GM 15-19 Pavement Subgrade and Deep Patch Recommendations ID VALLEY 21(8).pdf

158377846

M E M O R A N D U M

Western Federal Lands Highway Division

610 E. Fifth Street

Vancouver, WA 98661

DATE: June 12, 2019

TO: Lindsay Higa

Project Manager

FROM: Orion George, LEG

Licensed Engineering Geologist

COPIES: Nathan Jenks, Geotechnical Lead

Geotechnical File

SUBJECT: Geotechnical Memo 15-19

Pavement Subgrade and Deep Patch

Recommendations

Warren Wagon Road, MP 7.6 to 9.6

ID Valley 21(8)

McCall, Valley County, Idaho

INTRODUCTION

The purpose of this memorandum is to provide geologic observations and recommendations to help inform ongoing design work for the Warren Wagon Road, MP 7.6 to 9.6 project located in Valley

County, Idaho. This segment of the alignment was originally part of a 2013 Federal Lands Access

Program (FLAP) grant. Work on this portion of the roadway was advanced to the 30% design stage, but removed from the previous project as a result of scope expansion on the previous portion of the alignment.

Federal Highway Administration (FHWA) geotechnical engineer, Dustin Woods completed previous work for the 30% design. Any suggestions and recommendations contained within this memorandum supersedes any conflicting suggestions or recommendations contained in previous Geotechnical

Memorandums or Geotechnical Reports (GM 14-15, GR 11-17, and GR 1-18).

Stationing referenced in this memorandum is based on the 30% design stationing for the ID PFH 21(7)

Warren Wagon Road project (the previous project) and may need to be updated or converted for the current ID Valley 21(8) project.

PROJECT DESCRIPTION

This project was chartered to improve drainage, safety, and reduce maintenance costs between mileposts 7.6 to 9.6 on Valley County’s Warren Wagon Road. Repair of failed base material along with regrading and repaving are key components of the project.

GEOLOGY

Please review GM 14-15, GR 11-17, and GR 1-18 for a geologic overview.

SITE CONDITIONS

The project length was walked to assess pavement distress in an attempt to identify potential subgrade issues and locate sites that could benefit from deep patch and subexcavation designs. Western Federal

Lands (WFL) conducted the field work May 15, 2019 and June 3 and 4, 2019 for the basis of the recommendations contained herein. Western Federal Lands Engineering Geologist, Douglas Anderson was present on the May 15, 2019 site visit; he was also involved with the initial phase of work along the preceding stretch of Warren Wagon Road.

Numerous transverse and longitudinal fatigue cracks were observed suggesting frost heaving and subgrade degradation. It was communicated to WFL by Jeff McFadden of Valley County Maintenance the roadway has seen increased distress since the last geotechnical assessment, approximately three years ago. This distress was communicated to WFL as larger and increased pavement cracking along much of the project length.

During the May 2019 site visit, high surface water flows in ditches and other watercourses were observed due to high precipitation and snow melt at the time of work. The June site visits had similarly high flows as well. Runoff from nearby highland areas was seen ponding on the west side (left side) of the roadway and high water due to flooding of the North Fork Payette River was observed on the right side (east side) of the roadway. Ditches were also observed to be poorly drained and often undersized to handle witnessed runoff conditions.

SUBSURFACE CONDITIONS

A 2014 subsurface investigation was completed and is included in GR 11-17. Three subgrade borings from that investigation are located within the limits of this project. Their locations are given in Table 1.

Geotechnical Report GR 11-17 should be consulted for the full results and interpretations of the subsurface investigation. Logs for the three subgrade borings located within the project limits are included with this memorandum as Attachment A.

Table 1. Subgrade boring locations.

Boring

Number

Approximate

Station Mile Post

Distance from

Centerline (ft)

Right or

Left Lane

Depth

(ft)

SG14-15 618+60 8 5.2 R 5.0

SG14-16 644+50 8.5 5.5 L 5.0

SG14-17 669+75 9 7.5 R 5.0

Note:

1. The full subsurface investigation results and interpretations are presented in

Geotechnical Report 11-17 while the bore logs for these subgrades are in Attachment A.

Subgrade boring logs suggest 3 inches to 4 inches of asphalt overlying about 0.2 feet of base rock.

Underlying material is reported as mostly poorly graded silty sand with gravel and some clayey sand with gravel. These subsurface materials have been shown to be frost susceptible soils as seen in the pavement distress and similar conditions encountered on the previous construction project.

No materials testing was conducted on samples from subgrade borings along this part of the roadway.

ANALYSIS AND DESIGN RECOMMENDATIONS

Field work conducted in 2019 suggests areas of subexcavation, deep patches, and improved drainage will benefit the roadway. Locations of recommended areas of subexcavation are listed in Table 2 and deep patches in Table 3, while drainage issues are described by project station. Each of these subjects are also briefly discussed and followed with design recommendations below.

As stated previously, stationing referenced in this memorandum is based on the 30% design stationing for the ID PFH 21(7) Warren Wagon Road project (the previous project) and may need to be updated or converted for the current ID Valley 21(8) project.

Subexcavations

Table 2 provides the identified locations for subexcavation within the limits for this project. However, as discussed in more detail below, it is recommended that a frost-free pavement design be used for the full length of the Phase II project in place of the individual subexcavation locations shown in Table 2.

As can be seen in the stationing in Table 2, there are long lengths of half and full width subexcavations with relatively small distances between the locations. The 2014 subsurface investigation and subsequent field visits gave WFL required information to initially layout likely subexcavation limits for Phase I and

Phase II of this project. However, as Phase I was developed the amount of subexcavation was too great for its funding levels and a cost analysis of using a geotextile separated base layer or “frost free” design for the entire Phase I limits was assessed and ultimately selected for the Phase I project.

Although roadway subgrade consists of materials with reasonably good strength, these materials are frost susceptible, and there is not enough separation between the subgrade and pavement structural section or base layers. The amount of fines that migrate into the base layer weakens this layer and is also susceptible to frost heaves. Consequently, this is causing pumping in wet times of year and frost heave in the winter, resulting in pavement fatigue. The method used for the Phase I project of mitigating subsurface issues, a continuous, geotextile separated base layer, is also recommended for

Phase II. By permanently separating subgrade from base layer materials with a separation fabric, fine soil migration will be limited into the new base layer, helping prevent similar damage to new pavement.

Specific pavement structural design recommendations were provided by the WFL Materials Section for

Phase I, which utilized a clean aggregate low in fines. The cleaner aggregate material, with a separation fabric provides a capillary break below it allowing pavement structure to experience less freeze thaw differential movement. Additionally, pumping and migration of fines is less likely from wheel loading into the base, and drainage of the pavement structural section will be improved. The separation geotextile utilized in the Phase I design was a Class 1, Type C Separation-Stabilization Geotextile

(Subsection 714.01, FP-14).

Table 2. Subexcavation site locations.

Site Roadway

Width

Station

Begin End

SG-01 Full 597+70 603+10

SG-02 Half (left) 603+10 604+95

SG-03 Full 604+95 607+30

SG-04 Half (right) 608+05 608+80

SG-05 Half (right) 615+45 623+40

SG-06 Half (right) 624+60 626+50

SG-07 Full 626+50 628+00

SG-08 Full 628+55 629+80

SG-091 Full 633+35 647+60

SG-10 Full 652+40 659+65

SG-11 Full 660+45 674+00

SG-12 Full 674+95 676+75

SG-13 Half (right) 676+75 678+60

SG-14 Full 681+20 682+80

SG-15 Full 685+50 686+95

SG-16 Full 687+85 690+65

SG-17 Full 696+20 697+20

SG-18 Half (left) 699+85 700+95

Notes:

1. Two potential deep patch locations, DP-D and DP-

E, were identified within the limits of SG-09.

Portions of the Phase I section were constructed during the summer of 2018 and, as of Spring 2019, those sections of roadway were performing well. It is recommended a similar approach be given to the

Phase II design for the entire Phase II limits rather than constructing the individual subexcavation locations provided in Table 2.

Deep Patches

Some pavement damage currently seen is related to shallow road embankment landsliding. In these locations, the cause of pavement distress is too deep for the proposed “frost-free” pavement structural section design to provide stability. In these locations, it is recommended a deep patch be used to mitigate movement and repair the shoulder. Table 3 provides site observations and locations for deep patches.

The final deep repair design for the Phase II project should follow the design guidelines in Deep Patch

Repair, Phase I: Analysis and Design (FHWA-WFL/TD-12-003; Cuelho et al, 2012). There is additional information provided in Table 3, correlating to design parameters in the above referenced manual, to aid in the deep patch design. It is expected that one detail for deep patch repair can be developed and used in all locations of the project to keep various deep patches similar, and aid with construction efficiency. It also suggested that the Phase I deep patch design be reviewed for information in developing the Phase II deep patch design.

Table 3. Deep patch locations and observations.

Site Roadway

Width

Station L1,2

(ft)

Β1,3

(degrees)

SD1,4

(ft)

ϴ1,5

(degrees)

Xc 1,6

(ft)

W1,7

(ft)

Wp 1,8

(ft) Begin End

DP-A Full 660+50 660+85 35 45 28.5 35 26 33 23.5

DP-B Full 674+40 675+00 60 40 68.5 Low 19 28 26.5

DP-C Half (right) 679+60 681+15 155 36 42 40 7.5 31 24

DP-D9 Full 633+35 636+20 285 39 41.5 18.5 36 25.5

DP-E9 Full 639+60 640+35 75 38 39 19.5 36 24.5

Notes:

1. Using Collins, 2015.

2. L = Length along roadway, in feet.

3. β = Embankment angle, in degrees.

4. SD = Sight distance along downhill slope from the hinge point to the toe of the slope, in feet.

5. ϴ = Cut-side backslope angle, in degrees.

6. Xc = Horizontal distance from the slope hinge point to the furthest crack, in feet.

7. W = Width of the roadway bench, in feet.

8. Wp = Pavement width, in feet.

9. Deep patches DP-D and DP-E were identified within the limits of subexcavation SG-09. Site observations were not collected.

There is potential for a culvert conflict within the deep patch limits of DP-C. If there is a conflict, the geosynthetic should be bowed vertically either up or down to make room for the culvert, e.g. if the geosynthetic below the culvert will conflict, decrease the lift thickness in the immediate area of the culvert. If the geosynthetic needs to be bowed more than 12-inches in either direction, it should be cut.

Terminate all cut ends of the geosynthetic within 6-inches of the culvert. It is anticipated that implementing this into design will require hand-work in areas near the conflicting culvert.

Drainage

Overall ditch reconditioning needs to be considered along much of the alignment’s length. Widening and deepening with appropriate angles that encourage flow towards intended culverts and avoiding standing water, particular during spring melt. Also, some locations could benefit from additional cross drainage during seasonally wet periods. This is not a comprehensive assessment of drainage needs along this stretch of roadway as it was not the focus of the investigation. However, specific locations noted during site visits for improved drainage are described below by station along the project length.

In some locations flooding by the river or snow melt from above is causing fines to be removed from the subgrade causing pavement deterioration whereas other areas appear to be accumulating water and saturating the subgrade. These areas need additional cross draining, under draining, ditch regrading and development or a combination of all these methods.

Such a site is approximately station 604+80. Seasonal high water was observed ponding on the west side of the roadway. Cross drainage will help this water flow away from the roadway to the east side of the alignment where a severed meander of the North Fork Payette River is located.

Another area, between approximately stations 687+00 to 690+00, has a ditch with difficult drainage. It did not have a positive drainage angle, was grown in with vegetation, and was shallow. Water was observed standing in the ditch and seeping from cracks in the west lane of the roadway. The site also had a loose differentially eroding cut slope filling the ditch and exposing the roadway to falling rock.

The largest rock observed was almost 2 feet in dimension and sitting in the ditch. Some smaller rock was noted on the left fog line. No severe damage from rockfall was observed such as divots from rock impacts and Valley County Maintenance communicated this was an area of minor rockfall clean up.

It is anticipated that a larger ditch could solve both of these issues at this location. However, cutting into the unconsolidated slope is not recommended. Rather it is recommended to raise the elevation of the roadway in this section. By raising the roadway elevation a larger and deeper ditch could be constructed, which would allow for more rockfall catchment and a better chance for an improved drainage angle. An under drain design should also be considered for this site, particularly if ditch drainage is not improved sufficiently to remove surface water.

REFERENCES

Collins, B.M., 2015, Design considerations for deep patch embankment repair with geosynthetics, Transportation Research Record: Journal of the Transportation Research Board, Transportation

Research Board of the National Academies, Washington D.C., No. 2473, pp. 224-232. DOI:

10.3141/2473-26

Cuelho, E., S. Perkins, & M. Akin, March 2012, Deep Patch Repair, Phase I: Analysis and Design, FHWA-WFL/TD-12-003. http://www.wfl.fhwa.dot.gov/programs/td/publications.

CLOSING

Spatial data, in the form of two Google Earth kmz files, which includes field notes, photographs, and site locations, will be provided to WFL Project Manager Lindsay Higa:

• 2019-05-15 site visit ID_PFH_21(8).kmz

• 2019-06-04 site visit ID_PFH_21(8).kmz

These data files are also available upon request from the author of this memorandum.

Please contact Orion George at (360) 619-7634 or Orion.George@dot.gov with any questions regarding this memorandum.

Attachments: Subgrade Boring Logs: SG14-15, SG14-16, SG14-17 http://www.wfl.fhwa.dot.gov/programs/td/publications mailto:Orion.George@dot.gov

APPENDIX A

SG-1

SG-2

3" Asphalt

Silty GRAVEL with sand (base rock), dark gray, moist, subangular.

Base rock sample obtained.

Silty SAND with gravel, fine to coarse grained, brown, moist, subrounded.

Moisture sample obtained from 6" to 12"

Moisture sample obtained at 2'.

Poorly-graded SAND with gravel, fine to coarse grained, light tan, moist, subrounded.

Moisture sample obtained at 5'.

Bottom of boring SG14-15 at 5'. No groundwater encountered at time of drilling.

0.3

0.5

2.5

5.0

S A

M P

LE

R

10/1/2014

20 40

RQD (%)

WATER LEVELS

HAMMER:

WHILE DRILLING

DRILLER:

Subgrade Investigation BoringNOTES:

TOTAL DEPTH: 5'

D E

P T

H ft

RECOVERY (%)

PLASTIC LIMIT

Solid Stem Auger

STATION, OFFSET:

LATITUDE (DEGREES): N 45°0'51.12" (45.0142°)

LONGITUDE (DEGREES): W 116°3'49.032" (116.06362°)

BORING LOG (US Customary Units)

AFTER DRILLING

F ile

: Z :\P

R O

JE

C

T F

IL

E

S \2

P R

O

JE

C T

F

IL

E S

\H A

Y D

E N

P R

O

JE

C T

S \1

-3

G

W A

R R

E N

W A

G O

N R

O A

D \G

IN

T

\1

-3

G W

A R

R E

N W

A G

O N

R O

A D

.G P

J

Li b:

Z :\P

R O

JE

C

T F

IL

E

S \2

P R

O

JE

C T

F

IL

E S

\H A

Y D

E N

P R

O

JE

C T

S \1

-3

G

W A

R R

E N

W A

G O

N R

O A

D \G

IN

T

\F H

W A

L

IB

R A

R Y

.G

LB

ri nt ed : 1

1/ 4/

AT COMPLETION

G R

A P

H

IC

L O

G

DESCRIPTION

Haztech LOGGER: Kevin Funke

DATE STARTED:

0.0

0 100

BORING SG14-15

Sheet 1 of 1

COMPANY:

S A

M P

LE

DRILLING METHODS:

WATER CONTENT (%)

LIQUID LIMITFIELD

BLOW

COUNT

(Recovery)

DATE FINISHED:

0.0

0.6

1.2

1.8

2.4

3.0

3.6

4.2

4.8

5.4

6.0

FEDERAL HIGHWAY ADMINISTRATION

VANCOUVER, WASHINGTON

GEOTECHNICAL SECTION

Jason Adams

WEATHER:

DRILL: CME 75

D

E P

T H ft

10/1/2014

PROJECT: Warren Wagon Road

N/A 14" Auger

FIELD "N" VALUE

MP 8.0 5.2' R

dustin.woods Text Box D-15

4" Asphalt

Silty GRAVEL with sand (base rock), dark gray, moist, subangular.

Base rock sample obtained.

Silty SAND with gravel, fine to coarse grained, brown, moist, subrounded.

Moisture sample obtained from 6" to 12".

Moisture sample obtained at 2'.

Silty SAND with gravel, fine to coarse grained, light brown, moist

Moisture sample obtained at 5' Bottom of boring SG14-16 at 5'. No groundwater encountered at time of drilling.

0.3

0.5

2.5

5.0

S A

M P

LE

R

10/1/2014

20 40

RQD (%)

WATER LEVELS

HAMMER:

WHILE DRILLING

DRILLER:

Subgrade Investigation BoringNOTES:

TOTAL DEPTH: 5'

D E

P T

H ft

RECOVERY (%)

PLASTIC LIMIT

Solid Stem Auger

STATION, OFFSET:

LATITUDE (DEGREES): N 45°1'16.608" (45.02128°)

LONGITUDE (DEGREES): W 116°3'47.16" (116.0631°)

BORING LOG (US Customary Units)

AFTER DRILLING

F ile

: Z :\P

R O

JE

C

T F

IL

E

S \2

P R

O

JE

C T

F

IL

E S

\H A

Y D

E N

P R

O

JE

C T

S \1

-3

G

W A

R R

E N

W A

G O

N R

O A

D \G

IN

T

\1

-3

G W

A R

R E

N W

A G

O N

R O

A D

.G

Z :\P

R O

JE

C

T F

IL

E

S \2

P R

O

JE

C T

F

IL

E S

\H A

Y D

E N

P R

O

JE

C T

S \1

-3

G

W A

R R

E N

W A

G O

N R

O A

D \G

IN

T

\F H

W A

L

IB

R A

R Y nt ed : 1

1/ 4/

AT COMPLETION

G R

A P

H

IC

L O

G

DESCRIPTION

Haztech LOGGER: Kevin Funke

DATE STARTED:

0.0

0 100

BORING SG14-16

Sheet 1 of 1

COMPANY:

S A

M P

LE

DRILLING METHODS:

WATER CONTENT (%)

LIQUID LIMITFIELD

BLOW

COUNT

(Recovery)

DATE FINISHED:

0.0

0.6

1.2

1.8

2.4

3.0

3.6

4.2

4.8

5.4

6.0

FEDERAL HIGHWAY ADMINISTRATION

VANCOUVER, WASHINGTON

GEOTECHNICAL SECTION

Jason Adams

WEATHER:

DRILL: CME 75

D

E P

T H ft

10/1/2014

PROJECT: Warren Wagon Road

N/A 14" Auger

FIELD "N" VALUE

MP 8.5 5.5' L

dustin.woods

D-16

4" Asphalt

Silty GRAVEL with sand (base rock), dark brown, moist, subangular.

Base course sample obtained.

Silty SAND with gravel, fine to coarse grained, brown, moist, subrounded.

Moisture sample obtained from 6" to 12".

Clayey SAND with gravel, fine to coarse grained, dark brown, moist, subrounded.

Insufficient volume for 100 lb sample.

Moisture sample obtained at 2'.

Poorly-graded GRAVEL with silt and sand, fine to coarse grained, brown, moist, subrounded to rounded.

Moisture sample obtained at 5'.

Bottom of boring SG14-17 at 5'. No groundwater encountered at time of drilling.

0.3

0.5

1.2

2.8

5.0

S A

M P

LE

R

10/1/2014

20 40

RQD (%)

WATER LEVELS

HAMMER:

WHILE DRILLING

DRILLER:

Subgrade Investigation BoringNOTES:

TOTAL DEPTH: 5'

D E

P T

H ft

RECOVERY (%)

PLASTIC LIMIT

Solid Stem Auger

STATION, OFFSET:

LATITUDE (DEGREES): N 45°1'41.808" (45.02828°)

LONGITUDE (DEGREES): W 116°3'44.82" (116.06245°)

BORING LOG (US Customary Units)

AFTER DRILLING

F ile

: Z :\P

R O

JE

C

T F

IL

E

S \2

P R

O

JE

C T

F

IL

E S

\H A

Y D

E N

P R

O

JE

C T

S \1

-3

G

W A

R R

E N

W A

G O

N R

O A

D \G

IN

T

\1

-3

G W

A R

R E

N W

A G

O N

R O

A D

.G

Z :\P

R O

JE

C

T F

IL

E

S \2

P R

O

JE

C T

F

IL

E S

\H A

Y D

E N

P R

O

JE

C T

S \1

-3

G

W A

R R

E N

W A

G O

N R

O A

D \G

IN

T

\F H

W A

L

IB

R A

R Y nt ed : 1

1/ 4/

AT COMPLETION

G R

A P

H

IC

L O

G

DESCRIPTION

Haztech LOGGER: Kevin Funke

DATE STARTED:

0.0

0 100

BORING SG14-17

Sheet 1 of 1

COMPANY:

S A

M P

LE

DRILLING METHODS:

WATER CONTENT (%)

LIQUID LIMITFIELD

BLOW

COUNT

(Recovery)

DATE FINISHED:

0.0

0.6

1.2

1.8

2.4

3.0

3.6

4.2

4.8

5.4

6.0

FEDERAL HIGHWAY ADMINISTRATION

VANCOUVER, WASHINGTON

GEOTECHNICAL SECTION

Jason Adams

WEATHER:

DRILL: CME 75

D

E P

T H ft

10/1/2014

PROJECT: Warren Wagon Road

N/A 14" Auger

FIELD "N" VALUE

MP 9.0 7.5' R

dustin.woods

D-17