1、GEOTECHNICAL PRACTICE PUBLICATION NO. 9 ROCKY MOUNTAIN GEO-CONFERENCE 2014 PROCEEDINGS OF THE 2014 ROCKY MOUNTAIN GEO-CONFERENCE November 7, 2014 Lakewood, Colorado SPONSORED BY The Geo-Institute of the American Society of Civil Engineers Geo-Institute Chapter of the Colorado Section of the American
2、 Society of Civil Engineers Rocky Mountain Section of the Association of Environmental and Engineering Geologists Colorado Association of Geotechnical Engineers EDITED BY Jere A. Strickland, P.E. Richard L. Wiltshire, P.E. Christoph M. Goss, Ph.D., P.E. Published by the American Society of Civil Eng
3、ineers Library of Congress Cataloging-in-Publication Data 2014 Rocky Mountain Geo-Conference (2014 : Lakewood, Colo.) Rocky Mountain Geo-Conference 2014 : proceedings of the 2014 Rocky Mountain Geo-Conference, November 7, 2014, Lakewood, Colorado / sponsored by the Geo-Institute of the American Soci
4、ety of Civil Engineers and 3 others ; edited by Jere A. Strickland, P.E., Richard L. Wiltshire, P.E., Christoph M. Goss, Ph.D., P.E. pages cm. - (Geotechnical practice publication ; no. 9) ISBN 978-0-7844-1380-7 (paper : alk. paper) 1. Engineering geology-Colorado-Congresses. I. Strickland, Jere, ed
5、itor. II. Wiltshire, Richard L., editor. III. Goss, Christoph M., editor. IV. American Society of Civil Engineers. Geo-Institute, sponsoring body. V. Title. TA705.3.C6B534 2014 624.15109788-dc23 2014033267 Published by American Society of Civil Engineers 1801 Alexander Bell Drive Reston, Virginia, 2
6、0191-4382 www.asce.org/bookstore | ascelibrary.org Any statements expressed in these materials are those of the 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 me
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12、844-1380-7 (paper) Manufactured in the United States of America. Front and Back Cover Photo Credit: Bill McCormick iii Preface As geo-professionals, we are called to provide solutions for the many challenges that our earth presents in the areas we choose to work, play and live. From natures geologic
13、al 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 the use of new technologies, modeling methods and visual mapping, geo-professionals have answered these many challe
14、nges 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 anomalies, alternative energy resources and infrastructure. This will highlight, again, how the geo-professional communi
15、ty provides solutions to the most challenging applications. Since 1984, the Geotechnical Institute Chapter of Colorado (formally known as the ASCE Colorado Sections Geotechnical Group) in collaboration with the Rocky Mountain Section of the Association of Environmental and Engineering Geologists and
16、 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/geotechnical engineers, geologists, and other geo- professionals. The geotechnical seminars have been held at area
17、 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 papers of these seminars in Geotechnical Practice Publications, allowing the experiences to be shared with a worldwide
18、 audience. The Geo-Influence Steering Committee convened in August 2013 and held monthly meetings to plan for the 2014 Rocky Mountain Geo-Conference. The Steering Committee members included Christoph Goss (Conference Chair), Sam Adettiwar, Dustin Bennetts, Mark Brooks, Laura Campbell, Robin Dornfest
19、, Darin Duran, Julia Frazier, Evan Friedman, Joseph Kerrigan, Joels Malama, Bill McCarron, Minal Parekh, Becky Roland, Jere Strickland, Lindsay Tita, Mark Vessely, Chris Wienecke, Richard Wiltshire, and John Worthen. Jere Strickland, Richard Wiltshire, and Christoph Goss iv Acknowledgments The GeoCh
20、allenges 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. 9. The authors have spent many hours in preparing and finalizing their papers, which will be presented at the 2014
21、Rocky Mountain Geo-Conference on November 7, 2014. 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 on Technical Publications completed its review of our papers
22、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 Publications Division for putting this publication together. Contents Flood Repair: The Influence of Water Dam Perform
23、ance along Left Hand Creek during the Front Range Flood of 2013 1 Richard J. Tocher P.E. and L. Clint Brown P.E. GIS Modeling to Assess Economic Risk from Post-Fire Debris-Flows . 9 Kevin McCoy, Paul Santi P.G., Daniel Kaffine, and Vitaliy Krasko Dams and Levees: Influential Infrastructure Rio Grand
24、e Dam Seepage Reduction Design and Construction 31 Derek H. Foster P.E., Dan Bole, and Ted W. Deere City of Dallas Floodway System (DFS) Case Study: 100-Year Levee Remediation . 59 Brad Barth P.E., Stephen W. Ringen E.I.T., and Jeffrey H. Sallas Design and Construction of an Earthen Impoundment for
25、Water Management 69 Thomas Chapel P.G., P.E., Jon Jaffe, and Caleb Stock P.E. Classic Geotech: Influencing the State of the Art Dealing with Tricky Soils at the SDS Water Treatment Plant . 82 Steven Kuehr P.E., Rebecca Brock P.E., and Alexander Vega E.I.T. Needles Eye Tunnel Repair Feasibility Study
26、 98 Christoph Goss P.E. and Don W. Deere P.E. Ground Classification for Trench, Shaft, and Slope Excavations 111 Sarah Myers E.I.T., Bill Zietlow P.E., Robin Dornfest P.G., and Rebecca Brock P.E., P.G. Hazards: Reducing Influence A Landslide Hazard Rating System for Colorado Highways 120 Dan Pratt a
27、nd Paul Santi P.G. An Innovative Case Study on the Use of Launched Nails for Landslide Repair . 139 Matt Birchmier P.E. and Cameron Lobato P.E. Full-Scale Testing of Rockfall Barrier and Post Foundation Systems 148 Ben Arndt P.E., P.G., Ty Ortiz P.E., and Bob Group vAuthor List Arndt, Ben, 148 Barth
28、, Brad, 59 Birchmier, Matt, 139 Bole, Dan, 31 Brock, Rebecca, 82 Brock, Rebecca, 111 Brown, L. Clint, 1 Chapel, Thomas, 69 Deere, Don W., 98 Deere, Ted W., 31 Dornfest, Robin, 111 Foster, Derek H., 31 Goss, Christoph, 98 Group, Bob, 148 Jaffe, Jon, 69 Kaffine, Daniel, 9 Krasko, Vitaliy, 9 Kuehr, Ste
29、ven, 82 Lobato, Cameron, 139 McCoy, Kevin, 9 Myers, Sarah, 111 Ortiz, Ty, 148 Pratt, Dan, 120 Ringen, Stephen W., 59 Sallas, Jeffrey H., 59 Santi, Paul, 9, 120 Stock, Caleb, 69 Tocher, Richard J., 1 Vega, Alexander, 82 Zietlow, Bill, 111 viDam Performance along Left Hand Creek during the Front Range
30、 Flood of 2013 Richard J. Tocher 1 , P.E, M. ASCE and L. Clint Brown 2 , P.E. 1 Principal, Engineering Analytics, Inc. 1860 Blake Street, Ste 200, Denver, CO 80202 2 Project Manager, Engineering Analytics, Inc., 1600 Specht Point Road, Ste 209, Fort Collins, CO 80525 ABSTRACT: Severe flooding on t
31、he Front Range of Colorado in September 2013 tested many dams including several dams on and adjacent to the Left Hand Creek drainage north of Boulder, Colorado. A tropical-like storm drove moisture up against the foothills dropping 200 mm (8 in) to more than 350 mm (14 in) of precipitation in a 24-h
32、our period based on a number of weather stations within the watershed. The precipitation resulted in flash flooding in Left Hand Creek. A dam west of the main precipitation event experienced no damage. A diversion dam near the mouth of Left Hand Canyon was completely destroyed by the storm event due
33、 to scour. An off- channel valley reservoir dam experienced damage to both the service and emergency spillways. The experiences along Left Hand Creek demonstrate the need for geotechnical and structural design of dams for extreme events especially in mountain environments where uncertain flood event
34、s can occur due to unusual weather patterns. INTRODUCTION Left Hand Creek is 55 km (34 miles) long from its headwaters on Niwot Ridge at an elevation of over 3660 m (12,000 ft) to its confluence with St. Vrain Creek as shown on Fig. 1. The creek descends from the mountains in a steep canyon, known a
35、s Left Hand Canyon. It emerges from the foothills north of Boulder, Colorado and crosses the Colorado Piedmont, passing north of Niwot and joining St. Vrain Creek on the south side of Longmont. The basin covers 186 km 2(72 sq miles) and discharges into the St. Vrain Creek in Longmont at an elevation
36、 of 1500 m (4924 ft). GEOLOGIC SETTING Pre-Cambrian metamorphic and granitic rocks dominate the geology of the mountainous portions of the watershed, including intrusive stocks and dikes. Glacial deposits occur near the upper watershed alongside and west of Highway 72. These are 1mostly glacial mora
37、ine material rather than glacial outwash, and can reach up to 15 m (50 ft) thick in some locations. The crystalline rocks within the watershed contain FIG. 1. Left Hand Creek Watershed several minerals in extractable quantities, including gold, fluorite, lead, silver, uranium, tungsten, and copper.
38、These minerals were deposited with intrusions of molten igneous rocks during periods of mountain uplift. Soils in the watershed are fairly thin. The Left Hand Creek watershed covers portions of two distinct physiographic regions: the Southern Rocky Mountain province and the Colorado Piedmont section
39、 of the Great Plains province. Foothills separate these distinct topographical features. Glaciation, stream erosion and deposition, wind erosion, and atmospheric weathering formed and continue to alter the watershed topography. The watershed features gentle slopes concentrated near the upper reaches
40、 of the watershed and steep canyon reaches near the watershed mouth. Although some glacial deposits are present near the upper watershed, the canyons in the middle and lower portions of the watershed have a V- shaped morphology, formed by water flow rather than glacial ice. SEPTEMBER 2013 FLOOD EVEN
41、T The Front Range of Colorado experienced an unusually moist and persistent weather pattern from September 9 through 15, 2013. The storm dropped all time record precipitation in the area north of Boulder, Colorado with some areas receiving over 400 mm (16 in) of rain. The event was caused by a near
42、stationary low pressure system over eastern Nevada that pulled tropical moisture from the Pacific Ocean and the Gulf of Mexico. An upslope condition developed along the foothills creating the large rainfall. Most of the rainfall occurred over 36 hours between September 11 and 13. The event was simil
43、ar to a storm in 1938 that also occurred in September. The peak rainfall intensities were lower than previous storms but the intensity of the storm was about 5 mm (0.2 in) per hour from September 11 through 13 with a peak 2 ROCKY MOUNTAIN GEO-CONFERENCE 2014intensity of 28 mm (1.1 in) per hour. Ther
44、e were sufficient rain gages in the watershed (NOAA, 2013) to construct total event precipitation contours as shown in Fig. 2. About 40 percent of the basin received over 355 mm (14 in) of precipitation from the event. FIG. 2. Total Basin Precipitation Once the floodwaters receded, Left Hand Ditch C
45、ompany engineers found that Left Hand Creek had to be re-channeled to its original course over 1.6 km (1 mile) in an area of critical diversion structures and head gates. Some sections of the companys systems were completely destroyed. When applying for emergency loans from the Colorado Water Conser
46、vation Board, the company estimated the cost to repair the damage would be $3.2 million. Without critical repairs to the companys infrastructure, a significant portion of irrigated farm land in Boulder County and the companys five reservoirs would have been unusable for the following irrigation seas
47、on. One of those reservoirs provides water for residential use in the Left Hand Water District. The U.S. Geological Survey (1988) study of peak flows in the creeks surrounding Left Hand Creek generated a series of empirical correlations for flood levels based on elevation and drainage basin area bel
48、ow an elevation of 2440 m (8000 ft). These correlations were used to calculate exceedance probabilities for Left Hand Creek at the Allens Lake diversion dam, North 55th Street, and the confluence with the St. Vrain Creek as shown in Fig. 3. The results show a 100-year recurrence flow of 120 m 3 /s (
49、4300 cfs) at the diversion structure. This estimated flow was not able to be verified by field measurements during the flood event. Damage along Left Hand Creek and its tributary James Creek was massive. Photographs 1 and 2 show the degree and damage sustained. ROCKY MOUNTAIN GEO-CONFERENCE 2014 3 FIG. 3. Flood Recurrence along Left Hand Creek LEFT HAND CREEK DAMS There are five dams and reservoirs in and adjacent to the watershed that are owned and operated by Left Hand Ditch Company Lake Isabelle, Gold Lake, Allens
