The Modification and Application of the Geochemical Modelling Code CHEQMATE to Simulate Transport and Chemical Processes within Fractured Media

1993 ◽  
Vol 333 ◽  
Author(s):  
A. V. Chambers ◽  
A.C. Smith
Keyword(s):  
Fractured Rock ◽  
Chemical Processes ◽  
Fractured Media ◽  
Single Fracture ◽  
Radionuclide Transport ◽  
Continuum Approach ◽  
Multiple Fractures ◽  
Intermediate Level Radioactive Waste ◽  
The Uk ◽  
Fracture Distribution

ABSTRACTThe UK current plans for a repository for the disposal of intermediate-level radioactive waste involve the use of a cementitious backfill within the repository vaults. Radionuclide transport could be concentrated within cracks that may form in the cement, or in fractures within the rock surrounding the repository. A version of CHEQMATE (CHemical EQuilibrium with Migration And Transport Equations) that includes a representation of transport through fractured media has been developed. This paper describes modifications of the code, to allow simulation of transport through either a single fracture, or, by adopting a continuum approach to represent fracture distribution, through multiple fractures. Successful verification of the modified program against analytical solutions for transport through fractured rock and cracked cementitious media is presented. An application of the modified program to study the evolution of the aqueous chemistry within a repository vault containing a single fracture through the cementitious backfill is also discussed.

Modelling Radionuclide Transport in Cracks Through Cemented Radioactive Waste

1994 ◽  
Vol 353 ◽  
Author(s):  
A. V. Chambers
Keyword(s):  
Radioactive Waste ◽  
Computer Programs ◽  
Intermediate Level ◽  
Radionuclide Transport ◽  
Intermediate Level Radioactive Waste ◽  
The Uk ◽  
Radionuclide Release

AbstractIt is currently proposed to site the UK repository for intermediate-level radioactive waste (ILW) underground at a depth of several hundred metres, and to use a cementitious backfill to fill spaces between disposal packages within the repository vaults. Flow of water through the repository could be concentrated within cracks that may form in the backfill. This paper describes the CRACK and CRACK2 computer programs. These are used to predict radionuclide release via cracks, and radionuclide distributions within the vault. The programs are applied to an assessment of the release of inventory- and solubility-limited radionuclides from hypothetical ILW vaults. Calculations are reported for different densities of cracking, and for different repository designs, and the dominant modes of transport within cracks in repository vaults are discussed.

scholarly journals Fracture System and Rock-Mass Characterization by Borehole Camera Surveying: Application in Dimension Stone Investigations in Geologically Complex Structures

2021 ◽  
Vol 11 (2) ◽  
pp. 764
Author(s):  
Ivica Pavičić ◽  
Ivo Galić ◽  
Mišo Kucelj ◽  
Ivan Dragičević
Keyword(s):  
Rock Mass ◽  
Fractured Rock ◽  
Low Cost ◽  
Fracture Pattern ◽  
Dimension Stone ◽  
Rock Mass Characterization ◽  
Size And Shape ◽  
Distribution Parameters ◽  
Borehole Camera ◽  
Fracture Distribution

The successful exploration of dimension stone mainly depends on the quality, size, and shape of extractable blocks of dimension stone. The investigated area is in the Pelješac Peninsula (Croatia), in the External Dinarides orogeny, built from thick carbonate succession, characterized by relatively small deposits of high-quality dimension stone. These conditions demand challenging geological investigations in the “pre-quarry” phase to find optimal quarry location. The size and shape of dimension stone blocks are mainly controlled by fracture pattern systems. In the rugged, covered terrains, it is very hard to obtain a satisfactory amount of fracture data from the surface, so it is necessary to collect them from the underground. Borehole camera technology can visualize the inner part of the rock mass and measure the fracture characteristics. The main conclusions are as follows: (1) the digital borehole camera technology provides a quick, effective, and low-cost geological survey of fractured rock mass; (2) statistical fracture distribution parameters, P10, fracture spacing, Volumetric Joint Count (Jv) based on borehole wall survey can reflect the integrity of rock mass, providing a solid decision-making base for further investment plans and dimension stone excavation method.

Channeling Flow and Solute Transport in a Single Fracture

2013 ◽  
Vol 316-317 ◽  
pp. 632-635
Author(s):  
Ye Fei Tan ◽  
Zhi Fang Zhou ◽  
Shi Qiang Wu ◽  
Xing Hua Xie ◽  
Bo Ning
Keyword(s):  
Finite Element Method ◽  
Drinking Water ◽  
Breakthrough Curve ◽  
Laboratory Experiments ◽  
Fractured Media ◽  
Single Fracture ◽  
The Finite Element Method ◽  
Dispersive Equation ◽  
One Dimensional ◽  
Channeling Flow

Groundwater in fractured media plays an important role in drinking water supply, and the understanding of its principle mechanisms is essential for securing the groundwater exploring and utilization. In this paper, a novel conceptual fracture model was presented on the basis of the reality of channeling flow in natural fractures and laboratory experiments were conducted for the purpose of getting a better understanding of the step-like breakthrough curve (BTC). Experimental results were fitted with convective dispersive equation (CDE) and compared with those of the finite element method (FEM) models. Results showed that the traditional one-dimensional CDE was invalid in the fitting of a step-like BTC and needed to be improved.

Identification of sorption processes and parameters for radionuclide transport in fractured rock

2012 ◽  
Vol 414-415 ◽  
pp. 220-230 ◽  
Author(s):  
Zhenxue Dai ◽  
Andrew Wolfsberg ◽  
Paul Reimus ◽  
Hailin Deng ◽  
Edward Kwicklis ◽  
...  
Keyword(s):  
Fractured Rock ◽  
Radionuclide Transport

scholarly journals Laboratory experimental investigation of heat transport in fractured media

2016 ◽  
Author(s):  
Claudia Cherubini ◽  
Nicola Pastore ◽  
Concetta I. Giasi ◽  
Nicoletta Maria Allegretti
Keyword(s):  
Heat Transport ◽  
Power Plants ◽  
Time Moment ◽  
Experimental Studies ◽  
Renewable Resource ◽  
Fractured Media ◽  
Single Fracture ◽  
Tracer Transport ◽  
Transport Dynamics ◽  
Experimental Apparatus

Abstract. Low enthalpy geothermal energy is a renewable resource that is still underexploited nowadays, in relation to its potential for development in the society worldwide. Most of its applicabilities have already been investigated, such as: heating and cooling of private and public buildings, roads defrost, cooling of industrial processes, food drying systems, desalination. One of the major limitations related to the choice of installing low enthalpy geothermal power plants regards the initial investment costs. In order to increase the optimal efficiency of installations which use groundwater as geothermal resource, flow and heat transport dynamics in aquifers need to be well characterized. Especially in fractured rock aquifers these processes represent critical elements that are not well known. Therefore there is a tendency to oversize geothermal plants. In literature there are very few studies on heat transport especially in fractured media. This study is aimed to deepen the understanding of this topic through heat transport experiments in fractured network and their interpretation. The heat transfer tests have been carried out on the experimental apparatus previously employed to perform flow and tracer transport experiments, which has been modified in order to analyze heat transport dynamics in a network of fractures. In order to model the obtained thermal breakthrough curves, the Explicit Network Model (ENM) has been used, which is based on an adaptation of a Tang's solution for the transport of the solutes in a semi-infinite single fracture embedded in a porous matrix. Parameter estimation, time moment analysis, tailing character and other dimensionless parameters have permitted to better understand the dynamics of heat transport and the efficiency of heat exchange between the fractures and matrix. The results have been compared with the previous experimental studies on solute transport.

A SINGULAR PERTURBATION PROBLEM IN FRACTURED MEDIA WITH PARALLEL DIFFUSION

1998 ◽  
Vol 08 (04) ◽  
pp. 645-655 ◽  
Author(s):  
J. DAVID LOGAN ◽  
GLENN LEDDER ◽  
MICHELLE REEB HOMP
Keyword(s):  
Boundary Condition ◽  
Singular Perturbation ◽  
Porous Matrix ◽  
Fractured Media ◽  
Singular Perturbation Problem ◽  
Single Fracture ◽  
Direction Parallel ◽  
Flux Boundary Condition ◽  
Perturbation Problem ◽  
Parallel Diffusion

We study differential equations that model contaminant flow in a semi-infinite, fractured, porous medium consisting of a single fracture channel bounded by a porous matrix. Models in the literature usually do not incorporate diffusion in the porous matrix in the direction parallel to the fracture, and therefore they must omit a no-flux boundary condition at the edge, which, in some problems, may be unphysical. Herein we show that the problem usually treated in the literature is the outer problem for a correctly posed singular perturbation problem which includes diffusion in both directions as well as the no-flux boundary condition.

scholarly journals Laboratory experimental investigation of heat transport in fractured media

2017 ◽  
Vol 24 (1) ◽  
pp. 23-42 ◽  
Author(s):  
Claudia Cherubini ◽  
Nicola Pastore ◽  
Concetta I. Giasi ◽  
Nicoletta Maria Allegretti
Keyword(s):  
Heat Transport ◽  
Time Moment ◽  
Fractured Media ◽  
Single Fracture ◽  
Tracer Transport ◽  
Initial Development ◽  
Capital Costs ◽  
Transport Dynamics ◽  
Experimental Apparatus ◽  
Geothermal Power

Abstract. Low enthalpy geothermal energy is a renewable resource that is still underexploited nowadays in relation to its potential for development in society worldwide. Most of its applications have already been investigated, such as heating and cooling of private and public buildings, road defrosting, cooling of industrial processes, food drying systems or desalination. Geothermal power development is a long, risky and expensive process. It basically consists of successive development stages aimed at locating the resources (exploration), confirming the power generating capacity of the reservoir (confirmation) and building the power plant and associated structures (site development). Different factors intervene in influencing the length, difficulty and materials required for these phases, thereby affecting their cost. One of the major limitations related to the installation of low enthalpy geothermal power plants regards the initial development steps that are risky and the upfront capital costs that are huge. Most of the total cost of geothermal power is related to the reimbursement of invested capital and associated returns. In order to increase the optimal efficiency of installations which use groundwater as a geothermal resource, flow and heat transport dynamics in aquifers need to be well characterized. Especially in fractured rock aquifers these processes represent critical elements that are not well known. Therefore there is a tendency to oversize geothermal plants. In the literature there are very few studies on heat transport, especially on fractured media. This study is aimed at deepening the understanding of this topic through heat transport experiments in fractured networks and their interpretation. Heat transfer tests have been carried out on the experimental apparatus previously employed to perform flow and tracer transport experiments, which has been modified in order to analyze heat transport dynamics in a network of fractures. In order to model the obtained thermal breakthrough curves, the Explicit Network Model (ENM) has been used, which is based on an adaptation of Tang's solution for the transport of the solutes in a semi-infinite single fracture embedded in a porous matrix. Parameter estimation, time moment analysis, tailing character and other dimensionless parameters have permitted a better understanding of the dynamics of heat transport and the efficiency of heat exchange between the fractures and the matrix. The results have been compared with the previous experimental studies on solute transport.

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