1、G E O T E C H N I C A L P R A C T I C E P U B L I C A T I O N N O . 7 GEOCHALLENGES RISING TO THE GEOTECHNICAL CHALLENGES OF COLORADO PROCEEDINGS OF THE 2012 BIENNIAL GEOTECHNICAL SEMINAR November 9, 2012 Denver, Colorado SPONSORED BY The Geo-Institute of the American Society of Civil Engineers Geo-
2、Institute Chapter of the Colorado Section of the American Society of Civil Engineers Rocky Mountain Section of the Association of Environmental and Engineering Geologists Colorado Association of Geotechnical Engineers EDITED BY Christoph M. Goss, Ph.D., P.E. Jere A. Strickland, P.E. Richard L. Wilts
3、hire, P.E. Published by the American Society of Civil Engineers Cataloging-in-Publication Data on file with the Library of Congress. American Society of Civil Engineers 1801 Alexander Bell Drive Reston, Virginia, 20191-4400 www.pubs.asce.org Any statements expressed in these materials are those of t
4、he individual authors and do not necessarily represent the views of ASCE, which takes no responsibility for any statement made herein. No reference made in this publication to any specific method, product, process, or service constitutes or implies an endorsement, recommendation, or warranty thereof
5、 by ASCE. The materials are for general information only and do not represent a standard of ASCE, nor are they intended as a reference in purchase specifications, contracts, regulations, statutes, or any other legal document. ASCE makes no representation or warranty of any kind, whether express or i
6、mplied, concerning the accuracy, completeness, suitability, or utility of any information, apparatus, product, or process discussed in this publication, and assumes no liability therefore. This information should not be used without first securing competent advice with respect to its suitability for
7、 any general or specific application. Anyone utilizing this information assumes all liability arising from such use, including but not limited to infringement of any patent or patents. ASCE and American Society of Civil EngineersRegistered in U.S. Patent and Trademark Office. Photocopies and reprint
8、s. You can obtain instant permission to photocopy ASCE publications by using ASCEs online permission service (http:/pubs.asce.org/permissions/requests/). Requests for 100 copies or more should be submitted to the Reprints Department, Publications Division, ASCE, (address above); email: permissionsas
9、ce.org. A reprint order form can be found at http:/pubs.asce.org/support/reprints/. Copyright 2013 by the American Society of Civil Engineers. All Rights Reserved. ISBN 978-0-7844-1263-3 Manufactured in the United States of America. Preface As geo-professionals, we are called to provide solutions fo
10、r the many challenges that our earth presents in the areas we choose to work, play and live. From natures geological features to our worlds aging infrastructure, we are presented with the challenge of developing in areas and in ways that many thought were unbuildable or un-attainable. Yet, through t
11、he use of new technologies, modeling methods and visual mapping, geo-professionals have answered these many challenges by providing viable solutions. This book provides examples of how some in our profession have overcome these types of challenges in mining applications, tunneling, geological anomal
12、ies, alternative energy resources and infrastructure. This will highlight, again, how the geo-professional community provides solutions to the most challenging applications. Since 1984, the Geotechnical Institute Chapter of Colorado (formally known as the ASCE Colorado Sections Geotechnical Group) i
13、n collaboration with the Rocky Mountain Section of the Association of Environmental and Engineering Geologists and the Colorado Association of Geotechnical Engineers, has organized a biennial series of geotechnical seminars on a wide variety of themes that have been attended by as many as 270 civil/
14、geotechnical engineers, geologists, and other geo- professionals. The geotechnical seminars have been held at area universities or hotels and have offered the opportunity for sharing ideas and experiences among Colorados diverse geo-disciplines. Since 2004, ASCEs Geo-Institute has published the pape
15、rs of these seminars in Geotechnical Practice Publications, allowing the experiences to be shared with a worldwide audience. The GeoChallenges Steering Committee convened in August 2011 and held monthly meetings to plan for the 2012 Biennial Geotechnical Seminar. The Steering Committee members inclu
16、ded Joseph Kerrigan (Conference Chair), Dustin Bennetts, Mark Brooks, Robin Dornfest, Darin Duran, Dr. Christoph Goss, Joels Malama, Dr. Bill McCarron, Minal Parekh, Becky Roland, Keith Seaton, Jere Strickland, David Thomas, Mark Vessely Chris Wienecke, and Richard Wiltshire. Christoph Goss, Jere St
17、rickland, and Richard Wiltshire iiiAcknowledgments The GeoChallenges Steering Committee wishes to take this opportunity to thank all of the authors and reviewers of our papers, which are herein presented as Geotechnical Practice Publication No. 7. The authors have spent many hours in preparing and f
18、inalizing their papers, which will be presented at the 2012 Biennial Geotechnical Seminar on November 9, 2012. These papers have been reviewed by a volunteer group of Denver area geo-professionals who put in their valuable time and helped make these papers even better. The Geo-Institutes Committee o
19、n Technical Publications completed its review of our GeoTrends papers in a very timely manner and their adherence to our aggressive publication schedule is greatly appreciated. We would also like to acknowledge the assistance of Donna Dickert of ASCEs Book Production Department for putting this publ
20、ication together. iv v Author List Amundson, Al, 134 Anderson, Scott A., 37 Andrew, Rick D., 76 Bare, Dan, 134 Chang, Nien-Yin, 206 Deere, Don W., 148 DeMarco, Matthew J., 37 France, John W., 54 Friedman, Evan, 17 Gavin, Matt, 54 Hanna, Kanaan, 134 Haramy, Khamis, 76 Hoffman, Peter, 178 Huzjak, Robe
21、rt J., 189 Jurich, David, 230 Kottenstette, Joseph, 98 Kuehr, Steven, 134 Kumar, Narender, 164 Lawson, Tim, 230 McCartney, John S., 217 McCormick, Bill, 54 McDivitt, Joseph, 230 Murphy, Kyle D., 217 Parekh, Minal L., 134 Pauley, Chris, 134 Prochaska, Adam B., 189 Russell, Kendra, 121 Santi, Paul, 1,
22、 17 Simpson, Bryan K., 90 Sirles, Phil, 76 Soule, Nathan, 134 Spitzer, Roy H., 148 Surdahl, Roger W., 76 Volmer, Brian, 206 This page intentionally left blank Contents Challenging Hazards Challenges for Debris-Flow Mitigation in Colorado: Helpful Ideas from Recent Research . 1 Paul Santi Debris-Flow
23、 Hazard Assessment and Model Validation, Medano Fire, Great Sand Dunes National Park and Preserve, Colorado 17 Evan Friedman and Paul Santi Use of Rockfall Rating Systems in the Design of New Slopes 37 Scott A. Anderson and Matthew J. DeMarco Evaluation of Sinkhole at Beaver Park Dam, Colorado, Guid
24、ed by Risk Analysis 54 John W. France, Bill McCormick, and Matt Gav in Nondestructive Evaluation Challenge Seismic and Electrical 3D Imaging to Aid in Landslide Remediation Design, East Fork Landslide, Wolf Creek Pass, Colorado 76 Phil Sirles, Khamis Haramy, Rick D. Andrew, and Roger W. Surdahl Phot
25、ogrammetric Methods, Geologic Discontinuity Mapping for Spillway Modifications, Pathfinder Dam, Wyoming . 90 Bryan K. Simpson Use of Photogrammetric Measurements in a Concrete Damage Survey, Guernsey Dam South Spillway 98 Joseph Kottenstette Balloon Photogrammetry along the Middle Fork, John Day Riv
26、er, Oregon . 121 Kendra Russell Templeton Gap Floodway Levees, Investigation and Mitigation of Mine Subsidence . 134 Nathan Soule, Minal L. Parekh, Steven Kuehr, Al Amundson, Kanaan Hanna, Dan Bare, and Chris Pauley Challenging Ground The Misbehavior of the Laramie Formation Claystones . 148 Roy H.
27、Spitzer and Don W. Deere Effective Use of Underdrain System in Construction on Expansive Subsoils . 164 Narender Kumar Application of Coulombs Method to Reinforced Soil Structures 178 Peter Hoffman Bedrock Settlement beneath a Large Embankment Dam . 189 Robert J. Huzjak and Adam B. Prochaska vii Con
28、structing Challenges Drilled Shaft Responses under Pre-Torsion Lateral or Vertical Loads 206 Brian Volmer and Nien -Yin Chang Behavior of Full Scale Energy Foundations in Denver, Colorado 217 Kyle D. Murphy and John S. McCartney Geotechnical Challenges for the South Coast Water District Tunnel Rehab
29、ilitation and Sewer Pipeline Replacement Project 230 David Jurich, Joseph McDivitt, and Tim Lawson viii Challenges for Debris-Flow Mitigation in Colorado: Helpful Ideas from Recent Research Paul Santi 1 , Ph.D., P.G. 1 Professor, Department of Geology and Geological Engineering, Colorado School of M
30、ines, 1500 Illinois St., Golden CO 80401, psantimines.edu ABSTRACT: A large amount of recent research has focused on debris flow analysis, prediction, and mitigation, particularly in burned areas. Ten concepts from this work are especially applicable in Colorado. 1) Debris flows are larger and more
31、likely to occur following wildfire, and the problem is getting worse due to climate change. 2) After wildfire, vegetation often recovers to pre-fire conditions in one to three years. 3) Volume measurement and related volume prediction methods for debris flows have much larger error ranges than is ty
32、pically assumed. 4) Likewise, measurement and prediction of debris-flow velocities may easily include errors. 5) Impact forces from boulders carried by debris flows are typically overestimated. 6) Flows often occur in surges, probably from creation and breaching of small dams of material. 7) Flow pa
33、ths on open slopes are unpredictable and may change rapidly following development of these small dams. 8) In burned areas, the occurrence of debris flows depends more on rainfall intensity bursts, with flows often occurring within a few minutes of 10-minute intensities exceeding threshold values, th
34、an on total storm rainfall. 9) A corollary is that debris-flow volume, as predicted from multiple- regression datasets, depends more on total rainfall than on shorter intensity ranges. 10) Many flows are comprised more of channel sediment than of materials mobilized from a single slide mass, meaning
35、 that they grow substantially in volume in transit. INTRODUCTION Debris flows are a common and destructive geologic hazard in Colorado. Recent debris flows have covered Interstate 70 in more than 7m of debris, have affected dozens of flow channels following alpine summer cloudbursts (e.g., Coe et al
36、., 2007; Godt and Coe, 2007), and have influenced zoning and building locations in many mountain communities (such as Aspen, Vail, Glenwood Springs, Telluride, Ouray, and Georgetown). Recent wildfires have created conditions where numerous large and destructive debris-flow events have impacted Duran
37、go, Glenwood Springs, and Boulder (e.g., Cannon et al., 2003a; Cannon et al., 2008; Ruddy et al., 2010). 1 Mitigation for debris flows typically relies on systems to intercept debris, such as basins, walls, fences, and check dams; systems to guide debris past vulnerable structures, such as berms, le
38、vees and temporary barriers; and systems to reduce likelihood or volume of flows, such as mulching, revegetation after wildfire, and erosion barriers. Successful design and implementation of these systems depends on accurate estimates of a variety of debris-flow parameters, including volume, probabi
39、lity of occurrence, velocity, discharge rate, flow path direction and extent, triggering events, and fluid properties of the flow. Recent research has addressed many of these parameters, improving the accuracy of their prediction, raising awareness of typical pitfalls, and enhancing our understandin
40、g of the processes and our potential for influencing them. The goal of this paper is to review ten areas where recent research and field observations may be especially useful for mitigation of debris-flow hazards in Colorado. 1) THE GROWING, BURNING PROBLEM Debris flows are larger and more likely to
41、 occur following wildfire, and the problem is getting worse due to climate change. Following wildfire, there is more erosion and runoff because of loss of vegetation (reducing interception, infiltration, root strength and resistance to raindrop impact), temporary development of hydrophobic and ash l
42、ayers which further limit water infiltration, and heat fusing of soil into coarser and less cohesive aggregates that are more easily eroded (Martin and Moody, 2001; Shakesby and Doerr, 2006; Santi et al., in press). NASA estimates that there are over 6000 fires burning every day in July, August, and
43、 September (NASA, 2012). Climate change over the latter half of the last century has led to an increase in the number of wildfires and the length of the fire season (2.5 months longer in 2006 than in 1987) (Westerling et al. 2006). Despite the possible influence of fire suppression, exclusion and fu
44、el treatment, wildfire area burned is substantially controlled by climate (Littell et al. 2009). Grissino-Mayer et al. (2004) state that fire severity, frequency, and extent are expected to change drastically in coming decades in response to changing climate conditions. Climate change models show an
45、 increase in temperatures that will lead to more wildfires, but they also show a significant change in the precipitation patterns with more intense storms that can trigger post-wildfire debris flows. For example, in climate model results presented by Snyder and Sloan (2005), the trends predicted spe
46、cifically for California show that there will be large increases in intense precipitation. Heavy rainfall events have become more frequent over the past 50 years, even in locations where the mean precipitation has decreased or is unchanged (Chen and Knutson, 2008). Allen and Soden (2008) believe tha
47、t this amplification of rainfall extremes is bound to be larger than that predicted by models, implying that projections of future rainfall extremes in response to anthropogenic global warming may be underestimated. 2 GeoChallenges Debris flows in burned areas are larger than flows in the same areas
48、 before the burn or after recovery. For example, Figure 1 shows data from 276 sites in the Western U.S., compiled by Santi and Morandi (in review), where the median yield rate (volume of debris per unit area of drainage basin) for burned areas is over twice the rate for unburned areas. Debris flows
49、can be triggered by much lower rainfall amounts and intensity in burned areas than in unburned areas, as shown in Figure 2 (Cannon and DeGraff, 2009). 2) THE PLANTS COME BACK After wildfire, vegetation often recovers to pre-fire conditions in one to three years. For example, Figure 3 plots data showing vegetation represented as decreasing bare soil exposed for different burn severities (from Benavides-Solario and MacDonald, 2005). Assuming that typical Colorado mountain regions have a range of up to 20 to 30 percent bare soil, vegetative recover
