Spatial modeling of discontinuity intensity from borehole observations at El Teniente mine, Chile

Hekmatnejad, Amin; Emery, Xavier; Brzovic, Andrés; Schachter, Paulina; Vallejos, Javier

doi:10.1016/j.enggeo.2017.07.012

Cited by 22 publications

(4 citation statements)

References 9 publications

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“…Those artificial low and high intensities diverge from the actual intensity, but when they are averaged, they result in P 32 values close to the actual intensity (Table 6). This effect was already discussed by Hekmatnejad et al [21], who found that on a composite scale (interval scale), fluctuations in calculated P 32 are large and there may be a significant deviation between the calculated and the actual value of P 32 . However, on average, the values tend toward the actual P 32.…”

Section: Effect Of Interval Length On the Calculated P 32 From P 10mentioning

confidence: 58%

Discrete Fracture Network (DFN) Analysis to Quantify the Reliability of Borehole-Derived Volumetric Fracture Intensity

Ojeda,

Elmo,

Rogers

et al. 2023

Geosciences

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Volumetric fracture intensity (P32) is a parameter that plays a major role in the mechanical and hydraulic behaviour of rock masses. While methods such as Ground Penetrating Radar (GPR) are available to map the 3D geometrical characteristics of the fractures, the direct measurement of P32 at a resolution compatible with geotechnical applications is not yet possible. As a result, P32 can be estimated from the borehole and surface data using either simulation or analytical solutions. In this paper, we use Discrete Fracture Network (DFN) models to address the problem of estimating P32 using information from boreholes (1D data). When calculating P32 based on Terzaghi Weighting, it is common practice to use drill run lengths and limit the minimum angle between the borehole and the intersected fractures. The analysis presented in this paper indicated that limiting the minimum angle of intersection would result in an underestimation of the calculated P32. Additionally, the size of the interval has a significant impact on the variability of the calculated P32. We propose a methodology to calculate P32 using variable lengths, depending on the angle between the fractures and the borehole. This methodology allows the capture of the spatial variation in intensity and simultaneously avoids artificially increasing or decreasing the intensity sampled along borehole intervals. Additionally, this work has addressed the impact of boundary effects in DFN models and proposes a methodology to mitigate them.

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Section: Effect Of Interval Length On the Calculated P 32 From P 10mentioning

confidence: 58%

Discrete Fracture Network (DFN) Analysis to Quantify the Reliability of Borehole-Derived Volumetric Fracture Intensity

Ojeda,

Elmo,

Rogers

et al. 2023

Geosciences

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“…Esmeralda, Pacifico Superior, and Reservas Norte sectors have samples located in red and light blue rock type units, while Dacita sector samples are from the blue unit. These units were classified in the base of the P32, number (Dershowitz & Herda 1992;Hekmatnejad et al 2017) classification that has been used in El Teniente mine to asses rock mass stability (Brzovic & Villaescusa 2007;Brzovic et al 2015). The calculations of P32 includes the effect of soft veins in the rock mass classification.…”

Section: Measurementmentioning

confidence: 99%

Analysis of drillhole deviation during drawbell construction in block caving

Bustos¹,

Villaescusa²,

Onederra³

2020

MassMin 2020: Proceedings of the Eighth International Conference &Amp; Exhibition on Mass Mining

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In Block Caving drawbells allow for flow of broken rock. The drawbell construction starts with a drawbell design, which is constrained by the extraction layout shape and development drives sizes. The resulting shape of the drawbell is highly influenced by drilling performance, particularly drillhole deviation. This paper presents the results of a comprehensive analysis of drillhole deviation data undertaken from more than 2,000 holes of 76 mm diameter, having an average length of 12 m and drilled in more than 500 ring positions. In terms of drawbell design, the analysis indicates that the holes less affected by drillhole deviation are those with plunge angle ranging between 65° to 90°. Those holes are located near the centre of the drawbell. The holes less inclined show more deviation. They correspond to those forming the edge of the drawbell shape. Therefore, these areas can be exposed to possible blast damage due to confined charges. The analysis also indicated that 59% of the measured points have a drillhole deviation percentage (DD%) greater than 2%, while 2% of the points present a DD% over 10%. An industry standard for drawbell drill deviation along drilled depth was developed as a tool to check the effectiveness of a blast design, in terms of drill patterns that are likely to appear due to drillhole deviation.

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“…Grossmann [13] proposed mathematical calculation method on volumetric intensity. Hekmatnejad et al [14] addressed the problem of predicting the volumetric intensity in space and of quantifying the uncertainty in the true values, using information from observed discontinuities intersecting boreholes. Sanderson and Nixon [15] introduced some simple techniques to characterize the topology of a fracture network, which extended concepts of topological to 3 dimensions.…”

Section: Introductionmentioning

confidence: 99%

A New Approach for Estimating Rock Discontinuity Trace Intensity Based on Rectangular Sampling Windows

Huo

Tang

et al. 2020

Advances in Civil Engineering

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Trace intensity is defined as mean total trace length of discontinuities per unit area, which is an important geometric parameter to describe fracture networks. The probability of each trace appearing in the sampling surface is different since discontinuity orientation has a scatter and is probabilistically distributed, so this factor should be taken into account in trace intensity estimation. This paper presents an approach to estimate the two-dimensional trace intensity by considering unequal appearing probability for discontinuities sampled by rectangular windows. The estimation method requires the number of discontinuities intersecting the window, the appearing probability of discontinuities with both ends observed, one end observed, and both ends censored, and the mean trace length of discontinuities intersecting the window. The new estimator is validated by using discontinuity data from an outcrop in Wenchuan area in China. Similarly, circular windows are used along with Mauldon’s equation to calculate trace intensity using discontinuity trace data of the same outcrop as a contrast. Results indicate that the proposed new method based on rectangular windows shows close accuracy and less variability than that of the method based on circular windows due to the influence of finite sample size and the variability of location of the window and has advantage in application to sampling surfaces longer in one direction than in the other such as tunnel cross sections and curved sampling surfaces such as outcrops that show some curvature.

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Spatial modeling of discontinuity intensity from borehole observations at El Teniente mine, Chile

Cited by 22 publications

References 9 publications

Discrete Fracture Network (DFN) Analysis to Quantify the Reliability of Borehole-Derived Volumetric Fracture Intensity

Discrete Fracture Network (DFN) Analysis to Quantify the Reliability of Borehole-Derived Volumetric Fracture Intensity

Analysis of drillhole deviation during drawbell construction in block caving

A New Approach for Estimating Rock Discontinuity Trace Intensity Based on Rectangular Sampling Windows

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