Geotechnical Report - AC-831579_Hwy-140.pdf

GEOTECHNICAL REPORT

LANDSLIDE AND ROAD DAMAGE EVALUATION

AND REPAIR RECOMMENDATIONS

PR-128 KM 54.77, LARES, PR

ER-HWY-140

AC-809544

Submitted to:

José A. Batlle Montalvo, PE

José A. Batlle y Asociados, CSP

Prepared by:

Rommel Cintrón Aponte, MSCE, PE

Date:

March 4, 2019

Revision:

December 17, 2021

Job no. 7962

P

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B o x

S a n

J u a n

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Geotechnical Report: Site ER HWY 140

Landslide and Road Evaluation and Repair Recommendations PR 128 KM 54.77, Lares, PR

J a c a & S i e r r a E n g i n e e r i n g , P S C

P O B o x 3 6 3 1 1 6 , S a n J u a n , P R 0 0 9 3 6 - 3 1 1 6

R o a d 8 5 0 K m 0 . 2 L a s C u e v a s W a r d , T r u j i l l o A l t o , P R 0 0 9 7 6

T . ( 7 8 7 ) 7 6 1 - 2 5 7 0 w w w . j a c a s i e r r a . c o m

1. Introduction:

The present geotechnical report addresses the geotechnical conditions and recommendations for the road damages at the reference site location. This investigation is prepared based on approved scope of work and economical proposal by José A. Batlle y Asociados, CSP. This report is part of a multiple site assessment project for similar landslide rehabilitation cases related to damages by Hurricane Maria on September 20, 2017. This report is prepared exclusively for design purposes.

2. Scope of Work:

The scope of work consisted of two (2) test borings to 6.3 mts (20.5 ft) depth. Borings were completed with CME-45 drill rig at accessible locations on the side of the road. Test borings and soil sampling were performed by casing installation in accordance to ASTM

D1452 and soil sampling per Standard Penetration Test (SPT) method per ASTM D1586.

Refer to enclosed boring location plan for reference on boring location in Appendix A

Figure A2. The area of the landslide was not accessible for performing test borings with portable equipment due to existing debris and safety hazards on the slope surface.

3. Site Geology:

Based on the USGS Geology Map (refer to Appendix A Figure A1) the site’s predominant geologic formation is Tmi – Milagros Formation. Tmi is described as medium-gray feldspathic lapilli tuff and dark-brownish-gray volcanic breccia with interbedded bluish-gray fine-grained andesite lava, and brownish-gray, bedded vitric and crystal tuff, volcanic sandstone and siltstone.

Site ER HWY 140

PR 128 KM 54.77, Lares, PR

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1 2 / 1 7 / 2 1 Jaca & Sierra Engineering, PSC

t. (787) 761-2570 e. contact@jacasierra.com www.jacasierra.com

4. Site Stratigraphy:

Stratum no. 1: Fill: The upper fill stratum has thicknesses of 1.2 to 2.7 mts (4 to 9 ft). The fill material consists of sandy gravel with asphalt debris within the upper 2 feet and sandy clay with some gravel below 2 feet. SPT-N values recorded are varying from 5 to 38 blows/ft. Moisture contents measured are from 8 to 46 %.

Stratum no. 2: Saprolite: The above described fill layer overlays saprolitic soils composed of clayey silt with some sand and traces of weathered rock fragments in the lower horizon from the above-mentioned Milagros Formation extending to the end of boreholes at 6.3 mts (20.5 ft) depth. SPT-N values registered are ranging from 13 to 53 blows/ft. Moisture contents obtained are from 23 to 33 %.

4.1. Groundwater:

Groundwater level was not detected within the depth range of the test borings.

Temporary localized perched water may occur after prolonged rain events.

5. Geotechnical Recommendations:

5.1. Opinion on Probable Causes for Road Damage:

It is our opinion that the apparent cause of failure is related to a shallow landslide of fill material and native saprolitic soils occurring by erosion from overland runoff during storm event. The slide can be described as a soil washout. At the time of our site visit on

January 15, 2019, the landslide was covered with vegetation and dumped soils.

5.2. Slope Rehabilitation Alternatives:

5.2.1. Gabion Wall:

A gabion wall is favorable for this site due to its inherent ability to drain any water or moisture trapped in the backfill. The base width will be wider if compared to a concrete mailto:contact@jacasierra.com

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1 2 / 1 7 / 2 1 cantilever or gravity wall. Also, this type of wall will require an offset from the guard rails or concrete barrier at the edge of road. Therefore, it will project further in to the slope and thus result in more height required if compared to the concrete wall options.

This option shall be evaluated by design verification of different section profiles to be made along the extent of the project to evaluate the wall height variations. The wall shall be embedded at least 1.8 mts (6 ft) below slope surface as measured from the lower side.

This will result in a wall height of 6.3 mts (21 ft) at the highest location. When designing this option, it will be important to have measures to prevent water from infiltrating into the wall from the road side. A perforated pipe drain shall be included in the backfill to allow drainage of any water that accumulates on the backside of the wall or that infiltrates thru the wall. These details are well covered in PRHTA standard drawings.

5.2.2. Concrete Cantilever Retaining Wall:

This option has the advantage that it can be built right on the edge of the road as a concrete barrier extension (typical PRHTA section). The closer the retaining wall is to the roadway edge the less the retaining wall height required. This option shall include leveling the remaining slope to uniform inclination and armoring with turf reinforcement the deep-rooted vegetation such as vetiver. The wall shall be embedded at least 1.8 mts

(6 ft) below slope surface as measured from the lower side. With this requirement it is estimated that the retaining wall height will be 4.6 mts (15 ft) at the highest location.

5.2.3. Concrete Gravity Wall:

The concrete gravity wall option has the advantage of minimizing excavation width at the edge of the road. The gravity wall can be designed per PRHTA’s standard design section to be verified and adjusted by designer based on the herein provided bearing capacity and earth pressure parameters. The wall shall be embedded at least 1.8 mts (6

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1 2 / 1 7 / 2 1

ft) below slope surface as measured from the lower side. With this requirement it is estimated that the retaining wall height will be 4.6 mts (15 ft) at the highest location.

5.2.4. Anchored Gabion Wall:

Anchored gabion walls are an alternative to reduce the wall width requirements in conventional gabion walls. The anchor can be designed assuming allowable bond strength of 25 psi for non-shrink grout with over 5,000 psi strength. A minimum free length of 10 ft shall be considered. We recommend a minimum of 2 verification tests and proof tests on 5 % of the installed soil nails or anchors. Anchor testing shall be per Soil

Nail Walls Reference Manual FHWA NHI-14-007 February 2015. Similar to the previous explained alternatives, the slopes shall be excavated and leveled to improve their stability to the extent that the toe of the wall remains embedded 1.8 mts (6 ft).

Figure 1: Anchored gabion schematic concept (not to scale)

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5.3. Earth Pressure Parameters for Retaining Wall Design:

Strength or Earth Pressure Parameters

Engineered Fill /

Retaining Wall

Backfill

In-Situ Soils

Drained cohesion, c, kPa (psf) 0 (0) 12.0 (250)

Drained angle of internal friction, φ, ˚ 32 26

Undrained cohesion, c, kPa (psf) - 35.9 (750)

Undrained angle of internal friction, φ, ˚ - 0

Moist unit weight, γ, kN/cu.mt. (pcf) 20.4 (130) 18.9 (120)

Seismic horizontal coefficient, kh - 0.2

Base shear coefficient, * - 0.3

Net allowable bearing capacity for retaining wall over native soil, qa, kPa (psf)

- 95.8 (2,000)

Table 1: Earth pressure parameters for retained soils (neglect passive resistance)

It is our opinion that the above recommendations will stabilize the slope against global stability concerns. Other options such as soil nailing with shotcrete were discarded due to cost concerns and the fact that the edge of road was lost and a retaining wall is required to allow re-building the road to its original alignment. MSE walls or slopes will not work on this site due to limitations of space and steepness of the slope which will not allow for creating of suitable base and placement of soil reinforcements into the cut without having to excavate almost the entire road width. If any other option is wished to be considered, we should be provided with the information on the alternative to provide specific recommendations for that option. Also note that the recommended wall heights are based on interpretation of landslide plane depths that need to be confirmed during excavation process. Adjustments to these wall heights may be required.

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5.4. Global Stability Analysis Results

Soil

Condition Seismic Coefficient

Minimum Factor of Minimum Factor of

Safety Obtained Safety Required

Drained None (Static) 1.919 1.500

Drained Horizontal (Pseudostatic) 1.331 1.125

Undrained None (Static) 2.247 1.500

Undrained Horizontal (Pseudostatic) 1.607 1.125

Table 3: Summary of global stability analysis results

GEO-SLOPE SLOPE/W Version 5.2 software was used for global stability analysis of the preferred concrete gravity wall alternative. Results and relevant information are presented in Appendix D.

6. Generalized Recommendations:

6.1. Recommended Backfill Material: All engineered fill shall consist of A-2-4 or A-1

AASHTO Classification fill placed and compacted to 95 % of the modified Proctor density. Engineered fill shall be handled and placed per latest applicable PR Highway

Authority Specifications. Engineered fill shall be monitored by soil technician with guidance from a geotechnical engineer.

6.2. Fill Recommendations: Any fill shall be constructed upslope in horizontal layers and benched terraces shall be cut at the interface of fill and natural soils. The benches shall have a minimum width of 0.9 mts (3 ft) and shall be made at a maximum vertical distance of 0.9 mts (3 ft) as fill progresses upward. Unreinforced engineered fill slopes shall not exceed 2:1 (H:V) inclination.

6.3. Drainage: Road drainage shall be controlled by Jersey barriers, curbs and gutters or storm runoff management devices designed in such way that it prevents any overland water discharge over the project areas.

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6.4. Slope Erosion Control: Protect all slopes disturbed by excavations process with sodding or turf reinforcement. Deep rooted vegetation such as vetiver and fern

(“helecho”) is recommended within any area impacted by the project and particularly the slope extending downslope from the toe of the retaining wall.

6.5. Differing Site Conditions: These recommendations are based on test borings performed on locations, which are considered as representative of the subsoil conditions within the site, but not all areas of the site could be explored due to limitations of access.

Therefore, differing site conditions could occur. In such instances, we shall be notified to proceed with a field visual inspection directed to formulate the corresponding solution.

6.6. Excavation Safety: Contractor is responsible to adjust excavation inclination and provide shoring, where necessary, to ensure safety of working personnel per latest applicable OSHA excavation safety standards. The contractor shall consult with geotechnical engineer or geologist on excavation inclination and shoring requirements.

6.7. Geotechnical Engineer Confirmation: The excavations shall be coordinated with the undersigned to conduct a site visit by a representative from Jaca & Sierra Engineering, PSC to verify conditions and confirm foundation depth among other geotechnical considerations.

Thanks for the opportunity of providing our field investigation, testing and engineering consulting services. Feel free to contact us for any questions on our report.

Respectfully submitted, JACA & SIERRA ENGINEERING, PSC

Rommel Cintrón Aponte, MSCE, PE

Geotechnical Engineer

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1 2 / 1 7 / 2 1

Appendix A: Geology Map and Boring Location Plan

Figure A1: Site Geology Map – Nelson, A.E., and Tobisch, O.T., 1968, Geologic map of the Bayaney quadrangle, Puerto Rico: U.S. Geological Survey, Miscellaneous Geologic Investigations Map I-525

SITE

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Figure A2: Boring Location Plan – Site plan provided by Javier E. Bidot & Associates, PSC

A B

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Appendix B: Site Conditions Photographic Images

Figure B1: Existing road conditions and damaged area

Figure B2: Damaged road area

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Figure B3: Existing road conditions and damaged area

Figure B4: Downslope at damaged road area

Appendix C:

Boring Logs and Laboratory Tests

483.00

482.39

481.78

FILL: sandy gravel with asphalt debris, gray, black

FILL: sandy clay some gravel, red, gray

CLAYEY SILT some sand, stiff, red, reddish yellow

Do... very stiff, brownish yellow, gray, relic joints

Do... trace weathered rock fragments, hard

S-1

S-2

S-3

S-4

S-5

S-6

S-7

SUBSURFACE EXPLORATION LOG

BORING N0.: A

PROJECT

Landslide and Road Evaluation and Repairs (ER-HWY-140)

JOB

OF

SHEET 1

LOCATION PR-128 Km. 54.77, Lares, PR DRILLER/DRILL RIG: Carlos I. Diaz / CME-45

COORDINATES 247920 N 154743 E DATE HOLE STARTED 1-17-19 COMPLETED 1-17-19

DESCRIPTION BY Rommel Cintron ELEVATION TOP OF HOLE (mts): 483 GROUNDWATER (FT) Initial: Not Found Final: ENGINEER Rommel Cintron DRILLING METHOD: Hollow-Stem Auger 2.25" ID TOTAL DEPTH OF HOLE (ft): 20.5

N W Qu PL+LL

"N" - Number of blows required to drive the sampling spoon a distance of 12 in. with a 140 lbs hammer falling 30 in.

"W" - Natural Moisture Content in percentage of dry weight. Initial G.W. Depth "Qu" - Unconfined Compressive Strength in tons per square foot. Final G.W. Depth "Rc" - Core recovery in percent for each successive run. "Rqd" - Rock quality designation.

"WH" - Sample was recovered by advancing the sampler with the weight of the hammer.

"P" - A "P" in the Unconfined Compressive Strength test indicates the use of the pocket Penetrometer.

Elev.

(mts)

0.00

DEPTH

(feet) DESCRIPTION

LE

G

E N

D

S am pl e

N o.

TY

P

E

B

LO

W S

SPT

N W Qu RC RQD%

20 40 60 80

1 2 3 4

Qu

N-W

482.00

481.39

479.26

FILL: sandy gravel with asphalt debris, gray, black

FILL: sandy clay some gravel, brownish yellow, red, gray

CLAYEY SILT some sand, stiff, red, brownish yellow

Do... trace weathered rock fragments, hard, relic joints

S-1

S-2

S-3

S-4

S-5

S-6

S-7

SUBSURFACE EXPLORATION LOG

BORING N0.: B

PROJECT

Landslide and Road Evaluation and Repairs (ER-HWY-140)

JOB

OF

SHEET 1

LOCATION PR-128 Km. 54.77, Lares, PR DRILLER/DRILL RIG: Carlos I. Diaz / CME-45

COORDINATES 247917 N 154746 E DATE HOLE STARTED 1-17-19 COMPLETED 1-17-19

DESCRIPTION BY Rommel Cintron ELEVATION TOP OF HOLE (mts): 482 GROUNDWATER (FT) Initial: Not Found Final: ENGINEER Rommel Cintron DRILLING METHOD: Hollow-Stem Auger 2.25" ID TOTAL DEPTH OF HOLE (ft): 20.5

N W Qu PL+LL

"N" - Number of blows required to drive the sampling spoon a distance of 12 in. with a 140 lbs hammer falling 30 in.

"W" - Natural Moisture Content in percentage of dry weight. Initial G.W. Depth "Qu" - Unconfined Compressive Strength in tons per square foot. Final G.W. Depth "Rc" - Core recovery in percent for each successive run. "Rqd" - Rock quality designation.

"WH" - Sample was recovered by advancing the sampler with the weight of the hammer.

"P" - A "P" in the Unconfined Compressive Strength test indicates the use of the pocket Penetrometer.

Elev.

(mts)

0.00

DEPTH

(feet) DESCRIPTION

LE

G

E N

D

S am pl e

N o.

TY

P

E

B

LO

W S

SPT

N W Qu RC RQD%

20 40 60 80

1 2 3 4

Qu

N-W

(X=NO)PERCENTFINERSIZE

PASS?SPEC.*PERCENTSIEVE

Project No:

Project:

Client:

Elev./Depth:Location:

Date:Source of Sample:Sample No.:

Remarks

Classification

Coefficients

Atterberg Limits

Material Description

AASHTO=USCS=

Cc=Cu=

D10=D15=D30=

D50=D60=D85=

PI=LL=PL=

Particle Size Distribution Report

P E R C E N T F

IN

E R

100 10 1 0.1 0.01 0.001500

GRAIN SIZE - mm

% +75 MM % GRAVEL % SAND % SILT % CLAY

i n i n i n

-1 /2 i n i n

/4 i n

/2 i n

/8 i n

0.0 3.1 54.7 42.2

Figure7962

Landslide and Road Evaluation and Repairs (ER-HWY-140)

Jose A. Batlle y Associados

4-7.5'Lares, PR

2/13/19Project SiteER-140A

Tested by: J. Cordova

Checked by: Rommel Cintron Aponte, MSCE, PE

A-7-5(2)SM

0.1370.2531.25

114130

Silty sand

(no specification provided)

JACA & SIERRA

TESTING LABORATORIES

San Juan, Puerto Rico

100.0 99.6 96.9 90.2 69.1 51.3 42.2

.5 in.

.375 in.

#4 #10 #40 #100 #200

(X=NO)PERCENTFINERSIZE

PASS?SPEC.*PERCENTSIEVE

Project No:

Project:

Client:

Elev./Depth:Location:

Date:Source of Sample:Sample No.:

Remarks

Classification

Coefficients

Atterberg Limits

Material Description

AASHTO=USCS=

Cc=Cu=

D10=D15=D30=

D50=D60=D85=

PI=LL=PL=

Particle Size Distribution Report

P E R C E N T F

IN

E R

100 10 1 0.1 0.01 0.001500

GRAIN SIZE - mm

% +75 MM % GRAVEL % SAND % SILT % CLAY

i n i n i n

-1 /2 i n i n

/4 i n

/2 i n

/8 i n

0.0 7.7 27.3 65.0

Figure7962

Landslide and Road Evaluation and Repairs (ER-HWY-140)

Jose A. Batlle y Associados

2-5.5'Lares, PR

2/14/19Project SiteER-140B

Tested by: J. Cordova

Checked by: Rommel Cintron Aponte, MSCE, PE

A-7-5(14)MH

0.744

225331

Sandy elastic silt

(no specification provided)

JACA & SIERRA

TESTING LABORATORIES

San Juan, Puerto Rico

100.0 96.2 93.3 93.0 92.3 89.2 81.3 71.1 65.0

1 in.

.75 in.

.5 in.

.375 in.

#4

#10 #40

#100 #200

Appendix D:

SLOPE/W Software Results

Figure D1: Drained static condition

Figure D2: Drained seismic condition

Figure D3: Undrained static condition

Figure D4: Undrained seismic condition