HomeMy WebLinkAbout020 - Appendix Q.2 - Geotechnical_PavementSections mw�I��� �
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RRawhide
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Engineering Inc.
g 6871 King Avenue West,Suite G1 K,Billings,MT 59106(406)969-5305
October 26, 2023
Mr. Rob Lateiner
Virga Capital
PO Box 1070
Bozeman, MT 59771
SUBJECT: Pavement Sections
Turnrow Subdivision
Davis Lane &Valley Center Road
Bozeman, Montana
Dear Mr. Lateiner:
Rawhide Engineering was requested to design pavement sections for subdivision roads, inverted
alleys, collector streets and Valley Center to Davis Lane in the Turnrow Subdivision in Bozeman,
Montana. The project consists of designing pavement sections.
Rawhide Engineering excavated 10 exploratory test pits to a depth of 8.0 to 10.0 feet below
existing site grades. The site had six inches of topsoil with vegetation which was underlain by
silty clay with sand to depths 3 to 8 feet below existing site grades. Beneath the silty clay with
sand we encountered dense sand with gravel to the depths explored. The test pit logs should be
reviewed at each location that are included in the preliminary report from April 2021. Groundwater
was not encountered at the depths explored during our exploration in April 2021.
LABORATORY TESTING
A laboratory testing program was utilized to provide the necessary data for engineering analysis
of this project. The testing was used to evaluate the index and engineering properties specifically
for the conditions encountered during our field exploration. The following program was used for
this project.
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Moisture Content Tests—ASTM D2216
Moisture content tests were conducted on selected samples obtained from the site. These tests
were used to aid in identifying the current soil conditions and aid in classifying the soils. Moisture
content tests are shown on the boring logs.
Soil Classification Tests—ASTM D422, D1140, D4318, D2487 and D2488
In order to classify the soils according to the Unified Classification System, soil gradations and
Atterberg Limits test were conducted on selected samples. The results of this testing is shown
below and on the boring logs.
Pavement Sections
The recommended pavement structural section for the project presented below was calculated
using the AASHTO pavement design procedure. Traffic loading information was provided by
Sanderson Stewart for each of the road categories. In our analysis, we have used inverted alleys
of 80,000 ESAL's. Interior streets ESAL's of 164,000, Collector streets ESAL's of 360,000 and
Valley Center of 425,000 (18-kip ESAL) for the lifetime of the pavement section. A CBR value
of 3.0 was used for design of the pavement sections.
The existing vegetation should be removed from the site. The subgrade should be compacted to
95% of ASTM D698 prior to placing the base course. Valley Center and Davis Lane was not
investigated due to the utility locations and is based on recommendations from MDT.
PAVEMENT STRUCTURAL SECTIONS
Traffic Condition Recommended Minimum Structural Section
Inverted Alleys 3 inches of Asphaltic Concrete on 8 inches of crushed
Base Course
Interior Streets Asphalt Section 3 inches of Asphaltic Concrete on 6 inches of 1 '/2"
Crushed Base Course on 10 inches of pit run gravel
Collector Streets Asphalt Section 4 inches of Asphaltic Pavement on 8 inches of 1 W
Crushed Base Course on 12 inches of pit run gravel
Valley Center— Davis Lane Asphalt 4 inches of Asphaltic Concrete of 8 inches of Crushed
Sections Base Course on 14 inches of pit run gravel
Aggregate base course thickness may be reduced in each alternate pavement structural section
by approximately 20% with the use of geotextile fabric meeting AASHTO M 288-2000 class 1
requirements. If this alternative is selected, we can provide addition pavement structural sections.
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It should be noted that the subgrade soils are likely to be prone to frost action during the winter
and saturation during the wet spring months. The primary impact of frost action and subgrade
saturation is the loss of subgrade and aggregate base strength. Pavement life will be increased
if efforts are made to reduce the accumulation of excess moisture in the subgrade soils.
Subgrade and Aggregate Base
Subgrade Preparation -After completion of the utility trench backfill and prior to
placement of aggregate base, the upper six inches of subgrade soil shall be
uniformly compacted to at least 95% relative compaction. This may require
scarifying, moisture conditioning, and compacting in both cut and fill areas.
Aggregate Base - Aggregate materials shall meet the requirements of the
appropriate sections of the "Standard Specifications"for 1 % Minus Crushed Base
Rock. The aggregate base materials must be approved by the Geotechnical
Engineer prior to use.
After the subgrade is properly prepared, the aggregate base shall be placed in
layers, moisture conditioned as necessary, and compacted by rolling to at least
95% relative compaction. The compaction thickness of aggregate base shall be
as shown on the approved plans.
Asphalt Concrete Pavement
Materials-Aggregate materials for asphalt concrete in light and heavy traffic areas
shall conform to the requirements listed for Type B bituminous aggregates of the
"Standard Specifications." Asphalt concrete mixes shall utilize asphalt cement
meeting the requirements of Section 02510 of"Standard Specifications". The mix
design shall be based on the Marshall Method.
Placement and Compaction - The asphalt concrete material and placement
procedures shall conform to appropriate sections of the"Standard Specifications."
The asphalt concrete material shall be compacted to a minimum of 93% of the
Theoretical Maximum Rice Specific Gravity.
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We appreciate this opportunity to be of service to you, and look forward to future endeavors. If
you have any questions regarding this report or need additional information or services, please
feel free to call the undersigned.
Sincerely,
RAWHIDE ENGINEERING, INC.
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ROBERT WAYNE
KUKES
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Robert /cENSE :. -43
Principal
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