Scour at Bridge Foundations on Rock: Status of NCHRP Project 24-29 Jeffrey R. Keaton, Principal Investigator MACTEC Engineering and Consulting, Inc. Los Angeles, CA Su K. Mishra, Co-Principal Investigator Ayres Associates, Inc. (now with HDR) Sacramento, CA Project No. 24-29: Scour at Bridge Foundations on Rock Geohazards In Transportation In the Appalachian Region 04 Aug 2010
32
Embed
Scour at Bridge Foundations on Rock: Status of …...Scour at Bridge Foundations on Rock: Status of NCHRP Project 24-29 Jeffrey R. Keaton, Principal Investigator MACTEC Engineering
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Scour at Bridge Foundations on Rock:
Status of NCHRP Project 24-29Jeffrey R. Keaton, Principal Investigator
MACTEC Engineering and Consulting, Inc.Los Angeles, CA
Su K. Mishra, Co-Principal InvestigatorAyres Associates, Inc. (now with HDR)
Sacramento, CA
Project No. 24-29: Scour at Bridge Foundations on Rock
Geohazards In TransportationIn the Appalachian Region04 Aug 2010
NCHRP 24-29 Objectives
• Develop a methodology for determining– Design scour depth– Time-rate of scour
• Develop design and construction guidelines for applying the methodology
2
"Far better an approximate answer to the right question, which is often vague, than an exact answer to the wrong question, which can always be made precise."
John W. Tukey, 1962, The future of data analysis: Annals of Mathematical Statistics, v. 33, p.13
Bridge Sites
3
OregonDOT;
OregonState U
CaliforniaDOT
UtahDOT
FloridaDOT;Universityof Florida
New YorkState ThruwayAuthority;New YorkStateDOT;USGS
Chipola River – I-10
4
Oligocene marine dolomitic limestone
Rotating Erosion TestApparatus (RETA)
Mill Creek – OR SR-22
5Oligocene marine siltstone
WaterFlow
downstream
WaterFlow
Schoharie Creek – I-90
6
Paleozoic marine sandstone
Quaternary ice-contact stratified drift
Schoharie Creek Gage
Montezuma Creek – UT SR-262
7September 2003
Average annual precipitation = 8.43”100-yr, 24-hr precipitation = 2.62”
Gage 1 mile downstream15 yrs of data 1963 – 93(Source: HDR 2003 report)
Montezuma Creek – UT SR-262
8
Headcut > 2.5 m
Jurassic fluvial interbeddedsandstone and claystone
Sacramento River – CA SR-273
9
Cretaceous marine siltstone
Rock Scour Flow Diagram
Modes ofScour
10
Quantify modes that applyDismiss modes that don’t
11
Soluble Rock
Bridges are not founded on rocks that dissolve in engineering time (halite, sylvite, gypsum)
12
Cavitation
13
Degradable Rocks
October 1, 2008
1:36 pm
August 6, 200812:03 pm
14
Durable Rocks
Erik Bollaert, AquaVision Engineering
Degradable Rock Scour Procedure
15
Rock scour is a“rock-water interaction “
problem
Gage & Cross Section Data
16
Unit stream power= d S v = v
3/1
2
486.1 dv n
3v
22 ftslbft
sft
ftlb
Gage Data; No Cross Section
17
Cross Section; No Gage Data
18
No Gage or Cross Section Data
19
Stream Gage Data
20
Repeated Cross Sections
21
Cretaceousmarinesiltstone
Cumulative Stream Power
22
Stream power can be accumulated over time;Neither velocity nor shear stress can be accumulated