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Rockery Design and Construction Guidelines

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FHWA-CFL/TD-06-006
November 2006
Federal Highway Administration
U.S. Department of Transportation

Central Federal Lands Highway Division 12300 West Dakota Avenue

Lakewood, CO 80228

Front Materials

report cover

Publication No. FHWA-CFL/TD-06-006
November 2006

Central Federal Lands Highway Division 12300 West Dakota Avenue
Lakewood, CO 80228

Logo: U.S. Department of Transportation Federal Highway Administration    Logo: Federal Lands Highway

Forward

The Federal Lands Highway (FLH) of the Federal Highway Administration (FHWA) promotes development and deployment of applied research and technology applicable to solving transportation-related issues on Federal lands. The FLH provides technology delivery, innovative solutions, recommended best practices, and related information and knowledge sharing to Federal agencies, Tribal governments, and other offices within the FHWA.

The objective of this study is to review existing analytical methods and construction techniques currently in use for design and construction of rockeries and to develop a unified framework for design and specification of rockeries in modem highway construction. The ultimate goal of the project is to provide designers, inspectors, and contractors with a basis for evaluating existing rockeries and specifying and constructing new rockeries.

James W. Keeley, P.E., Director of Project Delivery
Federal Highway Administration
Central Federal Lands Highway Division

James W. Keeley, P.E., Director of Project Delivery
Federal Highway Administration
Central Federal Lands Highway Division

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. This report does not constitute a standard, specification, or regulation.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document.

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

Technical Report Documentation Page

1. Report No.
FHWA-CFL/TD-06-006
2. Government Accession No. 3. Recipient's Catalog No.
4. Title and Subtitle
Rockery Design And Construction Guidelines
5. Report Date
November 2006
6. Performing Organization Code
7. Author(s)
Darren A. Mack, P.E., Steven H. Sanders, P.E., William L. Millhone, P.E., Renée L. Fippin, P.E., Drew G. Kennedy, P.G.
8. Performing Organization Report No.
9. Performing Organization Name and Address
Sanders & Associates Geostructural Engineering, Inc. (SAGE)
4180 Douglas Boulevard, Suite 100
Granite Bay, California 95746
10. Work Unit No. (TRAIS)
11. Contract or Grant No.
DTFH68-05-P-00120
12. Sponsoring Agency Name and Address
Federal Highway Administration
Central Federal Lands Highway Division 12300 W. Dakota Avenue, Suite 210
Lakewood, CO 80228
13. Type of Report and Period Covered

Final Report

April 2006 to November 2006

14. Sponsoring Agency Code
HFTS-16.4
15. Supplementary Notes
COTR: Khamis Haramy, FHWA-CFLHD; Advisory Panel Members: Scott Anderson, FHWA-FLH; Daniel Alzamora, FHWA-RC; Rich Barrows, FHWA-WFLHD; Khalid Mohamed, FHWA-EFLHD; and Roger Surdahl, FHWA-CFLHD. This project was funded under the FHWA Federal Lands Highway Technology Deployment Initiatives and Partnership Program (TDIPP).
16. Abstract
Rockeries consist of earth retaining and/or protection structures comprised of interlocking, dry-stacked rocks without mortar or steel reinforcement. They have been used for thousands of years and rely on the weight, size, and shape of individual rocks to provide overall stability. Some of the earliest rockeries constructed by the Federal Government date back to 1918. Within the private sector, commercially built rockeries have been constructed in the Pacific Northwest for at least the last four decades and in Northern California and Nevada for at least the last 10 years. As rockery design procedures tend to vary regionally, studies were performed to determine the methods by which rockeries are designed and constructed in various regions throughout the western United States. These design methods were then compared using several typical rockery design loading conditions to determine how the resulting rockery designs differ and which methods are most appropriate for a proposed design for the FHWA's FLH Divisions. Based on the research performed, a rational design methodology, which evaluates rockery stability as a function of the rockery geometry (height, base width, and batter), rock properties and placement, and lateral pressure imposed by the backfill materials, was developed. A sample design problem is included. Recommendations for specifying and constructing rockeries that are consistent with the design methodology are also provided.
17. Key Words
ROCKERY, ROCKERIES, EARTH RETENTION, ROCK WALLS, LATERAL EARTH PRESSURE, GEOPHYSICAL EVALUATION METHODS
18. Distribution Statement
No restriction. This document is available to the public from the sponsoring agency at the website http://www.cflhd.gov.
19. Security Classif. (of this report)
Unclassified
20. Security Classif. (of this page)
Unclassified
21. No. of Pages
178
22. Price

Form DOT F 1700.7 (8-72)
Reproduction of completed page authorized

SI* (Modern Metric) Conversion Factors

APPROXIMATE CONVERSIONS TO SI UNITS
Symbol When You Know Multiply By To Find Symbol
LENGTH
in inches 25.4 millimeters mm
ft feet 0.305 meters m
yd yards 0.914 meters m
mi miles 1.61 kilometers km
AREA
in2 square inches 645.2 square millimeters mm2
ft2 square feet 0.093 square meters m2
yd2 square yard 0.836 square meters m2
ac acres 0.405 hectares ha
mi2 square miles 2.59 square kilometers km2
VOLUME
fl oz fluid ounces 29.57 milliliters mL
gal gallons 3.785 liters L
ft3 cubic feet 0.028 cubic meters m3
yd3 cubic yards 0.765 cubic meters

NOTE: volumes greater than 1000 L shall be shown in m3

m3
MASS
oz ounces 28.35 grams g
lb pounds 0.454 kilograms kg
T short tons (2000 lb) 0.907 megagrams (or "metric ton") Mg (or "t")
TEMPERATURE (exact degrees)
°F Fahrenheit 5 (F-32)/9 or (F-32)/1.8 Celsius °C
ILLUMINATION
fc foot-candles 10.76 lux lx
fl foot-Lamberts 3.426 candela/m2 cd/m2
FORCE and PRESSURE or STRESS
lbf poundforce 4.45 newtons N
lbf/in2 poundforce per square inch 6.89 kilopascals kPa
APPROXIMATE CONVERSIONS FROM SI UNITS
Symbol When You Know Multiply By To Find Symbol
LENGTH
mm millimeters 0.039 inches in
m meters 3.28 feet ft
m meters 1.09 yards yd
km kilometers 0.621 miles mi
AREA
mm2 square millimeters 0.0016 square inches in2
m2 square meters 10.764 square feet ft2
m2 square meters 1.195 square yards yd2
ha hectares 2.47 acres ac
km2 square kilometers 0.386 square miles mi2
VOLUME
mL milliliters 0.034 fluid ounces fl oz
L liters 0.264 gallons gal
m3 cubic meters 35.314 cubic feet ft3
m3 cubic meters 1.307 cubic yards yd3
MASS
g grams 0.035 ounces oz
kg kilograms 2.202 pounds lb
Mg (or "t") megagrams (or "metric ton") 1.103 short tons (2000 lb) T
TEMPERATURE (exact degrees)
°C Celsius 1.8C+32 Fahrenheit °F
      ILLUMINATION  
lx lux 0.0929 foot-candles fc
cd/m2 candela/m2 0.2919 foot-Lamberts fl
      FORCE and PRESSURE or STRESS  
N newtons 0.225 poundforce lbf
kPa kilopascals 0.145 poundforce per square inch lbf/in2

*SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380. (Revised March 2003)

TABLE OF CONTENTS

LIST OF ABBREVIATIONS, ACRONYMS, AND SYMBOLS

A - Acceleration Coefficient per AASHTO Division I-A, Section 3

A* - Amplified peak acceleration

Aa, Av - Acceleration coefficients per ATC-3-06

AASHTO - American Association of State Highway Transportation Officials

A.D. - Latin, Anno Domini, current calendar epoch

AOS - Apparent Opening Size

apeak - Peak spectral acceleration, gravity (g)

ARC - Associated Rockery Contractors

ASTM - American Society of Testing and Materials

ATC - Applied Technology Council

B - Base rock width, m

BMP - "Best Management Practices" as related to site erosion, sediment, and runoff control and reduction

c, c' - Total and effective soil cohesion values, respectively, in kPa. Although effective stresses are most typically used, the term "c" is commonly used throughout this report.

ca. - Latin, circa, meaning "about" for dates that are approximately known

CalTrans - State of California, Department of Transportation

cF, c'F - Total and effective soil cohesion values in the foundation soil, in kPa

CFLHD - Central Federal Lands Highway Division

CIE - Seismic inertial coefficient

CO - Contracting Officer

d - Depth of soil to neglect when computing passive resisting force, μ dpeak - Peak spectral displacement, cm

Dpeak - Embedment depth at toe of rockery, m

D* - Amplified peak displacement

e - Moment eccentricity relative to center of base rock, m

es - Moment eccentricity relative to center of base rock due to seismic forces, m

EFP - Equivalent fluid pressure applied by soil, kN/m3

EPA - Effective peak acceleration, g

EPV - Effective peak velocity, cm/s

FA - Active earth pressure force acting on the back of the rockery

FA,H - Horizontal component of active earth pressure force kN (per meter of rockery)

FA,V - Vertical component of active earth pressure force, kN (per meter of rockery)

FAE - Total static plus seismic thrust acting on rockery, kN (per meter of rockery)

ΔFAE - Incremental seismic thrust acting on rockery, kN (per meter of rockery)

FH - Sum of static horizontal driving forces acting on rockery, kN (per meter of rockery)

FH,S - Sum of static and seismic horizontal driving forces acting on rockery, kN (per meter of rockery)

FHWA - Federal Highway Administration

FLH - Federal Lands Highway

Foundation Fill - Material conforming to Section 704.01 of the FHWA Standard Specifications (FP-03)

Fp - Passive resisting force on toe of rockery, kN (per meter of rockery)

Fs - Horizontal resultant force due to application of vertical surcharge load, kN (per meter of rockery)

Fμ - Static resisting friction force of bottom of base rock, kN (per meter of rockery)

Fμ,S - Static and seismic resisting friction force of bottom of base rock, kN (per meter of rockery)

FS - Factor of safety

FSBC - Factor of safety with respect to bearing capacity

FSOT - Factor of safety with respect to external overturning

FSOT_INT - Factor of safety with respect to internal (inter-rock) overturning

FSseismic - Factor of safety with respect to required rockery weight to limit rockery displacement to Δ or less

FSSL - Factor of safety with respect to base sliding

GPR - Ground penetrating radar, a type of geophysical evaluation method

H - Rockery height, m

H/B - Height-to-base-width ratio

HDPE - High density polyethylene, usually referring to a type of plastic pipe

HEC - Hydraulic Engineering Circular

HP - Ultraseismic Horizontal Profiling Method, a type of geophysical surface wave method

i - Slope inclination, measured up from horizontal, per A. J. Hendron, Jr., methodology

IR - Impulse Response, a type of geophysical surface wave method

KA - Coefficient of active earth pressure

KAE - Lateral earth coefficient for computation of static plus seismic thrust force

kh - Horizontal seismic coefficient

Kp - Coefficient of passive earth pressure

kv - Vertical seismic coefficient

LTDS - Long term design strength of geogrid reinforcement

MARV - Minimum Average Roll Values

Mo - External overturning moment about toe of rockery imposed by lateral earth pressure (horizontal component) and surcharge loads, kN - μ (per meter of rockery)

Mo,s - External overturning moment due to static and seismic loads, kN - μ (per meter of rockery)

Mo_int - Internal (inter-rock) overturning moment about toe of intermediate rock imposed by lateral earth pressure (horizontal component) and surcharge loads, kN - μ (per meter of rockery)

Mr - External resisting moment about toe of rockery imposed by rockery weight, lateral earth pressure (vertical component), and passive pressure, kN - μ (per meter of rockery)

Mr,s - External resisting moment about toe of rockery imposed by rockery weight and vertical components of static and seismic lateral earth pressures kN - μ (per meter of rockery)

Mr_int - Internal resisting moment about toe of intermediate rock imposed by partial rockery weight, lateral earth pressure (vertical component), and passive pressure, kN - μ (per meter of rockery)

MSE - Mechanically stabilized earth or embankment

OSHA - Occupational Safety and Health Administration

PCR - Poorly constructed rockery as defined by A. J. Hendron, Jr.

PGA - Peak ground acceleration, g

PS - Parallel Seismic, a type of geophysical cross-hole logging method

PVC - Polyvinyl chloride, a type of plastic pipe

qmax - Maximum applied bearing pressure at toe of base rock due to moment eccentricity, kPa

qmax,s - Maximum applied bearing pressure at toe of base rock due to moment eccentricity under seismic loading, kPa

qs - Vertical surcharge pressure acting on the ground surface behind the rockery, kPa

RSP - Rock slope protection, e.g., riprap

RSS - Reinforced soil slope

SAGE - Sanders & Associates Geostructural Engineering, Inc.

SE - Sonic Echo, a type of geophysical surface wave method

Ta - Allowable tensile strength for geotextile soil reinforcement, equal to LTDS/FS

UBC - Uniform Building Code

U.S. - United States

UV - Ultraviolet light, such as sunlight

vpeak - Peak spectral velocity, cm/sec

V* - Amplified peak velocity

W - Total weight of rockery (unit width basis), kg

WCR - Well-constructed rockery as defined by A. J. Hendron, Jr.

Wi - Weight of rockery component (unit width basis), kg

xi - Moment arm from toe of rockery to centroid of mass for rockery component, m

z - Point of application of FAE, measured vertically from base of rockery, m

Δ - Tolerable rockery displacement for Richards and Elms analysis, in

ΔFAE - Incremental seismic thrust acting on rockery, kN (per meter of rockery)

α - Angle, measured up from the horizontal, to the back cut or rear face of rockery, degrees. Positive angle is defined as face of back cut sloping up and away from the base of the rockery, starting from the bottom of the cut.

αA, αV, αD - Newmark and Hall amplification factors

β - Retained ground surface inclination ("backslope"), degrees. Positive angle if slope increases in height with increasing distance from the back of the rockery.

δ - Interface friction angle between retained soil and back of rockery/crushed rock backfill zone, degrees

φ, φ' - Total and effective soil friction angle / angle of internal friction, respectively. Although effective stresses are most typically used, the term "f" is commonly used throughout this report.

φCR - Friction angle (effective or total) of crushed rock backfill

φF - Friction angle (effective or total) of foundation soil and soil at toe of rockery

γ, γs - Density of retained soil, kN/m3

γCR - Density of crushed rock backfill (net density, including voids), kN/m3

γR - Density of rockery facing (net density, including voids), kN/m3

γF - Density of foundation soil, kN/m3

μ - Friction factor for sliding

ψ - Back cut inclination, degrees

 

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