A cluster-based multiparametric similarity test for the compartmentalization of crystalline rocks into structural domains

Usually, fracture sampling studies comprise the collection of several fracture samples, which involve many fracture clusters. Grouping fracture samples into structural domains is generally useful for geologists, hydrogeologists, and geomechanicians as a region of fractured rocks is subdivided into sub-regions with similar behavior in terms of their hydromechanical properties. One of the common methods used for grouping fracture samples into structural domains considers the fracture orientation of clusters and ignores several fracture parameters, such as fracture spacing, aperture, and persistence, which are important for fluid circulation in the rock mass.In this study, we proposed a new cluster-based similarity method that considered the orientation of clusters as well as clusters’ aperture, persistence, and fracture spacing. Field investigations were conducted in the Grenville geological province of the Canadian Shield in the Lanaudière region, Quebec, Canada, where fractures were sampled from 30 outcrops and four boreholes. The proposed method is more suitable than other methods, and has applications in hydrogeology, rock mechanics, and especially in studies of fluid circulation in the rock mass. In addition, a method for the compartmentalization of a given study area into structural domains by means of Voronoi diagrams was also proposed.

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A similarity test for the compartementalization of crystalline rocks into structural domains

10.5194/egusphere-egu21-9979 ◽

2021 ◽

Author(s):

Attoumane Abi ◽

Julien Walter ◽

Ali Saeidi ◽

Romain Chesnaux

Keyword(s):

Rock Mass ◽

New Method ◽

Structural Domain ◽

Structural Elements ◽

Fluid Circulation ◽

Structural Domains ◽

Fracture Characterization ◽

Fracture Characteristics ◽

Fracture Spacing ◽

Field Investigations

It is well known that fracture networks play an important role in fluid circulation in crystalline rock mass. Given that crystalline basements have a negligible primary porosity (porosity of the rock matrix) in comparison to their secondary porosity (porosity due to fractures), fracture characterization generally constitute the most important parameter for the determination of the hydraulic characteristics of the rock mass. Fracture characterization may involve fracture samples from different surveying sources such as outcrops, tunnels and boreholes. For a matter of building a conceptual model, for a study area, the geologist compartmentalizes the study area into several structural homogeneous sub-areas. Those homogeneous sub-areas are called structural domains and how fracture samples are grouped in the same structural domain is the question treated in this presentation.From field investigations to grouping fracture samples into structural domains, geologists have used methods that are mainly based on the geologist experience and use major structural elements such as faults as domain boundaries. In the case of total absence or limited presence of major structural elements, grouping fracture samples into structural domains becomes complicated. Therefore, several statistical methods which use fracture characteristics have been developed to assist the geologist for that matter. Those methods can be classified into two approaches, which have been introduced by Miller (1983) and Mahtab and Yegulalp (1984). Miller&#8217;s approach consists of grouping fracture samples which are totally homogeneous with regard to the fracture characteristic(s) of interest, especially fracture orientation. On the other hand, Mahtab and Yegulalp&#8217;s approach consists of grouping fracture samples which share a similar fracture set. While, Miller&#8217;s approach got a lot attention, especially in the engineering fields, Mahtab and Yegulalp&#8217;s method has the advantage of allowing taking into consideration the blind zones of fracture samples as in practice a fracture sample can hardly be constituted by all the fracture sets of its belonging structural domain. However, Mahtab and Yegulalps&#8217;s method ignore fracture characteristics such as fracture spacing, aperture and persistence which are important for fluid circulation in the rock mass.This presentation proposes a new method that improves Mahtab and Yegulalp&#8217;s method by including fracture characteristics such as aperture, persistence and fracture spacing in addition to the fracture orientation considered in the original method. The field investigations took place in the Greenville geological province of the Canadian shield, in Lanaudi&#232;re region, in Quebec; where fractures were sampled from 30 outcrops and four boreholes. The new method adds a higher level of confidence with regard to the similarity of samples within a structural domain. As a result of the new method, each structural domain has a unique combination of fracture set(s) characteristics which characterize its fracture network. The structural domain compartmentalization impact on the hydrogeological behavior of water flow within the rock mass constitutes the topic of an ongoing research project.

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A NEW SQUASH BUG

The Canadian Entomologist ◽

10.4039/ent30239-9 ◽

1898 ◽

Vol 30 (9) ◽

pp. 239-240

Author(s):

F. H. Chittenden

Keyword(s):

District Of Columbia ◽

Department Of Agriculture ◽

Anasa Tristis ◽

Squash Bug ◽

Field Investigations ◽

The Common ◽

College Station ◽

Official Work

In the course of an investigation of insects affecting cucurbits, begun in a preliminary way in the season of 1897, as a part of the official work of the Division of Entomology of the Department of Agriculture, it was found that we have in addition to the common squash bug, Anasa tristis, DeG., a second species sufficiently resembling it as to have readily escaped the notice of the average observer, but at the same time quite distinct in all its stages. This species is Anasa armigera, Say, and it was first observed on cucurbits by the writer July 12, near colonial Beach, Va., where it occured on cucumbers. Afterward it was taken by the writer and Mr. F. C. Pratt, of the Division of Entomology, who has assisted in field investigations and collections on different cucurbits, at Ballston, Va., Poolesville and Seat pleasant, Md., and on the Conduit Road and at Tenleytown, D. C. At the last mentioned place it occured in great abudance on a late crop of cucumbers and watermelons. As late as the 29th of September, all stages of the insect were found, including the egg. The present year the species was found to be nearly as abundant in some locaties as the common squash bug. Such was the case at Marshall Hall, Md., and in one locality in the District of columbia. It was also observed on squash at College Station and Kensington, Md., and on cucumber at Cabin John, Md.

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Study on Dynamic Disaster in Steeply Deep Rock Mass Condition in Urumchi Coalfield

Shock and Vibration ◽

10.1155/2015/465017 ◽

2015 ◽

Vol 2015 ◽

pp. 1-8 ◽

Cited By ~ 5

Author(s):

Xing-Ping Lai ◽

Mei-Feng Cai ◽

Fen-Hua Ren ◽

Peng-Fei Shan ◽

Feng Cui ◽

...

Keyword(s):

Rock Mass ◽

Economic Benefit ◽

Rotation Effect ◽

Deep Mining ◽

Mining Seismicity ◽

Monitoring Technique ◽

Field Investigations ◽

Deep Rock ◽

Rock Mass Condition ◽

Roof Strata

The possible mining seismicity (MS) and its prediction are important for safety and recovery optimization of mining in steep-heavy-thick rock mass condition. The stress-lever-rotation-effect (SLRE) model of fault-like mobilization was proposed preliminarily. Some innovation monitoring technique approaches for mining seismicity assessment were successfully fulfilled at Wudong Mine of Urumchi Coalfield, China. The characteristics on acoustic-seismic-wave index indicated the spatial-temporal-strength and stress redistribution of steeply deeper-heavy thick coal and rock masses. Applications in field investigations showed that the innovation monitoring (in time and space) of these instruments could provide important information about the performance of mining disturbed structures (heading and steep pillar) during caving of competent overlying roof strata. The prediction and evaluation for mining seismicity were applicable and valid. Operating practice showed that mining efficiency was raised and conspicuous economic benefit was obtained. This approach provides essential data for assessing mining seismicity, coal burst, dynamic hazard prevention, and deep mining potential.

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Determining the REV for Fracture Rock Mass Based on Seepage Theory

Geofluids ◽

10.1155/2017/4129240 ◽

2017 ◽

Vol 2017 ◽

pp. 1-8 ◽

Cited By ~ 1

Author(s):

Lili Zhang ◽

Lu Xia ◽

Qingchun Yu

Keyword(s):

Rock Mass ◽

Fractured Rock ◽

Engineering Application ◽

Existence Condition ◽

Analysis Tool ◽

Fractured Rock Mass ◽

Rock Classification ◽

Fracture Spacing ◽

Fractured Rock Masses

Seepage problems of the fractured rock mass have always been a heated topic within hydrogeology and engineering geology. The equivalent porous medium model method is the main method in the study of the seepage of the fractured rock mass and its engineering application. The key to the method is to determine a representative elementary volume (REV). The FractureToKarst software, that is, discrete element software, is a main analysis tool in this paper and developed by a number of authors. According to the standard of rock classification established by ISRM, this paper aims to discuss the existence and the size of REV of fractured rock masses with medium tractility and provide a general method to determine the existence of REV. It can be gleaned from the study that the existence condition of fractured rock mass with medium tractility features average fracture spacing smaller than 0.6 m. If average fracture spacing is larger than 0.6 m, there is no existence of REV. The rationality of the model is verified by a case study. The present research provides a method for the simulation of seepage field in fissured rocks.

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Modelling the variation in the behaviour of pre-fractured rocks subjected to hydraulic fracturing with permeability of the rock matrix using finite-discrete element method

E3S Web of Conferences ◽

10.1051/e3sconf/202020508001 ◽

2020 ◽

Vol 205 ◽

pp. 08001

Author(s):

Shahrzad Roshankhah ◽

Arman K. Nejad ◽

Orlando Teran ◽

Kami Mohammadi

Keyword(s):

Rock Mass ◽

Finite Elements ◽

Hydraulic Fracturing ◽

Discrete Element Method ◽

Fractured Rocks ◽

Discrete Element ◽

Fracture Network ◽

Rock Matrix ◽

Flow Through ◽

Element Method

In this study, we present the results of two-dimensional numerical simulations for the effects of rock matrix permeability on the behaviour of hydraulic fractures in intact and pre-fractured rocks. The simulations are performed using the Finite-Discrete Element Method (FDEM). In this method, the deformation and fluid pressure fields within the porous rock blocks, pre-existing fracture network, and hydraulically induced fractures are calculated through a fully coupled hydromechanical scheme. Furthermore, new fractures can initiate in crack elements located between each pair of finite elements and can propagate in any path that the boundary and loading conditions require according to non-linear fracture mechanics criteria. Fluid channels are also defined between pairs of finite elements simulating the inter-connected flow paths through porous media. Four models of the rock mass are created in this study: (i) homogeneous-impermeable, (ii) homogeneous-permeable, (iii) heterogeneous-impermeable matrix, and (iv) heterogeneous-permeable matrix. Heterogeneous rock masses contain a discrete fracture network (natural fractures) in the rock mass structure. Hydraulic fracturing is modelled in domains of 40×40 m2 with the four different structures and mass transport capacities, and the results are compared to each other. The results highlight the significant effect of diffusive fluid flow through rock blocks, in addition to the flow through fracture network, on the global hydromechanical behaviour of the rock mass. These results help to understand the governing hydromechanical processes taking place in fractured rocks with matrix of different permeability, such as granites, shales, carbonate rocks, and sandstones and the extent of complexities required to model their behaviour to achieve reasonable accuracy.

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Fuzzy Rock Mass Rating

Advances in Civil and Industrial Engineering - Handbook of Research on Trends and Digital Advances in Engineering Geology ◽

10.4018/978-1-5225-2709-1.ch003 ◽

2018 ◽

pp. 97-131

Author(s):

Ahmet Gunes Yardimci ◽

Celal Karpuz

Keyword(s):

Rock Mass ◽

Slope Angle ◽

Short Review ◽

Classification Systems ◽

Rock Slopes ◽

Weak Rocks ◽

Mass Properties ◽

Mass Classification ◽

The Common ◽

Graphical Presentation

Rock mass classification systems are the most commonly used empirical tools in preliminary design of rock slopes. In spite of numerous advantages, these systems lack the common drawbacks of classification systems originated from uncertainties. These drawbacks may lead to similar or so close quality scores for different rock mass properties. Fuzzy Sets is a rising trend in describing Geomechanical problems by including the expert opinion. Especially in the case of weak rocks it allows prediction of more realistic rock mass quality scores. Although the empirical systems form a basis for the preliminary slope stability investigation, slope height and overall slope angle are still two missing important characteristic slope parameters. However, there have been some attempts to describe the graphical presentation of rock quality score, slope height and overall slope angle relation. These charts are called as slope performance charts. This chapter presents a short review on integration of Fuzzy RMR with these charts to provide a useful modification for the case of weak rock slopes.

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Identification of structural domains considering the size effect of rock mass discontinuities: A case study of an underground excavation in Baihetan Dam, China

Tunnelling and Underground Space Technology ◽

10.1016/j.tust.2015.10.026 ◽

2016 ◽

Vol 51 ◽

pp. 75-83 ◽

Cited By ~ 8

Author(s):

Wen Zhang ◽

Qihua Zhao ◽

Runqiu Huang ◽

Jianping Chen ◽

Yiguo Xue ◽

...

Keyword(s):

Rock Mass ◽

Size Effect ◽

Underground Excavation ◽

Structural Domains

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A Rock Mass Classification Scheme for Estimating Hydraulic Conductivity of Fractured Rocks

GeoCongress 2008 ◽

10.1061/40972(311)57 ◽

2008 ◽

Author(s):

Shih Meng Hsu ◽

Ming Chan Chung ◽

Yu Ku Cheng ◽

Chi Ho Tan ◽

Su Yun Chi

Keyword(s):

Rock Mass ◽

Hydraulic Conductivity ◽

Fractured Rocks ◽

Classification Scheme ◽

Rock Mass Classification ◽

Mass Classification

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PERMEABILITY OF COVER DEPOSITS OF CRYSTALLINE ROCKS IN THE SUDETY MOUNTAINS (SW POLAND) BASED ON A FIELD STUDY

Carpathian Journal of Earth and Environmental Sciences ◽

10.26471/cjees/2021/016/151 ◽

2021 ◽

Vol 16 (1) ◽

pp. 5-15

Author(s):

Tomasz OLICHWER ◽

◽

Katarzyna PIOTROWSKA ◽

Estera TEREŚKIEWICZ

Keyword(s):

Hydraulic Conductivity ◽

Field Measurements ◽

Crystalline Rocks ◽

Igneous Rocks ◽

Metamorphic Rocks ◽

Infiltration Capacity ◽

Field Investigations ◽

Vertical Hydraulic Conductivity ◽

Sudety Mountains ◽

Constant Head

Article presents a study on the permeability of weathering covers formed on crystalline rocks, which was conducted in south-western Poland (Sudety Mountains). Evaluation of the infiltration capacity was performed based on field measurements of the vertical hydraulic conductivity carried out by using the Porschet method and the ETC Pask Constant Head Permeameter. During the field investigations conducted in sixteen sites, 28 determinations of the hydraulic conductivity k were made, 16 by the Porschet method and 12 using the ETC Pask Permeameter. Ten sites represent weathering covers of metamorphic rocks (amphibolites, eclogites, mica-schists, crystalline limestones, gneisses) and the next six sites represent covers of igneous rocks (granites). The values of the vertical hydraulic conductivity k determined by the Porschet method ranged between 0.053 and 2.19 m/d, while those obtained using the ETC Pask Permeamet erranged between 0.012 and 0.76 m/d. In the first place, it should be noticed that the results determined during the field investigations conducted according to the Porschet method are generally 3-4 times higher than those obtained using the ETC Pask Permeameter. The results for the vertical hydraulic conductivity allow us to classify weathering sediments of metamorphic and igneous rocks, as semi-permeable to medium permeable rocks. Weathered gneisses were distinctly characterized by the worst capacity to conduct water (semi-permeable) among all types of weathering covers of crystalline rocks. Higher values (0,08-0,8 m/d) of the vertical hydraulic conductivity were found for the weathering covers of the other metamorphic rocks (low permeable). The best conditions to conduct water were found in the weathering covers of granite rocks, which in most cases are classified as medium permeable rocks (more than 0.8 m/d) and exhibit distinctly better permeability coefficients.

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