Report_GEO_AC-820579_HWY-156.pdf

P.O. Box 260370, San Juan, PR 00926-2622 ● 787.281.0686 ● www.despiau.net

April 12, 2019

Enrique Ruiz & Associates PO Box 360977 San Juan, Puerto Rico 00936-0977 Ph: 787.783.6717; Fax: 787.782.6760 E-mail: e.ruiz@era-pr.com

Attn.: Mr. Enrique Ruiz, PE, President

Subject: Addendum No.1 Proposed Geotechnical Engineering and Subsurface Exploratory Services for the Landslide and Road Damage Evaluation and Reconstruction Project ER-HWY-156 at State Road PR-14, KM 53.4 - 54.4 on Caonillas Ward of the Municipality of Aibonito, Puerto Rico. Reference No. DA/18O3742

Gentlemen:

Following the necessary approval of our revised proposal by the PRTHA’s Soils Engineering office, Despiau

Associates was engaged for the Geotechnical Engineering & Subsurface Exploratory Services on the referenced project. The scope of work and associated terms and conditions of our engagement were detailed in said revised proposal.

However, in order to verify the adequacy of the presented reconstruction alternatives, internal and external stability analyses for slopes within the project’s limits were performed. The degree of stability of a slope is expressed as the factor of safety, which is the ratio of the forces resisting failure to the driving forces causing instability.

The undersigned hereby certifies that the analyses contained in our geotechnical report were performed following the Puerto Rico Transportation and Highway Authority (PRTHA) Design guidelines, including internal and external stability. Moreover, the undersigned confirms that, provided the recommendations contained in the geotechnical report of reference are strictly followed and considered in the design, adequate safety factors for global stability against Static and Pseudo-Static conditions will be obtained. Furthermore, additional slope stability analyses may be performed to assure the global stability of the finally selected alternative.

Should you have any question regarding these matters, please do not hesitate to contact the undersigned.

Respectfully submitted, DESPIAU ASSOCIATES

Jose R. Despiau, P.E.

Geotechnical Engineer http://www.despiau.net/ mailto:e.ruiz@era-pr.com

P.O. Box 260370, San Juan, PR 00926-2622 ● 787.281.0686 ● www.despiau.net

April 29, 2022

PO Box 360977 San Juan, Puerto Rico 00936-0977 Ph: 787.783.6717; Fax: 787.782.6760 E-mail: e.ruiz@era-pr.com

Attn.: Mr. Enrique Ruiz, PE, President

Subject: Addendum No.2 Proposed Geotechnical Engineering and Subsurface

Exploratory Services for the Landslide and Road Damage Evaluation and Reconstruction Project ER-HWY-156 at State Road PR-14, KM 53.4 - 54.4 on Caonillas Ward of the Municipality of Aibonito, Puerto Rico. Reference No.

DA/18O3742

Gentlemen:

Please attached the revised boring logs with the revised soil description based on the classification column. The herein submitted revised Boring Logs shall supersede the previously submitted with the geotechnical report. Therefore, this Addendum No. 2 is an integral part of the already submitted geotechnical report.

Should you have any question regarding these matters, please do not hesitate to contact the undersigned.

Respectfully submitted, Jose R. Despiau, P.E.

Enclosure http://www.despiau.net/ mailto:e.ruiz@era-pr.com

PROJECT: REFERENCE NO.:

BORING NO.:

LOCATION:

NORTHING:

EASTING:

DATE:

GROUND ELEV.:

DEPTH OF HOLE (ft.):

DRILL MACHINE:

DRILLER:

DRILL METHOD:

SHEET: 1 of 1

CASING:

Hammer Weight ( lb.): Drop ( in.):

Type : Size :

SAMPLER:

Hammer Weight (lb.): Drop (in.):

Type: Size:

Soil / Geotechnical Engineering Laboratories D ep th ft

S a m p le r

S a m p le N o

B lo w s

/6 i n

S P

T N

-V a lu e

S y m b o l

Material Description

R e co v er y

R .Q

.D

W a te r

C o n te n t q u

W a te r

L e ve l

L iq u id

L im it

P la st ic it y

I n d ex

S o il

C la ss if ic a ti o n

$ DEPTH OF WATER BEFORE COMPLETION

# DEPTH OF WATER AFTER 24 HOURS

qu (TSF) - UNCONFINED COMPRESSION STRENGTH wh = WEIGHT OF HAMMER TO DRIVE SAMPLE Wn = NATURAL WATER CONTENT IN PERCENT OF DRY WEIGHT

ER-HWY-156 DA/18O3773

156-1

Aibonito

235673.69 219570.52

01/22/19

497.31

CME-45

Jose R. Bruno

5-5/8" Auger

N/A

N/A N/A

N/A N/A

SS

140 30

Split Spoon Sampler 1-3/8" I.D.

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

50-60/3"

42-60/6"

47-70/2"

65/6"

80/6"

75/6"

80/4"

100/3"

100/2"

100/3"

100/2"

100/4"

100/2"

Ground Surface

Clayey Sand With Gravel Dark grayish brown and brown clayey sand with gravel, some asphalt, some gravel fragments.

Clayey Sand (R)

Pale olive clayey sand some weathered rock fragments.

Sandy Silt (WC)

Weathered rock into grayish brown weathered rock with sandy silt, some rock fragments.

Silty Sand With Gravel (WH) Completely weathered rock into brown silty sand with gravel and rock fragments.

Note: Weathered rock was broken by sampling device into the described constituents.

G ro un d w at er w as n ot fo un d w ith in th e ex te nt d ril le d.

NP

28.7

21.0

8.4

3.8

A-1-b (0)/SC

A-2-4 (0)/SC

A-1-a (0)/SM

LOCATION:

NORTHING:

EASTING:

DATE:

GROUND ELEV.:

DEPTH OF HOLE (ft.):

DRILL MACHINE:

DRILLER:

DRILL METHOD:

SHEET: 1 of 1

CASING:

Hammer Weight ( lb.): Drop ( in.):

Type : Size :

SAMPLER:

Hammer Weight (lb.): Drop (in.):

Type: Size:

Soil / Geotechnical Engineering Laboratories D ep th ft

S a m p le r

S a m p le N o

B lo w s

/6 i n

S P

T N

-V a lu e

S y m b o l

Material Description

R e co v

.D

W a te r

C o n te n t

W a te r

L e ve l

L iq u id

L im it

P la st ic it y

I n ss if ic a ti o n

$ DEPTH OF WATER BEFORE COMPLETION

# DEPTH OF WATER AFTER 24 HOURS

qu (TSF) - UNCONFINED COMPRESSION STRENGTH wh = WEIGHT OF HAMMER TO DRIVE SAMPLE Wn = NATURAL WATER CONTENT IN PERCENT OF DRY WEIGHT

ER-HWY-156 DA/18O3773

156-2

Aibonito

235673.48 219552.51

01/28/19 - 01/29/19

498.46

CME-45

Jose R. Bruno

5-5/8" Auger

N/A

N/A N/A

N/A N/A

SS

140 30

Split Spoon Sampler 1-3/8" I.D.

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

SS

80-80-60

60/6"

5-13-27

90/3"

100/6"

25-27-25

40-60/3"

94/6"

38-100/3"

75/5"

70/4"

100/3"

100/2"

Ground Surface

Clayey Sand With Gravel Dark grayish brown clayey sand with gravel, some subangular gravel fragments, some asphalt.

Clayey Sand Brown and reddish yellow clayey sand, some weathered rock fragments.

Silty Sand (R) Brown, yellow, light gray silty sand, trace clay, weathered rock fragments.

Sandy Silt (WC)

Weathered rock into light brownish gray sandy silt, trace clay, some rock fragments.

Silty Sand (WH)

Weathered rock into light olive brown silty sand trace rock fragments.

Note: Weathered rock was broken by sampling device into the described constituents.

un d w at er w as n ot fo un d w ith in th e ex te nt d ril le

30.3

35.9

32.2

9.9

7.8

3.0

A-1-b (0)/SC

A-4 (0)/SM

A-4 (0)/SM

LOCATION:

NORTHING:

EASTING:

DATE:

GROUND ELEV.:

DEPTH OF HOLE (ft.):

DRILL MACHINE:

DRILLER:

DRILL METHOD:

SHEET: 1 of 1

CASING:

Hammer Weight ( lb.): Drop ( in.):

Type : Size :

SAMPLER:

Hammer Weight (lb.): Drop (in.):

Type: Size:

Soil / Geotechnical Engineering Laboratories D ep th ft

S a m p le r

S a m p le N o

B lo w s

/6 i n

S P

T N

-V a lu e

S y m b o l

Material Description

R e co v

.D

W a te r

C o n te n t

W a te r

L e ve l

L iq u id

L im it

P la st ic it y

I n ss if ic a ti o n

$ DEPTH OF WATER BEFORE COMPLETION

# DEPTH OF WATER AFTER 24 HOURS

qu (TSF) - UNCONFINED COMPRESSION STRENGTH wh = WEIGHT OF HAMMER TO DRIVE SAMPLE Wn = NATURAL WATER CONTENT IN PERCENT OF DRY WEIGHT

ER-HWY-156 DA/18O3773

156-3

Aibonito

235671.51 219481.27

01/29/19 - 01/30/19

503.45

CME-45

Jose R. Bruno

5-5/8" Auger

N/A

N/A N/A

N/A N/A

SS

140 30

Split Spoon Sampler 1-3/8" I.D.

SS

SS

SS

SS

SS

SS

C

75-40-60

60/6"

11-44-40

34-29-20

34-40-51

16-12-14

Ground Surface

Poorty Graded Sand With Clay And Gravel Dark grayish brown, brown and reddish yellow poorty graded sand with clay and gravel

Clayey Sand

Weathered rock into reddish yellow, yellow and light gray clayey sand some rock fragments, some clay.

Volcanic Rock Dark gray, light greenish gray, white mottled fine grained slightly fragmented, volcanic rock.

Note: Weathered rock was broken by sampling device into the described constituents.

un d w at er w as n ot fo un d w ith in th e ex te nt d ril le

39.2

14.4

A-1-b (0)/SP-SC

A-6 (2)/SC

LOCATION:

NORTHING:

EASTING:

DATE:

GROUND ELEV.:

DEPTH OF HOLE (ft.):

DRILL MACHINE:

DRILLER:

DRILL METHOD:

SHEET: 1 of 1

CASING:

Hammer Weight ( lb.): Drop ( in.):

Type : Size :

SAMPLER:

Hammer Weight (lb.): Drop (in.):

Type: Size:

Soil / Geotechnical Engineering Laboratories D ep th ft

S a m p le r

S a m p le N o

B lo w s

/6 i n

S P

T N

-V a lu e

S y m b o l

Material Description

R e co v

.D

W a te r

C o n te n t

W a te r

L e ve l

L iq u id

L im it

P la st ic it y

I n ss if ic a ti o n

$ DEPTH OF WATER BEFORE COMPLETION

# DEPTH OF WATER AFTER 24 HOURS

qu (TSF) - UNCONFINED COMPRESSION STRENGTH wh = WEIGHT OF HAMMER TO DRIVE SAMPLE Wn = NATURAL WATER CONTENT IN PERCENT OF DRY WEIGHT

ER-HWY-156 DA/18O3773

156-4

Aibonito

235656.70 219456.06

01/04/19

505.20

CME-45

Jose R. Bruno

5-5/8" Auger

N/A

N/A N/A

N/A N/A

SS

140 30

Split Spoon Sampler 1-3/8" I.D.

SS

SS

SS

SS

SS

SS

SS

SS

C

20-41-50

60/4"

60/3"

100/4"

100/3"

100/2"

70/5"

100/3"

Ground Surface

6"-Inches Asphlat

Clayey Sand Brown and dark brown clayey sand, trace weathered rock fragments.

Sandy Silt (R) Weathered rock into light brownish gray sandy silt, trace rock fragments.

Silty, Clayey Sand With Gravel (WC)

Completely weathered rock into brown silty, clayey sand with gravel and rock fragments.

Volcanic Rock Dark gray, light greenish gray, white mottled, fine grained, slightly fragmented, volcanic siltstone.

Note: Weathered rock was broken by sampling device into the described constituents.

60.0

56.7 un d w at er w as n ot fo un d w ith in th e ex te nt d ril le

24.1

22.6

7.8

4.4

A-1-b (0)/SC-SM

CONSULTING GEOTECHNICAL ENGINEERS

PO BOX 260370

San Juan, PR 00926-2622 www.despiau.net

Report of Geotechnical Engineering and Subsurface Exploratory Services for the Landslide and Road Damage Evaluation and Reconstruction Project at State Road PR-14, KM 53.4-54.4on Caonillas Ward of the Municipality of Aibonito, Puerto Rico.

Reference No. DA/18O3742

PROJECT ID: ER-HWY-156

February 1, 2019

Prepared for:

Enrique Ruiz & Associates, PSC

PO Box 360977 San Juan, Puerto Rico 00936-0977

Jose R. Despiau, P.E., License #17343 Geotechnical Engineer, Despiau Associates – Consulting Geotechnical Engineers.

P.O. Box 260370 San Juan, PR 00926-2622 ● 787.281.0686 ● www.despiau.net

February 1, 2019

PO Box 360977 San Juan, Puerto Rico 00936-0977 Ph: 787.783.6717; Fax: 787.782.6760 E-mail: e.ruiz@era-pr.com

Attn.: Mr. Enrique Ruiz, PE, President

Subject: Proposed Geotechnical Engineering and Subsurface Exploratory Services for the Landslide and Road Damage Evaluation and Reconstruction Project at State Road PR-14, KM 53.4 - 54.4 on Caonillas Ward of the Municipality of Aibonito, Puerto Rico. Reference No. DA/18O3742

Dear Eng. Ruiz:

As requested, we have completed the Subsoil Exploration and Geotechnical Engineering Assessment for the review of the landslide(s) and/or road, which were affected post Hurricane María as part of the Landslide and Road Damage Evaluation and Reconstruction Project ER- HWY-156, at State Road PR-14, KM 53.4 - 54.4 on Caonillas Ward of the Municipality of Aibonito, Puerto Rico.

The work was undertaken at the request of Mr. Enrique Ruiz, PE, President of Enrique Ruiz & Associates, PSC. The work was made in accordance to Proposal No. DA/04-51-18R for the subsurface exploration dated May 5, 2018. The work was commenced after order to proceed for the work was received on November 11, 2018.

This report presents the results of the field exploratory drilling, laboratory tests performed on secured soil samples, engineering assessments from geotechnical standpoint, soil and foundation design parameters for the proposed improvements (i.e. retaining walls, cut and fill earthwork specifications) as required thereof.

It has been a pleasure to have been of your assistance in this project.

Respectfully Submitted, Jose R. Despiau, PE.

Project No.: DA/18O3773 Aibonito, Puerto Rico February 1, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS i

TABLE OF CONTENTS

Page No.

I. INTRODUCTION

II. SITE AND PROJECT DESCRIPTION

III. FIELD SUBSURFACE AND SAMPLING PROGRAM

3.1 Subsurface Investigations

3.2 Geological Notes

3.3 Stratigraphic Units

IV. OBSERVATIONS AND FINDINGS

V. ENGINEERING RECOMMENDATIONS

5.1 General Design Parameters for Retaining Structures

5.1.1 Additional Considerations for Retaining Structures

5.1.2 Rock Anchors Design Considerations

5.2 Additional Recommendations for Cantilever Retaining Structures

5.3 Additional Recommendations for a Drilled Shaft Retaining System

5.3.1 Lateral Load Design Considerations

5.4. Additional Recommendations for a Drilled Shaft with Cantilever Beam Segment

5.4.1 Drilled Shaft Types and Capacities

5.4.2 Additional Drilled Shaft Recommendations

5.4.3 Lateral Load Design Considerations

5.4 Earthquake Design

5.5 Excavations

5.6 General Earthwork Recommendations

5.6.1 Excavations

5.6.3 Temporary Cut Sections

5.6.4 Backfill Material

5.7 Proposed Storm Water Run-off Control

5.8 Nearby Structures

5.9 Additional Recommendations

VI. LIMITATIONS OF THIS REPORT

Appendix (A) – Figures

1. US Geological Survey Service Topographical plan at a scale 1:20,000 1A. Geological Map

2. Boring Location Plan

Appendix (1) - Boring Logs Appendix (2) - Earthwork Specifications Appendix (3) - Special Laboratory Tests

I. INTRODUCTION

This report covers the Subsoil Exploration and Geotechnical Engineering Assessment for the review of the landslide(s) and/or road, which were affected post Hurricane María as part of the

Landslide and Road Damage Evaluation and Reconstruction Project ER-HWY-156, at State Road

PR-14, KM 53.4-54.4 on Caonillas Ward of the Municipality of Aibonito, Puerto Rico.

The work was undertaken at the request of Mr. Enrique Ruiz, PE, President of Enrique Ruiz &

Associates, PSC. The work was made in accordance to Proposal No. DA/04-51-18R for the subsurface exploration dated May 5, 2018. The work was commenced after order to proceed for the work was received on November 11, 2018.

This report presents the results of the field exploratory drilling, laboratory tests performed on secured soil samples, geotechnical assessments, and summary of findings, and recommendations for required site improvements.

Presently, three (3) reconstruction alternatives to cope with the disclosed conditions at the Site can be considered by the A/E Design Team. However, should the A/E design team consider other(s) and/or additional design reconstruction alternatives these shall be forwarded to this office to evaluate them and provided the required geotechnical recommendation, if deemed necessary.

In the following sections of this report the soil and foundation design parameters for the proposed improvements (i.e. retaining structures, cut and fill earthwork specifications) are being provided.

The selected boring locations were used to establish the profile data at the specific explored locations for the present geotechnical engineering review. This report has been prepared for the exclusive use of the owner and the A/E Consultant Firm involved in the preparation of the site engineering design plans and specifications.

II. SITE AND PROJECT DESCRIPTION

The Site observation revealed two (2) major landslides occurred along the eastern edge of State

Road PR-14 near km’s 53.4 and 54.4. The complete extent of road damage, caused by both landslides extend some 130.0 meters, however if each landslide is taken separately the extent of

Project No.: DA/18O3773 Aibonito, Puerto Rico February 1, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 2

each is some 10 and 20 meters in length, western (1) [Borings 156-3 & 156-4] and eastern (2)

[Borings 156-1 & 156-2] sloping grounds, respectively.

Based on the US Topographic map the Rio Usabón River lies about 200 meters north of the Site

(at an approximate elevation of 420 mts.). The roadside elevation is approximate 80 to 100 meters higher than the Rivers stream bed. These difference in elevation creates very steep sloping ratios, varying between 36° to 48° degrees steeper sloping grounds were assess on the eastern slide (2) and between 46° to 48° on the eastern slide (1), approximately. These slope ratios are too steep considering the surface in-situ soils, which minimal surface runoff will trigger additional slides.

Also, field observations revealed the average total width of State Road PR-14 at the project sector is approximately 5.95 to 7.3 mts. (19.5 to 24 ft.) wide. This narrow road section limits the reconstruction alternatives to cope with the limited space available for construction considering

PR-14 is a mayor highway with a heavy ADT (average daily traffic).

The following sections of this geotechnical report will provide the required Site improvements and foundation design recommendation for the proposed improvements required at the Site.

III. FIELD SUBSURFACE AND SAMPLING PROGRAM

3.1 Subsurface Investigations

The subsurface soil conditions at the site were investigated four (4) standard penetration test borings performed to assess the existing subsoil conditions at the project site. The location of borings is shown in the accompanying Boring Location Plans, in Appendix A, Figure No. 2.

Sampling of soils was performed continuously in the upper 10 ft. and thereafter, at approximately five-foot intervals. All soil samples were taken with a 2"-O.D. split barrel sampler following the standard penetration test procedures in ASTM D-1586. Penetration resistance values from the standard penetration tests are recorded in the "N" column of the boring logs.

Project No.: DA/18O3773 Aibonito, Puerto Rico February 1, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 3

The procedures used for the laboratory tests, as well as the routine and special laboratory procedures used, for the determination of the index soil properties are contained in the Appendix

(1) to this report.

3.2 Geological Notes

Based on the US Geological Survey of the Geologic Map and Sections of the Comerio Quadrangle

(Map I-320), prepared by Mr. Maurice H. Pease, Jr. and Reginald P. Brigs (1960), the geologic units that lie at or near the site are the following:

1. Los Robles Formation (Kr) – Described as chiefly thinly stratified fine0grained sedimentary rocks, Kr, but includes volcanic breccia, Krb, Krb2 and lava flows, Krf. Also, includes the Las Tetas lava member (Krt), Lapa lava member, lower flow (Krf) and upper flow (Krl2) and Rio Matón limestone Member (Krr), a thin discontinuous unit at the base of the formation. This formation, whose type area is Robles ward is best exposed along

Highway 14 and the valley of Quebrada Honda. Th rocks are essentially conformable with the rocks of formation K, but they overlap part of formation K toward the southeast. The dipping planes vary between 22° and 25° with a southwest trend. The faulted blocks of this sequence are continuous across a major anticlinal structure and are correlated with northwestward-dipping sedimentary rocks exposed in the northwestern part of the Comerίo

Quadrangle. The formation is composed chiefly of well-bedded sandstone and siltstone intercalated with thickly bedded, medium to coarse grained volcanic sandstone as waterlaid tuff. These rocks are medium dark gray to medium bluish gray when fresh, but weather to pale shades of brown and reddish-brown soil. Calcite and silica are the common cementing agent

The geologic map shows the Rio Usabón fault, with a northwest-southeast trend, is at approximately 800 meters northeast of the project site. Also, another approximate Unnamed fault line crossing, found about 275 meters to the southwest with a near northwest-southeast trend.

Refer to the US Geological Survey – Geologic Map which is included in Appendix A, Figure 1A.

Project No.: DA/18O3773 Aibonito, Puerto Rico February 1, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 4

3.3 Stratigraphic Units

Upper Surface Section – Generally at the road surface, the results of the exploration disclosed a surface layer thickness of about 1.5 to 3.0 ft. Following the six 6”-inch to 5”-inch asphalt overlay

[respectively at Borings 156-1 and 156-2], the surface layer is composed of dark grayish brown, reddish yellow and brown sandy silt, with some subangular gravel fragments. At the location of

Boring 156-2, this layer extends deeper into the profile to about 4.5 ft. The standard resistance to penetration (N-values) of the surface layers varied from 40 to practical refusal to penetration, at a dense to very dense State of Consistency. The natural moisture content values range from

3 to 12 percent. Random samples of this layer disclosed AASHTO class type A-1-b (0) AASHTO type soils (USSCS type SC) and Free Swell Test show a 5 percent.

Residual Material – Beneath the above described layers, the virgin soil material was found, extending from about 10 ft. [Boring 156-1 & 156-2]. They are formed as textured sediments from the residuum of highly weathered basic volcanic rock. The samples from this described as pale olive, brown, reddish yellow, yellow, and light gray sandy silt, with some weathered rock fragments. The standard resistance to penetration (N-values) of the residual layers varied from

26 blows/foot to practical refusal, at a dense to very dense State of Consistency. The natural moisture content values range from 1 to 16 percent.

Random sample of the residual material from both boring of exploration, disclosed AASHTO class type A-2-4 (0), A-4 (0), and A-6 (2) soils.

Completely and highly Weathered Rock – Deeper into the profile the completely weathered rock, broken by the sampling device into grayish brown, light brownish gray completely weathered rock with sandy silt fines, with traces of Volcanic rock fragments, product of the weathering of the parent geologic units was found. The standard penetration test attempts disclosed practical refusal to penetration with values greater 100 blows for a few inches of penetration. The natural moisture contents range from 1 to 16 percent.

Fresh Rock – at the location of Borings 156-3 and 156-4 Los Robles formation was drilled. To advance the boreholes it was necessary the use of diamond bits for the core runs performed.

These were described as dark gray, light greenish gray, white mottled, fine grained slightly

Project No.: DA/18O3773 Aibonito, Puerto Rico February 1, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 5

fragmented volcanic rock. The Fresh rock was encountered at a depth of 10 and 15 ft. at the location of Borings 156-3 and 156-4, respectively.

Graphical representation of the soil profiles is illustrated in the boring logs included as Appendix

(1) to this report.

3.4 Groundwater Levels

In general, the permanent ground water level was not found within the extent of depth drilled, during the period of exploration. All depths were measured from the existing ground surface prevailing during the period of exploration.

All surface ground and underground water should flow through existing drainage gullies, from higher sectors of the south toward the lowland areas to the north, towards the Usabón River later on meeting with Rio La Plata River further to the north.

IV. OBSERVATIONS AND FINDINGS

The present exploratory program was conducted to establish the subsurface profile and to allow the presentation engineering assessment, from a geotechnical standpoint, in addition to providing the construction guidelines for the implementation of the proposed improvements to the western sloping grounds, where several landslides scarps have been experienced on the eastern edge of

State Road PR-14, which was subjected to extensive degradation, erosional effects, and landslides causing the observed damages and partial rupture of the road embankment and pavement structure.

Field observations revealed two (2) major landslides occurred along the eastern edge of State

Road PR-14 near km’s 53.4 and 54.4. The complete extent of road damage, caused by both landslides extend some 130.0 meters, however if each landslide is taken separately the extent of each is some 10 and 20 meters in length, western (1) [Borings 156-3 & 156-4] and eastern (2)

[Borings 156-1 & 156-2] sloping grounds, respectively. Evaluations dictate that besides the surface failures caused by the excessive runoff experience during the hurricane event, an

Project No.: DA/18O3773 Aibonito, Puerto Rico February 1, 2019

DESPIAU ASSOCIATES – CONSULTING GEOTECHNICAL ENGINEERS 6

additional failure plane exist between the interface of the upper fill section and the residual weathered material. This interface generally occurs at about 6.5 ft. in depth, on [Slide (1) -Borings

156-3 and 156-4] and 5.0 ft. [Slide (2) Borings 156-1 & 156-2], respectively. Therefore, any retaining structure to be install shall be founded deeper than the previously mentioned failure plane.

Based on the results of the subsurface exploration performed, evaluations and Site observations, our engineering assessment is that the primary cause for the prevalent conditions were caused by the excessive surface subsurface water runoff, which eroded the lower northern sloping ground subsurface soils. The intense or above normal erosional conditions experienced during Hurricane

Maria was the primary factor which caused the prevailing conditions.

In addition, evaluation of the topographic plan submitted for the present evaluation revealed, the

Rio Usabón River lies about 200 meters north of the Site (at an approximate elevation of 420 mts.). The roadside elevation is approximate 80 to 100 meters higher than the Rivers stream bed. These difference in elevation creates very steep sloping ratios, varying between 36° to 48° degrees steeper sloping grounds were assess on the eastern slide (2) and between 46° to 48° on the eastern slide (1), approximately. These slope ratios are too steep considering the surface in-situ soils, which minimal surface runoff will trigger additional slides if not provided with the herein retaining structures being recommended.

Also, field observations revealed the average total width of State Road PR-14 at the project sector is approximately 5.95 to 7.3 mts. (19.5 to 24 ft.) wide. This narrow road section limits the reconstruction alternatives to cope with the limited space available for construction considering

PR-14 is a mayor highway with a heavy ADT (average daily traffic).

Therefore, to cope with the presently disclosed subsoil conditions and to assure no further instability is experienced, the herein recommendation to be considered shall be applied along the western edge of PR-14 to render stable grounds and road safety. The herein recommendation by themselves and/or any combination of them shall be applied to the presently affected area

(western sloping grounds) to render stable grounds. The following sections of this report will provide the required Site improvements and foundation design recommendation for the proposed improvements required at the Site.

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Considering the subsoil profile and slope ratios prevailing at the site, the improvement project may consider three (3) construction approaches or any combination of them. These are the following:

1. Evaluation of the Site conditions revealed, the existing road width is some 19 to 24 ft. wide and the total study sector is approximately 130 mts. However, the affected areas to be considered to be considered are the two (2) major slides western (1) and eastern (2), 10 and

20 meters in length, respectively. The prevailing sloping grounds west of State Road PR-

14, at the study sectors, have slope ratios ranging between 36° to 48° degrees. These slope ratios are too steep considering the in-situ soil encountered. Therefore, a cantilever retaining structure (with or without a slope section on top, if space is available) to retain the northern soil embankment mass and State Road PR-14 pavement structure shall be considered to attain the required embankment stability of the roadway section. The retaining wall shall be provided all-throughout the affected areas parallel to the northern edge of State Road PR-

14. However, evaluation reveal the major slides presently considered are approximately 10 and 20 mts. in length, respectively. The total height of the wall will depend on the final wall alignment and grading elevations and if they are provided with an adequate slope section

(2H:1V) on top, to reach the roadside elevation, however, preliminarily no space is available, therefore a cantilever wall by itself shall be considered. Thus, a cantilever wall of approximately 7 to 15 ft. (slide 1 & 2, respectively) in height will most probably be required, depending on its final alignment.

2. As a second alternative for the reconstruction of the northern sloping grounds which may be consider is the use of a retaining structure composed 18” to 24” inch diameters Drilled Shafts with a cap beam/wall to restrain the uppers soil layers, some 5.0 ft. (spacing), in between piles. The cap beam/wall shall be use for two (2) purposes, to reduce the pile moment/deflection at the top and to restrain any soil material between piles in the upper surface layer.

Considering the subsurface conditions at the site, where the dense residual and saprolitic material was found as shallow as 1.0 ft., NO driven piles shall be considered. Also, it shall be noted that the final length, diameter and quantity of shaft sections shall depend on the expected lateral loads and final grading elevations of the project. Although very dense profile was encountered, which on other circumstances it would not be considered, considering the

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space constraints of the project it has been considered one of the few alternatives viable to assure the road safety during and after construction.

3. As a third alternative for the reconstruction of the western sloping grounds which may be consider is the use of a drilled shafts to support a prefabricated cantilever beam Segment

(“Dovela” in Spanish) on top to allow the expansion of the northernmost lane. This alternative can also be used all throughout PR-14, on existing narrow segments which do not permit conventional construction procedures and would require extensive MOT’s during construction.

The drilled shafts spacing shall be determined based on the actual loading conditions required to withstand the expected loading conditions (dead and live loads). However, for cost estimate purposes, solely, 36”-inch diameter shafts spaced at 10 ft. on center can be considered until the final design scheme is established. They shall be installed parallel of

PR-14 at the crest of the northern sloping grounds. These shall have a minimum embedment length varying between 15 to 25 ft. (measured from the existing road side elevation). A minimum unsupported length of 5.0 ft. shall be considered by design. It shall be noted that the final length and type of the Drilled Shaft piles will depend on the final wall alignment and grading elevations as well as the expected lateral loads, as the structural evaluation will reveal.

Regardless of the final design alternative selected, new and/or additional drainage facilities of enough capacity shall be provided, based on hydrologic study. All surface water shall drain freely away from the embankment slope mass. Therefore, all surface water shall drain away from the embankment slope mass to adequate outfalls. Also, surface erosion countermeasures shall be provided.

The following section of this report will further discuss this alternative and will provided the foundation design parameters.

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V. ENGINEERING RECOMMENDATIONS

The present geotechnical review revealed the re-construction alternatives can be implemented.

Evaluation of the Site conditions revealed, the existing road width is some 19 to 24 ft. wide and the affected area extends for an approximately 130 meters. However, the affected areas to be considered to be considered are the two (2) major slides western (1) and eastern (2), 10 and 20 meters in length, respectively. Evaluations made revealed the prevailing sloping grounds south of State Road PR-14, at the study sector, have slope ratios ranging between 36° to 48° degrees.

Therefore, these steep sloping grounds shall be improved and/or provided with the retaining structures previously mentioned to render stable grounds and road safety. The following sections of this report shall be used for the design of the herein recommended retaining structures.

5.1 General Design Parameters for Retaining Structures

Evaluation indicate that provided the proposed retention structure unit(s) are adequately embedded, into the dense gravelly sandy silt residual, weathered saprolitic material or fresh rock, an adequate global stability of the proposed retaining system can be obtained.

Considering the soil profiles found at the investigated locations the following parameters of in-situ soils may be used for the design of the proposed retaining systems:

SUMMARY OF IN-SITU SOIL PARAMETERS FOR DESIGN

RECOMMENDED RANGE OF VALUES PER LAYERS – BORINGS 156-1 & 156-2

Soil Description Unit

Weight (pcf.)

Angle of Internal Friction (degrees)

Cohesion (psf.)

Allowable Soil Bearing Pressure

(psf.)

New Fill (A-2-4) 125 27 Neglect 2.0 Ksf.

New Fill (Crushed-Stone) 133 33 Neglect

Upper Sandy Silt (0’-4.0’) 124 28 350

Residual Material (4.0' -10') 130 32 - 4.5 Ksf. @ 5.0 ft.

Weathered rock (>10’) 134 35 -

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RECOMMENDED RANGE OF VALUES PER LAYERS – BORINGS 156-3 & 156-4

Soil Description Unit

Weight (pcf.)

Angle of Internal Friction (degrees)

Cohesion (psf.)

Allowable Soil Bearing Pressure

(psf.)

New Fill (A-2-4) 125 27 Neglect 2.0 Ksf.

New Fill (Crushed-Stone) 133 33 Neglect

Upper Sandy silt (0’-3.0’) 124 28 300

Weathered Material (3.0' -10') 133 32 - 4.5 Ksf. @ 6.5 ft.*

Fresh Rock (>10’) 138 40 -

ADDITIONAL NOTES:

1. Complete removal of unsuitable soil and/or slope washed shall be guaranteed. By no means should the bearing material be soft/loose. However, any unsuitable material can be replaced with a well compacted engineering fill section, for which the allowable bearing capacity shall be not greater than 2.0 Ksf.

2. The minimum depth of foundation shall be measured from the existing grade.

3. Full hydrostatic conditions and surcharge loads imposed by the construction sequence and vehicular loadings, shall be considered by design.

Lateral earth pressure coefficients are given for the active and for the at-rest case, depending on whether the wall can rotate at the top or not. Earth pressures will be influenced by structural design of the walls, conditions of wall restraint, methods of construction and/or compaction and the strength of the materials being restrained. Active earth pressure is commonly used for design of free-standing cantilever retaining walls and assumes wall movement. The "at-rest" condition assumes no wall movement and is commonly used for basement walls, loading dock walls, or other walls restrained at the top.

The coefficient for lateral earth pressure, based on Rankine’s Theory, can be determined using the following formulas, however other methods and/or theories may be used as well, depending on actual retaining wall configuration.

Lateral Pressure Coefficient at rest case:

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Coefficient Active Earth Pressure for sloping backfill:

Coefficient Passive Earth Pressure for sloping backfill:

Coefficient Active Earth Pressure for horizontal backfill for vertical face:

Coefficient Passive Earth Pressure for horizontal backfill for vertical face:

The depth of foundation (Df) shall be compatible with the minimum depth requirements previously described. However, a re-compaction of the in-situ soil to a minimum of 95 % of its maximum dry density shall be allowed prior to the foundation construction.

To reduce hydrostatic loading on retaining walls, a subsurface drain system should be placed behind the wall. The drain system should consist of free-draining granular soils containing less than five percent fines (by weight) passing a No. 200 sieve placed adjacent to the wall. The free-draining granular material should be graded to prevent the intrusion of fines or provided with a suitable filter fabric.

A drainage system consisting of either weep holes or perforated drain lines (placed near the base of the wall) should be used to intercept and discharge water which would tend to saturate the backfill. Where used, drain lines should be embedded in a uniformly graded filter material and provided with adequate cleanouts for periodic maintenance. As an alternative, a prefabricated drainage structure, such as geo-composite (Macaferri MacDrain or equivalent), may be used as a substitute for the granular backfill adjacent to the wall.

In addition, a perimeter drain shall be placed along the wall footings and drained away from the units to proper out falls. Underground water, if any, may flows beneath foundations, which are not

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adequately drained, creating unsuitable erosional effects on foundations. This aspect of the construction and design should not be overlooked.

Preferably, the backfill soil is to be clean, free draining coarse granular material (AASHTO A-1-a

Classification), placed in 2-inch to 3-inch layers, each compacted to at least 95% of the material's

Modified Proctor maximum density. However, under standard design criterion, the backfill for the wall should be granular (AASHTO A-2-4 or better), carefully placed and of good quality, above

1.0 m. from the maximum flood level; otherwise, crushed stone compacted to a minimum of 83 % of its bulk density shall be used for the reinforced back fill material.

5.1.1 Additional Considerations for Retaining Structures

Prior to the construction of any retention structure, the complete removal of any soft/loose, unsuitable saturated soil, slope-wash and/or debris shall be allowed prior to the back filling, which shall be done in stages, considering the back-filling recommendations contained in this report.

Also, it is of upmost importance to take all precautions during the excavation procedures to assure slope stability during construction, especially during the excavation phase. To prevent further instability of existing slope surfaces the herein construction sequence shall be performed in alternate improvement (two-stage) sections of not more than 15.0 ft. wide.

The initial stage is to remove any unstable surface material in benches to create a level area on which to rest the proposed retaining structure alignment. Once the initial demucking operation is performed and the over excavation to prepare the foundation base is completed, then the retaining wall foundation can commence.

Also, considering the subsoil conditions found a sand cushion shall be provided beneath the proposed retaining units to avoid any punching shear to the base of the wall, provoke by any pinnacles of the rock once the excavation (working platform) is made.

Considering the proposed retaining structures foundation unit may lie on sloping grounds surfaces, the depth of foundation on these circumstances shall be compatible with a minimum depth requirement such that a line drawn from the bottom edge of the foundation at an angle ( )

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of 30⁰ and at a horizontal distance (t) of 15 ft. from the sloping surface do not intersect with the face of the slope. Refer to the following Figure A.

FIGURE A: Footing in Sloping Grounds

NOTE: The footing depth on sloping grounds shall satisfy a minimum separation requirement such that a line drawn from the bottom edge of the foundation at an angle ( ) of 30⁰ and at a horizontal distance (t) of 15 ft. do not intersect with the face of the slope.

Should the proposed foundation do not meet the minimum separation requirement, deepening of the foundation shall be required. In lieu, a structural key or soil/rock anchors may be provided to the foundation to avoid the translation of the foundation stresses to the sloping grounds and provide an additional sliding retraining measure. However, the prevailing slopes to remain shall be protected against scour and/or erosional effects during an intensive rainfall.

5.1.2 Rock Anchors Design Considerations

To obtain an adequate factor of safety against sliding and overturning rock anchors may be required. Anchors installed into the completely weathered rock will provide overturning and sliding resistance in addition to the dead weight of the foundations, structure and backfill. Anchors should be grouted and prestressed. Capacity of grouted rock anchors should be estimated using the following formula:

P = Lb x x d x TW

P =Design load

Lb =Anchor bond length

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d = Diameter of drill hole

TW =Allowable bond stress between grout and rock surface

For the above equation, the allowable bond stress (TW) may be calculated using an appropriate factor of safety and the estimated ultimate bond stress of 175 psf.

Estimated bond stress values are consistent with published data and considers the subsoil conditions within the anticipated bond zone. Anchors should be installed with a minimum 10 ft.

long unbonded zone (free length) in order to engage higher quality rock and avoid excessive creep and reduction in tensioning as bonds weaken in upper zones.

The weight of rock engaged to resist overturning should be taken as the volume of a truncated cone extending from the midpoint of the anchor bond zone to the surface of the rock at an angle of 45 degrees from vertical multiplied by the unit weight or effective unit weight of rock, as applicable. A minimum factor of safety of 2.0 with respect to rock mass engaged versus overturning load is recommended. Where the rock mass is highly fractured, as is the case in this project a higher factor of safety may be required, along with a smaller cone of influence angle.

At least 10 percent of the anchors should be performance tested at each before production installation of anchors. Pending satisfactory results of performance tests, all anchors need to be proof-tested and locked off to at least the design load. Performance testing will help evaluate load and unload behavior, and creep potential. Proof testing will effectively load test the remaining anchors and verify the capacity of each anchor prior to casting the foundations. If performance testing field capacities do not meet design capacities, anchor lengths and/or drill hole diameters may need to be increased.

Spacing of rock anchors should be such that imaginary lines extending from the top of the grout bonds of adjacent anchors, at an angle of 20 degrees from the perpendicular intersection of the bedrock, to the ground surface do not intersect. Rock anchors should be designed, installed, and tested in accordance with the manufacturer’s recommendations and guidelines by the Post-

Tensioning Institute (PTI) Recommendations for Prestressed Rock and Soil Anchors, 2004 including requirements for water pressure testing and pre-grouting.

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5.2 Additional Recommendations for Cantilever Retaining Structures

The initial stage is to remove any unsuitable surface material to create a level area on which to rest the base of the new retaining structure. The base of foundation of the proposed retaining structure shall be located at a depth which complies with the following criteria:

1. Once the cuts are made and the desired foundation pad is prepared, the base of the retention structure shall be located at a minimum depth of 5.0 and 6.5 ft., respectively, beneath any loose/soft saturated and slope-wash material, beneath the walls alignment

2. The base backfill material, if any, shall be placed above the level of the pre-worked foundation pad in the firm in-situ dense residual or weathered material. For such purposes an inspection of the exposed material shall be allowed during the construction sequence.

3. Once the working pad is prepared a sand cushion shall be provided beneath the proposed retaining units to avoid any punching shear to the base of the wall, provoke by any pinnacles of the rock once the excavation (working platform) is made.

Also, considering the proposed retaining structure foundation unit may lie on sloping grounds surfaces, the depth of foundation on these circumstances shall be compatible with a minimum depth requirement given in Section 5.1 - General Design Parameters for Retaining Structures.

Should the proposed foundation do not meet the minimum separation requirement, deepening of the foundation shall be required. In lieu, a structural key or soil/rock anchors may be provided to the foundation to avoid the translation of the foundation stresses to the sloping grounds and provide an additional sliding retraining measure.

As previously mentioned, rock anchors may be required depending on the final design scheme to obtain an adequate factor of safety against sliding and overturning. The recommendation for the rock anchor design are being provided in Section - 5.4 Rock Anchors Design Considerations of

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this report. However, in this project these may not be able to be installed on the outer face of the wall, depending on the final design scheme, hence a wall key shall be used instead.

5.3 Additional Recommendations for a Drilled Shaft Retaining System

Another reconstruction alternative for the northern sloping grounds which may be consider is the use of a retaining structure composed 18” to 24” inch diameters Drilled Shafts with a cap beam/wall to restrain the uppers soil layers, some 5.0 ft. (spacing), in between piles. The cap beam/wall shall be use for two (2) purposes, to reduce the pile moment/deflection at the top and to restrain any soil material between piles in the upper surface layer.

Considering the subsurface conditions at the site, where the dense residual and saprolitic material was found as shallow as 1.0 ft., special drilling equipment to obtain the minimum embedment length shall be required and NO driven piles shall be considered.

Also, it shall be noted that the final length, diameter and quantity of shaft sections shall depend on the expected lateral loads and final grading elevations of the project. Although very dense profile was encountered, which on other circumstances it would not be considered, considering the space constraints of the project it has been considered one of the few alternatives viable to assure the road safety during and after construction.

The wall shall be located at a distance from the northern edge of PR-14 such that it encases the proposed southern fill embankment south of PR-14, perpendicular to the slope failure. Evaluation dictate this retaining structure shall be the same as alternative No. 1, however, the final location, configuration, length and height shall be determined once the final design scheme is selected by the A/E Design Team

For piles to be effective shall have be spaced at approximately 5.0 ft. on center approximately to a minimum embedment length varying between 10 to 15 ft. (measured from the existing road side elevation) into the residual and completely weathered rock found in the borings of exploration. A minimum unsupported length of 5.0 ft. shall be considered by design.

The pile units shall develop the necessary lateral resistance to sustain the earth and structure loads, assuming full mobility of the soil shear strength. Therefore, the final length and type of the

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Drilled Shafts shall depend on the expected lateral loads and final grading elevations of the project.

Also, the recommended cap beam/wall to be installed on top of the Drilled Shafts shall withstand the expected lateral earth pressures, assuming full hydrostatic conditions and surcharge forces imposed by the construction sequence and vehicular loadings.

Once the combined retaining system is installed, then the re-construction of the pavement structure components can commence.

It shall be noted that the final length, diameter and quantity of the Drilled Shaft piles will depend on the final wall alignment and grading elevations as well as the expected lateral loads and final grading elevations of the project.

5.3.1 Lateral Load Design Considerations

The following design model shall be used in the foundation design for lateral load evaluations of the proposed piles. For lateral calculations, an unsupported length of the upper 5 ft. shall be considered in the evaluation. Should the structural evaluation reveal the expected deflection at the top of the pile is too excessive, the larger pile sections, and/or smaller spacing in between piles and/or providing Deadman, beneath the PR-14 Pavement Structure, may be considered to cope with the expected lateral loads.

Lateral load evaluations depend on the specific requirements of the structure. Often, a 1/4-inch allowable lateral deflection is used as a limit. In no case, the lateral load shall exceed 0.33 the ultimate load capacity. The normally consolidated to slightly over consolidated cohesive as well as for granular soils, the pile deformation can be estimated assuming that the coefficient of sub grade reaction Kh, increases linearly with depth in accordance with the expression:

Kh = f * z / D

Where, Kh = coefficient of lateral subgrade reaction (tons/ft.3) f = coefficient of variation of lateral subgrade reaction (tons/ft.3) z = depth (ft.)

D = width/diameter of loaded area

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