GEOTECHNICAL ENGINEERING REPORT...Oct 01, 2018 · This report presents the results of our geotechnical investigation and pavement design for the 58.6 Road (Kimball Creek Road) improvements

GEOTECHNICAL ENGINEERING REPORT

58.6 ROAD (KIMBALL CREEK)

58.9 ROAD TO 58.7 ROAD MESA COUNTY, COLORADO

February 9, 2018

Prepared By:

Prepared For:

Mr. Eric Krch, P.E. SGM, Inc. 744 Horizon Court, Suite 250 Grand Junction, CO 81506

Project No. 17-079G-G1

58.6 Road (Kimball Creek) Project No. 17-079G-G1 Mesa County, Colorado

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TABLE OF CONTENTS

1.0 PROJECT INFORMATION .................................................................................. 1

1.1 Purpose and Scope .................................................................................. 1 1.2 Site Conditions ......................................................................................... 1 1.3 Proposed Construction ............................................................................. 1

2.0 SITE INVESTIGATION ........................................................................................ 2

2.1 Subsurface Investigation .......................................................................... 2 2.2 Subsurface Conditions ............................................................................. 2 2.2.1 Groundwater ........................................................................................ 3

3.0 SITE GRADING ................................................................................................... 3

4.0 RETAINING WALL RECOMMENDATIONS ......................................................... 4

4.1 Lateral Earth Pressures ............................................................................ 5 5.0 CONCRETE ........................................................................................................ 6

6.0 PAVEMENT RECOMMENDATIONS ................................................................... 6

6.1 Subgrade Strength Evaluation .................................................................. 6 6.2 Hot Mix Asphalt Pavement Design ........................................................... 7 6.2.1 Hot Mix Asphalt Type ........................................................................... 8

6.3 Pavement Subgrade Preparation ............................................................. 8 6.4 Drainage Considerations .......................................................................... 9

7.0 LIMITATIONS ...................................................................................................... 9

LIST OF FIGURES

Figure 1 – Approximate Test Hole Locations

LIST OF APPENDICES

Appendix A – Logs of Exploratory Borings

Appendix B – Laboratory Test Results

Appendix C – Pavement Calculations


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1.0 PROJECT INFORMATION 1.1 Purpose and Scope

This report presents the results of our geotechnical investigation and pavement design for the

58.6 Road (Kimball Creek Road) improvements from 58.9 Road (Buzzard Creek Road) to 58.7

Road in Mesa County, Colorado. The project includes improvements and realignment of this

portion of 58.6 Road, also known as Kimball Creek Road. The purpose of this study was to

evaluate the geotechnical characteristics of the on-site soils and provide retaining wall

recommendations and pavement designs for the proposed roadway.

The site investigation consisted of geologic reconnaissance and exploratory test hole drilling to

investigate subsurface conditions. Test hole drilling was observed by a representative of RJ

Engineering. Samples obtained during the field exploration were examined by the project

personnel and representative samples were subjected to laboratory testing to determine the

engineering characteristics of materials encountered. This report summarizes our field

investigation, the results of our analyses, and our conclusions and recommendations based on

the proposed construction, site reconnaissance, subsurface investigation, and results of the

laboratory testing.

1.2 Site Conditions The project area is located on Kimball Creek Road from 58.9 Road (Buzzard Creek Road) to

58.7 Road in Mesa County, Colorado. The roadway steeply climbs upward from Buzzard Creek

Road to 58.7 Road. The total elevation change is about 120 feet. The adjacent properties

consist of gently to steeply sloping topography with localized areas of very steep cut slopes on

the uphill side and very steep fill slopes on the downhill side of the roadway. A residential drive

accesses the roadway near the top of the hill on the northern end of the site.

1.3 Proposed Construction The project consists of reconstruction of Kimball Creek Road from Buzzard Creek Road to 58.7

Road. Plans were not available at the time of this report. We anticipate cut walls will be

planned on the uphill side of the roadway to accommodate drainage and widening of the

roadway. In addition, fill walls or reinforced slopes may be planned on the downhill side of the


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road. Cut walls will likely be a soil nail system, and fills walls will be gravity, MSE or

conventional cast-in-place. We anticipate maximum wall heights of 10 to 15 feet.

2.0 SITE INVESTIGATION 2.1 Subsurface Investigation

Five test holes were drilled on January 9, 2018. The approximate locations of the test holes are

presented on Figure 1. All test holes were drilled within the existing roadway. All test holes

were advanced with a CME 55 rubber track rig using 4-inch continuous flight auger to pre-

determined depths where a modified California or standard split-spoon sampler was used to

record blow counts and obtain samples. Bulk samples were also obtained at depths indicated

on the test hole logs presented in Appendix A.

To perform the modified California penetration resistance tests, a 2.0-inch inside diameter

sampler was seated at the bottom of the test hole, then driven up to 12 inches with blows of a

standard hammer weighing 140 pounds and falling 30 inches utilizing an “auto” hammer (ASTM

D1586). The number of blows (Blow Count) required to drive the sampler 12 inches or a

fraction thereof, constitutes the N-value. The N-value, when properly evaluated, is an index of

the consistency or relative density of the material tested. Split spoon samples are obtained in

the same manner, but with a 1.5-inch inside diameter sampler. Test hole logs and legend are

presented in Appendix A.

2.2 Subsurface Conditions Subsurface conditions generally consisted of asphalt underlain by varying amounts of fill or

sand with gravel, cobbles and boulders. Asphalt and base coarse was encountered at select

test hole locations. Table 1 below summarizes asphalt and base course thicknesses

encountered. Fill consisting of clay with sand and gravel underlain by a natural clay was

encountered in test hole TH-4. Sand with gravel and abundant cobbles and boulders was

encountered in the remaining test holes. Sandstone bedrock was encountered at a depth of 13

feet in test hole TH-3. The fill and natural clay was generally stiff to very stiff. The sands were

medium dense to very dense.


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Table 1 – Asphalt and Base Course Thicknesses

Test Hole Asphalt Thickness (inches)

Base Course Thickness (inches)

TH-1 8 10

TH-2 5 19

TH-3 4 None detected

TH-4 5 None detected

TH-5 None None detected

Two fill and natural clay samples had 53 and 82 percent fines (material passing the No. 200

sieve). Atterberg limit testing indicated the fill sample had a liquid limit of 32 percent and

plasticity index of 17 percent. Seven sand samples had 22 to 46 percent fines and liquid limits

of 20 to 32 percent and plasticity indices of 3 to 15 percent. The existing fill sample classified as

sandy, low plasticity clay (CL), the clay sample classified as a silty, low plasticity clay (CL), and

the sands as silty to slightly clayey with gravel (SC-SM, SM and SC) according to the Unified

Soil Classification System (USCS). A combination sample of test holes TH-3 and 4 was

subjected to Hveem (R-value) testing (ASTM 2844) and resulted in an R-value of 30 at an

exudation pressure of 300 psi. Chemical testing results for water soluble sulfate content are

presented under section 5.0. Results of the laboratory testing are included in Appendix B and

are summarized in the Summary of Laboratory Test Results.

2.2.1 Groundwater

Groundwater was not encountered in any test holes during drilling. The test holes were

backfilled after drilling for public safety. Variations in groundwater conditions may occur

seasonally. Local structure could cause localized areas of perched groundwater. In addition,

the amount of spring snowmelt, duration and intensity of precipitation, and the surface and

subsurface drainage characteristics of the surrounding area could also cause areas of localized

ground water.

3.0 SITE GRADING Site grading plans were not available at the time of our investigation. We anticipate minor cuts

and fills within the roadway alignment to achieve final grades. For wall areas, we anticipate cuts


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and fills of up to about 10 to 15 feet. Based on our drilling and observations, we believe that the

materials encountered can be excavated by conventional construction equipment. We

recommend cut and fill slopes be constructed no steeper than 2H:1V. However, to reduce the

potential for erosion and surface instability, fill slopes of 3H:1V should be considered. If steeper

fill slopes are necessary, reinforced soil slopes can be designed to accommodate areas where

steeper fill slopes are required.

The on-site (cut) soils can be used in site grading fills provided the material is substantially free

of organic material, debris and particles are no larger than 6 inches. Onsite soils should not be

used below pavement areas. Areas to receive fill should be stripped of vegetation, organic soils

and debris. Topsoil is not recommended for fill material. Fill should be placed in thin, loose lifts

of 8 inches thick or less. We recommend fill materials be moisture conditioned to within 2

percent of optimum moisture content and compacted to at least 95 percent of maximum

standard Proctor dry density (ASTM D 698). Placement and compaction of fill should be

observed and tested by a geotechnical engineer.

4.0 RETAINING WALL RECOMMENDATIONS We anticipate soil nail walls will be required on the downhill side at 58.9 Road intersection to

accommodate phased construction and to provide room for the intersection realignment. For

soil nail walls, design parameters are typically selected by the engineer based on anticipated

installation and equipment used for constructing the wall. We are available to discuss design

options and alternatives for soil nail systems.

Fill walls may be necessary on the downhill side of the roadway to accommodate a wider

roadway platform and reduce the height of uphill cut walls. As an alternative, reinforced soil

slopes may be used in lieu of retaining walls on the downhill side of the roadway.

Foundations should be constructed on undisturbed natural soils. Loose, disturbed soils

encountered at foundation level should be removed and the foundation should be extended to

natural soils and/or replaced with properly compacted fill. We recommend fill be placed in

accordance with the specifications presented in section 3.0. The proposed retaining wall could


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be constructed as a cast-in-place concrete, gravity or MSE wall or a soil nail wall system. The

type of wall selected would depend on space constraints, wall height and budget.

1. Footings should be placed on undisturbed natural soils. Foundations can be designed for a maximum allowable soil pressure of 2,500 psf. Based on experience, we anticipate settlement of footings designed and constructed as recommended will be about 1-inch or less.

2. Using Load Resistance Factor Design criteria (LRFD), a nominal bearing capacity can be determined for shallow spread footing foundations placed on properly placed and compacted structural fill using the following equation based on a minimum footing width of 6 feet:

qn = 6.36 + 0.32*(B-2*e) where: qn – nominal bearing capacity in ksf B – footing width in feet e – eccentricity in feet

3. A coefficient of friction of 0.30 may be used for the calculation of sliding resistance when performing an external stability check.

4. Passive pressure against the sides of the footings can be used for sliding resistance and

can be calculated using an equivalent fluid unit weight of 350 pcf if granular backfill is used.

5. The soils below foundations should be protected from freezing. We recommend the bottom of foundations be constructed at least 3.0 feet below finished grade or as required by local municipal code for cast-in-place structures. For MSE walls, we recommend a minimum embedment of 1-foot below finish grade.

6. Retaining walls acting as retaining structures should be designed to resist lateral earth pressures as discussed in section 4.1 below.

7. All foundation excavations should be observed by a representative of a geotechnical engineer prior to placement of concrete.

4.1 Lateral Earth Pressures Retaining walls should be designed to resist lateral earth pressure. Retaining walls can be

backfilled with on-site or imported granular soils. For a horizontal backslope for properly placed

and compacted fill, the unfactored earth pressure can be estimated using an equivalent fluid

pressure of 50 pcf for the active condition and 65 pcf for an at-rest condition. For wall backfill

consisting of CDOT Class 1 structure backfill, walls can be designed using an equivalent fluid


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density of 40 pcf for active or 60 pcf for at rest conditions. Site retaining walls that can be

expected to deflect to mobilize the full active earth pressure condition could be designed using

an equivalent fluid pressure for active conditions. These values assume that the backfill

materials are not saturated. Wall designs should consider the influence of surcharge loading

such as traffic, construction equipment and/or sloping backfill.

Retaining walls and structures should be constructed with a drainage system to drain away any

excess water immediately behind the wall. The drainage system may consist of free-draining

gravel, pipes, drain board and/or weep holes are commonly used for wall drainage.

5.0 CONCRETE Two subsoil samples were subjected to water-soluble sulfate testing. The samples exhibited

concentrations of 0.019 and 0.096 percent which are considered negligible/low (Class 0

exposure) degree of sulfate attack for concrete exposed to these materials. The degree of

attack is based on a range of 0.00 to less than 0.10 percent water-soluble sulfates as presented

in the American Concrete Institute Guide to Durable Concrete. Due to the negligible/low

degree, no special requirements for concrete are necessary for this site.

6.0 PAVEMENT RECOMMENDATIONS Traffic information for the design of 58.6 Road was provided by the client. Twenty-year flexible

pavement Equivalent Single Axle Loads (ESALs) were calculated and used for thickness

designs. Table 2 presents a summary of the ESAL values used as pavement design inputs.

Traffic calculations and information used in the designs is presented in Appendix C.

Table 2 – Design Traffic Loading

Roadway Segment 20-Year Flexible ESALs

58.6 Road 220,088

6.1 Subgrade Strength Evaluation Based on the results of our field exploration and laboratory testing, the subgrade materials

below pavements as classified by the American Association of State Highway and


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Transportation Officials (AASHTO) consisted of A-2-4 to A-6(6). R-value testing was performed

and resulted in an R-value of 30 for the A-6 material. A design R-value of 30 was selected

based on our experience.

We recommend new fill material placed within the proposed roadway alignment below the

aggregate base course (ABC) meet a minimum R-value of 30. Aggregate base course (ABC)

should meet CDOT Class 6 specifications and have a minimum R-value of 78. The subbase

should meet CDOT Class 2 or 3 specifications and have a minimum R-value of 59.

6.2 Hot Mix Asphalt Pavement Design For the hot mix asphalt (HMA) pavement thickness designs, resilient modulus of 6,849 psi was

calculated from the R-value of 30 using the AASHTO Design Manual. Table 3 presents the

input design parameters used for the designs of flexible pavement sections for 58.6 Road.

Table 3– Flexible Pavement Design Parameters for 58.6 Road HMA Design Inputs

Initial Serviceability 4.2 Reliability Level, % 90

Terminal Serviceability 2.5 Subgrade Resilient Modulus, MR, psi 6,849

Design Subgrade R-value 30 HMA Str. Layer Coefficient 0.44

20 Year Design ESAL 220,088 ABC Str. Layer Coefficient 0.15

Subbase Str. Layer Coefficient 0.11

A pavement section is a layered structure designed to disperse dynamic traffic loads to the

subgrade. The performance of the pavement structure depends on the traffic loadings and

physical properties of the subgrade materials. Recommended pavement design thickness

sections are summarized below.

HMA pavement design calculations were performed using the guidelines from the AASHTO

Design Manual. Calculations for all pavement designs are presented in Appendix C. HMA

pavement thicknesses presented are rounded up to the nearest half-inch. HMA pavement

thicknesses are based on 20-Year ESAL loadings and are presented in Table 4.


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Table 4 – Recommended Pavement Sections for 58.6 Road

Roadway Pavement Type Design Life (years) Thickness (inches)

58.6 Road

HMA 20 6.5” HMA

HMA + ABC 20 5” HMA + 5” ABC

HMA + ABC + Subbase 20 5” HMA + 4” ABC + 4” Subbase

6.2.1 Hot Mix Asphalt Type

We recommend that the asphalt mix for this project meet the specifications for Grading SX (75)

in accordance with the specifications. The number of SuperPave Gyratory revolutions (Ndes)

for the asphalt mixes should be at 75 gyrations is recommended if the design ESALs are below

3 million. We recommend that unmodified performance grade asphalt binder meeting the

CDOT requirements for performance grade PG 58-28 be used in both the lower and top lifts for

58.6 Road. PG 58-28 is a 98% reliability binder for both binder rutting resistance and thermal

cracking for the Collbran area based on data from the FHWA Binder Selection Program, LTPP

Bind. The lower lift should meet the requirements for SX (75) and be placed at thicknesses of

three inches. The top 2-inch lift should conform to SX (75) with PG 58-28 binder.

Aggregates for hot plant mix bituminous pavement should be of uniform quality, composed of

clean, hard, durable particles of crushed stone, gravel, or slag. Excess of fine material should

be wasted before crushing. The specified gradations for the above mixes are published in

Tables 703-4 and 703-5 of the 2017 CDOT Standard Specifications.

6.3 Pavement Subgrade Preparation We recommend that the top 6 inches of the subgrade for the entire roadway width be scarified

and recompacted in compliance with CDOT Standard Specifications. We recommend that a

separator geotextile Class 1 conforming to the requirements listed in Section 712.08 of the 2017

CDOT Standard Specifications be placed between the subgrade and the ABC Class 6 or Class

2 in conformance with Section 420.07 where subgrade soils consist of clay. Based on our


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investigation, clay was encountered in the area of test hole TH-4. The subgrade and ABC

should be compacted in accordance with the requirements shown in Section 203.07 of the 2017

CDOT Standard Specifications.

The pavement subgrade should be proof rolled with a heavily loaded pneumatic-tire vehicle.

Areas that deform more than ½-inch under heavy wheel loads should be removed, replaced if

necessary and reworked to achieve a stable subgrade prior to paving. We recommend that

proof rolling and compaction tests be observed and documented by a representative of the

engineer.

6.4 Drainage Considerations The collection and diversion of surface drainage away from paved areas is critical to the

satisfactory performance of the pavement. Proper drainage design should include prevention of

ponding of water on or immediately adjacent to pavement areas. Concentrated runoff should be

avoided in areas susceptible to erosion. Slopes and other stripped areas should be protected

against erosion by re-vegetation or other methods.

7.0 LIMITATIONS This study was conducted in accordance with generally accepted geotechnical engineering

practices in this area for use by the client for design purposes. The conclusions and

recommendations submitted in this report are based upon the data obtained from exploratory

test holes, field reconnaissance and anticipated construction. The nature and extent of

subsurface variations across the site may not become evident until excavation is performed. If

during construction, conditions appear to be different from those described herein; this office

should be advised at once so reevaluation of the recommendations may be made. We

recommend on-site observation of excavations by a representative of the geotechnical

engineer.

The scope of services for this project did not include, specifically or by implication, any

environmental or biological (e.g., mold, fungi, and bacteria) assessment of the site or

identification or prevention of pollutants, or conditions or biological conditions. If the owner is


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concerned about the potential for such contamination, conditions or pollution, other studies

should be undertaken.

The report was prepared in substantial accordance with the generally accepted standards of

practice for geotechnical engineering as exist in the site area at the time of our investigation.

No warranties, express or implied, are intended or made.

Respectfully Submitted:

RJ Engineering & Consulting, Inc.

Richard D. Johnson, P.E. Project Manager

TH-1

TH-2

TH-3

TH-4

TH-5

TH-1

LEGEND:

Indicates approximate test hole location

1. Base drawing from Google Earth.

NOTES:

Approximate

Test Hole Locations

0 100'200'

Figure

1

SCALE: 1" = 200'

N

58.6 Road (Kimball Creek), Mesa County

PROJECT NO:PROJECT:

17-079G-G1


APPENDIX A

Logs of Exploratory Borings


APPENDIX B

Laboratory Test Results

Project No:

Grain Size Analysis Atterberg Limits

TH-1 0-4 Bulk 7.2 24 50 26 20 17 3 SAND, silty (SM)

TH-2 4 CA 8.4 109 31 SAND, silty (SM)

10-18 Bulk 3.9 19 59 22 SAND, silty (SM)

TH-3 0-4 Bulk 5.0 29 21 15 6 SAND, silty to clayey (SC-SM)

4 CA 11.9 112 46 0.096 SAND, silty (SC)

10-13 Bulk 5.6 21 40 39 SAND, clayey (SC)

TH-4 0-4 Bulk 11.4 53 32 15 17 FILL, clay, sandy (CL)

4 CA 18.8 96 82 0.019 CLAY, sandy (CL)

TH-5 0-4 Bulk 6.4 44 32 17 15 SAND, clayey (SC)

TH-3 & 4 0-4 Combo 6.6 16 43 41 25 14 11 30 SAND, clayey (SC)

LL (%)

58.6 Road, Mesa County

PI (%)

Description

Water Soluble Sulfate

(%)

R-value at 300

psi

RJ Engineering & Consulting, Inc.

Sample Type

Dry Density (pcf)

Gravel > #4 (%)

Moisture Content

(%)PL (%)

Sample Location

Test Hole Depth (ft)

Summary of Laboratory Test Results

Sand (%)

17-079G-G1 Project Name:

Fines < #200

(%)

CA-Indicates modified California samplerBulk-Indicates bulk sample from auger cuttings Page 1 of 1

Sample Description: Gravel (%) 24 Liquid Limit (%) 20From: Sand (%) 50 Plastic Limit (%) 17

Silt & Clay (%) 26 Plasticity Index (%) 3

Sample Description: Gravel (%) 19 Liquid Limit (%)From: Sand (%) 59 Plastic Limit (%)

Silt & Clay (%) 22 Plasticity Index (%)

17-079G-G1B-1

SAND, silty (SM)TH-1 at 0-4 feet

SAND, silty (SM)TH-2 at 10-18 feet

SIEVE ANALYSIS Project No.:Figure No.:

0

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0.010.11101001000

Perc

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assi

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Particle Size (mm)

20040103/8" 41/2"3/4"3"12" 6" 1" 30 508 16

Sieve Analysis Hydrometer Analysis

Sieve Opening in Inches U.S. Standard Sieves Size in mm

1002"

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20040103/8" 41/2"3/4"3"12" 6" 1" 30 508 16 1002"

Sample Description: Gravel (%) 21 Liquid Limit (%)From: Sand (%) 40 Plastic Limit (%)

Silt & Clay (%) 39 Plasticity Index (%)

Sample Description: Gravel (%) 16 Liquid Limit (%) 25From: Sand (%) 43 Plastic Limit (%) 14

Silt & Clay (%) 41 Plasticity Index (%) 11

17-079G-G1B-2

SAND, silty (SC-SM)TH-3 at 10-13 feet

SAND, clayey (SC)TH-3 & 4 at 0-4 feet

SIEVE ANALYSIS Project No.:Figure No.:

0

10

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0.010.11101001000

Perc

ent P

assi

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Particle Size (mm)

20040103/8" 41/2"3/4"3"12" 6" 1" 30 508 16



1002"

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0.010.11101001000

Perc

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20040103/8" 41/2"3/4"3"12" 6" 1" 30 508 16 1002"


APPENDIX C

Pavement Calculations

TRAFFIC LOADINGFlexible (HMA) Design58.6 Road (Kimball Creek) Project No. 17-079G

Current ADT: 161 vehicles per day Design Life = 20 yearsProjected ADT: 235 vehicles per dayAverage ADT: 198 vehicles per day Growth Rate = 1.9% per year

Projected ADT = 235 vehicles per day

Separate Equivalency EquivalentADT Factor ADT

Combination Trucks: 22% 44 1.087 47Single Unit Trucks: 5% 10 0.249 2Cars & Light Trucks: 73% 145 0.003 0

100% 198 50

Total ESAL: 366,814Lanes per direction: 1 lane(s)Lane Factor: 0.6

Design ESAL: 220,088

Anticipated Traffic

AASHTO PAVEMENT DESIGNFlexible (HMA) Design58.6 Road (Kimball Creek) Project No. 17-079G

R-value = 30S1 = 5.214Mr = 6,849 psiW18 = 220,088Log(W18)= 5.343Reliability = 90 %ZR = -1.282Deviation, So = 0.49po = 4.2

pt = 2.5∆psi = 1.7Log(W18)= 5.343Difference = 0.000

Design SN = 2.86

Structural Drainage Thickness Width Calculated SNLayer Material Coefficient Coefficient (inches) (feet) (inches)

HMA 0.44 1 6.5 12 2.86Totals - - 6.5 - 2.86


HMA 0.44 1 5.0 12 2.20ABC 0.15 1 5.0 12 0.75

Totals - - 10.0 - 2.95


HMA 0.44 1 5.0 12 2.20ABC 0.15 1 4.0 12 0.60

Subbase 0.11 1 4.0 12 0.44Totals - - 13.0 - 3.24

ABC - Aggregate Base Course consisting of CDOT Class 6 (R-value > 78)Subbase - Subbase consisting of CDOT Class 1 or 2 (R-value > 69)

Full Depth Hot Mix Asphalt (HMA)

Hot Mix Asphalt (HMA) over Aggregate Base Course (ABC)

Hot Mix Asphalt (HMA) over Aggregate Base Course (ABC) over Subbase

Documents

GEOTECHNICAL ENGINEERING REPORT...Oct 01, 2018 · This report presents the results of our geotechnical investigation and pavement design for the 58.6 Road (Kimball Creek Road) improvements