Creep Behavior of Shallow Anchors in Ice-rich Silt

Zhang, Xiong; Chen, Liangbiao; Lin, Chuang; McHattie, Robert

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Abstract

Grouted anchors have become a common technique in the application of earth retention systems, slope stability problems and tie-down structures in unfrozen soils due to its cost and time efficiency. However, within much of Alaska area, permafrost is a common type of soil and might contain large amount of visible ice. The highly time and temperature dependent properties of ice-rich soil make it a challenge for the application of anchors in permafrost area. This project valuates the effect of water content and temperature on the creep behavior of shallow anchors in cold room lab. Also, field test was conducted to determine effectiveness of three types of grouting materials, including Bentonite clay, Microsil Anchor Grout and special cement formula. The temperature along the anchor was monitored to evaluate the degradation of the surrounding frozen soil. Research results may be applicable in the design of shallow anchors in ice-rich permafrost at various ice content and temperature range. Also, the load distribution and the pullout test results could give a general guidance for the shallow anchor design in permafrost area.

Table of Contents - iv List of Figures - viii List of Tables - xiv Chapter 1 Introduction - 1 1.1 General - 1 1.2 Problem Statement - 1 1.3 Objective - 2 1.4 Research Methodology - 2 Chapter 2 Literature Review - 4 2.1 Background on Grouted Anchors - 4 2.2 Creep Theory - 5 1. General Creep Behavior - 5 2. Creep Behavior of Ice - 6 3. Creep behavior of Frozen Soils - 8 2.3 Grouted Anchor Design in Permafrost - 10 1. Grouted Anchor Design Considerations - 11 2. Grouted Anchor Design in Ice-rich Soil - 14 Chapter 3 Laboratory Test - 19 3.1 Laboratory Pullout Test Preparation - 19 1. Soil Preparation - 19 2. Grouted Anchor Preparation - 20 3. Load Frame Preparation - 23 4. Calibration of the Testing Equipment - 26 3.2 Laboratory Pullout Test Procedures - 28 1. Preparing Anchor Test Specimens - 28 2. Load Frame Setup - 31 3. Testing Procedure Outline - 32 Chapter 4 Field Tests of Anchor in CRREL Permafrost Tunnel - 34 4.1 Test Site Overview - 34 1. Introduction to Testing Site - 34 2. CRREL Permafrost Tunnel Geology - 36 3. Anchor Test Location within Permafrost Tunnel - 37 4.2 Testing Equipment - 39 1. Strain Sensors - 40 2. LVDT - 42 4.3 Borehole Drilling Process - 43 1. Drilling Borehole and Drilling System Layout - 43 2. Drilling machine setup - 46 3. Drilling procedure - 48 4. Drilling sequence - 50 4.4 Anchor Preparation and Installation - 51 1. HPI Strain Gage Installation - 52 2. Geokon Strain Gage Installation - 55 3. Anchor Installation Process - 57 4. Backfill Material Preparation and Grouting - 58 5. Backfill Material Mixing - 59 4.5 Loading System Setup - 62 1. Loading system for shallow anchor - 62 2. Loading system for duckbill - 68 4.6 Data Acquisition System Setup - 69 4.7 Duckbill Removal and Anchor Pullout Test - 71 1. Duckbill Removal - 71 2. Pullout Test System Setup - 72 Chapter 5 Test Results and Data Analysis - 75 5.1 Laboratory Pullout Test Results and Analysis (UAF Laboratory) 75 1. Effect of Temperature and Water Content - 77 2. Design Chats for Creep Rate at Different Temperature and Water Content - 78 5.2 Grouting Temperature Test Results and Analysis (Permafrost Tunnel) - 79 5.3 Duckbill Test Results and Analysis (Permafrost Tunnel) - 85 5.4 Load Distribution along Anchor Shaft for Bar-Type Anchors (Permafrost Tunnel) - 88 5.5 Displacement vs. Time Curves (Permafrost Tunnel) - 98 5.6 Pullout Test Results and Analysis - 103 Chapter 6 Conclusion and Recommendation - 111 6.1 Conclusions - 111 6.2 Recommendations - 112 References - 113 Appendix A Displacement vs. Time Curves - 116 Appendix B Grouting Temperature - 123 Appendix C Load Distribution - 126 Appendix D Displacement vs. Time Curve Revision - 134 Appendix E Pullout Test Results - 140

Date

2013-07

Type

Technical Report

Collections

INE Project Reports