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Case Histories of Liquefaction Failures

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Case Histories of Liquefaction Failures MISCELLANEOUS PAPER S-76-4 CASE HISTORIES OF LIQUEFACTION FAILURES by Paul A. Gilbert Soils and Pavements Laboratory U. S. Army Engineer Waterways Experiment Station P. O. Box 631, Vicksburg, Miss. 39180 April 1976 Final Report Approved For Public Release; Distribution Unlimited . ± ¿ L Z « Prepared for Office, Chief of Engineers, U. S. Army TA Washington, D. C. 2 0 3 14 7 .W34m Under Project No. 4AI6II02B52E, S-76-4 Task 04 1976 LIBRARY um 2 5 1981 Waters Por-- P o l i r e - ■■ Iteiiv^r, UGìOfiiuò Destroy this report when no it to the BUREAU OF RECLAMATION DENVER LIBRARY 92044012 SECURITY CLASSIFICATION OF THIS PAGE (When Data Entered) READ INSTRUCTIONS REPORT DOCUMENTATION PAGE BEFORE COMPLETING FORM 1. REPORT NUMBER 2. GOVT ACCESSION NO. 3. RECIPIENT'S CATALOG NUMBER Miscellaneous Paper S-76-4 4. T IT L E (and Subtitle) 5. TYPE OF REPORT & PERIOD COVERED Final report CASE HISTORIES OF LIQUEFACTION FAILURES 6. PERFORMING ORG. REPORT NUMBER 7. AUTHOR!» 8. CONTRACT OR GRANT NUMBER*» Paul A. Gilbert 9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT, PROJECT, TASK AREA & WORK UNIT NUMBERS U. S. Army Engineer Waterways Experiment Station Soils and Pavements Laboratory Project 4A161102B52E, P. O. Box 631, Vicksburg, Miss. 39180 Task 04 11. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE April 1976 Office, Chief of Engineers, U. S. Army Washington, D. C. 20314 13. NUMBER OF PAGES 24 14. MONITORING AGENCY NAME & ADDRESS!’// different from Controlling Office) 15. S E C U R IT Y CLASS, (of thia report) Unclassified 15«. declassification / downgrading SCHEDULE 16. DISTRIBUTION STATEMENT (of thia Report) Approved for public release; distribution unlimited. 17. DISTRIBUTION STATEMENT (of the abatract entered in Block 20, if different from Report) 18. SUPPLEMENTARY NOTES 19. KEY WORDS (Continue on reverae aide if neceaaary and identify by block number) Liquefaction (Soils) Noncohesive soils 20k. ABSTRACT (Cbnttaum an reverae aid* ft neceeeary and identify by block number) Liquefaction of loose, saturated, cohesionless soils is a phenomenon in which the soil mass suddenly loses shear strength, behaves as a fluid, and acquires a degree of mobility sufficient to permit large movements. This report reviews various case histories to determine common characteristics associated with liquefaction failures. A review of case histories reveals that liquefaction failures are dependent upon (a) a collapsible soil structure, (b) a saturated and undrained condition, and (c) a triggering mechanism. Typically collapsible soils which liquefied were fine, uniform, loose sand deposits with D 10 sizes ranging from 0.05 to 1.0 mm and a coefficient of uniformity ranging from 2 to 10. Saturated-undrained conditions provided a situation conducive to high pore pressure development upon collapse of the soil structure. Generally, water was the pore fluid; however, several (Continued) DO I JAN 73 1473 ed itio n OF I NOV ss is o b so l e t e Unclassified SECURITY CLASSIFICATION OF THIS PAGE (Witen Data Entered) ________________Unclassified_________________ SECURITY CLASSIFICATION OF THIS PAGEQWin Data Entered) 20. ABSTRACT (Continued). unusual cases were reported with air as the pore fluid (termed fluidization). A variety of triggering mechanisms, including monotonically changing stresses, earthquakes, explosive blasts, and cyclic vibrations, were found to cause liquefaction failures. However, monotonically increasing shear stresses and earthquakes are the most common triggering mechanisms. Density is the most important property controlling the susceptibility of saturated-undrained sands to liquefaction. It was found that sands which liquefy when subjected to earthquake shakings do not become significantly more stable against reliquefaction. Conversely, vibrations appear to alter the sand structure, making a deposit less susceptible to liquefaction than indicated by density increases. Unclassified SECURITY CLASSIFICATION OF THIS PAGE(TWien Data Entered) PREFACE This study was funded by the Office, Chief of Engineers, U. S. Army, under Project No. 4A161102B52E, Task 04, “Research in Military Engineering and Construction.” The work was conducted during the period September 1974-May 1975 at the U. S. Army Engineer Waterways Experiment Station (WES) by Mr. Paul A. Gilbert under the direct supervision of Dr. Frank C. Townsend, Chief, Soils Research Facility. The study was under the general supervision of Mr. Clifford L. McAnear, Chief, Soil Mechanics Division, and Mr. James P. Sale, Chief, Soils and Pavements Laboratory. The technical monitor of this study at OCE was Mr. A. F. Muller. The Director of WES during this study was COL G. H. Hilt, CE, and the Technical Director was Mr. F. R. Brown. 1 CONTENTS Page PREFACE .......................................... 1 CONVERSION FACTORS, U. S. CUSTOMARY TO METRIC (SI) UNITS OF MEASUREMENT ..................................................................................................... 3 PAR TI: INTRODUCTION ........................................................................................................... 4 Background .................................................................................................................................. 4 Objective and Scope ..................................................................................................................... 4 PART II: NECESSARY CONDITIONS FOR LIQUEFACTION FAILURE ....................... 5 Loose Deposits, Fine Sand ............................................................ 5 Soil Saturation ............................................................................................................................. 7 Triggering Mechanisms ............................................................................................................... 8 PART III: CASE HISTORIES ....................................................................................................... 9 Liquefaction Induced by Monotonically Changing Stresses ................................................... 9 Liquefaction Induced by Cyclic Vibrations .............................................................................. 12 Flow Failures Induced by Earthquakes, Blasts, and Wave Action ......................................... 14 PART IV: DISCUSSION OF CASE HISTORIES .................................................................... 19 Soil Type and Triggering Mechanisms Causing Liquefaction ................................................. 19 Effects of Density on Liquefaction Potential ............................................................................ 19 Liquefaction Potential ................................................................................................................. 21 PART V: CONCLUSIONS ............................................................................................................. 22 REFERENCES .................................................................................................................................... 23 2 CONVERSION FACTORS, U. S. CUSTOMARY TO METRIC (SI) UNITS OF MEASUREMENT U. S. customary units of measurement used in this report can be converted to metric (SI) units as follows: Multiply By To Obtain feet 0.3048 metres miles (U. S. statute) 1.609344 kilometres acres 4046.856 square metres acre-feet 1233.482 cubic metres cubic yards 0.7645549 cubic metres tons (short, 2000 lb mass) 907.1847 kilograms pounds (force) 4.448222 newtons tons (force) 8.89644 kilonewtons miles per hour (U. S. statute) 1.609344 kilometres per hour tons (nuclear equivalent of TNT) 4200 megajoules degrees (angle) 0.01745329 radians 3 CASE HISTORIES OF LIQUEFACTION FAILURES PART I: INTRODUCTION BACKGROUND 1. By definition, liquefaction of cohesionless soils is a phenomenon in which a soil mass suddenly loses shear strength and behaves as a viscous fluid in that it undergoes large shear deformations without recovery of shear resistance. This loss of shear strength is due to a collapse of the soil structure which transfers load carried by the grain structure onto the pore water, thereby increasing the pore water pressure and decreasing the effective stress within the soil mass. Hence the process requires (a) a collapsible soil structure, (b) a nearly saturated and undrained condition, and (c) a triggering mechanism. A collapsible soil structure implies a low density and little or no cohesion to restrict movement of the soil grains. In this context, most liquefaction failures have been observed in sand deposits. A nearly saturated-undrained condition is implied since if air were present (i.e., partial saturation) or drainage were to occur, the induced pore pressures would quickly dissipate and the effective stress would increase, allowing the mass to recover strength. A variety of triggering mechanisms exist which cause shear strains leading to collapse of the soil structure; these may be monotonically changing shear stresses, cyclic vibratory loads, or random shock waves. OBJECTIVE AND SCOPE 2. The objective of the study was to determine the common conditions associated with liquefaction failures caused by the various triggering mechanisms. Published case histories are reviewed and evaluated to establish the common conditions. Each of these conditions is studied to determine its relative importance in the evaluation of liquefaction susceptibility. 4 PART II: NECESSARY CONDITIONS FOR LIQUEFACTION FAILURE 3. This part of the report discusses the field conditions necessary for a liquefaction
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