FIELD AND LABORATORY EXPERIMENT TO 

ESTIMATE BULKING FACTOR FOR A LITHOPHYSAL 

TUFF, FRAN RIDGE, YUCCA MOUNTAIN, NEVADA 

Prepared for 

U.S. Nuclear Regulatory Commission 

Contract NRC–02–07–006 

Prepared by 

Danielle Wyrick1

Randall Fedors3

Kevin Smart1 

Robert Lenhard2 

Ronald McGinnis1 

Donald Bannon2 

Chandrika Manepally 

1

Department of Earth, Material, and Planetary Sciences 

San Antonio, Texas 

2Center for Nuclear Waste Regulatory Analyses 

San Antonio, Texas 

3U.S. Nuclear Regulatory Commission 

Washington DC 

September 2011
ii 

ABSTRACT 

This report presents the results of field work and laboratory testing to estimate the bulking factor 

for the Topopah Springs welded lower lithophysal tuff, Yucca Mountain, Nevada. Bulking factor 

is used in performance assessment analyses to constrain the amount of rubble spalling from the 

drift ceiling and covering the drip shield. The field and laboratory testing utilized data and rock 

taken from an analog site for the drift environment. The field site was a surface exposure of the 

lower lithophysal unit on the south end of Fran Ridge, which is a small ridge east of 

Yucca Mountain. Rock fragments from several outcrops were collected, shipped to the 

laboratory, and repacked using several approaches to obtain estimates of rubble bulk density, 

which leads directly to estimates of bulking factor. The dominant shape of fragments could be 

described as bladed and elongated. Bulking factors estimated from these experiments range 

from 1.62 to 1.83. Collection and analysis of fracture and fragment shape data from the analog 

site could facilitate both the correlation of experiment data with the range of fracturing along 

drifts, and estimation of permeability and thermal conductivity of rubble needed for modeling 

thermohydrological conditions. The approaches used for laboratory repacking of the rock 

fragments illustrate different extents of packing, but these approaches may not directly be 

correlated with the physical effects of static loads or shaking due to earthquakes as expected 

over long time periods in drifts. Thus, these estimates of bulking factor reported herein likely 

reflect early values of bulking factor or reflect the upper portion of the range of long-term bulking 

factors expected in drifts. 
iii 

CONTENTS 

Section Page 

ABSTRACT ................................................................................................................................... ii 

FIGURES ..................................................................................................................................... iv 

TABLES ....................................................................................................................................... vi 

ACKNOWLEDGMENTS .............................................................................................................. vii 

1 INTRODUCTION ................................................................................................................ 1-1

2 FIELD EXPERIMENT ......................................................................................................... 2-1

2.1 Field Investigation ...................................................................................................... 2-1

2.2 Fracture Characterization .......................................................................................... 2-3

2.3 Rubble Characterization ............................................................................................ 2-5

2.3.1 Clast Shape Distribution ................................................................................ 2-5

2.3.2 Clast Size Distribution .................................................................................. 2-22

3 LABORATORY MEASUREMENT OF BULKING FACTOR ................................................ 3-1

3.1 Introduction ................................................................................................................ 3-1

3.2 Bulk Density of Rubble .............................................................................................. 3-1

4 SUMMARY .......................................................................................................................... 4-1

5 REFERENCES ................................................................................................................... 5-1
iv 

FIGURES 

Figure Page 

2-1 A Location Map of Fran Ridge Outcrop Sites Inset Shows Location With Respect to 

the Exploratory Studies Facility (ESF) at Yucca Mountain ............................................. 2-2 

2-2 Example Rubble Pile Collected From Plot 2 Outcrop at Fran Ridge .............................. 2-3 

2-3 Examples of Basic Rubble Shapes. (A) Platy, (B) Cubic, (C) Bladed, 

 and (D) Elongate ............................................................................................................ 2-4 

2-4 Equal-Area Stereonet Plot of Poles to Fracture Planes From Fracture Orientation 

Data Collected at Fran Ridge Outcrop (Green Circles) and the ESF/ECRB Detailed 

Line Survey Small-Scale Fracture Data ......................................................................... 2-6 

2-5 Equal-Area Stereonet Plot of Poles to the Mean Fracture Set Planes ........................... 2-6 

2-6 A Modified Sneed and Folk Diagram Representation of Particle Shape ....................... 2-8 

2-7 Modified Sneed and Folk Diagram of All Rubble Shape Data ........................................ 2-9 

2-8 Rubble Shape Major Classification by Percentage for All Rubble Shape Data .............. 2-9 

2-9 Rubble Shape Major Classification by Percentage for All Rubble Shape Data ............ 2-10 

2-10 Rubble Shape Classification Detailed by Percentage for All Rubble Shape Data ....... 2-10 

2-11 Field Photograph of Talus Pile Location for Plot 1A ..................................................... 2-11 

2-12 Modified Sneed and Folk Diagram of Plot 1A Rubble Shape Data .............................. 2-11 

2-13 Rubble Shape Major Classification by Percentage for Plot 1A Rubble Shape Data .... 2-12 

2-14 Rubble Shape Major Classification by Percentage for Plot 1A Rubble Shape Data .... 2-12 

2-15 Rubble Shape Classification Detail by Percentage for Plot 1A Rubble Shape Data .... 2-13 

2-16 Field Photograph of Rubble Collection Area Plot 2 ...................................................... 2-13 

2-17 Modified Sneed and Folk Diagram of Plot 2A Rubble Shape Data .............................. 2-14 

2-18 Rubble Shape Major Classification by Percentage for Plot 2A Rubble Shape Data .... 2-14 

2-19 Rubble Shape Major Classification by Percentage for Plot 2A Rubble Shape Data .... 2-15 

2-20 Rubble Shape Classification Detail by Percentage for Plot 2A Rubble Shape Data .... 2-15 

2-21 Modified Sneed and Folk Diagram of Plot 2B Rubble Shape Data .............................. 2-16 

2-22 Rubble Shape Major Classification by Percentage for Plot 2B Shape Data ................ 2-16 

2-23 Rubble Shape Major Classification by Percentage for Plot 2B Rubble Shape Data .... 2-17 

2-24 Rubble Shape Classification Detail by Percentage for Plot 2B Rubble Shape Data .... 2-17 

2-25 Modified Sneed and Folk Diagram of Plot 2C Rubble Shape Data .............................. 2-18 

2-26 Rubble Shape Major Classification by Percentage for Plot 2C Rubble Shape Data .... 2-18 

2-27 Rubble Shape Major Classification by Percentage for Plot 2C Rubble Shape Data .... 2-19 

2-28 Rubble Shape Classification Detail by Percentage for Plot 2C Rubble Shape Data .... 2-19 

2-29 Field Photograph of Talus Pile Location for Plot 3 ....................................................... 2-20 

2-30 Modified Sneed and Folk Diagram of Plot 3 Rubble Shape Data ................................ 2-20 

2-31 Rubble Shape Major Classification by Percentage for Plot 3 Rubble Shape Data ...... 2-21 

2-32 Rubble Shape Major Classification by Percentage for Plot 3 Rubble Shape Data ...... 2-21 

2-33 Rubble Shape Classification Detail by Percentage for Plot 3 Rubble Shape Data ...... 2-22 

2-34 Frequency of Length (Longest Orthogonal Dimension) Measurements ....................... 2-23 

2-35 Cumulative Frequency Distribution Plot of Rubble Clast Length, Width, and Height 

From All Plots ............................................................................................................... 2-23 

2-36 Frequency of Clast Volume. Note That Volume Measurements Are Truncated at 

4,000 cm3 [244.09 in3

] To Illustrate Smaller Values...................................................... 2-24 

2-37 Cumulative Frequency Distribution Plot of Rubble Clast Volume From All Plots ......... 2-24 

2-38 Plot of (Length/Width) Versus (Width/Height) Illustrates the Limited Binning 

Effect Described on Size Distributions. ........................................................................ 2-25 

2-39 Cumulative Frequency Distribution Plot of Rubble Clast Volume From Plot 1 ............. 2-25 
v 

FIGURES (continued) 

Figure Page 

2-40 Cumulative Frequency Distribution Plot of Rubble Clast Length, Width, and Height 

From Plot 1 ................................................................................................................... 2-26 

2-41 Cumulative Frequency Distribution Plot of Rubble Clast Volume From Plot 2A .......... 2-26 

2-42 Cumulative Frequency Distribution Plot of Rubble Clast, Length, Width, and 

Height From Plot 2A ..................................................................................................... 2-27 

2-43 Cumulative Frequency Distribution Plot or Rubble Clast Volume From Plot 2B .......... 2-27 

2-44 Cumulative Frequency Distribution Plot of Rubble Clast Length, Width, and Height 

From Plot 2B ................................................................................................................ 2-28 

2-45 Cumulative Frequency Distribution Plot of Rubble Clast Volume From Plot 2C .......... 2-28 

2-46 Cumulative Frequency Distribution Plot of Rubble Clast Length, Width, and 

Height From Plot 2C ..................................................................................................... 2-29 

2-47 Cumulative Frequency Distribution Plot of Rubble Clast Volume From Plot 3 ............. 2-29 

2-48 Cumulative Frequency Distribution Plot or Rubble Clast Length, Width, and 

Height From Plot 3 ....................................................................................................... 2-30

3-1 Experimental Setup To Determine Mass Density of Packed Rubble 

(A) Container 1—Cubic Shape, (B) Top View of Container 1, and 

(C) Container 2—Rectangular Shape ............................................................................ 3-3 
vi 

TABLES 

Table Page 

2-1 Summary of Fran Ridge Fracture Data Collected at All Plots ........................................ 2-4 

2-2 Summary of Fran Ridge Fracture Data Collected at Plot 1 ............................................ 2-7 

2-3 Summary of Fran Ridge Fracture Data Collected at Plot 2 ............................................ 2-7 

2-4 Summary of Fran Ridge Fracture Data Collected at Plot 3 ............................................ 2-7 

3-1 Bulk Density of Rubble From Laboratory Measurements Assuming In-Situ (Intact) 

Bulk Density of 1,979 kg/m3

 ........................................................................................... 3-4 
vii 

ACKNOWLEDGMENTS 

This report describes work performed by the Center for Nuclear Waste Regulatory Analyses 

(CNWRA®) and its contractors for the U.S. Nuclear Regulatory Commission (USNRC) under 

Contract No. NRC–02–07–006. The activities reported here were performed on behalf of the 

USNRC Office of Nuclear Material Safety and Safeguards, Division of High-Level Waste 

Repository Safety and Safeguards, Division of High-Level Waste Repository Safety. This report 

is an independent product of the CNWRA and does not necessarily reflect the view or regulatory 

position of the USNRC. The USNRC staff views expressed herein are preliminary and do not 

constitute a final judgment or determination of the matters addressed or of the acceptability of 

any licensing action that may be under consideration at USNRC. 

The authors gratefully acknowledge A. Morris for his technical review, E. Pearcy for his 

programmatic review, L. Mulverhill for her editorial review, and A. Ramos for his 

administrative support. 

QUALITY OF DATA, ANALYSES, AND CODE DEVELOPMENT 

DATA: All CNWRA-generated original data contained in this report meet quality assurance 

requirements described in the Geosciences and Engineering Division Quality Assurance 

Manual. Sources of other data should be consulted for determining the level of quality of those 

data. The work presented in this report is documented in Scientific Notebook Nos. 852 and 

779E (Wyrick, 2011; Bannon, 2006). 

ANALYSES AND CODES: Microsoft® Excel® 2003 (Microsoft Corporation, Inc., 2003) and 

RockWare StereoStat® Version 1.4 (Rockware, Inc. 2004). 

REFERENCES 

Bannon, D. “Rubble Flow Laboratory Experiment.” Scientific Notebook 779E. 

San Antonio, Texas: CNWRA. 2006. 

Microsoft Corporation, Inc. “Microsoft Excel 2003.” Redmond, Washington: 

Microsoft Corporation. 2003. 

Rockware, Inc. “StereoStat Version 1.4.” Golden, Colorado: Rockware, Inc. 2004. 

Wyrick, D. “Fran Ridge Topopah Springs Welded (TSw) Lower Lithophysal Unit Rubble 

Characterization.” Scientific Notebook 852. San Antonio, Texas: CNWRA. 2011. 
1-1 

1 INTRODUCTION 

Field and laboratory experiments were performed to help understand the nature of rockfall that 

may form a rubble pile on top of and to the sides of drip shields in emplacement drifts of a 

proposed high-level waste repository at Yucca Mountain. The nature and characteristics of 

rubble that may result from degradation of emplacement drifts in welded lithophysal rocks have 

not been previously determined. Spalling of rock during the drift-scale heater test and 

fragments found in the invert in the Exploratory Studies Facility tunnel and enhanced 

characterization of repository block cross-drift provide qualitative information on the size and 

shape of fragments. More detailed and quantitative information on rubble characteristics, 

however, is not available at these locations. 

The field and laboratory work focused on estimation of a bulking factor, which is related to the 

rubble bulk density, and characterized fracture and fragment shape and size information. An 

understanding of the fragment sizes and shapes and their packing could help constrain 

estimates of the bulking factor, which constrains the extent (or thickness) of rubble that may 

occur above drip shields and waste packages. In addition, the size and shape distributions of 

the fragments and their packing in rubble piles are needed to conceptualize and quantify the 

flow of water (liquid and gas phase) and heat transfer (conduction, convection, and radiation) for 

determining the evolution of in-drift environments used in performance assessments of a 

potential repository (e.g., Mohanty, et al., 2006). 

Surface exposure of the Topopah Spring welded lower lithophysal zone at the south end of 

Fran Ridge, Yucca Mountain, were identified as an analog site to the host rock that would 

enable detailed fracture characterization and collection of rubble samples (Smart and Fedors, 

2006). Field work was performed to characterize surface exposures of the Topopah Springs 

welded lower lithophysal tuff (Tptpll)1

 zone on the southern end of Fran Ridge (Wyrick, et al., 

2007). The supposition is that fracture orientation and spacing control the size and shape of 

rock blocks that can form, which in turn influence the assessments of the distribution and size of 

rubble piles that accumulate on waste packages from rock fall (Smart, et al., 2006). The 

objective of the field work was to obtain a more quantitative understanding of rubble size 

distributions by examining fractured outcrops of lower lithophysal rock and nearby talus piles on 

the southern end of Fran Ridge. Degradation in emplacement drifts and the resulting block size 

and bulking factor are influenced by existing fractures. The surface exposures and talus, 

therefore, may provide a link between fracture patterns and rubble fragment size and shape 

distributions that would be useful for understanding drift degradation and the extent of spallation 

in drift ceilings. The effect of surficial processes on fracture and fragment characteristics is 

acknowledged, but neglected, in this study. 

Section 2 of this report describes a focused investigation on the size and shape distributions of 

rubble resulting from fractured lower lithophysal rock, which, along with detailed fracture data 

collection, provided an outcrop-scale rubble characterization for subsequent modeling efforts. 

Section 3 describes laboratory experiments using different packing approaches to estimate a 

range of bulking factors for rubble. 

 

1

Topopah Spring welded Lower Lithophysal zone is used frequently throughout this chapter; therefore, the acronym 

Tptpll will be used. 
2-1 

2 FIELD EXPERIMENT 

Staff made two field excursions to Yucca Mountain as part of an effort to quantify bulking factor 

for a welded lithophysal tuff. The first excursion (Smart and Fedors, 2006) focused on 

familiarization with and visits to surface and subsurface exposures of the Tptpll. During this 

excursion, it was determined that the Topopah Springs welded upper lithophysal zone would not 

serve as a reasonable analog, because of the different character of fracturing compared to that 

of the lower lithophysal unit. The identified analog site at the south end of Fran Ridge exhibited 

a range of fracture densities, due in part to the close proximity to a mapped fault. The second 

excursion focused on excavation and characterization of the selected rubble analog site 

(Wyrick, et al., 2007). 

This section of the report documents the (i) site description, excavation of several plots at 

three intact outcrops, and collection of rubble; (ii) characterization of fracture patterns and 

density in the vicinity of each plot; and (iii) shape and size characterization of rubble fragments 

in the last subsection. 

2.1 Field Investigation 

The south end of Fran Ridge at Yucca Mountain has outcrop exposures of the Tptpll that are 

easily accessible (Figure 2-1) because of close proximity to a road. Three outcrop areas were 

delineated in the field, designated as Plot 1, Plot 2, and Plot 3. Plot 2 was further subdivided for 

rubble collection and characterization into subareas A, B, and C. Fracture data were collected 

from the three field outcrops. Data collection included fracture orientation, spacings, and 

tracelength (where it could be determined). Fracture orientation data were collected as strike, 

dip, and dip direction. Values were then converted to right-hand rule azimuth direction for 

subsequent analyses. 

There were two methods of rubble collection. For the first method, talus was collected from 

immediately beneath outcrops for Plots 1 and 3. Upslope characteristics supported the 

observation that the rubble fragments could only have come from the identified outcrop and 

could not have been transported from adjacent areas (e.g., transported down slope from above 

the outcrop area). Known limitations to the field data at Plots 1 and 3 include secondary 

alteration to the rubble (e.g., weathering and erosion effects). The smallest material in the talus 

piles of Plots 1 and 3 (i.e., fine-grained particles) was not included in the collection or analysis, 

because it was not possible to distinguish particles that originated from the outcrop from those 

introduced by eolian transport or other means. The second method of rubble collection 

minimized the uncertainty of origin for the fine particles. Rock fragments from Plot 2 were 

excavated (i.e., extracted) directly from the outcrop. Minimal prying of outcrop blocks was 

needed because the fracture density was sufficiently high. Staff attempted to collect all particle 

sizes from Plot 2 for subsequent laboratory experiments (see Section 3), including fine-grained 

particles, although the fine material was not used in size distribution analysis. It was not 

possible to quantify the amount of fine-grained material that may have been transported into the 

outcrop or lost to erosion; this represents a limitation to the data collected at Plot 2, but is not 

expected to significantly affect results. The percentage volume of fines in a rubble pile may 

influence the bulking factor (Peele, 1961). 
2-2 

Figure 2-1. A Location Map of Fran Ridge Outcrop Sites Inset Shows Location With 

Respect to the Exploratory Studies Facility (ESF) at Yucca Mountain 

Rubble data were recorded in the field with the following methodology: (i) clasts were 

photographed on a 2 by 2-cm [0.79 by 0.79-in] grid, (ii) the longest orthogonal dimensions 

(length, width, height) were measured, and (iii) all measurements were rounded to the nearest 

0.5-cm [0.20-in] increment. Size limitations on the collection include truncations at the smallest 

and largest scale. The largest rock clasts collected were limited to the outcrop scale. The 

smallest clasts {~3–10 cm [1.18–3.94 in] in longest dimension} were too small to practically 

measure in the field. These clasts were binned by average size, laid out on the grid as close 

together as possible (representing the total length and width), and photographed as a group, 

with the largest and average heights recorded. Rubble particle volumes were averaged for 

these groups by calculating the overall length, width, and height of the collection and dividing by 

the number of clasts in the group. 

Approximately 1,500 rubble clasts were photographed and measured during the field 

examination. Four 0.24-m3

 [55-gal] drums of rubble were collected for further analyses 

(Figure 2-2). Each drum contained a single rubble characterization site (e.g., sample drum #1 

contains rubble collected and characterized from Plot 1). For Plot 2, only subareas A and B 

were collected. The largest clasts measured were wrapped separately on a pallet and tagged 

for sample identification. 
2-3 

Figure 2-2. Example Rubble Pile Collected From Plot 2 Outcrop at Fran Ridge 

Field observations indicated that the talus primarily resulted from degradation along existing 

outcrop fractures. Observations included a positive correlation between higher fracture intensity 

and smaller clast sizes. Also, fracture set orientations contributed to the shape of rock 

fragments (e.g., bladed or elongate). Field observations indicated most rock clasts were 

bladed, elongate, or platy in shape (Figure 2-3). The least frequently encountered shape was 

cubic (i.e., equidimensional). 

2.2 Fracture Characterization 

Three primary fracture sets were defined from the Fran Ridge outcrop data (Table 2-1). 

Fracture data were analyzed with RockWare StereoStat® Version 1.4 (RockWare, Inc., 2004) for 

orientation and dispersion values to determine fracture sets. Set 1 is a north-northwest striking, 

steeply dipping set with an average strike and dip of 166°/73°. Mean spacing for Set 1 fractures 

is 7 cm [2.76 in]. Set 2 is an east-west-striking, moderately dipping set with an average strike 

and dip of 101°/69°. Mean spacing for Set 2 fractures is 16 cm [6.30 in]. Set 3 is a 

subhorizontal fracture set with a mean strike and dip of 355°/15° and spacing of 9 cm [3.54 in]. 

A comparison of the Fran Ridge outcrop fractures (outcrop scale) in the Tptpll to the fracture 

data Smart, et al. (2006) analyzed for the same zone recorded in the Detailed Line Survey in the 

Exploratory Studies Facility (ESF)1

 and enhanced characterization of repository block (ECRB)2 

 

1

Exploratory Studies Facility is used frequently throughout this chapter; therefore, the acronym ESF will be used. 2

Enhanced characterization of repository block is used frequently throughout this chapter; therefore, the acronym 

ECRB will be used. 
2-4 

Figure 2-3. Examples of Basic Rubble Shapes. (A) Platy, (B) Cubic, (C) Bladed, and 

(D) Elongate. Note That Background Grid Has 2 by 2-cm [0.79 by 0.79-in] Spacing. 

Table 2-1. Summary of Fran Ridge Fracture Data Collected at All Plots 

Fracture Set 

Mean 

Orientation 

Angular 

Standard 

Deviation 

Fisher 

Dispersion 

Coefficient* 

True Spacing (cm) [in] 

Mean Median 

Fran Ridge (this report)

Set 1 129°/72° 64° 13.3 7.3 [2.87] 6.2 [2.44] 

Set 2 101°/69° 17° 21.8 16.3 [6.42] 12.5 [4.92] 

Set 3 355°/15° 12° 42.4 9.1 [3.58] 8.5 [3.35] 

Table 3-7†

Set 1 134°/82° 45° 3.3 10.8 [4.25] 3 [1.18] 

Set 2 079°/82° 21° 14.6 24 [9.45] 12 [4.72] 

Set 3 313°/04° 12° 47.4 10 [3.94] 6 [2.36] 

*The Fisher dispersion coefficient (also referred to as the concentration parameter) is a measure of the degree to 

which spherical data are concentrated around the mean (Fisher, N.I., T. Lewis, and B.J.J. Embleton. Statistical 

Analysis of Spherical Data. Cambridge, United Kingdom: Cambridge University Press. 1993). Larger values of the 

Fisher dispersion coefficient indicate tighter clustering (i.e., less dispersion). 

†Smart, K.J., D.Y. Wyrick, P.S. Landis, and D.J. Waiting. “Summary and Analysis of Subsurface Fracture Data From 

the Topopah Spring Tuff Upper Lithophysal, Middle Nonlithophysal, Lower Lithophysal, and Lower Nonlithophysal 

Zones at Yucca Mountain, Nevada.” CNWRA 2005-04. ML060660009. San Antonio, Texas: Center for Nuclear 

Waste Regulatory Analyses. 2006. 
2-5 

(drift scale) shows similar fracture orientations (strike and dip) and spacing between these 

two sites (Figures 2-4 and 2-5). Both the outcrop-scale and drift-scale fracture analyses 

indicate three primary fracture sets: (i) a north-northeast striking, steeply dipping set; (ii) an 

east-west-striking, steeply dipping set; and (iii) a subhorizontal set. The mean orientation of 

these three primary sets measured at Fran Ridge fall within the angular standard deviation 

(representing the degree of scatter) of the mean fracture set data observed in the ESF and 

ECRB. Fracture lengths between the two sites are not directly comparable (outcrop scale 

versus drift scale) as most fracture tracelengths at the outcrop were truncated because of the 

small exposures. A comparison of fracture spacing at the outcrop scale to the small-scale 

fracture data collected in the ECRB cross drift (cf., Table 2-1 this report; Smart, et al., 2006, 

Table 3-7) shows similar values for fracture spacing. 

Some variations in fracture orientations and spacing are observed for each plot (Tables 2-2 to 

2-4). Notably, Plot 3 differs from Plots 1 and 2 (and the ESF/ECRB fracture data) both in 

fracture set orientations and in fracture spacing. Fracture Set 2 (east-west striking, moderately 

dipping) was not found at Plot 3; instead, north-northwest-striking, steeply dipping and 

north-northeast-striking, steeply dipping fracture sets were observed. Plot 3 had smaller 

fracture spacing values overall. This variation in Plot 3 fracture data is likely due to its proximity 

to a mapped normal fault near the southeast end of Fran Ridge (Day, et al., 1998). 

2.3 Rubble Characterization 

2.3.1 Clast Shape Distribution 

The literature reviewed shows that rubble clast shape influences bulking factor (Pappas and 

Mark, 1993). To characterize the shapes distribution of rubble, a classification system that 

captures the wide range of clast shape is required. A literature search of the types of clast 

shape classifications systems indicates that a modified Sneed and Folk (1958) organization that 

includes shape ranges from cubic (equidimensional), platy (tabular), bladed, and elongate (rod) 

is suitable for these analyses (Sneed and Folk, 1958; Graham and Midgley, 2000). Sneed and 

Folk (1958) diagrams, employing ratios of the three orthogonal particle axes, have been 

advocated as the most appropriate method for unbiased presentation of primary particle shape 

data. A Sneed and Folk (1958) diagram is scaled such that independent (although related) 

variables can be plotted for one axis without necessarily affecting the other two. For any given 

particle, the values of the three axes (length, width, and height) are independent, except that, by 

definition, Length≥Width≥Height. This type of triangular diagram differs from traditional ternary 

plots where the three variables plotted represent relative proportions of a whole (i.e., a decrease 

in one variable will produce increases in one or both of the other variables). The four major 

shape classifications (cubic, platy, elongate, and bladed) are illustrated in Figure 2-6 to show 

the general block shapes and their locations on the chart.

For the major classifications, subdivisions are grouped such that cubic = all cubic values; 

platy = cubic-platy + platy + very platy; bladed = cubic-bladed + bladed + very bladed; and 

elongate = cubic-elongate + elongate + very elongate (Figure 2-6). The major shape 

classifications could be grouped slightly differently (e.g., cubic could include cubic + cubic platy 

+ cubic elongate + cubic bladed). Both values are provided in this report. The most common 

rubble shape was bladed fragments, representing 39–48 percent of all rubble clasts; elongate 

shapes represented 26-31 percent of all rubble. These two primary shapes combined 

comprised 65–79 percent of the outcrop rubble measured. Clast shape data for all the Fran 

Ridge outcrop samples are illustrated in Figures 2-7 to 2-10. 
2-6 

Figure 2-4. Equal-Area Stereonet Plot of Poles to Fracture Planes From Fracture 

Orientation Data Collected at Fran Ridge Outcrop (Green) and the ESF/ECRB Detailed 

Line Survey Small-Scale Fracture Data (Red). (Smart, et al., 2006, Figure 3-10)

Figure 2-5. Equal-Area Stereonet Plot of Poles to the Mean Fracture Set Planes From 

Table 2-1 (Green Circles From Fran Ridge, Red Squares From ESF/ECRB)
2-7 

Table 2-2. Summary of Fran Ridge Fracture Data Collected at Plot 1 

Fracture Set Mean Orientation True Spacing (cm) [in] Mean 

Set 1 170°/71° 10.2 [4.02] 

Set 2 097°/24° 12.1 [4.76] 

Set 3 007°/24° 15.4 [6.06] 

Table 2-3. Summary of Fran Ridge Fracture Data Collected at Plot 2 

Fracture Set Mean Orientation True Spacing (cm) [in] Mean 

Set 1 164°/73° 7.6 [2.99] 

Set 2 102°/69° 17.2 [6.77] 

Set 3 349°/17° 8.4 [3.31] 

Table 2-4. Summary of Fran Ridge Fracture Data Collected at Plot 3 

Fracture Set Mean Orientation True Spacing (cm) [in] Mean 

Set 1 172°/76° 4.3 [1.69] 

Set 2 — — 

Set 3 353°/13° 6.8 [2.68] 

Set 4 332°/85° 3.64 [1.43] 

Set 5 022°/83° 2.75 [1.08] 
2-8 

Figure 2-6. A Modified Sneed and Folk Diagram Representation of Particle Shape 

(Sneed and Folk, 1958; Graham and Midgley, 2000). Sneed and Folk Diagrams Employ 

Ratios of the Three Orthogonal Particle Axes To Present Primary Particle Shape Data.
2-9 

All Plots

H : L

( L - W ) / ( L - H)

Figure 2-7. Modified Sneed and Folk Diagram of All Rubble Shape Data

All Plots Clast Data

3%

18%

48%

31%

0%

10%

20%

30%

40%

50%

60%

Cubic Plat y Bladed Elongat e

Shape Class

Percentage

Figure 2-8. Rubble Shape Major Classification by Percentage for All Rubble Shape Data. 

In This Chart, Cubic = Cubic; Platy = Cubic-Platy + Platy + Very Platy; Bladed = CubicBladed + Bladed + Very Bladed; Elongate = Cubic-Elongate + Elongate + Very Elongate.
2-10 

All Plots Clast Data

20%

15%

39%

26%

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

Cubic Plat y Bladed Elongat e

Shape Class

Percentage

Figure 2-9. Rubble Shape Major Classification by Percentage for All Rubble Shape Data. 

In This Chart, Cubic = Cubic + Cubic Platy + Cubic Elongate + Cubic Bladed; 

Platy = Platy + Very Platy; Bladed = Bladed + Very Bladed; 

Elongate = Elongate + Very Elongate.

All Plots Clast Data

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

Cubic CubicPlat yCubicBladedCubicElongat ePlat y Bladed Elongat e VeryPlatyVeryBladedVeryElongat e

Shape

Percentage

Figure 2-10. Rubble Shape Classification Detail by Percentage for All Rubble Shape Data
2-11 

Plot 1A 

Plot 1A rubble was collected from the talus pile located directly beneath the outcrop 

(Figure 2-11). Rubble fragments from this location are primarily bladed and elongate in shape 

(Figures 2-12 to 2-15). 

Figure 2-11. Field Photograph of Talus Pile Location for Plot 1A

Plot 1A

H : L

( L - W ) / ( L - H)

Figure 2-12. Modified Sneed and Folk Diagram of Plot 1A Rubble Shape Data
2-12 

Plot 1A

2%

17%

47%

35%

0%

10%

20%

30%

40%

50%

60%

Cubic Plat y Bladed Elongat e

Shape Class

Percentage

Figure 2-13. Rubble Shape Major Classification by Percentage for Plot 1A Rubble Shape 

Data. In This Chart, Cubic = Cubic; Platy = Cubic-Platy + Platy + Very Platy; 

Bladed = Cubic-Bladed + Bladed + Very Bladed; 

Elongate = Cubic-Elongate + Elongate + Very Elongate.

Plot 1A

18%

14%

40%

28%

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

Cubic Plat y Bladed Elongat e

Shape Class

Percentage

Figure 2-14. Rubble Shape Major Classification by Percentage for Plot 1A Rubble Shape 

Data. In This Chart, Cubic = Cubic + Cubic Platy + Cubic Elongate + Cubic Bladed; 

Platy = Platy + Very Platy; Bladed = Bladed + Very Bladed; 

Elongate = Elongate + Very Elongate.
2-13 

Plot 1A

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

Cubic CubicPlat yCubicBladedCubicElongat ePlat y Bladed Elongat e VeryPlatyVeryBladedVeryElongat e

Shape

Percentage

Figure 2-15. Rubble Shape Classification Detail by Percentage for Plot 1A Rubble 

Shape Data

Plot 2A 

Plot 2A rubble was extracted directly from the outcrop with minimal force to provide the most 

“pristine” rubble collection possible (Figure 2-16). Rubble fragments from this location are 

primarily bladed and elongate in shape (Figures 2-17 to 2-20). 

Figure 2-16. Field Photograph of Rubble Collection Area Plot 2
2-14 

Plot 2A

H : L

( L - W ) / ( L - H)

Figure 2-17. Modified Sneed and Folk Diagram of Plot 2A Rubble Shape Data

Plot 2A

3%

21%

47%

29%

0%

10%

20%

30%

40%

50%

60%

Cubic Plat y Bladed Elongat e

Shape Class

Percentage

Figure 2-18. Rubble Shape Major Classification by Percentage for Plot 2A Rubble Shape 

Data. In This Chart, Cubic = Cubic; Platy = Cubic-Platy + Platy + Very Platy; 

Bladed = Cubic-Bladed + Bladed + Very Bladed; 

Elongate = Cubic-Elongate + Elongate + Very Elongate.
2-15 

Plot 2A

21%

18%

37%

24%

0%

5%

10%

15%

20%

25%

30%

35%

40%

Cubic Plat y Bladed Elongat e

Shape Class

Percentage

Figure 2-19. Rubble Shape Major Classification by Percentage for Plot 2A Rubble Shape 

Data. In This Chart, Cubic = Cubic + Cubic Platy + Cubic Elongate + Cubic Bladed; 

Platy = Platy + Very Platy; Bladed = Bladed + Very Bladed; 

Elongate = Elongate + Very Elongate.

Plot 2A

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

Cubic CubicPlat yCubicBladedCubicElongat ePlat y Bladed Elongat e VeryPlatyVeryBladedVeryElongat e

Shape

Percentage

Figure 2-20. Rubble Shape Classification Detail by Percentage for Plot 2A Rubble 

Shape Data
2-16 

Plot 2B 

Plot 2B rubble was extracted directly from the outcrop with minimal force to provide the most 

“pristine” rubble collection possible. Plot 2B was located directly above Plot 2A. Rubble 

fragments from this location are primarily bladed and elongate in shape (Figures 2-21 to 2-24). 

Plot 2B

H : L

( L - W ) / ( L - H)

Figure 2-21. Modified Sneed and Folk Diagram of Plot 2B Rubble Shape Data

Plot 2B

2%

17%

54%

27%

0%

10%

20%

30%

40%

50%

60%

Cubic Plat y Bladed Elongat e

Shape Class

Percentage

Figure 2-22. Rubble Shape Major Classification by Percentage for Plot 2B Rubble Shape 

Data. In This Chart, Cubic = Cubic; Platy = Cubic-Platy + Platy + Very Platy; 

Bladed = Cubic-Bladed + Bladed + Very Bladed; 

Elongate = Cubic-Elongate + Elongate + Very Elongate.
2-17 

Plot 2B

19%

13%

44%

23%

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

50%

Cubic Plat y Bladed Elongat e

Shape Class

Percentage

Figure 2-23. Rubble Shape Major Classification by Percentage for Plot 2B Rubble Shape 

Data. In This Chart, Cubic = Cubic + Cubic Platy + Cubic Elongate + Cubic Bladed; 

Platy = Platy + Very Platy; Bladed = Bladed + Very Bladed; 

Elongate = Elongate + Very Elongate.

Plot 2B

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

Cubic CubicPlat yCubicBladedCubicElongat ePlat y Bladed Elongat e VeryPlatyVeryBladedVeryElongat e

Shape

Percentage

Figure 2-24. Rubble Shape Classification Detail by Percentage for Plot 2B Rubble 

Shape Data
2-18 

Plot 2C 

Plot 2C rubble was extracted directly from the outcrop with minimal force to provide the most 

“pristine” rubble collection possible. Plot 2C was located directly to the right (east) of Plot 2A. 

The rubble fragments from this subarea were measured in the field, but not collected as 

samples due to space limitations. Rubble fragments from this location are primarily bladed and 

elongate in shape (Figures 2-25 to 2-28). 

Plot 2C

H : L

( L - W ) / ( L - H)

Figure 2-25. Modified Sneed and Folk Diagram of Plot 2C Rubble Shape Data

Plot 2C

4%

20%

47%

29%

0%

10%

20%

30%

40%

50%

60%

Cubic Plat y Bladed Elongat e

Shape Class

Percentage

Figure 2-26. Rubble Shape Major Classification by Percentage for Plot 2C Rubble Shape 

Data. In This Chart, Cubic = Cubic; Platy = Cubic-Platy + Platy + Very Platy; 

Bladed = Cubic-Bladed + Bladed + Very Bladed; 

Elongate = Cubic-Elongate + Elongate + Very Elongate.
2-19 

Plot 2B

28%

15%

36%

22%

0%

5%

10%

15%

20%

25%

30%

35%

40%

Cubic Plat y Bladed Elongat e

Shape Class

Percentage

Figure 2-27. Rubble Shape Major Classification by Percentage for Plot 2C Rubble Shape 

Data. In This Chart, Cubic = Cubic + Cubic Platy + Cubic Elongate + Cubic Bladed; 

Platy = Platy + Very Platy; Bladed = Bladed + Very Bladed; 

Elongate = Elongate + Very Elongate.

Plot 2C

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

Cubic CubicPlat yCubicBladedCubicElongat ePlat y Bladed Elongat e VeryPlatyVeryBladedVeryElongat e

Shape

Percentage

Figure 2-28. Rubble Shape Classification Detail by Percentage for Plot 2C Rubble 

Shape Data
2-20 

Plot 3 

Plot 3 rubble was collected from the talus pile located directly beneath the outcrop 

(Figure 2-29). Rubble fragments from this location are primarily bladed and elongate in shape 

(Figures 2-30 to 2-33). 

Figure 2-29. Field Photograph of Talus Pile Location for Plot 3. Note That Higher 

Fracture Frequency at This Location Correlated With Smaller Rubble Clast Size.

Plot 3

H : L

( L - W ) / ( L - H)

Figure 2-30. Modified Sneed and Folk Diagram of Plot 3 Rubble Shape Data
2-21 

Plot 3

3%

17%

45%

35%

0%

10%

20%

30%

40%

50%

60%

Cubic Plat y Bladed Elongat e

Shape Class

Percentage

Figure 2-31. Rubble Shape Major Classification by Percentage for Plot 3 Rubble Shape 

Data. In This Chart, Cubic = Cubic; Platy = Cubic-Platy + Platy + Very Platy; 

Bladed = Cubic-Bladed + Bladed + Very Bladed; 

Elongate = Cubic-Elongate + Elongate + Very Elongate.

Plot 3

19%

14%

38%

29%

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

Cubic Plat y Bladed Elongat e

Shape Class

Percentage

Figure 2-32. Rubble Shape Major Classification by Percentage for Plot 3 Rubble Shape 

Data. In This Chart, Cubic = Cubic + Cubic Platy + Cubic Elongate + Cubic Bladed; 

Platy = Platy + Very Platy; Bladed = Bladed + Very Bladed; 

Elongate = Elongate + Very Elongate.
2-22 

Plot 3

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

Cubic CubicPlatyCubicBladedCubicElongat ePlat y Bladed Elongat e VeryPlatyVeryBladedVeryElongat e

Shape

Percentage

Figure 2-33. Rubble Shape Classification Detail by Percentage for Plot 3 Rubble 

Shape Data

2.3.2 Clast Size Distribution 

Rubble clast size (length, width, and height) was measured in the field. The majority 

(94 percent) of clast lengths (defined as the longest orthogonal dimension) were between 5 and 

20 cm [1.97 and 7.87 in] with 50 percent of the fragments measuring ≤ 11 cm [4.33 in] 

(Figures 2-34 and 2-35). Clast widths (Figures 2-34 and 2-35) in the intermediate orthogonal 

dimension primarily ranged between 3 and 15 cm [1.18 and 5.91 in] (96 percent) with half of the 

fragments ≤ 7.5 cm [2.95 in]. Heights (the shortest dimension; Figures 2-34 and 2-35) primarily 

ranged from 1 to 8 cm [0.39 to 3.15 in] (94 percent) with 50 percent ≤ 5 cm [1.97 in]. The 

majority (88 percent) of rubble clasts had volumes between 100 and 1,000 cm3

 [6.10 and 

61.02 in3

] (Figure 2-36), with the median volume ≤ 3,300 cm3 [201.38 in3] (Figure 2-37). 

Rubble size measurements are limited due to the data measurement methodology in the field. 

Specifically, the rubble measured in the field had a limited size range {0.5 cm [0.20 in] to a 

maximum of 65 cm [25.59 in]; Figure 2-34}. Additionally, all measurements were rounded to the 

nearest 0.5-cm [0.20-in] increment. This combines to produce a limited number of bins, both in 

absolute values {e.g., height values of 3.0 cm [1.18 in] occur most often; Figure 2-34} and in 

ratios (e.g., width/height ratios of 4:2, 6:3, and 10:5 are all equal to 2; Figure 2-38). There is 

also a (likely) human tendency to round to the nearest whole number increment, which can be 

seen in the data (e.g., Figure 2-34). Although size gradation curves were found to be relatively 

insensitive to maximum particle size (Pappas and Mark, 1993), the smallest particle sizes may 

be underrepresented in the rubble analyses. The size gradation curves for the Fran Ridge 

rubble, therefore, represent the range that was measured at the outcrop scale. Although the 

size distributions are generally similar, there are variations in the rubble size characteristics by 

plot (Figures 2-39 to 2-48). Plot 1, collected from the talus pile, has median length, width, and 

height values of 5, 8, and 12 cm [1.97, 3.15, and 4.72 in], respectively, with 50 percent of the 

rubble clast volume ≤ 2,329 cm3

 [142.12 in3]. Plot 2A, removed in situ, had the largest range of 

particle sizes {from 0.5 to 65 cm [0.20 to 25.59 in]}; the large clasts removed from Plot 2A 

contribute to the median volume for this outcrop at ≤ 13,629 cm3

 [831.69 in3]. Conversely, 

Plot 3 had overall smaller clast sizes {from 1 to 23 cm [0.39 to 9.06 in]}, with half of the sample 

≤344 cm3

 [20.99 in3]. This is likely due to smaller fracture spacing at Plot 3 (cf., Table 4 to 

Figure 2-47). 
2-23 

Figure 2-34. Frequency of Length (Longest Orthogonal Dimension) Measurements. 

All Clasts Measured Are Shown.

All Plots Clast Dimensions

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 10 20 30 40 50 60 70

Clast Size (cm)

Percentage

Length

Width

Height

Figure 2-35. Cumulative Frequency Distribution Plot of Rubble Clast Length, Width, and 

Height From All Plots
2-24 

Figure 2-36. Frequency of Clast Volume. Note That Volume Measurements Are 

Truncated at 4,000 cm3

 [244.09 in3] To Illustrate Smaller Values.

Figure 2-37. Cumulative Frequency Distribution Plot of Rubble Clast Volume From 

All Plots

All Plots Volume

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 10000 20000 30000 40000 50000 60000 70000 80000

Clast Volume (cm3

)

Percentage

Clast Volume

0

50

100

150

200

250

300

350

400

450

500

0 500 1000 1500 2000 2500 3000 3500 4000

Size (cm3)

Frequency
2-25 

1

2

3

4

5

6

13579

W/H

L/W

Figure 2-38. Plot of (Length/Width) Versus (Width/Height) Illustrates the Limited Binning 

Effect Described on Size Distributions. All Clasts Measured Are Shown.

Figure 2-39. Cumulative Frequency Distribution Plot of Rubble Clast Volume From Plot 1

Plot 1 Volume

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 5000 10000 15000 20000 25000 30000 35000

Clast Volume (cm3

)

Percentage
2-26 

Plot 1 Dimensions

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 10 20 30 40 50 60 70

Clast Size (cm)

Percentage

Length

Width

Height

Figure 2-40. Cumulative Frequency Distribution Plot of Rubble Clast Length, Width, and 

Height From Plot 1

Figure 2-41. Cumulative Frequency Distribution Plot of Rubble Clast Volume From 

Plot 2A

Plot 2A Volume

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 10000 20000 30000 40000 50000 60000 70000 80000

Clast Volume (cm3

)

Percentage
2-27 

Plot 2A Dimensions

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 10 20 30 40 50 60 70

Clast Size (cm)

Percentage

Length

Width

Height

Figure 2-42. Cumulative Frequency Distribution Plot of Rubble Clast Length, Width, and 

Height From Plot 2A

Figure 2-43. Cumulative Frequency Distribution Plot of Rubble Clast Volume From 

Plot 2B

Plot 2B Volume

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 5000 10000 15000 20000 25000

Clast Volume (cm3

)

Percentage
2-28 

Plot 2B Dimensions

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 10 20 30 40 50 60 70

Clast Size (cm)

Percentage

Length

Width

Height

Figure 2-44. Cumulative Frequency Distribution Plot of Rubble Clast Length, Width, and 

Height From Plot 2B

Figure 2-45. Cumulative Frequency Distribution Plot of Rubble Clast Volume From 

Plot 2C

Plot 2C Volume

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 5000 10000 15000 20000 25000

Clast Volume (cm3

)

Percentage
2-29 

Plot 2C Dimensions

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 10 20 30 40 50 60 70

Clast Size (cm)

Percentage

Length

Width

Height

Figure 2-46. Cumulative Frequency Distribution Plot of Rubble Clast Length, Width, and 

Height From Plot 2C

Figure 2-47. Cumulative Frequency Distribution Plot of Rubble Clast Volume From Plot 3

Plot 3 Volume

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 500 1000 1500 2000 2500 3000 3500

Clast Volume (cm3)

Percentage
2-30 

Plot 3 Dimensions

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 10 20 30 40 50 60 70

Clast Size (cm)

Percentage

Length

Width

Height

Figure 2-48. Cumulative Frequency Distribution Plot of Rubble Clast Length, Width, and 

Height From Plot 3 
3-1 

3 LABORATORY MEASUREMENT OF BULKING FACTOR 

3.1 Introduction 

Rubble obtained from the field investigation at Fran Ridge, described in Section 2, was shipped 

to the Center for Nuclear Waste Regulatory Analyses (CNWRA®) for further analyses. Planned 

laboratory tests were expected to provide further information on estimates of possible loose 

rubble mass densities (bulk density) that may occur in drifts constructed in the Topopah Spring 

welded lower lithophysal zone (Tptpll). Rubble from Plot 2 was used in the laboratory tests 

because of the closer link to in-situ rock mass densities compared to Plots 1 and 3. The rubble 

from Plot 2 was extracted directly from an outcrop with minimal force. The resulting rubble and 

the small percentage of fines were placed in two 0.2 m3

 [55-gal] drums at the field site. 

Approximately 0.3 m3

 [10.6 ft3] of rubble from Plot 2 subareas A and B, which included the void 

volume between rubble fragments in the drums, was shipped to CNWRA. The mass of rubble 

needed to fill wooden boxes with known dimensions was measured using a calibrated balance. 

The laboratory test was based on the procedure of Peele (1961, Section 2.4, Measurement of 

Bulking Factor). 

Results of laboratory packing experiments of the loose rubble are presented using two 

definitions of bulking factor. From a physical perspective, these definitions are the same. They 

differ in how the factor can be implemented in geological analyses or performance 

assessments. The two definitions of bulking factor are VB V or , where VB V −1 VB is the 

volume taken up by rubble and V is the volume taken up by intact rock. Because the mass of 

rock remains the same, the ratio of intact bulk density to rubble bulk density is the same as the 

ratio of the corresponding volumes. The volume increase is reflected as a porosity increase, 

which leads to increased permeability and decreased thermal conductivity for the rubble 

compared to that of the intact rock. Permeability and thermal conductivity of the rubble are not 

estimated as part of this report. An approach for estimating permeability and thermal 

conductivity using bulking factors and fracture data is described in Mohanty, et al. (2006). 

3.2 Bulk Density of Rubble 

Two wooden boxes were constructed to determine the mass density of loose rubble 

(Figure 3-1). The volume of each box was approximately 0.23 m3

 [8.1 ft3], and each could hold 

approximately 75 percent of the Plot 2 rubble sample sent to CNWRA. The box volume was 

chosen to minimize boundary effects associated with the box walls and so that different rubble 

fragments could be used in replicate packing of the boxes to investigate variability of the 

measurements. One box (Container 1) was 61.0 cm [2.0 ft] high by 61.0 cm [2.0 ft] wide by 

61.0 cm [2.0 ft] long and was cubic in shape. The other box (Container 2) was 61.0 cm [2.0 ft] 

high by 40.5 cm [1.325 ft] wide by 91.5 cm [3.0 ft] long and was rectangular in shape. The 

different shaped boxes have slightly different surface area to volume ratios, which could 

potentially affect measured loose rubble mass density. Much larger boxes, which would further 

minimize box boundary effects, could not be constructed, because of the limited available rubble 

volume. Given the rubble size distribution for Plot 2, subareas A and B (Figure 2-1), 

approximately 10 rubble fragments could fit in each direction within the boxes, except for 

possibly the shorter dimension of the rectangular box. Figure 3-1(B) shows one packing of the 

cubic box; the box dimensions are such that approximately 10 rubble fragments can fit into the 

box dimensions in each direction, which is a generally accepted approach for measuring mass 

per volume relationships of particles. 
3-2 

Before packing the boxes, all rubble from Plot 2 was removed from the drums and placed on a 

tarp according to size. When packing the boxes, staff tried to reproduce the size distribution of 

rubble observed on the tarp in the packed boxes using visual determination. Two box-packing 

approaches were used to obtain a range of loose rubble mass densities. In some packings, the 

open spaces between large rubble fragments were not filled with smaller rubble fragments. In 

other packings, smaller rubble fragments were placed in the larger openings to obtain a denser 

packing. In all packings, staff adjusted the orientation of the rubble fragments along the box 

walls to minimize boundary effects. 

In packings 1–4, there was no attempt to fill all larger openings between the rubble fragments 

with smaller sized rubble fragments. However, the packings were conducted such that no 

extraordinarily large openings or void spaces existed in the packed rubble. There was no 

attempt to pack the boxes as tightly or densely as possible. In packings 5–7, smaller sized 

rubble fragments were placed in larger openings/voids between the rubble fragments to produce 

a denser packing than in packings 1–4. A greater percentage of smaller fragments was used in 

packings 5–7 than what was observed on the tarp initially and was contained in packings 1–4. 

Openings/voids remained between the rubble fragments, however, but their size was not as 

large as may have existed in packings 1–4. The shape of the boxes did not appear to affect the 

measured, packed rubble mass density. 

The loose rubble bulk densities measured in packings 1–7 are shown in Table 3-1. The bulking 

factors were estimated based on an in-situ rock density of 1,979 kg/m3

 [123.5 lb/ft3] 

(Bechtel SAIC Company, LLC, 2003) for the Tptpll unit at Yucca Mountain, Nevada. A dry 

in-situ bulk density was used to estimate the bulking factor because the rubble fragments used 

in determining the rubble bulk densities were dry. 

Table 3-1 shows that the packing procedure yielded dissimilar loose rubble densities. 

Packings 1–4 were less dense than packings 5–7. The bulking factors calculated in Table 3-1 

are only estimates. They reflect the bulking factor before any settlement due to load or seismic 

events. The special care in packing fine particles in larger voids changes the magnitude of the 

rubble bulk density in a direction similar to increasing static load or shaking by earthquakes; 

however, no representation of these processes is otherwise implied by the packing method. 
3-3 

 (A) (B) 

(C)

Figure 3-1. Experimental Setup To Determine Mass Density of Packed 

Rubble (A) Container 1—Cubic Shape, (B) Top View of Container 1, and 

(C) Container 2—Rectangular Shape
3-4 

Table 3-1. Bulk Density of Rubble From Laboratory Measurements Assuming In-Situ

(Intact) Bulk Density of 1,979 kg/m3

 [124 lbs]. Definitions of Bulking Factor Use VB for the 

Rubble Volume and V for the Intact Rock Volume. 

Packing 

Number Container* 

Total Mass 

(kg)† 

Rubble 

Density 

(kg/m3

)‡ 

Bulking Factor (-) 

Using VB/V 

Definition 

Bulking Factor (%)

Using VB/V-1 

Definition 

1 1 244.05 1,080 1.83 83 

2 2 256.29 1,130 1.75 75 

3 1 257.12 1,130 1.75 75 

4 2 260.74 1,150 1.72 72 

5 1 284.34 1,250 1.58 58 

6 2 273.17 1,210 1.64 64 

7 1 276.32 1,220 1.62 62 

*Volume of Container 1 = 0.23 m3 [8.1 ft3]; Volume of Container 2 = 0.226 m3 [7.98 ft3] 

†1 kg = 2.2 lb 

‡1 kg/m3 = 0.062 lb/ft3
4-1 

4 SUMMARY 

Field data collected at surface exposures of the Tptpll at the south end of Fran Ridge provide 

additional information potentially relevant to conditions that could arise in the drifts of a 

high-level waste repository at Yucca Mountain. In general, the fracture data collected from the 

Topopah Springs welded lower lithophysal zone at the Fran Ridge outcrop are in good 

agreement with the fracture data collected in the exploratory drifts. The similarity of the fracture 

data, both in orientation and spacing, between the Fran Ridge outcrop and the small-scale 

fracture data in the ECRB lends confidence that the fracture and rubble clast data collected are 

of a comparable range. As observed in the field, rubble shape and size are strongly controlled 

by the fracture characteristics. The three primary fracture set orientations appear to contribute 

to the majority of rubble clasts being bladed or elongate in shape. At the drift scale, clast shape 

distribution is expected to remain consistent with the outcrop data because the fracture 

orientation data (the primary control on shape) are similar. Particle shape is an important 

component in determining bulking factor, with more angular fragments contributing to a higher 

bulking factor. The relationship between fracture spacing and rubble size distribution can be 

seen in the fracture/rubble characteristics of Plot 3 versus Plots 1 and 2. Rubble size 

distribution curves provide the range of particle sizes in the outcrop data and may help define 

appropriate size gradation estimates at the drift scale. The field data collection could not 

quantify the smallest particle sizes {>0.5 cm [0.20 in] fine-grained material} that may have been 

transported into or eroded away from the outcrop. The percentage of fines in a rubble pile will 

affect bulking factor, with a higher percentage producing a lower bulking factor. The 

supplementary information from the outcrop characterization, combined with knowledge from 

other sources (e.g., fracture analyses; Smart et al., 2006), may be used to further refine or 

constrain bulking factor estimates. Rock fragments from the field site were repacked in known 

volumes to estimate a rubble bulk density. Using a range of packing approaches, estimates of 

bulking factor ranged between 1.62 and 1.83. These values represent early time rubble piles, or 

the upper end of the range of long-term rubble piles that have experienced increased static 

loads and shaking by earthquakes. 
5-1 

5 REFERENCES 

Bechtel SAIC Company, LLC. “Subsurface Geotechnical Parameters.” 

Report 800–K0C–WIS0–00400–000–00A. Las Vegas, Nevada: Bechtel SAIC Company, LLC. 

2003. 

Day, W.C., R.P. Dickerson, C.J. Potter, D.S. Sweetkind, C.A. San Juan, R.M Drake II, and 

C.J. Fridrich. “Bedrock Geologic Map of the Yucca Mountain Area, Nye County, Nevada.” 

U.S. Geological Survey Geologic Investigations Series I-2627. 1998. 

Graham, D.J. and N.G. Midgley. “Graphical Representation of Particle Shape Using Triangular 

Diagrams.” Earth Surface Processes and Landforms. Vol. 25. pp. 1,473–1,477. 2000. 

Mohanty, S., A. Ghosh, and G. Adams. “Heat Transfer by Natural Convection Through 

Rubble Generated by Drift Degradation.” Proceedings Paper in the International 

High Level Radioactive Waste Management Conference, Las Vegas, Nevada, April 30–May 4, 

2006. La Grange Park, Illinois: American Nuclear Society. 2006. 

Pappas, D.M. and C. Mark. “Behavior of Simulated Longwall Gob Material.” Report of 

Investigations RI 9458. Washington, DC: U.S. Bureau of Mines. 1993. 

Peele, R. Mining Engineers’ Handbook. 3rd Edition. New York City, New York: 

John Wiley & Sons. 1961. 

Rockware, Inc. “StereoStat Version 1.4.” Golden, Colorado: Rockware, Inc. 2004. 

Smart, K. and R. Fedors. “Trip Report: Field Examination of Lithophysal Rocks at 

Yucca Mountain.” San Antonio, Texas: CNWRA. 2006. 

Smart, K.J., D.Y. Wyrick, P.S. Landis, and D.J. Waiting. “Summary and Analysis of Subsurface 

Fracture Data from the Topopah Spring Tuff Upper Lithophysal, Middle Nonlithophysal, Lower 

Lithophysal, and Lower Nonlithophysal Zones at Yucca Mountain, Nevada.” CNWRA 2005-04. 

ML060660009. San Antonio, Texas: CNWRA. 2006. 

Sneed, E.D. and R.L. Folk. “Pebbles in The Lower Colorado River, Texas, A Study of Particle 

Morphogenesis. Journal of Geology. Vol. 66, No. 2. pp. 114–150. 1958. 

Wyrick, D., R. Fedors, K. Smart, and R. McGinnis. “Trip Report: Field Examination of Fractures 

and Talus From Lithophysal Tuffs at a Rubble Analog Site, South End of Fran Ridge, 

Yucca Mountain, Nevada, February 5–8, 2007.” San Antonio, Texas: CNWRA. 2007.