scholarly journals A dual fracture model to simulate large-scale flow through fractured rocks

2002 ◽  
Vol 39 (6) ◽  
pp. 1302-1312 ◽  
Author(s):  
E Z Wang ◽  
Z Q Yue ◽  
L G Tham ◽  
Y Tsui ◽  
H T Wang
Keyword(s):  
Groundwater Flow ◽  
Large Scale ◽  
Fractured Rock ◽  
Network Models ◽  
Total Porosity ◽  
Seepage Flow ◽  
Fracture Network ◽  
Fracture Model ◽  
Rock Masses ◽  
Rock Matrix

Discrete fracture network models can be used to study groundwater flow in fractured rock masses. However, one may find that it is not easy to apply such models to practical projects as it is difficult to investigate every fracture and measure its hydraulic parameters. To overcome such difficulties, a dual fracture model is proposed. Taking into account the hydraulic characteristics of the various elements of the fracture system, a hydrogeological medium is assumed to consist of two components: the dominant fracture network and the fractured rock matrix. As the dominant fracture network consists of large fractures and faults, it controls the groundwater flow in rock masses. Depending on the permeabilities of the in-fill materials, these fractures and faults may serve as channels or barriers of the flow. The fractured rock matrix, which includes rock blocks and numerous small fractures, plays a secondary role in groundwater flow in such medium. Although the small fractures and rock blocks possess low permeability, their numbers and their total porosity are relatively large. Therefore, they provide large volume for groundwater storage. In this paper, the application of the proposed model to simulate the groundwater flow for a hydropower station before and after reservoir storage is reported. The implications of the results on the design of the station are also highlighted.Key words: seepage flow, dual fracture model, dominant fracture, fractured rock matrix, case studies, rock-filled dam.

Parallel Computing for Analysis on Intersections between Fractures in Rock Masses

2014 ◽  
Vol 955-959 ◽  
pp. 3001-3005
Author(s):  
Zhi Yu Li ◽  
Ming Yu Wang ◽  
Jian Hui Zhao
Keyword(s):  
Parallel Computing ◽  
Large Scale ◽  
Numerical Study ◽  
Fractured Rock ◽  
Fracture Network ◽  
Mine Safety ◽  
Main Concern ◽  
Rock Masses ◽  
Geothermal Resources ◽  
Intersection Analysis

Fractures dominate the path for fluid flow in fractured rock masses, which is a main concern in groundwater protection, coal mine safety and energy exploitation, e.g., petroleum and geothermal resources. Intersection analysis is one crucial procedure for discrete fracture network modeling as it can provide necessary information for evaluating the connectivity of fractures. This paper is proposed to improve the performance of intersection analysis by means of parallel computing. The algorithm is designed in view of both the computational efficiency and the smooth connection with other procedures in modeling. Numerical study indicates that the proposed parallel algorithm is practical and can significantly reduce the calculation time of intersection analysis under large scale simulations.

Analysis of Coupled Three-Dimensional Seepage and Temperature Fields in Fracture Network of Rock Mass

2019 ◽  
Vol 17 (04) ◽  
pp. 1950005 ◽  
Author(s):  
Zengguang Xu ◽  
Yang Liu ◽  
Yaping Wang ◽  
Junrui Chai ◽  
Yanlong Li
Keyword(s):  
Rock Mass ◽  
Coupling Effect ◽  
Fractured Rock ◽  
Seepage Flow ◽  
Fracture Network ◽  
Temperature Fields ◽  
Fractured Rock Mass ◽  
Flow Temperature ◽  
Geothermal Resources ◽  
Mass Temperature

The coupling effect of seepage and temperature fields in fractured rock mass is a hot topic in the area of water conservancy, nuclear waste disposal and geothermal resources development. A coupling mathematical model of the seepage, flow temperature and rock mass temperature fields in the fracture network of rock mass is established based on the seepage and temperature interaction. A calculation program is developed and applied to calculate the seepage and temperature fields of the dam foundation of a water conservancy project. The interaction mechanism of the seepage, flow temperature and rock mass temperature fields is analyzed in this paper. Results show that the seepage field largely influences the temperature field, which can provide several suggestions for the deep underground disposal of nuclear waste, geothermal resources development and fractured rock mass in dam foundations. Considering the coupling effect of the seepage, flow temperature and rock mass temperature fields by the fracture network method is necessary.

A New Method to Determining the Strength Parameters of Fractured Rock Mass

2014 ◽  
Vol 898 ◽  
pp. 378-382
Author(s):  
Yun Hua Guo ◽  
Wei Shen Zhu
Keyword(s):  
Rock Mass ◽  
Mechanical Response ◽  
Fractured Rock ◽  
Fracture Network ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Constitutive Relationship ◽  
Hydropower Station ◽  
Rock Masses ◽  
Fractured Rock Mass

A Hydropower Station is located in the middle reach of the Dadu River in southwest China. The natural slope angles are generally 40°~65° and the relative elevation drop is more than 600m. Complex different fractures such as faults, dykes and dense fracture zones due to unloading are developed. Many abutment slopes were formed during construction of the abutments. The stability of these steep and high slopes during construction and operation period plays an important role for the safe construction and operation of the hydropower station. According to the statistical distribution of joints and fractures at the construction site, the slope is divided into a number of engineering geological zones. For each zone, a stochastic fracture network and a numerical model which is close to the real state of the fractured rock mass are established by the Monte-Carlo method. The mechanical response of fractured rock masses with different sizes of numerical models is studied using FLAC3D. The REV characteristic scale is identified for rock masses in the slopes with stochastic fracture network. Numerical simulation is performed to obtain the stress-strain curve, the mechanical parameters and the strength of the jointed rock mass in the zone. A constitutive relationship reflecting the mechanical response of the jointed rock mass in the zone is established. The Comparison between the traditional method and the method in this paper has been made at the end.

Interpretation of a Network-Scale Tracer Experiment in Fractured Rock

2020 ◽  
Author(s):  
Matthew Howroyd ◽  
Kent Novakowski
Keyword(s):  
Large Scale ◽  
Control Volume ◽  
Fractured Rock ◽  
Element Model ◽  
Fracture Network ◽  
Tracer Experiment ◽  
Transport Processes ◽  
Depth Range ◽  
Network Scale ◽  
Observation Wells

<p>The presence of fractures in consolidated media allows for rapid transport of aqueous contaminants through convoluted pathways and for diffusion into the rock matrix adjacent to the fracture, which significantly complicates our ability to make transport predictions. Despite the need to predict transport in fractures over substantive distances, very few tracer experiments have been conducted at large scale (>50m) due to experimental difficulty and cost associated with such experiments.  Even where these studies have been conducted, the results have often been difficult to model accurately without the use of extra fitting parameters. The objective of this study is to improve our understanding of key transport processes in complex large-scale fracture networks in carbonate rock by simulating the results of a tracer experiment conducted at a network scale. The tracer experiment used for this study was conducted previously by injecting a conservative dye tracer into an isolated 10 m section of a well and with breakthrough in six downstream observation wells open over a similar depth range. These observation points were located at distances of up to 245 m from the injection well. Measurement of the tracer breakthrough was conducted using a downhole fluorometer, allowing for observation of the full concentration profile in each well over time. To simulate the results, a DFN approach with a control-volume finite element model is used, which allows for irregular grid blocks and maintenance of the mass balance within the simulation domain. Because of the measurement of full concentration profiles, simulating transport inside the observation wells is also a focus of this study. In order to achieve a fit between the simulated and measured data, combinations of various fracture network geometries with aperture and matrix porosity heterogeneity are examined.</p>

scholarly journals Correlations between Geometric Properties and Permeability of 2D Fracture Networks

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Xiaolin Wang ◽  
Liyuan Yu ◽  
Hanqing Yang
Keyword(s):  
Fractured Rock ◽  
Rock Fracture ◽  
Fractal Dimensions ◽  
Fracture Network ◽  
Network Structures ◽  
Rock Masses ◽  
Fracture Networks ◽  
Geometric Properties ◽  
Equivalent Permeability ◽  
Fractured Rock Masses

The equivalent permeability of fractured rock masses plays an important role in understanding the fluid flow and solute transport properties in underground engineering, yet the effective predictive models have not been proposed. This study established mathematical expressions to link permeability of 2D fracture networks to the geometric properties of fractured rock masses, including number density of fracture lines, total length of fractures per square meter, and fractal dimensions of fracture network structures and intersections. The results show that the equivalent permeability has power law relationships with the geometric properties of fracture networks. The fractal dimensions that can be easily obtained from an engineering site can be used to predict the permeability of a rock fracture network. When the fractal dimensions of fracture network structures and intersections exceed the critical values, the effect of randomness of fracture locations is negligible. The equivalent permeability of a fracture network increases with the increment of fracture density and/or fractal dimensions proportionally.

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