Report - Geo-Report_Addendum_2_Sch A_Hwy-385.pdf

Geotechnical engineers providing geotechnical engineering solutions .... Patricia A. Crumley, MECEE Tirso A. Alvarez, PhD Alan R. Crumley, MSCE

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ADDENDUM NUMBER TWO

TO

GEOTECHNICAL ENGINEERING REPORT

EROSION REMEDIATION

PR-5568 KILOMETER 0.8

Corozal, Puerto Rico

Report dated January 12, 2019 Addendum One was dated March 6, 2019.

Addendum Two is dated May 29, 2020.

In response to comments regarding the previous reports by an unnamed reviewer from an agency named Eastern Federal Lands, we submit this second addendum. Responses are given in the same order as received.

Comment No.

1 Eastern Federal Lands Comment No soil properties were recommended in the geotechnical report or addendum. Please add recommendations for soil parameters (unit weight, friction angle, among others) to the report.

GeoConsult Response

The soil properties that the designer had assumed for initial design and with which I concurred are listed on sheet BC-B/2 of the design. These are repeated below:

BACKFILL MATERIAL, APPROACH

Friction angle = 34 degrees

Cohesion zero

Unit weight 125 lb/ft3

For friction beneath walls, a friction factor of 0.4 is recommended.

IN-SITU WEATHERED ROCK

Friction angle = 32 degrees

Cohesion zero

Unit weight 130 lb/ft3

FOUNDATION FILL

Friction angle = 32 degrees

PR-5568, kilometer 0.8

Addendum No. 2 to Geotechnical Engineering Report

Cohesion zero

Unit weight 125 lb/ft3

2 Eastern Federal Lands Comment

Addendum One recommended an ultimate bearing pressure of 15 kips per square foot, but no factor of safety is recommended. If Ultimate Bearing Capacity is provided in the report, a minimum factor of safety for bearing needs to be provided to be able to perform bearing capacity analysis. Please provide a minimum Factor of Safety.

GeoConsult Response

The addendum states (page 2 of 3) “The recommended ultimate bearing pressure for design of the culvert and flarewalls is 15 kips per square foot, or five kips per square foot in service loads.” The recommended factor of safety is thus three. But, no further bearing capacity analysis is necessary since the allowable (service load) bearing capacity is specified. Also, settlements are discussed later in the report.

3 Eastern Federal Lands Comment

Elevation of box culvert is not recommended in the geotechnical report and Addendum One in regards to bearing capacity recommendations. Please provide a recommendation for the box culvert elevation.

GeoConsult Response

The addendum refers to seven pages that are included in the report, which show the elevations. But, to confirm, the foundation bottom elevations indicated by the designer are listed below. I concur with these elevations for design.

Culvert: 206.00m SW & NW flarewalls: 203.70m NE & SE flarewalls: 203.80m

4 Eastern Federal Lands Comment

Side slopes of 1.5h:1v and 2h:1 are recommended in the addendum but no global stability analysis is provided for the rip rap. Please provide the global stability analysis for rip rap with slope of 1.5h:1v.

GeoConsult Response

Rip-rap depends on many factors determined by the civil and hydraulic designer, such as flow velocity, particle size and gradation, time of drawdown and placement conditions, among others. For a general response, assume rip-rap consisting of boulders and cobbles, minimum thickness 1.5 meters. Assume flood duration is less than 12 hours. Assume native soil permeability is 10-3 ft/minute; thus, native soil is not saturated by flood. Stability in question is for rip-rap. Based on assumed grain size distribution for rip-rap, drainage of rip-rap as flood recedes is immediate. Assumed rip-rap friction angle is 42 degrees (angular, well-graded material). Slope angle of rip-rap is 34 degrees (1:1.5). Then, for an infinite drained slope (clearly conservative, since the slope is not infinite), FS = tan phi / tan theta, where phi is the rip-rap friction angle (42 degrees) and theta is the slope angle (tan-1 1.5/1 = 34 degrees). The factor of safety is tan phi/tan theta = 1.3.

PR-5568, kilometer 0.8

Addendum No. 2 to Geotechnical Engineering Report

Then slope stability analyses were performed, with and without water. The factor of safety on both instances in greater than 1.4. See Figures AA and BB.

I reviewed the geotechnical design manuals for DOTs from the states of Washington, New York, Illinois, South Carolina, Texas and Florida. None of these DOT manuals mentions rip-rap as part of the DOT geotechnical design. Neither does the US Army Corps of Engineers Design Manual for Earth and Rockfill Dams. Not one mentions the need for stability analyses of rip-rap. Feel free to contact me if further information is required.

5 Eastern Federal Lands Comment Addendum appendix shows general plan and elevation sheet with soil parameters. No soil parameters were recommended in the addendum or geotechnical report. Page 5 of addendum one. Please review and clarify if the soil properties recommended are correct.

GeoConsult Response See response to Comment 1. The soil properties mentioned on the plans are correct and I concur.

6 Eastern Federal Lands Comment

Geotechnical report does not show a lab result summary table. Please add.

GeoConsult Response

The actual lab results are referred and identified in the appendix to the report.

Moreover, the Atterberg Limit results (three) are indicated on the borings themselves, and repeated in the three lab result pages. The three results are repeated in the following list:

Boring CR-1, depth 4-6 feet: LL 33, PI 13, USCS SC, 29% gravel, 55% sand, 16% passing #200 sieve

Boring CR-1, depth 10-12 feet: LL 32, PI 14, USCS GP-GC, 54% gravel, 36% sand, 10% passing #200 sieve

Boring CR-2, depth 2-4 feet: LL 39, PI 17, USCS SC, 18% gravel, 47% sand, 35% passing #200 sieve

Boring CR-2, depth 4-6 feet: LL 40, PI 14, USCS SM, 13% gravel, 53% sand, 34% passing #200 sieve

Boring CR-5, depth 6-8 feet: LL 39, PI 16, USCS SC, 31% gravel, 47% sand, 22% passing #200 sieve

Alan R. Crumley, PE May 29, 2020 License 5828 San Juan, Puerto Rico File No. 3008-18

1.472

Rip-rap Mohr-Coulomb 20 kN/m³ 0 kPa 38 °

PR-5568

Corozal, PR Rip-rap Analysis

Native soil Undrained (Phi=0) 17 kN/m³ 100 kPa

Medium stiff soils Undrained (Phi=0) 19 kN/m³ 50 kPa

Distance

0 5 10 15 20 25

E le va tio n

Geoconsult Text Box Figure AA - Riprap stability analysis, no water

1.445

Rip-rap Mohr-Coulomb 20 kN/m³ 0 kPa 38 °

PR-5568

Corozal, PR Rip-rap Analysis

Native soil Undrained (Phi=0) 17 kN/m³ 100 kPa

Medium stiff soils Undrained (Phi=0) 19 kN/m³ 50 kPa

Distance

0 5 10 15 20 25

E le va tio n

Geoconsult Text Box Figure BB - Riprap stability analysis with water

GEOCONSULT

Geotechnical Engineers

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