LANDSLIDES OF THE CINCINNATI, OHIO, AREA

Contribution of Artesian Water to Progressive

Failure of the Upper Part of the Delhi Pike

Landslide Complex, Cincinnati, Ohio

U.S. GEOLOGICAL SURVEY BULLETIN 2059-D
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Contribution of Artesian Water to Progressive 

Failure of the Upper Part of the Delhi Pike 

Landslide Complex, Cincinnati, Ohio

By REX L. BAUM

LANDSLIDES OF THE CINCINNATI, OHIO, AREA

U.S. GEOLOGICAL SURVEY BULLETIN 2059-D

Analysis of saturated ground-water flow and slope 

stability of a landslide in thin colluvium to 

determine where failures probably began

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON :1994
U.S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY 

Robert M. Hirsch, Acting Director

For Sale by U.S. Geological Survey, Map Distribution

Box 25286, MS 306, Federal Center

Denver, CO 80225

Any use of trade, product, or firm names in this publication is for descriptive purposes only and 

does not imply endorsement by the U.S. Government

Library of Congress Cataloging-in-Publication Data

Baum, Rex L.

Contribution of artesian water to progressive failure of the upper part of the Delhi Pike 

landslide complex, Cincinnati, Ohio / by Rex L. Baum.

p. cm. (Landslides of the Cincinnati, Ohio, area ; D) 

(U.S. Geological Survey bulletin ; 2059)

Includes bibliographical references.

Supt. of Docs, no.: 119.3:2059-D

1. Landslides Ohio Cincinnati Region. 2. Colluvium Ohio Cincinnati 

Region. 3. Groundwater Ohio Cincinnati Region. I. Title. II. Series. III. Series: 

Landslides of the Cincinnati, Ohio, area ; ch. D. 

QE75.B9 no. 2059-D

557.3 s dc20 93-43886 

[551.3'07'0977178] CIP
CONTENTS

Abstract........................................................................................................................... Dl

Introduction..................................................................................................................... 1

Acknowledgments................................................................................................ 2

The Delhi Pike Landslide............................................................................................... 2

Model of Ground-Water Seepage................................................................................... 6

Results of the Ground-Water Model.................................................................... 9

Role of Artesian Water in the Failure of Colluvium at Delhi Pike ................................ 11

Conclusion...................................................................................................................... 13

References Cited............................................................................................................. 13

FIGURES

1. Map showing location of the Delhi Pike landslide complex..................................................................................... D3

2. Cross section of east wall of trench through lower part of Delhi Pike landslide...................................................... 4

3. Photograph showing icicles on the face of a quarry.................................................................................................. 5

4. Flow net showing directions of seepage in an infinite slope consisting of a permeable layer overlying less

permeable material.................................................................................................................................................... 6

5-7. Graphs and cross sections showing modeled distribution of hydraulic conductivity in the Delhi Pike landslide 

and the resulting pressure head at the slip surface, assuming:

5. High permeability in weathered bedrock and low permeability in unweathered bedrock ................................ 8

6. Increased permeability in the unweathered bedrock.......................................................................................... 9

7. Decreased permeability in the weathered bedrock............................................................................................. 10

8. Free-body diagram showing forces acting on an element or slice of a landslide...................................................... 11

9. Graphs showing local factor of safety, pressure head, slope of the slip surface, and depth to the slip surface

at the Delhi Pike landslide......................................................................................................................................... 12

TABLE

1. Factors of safety and height of water table under varying conditions in the Delhi Pike landslide........................... D6

III
IV CONTENTS

	LIST OF SYMBOLS

c' Residual cohesion for effective stress

D Vertical distance from ground surface to slip surface

E Resultant normal force acting on a vertical plane in a landslide

F Overall factor of safety

F' Initial local factor of safety

h Static head of water

/ze Amount of error in a computed solution to the ground-water flow equation due to an error in the boundary

	conditions

H Average distance from the water table to the failure surface measured normal to the slope

KI, K2 Hydraulic conductivities of isotropic layers of material shown in figure 4

Kx, Kz Hydraulic conductivity of materials in directions parallel to x and z Cartesian coordinates, respectively

p Pore pressure

Qxl- Qzb Total flux of water at the left-hand and basal boundaries of model

r Ratio of Qxl to Qzb

T Resultant shear force acting on a vertical plane in a landslide

t Average thickness of landslide debris, measured normal to the slope

jc, z Cartesian coordinates, horizontal and vertical, respectively

P Average slope angle, measured clockwise from the horizontal

Jt Unit weight of wet soil

Jw Unit weight of water

e An error in boundary conditions

9 Local slope of slip surface

AI, A/2 Angles measured from a line normal to the contact between materials to flow lines in figure 4

<5nn Normal stress acting on the slip surface

<5ns Shear stress acting on the slip surface

()>' Angle of residual friction for effective stress

\|/ Pressure head, p/jw
CONTRIBUTION OF ARTESIAN WATER TO

PROGRESSIVE FAILURE OF THE UPPER PART

OF THE DELHI PIKE LANDSLIDE COMPLEX,

CINCINNATI, OHIO

By Rex L. Baum1

ABSTRACT

Artesian water in bedrock beneath a colluvium-mantled 

slope can influence the stability of the slope, either by 

causing local failure that leads to progressive failure of the 

colluvium or by reducing the overall strength of the 

colluvium and causing failure. Artesian water under at least 

1.5 m of pressure head occurs in limestone layers of 

weathered shale and limestone bedrock at the Delhi Pike 

landslide complex in Cincinnati, Ohio. Colluvium, 1-2 m 

thick on the upper part of the slope, mantles the weathered 

bedrock. The colluvium slips on an undulating failure 

surface that coincides approximately with the top of the 

weathered bedrock. Several limestone layers are in contact 

with the colluvium near the failure surface.

A model of ground-water flow in ground beneath the 

slope, for saturated flow assumed to occur when the 

landslide is active, indicates that seepage in the colluvium is 

nearly horizontal near the contacts with the limestone beds, 

but seepage may have a strong downward component away 

from the contacts. Consequently, relative maxima in the 

distribution of pore pressure at the slip surface are near the 

limestone beds and relative minima occur along other parts 

of the failure surface.

Analysis indicates that artesian water flowing from the 

limestone beds has no significant effect on the overall 

stability of the thin colluvium at Delhi Pike, and plays only 

a minor role in determining the positions of initial local 

failures that lead to progressive failure. Stability analysis 

indicates that the overall factor of safety due to the pattern of 

ground-water flow determined by the model is approximately equal to the factor of safety due to slope-parallel 

seepage with the water table at the ground surface. The role

.S. Geological Survey, Box 25046, MS 966, Denver, CO 80225.

of the artesian water in determining the positions where local 

failures start was assessed by computing local factors of 

safety at many points along the failure surface. Positions of 

relative minima in the graph of local factors of safety 

coincide with locally steep parts of the slip surface. A few 

relative maxima of the pore pressure also coincide with 

positions of relative minima of the local factors of safety. 

However, the local slope of the developing slip surface 

appears to have an overriding influence on the positions of 

initial failures in slopes undergoing progressive failure.

INTRODUCTION

Artesian water in bedrock beneath colluvium-covered 

slopes is thought to be a major cause of landsliding in the 

colluvium (Zaruba and Mencl, 1982; Deere and Patton, 

1971). In humid climates, artesian water commonly occurs 

in horizontally layered shale alternating with permeable 

rock, such as sandstone or fractured limestone (Deere and 

Patton, 1971). Clay-rich colluvium that covers the layered 

bedrock has low permeability and impedes the flow of water 

out of the permeable bedrock layers. Consequently, high 

pore pressures can develop in the colluvium near the contact 

with the permeable bedrock layers and can contribute to 

sliding of the colluvium.

Artesian water beneath colluvium can contribute to 

failure of the colluvium by reducing the overall factor of 

safety; furthermore, it can contribute to progressive failure, 

the gradual growth in area of a slip surface from an initial, 

localized failure (Bishop, 1968), by reducing local factors of 

safety. The local factor of safety is the factor of safety on a 

small part of the potential failure surface; the overall factor 

of safety is an average factor of safety taken over the entire 

potential failure surface. The factor of safety against sliding 

is commonly defined as the ratio of available strength to the

Dl
D2 LANDSLIDES OF THE CINCINNATI, OHIO, AREA

strength mobilized along the slip surface (Morgenstern, 

1974). Analysis of the influence of artesian water on the 

local and overall factors of safety requires a detailed 

knowledge of the distribution of pore pressures along the slip 

surface.

An opportunity to investigate the role of artesian water 

in the failure of colluvium arose when artesian water was 

discovered in limestone layers of weathered shale and 

limestone bedrock beneath the Delhi Pike landslide complex 

near Cincinnati, Ohio (Fleming and others, 1981). During 

exploratory drilling, water flooded previously dry boreholes 

as the auger penetrated the first layer of limestone in the 

weathered shale and limestone bedrock beneath the 

landslide. A small-diameter standpipe was sealed into one of 

these layers, and measurements through the following year 

showed that water levels in the standpipe rose as much as 1.5 

m above the top of the limestone bed.

Several workers have modeled ground-water flow 

beneath slopes and analyzed its effect on slope stability. 

Hodge and Freeze (1977) analyzed some ground-water 

models that included confined permeable layers within 

weathering profiles. They determined that high pore 

pressures can occur near the toe of a slope in the confined 

layers, and that the high pore pressures can significantly 

reduce stability of a slope. Rulon and Freeze (1985) modeled 

steady, saturated and unsaturated seepage in horizontally 

layered, unconfined media beneath a hillside and showed 

that the distribution of pore pressure in their model produces 

a significantly higher factor of safety than the distributions 

commonly used in stability analyses. However, they did not 

analyze flow in layered media beneath slopes mantled by 

low-permeability colluvium. Wilson and Dietrich (1987) 

monitored ground water in a colluvium-filled hollow; they 

found that topography and heterogeneities in the hydraulic 

conductivity of bedrock beneath the colluvium determined 

the pattern of ground-water flow in bedrock, which, in turn, 

determined pore pressures in the colluvium. Iverson and 

Major (1986) clarified the roles of seepage direction and 

magnitude of the hydraulic gradient in the failure of long, 

uniform slopes. They found that, other things being equal, 

horizontal seepage is the most unstable condition if the 

friction angle of the soil is equal to the slope angle of the 

ground surface.

Progressive failure of slopes was an active field of 

research from the late 1960's through the 1970's; however, 

the influence of seepage on progressive failure has received 

little attention. The idea of progressive failure, meaning the 

gradual growth in area of a slip surface from an initial, 

localized failure, has existed for at least 40 years (Terzaghi 

and Peck, 1948, p. 91; Taylor, 1948, p. 342-343). Bjerrum 

(1967) proposed a conceptual model for progressive failure 

from a cut at the base of a long, uniform slope. Christian and 

Whitman (1969), Palmer and Rice (1973), and others 

subsequently analyzed Bjerrum's model and determined 

conditions that can cause a slip surface to propagate. Romani

and others (1972) analyzed progressive formation of 

rotational failures in slopes. Burland and others (1977) 

studied a field example of progressive failure due to 

excavation in a clay pit and observed evidence that a slip 

surface was propagating into a slope at the base of a cut. 

Much of the work on progressive failure has focused on 

progressive failure due to excavation, while neglecting any 

effects due to seepage.

I have modeled ground-water flow within the 

colluvium at part of the Delhi Pike landslide complex near 

Cincinnati, Ohio, and analyzed the role of artesian ground 

water in progressive failure of the colluvium. In sections that 

follow, I describe and analyze the physical characteristics of 

the landslide and materials beneath it that seem relevant to 

ground-water seepage and slope stability. These data are 

taken largely from Fleming and others (1981), supplemented 

by my own observations. Based on these observations, I 

formulate and use a model of ground-water flow to analyze 

possible seepage patterns. I then use pressure-head data 

from the ground-water model to compute local factors of 

safety, in order to study the influence of seepage on the 

locations of initial failures that lead to progressive failure of 

the slope.

ACKNOWLEDGMENTS

Robert Fleming (U.S. Geological Survey) and Arvid 

Johnson (Purdue University) shared data and observations 

from the Delhi Pike landslide.

THE DELHI PIKE LANDSLIDE

The Delhi Pike landslide is a thin translational slide that 

is part of a much larger landslide complex on a steep slope 

(fig. 1). The landslide complex is on the side of a ridge that 

is about 110 m high and several kilometers long. The 

complex extends for about 1 km along the side of the ridge 

and measures 100-200 m perpendicular to the ridge 

(Fleming and Johnson, 1994). The landslide complex 

consists of landslides as much as 2 m thick uphill from Delhi 

Pike and landslides as much as 5 m thick downhill from 

Delhi Pike. The Delhi Pike landslide was active during 

several years in the 1970's and has been studied by Fleming 

and others (1981). At the conclusion of their studies, they 

excavated a trench through the lower part of the Delhi Pike 

landslide (fig. 2). Data from the trench have been used in 

this analysis. The thickness of the landslide in the trench 

ranges from 0.3 to 1.8 m and averages 1.2 m. The ground 

surface undulates gently and has an average slope of 18.2°. 

The slip surface also undulates; its slope ranges from 0° to 

60°, and averages 18.7°.
CONTRIBUTION OF ARTESIAN WATER TO FAILURE, DELHI PIKE LANDSLIDE, CINCINNATI

4°45' 84°30' 84°15'

D3

39°15' -

39°00'

0 10 MILES

_J

0 5 10 KILOMETERS 

Figure 1. Location of the Delhi Pike landslide complex, Cincinnati, Ohio. (From Fleming and Johnson, 1994.)

Landslide debris at Delhi Pike consists of stony, clayey 

colluvium derived from weathered limestone and shale 

bedrock. The surface layer of the colluvium typically is a 

dark-brown silty clay, as much as 0.6 m thick. The lower 

layer of colluvium is a yellowish-brown to brown silty clay, 

1-2 m thick, containing pebble-, gravel-, and cobble-sized 

clasts of gray limestone. The upper part (soil B horizon) of 

the yellow-brown colluvium is formed into blocky peds, 0.5 

cm across, and free water fills fractures between the peds in 

the spring (Fleming and others, 1981). The ped structure 

diminishes with depth.

The base of the colluvium grades to weathered bedrock 

within a few centimeters. The slip surface generally occurs

at the top of the weathered bedrock, in a paper-thin layer of 

clay. Colluvium above the failure surface has a higher water 

content than weathered bedrock immediately below the slip 

surface. Measurements showed that colluvium immediately 

above the slip surface contained 27 percent water (based on 

dry weight) and the material beneath contained 19 percent 

water (Fleming and others, 1981, p. 550).

The weathered bedrock consists of fractured brown 

shale and jointed limestone beneath the colluvium. The shale 

is uncemented and traversed by many hairline fractures; it 

breaks into small blocky clasts, 2-10 cm across. Several 

beds of limestone from 0.1 to 0.3 m thick, separating beds of 

weathered shale from 0.1 to 3.0 m thick, are evident in the
D4 LANDSLIDES OF THE CINCINNATI, OHIO, AREA

65,20

Figure 2 (above and facing page). Cross section of east wall of trench through part of Delhi Pike landslide, Cincinnati, Ohio. Figure 

reduced from Fleming and Johnson (1994, pi. 1).

cross section (fig. 2). Vertical joints, from 0.1 to 0.4 m apart, 

break limestone beds into rectangular, triangular, or 

rhomboidal blocks. The joints are open 0-5 mm (Baum, 

1983). About 3-4 m beneath the ground surface (2-3 m 

below the contact with colluvium), the bedrock is relatively 

unweathered; fractures and joints are narrower than those 

near the surface, and ground-water seepage diminishes with 

depth. Bedding is almost horizontal; the regional dip of 

bedrock in the Cincinnati area is 1-2 m/km toward the 

northwest (Fleming and others, 1981, p. 543).

Ground-water flow beneath the slopes tends to 

concentrate in the colluvium and the upper part of the 

weathered bedrock (Robert W. Fleming, oral commun., 

1988). Water seeping from limestone layers in bedrock 

exposed at an abandoned quarry in western Cincinnati 

freezes into icicles on the face of the quarry during the winter 

(fig. 3). The largest volume of ice forms at the topmost layer 

of limestone in the weathered bedrock. The volume of ice 

diminishes rapidly at successively deeper layers so that the 

combined volume of ice on all lower layers of limestone is 

only a few percent of the volume on the topmost layer.

The concentration of ground-water flow in the 

colluvium and upper part of the weathered bedrock is consistent with a model of seepage in a sloping layer of relatively 

permeable material overlying less permeable material. 

Figure 4 shows a flow net for saturated ground-water flow 

beneath an infinite slope in which the water table is a short 

distance below the ground surface. The sloping layer has 

hydraulic conductivity K^ and the underlying material has

hydraulic conductivity K2, such that Kl=20K2. The ground 

surface and the interface between the materials slope 20°. 

Seepage is assumed to be vertical below the interface. 

Vertical seepage is a limiting case for saturated flow in this 

example, because seepage with a component to the left in 

figure 4 would indicate that the material became unsaturated 

at some depth below the interface. The orientation of flow 

lines above the interface is determined by the tangent law 

(Freeze and Cherry, 1979, p. 172-173):

tan 'kl=(Kl/K2) tan K2 

In applying the formula for the tangent law to figure 4, Xj 

and X2 are angles measured counterclockwise from a line 

normal to the interface to the flow lines in the materials 

having K^ and K2, respectively. In figure 4, the average 

slope angle, (3, is 20°, K{ /K2 = 20, X2 = 20°, and ^ = 82.2°. 

Increasing K] /K2 or K2 will make A,j approach 90°, so that 

flow above the interface will become more nearly parallel to 

the slope. The relatively close spacing of flow lines above 

the interface in figure 4 indicates that flow is concentrated 

above the interface.

Landslides in thin colluvium tend to be active in the 

early spring, from late March through early May (Fleming 

and others, 1981). Rapid, spectacular response of shallow 

ground water to spring rainstorms indicates that locally the 

entire thickness of the colluvium is nearly saturated during 

this time of year (Haneberg, 1989; Haneberg and Gokce, 

1994). For instance, the water level in a shallow boring rose
CONTRIBUTION OF ARTESIAN WATER TO FAILURE, DELHI PIKE LANDSLIDE, CINCINNATI D5

EXPLANATION

S:-BS§: Stony clay, dark-brown; pedologic soil formed on colluvium

Y Stony clay, yellow-brown; colluvium derived from subjacent 

bedrock. Contact with bedrock is transitional and locally 

obscure

Sh E Shale, yellow-brown to olive-gray, soft bedrock

En echelon open cracks indicating incipient shear failure 

on surface

Failure surface Continuous shiny surface containing striations. May also be a contact between different materials

Open crack with rough irregular surface that apparently 

formed in tension

Limestone fragment in colluvium 

Contact between different materials

Bottom of trench

Figure 3. Icicles on the face of a quarry in western Cincinnati, 

Ohio. The amount of ice diminishes with depth below the topmost 

limestone layer. (Photograph by R.W. Fleming.)

50 cm in response to 1.7 cm of rainfall (Fleming and others, 

1981, fig. 7). Such a large rise in water level is consistent 

with an unfilled porosity of no more than 3.4 percent (1.7 cm 

is 3.4 percent of 50 cm); thus, most of the void space must be 

filled with water. However, some borings remain dry during 

storms, and tensiometers indicate that some of the landslide 

debris remains unsaturated during storms (W.C. Haneberg, 

written commun., 1989).

Ground-water conditions in the Delhi Pike landslide 

were not observed at the time of failure, nor when the 

landslide was active, but data exist to constrain possible 

ground-water conditions at failure. Water levels and 

movement of the landslide were monitored for 5 yr during 

the 1980's by R.W. Fleming, A.6. Gokce, L. Murdock, and 

W.C. Haneberg. Their data indicate that the landslide debris 

did not become fully saturated (W.C. Haneberg, written 

commun., 1989) and did not move significantly during the 

time of monitoring. Stability analyses, based on residual 

strength of the landslide debris, as determined by laboratory 

tests and the well-known infinite-slope analysis (Lambe and 

Whitman, 1969, p. 352-356), indicate that the factor of
D6 LANDSLIDES OF THE CINCINNATI, OHIO, AREA

safety2 ranges from 0.63 to 1.21 (table 1) if the water table is 

at the ground surface and flow is parallel to the slope; it 

would be about 8 percent higher for flow like that shown in 

figure 4. The factor of safety is unity if flow is parallel to the 

slope and the water table is less than 0.95 m below the 

ground surface or if slightly artesian conditions exist (table 

1). Although the strength parameters vary considerably, 

these calculations indicate that the water table is probably 

near the ground surface when the landslide is active. Thus, 

a reasonable assumption about ground-water conditions in 

the landslide is that the water table is at the ground surface 

when the landslide is active.

MODEL OF GROUND-WATER 

SEEPAGE

I have made several assumptions in modeling groundwater flow at Delhi Pike:

Flow obeys Darcy's law. 

Flow is two dimensional. 

The porous medium is fully saturated and the top

flow line is at the ground surface. 

Flow is steady. 

Flux at the left and lower boundaries of the model is

known. 

Flow in fractured rock can be modeled as flow in an

equivalent porous medium.

Ground-water flow, subject to these assumptions, in a 

vertical, two-dimensional cross section of a heterogeneous, 

anisotropic, porous medium is governed by

a

(i)

In equation 1, x and z are the horizontal and vertical Cartesian coordinate directions, respectively; h is the hydraulic 

head, and Kx and KZ are principal components of the

hydraulic conductivity tensor. The principal axes of the 

conductivity tensor are assumed parallel to x and z. The 

head, h, is a measure of the potential of the fluid, and it has 

two main components, z and \j/,

(2)

2The factor of safety, F, is determined by the formula

c' + (tj -Hj ) cosptan<b'

F = - ^-a 

where c' is the residual cohesion for effective stress; <j>' is the residual 

friction angle for effective stress; P is the average slope angle; t is the 

average thickness of the landslide debris 0=1.2 m for the Delhi Pike 

landslide); H is the height of the water table above the slip surface, assuming 

slope-parallel flow; jt is the unit weight of saturated soil (jt was assumed to 

be 18.8 kN/m3); and v is the unit weight of water, 9.8 kN/m3 .

where \j/ is the pressure head and z is the elevation above an 

arbitrary datum (the .x-axis).

Equation 1 is solved subject to conditions of either 

specified head or specified flux at the boundaries of the 

problem domain. Head at the ground surface is set equal to 

the elevation of the ground surface, and flux across the other 

boundaries is specified in the model analyzed here. I have 

used finite differences on a square grid with the method of 

successive over-relaxation to solve the flow problem. Finite

EXPLANATION

 Contour of constant static head

 > Flow/line

Figure 4. Flow net showing directions of seepage in an infinite 

slope consisting of a permeable layer overlying less permeable 

material. The permeability, K^, of the overlying layer is 20 times 

the permeability of the underlying material, K2. Flow in the 

permeable layer is almost parallel to the slope (Xj=82.2c). Flow in 

the less permeable material is vertical downward (?i2=20°), a 

limiting case for saturated flow in this slope.

Table 1. Factors of safety and height of water table under varying 

conditions in the Delhi Pike landslide.

[Strength parameters from Fleming and Johnson (1994, table 3). Only those tests having c' less than 5.5 kN/m were used here; higher values of c' are inconsistent with the 

shallow failure surface of the Delhi Pike landslide]

Residual strength,

under effective stress Factor of 

safety, F, if

Cohesion, 

c' (kN/m2)

Angle of at ground 

friction, V surface

Height of water table 

in meters, if F=l

Above 

slip 

surface

Relative 

to ground 

surface

0

3

5

5.5

3

24° 

21° 

20° 

12° 

12.5C

0.63

.96

1.21

1.06

.73

0.55

1.11

1.64

1.42

.25

-0.65

-.09 

+ .44 

+ .22

-.95
CONTRIBUTION OF ARTESIAN WATER TO FAILURE, DELHI PIKE LANDSLIDE, CINCINNATI D7

difference formulas approximating equation 1 are found in 

Freeze and Cherry (1979, p. 181-185), and special formulas 

for the irregular boundary at the ground surface are in Smith 

(1985, p. 247-248).

Previously, I justified the assumption of total saturation 

with the water table at the ground surface; however, some of 

the other assumptions used in the model require some 

explanation.

In general, ground-water flow at Delhi Pike is not 

steady. Data of Fleming and others (1981, p. 551) indicate 

that shallow landslides are active during the times of rapid 

water-level rises associated with spring rainfall. I have used 

the assumption of steady flow to determine the pattern of 

seepage during times of highest water levels, which is the 

worst case for slope stability.

Flux across any given vertical or horizontal line in a 

slope is usually not known; thus, in designing models, 

regions of flow are commonly chosen that are much larger 

than the area of interest so that possible errors in the basal 

and lateral boundary conditions have a minimal effect on the 

results of the model (Hodge and Freeze, 1977, p. 468). This 

method of minimizing errors by modeling oversized regions 

of flow can be justified qualitatively by means of the 

principal of superposition and the properties of elliptic 

partial-differential equations. (See, for example, 

Weinberger, 1965; Kovach, 1984.) Let h represent the 

correct solution to equation 1 for a given set of boundary 

conditions, and let h£ represent the amount of error in a 

computed solution to equation 1 due to an error in the 

boundary conditions, e. The computed solution will be h+he. 

According to the maximum value theorem (Weinberger, 

1965, p. 55-57), I he \ < e |. If the error, e, is small compared to the true boundary values, then | h£ \«\ h and the 

computed solution will closely approximate the correct 

solution. Furthermore, the magnitude of he decreases with 

increasing distance from the boundary where the error exists 

(Kovach, 1984, figure 4.4-4, p. 177, or 4.4-6, p. 179). Thus, 

small errors in boundary conditions that are relatively far 

from the area of interest will have a very small effect on the 

solution for the area of interest.

Detailed data about the ground upslope and downslope 

from the trench shown in figure 2 are not available, so I put 

the left boundary of the model near the upper end of the 

trench. The lower end of the trench coincides with the toe of 

the landslide element within the larger landslide complex, 

and the basal boundary of the model is approximately at the 

elevation of the bottom-right side of the trench. I expect the 

model to yield relatively accurate results near the slip surface, except possibly near the head and toe, where the arbitrary left and lower boundaries of the model intersect the 

ground surface. The Delhi Pike landslide is shallow, so the 

slip surface is close to the ground surface in the model, and 

the geometry of the ground surface is well known. For saturated flow with the water table at the ground surface, the 

boundary conditions at the ground surface are accurately

known. Thus, the known boundary conditions at the ground 

surface should dominate the solution near the slip surface, 

except near the head and toe of the slope, where arbitrary 

boundaries of the model are close enough to influence the 

solution significantly.

The horizontal component of the hydraulic gradient at 

the left boundary of the model, {3/z(0,z)/3jt}, and the vertical 

component of the hydraulic gradient at the bottom boundary, 

{3/z(jt,0)/3z}, were set equal to constants. Thus, the flux 

across these boundaries varies in proportion to the hydraulic 

conductivity. Furthermore, the total flux at the left boundary, Qxl, and the total flux at the basal boundary, Qzb, were 

also constants. I varied the ratio of the fluxes, r,

r=(QxlIQzt) , (3)

in successive runs of the model to determine how sensitive 

the model was to the boundary conditions.

The boundary conditions used in the model would produce straight flow lines at some constant angle to the ground 

surface of a hill having a planar surface and consisting of an 

isotropic, homogeneous medium. The slope of the flow lines 

would depend on the ratio, r, in such a model. Topographic 

irregularities on the ground surface, and inhomogeneities 

and anisotropy within the slope, perturb the pattern of 

straight flow lines (Iverson and Major, 1986; Wilson and 

Dietrich, 1987).

The degree to which flow in fractured rock can be successfully modeled by an equivalent continuous medium is 

partly a matter of scale. For instance, rock containing many 

closely spaced, well-connected fractures can be successfully 

modeled as an equivalent continuous medium (Freeze and 

Cherry, 1979, p. 73). Fractures within the weathered bedrock at Delhi Pike have spacings on the order of centimeters 

to tens of centimeters and seem to be well connected. The 

slope being modeled has dimensions on the order of tens of 

meters, and nodal spacings in the model are 0.76 m. Thus, 

the spacing of fractures is small compared to the overall size 

of the model and individual units within the model, so I 

expect the representation of the fractured bedrock as an 

equivalent porous medium to yield acceptable results.

A possible distribution of hydraulic conductivity for the 

materials making up the slope is shown in the cross section 

in figure 5. In modeling steady flow, the ratios of conductivities between different materials are much more important 

than the actual values of the hydraulic conductivities. Thus, 

I have assigned conductivities to various materials in the 

slope on the basis of their permeabilities relative to the colluvium. The colluvium is assigned horizontal and vertical 

conductivities of l.OxlO"3 cm/s, on the basis of laboratory 

measurements by Fleming and others (1981). I assumed that 

weathered shale is 3-5 times more permeable than the colluvium, because it is highly fractured, and assigned Kx = 

5.0xlO-3 cm/s and K = 3.0xlQ-3 cm/s.
D8 LANDSLIDES OF THE CINCINNATI, OHIO, AREA

10 25 oc *-°

Ul IUl 9 S ^ 

Z

Q 1.5

LU

X 1

LU

OC

w 0.5 in

i i r T I T

,r=10

10 20 30 40 

HORIZONTAL DISTANCE IN METERS

50 60

Ground Surface

40 50 60

HORIZONTAL DISTANCE IN METERS 

EXPLANATION

Colluvium, 

KX=KZ=0.001 cm/s

Weathered shale, Kx=0.005 cm/s, 

Kz=0.003 cm/s

Unweathered shale and limestone, 

KX=KZ=0.000001 cm/s

Contour of constant head

Weathered shale and fractured 

limestone with conductivities 

(in cm/s) as follows:

Unit Kx

1 0.0127 0.00332

2 .0224 .00372

3 .0321 .00423

4 .0515 .00583

Figure 5. Modeled distribution of hydraulic conductivity in the Delhi Pike landslide and the resulting pressure head at the slip surface, 

assuming high permeability in weathered bedrock (shale) and low permeability in unweathered bedrock (limestone). The horizontal hydraulic gradient at the left boundary, 3/z/3jc, is -0. 1 183, and the vertical hydraulic gradient at the basal boundary, 3/z/3z, is 0.0529. Pressure-head 

distributions are projected based on three different ratios of influx at the left boundary to outflux at the basal boundary (r=l, r=2, r=10).

Fractured limestone was assigned a conductivity of 0.1 

cm/s, consistent with joint spacing of 0.1 m and average 

joint opening of 0.5 mm. (The conductivity of fractured 

rock can be estimated by means of equation 2.86 of Freeze 

and Cherry, 1979, p. 75). The limestone beds were 

assumed to be horizontal in the model. Individual beds 

within the weathered shale and fractured limestone unit in 

figure 5 are too thin to represent in the model, because the 

node spacing used was 0.76 m, and the thickest limestone 

bed is only 0.2 m, so average vertical and horizontal conductivities (Freeze and Cherry, 1979, p. 33-34) were 

assigned to the combined units based on the relative 

amounts of shale and limestone they contain. These

conductivities are listed in figure 5. Unweathered bedrock 

is assigned a conductivity of IxlO"6 cm/s in both the horizontal and vertical directions. Freeze and Cherry (1979, p. 

158) indicate that unweathered shale at depth generally has 

very low permeability. The upper limit of hydraulic conductivity for intact shale and limestone beds is much less 

than the assumed value of IxlO"6 cm/s (Freeze and Cherry, 

1979, p. 29); however, the assumed conductivity of 

unweathered bedrock is three orders of magnitude lower 

than the conductivity of the colluvium and weathered shale. 

Hence, the calculated flow in the unweathered bedrock is 

negligible, in accordance with field observations and the 

model in figure 4.
CONTRIBUTION OF ARTESIAN WATER TO FAILURE, DELHI PIKE LANDSLIDE, CINCINNATI D9

2.5

1.5

0.5

10 20 30 40 

HORIZONTAL DISTANCE IN METERS

50 60

Ground Surface

10 20 30 40 

HORIZONTAL DISTANCE IN METERS 

EXPLANATION

50

Colluvium, 

KX=KZ=0.001 cm/s

Weathered shale, Kx=0.005 cm/s, 

Kz=0.003 cm/s

Weathered shale and fractured 

limestone with conductivities (in 

cm/s) as follows:

Unit Kx

0.0127

.0224

.0321

.0515

0.00332

.00372

.00423

.00583

Unweathered shale, 

KX=KZ=0.000001 cm/s

Unweathered shale and fractured 

limestone with conductivities (in 

cm/s) as follows:

Unit Kx Kz ~

5 0.0010 0.00000111

6 .0020 .00000125

7 .0030 .00000143

8 .0050 .00000200

Figure 6. Modeled distribution of hydraulic conductivity in the Delhi Pike landslide and the resulting pressure head at the slip surface, 

showing the effect of increased permeability in the unweathered bedrock (limestone), relative to figure 5. The hydraulic gradient at the left 

boundary, 9Mk, is -0.056, and the hydraulic gradient at the basal boundary, dh/dz, is 0.0529. Only pressure-head distribution for r=l is 

shown, and it is almost identical to that shown in figure 5.

RESULTS OF THE GROUND-WATER 

MODEL

The cross section in figure 5 shows contours of equal 

head on a cross section through the Delhi Pike slope, and several inferences can be made from the contours about the pattern of flow. Seepage in the unweathered bedrock is roughly 

parallel to the mean slope, just as one would expect it to be 

near the middle of a long, uniform slope. A strong downward

component of seepage exists in colluvium and weathered 

bedrock near the top of the cross section, probably because 

the ground surface has a slight backslope and the flow is 

recharging a weathered limestone bed. Ground water flows 

downward above the middle and left parts of weathered limestone layers. Water in the weathered limestone beds is subject to about 1.5 m of pressure head (that is, the head in any 

given layer is about 1.5 m greater than the elevation of the 

layer). Flow is nearly horizontal (toward the ground surface)
DIG

£ 2.5

LLJ

ILLJ 9

^

Z

Q 1.5

<

LU

^ 1

LANDSLIDES OF THE CINCINNATI, OHIO, AREA

~i i i r

c/j 0.5 in

10 20 30 40 

HORIZONTAL DISTANCE IN METERS

50 60

Ground Surface

10

T I T

20 30 40

HORIZONTAL DISTANCE IN METERS

EXPLANATION

50 60

Colluvium, 

KX=KZ=0.001 cm/s

Weathered shale, 

KX=KZ=0.0001 cm/s

Unweathered shale and limestone, 

KX=KZ=0.000001 cm/s

Weathered shale and fractured 

limestone with conductivities 

(in cm/s) as follows:

Unit Kx

1 0.0101 0.000111

2 .0201 .000125

3 .0301 .000143

4 .0501 .000200

Figure 7. Modeled distribution of hydraulic conductivity in the Delhi Pike landslide and the resulting pressure head at the slip surface, 

showing the effect of decreased permeability in the weathered bedrock (shale), relative to figure 5. The hydraulic gradient at the left 

boundary, 3/z/3x, is zero, except in the weathered bedrock and colluvium, where it is -0. 150, and the hydraulic gradient at the basal boundary, 

3/z/3z, is 1.000, except in the weathered bedrock and colluvium, where it is 0.04606. Only pressure-head distribution for ^=1 is shown, and 

it is smoother than that shown in figure 5, but relative maxima and minima occupy the same positions.

in the limestone beds. Flow of the artesian water from the 

right ends of the weathered limestone layers through the colluvium either is horizontal or has a slight upward component.

The graph at the top of figure 5 shows the distribution 

of pressure head at the slip surface for the seepage pattern 

shown in the cross section below. The pore pressure at the 

slip surface was determined by interpolating linearly 

between nodes in the model that were immediately above 

and below the slip surface. Pressure head is converted to 

pore pressure by multiplying it by the unit weight of water, 

9.8 kN/m3 . Pressure head is relatively low at the ends and 

near the middle of the section, where seepage has a strong 

downward component. Pore pressures are locally elevated

near the ends of weathered limestone beds (fig. 5), where 

flow in the colluvium is horizontal or has an upward 

component.

Changing the ratio of fluxes at the two boundaries, r, 

changes the pressure head at the slip surface in the upper 

one-fourth of the model. Figure 5 shows pressure head at the 

slip surface for r=l, 2, and 10. Pressure head to the left of 

the 17-m mark is slightly greater for r=2 than for r=l. The 

average pressure head is only 2 percent greater for r=2 than 

for r=l. The pressure head for r=10, however, is significantly greater than that for r=l to the left of 17 m, and 

slightly greater between 17 and 27 m. The average pressure 

head is only 20 percent higher for r=10 than for r=l.
CONTRIBUTION OF ARTESIAN WATER TO FAILURE, DELHI PIKE LANDSLIDE, CINCINNATI Dll

The most reasonable choice for the boundary conditions used for this model is to let r equal 1. If r=l, any water 

that flows out of the slope at the ground surface, near a limestone layer, soaks back into the ground surface a short distance downslope. Letting r be greater than 1 forces more 

water to flow out of the slope at the ground surface than can 

soak back into the ground elsewhere and, thus, results in surface runoff. However, surface runoff has not been observed 

at Delhi Pike, even during heavy rainstorms (A.6. Gokce, 

oral commun., 1982).

Changing the distribution of permeability can change 

the distribution of pore pressure at the slip surface. However, 

the pressure-head distributions shown in figures 5 and 6 are 

almost identical, even though the horizontal permeability of 

unweathered bedrock is increased four orders of magnitude 

in figure 6, while all other permeabilities remain equal. 

Decreasing the permeability of the weathered shale, while 

holding the permeability of other materials constant, causes 

the pressure head in the limestone to change, and the peaks 

and valleys in the distribution of pore pressure along the slip 

surface change in magnitude but maintain their positions 

(fig. 7). Of course, if the permeability of the weathered shale 

is significantly less than the permeability of the colluvium, 

then the flow will be roughly parallel to the top of the weathered bedrock, as in figure 4. Pressure head in the weathered 

limestone beds, computed from the model in figure 5, ranges 

from 1.1 to 3.6 m and averages 2.0-2.5 m, somewhat higher 

than but consistent with the pressure head of 1.5 m reported 

by Fleming and others (1981). Thus, the distribution of permeabilities shown in figure 5 gives plausible results, and the 

distribution of pressure head shown by the r=l curve in figure 5 is my best estimate of the distribution of pressure head 

along the slip surface if the slope is fully saturated.

ROLE OF ARTESIAN WATER IN THE

FAILURE OF COLLUVIUM AT

DELHI PIKE

The distribution of pressure head from the model of 

ground-water flow (fig. 5) can be used to assess the role of 

ground water in the failure of the slope. Ground water can 

affect the overall factor of safety of a slope by reducing 

strength all along the potential failure surface. Furthermore, 

ground water can reduce strength preferentially in zones of 

high pore pressure (resulting from horizontal or upward 

seepage) along a potential slip surface. This preferential 

reduction of strength can influence the sequence of failure 

along a potential failure surface.

Artesian water from the limestone causes inconsequential reduction of the overall factor of safety; it is equivalent 

to the reduction of the overall factor of safety by theoretical 

slope-parallel flow. Ground-water flow in the slope (as 

modeled in fig. 5) has an effect on the overall factor of safety 

(as computed by the method of Janbu, 1973) approximately

Cns(?>x/cos 0)

 E+(dE/dx)8x 

 T+(dT/dx)5x

(8x/cos Q)

Figure 8. Free-body diagram showing forces acting on a slice of 

a landslide. The width of the slice is 8.x, the depth from the ground 

surface to the slip surface is D, and the weight (per unit width) is 

Dyfix. The local slope of the slip surface is determined by the angle 

6. The normal and shear stresses acting on the slip surface are Gnn 

and Gns, respectively. The horizontal (normal) resultant force 

acting on the surface of the slice is E, and the vertical (shear) 

resultant force acting on the surface of the slice is T.

equal to that of theoretical flow parallel to the mean slope, 

with the top flow line at the ground surface. Pore pressures 

due to slope-parallel flow are adequate to explain failure 

(table 1). The average of the modeled pore pressures is 98 

percent of the average of the pore pressures due to slopeparallel flow.

High pore pressure associated with artesian water can 

also influence progressive failure of a slope. Among the 

factors that can affect local factors of safety, three will be 

analyzed here: local depth, local pore pressure, and local 

slope of the potential failure surface. If the depth and slope 

of the potential failure surface were uniform, then it would 

be straightforward to assess the role of high pore pressure in 

failure of the slope at Delhi Pike, because areas of the slip 

surface where pressure head is relatively high would 

coincide with the positions of low local factors of safety and, 

therefore, initial failures. The depth and slope of the slip 

surface enter the problem because both are nonuniform at 

Delhi Pike. Strength enters the problem only indirectly, 

through its variation with depth, because the cohesion and 

coefficient of friction are assumed constants along the failure 

surface.

The initial local factor of safety (that is, the local factor 

of safety before any deformation occurs) can be computed 

by neglecting variation in the horizontal and vertical forces 

acting in the soil (fig. 8):

dE dT

(4)
D12

-0.7

LANDSLIDES OF THE CINCINNATI, OHIO, AREA

10 20 30 40 

HORIZONTAL DISTANCE IN METERS

HORIZONTAL DISTANCE IN METERS

HORIZONTAL DISTANCE IN METERS

HORIZONTAL DISTANCE IN METERS

Figure 9. Local factor of safety, pressure head, slope of the slip surface, and depth to the slip surface at the Delhi Pike landslide, compared to distance from the toe of the trench. The top three graphs are inverted so that conditions that tend to decrease the factor of safety 

(specifically, high pore pressure, steep inclines of the slip surface, and deep parts of the slip surface) are represented as relative minima. 

Except for this inversion, the distribution of pressure head shown here is identical to the r=l curve in figure 5. Minima in the local factor 

of safety coincide with the steepest parts of the slip surface.
CONTRIBUTION OF ARTESIAN WATER TO FAILURE, DELHI PIKE LANDSLIDE, CINCINNATI D13

In equation 4, E is the resultant normal force acting on a 

vertical plane passing through the landslide, and T is the 

resultant shear force acting on the same plane. Other forces 

that determine the vertical and horizontal equilibrium of a 

slice are the weight of the soil and the resultants of the 

normal and shear stresses acting on the slip surface. Thus, 

the forces considered in this analysis are the same as those 

in the ordinary method of slices (Lambe and Whitman, 

1969, p. 364). However, the analysis differs from other 

methods of stability analysis in that a factor of safety is 

computed for each slice, rather than summing the driving 

and resisting forces of all the slices and computing a factor 

of safety for the entire landslide. The initial, local factor of 

safety, F', is determined by a formula identical to the formula for the overall factor of safety in an infinite slope, 

except that the slope angle, 0, the pore pressure, p, and the 

depth of the failure surface, D, vary along the failure surface,

r =

tan(j)'

 + 

Z)yfsin0cos0 tanG

(5)

In equation 5, c' is cohesion for effective stress, ())' is the 

friction angle of the soil for effective stress, and jt is the 

total (wet) unit weight of soil. Equation 5 shows that F' 

decreases as D, p, and 0 increase.

The extent to which local thickness, slope, and pore 

pressure, combined, might have influenced the occurrence of 

initial, localized failures that led to progressive failure of the 

slope at Delhi Pike can be seen in figure 9. The local factor 

of safety (F'), slope of the slip surface (tan 0), depth to the 

failure surface (D), and pressure head (\|/), are graphed as 

functions of distance from the toe of the trench. Residual 

strengths were used in computing local factors of safety, but 

relative minima in the factor-of-safety graph represent the 

most likely sites of initial failures. The graphs of pressure 

head, slope, and depth are inverted in figure 9 so that 

conditions that tend to decrease the factor of safety 

(specifically, high pore pressure, steep inclines of the slip 

surface, and deep parts of the slip surface) are represented as 

relative minima in the graphs. Where relative minima in the 

graphs of pore pressure, slope, and depth coincide (as at 6, 

19, 38, and 49 m, for instance), the response in the factor-ofsafety graph is most pronounced. However, where the 

relative minima in these first three graphs are out of phase, 

their effects tend to ameliorate each other.

Local slope of the slip surface appears to have a 

stronger influence on the local factor of safety than pore 

pressure or thickness in the Delhi Pike landslide. Positions 

of both relative maxima and minima in the graphs of local 

factor of safety and local slope of the slip surface coincide 

almost exactly (fig. 9). However, positions of only a few of 

the local maxima and minima of pore pressure coincide with 

the maxima and minima of local factor of safety. The same

is true of local thickness. Thus, whatever determined the 

slope of the failure surface also determined the position of 

the initial failures. Apparently, artesian water played only a 

minor role in determining the locations of initial failures in 

the slope.

CONCLUSION

Although artesian ground water is generally thought to 

be a major cause of landslides in colluvium overlying 

horizontally bedded sedimentary rocks, analysis of the Delhi 

Pike landslide indicates that artesian water probably plays a 

minor role in initial failure of thin colluvium in the 

Cincinnati area. Places may exist where artesian water plays 

a significant role, such as some deep-seated failures in thick 

colluvium, but data needed to document such cases are 

unavailable. For the models used here, average pore 

pressure in the colluvium is no higher than would be 

expected for the commonly assumed slope-parallel flow 

with the water table at the ground surface. Thus, the overall 

factor of safety is no lower than it would be if the weathered 

and unweathered bedrock were homogeneous. A few areas 

of locally high pore pressure coincide with local minima of 

the factor of safety and steep parts of the failure surface. 

Positions of other local maxima of pore pressure coincide 

with local maxima of the factor of safety along relatively flat 

parts of the slip surface. Thus, high pore pressure associated 

with the artesian water probably contributed slightly to 

initial failures at a few points on the slip surface, but it cannot 

have determined the locations of initial failures to the extent 

it would have if the depth and slope of the slip surface were 

constants.

REFERENCES CITED

Baum, R.L., 1983, Engineering geology and relative slope stability 

in the area of the Fay Apartments and part of Mount Airy 

Forest: Cincinnati, Ohio, University of Cincinnati M.S. thesis, 

74 p.

Bishop, A.W., 1968, Progressive failure with special reference to 

the mechanism causing it: Proceedings of Geotechnical 

Conference, Oslo, Norway, 1967, v. 2, p. 142-150.

Bjerrum, Laurits, 1967, Progressive failure in slopes of overconsolidated plastic clay and clay shales: Proceedings of the 

American Society of Civil Engineers, v. 93, paper 5456, Journal of the Soil Mechanics and Foundations Division, no. SM5, 

p. 3^9.

Burland, J.B., Longworth, T.K., and Moore, J.F.A., 1977, A study 

of ground movement and progressive failure caused by a deep 

excavation in Oxford clay: Geotechnique, v. 27, no. 4, p. 

557-591.

Christian, J.T., and Whitman, R.V., 1969, A one-dimensional model for progressive failure: International Conference on Soil 

Mechanics and Foundation Engineering, 7th, Mexico City, 

1969, Proceedings, v. 2, p. 541-545.
D14 LANDSLIDES OF THE CINCINNATI, OHIO, AREA

Deere, D.U., and Patton, F.D., 1971, Slope stability in residual 

soils, in Proceedings of the Fourth Panamerican Conference on 

Soil Mechanics and Foundation Engineering, San Juan, Puerto 

Rico: American Society of Civil Engineers, State-of-the-Art 

Papers, v. 1, p. 87-170.

Fleming, R.W., and Johnson, A.M., 1994, Landslides in colluvium: 

U.S. Geological Survey Bulletin 2059-B, 24 p.

Fleming, R.W., Johnson, A.M., and Hough, J.E., 1981, Engineering 

geology of the Cincinnati area [field trip 18], in Roberts, T.G., 

ed., Geomorphology, hydrogeology, geoarcheology, engineering geology, v. 3 o/GSA Cincinnati '81-Field trip guidebooks: 

Falls Church, Va., American Geological Institute, p. 543-570.

Freeze, R.A. and Cherry, J.A., 1979, Groundwater: Englewood 

Cliffs, New Jersey, Prentice-Hall, 604 p.

Haneberg, W.C., 1989, Hydrology and drainage of a thin colluvium 

hillside in Delhi Township, Ohio: Cincinnati, Ohio, University 

of Cincinnati Ph.D. dissertation, 232 p.

Haneberg, W.C., and Gokce, A.O, 1994, Rapid water-level fluctuations in a thin colluvium landslide west of Cincinnati, Ohio: 

U.S. Geological Survey Bulletin 2059-C, 16 p.

Hodge, R.A.L., and Freeze, R.A., 1977, Groundwater flow systems 

and slope stability: Canadian Geotechnical Journal, v. 14, no. 

4, p. 466-416.

Iverson, R.M., and Major, J.J., 1986, Groundwater seepage vectors 

and the potential for hillslope failure and debris flow mobilization: Water Resources Research, v. 22, no. 11, p. 1543-1548.

Janbu, N., 1973, Slope stability computations, in Hirshfield, R.C., 

and Poulos, S.J., eds., Embankment-dam engineering 

Casagrande volume: New York, Wiley, p. 47-86.

Kovach, L.D., 1984, Boundary-value problems: Reading, Mass., 

Addison-Wesley, 419 p.

Lambe, T.W., and Whitman, R.V., 1969, Soil mechanics: New 

York, Wiley, 553 p.

Morgenstern, N.R., 1974, Methods of slope stability analysis, in 

Computer applications in foundation engineering and construction: American Society of Civil Engineers, Chicago Soil 

Mechanics Lectures, Geotechnical Engineering Division, 

Illinois Section, p. 44-68.

Palmer, A.C., and Rice, J.R., 1973, The growth of slip surfaces in 

the progressive failure of overconsolidated clay: Proceedings 

of the Royal Society of London, series A, v. 332, p. 527-548.

Romani, P., Lovell, C.W., Jr., and Harr, M.E., 1972, Influence of 

progressive failure on slope stability: American Society of 

Civil Engineers, Journal of the Soil Mechanics and 

Foundations Division, no. SM 11, p. 1209-1223.

Rulon, J.J., and Freeze, R.A., 1985, Multiple seepage faces on 

layered slopes and their implications for slope-stability 

analysis: Canadian Geotechnical Journal, v. 22, p. 347-356.

Smith, G.D., 1985, Numerical solution of partial differential 

equations Finite difference methods: New York, Oxford 

University Press, 337 p.

Taylor, D.W., 1948, Fundamentals of soil mechanics: New York, 

Wiley, 700 p.

Terzaghi, Karl, and Peck, R.B., 1948, Soil mechanics in 

engineering practice: New York, Wiley, 566 p.

Weinberger, H.F., 1965, A first course in partial differential 

equations with complex variables and transform methods: New 

York, Wiley, 446 p.

Wilson, C.J., and Dietrich, W.E., 1987, The contribution of bedrock 

ground-water flow to storm runoff and high pore-pressure 

development in hollows, in Erosion and sedimentation of the 

Pacific Rim: Proceedings, Corvallis Symposium, August 1987, 

International Association of Hydrological Sciences Publication 165, p. 49-59.

Zaruba, Quido, and Mencl, Vojtech, 1982, Landslides and their 

control: Developments in Geotechnical Engineering, v. 31, 

324 p.

Manuscript approved for publication October 19, 1993. 

Published in the Central Region, Denver, Colorado. 

Photocomposition by Mari L. Kauffmann. 

Graphics by Carol A. Quesenberry. 

Edited by Peter L. Martin.

Cover design by Arthur L. Isom, based on an original drawing by 

K.A. Richards, University of Cincinnati.

U.S. GOVERIWEOT PRINTING OFFICE: 1994-573-038/86026


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geology. Maps generally include brief texts; some maps include structure 

and columnar sections only.

Geophysical Investigations Maps are on topographic or planimetric bases at various scales, they show results of surveys using geophysical techniques, such as gravity, magnetic, seismic, or radioactivity, which 

reflect subsurface structures that are of economic or geologic significance. Many maps include correlations with the geology.

Miscellaneous Investigations Series Maps are on planimetric or 

topographic bases of regular and irregular areas at various scales; they 

present a wide variety of format and subject matter. The series also includes 7 1/2-minute quadrangle photogeologic maps on planimetric 

bases which show geology as interpreted from aerial photographs. The 

series also includes maps of Mars and the Moon.

Coal Investigations Maps are geologic maps on topographic or 

planimetric bases at various scales showing bedrock or surficial geology, 

stratigraphy, and structural relations in certain coal-resource areas.

Oil and Gas Investigations Charts show stratigraphic information for certain oil and gas fields and other areas having petroleum potential.

Miscellaneous Field Studies Maps are multicolor or black-andwhite maps on topographic or planimetric bases on quadrangle or irregular areas at various scales. Pre-1971 maps show bedrock geology in relation to specific mining or mineral-deposit problems; post-1971 maps 

are primarily black-and-white maps on various subjects such as environmental studies or wilderness mineral investigations.

Hydrologic Investigations Atlases are multicolored or black-andwhite maps on topographic or planimetric bases presenting a wide range 

of geohydrologic data of both regular and irregular areas; the principal 

scale is 1:24,000, and regional studies are at 1:250,000 scale or smaller.

Catalogs

Permanent catalogs, as well as some others, giving comprehensive 

listings of U.S. Geological Survey publications are available under the 

conditions indicated below from USGS Map Distribution, Box 25286, 

Building 810, Denver Federal Center, Denver, CO 80225. (See latest 

Price and Availability List.)

"Publications of the Geological Survey, 1879-1961" may be purchased by mail and over the counter in paperback book form and as a set 

microfiche.

"Publications of the Geological Survey, 1962-1970" may be purchased by mail and over the counter in paperback book form and as a set 

of microfiche.

"Publications of the U.S. Geological Survey, 1971-1981" may be 

purchased by mail and over the counter in paperback book form (two 

volumes, publications listing and index) and as a set of microfiche.

Supplements for 1982, 1983, 1984, 1985, 1986, and for subsequent years since the last permanent catalog may be purchased by mail 

and over the counter in paperback book form.

State catalogs, "List of U.S. Geological Survey Geologic and Water-Supply Reports and Maps For (State)," may be purchased by mail and 

over the counter in paperback booklet form only.

"Price and Availability List of U.S. Geological Survey Publications," issued annually, is available free of charge in paperback booklet 

form only.

Selected copies of a monthly catalog "New Publications of the 

U.S. Geological Survey" is available free of charge by mail or may be 

obtained over the counter in paperback booklet form only. Those wishing 

a free subscription to the monthly catalog "New Publications of the U.S. 

Geological Survey" should write to the U.S. Geological Survey, 582 National Center, Reston, VA 22092.

Note.-Prices of Government publications listed in older catalogs, 

announcements, and publications may be incorrect. Therefore, the prices 

charged may differ from the prices in catalogs, announcements, and publications.