Borehole, surface geologic, and geotechnical data for 

the Aspen Grove landslide, Sanpete County, Utah 

Rex L. Baum and Robert W. Fleming 

U.S. Geological Survey Open-File Report 01-413 

This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial 

standards nor with the North American Stratigraphic Code. Any use of trade names in this publication is 

for descriptive purposes only and does not imply endorsement by the U.S. Government. 

2001 

U.S. Department of the Interior 

U.S. Geological Survey 

1

Introduction

The Aspen Grove landslide, in Ephraim Canyon,

Sanpete County, Utah (fig. 1) was active from 1983

through 1987 and was the subject of field investigations

from 1983-1986. Previous reports included some of the

borehole, geologic, and geotechnical data collected as

part of these investigations but many of the data have not

previously been published (Baum, 1988; Baum and others, 1988; Baum and Fleming, 1989; Fleming and

Johnson, 1989; Baum and others, 1993; Baum and Reid,

2000). Plans to pave Utah State Highway 29, which

crosses the landslide in two places, has led to a recent

request to make these data available. This report includes

a geologic description of the landslide and its immediate

surrounding area, borehole logs, piezometric observations, and laboratory data from the landslide. 

Topographic and Geologic Setting

The head of the Aspen Grove landslide is at about

2,423 m (about 7,950 ft) altitude in an assemblage of

spruce, fir, aspen, and maple (fig. 1). The toe is at about

2,240 m (about 7,350 ft) altitude in an assemblage of

scrub oak and sagebrush. Grasses and shrubs cover the

ground surface, and boulders of sandstone jut out of the

ground.

Map

location

Utah

19 

21 

North 0 1000 feet

0 300 meters

Contour interval, 25 feet

7600

7700

7800

7800

7900

7900

8000

7700

7600

Flagstaff limestone, generally blanketed by 0.5-2 m of weatherred 

residuum.

Landslide deposits and colluvium that predate the Aspen Grove landslide

Tf

Tf

Tf

Tf

Tf

Ql1

Ql1

Ql1

Ql1

Ql1

Ql1

Ql2

Ql2

Landslide deposits of the Aspen Grove landslide

Ql1

Tf

Ql2

Approximate area

shown in Figure 2

Explanation of Map Units

Ql1

Internal toe

Figure 1. Simplified geologic

map of the Aspen Grove

landslide and vicinity.

Topographic base compiled

by Diana Fair, USGS geologic plotter lab, from aerial

photography of 14 June1983.

2
The slope of the ground in the vicinity of the landslide 

ranges from 0° to 31° and averages about 11°. The 

ground slopes generally toward the west. Superimposed 

on the westerly slope of the area are plunging ridges and 

troughs in the ground surface that trend west or northwest (fig. 1). The ridges are 100 to 200 m wide and hundreds of meters long. The troughs are of the same length, 

but are about half as wide as the ridges. Relief on the 

troughs and ridges is about 10 to 50 m. The troughs and 

ridges result from relief on the surface of the bedrock, 

because bedrock crops out at the crests of many of the 

ridges. The trend of the troughs and ridges is oblique to 

the strike of the bedrock. 

Bedrock 

Bedrock in the area consists of bedded limestone, limy sandstone, and shale of the Cove Mountain and 

Musina Peak Members of the Flagstaff Limestone 

(Stanley and Collinson, 1979), and sandstone and shale 

of the North Horn Formation. Figure 1 shows the distribution of bedrock formations and surficial deposits near 

the slide (see also Plate 1 of Baum and Fleming, 1989). 

The Flagstaff Limestone underlies ground in the vicinity 

of the Aspen Grove landslide, and the North Horn 

Formation underlies an escarpment east of the landslide. 

Limestone of the Cove Mountain Member of the 

Flagstaff Limestone is white or gray, porous, and lacks 

fossils. Some brown chert occurs with the limestone. 

Limestone of the Musina Peak Member contains abundant mollusk fossils and is white or gray and finegrained. Some of the limestone is silicified. Sandstone 

occurs only in the Cove Mountain Member; it is white or 

light gray and moderately indurated. The sandstone consists of fine- to medium-grained, pink and white quartz 

sand with calcite cement. Shale in both members is compact and gray, white, brown, or red claystone. 

The North Horn Formation southeast of the landslide 

consists of 1- to 3-m-thick beds of ledge-forming sandstone, alternating with beds of claystone and a few 0.1-

to 0.3-m-thick beds of limestone. The sandstone is light 

gray or light yellow, massive or cross laminated, and 

consists of quartz sand mixed with a few chert granules 

and cemented by silica. The claystone is red, brown, 

orange, or gray, massive and silty. The limestone is medium- to dark-gray, and fossiliferous. 

The bedding in the Flagstaff Formation, which underlies the area of Aspen Grove landslide, dips about 20° 

toward the west. The structures in the area include a fault 

at the foot of the escarpment (east of Aspen Grove, see 

Baum and Fleming, 1989). The fault dips steeply toward 

the west and trends about N. 10° E. Beds of the Flagstaff 

Limestone, west of the fault, are down relative to beds of 

the North Horn Formation, east of the fault. The North 

Horn beds are about horizontal. Another fault is in 

Flagstaff Limestone, near the presumed terminus of the 

Aspen Grove landslide. The fault trends about due north 

and dips steeply or is vertical. Beds are down on the east 

side of the fault. 

Residuum 

The area of the Aspen Grove landslide is blanketed by 

weathered residuum in some places and by colluvium or landslide debris in others. The residuum is material derived from the underlying bedrock of the Flagstaff 

Limestone by weathering essentially in place. It is generally 0.5 to 2 m thick. The residuum is predominantly 

clay, and contains abundant pebble-, cobble-, and boulder-sized clasts. The clasts include white or gray limestone; white, silicified, fossiliferous limestone; white or 

gray limy sandstone; and light gray, red, or green claystone.1 

Landslide Debris 

The matrix of the landslide debris in the area of the Aspen Grove landslide consists of yellow or brown, 

sandy clay and contains abundant boulders and blocks of 

cross-laminated yellow and light-gray sandstone derived 

from the North Horn Formation. The sandstone boulders 

and blocks in the landslide debris consist of fine- to 

medium-grained, moderately sorted quartz sand with 

granules and pebbles of white chert. The sandstone has 

silica cement and does not effervesce in acid as does the 

limy sandstone found in the residuum. The landslide 

debris also contains some clasts of limestone and claystone derived from the Flagstaff Limestone. The nearest 

outcropping of the North Horn Formation and probable 

source area of the landslide debris at Aspen Grove is 

about 200 to 300 m east-southeast of the head of the 

Aspen Grove landslide (Baum and Fleming, 1989, plate 

1). The landslide debris is 6 to 8 m thick in the upper 

half of the landslide and may be thicker in the foot area 

below the lower road crossing. 

1South of Aspen Grove, the residuum contains clasts of claystone and white or gray limestone. Fine- to medium-grained, 

white, limy sandstone clasts occur with the limestone and claystone clasts. Upslope from the upper crossing of the road (fig. 

1), clasts of white, limy sandstone and silicified limestone are 

especially common. In the triangular deposit of residuum north 

of the modern landslide (fig. 1), white or light-gray limestone 

occurs with only minor amounts of white, limy sandstone and 

greenish-gray claystone clasts. In the northeastern corner of the 

map area (fig. 1), the residuum contains white, fine- to medium-grained, limy sandstone and light-gray claystone with 

small amounts of limestone. 

3 
Distribution of Landslide Debris and Residuum 

The distribution of residuum and landslide deposits 

closely correlates with topographic position at the 

site (fig. 1). A thin, discontinuous mantle of residuum 

covers large, north-trending ridges and some minor 

troughs. Bedrock crops out at few locations, mainly on 

ridge crests and in road cuts. Landslide debris occupies 

the main trough through the center, the branch trough in 

the northeast, and the low-lying, marshy ground in the 

northwest corner of the area, beyond the limits of the area 

shown in figure 1. 

Drilling 

Figure 2 shows the locations of borings drilled by the 

USGS during the summers of 1984 and 1985. During 

August 1984, five holes were drilled in the upper part of 

the landslide with a truck-mounted drill rig formerly 

operated by the USGS Geotechnical Laboratory, Golden, 

Figure 2. Map showing locations of boreholes in the 

Aspen Grove landslide. Landslide features and topographic contours based on detailed mapping by 

Fleming and Johnson (1989). 

4 

Colorado (Roger Nichols, Supervisor). One was drilled in 

ground adjacent to the landslide (borehole B4, figure 2). 

Another was drilled through the right flank of the landslide (B3), and three others were drilled near midwidth 

(B1, B2 and B2A). During July 1985, two new holes (B5 

and B6) were drilled near B1. Three undisturbed samples 

were collected near the bottom of borehole B6 for laboratory testing. Logs of the borings (Appendix A) indicate 

the methods of drilling and sampling used in each hole, 

the sample intervals, stratigraphic interpretations, instrumentation and methods of backfilling the boreholes. 

Geologic interpretation of borehole data 

Examination of the cuttings and detailed description of cores determined the stratigraphy of the debris in the 

upper part of the Aspen Grove landslide. The log of one 

boring (B4, Appendix A) shows the older landslide debris 

about 30 m northeast of the modern Aspen Grove landslide. The others (B1, B2, B2A, B3, B5, and B6; 

Appendix A) show the debris involved in the upper part 

of the landslide. Details of each profile are different, of 

course, but three layers can be identified in each profile. 

From the top downward they are: (1) top soil; 1 to 2 m of 

black to dark brown, organic, sandy clay containing sandstone boulders; (2) landslide debris; 4 to 6 m of brown or 

yellow-brown, plastic, sandy clay containing sandstone 

boulders; (3) bedrock of Flagstaff Limestone; green, gray, 

and tan claystone interbedded with white, cherty limestone. Evidence of a failure surface above or at the top of 

weathered bedrock is discussed below. 

Tube samples collected in borehole B6, in the upper 

part of the Aspen Grove landslide, were extruded and 

examined in the laboratory. Drillers pushed a tube sampler inside a hollow-stem auger to obtain nominally continuous, relatively undisturbed samples between depths of 

4.57 m and 6.59 m. Sample recovery totaled 1.51 m, or 

75 percent of the total interval sampled. Consequently the 

depth where samples originated are known only approximately. Several intervals of the tube samples (fig. 3) were 

thinly laminated, plastic clay, like that shown in figure 4. 

Alternating intervals were massive plastic clay or silty 

clay. 

Study of the tube sample suggests that the failure zone 

or slip surface of the landslide passed through the laminated clay at depths of 6.15 or 6.52 m (fig. 3). A crack 

and some poorly developed slickensides that dipped 

about 15° were observed at a contact between silty clay 

and laminated clay at a depth of 6.15 m. There was a disturbed zone at the base of the tube sample in greenishgray, waxy shale at a depth of 6.52 m, but much of the 

disturbance was due to drilling, because the most obvious 
5.0 

5.5 

6.0 

6.5 Depth, meters 

Bit or sampler type 

Interval/ recovery 

Graphic log 

3-inch 

tube 

3-inch 

tube 

3-inch 

tube 

0.51 m/ 

0.68 m 

(75%) 

0.50 m/ 

0.65 m 

(77%) 

0.50 m/ 

0.68 m 

(74%) 

Detailed log of tube samples from the lower part of hole B-6 in the 

Aspen Grove landslide, Sanpete County, Utah 

AG1-1 

AG1-2 

AG2-1 

AG3-

AG3-2 

Crack, slickensides at contact 

Variegated brown, gray, and yellow sandy clay with many fragments of 

yellow and white sandstone, siltstone and white to gray limestone and 

fragments of red and green shale, lithology of sand fraction, quartz, 96%; 

limestone, 2-3%; brown chert, 1-2%; hematite, trace; sandstone granules, 

trace; Liquid Limit, LL=38; Plasticity Index PI=26. 

Plastic, slippery, faintly laminated, sandy clay, gray on fresh surfaces, on 

exposure to air, weathers overnight to brown, 

fraction, quartz, 94%, limestone, 5%; brown chert, 1%. 

Brown, sandy, plastic clay with yellow and white sandstone fragments in 

upper 8 cm limestone granules in upper 1 cm. 

Laminated, sandy, plastic clay with fragments of sandstone and 

limestone, 

Laminations are blue-gray, medium brown, yellow, dark gray and olive; 

no laminations in upper 3 cm. 

90%; limestone 9%, black and brown chert, 1%, sandstone fragements, 

trace; 

Green clay with fragments of green shale, upper 12 cm, top contact is 

gradational; weathered sandstone fragments, 0.5-1.0 cm abundant near 

top. 

weathered yellow sandstone; 

contact with some faint slickensides on part of the surface. 

15°. 

Dark brown-gray, laminated, waxy, plastic clay with scattered fragments of 

white limestone, sandstone, and green shale, lithology of sand-sized 

fraction, quartz, 85-90%; limestone, 1%; chert, 10-14%; magnetite, trace; 

LL=59, PI=16 

Medium brown sandy clay with abundant fragments of white limestone 

Medium-hard, waxy, green, laminated shale, upper contact irregular but 

distinct, 

chert, 2%; gray to green-gray calcite-cemented shale fragments, 98%; 

Circumferential slickensides 

Hard, gray, slightly gritty, laminated shale, yellow iron-oxide stains on joints 

lithology of sand-sized 

LL=68, PI=49 

separates at sand stringer 9 cm above base of unit. 

Lithology of sand-sized fraction, quartz, 

LL=52, PI=36 

Lower 2 cm variegated and streaked brown clay with pieces of 

bottom contact distinct. Crack at bottom 

Crack dips 

lithology of sand-sized fraction, quartz, trace; brown translucent 

Figure 3. Detailed log of tube samples near the bottom of borehole B-6. The graphic log is drawn as if 

the material recovered in the tube samples came from the bottom of each interval. 

5 
D3) were deeper. Cable D5 was not 

pulled down the hole, and was anchored 

at a depth of 4.9 m. Monitoring of the 

cables, therefore, indicated that the failure surface is at a depth between 4.9 m 

(D5) and 11 m (D4). Now, at B1 we also 

had an observation well of PVC pipe for 

measuring water levels. It was open to 

12.5 m depth in August 1984. In April 

1985, the pipe had been sheared and one 

could probe it to a depth of only 5.95 m. 

On this basis, we infer that the failure Figure 4. Photograph of tube sample from borehole B-6. Laminated clay surface is between 6 and 11 m deep; we from vicinity of the basal shear zone. 

structures were slickensides with circumferential striations. 

Depth to basal slip surface 

Our observations determined the thickness of the 

Aspen Grove landslide in only a few places. Near 

boreholes B1, B5, and B6, the landslide is about 6 m 

deep. At mid width in the landslide near holes B2 and 

B2A, the depth of the basal slip surface is poorly known, 

only that it occurs at a depth of between 3.1 and 6.5 m. 

One to two meters inside the right flank at borehole B3, 

the failure surface is about 2.5 m deep2. It is unclear, 

here, whether the failure surface is the flank fault or the 

basal shear surface; we suspect it is the flank fault, in 

which case the average dip of the flank fault would be on 

the order of 45 to 60°. 

Depths to the failure surface in the boreholes were 

determined by measuring the changes in lengths of 

cables anchored at various depths in holes B1 and B3, 

knowing the depths of piezometers that were damaged 

by landslide movement, or by measuring the depths of 

observation wells disrupted by the landslide. 

For example, at B1 five cables were anchored at different depths, (D1 through D5, Appendix A). Cables Dl, 

D2, D3 and D4 were pulled down the borehole and their 

length above ground shortened by 2.7 m between August 

1984 and July 1985, indicating that these cables were 

anchored below the failure surface. Cable D4 was 

anchored at a depth of 11 m. The others (D1, D2, and 

2Cables were anchored at various depths in holes B1 and B3 to 

locate approximately the depth of the failure surface. Cables 

anchored below the failure surface are pulled down the hole as 

the landslide moves downslope; consequently, their length 

above ground shortens. Cables anchored in ground above the 

failure surface are not pulled down the hole and, thus, their 

length above ground is unchanged by movement. 

assume that it is 6 m deep. 

Geotechnical Properties 

Samples for determination of standard physical properties were collected from various units within the tube 

samples taken in borehole B6 in 1985. The samples are 

identified by the depth in meters near the middle of the 

sample (table 1) or by sample numbers shown on figure 

3. Two grab samples were also collected from boring B-3 

during 1984 (table 2). 

Particle-size distributions and Atterberg limits for the 

samples are given in tables 1 and 2. The tables show that 

materials identified as clay or silty clay in the log (fig. 3) 

indeed are dominantly clay or silty clay. In the bottom 2 

m of borehole B6, the clay content ranges from 44 to 74 

percent, the plastic limit (PL) ranges from 12 to 19 percent and the plasticity index (PI) ranges from 26 to 49 

percent. A sample of green shale collected about a 

decimeter above the bedrock has relatively high clay content of 58 percent and a low PI of 28. Microscopic examination of the sand fraction indicates that 95 percent of 

the sand-sized fraction in the shale sample is actually calcite-cemented claystone fragments. Cementation of the 

clay particles in the shale might be responsible for the 

low PI. 

The strength of several samples was determined at the 

USGS Geotechnical Laboratory in Golden, Colorado. An 

undisturbed sample was tested in order to estimate peak 

strength and residual strength. Disturbed samples were 

tested to estimate the residual strength. 

Test procedures 

Direct shear test of undisturbed sample.—The tests were 

done in a direct-shear apparatus under slow, drained conditions. Specimens were cut from tube sample AG3-1 in 

the interval from 6.15 to 6.35 m (fig. 3) and trimmed to 

fit the shear box of the direct shear device (6.4 cm in 

diameter and 2.08 cm thick). Water content of each specimen before the test was determined from trimmings, and 

6 
Table 1. Physical Properties of Samples from Hole B-6


[Test specimens cut from tube samples representing the depths indicated in the table. Tony Shanahan conducted the tests.]


Sample depth Particle Size Distribution Atterberg limits Grain density 

(meters) Gravel Sand Silt Clay (water content, percent of weight of solids) (g/cm3) 

>4.76 mm 4.76- 0.075 0.075- 0.005 <0.005 mm LL PL PI 

mm mm 

4.8 0 27 29 44 38 12 26 2.76 

5.1 1 11 29 59 68 19 49 2.75 

5.6 1 14 31 54 52 16 36 2.81 

6.3 2 6 18 74 59 16 43 2.68 

6.5 0 17 25 58 46 18 28 2.76 

Table 2. Physical Properties of Samples from Hole B-3


[Test specimens were grab samples of cuttings collected when the auger bit was at the depth indicated. Tony Shanahan conducted the


tests]


Sample depth Particle Size Distribution Atterberg limits Grain density 

(meters) Gravel SandSilt Clay (water content, percent of weight of solids) (g/cm3) 

>4.76 mm	 4.76- 0.075 0.075- 0.005 <0.005 mm LL PL PI 

mm mm 

7.3 0 6 33 61 61 16 45 2.72 

11.3 0 14 16 70 41 15 26 2.72 

Table 3. Summary results of direct shear tests


[George S. Erickson and Anthony Shanahan performed the tests. Sample type, "I" denotes intact, "R" denotes remolded. Sample ID


appears on laboratory plots of stress and displacement. Water content reported as weight percent of solids. Peak strength of remolded


samples not representative of peak strength of intact material]


Borehole/ 

Sample ID 

Sample 

Type 

Depth 

(m) 

Normal 

Stress, 

(kN/m2

) 

Initial 

water 

content 

Final 

water 

content 

Rate 

(mm/min) 

Peak 

strength 

(kN/m2

) 

Displacement 

at peak 

(mm) 

Residual 

strength 

(kN/m2

) 

B-6/ AG3-1 I 6.3 34.5 19.0 25.7 0.0240 42.4 1.0 21.5 

B-6/ AG3-1 I 6.3 137.9 19.2 23.9 0.0240 76.7 1.2 43.2 

B-6/ AG3-1 I 6.3 413.8 20.7 23.2 0.0240 122.4 5.4 116.7 

B-3/ DH4-1 R 7.3 47.9 15.7 26.9 0.0048 28.0 0.9 19.3 

B-3/ DH4-1 R 7.3 382.9 14.2 22.4 0.0048 116.8 4.2 104.5 

B-3/ DH4-1 R 7.3 750.3 -- -- 0.0048 216.8 6.2 208.9 

B-3/ DH4-2 R 11.3 47.9 13.0 22.0 0.0048 30.4 3.1 26.9 

B-3/ DH4-2 R 11.3 382.9 13.8 17.7 0.0048 176.5 7.0 174.8 

B-3/ DH4-2 R 11.3 765.8 12.8 18.5 0.0048 326.6 7.6 325.4 

water content after the test was determined from a piece 

of the specimen. Each specimen was placed in the shear 

box of the direct shear apparatus and consolidated under 

a normal stress (table 3). Each specimen was then 

sheared at a constant rate (table 3) until displacement 

totaled 9 mm. Three separate specimens were tested at 

different normal loads. The stress-displacement diagrams 

are shown in Appendix B. 

Direct shear test of disturbed, remolded samples.—The 

tests were done in a direct-shear apparatus under slow, 

drained conditions. Specimens were remolded from material passing a number 10 sieve (material finer than 2 mm) 

and tamped into the 6.4 cm diameter shear box. The 

remaining test procedure was the same as for the undisturbed sample. 

Torsional shear test of disturbed, remolded samples.— 

The tests were done in a Bromhead ring-shear apparatus 

under slow, drained conditions. Representative samples 

were remolded from the material passing a number 40 

sieve (finer than 0.425 mm) after the Atterberg limits 

7 
-- --

-- --

-- --

-- --

-- --

tests were completed. The samples were consolidated and 

later sheared under a normal load of either 34.5, 137.9, or 

344.8 kN/m2 (5, 20 and 50 lb/in.2). After consolidation, 

the samples were rotated two revolutions to develop a 

shear plane. The samples were then rotated at a rate of 

0.267 mm/minute for about 250 mm; the rate was then 

doubled and shear continued for about four hours (~130 

mm). Finally the rate was reduced by a factor of five to 

finish the test for a total displacement of 400 mm. The 

ring shear sample is only 5 mm thick and drained at the 

top and bottom; thus, drained tests proceed at higher rates 

than in the direct shear apparatus. Table 4 summarizes 

results of the individual tests. 

Shear Strength 

Table 5 summarizes shear-strength parameters of 

material from the Aspen Grove landslide. The landTable 4. Summary results of torsional shear tests 

slide was a reactivation of old landslide deposits, therefore, testing focused on determining residual shear 

strength because it is relevant to reactivation. The angle 

of residual friction, for effective stress, ranged from 5° to 

23°, and residual cohesion, also for effective stress, 

ranged from 5 to 16 kN/m2 (table 5). The landslide material is heterogeneous and representative values for the 

basal shear zone probably lie somewhere inside the 

observed ranges. 

Test results for a sample from the basal shear zone of 

the landslide are of particular interest. The strengths of 

the specimens are plotted as a function of normal stress 

in figure 5. The peak strength defines a segmented failure 

envelope. The intercept is about 31 kN/m2 and the segment defining peak strengths at lower normal stress 

slopes about 18°. The segment defining peak strengths at 

higher normal stresses slopes about 9°. 

Upper- and lower-bound estimates of the residual 

strength are also shown in figure 5. The 

upper-bound estimate uses the strength at 

[George S. Erickson performed the tests. Water content reported as weight percent of the end of each direct-shear test. The 

solids. Rate is average value at middle of sample. After 250 mm of displacment, rate upper-bound failure envelope has an inter- was doubled; after an additional 130 mm of displacement, the rate was reduced by a 

factor of 5] cept of 10.8 kN/m2 and slopes 14.3°. The 

lower-bound estimate uses the residual 

Borehole/ Depth Normal Initial Final Rate Residual 

Sample ID (m) Stress, water water (mm/ min) strength 

(kN/m2

) content content (kN/m2) 

B-6/ AG1-2 4.8 34.5 27.4 28.1 0.267 18.4 

B-6/ AG1-2 4.8 137.9 26.7 23.8 0.267 65.4 

B-6/ AG1-2 4.8 344.8 26.7 23.2 0.267 108.8 

B-6/ AG1-1 5.1 34.5 57.5 50.4 0.267 13.5 

B-6/ AG1-1 5.1 137.9 56.1 44.2 0.267 23.7 

B-6/ AG1-1 5.1 344.8 55.2 44.2 0.267 43.6 

B-6/ AG3-1 6.3 34.5 42.5 38.7 0.267 8.6 

B-6/ AG3-1 6.3 137.9 42.7 39.7 0.267 19.2 

B-6/ AG3-1 6.3 342.9 43.0 41.6 0.267 40.2 

Table 5. Summary of shear strength parameters for effective stress from drained direct


shear and ring shear tests


[DS denotes direct shear test, RS denotes torsional ring shear test]


Peak Strength Residual Strength 

Borehole/ Test Depth Angle of Cohesion Angle of Cohesion 

Sample ID Type (m) internal (kN/m2

) internal (kN/m2) 

friction friction 

(degrees) (degrees) 

B-6/ AG3-1 DS 6.3 11.4 41.1 14.3 10.8 

B-6/ AG3-1 RS 6.3 5.8 5.1 

B-6/ AG1-1 RS 4.8 5.5 10.2 

B-6/ AG1-2 RS 5.1 15.6 16.0 

B-3/ DH4-1 DS 7.3 15.1 4.5 

B-3/ DH4-2 DS 11.3 22.6 10.0 

strength determined for the specimen tested under a normal stress of 414 kN/m2, 

and projects through the origin. Slopes of 

the stress-displacement diagrams 

(Appendix B) indicate that the specimen 

tested under a normal stress of 414 kN/m2 

was the only one of the three that attained 

its residual strength after 9 mm of shearing. The lower-bound estimate has an 

intercept of 0 kN/m2 and slopes 15.8°. A 

torsional shear test on material from the 

same interval had residual-strength 

parameters of 5° and 5.2 kN/m2. 

Removal of particles larger than 0.425 

mm from the torsional shear test specimens may have reduced the strength 

slightly relative to the total sample; however, the coarse particles accounted for 

only about 2 percent of the total. 

Surface and Subsurface Water 

Observations 

Snow meltwater infiltrating at the surface of the landslide was almost certainly the main source of water in the 

landslide. When we visited the landslide 

in May 1984, snow was still melting on 

8

■ Peak strength ● Residual strength (DS) ▲ Residual strength (RS) 

150 

Shear stress, kPa 

100


50
 ■ 

■ 

■ 

● 

● 

● 

▲ 

▲ 

▲ 

0 

0 50 100 150 200 250 300 350 400 450 

Normal stress, kPa 

Figure 5. Failure envelopes for sample AG3-1 from about 6.3 m depth in borehole B-6. Peak shear 

strength, dashed black line represents segmented strength envelope; solid black line represents best fit 

straight-line envelope. Residual strength by direct shear (DS), dashed light-gray line represents lowerbound estimate through the origin and the strength at the highest normal load; solid light-gray line 

represents best fit straight line envelope and upper bound estimate of the resiudal strength. Residual 

strength by torsional shear (RS) solid gray line represents best fit straight-line envelope. 

the surface of the landslide. Meltwater flowed everywhere across the surface of the landslide, in numerous 

rivulets. Shallow holes, about 1 m deep, dug into the 

internal toe and at the lower road crossing, to emplace 

pressure cells, quickly filled with water flowing from the 

walls of the holes. Cracks and hollows contained ponded 

water. The trough-like topography on the surface of the 

landslide channelizes the meltwater from the head to the 

foot. Surface channels drain away from the landslide only 

in the area of the old foot. Even there, channels bring the 

water back onto the sliding ground beyond the internal 

toe (figure 1). 

Timing of the landslide activity was roughly synchronous with the presence of surface water on the landslide. 

The beginning of movement coincided approximately 

with the spring thaw in 1984, 1985 and 1986. The end of 

movement coincided approximately with the drying up of 

ponds on the surface of the landslide. 

Water-level measurements during parts of 1985 and 

1986 in six boreholes, B1 through B6, are shown in 

Tables 6 and 7. Water levels were measured directly in 

boreholes B1, B2 and B3, and water levels were calculated from piezometric measurements made in boreholes 

B4, B5 and B6. We have indicated the water levels in 

terms of the height of water above the sensor or base of 

the open-tube piezometer. Some of the vibrating-wire 

piezometers were destroyed by movement of the landslide early in the spring of 1984 and did not provide any 

useful data. 

The measurements show that, at three locations within 

the upper part of the landslide, between B-1 and B-2, the 

water level was always within 3 m of the ground surface 

during April through August 1985 and during February 

through September 1986. The best record exists for B1, 

where water level fell 1.2 m from a maximum height of 

about 0.3 m below the ground surface during May to 

about 1.5 m below the ground surface when movement 

stopped in 1985. According to the scant data, the water 

level was at a depth of about 1 m when movement began 

in 1986. Again, the water level appears to have reached a 

maximum during May (tables 6 and 7). In contrast, the 

water level in the one borehole in stable ground outside 

the landslide, B4 (table 7) was always low, at depths 

greater than 3 m below the ground surface. Water levels 

ranged from 3 to 5 m below the ground surface during 

the period of measurement (table 7). 

9

--

--

--

-- --

--

--

--

--

Table 6. Height of water column (pressure head) 

observed at open-tube piezometers 

Boring B1 B2A B3 

Depth of 5.96 3.46 12.48 

piezometer 

(meters) 

Date Pressure head Pressure head Pressure head 

(meters) (meters) (meters) 

4/21/85 

4/24/85 

4/26/85 

4/28/85 

4/28/85 

4/29/85 

4/30/85 

5/1/85 

5/5/85 

5/15/85 

5/18/85 

5/24/85 

5/31/85 

6/4/85 

6/14/85 

7/2/85 

7/8/85 

7/11/85 

7/15/85 

7/18/85 

7/22/85 

7/26/85 

7/29/85 

8/1/85 

4/18/86 

5/28/86 

5/31/86 

9/9/86 

3.369 3.46 1.72 

3.7 1.66 

4.96 1.91 

5.312 1.67 

5.325 

5.96 1.70 

5.312 1.70 

5.401 3.409 1.70 

5.646 2.492 

5.506 3.46 1.69 

5.417 3.46 1.43 

5.319 3.46 1.22 

5.315 3.158 1.00 

5.246 3.133 0.94 

5.08 2.79 0.77 

4.92 2.39 0.41 

4.7 2.12 0.42 

4.58 1.98 0.32 

4.48 1.81 0.27 

4.41 1.66 0.23 

4.35 1.59 0.19 

4.32 1.48 0.12 

4.27 1.4 0.07 

4.24 1.31 0.03 

3.33 1.06 

5.265 3.12 0.83 

5.2 3.03 0.79 

3.63 0.53 0.00 

1

 Depth varied through time as the landslide moved over a bump


in the slip surface. Initially the tube sheared at depth of 2.48 m.


As the slide moved, the tube gradually pushed out of the ground.


By September 1986, the upper 1.16 m of the tube protruded from


the ground and the base of the tube was 1.32 m below the ground surface.


10

-- --

-- --

-- --

-- -- --

-- -- --

-- -- --

--

-- -- --

--

--

--

--

--

--

--

--

--

--

--

--

--

-- --

-- --

-- -- --

Table 7. Pressure head observed using vibriating-wire piezometers. 

[Piezometers shown on logs but not listed in table stopped working 

before the 1985 field season. Piezometers were by Slope Indicator Co., 

model number 52605211, 150 psi pressure range.] 

Boring B2 B4 B4 B5 B6 

Depth of 17.28 5.03 6.71 6.10 6.48 

sensor, 

meters 

Date Pressure head 

(meters) 

Pressure head 

(meters) 

Pressure head 

(meters) 

Pressure head 

(meters) 

Pressure head 

(meters) 

4/21/85 0.45 1.87 2.36 

4/23/85 0.39 1.75 2.36 

4/24/85 0.45 1.87 2.42 

6/24/85 0.99 2.03 

6/27/85 0.66 1.72 

6/27/85 0.81 1.93 

7/2/85 0.60 1.75 5.09 5.36 

7/3/85 7.70 6.57 

7/5/85 0.54 1.75 7.88 6.27 

7/8/85 0.51 1.69 8.00 6.34 

7/11/85 0.48 1.69 8.00 6.21 

7/15/85 0.42 1.69 7.94 6.08 

7/18/85 0.30 1.60 7.76 5.95 

7/22/85 0.24 1.63 7.73 5.95 

7/23/85 0.27 1.63 7.70 5.95 

7/26/85 0.12 1.45 7.46 5.81 

7/29/85 0.06 1.45 7.28 5.75 

8/1/85 0.00 1.45 7.09 5.68 

2/12/86 -0.42 1.63 5.28 5.46 

3/14/86 -0.72 1.33 5.94 5.10 

4/18/86 -0.48 2.12 6.06 4.90 

5/28/86 1.45 3.33 6.25 

5/31/86 1.42 3.20 6.18 

9/9/86 -0.66 4.37 

References Cited 

Baum, R.L., 1988, The Aspen Grove landslide, Ephraim 

Canyon, central Utah: Cincinnati, Ohio, The University of 

Cincinnati, unpublished Ph.D. dissertation, 363 p. 

Baum, R.L., Johnson, A.M., and Fleming, R.W., 1988, 

Measurement of slope deformation using quadrilaterals, 

chap. B of Landslide processes in Utah—Observation and 

theory: U.S. Geological Survey Bulletin 1842, p. B1-B23. 

Baum, R.L., and Fleming, R.W., 1989, Landslides and debris 

flows in Ephraim Canyon, central Utah, chap. C of 

Landslide processes in Utah—Observation and theory: U.S. 

Geological Survey Bulletin 1842, p. C1-C12, 1 oversize 

plate. 

Baum, R.L., Fleming, R.W., and Johnson, A.M., 1993 [1994], 

Kinematics of the Aspen Grove landslide, Ephraim Canyon, 

central Utah, chap. F of Landslide processes in Utah— 

Observation and theory: U.S. Geological Survey Bulletin 

1842, p. F1-F34. 

Baum, R.L., and Reid, M.E., 2000, Groundwater isolation by 

low-permeability clays in landslide shear zones, in 

Bromhead, E., Dixon, N, and Ibsen, M., eds., Landslides in 

Research, Theory and Practice, Proceedings of the 8th 

International Symposium on Landslides: London, Thomas 

Telford p. 139-144. 

Fleming, R.W., and Johnson, A.M., 1989, Structures associated with strike-slip faults that bound landslide elements: 

Engineering Geology, v. 27, p. 39-114. 

Stanley, K.O., and Collinson, J.W., 1979, Depositional history 

of Paleocene-lower Eocene Flagstaff Limestone and coeval 

rocks, central Utah: American Association of Petroleum 

Geologists Bulletin, v. 63, no. 3, p. 311-323. 

11

A1

B-1

Sample Data Soil Profile Completion Detail

5

10

15

20Depth, meters

Bit orsampler type

Interval/recovery

Graphic log

Ground Elevation 2401 m (MSL)

Dark brown organic clay with gravel- and 

cobble-sized sandstone clasts (Soil)

Gravel-, cobble, and boulder-sized clasts 

of sandstone in a matrix of clay and 

weathered claystone (Landslide debris)

3-inch 

tube

5-inch

auger

NXcore

3-inch 

rock bit

0.4 m

0.9 m

1.2 m

0.3 m Gray, white and light-brown claystone and 

shale interbedded with cherty limestone, 

siltstone and minor sandstone. (Flagstaff 

Limestone)

1-inch PVC, 

open at 

bottom

Sand backfill

Anchor of 

displacement 

gauge, D5

Anchor of 

displacement 

gauge, D4

Anchor of 

displacement 

gauge, D3

--

--

--

Cuttings

Cuttings

Aspen Grove Landslide, Sanpete County, Utah

Appendix A. Borehole logs 
Appendix A. Borehole logs—continued 

A2

Sample Data Soil Profile Completion Detail

25

30

35

40Depth, meters

Bit orsampler type

Interval/recovery

Graphic log

Ground Elevation 2401 m (MSL)

3-inch 

rock bit Gray, white and light-brown claystone and 

shale interbedded with cherty limestone, 

siltstone, and minor sandstone (Flagstaff 

Limestone)

Sand backfill

Anchor of 

displacement 

gauge, D2

Anchor of 

displacement 

gauge, D1

Cuttings

B-1 (continued)

Cave-in 

material

Boring completed 17 August 1984

Total depth 33.7m

Aspen Grove Landslide, Sanpete County, Utah
Appendix A. Borehole logs—continued 

A3

Sample Data Soil Profile Completion Detail

5

10

15

20Depth, meters

Bit orsampler type

Interval/recovery

Graphic log

Ground Elevation 2386.5 m (MSL)

B-2

Sand backfill

Dark brown, organic clay (Soil)

Brown to light-brown, silty sand, gravel-and 

cobble-sized clasts of limestone and sandstone 

throughout (Landslide debris) 

3-inch 

rock bit, 

with 

fluid

Bentonite

Cuttings

Sand backfill

3-inch PVC 

casing stuck in 

hole.

Bentonite

Blue-gray, light gray, and light-brown clay or 

claystone and shale interbedded with limestone, 

siltstone and minor sandstone (Flagstaff 

Limestone)

Aspen Grove Landslide, Sanpete County, Utah

Vibrating-wire 

Piezometer

Vibrating-wire 

Piezometer

Sand backfill

Bentonite

Bentonite

Blue-gray, light gray,and brown clay to sandy silty 

clay with limestone fragments (Landslide 

debris or weathered Flagstaff Limestone?)
Appendix A. Borehole logs—continued 

A4

Sample Data Soil Profile Completion Detail

25

30

35

40Depth, meters

Bit orsampler type

Interval/recovery

Graphic log

Ground Elevation 2386.5 m (MSL)

3-inch 

rock bit, 

with fluid

Gray, white and light-brown claystone and 

shale intebedded with cherty limestone and 

minor sandstone (Flagstaff Limestone)

Sand backfill

B-2 (continued)

Boring completed 22 August 1984

Total depth 22.25m

Aspen Grove Landslide, Sanpete County, Utah

Soft, 

few 

cuttings 

returned 

below 

19.5 m
Appendix A. Borehole logs—continued 

A5

Sample Data Soil Profile Completion Detail

5

10

15

20Depth, meters

Bit orsampler type

Interval/recovery

Graphic log

Ground Elevation 2386.5 m (MSL)

B-2A

Dark brown, organic, sandy clay (Soil Sand backfill )

Brown to light-brown, moist, sandy clay grades 

downward to silty sand, gravel-and cobble-sized 

clasts of limestone and sandstone throughout, 

saturated below 3.3 m (Landslide debris) 

6-inch 

auger

Bentonite

Cuttings

Sand backfill

1-inch PVC, 

slotted at 

bottom 0.6 m

Bentonite

Water table on 18 August 1984

No 

samples 

returned

Stoped 

drilling, 

18 August 

1984

No 

samples 

returned

Gray, white and light-brown claystone and shale 

interbedded with limestone, siltstone and minor 

sandstone (Flagstaff Limestone)

Standing water level 

morning of 20 August 1984

Hole closed off 

to about 3.8 m 

after auger 

removed on 20 

August 1984

Resumed 

drilling, 

20 August 

1984,

hole 

blocked at 

3.1 m, 

pushed 

blockage 

down to 

3.8 m, 

smooth 

drilling 

and no 

samples 

retuned 

to 14.3 m

Aspen Grove Landslide, Sanpete County, Utah
Appendix A. Borehole logs—continued 

A6

Sample Data Soil Profile Completion Detail

25

30

35

40Depth, meters

Bit orsampler type

Interval/recovery

Graphic log

Ground Elevation 2386.5 m (MSL)

6-inch 

auger

Gray, white and light-brown claystone and shale 

interbedded with limestone, siltstone and minor 

sandstone (Flagstaff Limestone)

Cuttings

B-2A (continued)

Boring completed 20 August 1984

Total depth 22.4 m

Aspen Grove Landslide, Sanpete County, Utah
Appendix A. Borehole logs—continued 

A7

Sample Data Soil Profile Completion Detail

5

10

15

20Depth, meters

Bit orsampler type

Interval/recovery

Graphic log

Ground Elevation 2391.5 m (MSL)

Sand backfill

B-3

Boring completed 23 August 1984

Total depth 16.3 m

Cuttings used 

for backfill

Vibrating-wire 

Piezometer

Bentonite

Dark brown, organic, sandy clay (Soil)

Brown to light-brown, moist, sandy to silty clay 

with gravel-and cobble-sized clasts of limestone 

and sandstone, color lightened and sand 

content decreased with depth (Landslide 

debris)

5-inch 

auger

Bentonite

Sand backfill

Gray, green, and light brown claystone 

interbedded with limestone and cherty limestone, 

becomes harder and less weathered with depth 

(Flagstaff Limestone)

Grab 

sample,

B3-1

Grab 

sample,

B3-2

Cuttings

Yellow-brown fine sand with sandstone clasts 

(Landslide debris)

Cave-in 

material

Sand backfill

Bentonite

Sand backfill

Vibrating-wire 

Piezometer

1-inch PVC, 

open at bottom

Anchor of 

displacement 

gauge, D2

Anchor of 

displacement 

gauge, D1

Aspen Grove Landslide, Sanpete County, Utah
Appendix A. Borehole logs—continued 

A8

Sample Data Soil Profile Completion Detail

5

10

15

20Depth, meters

Bit orsampler type

Interval/recovery

Graphic log

Ground Elevation 2401 m (MSL)

Sand backfill

B-4

Boring completed 24 August 1984

Total depth 8.5 m

Cuttings used 

for backfill

Vibrating-wire 

piezometer

Bentonite

Dark brown, organic, sandy clay

Light-brown to yellow-brown, moist, sandy silt to 

sandy, silty clay with gravel-and cobble-sized 

clasts of limestone and sandstone

Stiff, brittle, gray claystone

3-inch 

tube

0.3 m

0.8 m

0.6 m

Bentonite

Sand backfill

NX core

1.5 m

0.9 m

0.4 m

0.8 m

0.7 m

Vibrating-wire 

piezometer

Aspen Grove Landslide, Sanpete County, Utah
Appendix A. Borehole logs—continued 

A9

Sample Data Soil Profile Completion Detail

5

10

15

20Depth, meters

Bit orsampler type

Interval/recovery

Graphic log

Ground Elevation 2401 m (MSL)

Sand backfill

B-4

Boring completed 24 August 1984

Total depth 8.5 m

Cuttings used 

for backfill

Vibrating-wire 

piezometer

Bentonite

Dark brown, organic, sandy clay

Light-brown to yellow-brown, moist, sandy silt to 

sandy, silty clay with gravel-and cobble-sized 

clasts of limestone and sandstone

Stiff, brittle, gray claystone

3-inch 

tube

0.3 m

0.8 m

0.6 m

Bentonite

Sand backfill

NX core

1.5 m

0.9 m

0.4 m

0.8 m

0.7 m

Vibrating-wire 

piezometer

Aspen Grove Landslide, Sanpete County, Utah
Appendix A. Borehole logs—continued 

A10

Sample Data Soil Profile Completion Detail

5

10

15

20Depth, meters

Bit orsampler type

Interval/recovery

Graphic log

Ground Elevation 2401.8 m (MSL)

Sand backfill

B-5

Boring completed 2 July1985

Total depth 6.4 m

Cuttings used 

for backfill

Vibrating-wire 

piezometer

Approximate 

standing water 

level 30 

minutes after 

completion

Bentonite

Dark brown, sandy, organic clay

Silty, sandy brown clay

Limestone and sandstone gravel

Soft, light-brown clay and silty clay

Moist brown sandy clay

Soft, light-brown clay with limestone 

Light-gray, wet, very soft clay

6-inch 

hollowstem 

auger

Cuttings

Aspen Grove Landslide, Sanpete County, Utah
Appendix A. Borehole logs—continued 

A11

Sample Data Soil Profile Completion Detail

5

10

15

20Depth, meters

Bit orsampler type

Interval/recovery

Graphic log

Ground Elevation 2401.8 m (MSL)

Sand backfill

B-6

Boring completed 2 July1985

Total depth 6.6 m

Cuttings used 

for backfill

Vibrating-wire 

Piezometer

Bentonite

Dark brown, organic, sandy clay

Dark brown, moist, sandy clay with gravel-and 

cobble-sized clasts of limestone and sandstone

Gray and light-brown moist clay with gravelsized limestone clasts

6-inch 

hollowstem 

auger

Cuttings

Hard, dry, gray clay shale

3-inch 

tube

0.51 m

0.51 m

0.50 m

Aspen Grove Landslide, Sanpete County, Utah
Appendix B. Stress-displacement plots of direct-shear and 


torsional-shear test


B1

03

Appendix B. Stress-displacement plots of direct-shear and

torsional-shear test—Continued

DIRECT SHEAR TEST
Appendix B. Stress-displacement plots of direct-shear and 


torsional-shear test—Continued


B3

Appendix B. Stress-displacement plots of direct-shear and 


torsional-shear test—Continued


B4

Appendix B. Stress-displacement plots of direct-shear and 


torsional-shear test—Continued


B5

Appendix B. Stress-displacement plots of direct-shear and 


torsional-shear test—Continued


B6

Appendix B. Stress-displacement plots of direct-shear and 


torsional-shear test—Continued


B7

Appendix B. Stress-displacement plots of direct-shear and 


torsional-shear test—Continued


B8

Appendix B. Stress-displacement plots of direct-shear and 


torsional-shear test—Continued


B9

Appendix B. Stress-displacement plots of direct-shear and 


torsional-shear test—Continued


B10

Appendix B. Stress-displacement plots of direct-shear and 


torsional-shear test—Continued


B11

Appendix B. Stress-displacement plots of direct-shear and 


torsional-shear test—Continued


B12

Appendix B. Stress-displacement plots of direct-shear and 


torsional-shear test—Continued


B13

Appendix B. Stress-displacement plots of direct-shear and 


torsional-shear test—Continued


B14

Appendix B. Stress-displacement plots of direct-shear and 


torsional-shear test—Continued


B15

Appendix B. Stress-displacement plots of direct-shear and 


torsional-shear test—Continued


B16

Appendix B. Stress-displacement plots of direct-shear and 


torsional-shear test—Continued


B17

Appendix B. Stress-displacement plots of direct-shear and 


torsional-shear test—Continued


B18