William Dershowitz

University of Washington Seattle | UW · Department of Civil and Environmental Engineering

Common approaches to slope stability for rock slopes involve representing the rock mass as a continuum. Rock mass properties are estimated based on the intact properties of the rock and on the nature of the rock fabric, notably fracture spacing and condition. However, typically there are one or more well-developed fracture sets that provide prefere...

Step path slope failures form as a combination of sliding on fracture surfaces and tensile failure of rock bridges between those fractures. This paper presents a new method for estimating rock bridges using a searching algorithm that identifies potential failure pathways through Discrete Fracture Network (DFN) models which more realistically repres...

Fractured rocks, specifically sedimentary sequences, present a particular challenge for grouting, as major connected fractures that must be sealed will rarely be intersected by vertical groutholes. The aperture controlled grouting (ACG) method can be readily applied using discrete fracture network (DFN) analysis approaches to understand the pattern...

URTeC 1581931 Many unconventional reservoirs contain natural fractures. These fractures may be non-conductive but open preferentially during hydraulic fracturing treatment, or they may be conductive prior to treatment and provide an enlarged tributary drainage volume with different lateral extents than those suggested by conventional models of unco...

URTeC 1582243 Hydraulic fracture simulation is essential to safe, efficient, and productive development of many unconventional resources, including shale gas and oil, tight sands, and increasingly, even fractured carbonates. Hydraulic fracture propagation geometry, and the geometry of both inflated and reactivated (sheared) natural fractures, can b...

This paper presents a case study of Discrete Fracture Network (DFN) simulation for rock slope wedge stability for a site in Sweden. While conventional wedge stability uses a combinatoric approach, the DFN approach uses stochastic DFN realizations of fracture geometry. As a result, the DFN approach provides a probability of failure, while the conven...

The development and implementation of a hybrid discrete fracture network/equivalent porous medium (DFN/EPM) approach to groundwater flow at the Gyeong-Ju low- and intermediate-level radioactive waste (LILW) disposal site in the Republic of Korea is reported. The geometrical and hydrogeological properties of fractured zones, background fractures and...

The effectiveness of grouting fractured rock depends on the distance that grout penetrates into individual fractures and spreads into connected fracture networks. Assessing grout spread, and the consequent effect on groundwater flow, requires consideration of the 3-D geometry and hydraulic properties of the natural fracture network. Discrete fractu...

This paper describes an approach for assessing the geosphere performance of nuclear waste disposal in fractured rock. In this approach, a three-dimensional heterogeneous channelnetwork model is constructed using a stochastic discrete fracture network (DFN) code. Radionuclide migration in the channel-network model is solved using the Laplace transfo...

This paper describes the development of a 3-dimensional Discrete Fracture Network (DFN) approach for simulation and evaluation of hydraulic fracturing in low permeability fractured rock in the FracMan® reservoir analysis tool. The approach is based on an empirical algorithm approximating the effect of natural fractures and in situ stress on hydraul...

Although radionuclide tracer tests have been carried out for over 30 years, the role of tracer tests in radioactive waste repository performance assessment (PA) has been questioned due to the differences between the time scales for tracer tests and PA. The possibility of using in situ tracer tests to constrain PA time scale (over 10,000 years) solu...

This paper examines the significance of mechanical layering for “blocky” rock mass deformation around underground openings excavated through sedimentary rocks. The analysis is based on an integration of geologically based discrete fracture models (“geoDFN”), which incorporate “mechanical layering”, with the numerical discrete element method—the dis...

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1985. Supervised by Herbert H. Einstein. Includes bibliographical references (p. 745-764).

Sedimentary rocks exhibit a geological structure known as "mechanical layering" where vertical to sub-vertical joints are bounded by bedding plane boundaries, and a ratio between bed thickness and joint spacing is typically defined. This paper demonstrates the use of geologically based discrete fracture models (geoDFN) which incorporate the "mechan...

This paper presents a discrete fracture approach for improving the efficiency of grout design for tunnels in fractured rock. In this approach the grout injection boreholes and the fractures intersecting them are modeled explicitly. Grout volumes are matched to the volumes of fracture networks directly connected to the grout injection boreholes, app...

The prevalence of block and panel caving mines is predicted to increase as easy access deposits exploited with open pit mining are worked out and mining of deeper deposits is required to meet metal demand. With the caving process from block and panel caving mines relying strongly upon the natural fracture network of the rock mass, there is an assoc...

Crystalline rock is typically viewed as consisting of essentially impervious rock blocks separated by fractures. These fractures include both high-conductivity structures along which most of the flow takes place, and lower- conductivity fractures which are either hydraulically inactive, or carry very low flow. A number of tracer tests ("Tracer Rete...

The TRUE-1 tracer experiments at Aspo, Sweden (Winberg et al., 2000) provide an extensive database of solute transport behavior in a 20-meter scale fracture. As part of the TRUE-1 experiments, an extensive suite of conservative and sorbing tracer transport tests were carried out on a pathway of approximately 5 m length between two boreholes in a si...

Tracer experiments have been performed since 1995 at the underground SKB Äspö Hard Rock Laboratory, southeastern Sweden. Non-sorbing and sorbing radioactive tracer experiments of the TRUE Block Scale Project were conducted in single fractures and a network of fractures with support from a comprehensive program of laboratory experiments, geological,...

This paper describes the development of a hybrid discrete fracture network/continuum (DFN/EPM) model for an underground rock research laboratory. This model is based on a 9 km scale discrete fracture network (DFN) model, which includes a combination of conductive discrete fractures and partially sealing, non-planar sub-vertical faults. In addition,...

The JNC/Golder team has developed discrete fracture network (DFN) approaches for modelling solute transport in fractured rocks with multiple immobile zones. This approach provides significant advantages, including its ability to directly model the geometry and transport pathways, and the variation of transport properties along those pathways. Immob...

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1979. MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. Bibliography: leaves 201-208. by William Simon Dershowitz. M.S.

This report describes the JNC/Golder team’s flow and transport analysis and modeling in support of Task BS2B of the TRUE Block Scale Continuation project. BS2B focuses on a series of hypotheses concerning conservative and reactive transport in pathways defined within a rock block of scale approximately 100 m. Simulations and analyses were carried o...

This paper describes recent advances in discrete fracture network (DFN) modeling and analysis. These advances represent a significant convergence between DFN and EPM methods for flow, combined with significant increases in geological realism, and more appropriate solute transport conceptual models.

This paper proposes a method for quantitative integration of seismic(elastic) anisotropy attributes with reservoir-performance data as an aid in characterizing systems of natural fractures in hydrocarbon reservoirs. This method is demonstrated through application to history matching of reservoir performance using synthetic test cases. Discrete-feat...

Gel injection is used with water injection in fractured and heterogeneous reservoirs to decrease water production and improve the oil sweep efficiency. Gel treatments are able to achieve this because the gel is preferentially deposited to the most conductive fractures, blocking the water flow through those structures, and forcing to water to displa...

This paper presents an approach for estimating the size distributions of elliptical discontinuities. This is an extension of approaches for estimating size distributions of circular discontinuities. By assuming an elliptical shape and changing the aspect ratio k of the ellipses (i.e. the ratio of the major to minor axes), many real discontinuities...

This report describes the participation of the JNC/Golder team in the coupled hydrogeological/geochemical pathway modeling of the construction of the Äspö Hard Rock Laboratory during the period 1990 through 1996. Modeling was carried out to the specifications of the Äspö Task Force on Modeling of Groundwater Flow and Transport of Solutes, Task 5. T...

This report describes the participation of the JNC/Golder team in the coupled hydrogeological/geochemical pathway modeling of the construction of the Äspö Hard Rock Laboratory during the period 1990 through 1996. Modeling was carried out to the specifications of the Äspö Task Force on Modeling of Groundwater Flow and Transport of Solutes, Task 5. T...

This report describes preliminary modeling to demonstrate the application of FracMan Discrete Feature Network and PAWorks Pathways Analysis software to support Task 5, site scale hydro-geochemical modeling of the Äspö HRL site. The modeling was carried out based on preliminary project data, and will be updated during 1999. The analysis defined the...

This report describes channel network (CN) and discrete fracture network (DFN) flow and transport modeling by the JNC/Golder team for the Äspö TRUE Block Scale project Tracer Testing Stage (TTS). The fracture network model combines the deterministic structures of the Revised March 2000 Hydro-structural model (Hermanson and Doe, 2000) and the by Der...

This progress report describes activities during the period January 1, 1999 to June 30, 1999. Work was carried out on 21 tasks. The major activity during the reporting period was the development and preliminary application of discrete fracture network (DFN) models for Stoney Point, South Oregon Basin, and North Oregon Basins project study sites. In...

This paper summarizes discrete fracture network (DFN) analysis of the Tracer Retention Understanding Experiments “TRUE-1” carried out at the Äspö Hard Rock Laboratory in Sweden from 1995 through 2000. These studies confirmed the ability of the DFN approach, together with conventional advection-dispersion-diffusion assumptions to calibrate and predi...

The Äspö Task Force on Modelling of Groundwater Flow and Transport of Solutes is a forum for the international organisations supporting the Äspö HRL Project. The purpose of the Task Force is to interact in the area of conceptual and numerical modelling of groundwater flow and solute transport in fractured rock. Task 4 of the Äspö Modelling Task For...

This paper summarizes discrete fracture network (DFN) analysis of the Tracer Retention Understanding Experiments “TRUE-1” carried out at the Äspö Hard Rock Laboratory in Sweden from 1995 through 2000. These studies confirmed the ability of the DFN approach, together with conventional advection-dispersion-diffusion assumptions to calibrate and predi...

The discrete feature network (DFN) approach offers many key advantages over conventional dual porosity (DP) approaches, particularly when issues of connectivity dominate recovery and reservoir stimulation in fractured and heterogeneous reservoirs. DP models have been developed for complex multiphase and thermal effects, and have been implemented fo...

This paper describes the development of a discrete feature network (DFN) model for the South Oregon Basin field in the Big Horn Basin of Wyoming. This DFN model is being developed to support well placement and gel treatment in order to recover previously bypassed oil in this highly heterogeneous, structurally controlled carbonate reservoir. The DFN...

Discrete fracture network (DFN) models generally require solution of flow and transport equations in three-dimensional networks of either disc, polygonal, or pipe elements. Pipe network elements have significant advantages in computation for both flow and transport. However, there is a need to develop an efficient procedure for derivation of the pr...

This paper illustrates how Discrete Fracture Network (DFN) technology can serve as a basis for the calculation of reservoir engineering parameters for the development of fractured reservoirs. It describes the development of quantitative techniques for defining the geometry and volume of structurally controlled compartments. These techniques are bas...

The dimension of a well test indicates how conductance (the product of hydraulic conductivity and flow area) changes with distance from a pumping well. Dimensional information is very important because it is one of the few direct hydraulic measures of rock mass heterogeneity and connectivity. Although a relationship between flow geometry and well t...

In rock masses where fracture flow greatly exceeds flow through the rock matrix, the matrix provides a storage porosity which needs to be considered for transient flow, and for solute transport. This paper presents a dual-porosity, single permeability approach for evaluation of flow and transport in fractured rock. The fracture network flow approac...

The water level of the Dead Sea, a terminal hypersaline lake (total dissolved solids, approximately 340 g/L) has decreased at an average rate of 0.5 m/yr since 1960 and by 0.8 m/yr between 1981 and 1989. The dramatic long-term water level variation of the Dead Sea and the seasonal short-term fluctuations are accompanied by parallel variations of gr...

Engineering fractured rock masses requires accurate geometrical description of the fractures. A critical parameter is fracture size which strongly affects the degree of interconnection between fractures, and consequently permeability, mass transport and incipient instability. Existing methods for estimating size from borehole data or from planar ex...

Discrete fracture analysis provides the crucial link between the complex geometries and structural control of reservoir geology and the finite difference continua of reservoir engineering. This approach is applicable to reservoirs where heterogeneity is the result of the combination of a primary permeability defined by features such as faults, frac...

Hydrogeology is a discipline that may be applied to environmental investigations at wastedisposal sites. The information objectives from such investigations are diverse, and necessitate the development of a variety of data types. Presented herein is an explanation of the logic inherent in the development of data-management system, illustrating how...

Representation of geological discontinuities by means of structural diagrams, often called stereoplots, is standard practice. When the dip directions of such discontinuities form a roughly circular cluster about the horizontal, bimodal pole distributions are observed (and vice versa). This is problematic in the interpretation of any rock-engineerin...

Many rock engineering geologic problems can be better solved if the genesis of rock fractures (rock joints) is understood. This paper concentrates on tensile fractures and shear fractures created in predominately compressive stress fields; such fractures prevail in many areas. Stress-based and fracture-mechanics-based concepts are introduced. They...

This paper develops a discrete fracture approach to flow analysis of dual-porosity systems. The well-established methods of analyzing dual-porosity flow in fractures deal primarily with matrix blocks having idealized shapes, such as slabs, blocks, and spheres. While these geometric simplifications allow analytical solution of difficult now problems...

A number of problems involving flow through rock masses need to be analyzed by fracture flow models rather than equivalent porous medium models. Two- and three-dimensional fracture flow models have been developed. In this paper, computational comparisons are made. They show that different fracture geometries lead to considerably different conductiv...

The media and sites considered include: (1) basalt at Hanford, Washington; (2) tuff at Yucca Mountain, Nevada Test Site; (3) domal salt at specific Gulf Coast sites; (4) bedded salt at an unspecified site; and (5) granite at an unspecified site. A licensing perspective is outlined and a defensible rationale developed and utilized for the test selec...

The data base developed for selection and evaluation of geothermal subsidence case studies is presented. Data from this data base were used in case studies of Wairakei, The Geysers, and Austin Bayou Prospect (Report LBL 10571).

The results of an assessment of existing mathematical models for subsidence simulation and prediction are summarized. The following subjects are discussed: the prediction process, physical processes of geothermal subsidence, computational models for reservoir flow, computational models for deformation, proficiency assessment, and real and idealized...

There are a variety of theories, techniques, and parameters in the subsidence literature. Biot's theory, Terzaghi's theory, and the theory of interacting continua (TINC) are used to explain solid-fluid interaction; stress-strain theories range from linear elastic to e-log p to plasticity and pore-collapse theories. Parameters are numerous: void rat...

An assessment was performed of existing mathematical models for subsidence simulation and prediction. Detailed analyses are presented of the theory, power, usability, and performance of the seven models used in conjunction with an ongoing research program aimed at improved understanding and control of ground movements caused by geothermal power pro...

This report describes progress on the project, {open_quotes}Fractured Reservoir Discrete Feature Network Technologies{close_quotes} during the period March 7, 1996 to February 28, 1997. The report presents summaries of technology development for the following research areas: (1) development of hierarchical fracture models, (2) fractured reservoir c...