NM.FTFS.0333(1).Juan_Tabo_La_Luz.Geotech.2018.pdf

JUAN TABO AND LA LUZ ACCESS ROADS

NATIONAL FOREST SYSTEM ROUTE 333

CIBOLA NATIONAL FOREST, NM

NM FTFS 333 (1)

FINAL Geotechnical Report

Report No. NM-FX-0333-18-01

Prepared by Federal Highway Administration

Central Federal Lands Highway Division

Geotechnical Services Branch February 2018

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TABLE OF CONTENTS

SECTION ONE - INTRODUCTION

1.1 BACKGROUND AND LOCATION

1.2 SCOPE AND PURPOSE

SECTION TWO – GEOLOGY AND SEISMICITY

2.1 REGIONAL GEOLOGY

2.2 SEISMIC DESIGN PARAMETERS

2.3 GEOLOGIC HAZARDS

SECTION THREE – SUBSURFACE INVESTIGATION

3.1 SUMMARY OF SUBSURFACE CONDITIONS

3.2 RETAINING STRUCTURES

SECTION FOUR – ANALYSIS & RECOMMENDATIONS

4.1 GEO-PROFILE OF SLOPE MATERIALS

4.2 RETAINING STRUCTURES

4.2.1 Presumptive Material Parameters

4.2.2 Rockery Wall Design

4.3 SPECIFICATIONS

4.4 DISCLAIMER/LIMITATIONS CLAUSE

SECTION FIVE - REFERENCES

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TABLES

Table 1:- Summary of Nearby Faults Table 2:- Summary of Seismic Parameters Corrected for Site Class C Table 3:- Retaining Wall Design Parameters Table 4:- Rockery Wall Design Minimum Factors of Safety Table 5:- Calculated Factors of Safety at Maximum Design Height Table 6:- Recommended Geometry for Rockery Walls

FIGURES

Figure 1:- La Luz Trailhead parking lot Figure 2:- Existing cut slope and trailhead at the La Luz parking area Figure 3:- Undermining of masonry wall near south end of wall Figure 4:- Rockery Schematic and Notation for Recommended Geometry Layout

APPENDICES

APPENDIX A - Project Location and Geologic Maps APPENDIX B - Rockery Wall Analyses APPENDIX C - Special Contract Requirements file://cflcadd3.cflhd.local/projects/NM/333(1)/Geotech/7_FinalDocs/FINAL%20Geotechnical%20Report.docx#_Toc506211345 file://cflcadd3.cflhd.local/projects/NM/333(1)/Geotech/7_FinalDocs/FINAL%20Geotechnical%20Report.docx#_Toc506211346 file://cflcadd3.cflhd.local/projects/NM/333(1)/Geotech/7_FinalDocs/FINAL%20Geotechnical%20Report.docx#_Toc506211347 file://cflcadd3.cflhd.local/projects/NM/333(1)/Geotech/7_FinalDocs/FINAL%20Geotechnical%20Report.docx#_Toc506211348

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NFSR 333 NM FTFS 333 (1) February 2018

SECTION ONE - Introduction

1.1 BACKGROUND AND LOCATION

This report presents the results of the geotechnical engineering assessment and provides recommendations for the reconstruction and rehabilitation work to be performed on 1.8-mile long section along National Forest System Route (NFSR) 333. The project is located in the Sandia Ranger District of the Cibola National Forest, northeast of Albuquerque, New Mexico. The project begins at Station 10+00, approximately 0.2 miles northeast of the intersections with Tramway Road, at an elevation of approximately 6,050 feet. The route climbs northeast towards the Juan Tabo picnic sites and the La Luz Trailhead, and terminates at the trailhead parking lot at an approximate elevation of 7,030. The route is generally located within undeveloped desert, scrubland, and forest and serves as the access road to private residences and recreational facilities.

A site map is presented on Figure A-1 of this report.

Recreational facilities accessed by this route include the La Cueva, La Luz, and Piedra Lisa South Trailheads and the La Cueva and Juan Tabo Picnic Sites. The overall objective of this project is to rehabilitate the roadway conditions and to improve safety for the recreating public. The existing route is characterized as a narrow two-lane thoroughfare with some sharp switchbacks and relatively steep grades. The roadway traverses mountainous terrain with most cuts excavated in either colluvium soils or granitic bedrock and side cast embankments to provide two 10-foot wide asphalt paved lanes with one-foot shoulders that pass through forest, shrub land, and desert habitat.

The La Luz Trailhead parking lot is often at capacity, especially during the fall and winter months.

When the parking lot is full, visitors often park along the shoulder of the road, creating significant roadside safety hazards. Other hazards include edge drop-offs and inadequate signage and striping.

An inadequate drainage area was identified at the intersection of NFSR 333 and NFSR 333A, which causes frequent inundation and sedimentation on the roadway.

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To improve the trailhead parking lot capacity, an approximate 220-feet long by 12-feet high retaining structure is proposed along the north and east sides of the lots (see Figure 1). In addition to improving capacity, the proposed parking lot reconstruction is expected to improve traffic flow and reduce congestion compared to the current layout.

1.2 SCOPE AND PURPOSE

The scope of work included geotechnical investigation, analysis, and recommendations of retaining structures within the project limits for use in design and construction. This involved several tasks including field reconnaissance, interpretation and correlation of field measurements, and geotechnical engineering analysis. Specifically, this investigation is to estimate the soil profiles at the retaining structure location and develop recommendations concerning structure type and dimensions, material shrink/swell, and construction considerations for the design and construction of retaining structures at the La Luz Trailhead parking lot. Due to the limited scope of geotechnical improvements, this report is limited to discussion of the La Luz Trailhead parking lot. The stationing in this report is based on the preliminary 70 percent project plans, dated November 7, 2017.

Figure 1:- La Luz Trailhead parking lot.

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SECTION TWO – Geology and Seismicity

2.1 REGIONAL GEOLOGY

The project is located within the Sandia Mountain Range on the eastern edge of the Rio Grande Rift Valley. The core of the range is comprised of Precambrian rocks (approximately 1.8 billion to 540 million years old) at its core and younger sedimentary along its flanks. The principal mapped surficial deposits are piedmont alluvium (Read et al, 2000). The La Luz Trailhead parking lot is mapped as underlain by piedmont alluvium. The alluvium is described as a moderately consolidated gravel and sand with minor silty-clay interbeds. The alluvium is underlain by Sandia Granite, which is described as a coarse-grained biotite monzogranite to granodiorite. A map of the regional geology is presented in Figure A-2.

Several known Quaternary faults are mapped within approximately 40 miles of the parking and are summarized on Table 1 below (U.S. Geological Survey, 2017).

Table 1:- Summary of Nearby Faults

FAULT OR FAULT

ZONE

DISTANCE

FROM CENTER

OF PROJECT

FAULT

PARALLEL

SLIP RATE

FAULT

LENGTH AGE

(miles) (inch/year) (miles) (years)

San Francisco fault 4.68 0.0055 17.4 <1,600,000

Tijeras-Canoncito fault 9.06 0.0039 50.3 <130,000

San Felipe fault zone 9.53 0.0024 26.7 <1,600,000

East Paradise fault zone 11.34 0.0004 8.1 <130,000

Hubbell Springs fault 15.59 0.0055 28.0 <15,000

County Dump fault 16.73 0.0020 23.0 <130,000

La Bajada fault 17.4 0.0039 26.1 <1,600,000

Zia fault 18.92 0.0020 20.5 <15,000

Calabacillas fault 20.9 0.0004 20.5 <15,000

Nacimiento fault 28 0.0012 51.6 <750,000

Pajarito fault 30.77 0.0039 31.1 <15,000

Pojoaque fault 38.82 0.0012 29.8 <1,600,000

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2.2 SEISMIC DESIGN PARAMETERS

The American Association of State Highway and Transportation Officials (AASHTO) criteria for Recommended seismic response parameters are based on AASHTO LRFD Bridge Design Specifications, 7th Edition, 2014, and represents horizontal peak ground acceleration (PGA) with 7 percent probability of exceedance in 75 years (approximate 1000-year return period). The 1000-year return period uniform hazard spectrum for NFSR 333 (35.21965º N latitude and -106.48096º W longitudes) was obtained in accordance with the AASHTO ground motion maps. The site was classified as “Class C” according to site class definitions specified in Table 3.10.3.1-1 of AASHTO and soil profile assumptions based on rock outcrops at the site and geologic mapping of the project vicinity. The recommended spectral acceleration coefficient values for probabilistic design are summarized in the following table.

Table 2:- Summary of Seismic Parameters Corrected for Site Class C

Peak Seismic Ground Acceleration Coefficient, (As) 0.172 Horizontal Response Spectral Acceleration at Period of 0.2 sec, (SDS) 0.407 Horizontal Response Spectral Acceleration at Period of 1.0 sec (SD1) 0.168

Site Factor at Zero-Period of Acceleration Spectrum, (Fpga) 1.2 Site Factor at Short-Period of Acceleration Spectrum, (Fa) 1.2

Site Factor at Long-Period Range of Acceleration Spectrum, (Fv) 1.7

Based on the long acceleration coefficient SD1 value of 0.168, the site is assigned to seismic hazard Zone 2 in accordance with Table 3.10.6-1 of AASHTO.

2.3 GEOLOGIC HAZARDS

The La Luz Trailhead parking area is constructed on piedmont alluvium and decomposed granite materials. These materials are susceptible to erosion. Any areas disturbed during construction should be stabilized to prevent significant loss of soil and damage to adjacent structures.

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SECTION THREE – Subsurface Investigation

3.1 SUMMARY OF SUBSURFACE CONDITIONS

A subsurface investigation targeting the proposed retaining structure area was not performed for this scope of work. Observations and surficial evaluation and mapping was performed based on areas identified during project scoping. Prior to initiating wall construction, the Contractor should excavate test pits within or near the proposed wall alignment in order to verify the assumptions made in this report.

3.2 RETAINING STRUCTURES

Existing cutslope conditions were visually evaluated near the proposed retaining structure location (Figure 2). The evaluation was conducted to assess the stability of existing slopes and to design optimum retaining structures to meet slope retention and aesthetic requirements for parking lot expansion. Existing cutslopes extend to a height of approximately 8 feet with evidence of some minor erosion. Cut-slopes in soil adjacent to the parking area generally vary between 18 to 21 degrees from horizontal while naturally occurring slopes are typically between 10 and 15 degrees.

Figure 2:- Existing cut slope and trailhead at the La Luz parking area.

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Free-standing rubble masonry walls are present adjacent to the parking area (Figure 3). The walls are approximately 3 feet high and are in good to fair condition. Local undermining of the wall foundation was noted at one location along the walls; however, no other distress such as sliding or rotation is noted in this area. These walls are within the footprint of the proposed parking lot expansion and will be removed.

Visual inspection of slopes, along with geological knowledge provided the means for evaluating slope stability. In general, slopes with smooth contours indicated that the slopes have been formed by surface erosion processes without slip movement. On the other hand, irregular surfaces with stair stepping contours, scarp lines, slopping trees, or changes of vegetation indicated slope slumping. The existing cutslopes adjacent to the parking lot appeared to be in stable condition meeting the required factor of safety for low volume roads.

Figure 3:- Undermining of masonry wall near south end of wall.

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SECTION FOUR – Analysis & Recommendations

This section presents analysis and recommendations pertaining to retaining structures. In addition, this section provides general interpretation of visual site reconnaissance. Generalized subsurface profiles were developed based on field reconnaissance and surficial visual evaluation. No subsurface investigations were performed. Design parameters are based on presumptive values for similar materials. Based on the required retaining structure size, project scope, and desired aesthetic finish, a rockery wall is anticipated at the La Luz Trailhead parking lot (Station 124+50 to Station 126+17). The remainder of the project is anticipated to follow the existing roadway footprint. As previously discussed, field reconnaissance was confined to the immediate vicinity of the La Luz Trailhead parking lot.

4.1 GEO-PROFILE OF SLOPE MATERIALS

Soil deposits encountered along the proposed retaining structure alignment were mostly of colluvial or alluvial origin and are characterized for design purposes as a mixture of silty sand and gravel with varying sizes of cobbles and boulders. The slope materials are generally formed by the weathering and eroding process of granitic bedrock. The materials are considered to have high friction angle and low cohesion which is a good quality material for retaining structure construction. The overburden slope materials are, however, susceptible to water infiltration and will require drainage methods to be incorporated into the retaining structure design.

The natural soils are highly permeable and are likely to be heterogeneous in nature. The soil profile consists of zones of partially weathered bedrock material containing remnants of the parent rock (boulders) of varying sizes, and zones of fully weathered material (soil). Boulders up to 10 feet in diameter were observed at the ground surface near the proposed retaining wall location. Since no subsurface exploration was performed, prior to wall construction, the Contractor should excavate test pits within or near the proposed retaining wall alignment to verify the assumptions made in this section. Specifically, the test pits should be excavated to verify the quantity of rock suitable for rockery constructions, on-site soil properties, and overall difficulty of excavations.

4.2 RETAINING STRUCTURES

Based on the existing grading and proposed parking lot layout, retaining structures are required to reduce the total excavation and impacts to the local environment. The required grade separation is estimated to be approximately 6.5 feet. The proposed rockery wall will be approximately 235 feet long, starting at mainline Station 124+50 and extending to secondary alignment Station 300+58.

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Based on the required grade separation and a preference for a natural appearance, rockery retaining walls are recommended for this application.

4.2.1 Presumptive Material Parameters

Based on the limited field reconnaissance and visual classification of the on-site soils, the estimated material parameters used in design are summarized in Table 3. Excavation for the wall may provide suitable rockery material. For estimation purposes, 20 percent of the materials produced from excavation will be suitable, with processing, as rock for rockery walls.

Table 3:- Retaining Wall Design Parameters

1) Cohesion of rockery rock was artificially inflated to simulate assumed rigidity of a properly constructed rock face.

The design for the rockery wall was checked for adequate factors of safety against sliding, overturning, bearing capacity, and global stability. The recommended factors of safety for static and seismic design are presented in Table 4 below (FHWA, 2006).

Table 4:- Rockery Wall Design Minimum Factors of Safety

MATERIAL TYPE UNIT WEIGHT

γ (pcf)

FRICTION ANGLE

φ (deg)

COHESION

INTERCEPT

c (psf) Retained Soils 125 34 0

Foundation Soils 125 36 0 Rock for Rockery 150 40 5001

MODE OF FAILURE STATIC FACTOR OF

SAFETY

SEISMIC FACTOR OF

SAFETY

Sliding 1.5 1.1 Overturning 2.0 1.5

Bearing 3.0 2.0 Global Stability 1.3 1.1

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4.2.2 Rockery Wall Design

Rockeries are earth retaining structures constructed of large interlocking, dry-stacked rocks, typically placed without mortar or reinforcement. These structures rely on the weight, size, shape, and interface friction of the individual rocks to resist earth pressures and provide overall stability.

Rockeries have been utilized on many projects as context sensitive solutions preserving scenic, aesthetic, historic, and environmental resources.

The rockery wall was designed in accordance with the guidelines provided in FHWA (2006). The rockery was designed as a gravity retaining wall with a backslope based on the proposed grading plan. Static and seismic lateral earth pressures were applied to the back of the rockery; however, passive earth pressure was neglected at the toe of the wall. Calculated factors of safety at the maximum design height (8 feet) are presented in Table 5. The recommended geometry of the rockery wall and an explanatory figure are presented in Table 6 and Figure 4. Results of the rockery design calculations are presented in Appendix B.

Table 5:- Calculated Factors of Safety at Maximum Design Height

Table 6:- Recommended Geometry for Rockery Walls

MAXIMUM

HEIGHT

H, ft

MINIMUM

BASE

WIDTH

B, ft

EMBEDMENT

DEPTH AT

TOE

D, ft

BACKSLOPE

ANGLE

β, degrees

WALL

FACE

BATTER

V:H

BACK CUT

INCLINATION

α, V:H

8 5.0 1.5 26.6 4:1 8:1 6 4.0 1.5 26.6 4:1 8:1

MODE OF FAILURE STATIC FACTOR OF

SAFETY

SEISMIC FACTOR OF

SAFETY

Sliding 2.2 1.2 Overturning 5.0 2.2

Bearing 17.5 9.8 Global Stability 1.5 1.3

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4.3 SHRINK/SWELL RECOMMENDATIONS

The proposed Juan Tabo trailhead parking lot will require cut slopes and retaining walls to accommodate the proposed parking area footprint. This will require excavation in the native silty to clayey sand soils. As previously discussed, the soils contain varying quantities of gravel, cobbles, and boulders, with boulders up to 10-foot diameter noted at the surface.

For the purpose of estimating shrink/swell values, silty to clayey sands are assumed to be the predominate material located in permanent cut areas. The recommended shrink/swell factors are based on a combination of standard tabled values for common materials in the FLH Technical Guidance Manual (2006) and experience with other CFLHD projects in similar materials.

The estimated shrink/swell values the silty to clayey sand with gravel, cobbles, and boulders of the cut slopes are assumed to Swell 10 percent (Swell Factor 1.10) if wasted without tight density control during placement.

Figure 4:- Rockery Schematic and Notation for Recommended Geometry Layout

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4.4 SPECIFICATIONS

Special provisions were developed to be consistent with geotechnical recommendations stated above and should be incorporated into the special contract requirements (SCR). The following SCR’s were added for this project:

Section 252 – Rockery and Special Rock Embankment

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4.4 DISCLAIMER/LIMITATIONS CLAUSE

Subsurface exploration was not performed as a part of this scope of work. Interpretation of surface and subsurface conditions is based on limited field reconnaissance and surface mapping of soil and rock outcrops. The Analysis and Recommendations Section in this report includes interpretations and recommendations developed by the Government in the process of preparing the design. These interpretations are not intended as a substitute for the personal investigation, independent interpretation, and judgment of the Contractor.

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SECTION FIVE - References

American Association of State Highway and Transportation Officials (AASHTO). “AASHTO LRFD Bridge Design Specifications.” Seventh Edition, 2014.

Read, A.S., Karlstrom, K.E., Connell, S., Kirby, E., Ferguson, C.A., Ilg, B., Osburn, G.R., Van Hart, D., and Pazzaglia, F.J. (2000). “Geology of Sandia Crest quadrangle, Bernalillo and Sandoval Counties, New Mexico,” 1:24,000. NMBMMR Open File Map Series, Map OF-GM-6. Socorro, NM: New Mexico Bureau of Mines and Mineral Resources, U.S. Department of Transportation, Federal Highway Administration (FHWA). (2014). “Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects, FP-14.”

Publication No. FHWA-FLH-14-001.

U.S. Department of Transportation, Federal Highway Administration (FHWA), Central Federal Lands Highway Division. (2006). “Rockery Design and Construction Guidelines.” Publication No. FHWA-CFL/TD-06-006.

U.S. Geological Survey (2017). “Quaternary Fault and Fold Database of the United States.” USGS Earthquake Hazards Program, <http://earthquake.usgs.gov/hazards/qfaults/>

U.S. Geologic Survey (2017). “U.S. Seismic Design Maps.” USGS Earthquake Hazards Program, <http://earthquake.usgs.gov/designmaps/us/application.php>

Juan Tabo La Luz NM FLAP 333(1) February 2018

APPENDIX A Project Location and Geology Maps

APPENDIX B Rockery Wall Analyses

Project: Juan Tabo La Luz (NM FLAP 333(1)) Units: US Project Name: Juan Tabo La Luz Project Number: NM FLAP 333(1) Company Name: FHWA-CFL Location: Lakewood, CO Map Coordinates: 35.219649, -106.480960 Designer: JMA Reviewer: KYH Project Date: 1/10/2018

Geometry Rockery Wall Geometry Value Unit H Rockery height, total 8 ft Hr Rockery height, exposed 6.5 ft D Embedment depth at toe of rockery 1.5 ft B Base rock width 5 ft Df Depth of soil to neglect for passive resisting force 1.5 ft β Retained ground surface inclination ("backslope") 26.6 deg

Face Face Ratio: 1/Face 4 Backcut Backcut Ratio, 1/Backcut 8 α {a} = tan^-1_(Backcut) 82.9 deg ψ {y} = 90 - {a} 7.13 deg qs Vertical surcharge on surface behind rockery 0 pcf γR Unit weight of rockery facing (net density, including voids) 150 pcf

Soil Soil Parameters γs Unit weight of retained soil 125 pcf φ Soil friction angle / angle of internal friction 34 deg δ {s} = 2/3{f} 22.7 deg C Effective cohesion for soil beneath foundation 0 psf φf Friction angle of foundation soil and soil at toe of rockery 36 deg μ Allowable sliding friction factor 0.484 γ Effective unit weight for soil beneath foundation 125 pcf φBC Foundation soil friction angle 36 deg

Seismics Seismic Parameters A Peak Ground Acceleration 0.172 g Kh Horizontal seismic coefficient 0.086 g Kv Vertical seismic coefficient 0 g

Page B‐1 of B‐8 NM FTFS 333(1) February, 2018

Coefficients Rockery Wall Output Coefficients K_a Lateral earth pressure coefficient 0.32 FH Total horizontal force 114.7 pcf W Wall weight 5.2 kip/ft Fμ Frictional Resistance 2.7 kip/ft Fp Passive Frictional Resistance 0.0 kip/ft Mo External moment overturning 3.3 kip-ft/ft Mr External moment overturning resistance 16.4 kip-ft/ft Nq Bearing capacity factor 37.8 Nc Bearing capacity factor 50 Nγ Bearing capacity factor 50

Height (ft) Internal Overturning Checks

1.50 Factor of safety at corresponding height 6.2

2.15 Factor of safety at corresponding height 7.1

2.80 Factor of safety at corresponding height 8.3

3.45 Factor of safety at corresponding height 9.9

4.10 Factor of safety at corresponding height 12.3

4.75 Factor of safety at corresponding height 16.1

5.40 Factor of safety at corresponding height 22.8

6.05 Factor of safety at corresponding height 36.3

6.70 Factor of safety at corresponding height 72.6

7.35 Factor of safety at corresponding height 255.9

Page B‐2 of B‐8 NM FTFS 333(1) February, 2018

More Coefficients Rockery Wall Output Coefficients e Check: Eccentricity (e) less than B/6 0.04

Qmax Maximum applied bearing pressure at toe of base rock due to moment eccentricity 1.29 ksf

Qult Terzaghi bearing capacity 22.7 ksf Qmaxs Maximum applied seismic bearing pressure 2.31 ksf Kae Seismic earth pressure coefficient 0.479 FA Lateral surcharge pressure 1.3 kip/ft FAE Seismic surcharge pressure 1.9 kip/ft ΔFAE Delta seismic surcharge pressure 0.6 kip/ft

Factors of Safety Rockery Wall Factors of Safety FSsl Factor of safety with respect to base sliding, > 1.5, OK 2.2

FSot Factor of safety with respect to external overturning, > 2, OK 5.0

FSbc Factor of safety with respect to bearing capacity, > 2.5, OK 17.5

FSint,ot Factor of safety with respect to internal (inter-rock) overturning, > 2, OK

6.2

Hint,ot Height of minimum factor of safety of internal (inter-rock) overturning 1.5 ft

FSsl,s Factor of safety with respect to base seismic sliding, > 1.125, OK 1.2

FSot,s Factor of safety with respect to external seismic overturning, > 1.5, OK

2.2

FSbc,s Factor of safety with respect to seismic bearing capacity, > 1.875 (p.

75), OK

9.8

FSseismic Factor of safety against wall movement due to seismic activity, 1.4

Page B‐3 of B‐8 NM FTFS 333(1) February, 2018

Static Global Stability Analysis Scale Range for factor of safety color scale 0.0,5.0

Center Center of minimum factor of safety failure circle -0.3,18.8 ft Radius Radius of minimum factor of safety failure circle 19.8 ft

FoS Global Minimum factor of safety 1.59

Seismic Global Stability Analysis Scale Range for factor of safety color scale 0.0,5.0

Center Center of minimum factor of safety failure circle -0.7,19.4 ft Radius Radius of minimum factor of safety failure circle 20.5 ft

FoS Global Minimum factor of safety 1.37

Page B‐4 of B‐8 NM FTFS 333(1) February, 2018

Project: Juan Tabo La Luz (NM FLAP 333(1)) Units: US Project Name: Juan Tabo La Luz Project Number: NM FLAP 333(1) Company Name: FHWA-CFL Location: Lakewood, CO Map Coordinates: 35.219649, -106.480960 Designer: JMA Reviewer: KYH Project Date: 1/10/2018

Geometry Rockery Wall Geometry Value Unit H Rockery height, total 6 ft Hr Rockery height, exposed 4.5 ft D Embedment depth at toe of rockery 1.5 ft B Base rock width 4 ft Df Depth of soil to neglect for passive resisting force 1.5 ft β Retained ground surface inclination ("backslope") 26.6 deg

Face Face Ratio: 1/Face 4 Backcut Backcut Ratio, 1/Backcut 8 α {a} = tan^-1_(Backcut) 82.9 deg ψ {y} = 90 - {a} 7.13 deg qs Vertical surcharge on surface behind rockery 0 pcf γR Unit weight of rockery facing (net density, including voids) 150 pcf

Soil Soil Parameters γs Unit weight of retained soil 125 pcf φ Soil friction angle / angle of internal friction 34 deg δ {s} = 2/3{f} 22.7 deg C Effective cohesion for soil beneath foundation 0 psf φf Friction angle of foundation soil and soil at toe of rockery 36 deg μ Allowable sliding friction factor 0.484 γ Effective unit weight for soil beneath foundation 125 pcf φBC Foundation soil friction angle 36 deg

Seismics Seismic Parameters A Peak Ground Acceleration 0.172 g Kh Horizontal seismic coefficient 0.086 g Kv Vertical seismic coefficient 0 g

Page B‐5 of B‐8 NM FTFS 333(1) February, 2018

Coefficients Rockery Wall Output Coefficients K_a Lateral earth pressure coefficient 0.32 FH Total horizontal force 64.5 pcf W Wall weight 3.2 kip/ft Fμ Frictional Resistance 1.7 kip/ft Fp Passive Frictional Resistance 0.0 kip/ft Mo External moment overturning 1.4 kip-ft/ft Mr External moment overturning resistance 7.9 kip-ft/ft Nq Bearing capacity factor 37.8 Nc Bearing capacity factor 50 Nγ Bearing capacity factor 50

Height (ft) Internal Overturning Checks

1.50 Factor of safety at corresponding height 7.8

1.95 Factor of safety at corresponding height 9.0

2.40 Factor of safety at corresponding height 10.5

2.85 Factor of safety at corresponding height 12.7

3.30 Factor of safety at corresponding height 16.0

3.75 Factor of safety at corresponding height 21.1

4.20 Factor of safety at corresponding height 30.1

4.65 Factor of safety at corresponding height 48.7

5.10 Factor of safety at corresponding height 98.7

5.55 Factor of safety at corresponding height 353.2

Page B‐6 of B‐8 NM FTFS 333(1) February, 2018

More Coefficients Rockery Wall Output Coefficients e Check: Eccentricity (e) less than B/6 0.03

Qmax Maximum applied bearing pressure at toe of base rock due to moment eccentricity 0.98 ksf

Qult Terzaghi bearing capacity 19.58 ksf Qmaxs Maximum applied seismic bearing pressure 1.67 ksf Kae Seismic earth pressure coefficient 0.479 FA Lateral surcharge pressure 0.7 kip/ft FAE Seismic surcharge pressure 1.1 kip/ft ΔFAE Delta seismic surcharge pressure 0.4 kip/ft

Factors of Safety Rockery Wall Factors of Safety FSsl Factor of safety with respect to base sliding, > 1.5, OK 2.4

FSot Factor of safety with respect to external overturning, > 2, OK 5.7

FSbc Factor of safety with respect to bearing capacity, > 2.5, OK 20.0

FSint,ot Factor of safety with respect to internal (inter-rock) overturning, > 2, OK

7.8

Hint,ot Height of minimum factor of safety of internal (inter-rock) overturning 1.5 ft

FSsl,s Factor of safety with respect to base seismic sliding, > 1.125, OK 1.3

FSot,s Factor of safety with respect to external seismic overturning, > 1.5, OK

2.4

FSbc,s Factor of safety with respect to seismic bearing capacity, > 1.875 (p.

75), OK

11.7

FSseismic Factor of safety against wall movement due to seismic activity, 1.5

Page B‐7 of B‐8 NM FTFS 333(1) February, 2018

Static Global Stability Analysis Scale Range for factor of safety color scale 0.0,5.0

Center Center of minimum factor of safety failure circle 0.0,15.1 ft Radius Radius of minimum factor of safety failure circle 16.1 ft

FoS Global Minimum factor of safety 1.78

Seismic Global Stability Analysis Scale Range for factor of safety color scale 0.0,5.0

Center Center of minimum factor of safety failure circle 2.0,16.2 ft Radius Radius of minimum factor of safety failure circle 16.5 ft

FoS Global Minimum factor of safety 1.51

Page B‐8 of B‐8 NM FTFS 333(1) February, 2018

APPENDIX C Special Contract Requirements

Section 252. – ROCKERY, SPECIAL ROCK EMBANKMENT, AND ROCK

BUTTRESS

Description

252.01 Delete the text and substitute the following:

This work consists of constructing rockeries. Rockeries are formed of interlocking, dry-stacked rocks without reinforcing steel, mortar, or concrete. Rockeries may be constructed as either single structures or in tiers.

This work also consists of constructing special rock embankment and rock buttresses. Special rock embankments and rock buttresses are designated as hand-placed or mechanically-placed.

Rock embankment consists of furnishing and placing hand-placed or mechanically-placed rock in fill sections. Rock buttress work consists of furnishing and placing hand-placed or mechanically-placed rock in cut sections.

Material

252.02 Add the following:

Plastic pipe 708.04

Construction Requirements

252.03 Rockery. Add the following:

Prior to the start of rockery construction submit the experience of the primary equipment operator responsible for placement of base, facing, and cap rocks.

(a) Excavation. Delete the text and substitute the following: Prior to rockery construction, excavate 3 test pits within or near the proposed wall footprint to confirm subsurface conditions as outlined in the Geotechnical Report. Perform production excavation work under Sections 204 and 209 as required. Do not excavate more areas for rockeries than can be replaced with rockery construction in one shift unless shoring is provided or as approved by the CO. Allow CO or designated representative to inspect excavations prior to rockery construction. Protect backslopes from damage by surface water.

(b) Erection. Add the following after the third paragraph:

Avoid placing rocks which have shapes that create voids with a linear dimension greater than 12 inches.

Measurement

252.06 Delete the second paragraph and add the following to the second paragraph:

Structure excavation, granular rock backdrain, foundation fill, drainage pipes (perforated and non-perforated), geotextile, and grout for choking rocks will not be measured for payment and are considered incidental to the rockery.

Table 252-1. Delete table and substitute the following:

Table 252-1 Sampling, Testing, and Acceptance Requirements

Material or Product

(Subsection)

Type of Acceptance (Subsection)

Characteristic Category Test Methods Specifications

Sampling Frequency

Point of Sampling

Split Sample

Reporting Time

Remarks

Source Rock for buttresses (705.05)

Measured and tested for conformance

(106.04 & 105)

Rock breadth and thickness

− Subsection 705.05(a)(1)

1 per rock type

Source of material

No Before using in work

Apparent specific gravity

− AASHTO T 85 " " Yes " Not required when using Government

-provided source

Absorption − " " " " " "

Rock for rockeries (705.06)

" Apparent specific gravity

− " 1 per rock type

Source of material

Yes Before using in work

Not required when using Government

-provided source

Absorption − " " " " " "

LA abrasion − AASHTO T 96 " " " " "

Soundness using sodium sulfate

− AASHTO T

Rock for special rock embankment

(705.04)

Process control

(153.03)

Size − See Note (1) 1 per 100 yd3 (80 m3)

In-place No 24 hours

Rock for buttresses (705.05)

" " − " 1 per 100 yd3 (80 m3)

(1) For mechanically placed embankments, verify rock size by confirming that the largest accessible rock has an intermediate dimension greater than the D50 size specified in Table 705-2. Also confirm that the smallest accessible rock has an intermediate dimension within the lower D50 size range specified in Table 705-2.

For hand placed embankments, verify rock size by confirming that the largest accessible rock has an intermediate dimension greater than the D75 size specified in Table 705-3. Also confirm that the smallest accessible rock has an intermediate dimension within the D25 size range specified in Table 705-3.