STO18L80332_-_Bridalveil_Addendum_Letter_Amd3_0003.pdf
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- YOSE 215798 - Bridalveil Fall Comfort Station
- Solicitation number
- 140P2022R0038
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This addendum letter provides recommendations for rock anchors and shallow drilled pier foundations for an elevated walkway portion of the Bridalveil Fall Rehabilitation project in Yosemite National Park, California. It discusses using rock anchors and shallow drilled pier foundations to support spans of the elevated pathway and bridges of up to 40 feet. It recommends an unconfined compressive strength of 3,600 psi be used for design of the rock anchors. It also provides factored frictional resistance coefficients of 0.4 for service loads and 0.8 for extreme loads. Due to potential erosion or degradation of any sediment above bedrock and uncertain complexity of localized jointing, conventional passive pressure should not be considered. An engineering geologist and geotechnical engineer should observe foundation excavations to confirm no adverse localized geologic structures exist.
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20184025.001A/STO18L80332 Page 1 of 2 June 22, 2018 © 2018 Kleinfelder www.kleinfelder.com
KLEINFELDER 2001 Arch-Airport Road, Suite 100, Stockton, CA 95206 p | 209.948.1345 f | 209.234.4700
June 22, 2018 Kleinfelder Project No. 20184025.001A
Mr. John N. Roberts John Northmore Roberts & Associates 2927 Newbury Street, Suite B Berkeley, CA 94703
Subject: Addendum to Geotechnical Services Report Proposed Bridalveil Fall Rehabilitation Yosemite National Park, California
Reference: “Geotechnical Services, Proposed Bridalveil Fall Rehabilitation, Yosemite National
Park, California,” File No. 20184025.001A, dated May 18, 2018.
Dear Mr. Roberts:
This letter is an addendum to the referenced report prepared for the proposed Bridalveil Fall Rehabilitation project in Yosemite National Park, California. The purpose of this letter is to provide recommendations for rock anchors and shallow drilled pier foundations for the elevated walkway portion of the project.
It is understood the project will include 700 linear feet of elevated pathways and bridges capable of spanning about 40 feet. The spans will be supported rock anchors and shallow drilled pier foundations.
Based on our field observations and experience in the area, the rock encountered along the proposed elevated walkway path predominantly consisted of strong to very strong rock with estimated unconfined compressive strengths in the range of 7,250 – 36,000 pounds per square inch (psi). However, some rock can be classified as medium strong with unconfined compressive strengths in the range of 3,600 – 7,250 psi. It is recommended that an unconfined compressive strength of 3,600 psi be used for design of the rock anchors.
Based on the estimated unconfined compressive strength of the sound granitic rock, the available allowable bond strength is potentially very high (180 psi). The available allowable bond strength of the foundation concrete would be limited to 5% of the compressive strength of the concrete (typically greater than 200 psi). Considering these high values, resistance to lateral loads should utilize the equivalent frictional coefficients presented in Table 1. As a note, the data is presented as factored resistance. The factored value with =0.5 would be an allowable value and the value with =1.0 would be the ultimate or unfactored nominal value.
http://www.kleinfelder.com/
20184025.001A/STO18L80332 Page 2 of 2 June 22, 2018 © 2018 Kleinfelder www.kleinfelder.com
KLEINFELDER 2001 Arch-Airport Road, Suite 100, Stockton, CA 95206 p | 209.948.1345 f | 209.234.4700
Table 1 Frictional Coefficients
Service
=0.5
Extreme
=1.0
Frictional Coefficient 0.4 0.8
Because any sediment above bedrock could be subject to erosion or degradation and uncertain complexity of localized jointing, conventional passive pressure should not be considered. It is recommended an engineering geologist and geotechnical engineer observe the foundation excavation to confirm no adverse localized geologic structure exists.
We trust this letter presents the information requested. The limitations discussed in the referenced report also apply to the recommendations contained in this letter. If you need any further assistance, please contact our office.
Respectfully, KLEINFELDER, INC.
James A. Wetenkamp, C.E.G., No. 2556 Project Engineering Geologist
Reviewed by:
Nathan L. Dahlen, PE, No. C71344 Senior Engineer
JW/ND:bn http://www.kleinfelder.com/
File details come from the government source that posted it. Updated .