶窗的高钻遇率对单井获得较大储层改造规模、较高的测试产量和稳定的累计产量具有重要的控制作用。 相似文献
18.
结构面平均迹长估算的Laslett算法和广义H-H算法虽然在理论上具有严密的推导过程,但实际应用时,由于迹长层次不同,两种算法估值精度不同。在利用开挖边坡所揭露的全迹长资料对不同迹长层次下两种算法的估值精度进行检验的基础上,讨论了两种算法的适用性,并针对工程中所采用的测量窗口高度通常较小这一实际情况,对广义H-H算法在小窗口长迹长层次下的迹长估计值进行适当修正。综合研究结果,建议:(1)小窗口短小迹长层次情况下采用Laslett算法进行迹长估计; (2)小窗口长大迹长层次情况下采用乘以修正系数x=2的广义H-H算法。 相似文献
19.
以重庆梁-忠（梁平县-忠县）高速公路礼让隧道为工程研究背景,通过测线法调查现场节理,获得了节理产状分布概率密度函数,并从分形几何学的角度分析了节理间距及迹长的分形分布规律,推导出能反映节理间距及迹长分布状态的分形维数D及分形分布概率密度函数。在该基础上采用Matlab软件以及Monte-Carlo随机分析方法,产生节理参数随机数,结合3DEC中最新模块离散裂隙网络(DFN)技术,建立了能反映节理裂隙分布特征的离散裂隙网络模型并验证了模型的有效性,结果表明,分形分布比负指数分布包含更多的间距、迹长分布信息,更接近于实际分布;分形维数D反映了节理间距、迹长在其变化范围内的分布特征,分形维数的大小取决于小间距、小迹长部分数量在总节理数量中的比例,为节理裂隙岩体网络模型构建提供了一种新方法。 相似文献
20.
Based on the fracture trace length distribution, conditions for the existence, uniqueness, and correctness of the fracture diameter distribution are given using Warburton’s fracture model. In particular, a solution for the fracture diameter distribution exists and is unique for all trace length probability density functions, h A (y), such that \(h_{A}(y)/\sqrt{y^{2}-x^{2}}\) is Lebesgue integrable on [x,∞). This condition is met by the uniform, exponential, gamma, lognormal, and power-law trace length distributions as well as by the trace length distributions that arise from a deterministic fracture diameter or from a discontinuous fracture diameter length distribution. Exponential, gamma, lognormal, and power-law trace length distributions satisfy necessary conditions for the diameter distribution to be non-negative, and necessary and sufficient conditions for the distribution to have unit integral over the real line. Negative values of the fracture diameter distribution arise when the trace has a uniform distribution and the lower bound of the fracture trace is greater than zero. 相似文献