Creep of grouted anchors in ice-rich silt

Chen, Liangbiao

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Abstract

Creep is a critical consideration for designing anchors in ice-rich silt. In this study, creep was evaluated for grouted anchors in ice-rich silt by laboratory tests. A total of nineteen staged-load pullout tests were conducted on smooth grouted anchors. The anchors were loaded until either a tertiary creep stage or the capacity of the load system was reached. Soil temperatures evaluated in this study ranged from 32 °F to 26.6 °F. It was found that the onset of tertiary creep for smooth anchors was around 0.03 inches, which was much smaller than that suggested in the literature for rough anchors (1.0 inch). Given the same shear stress and soil temperature, the observed creep displacement rates for smooth anchors were greater than those given by the existing design guidelines for rough anchors. A new creep model was proposed in which soil temperature was included as an additional variable. Model parameters were developed as a function of soil temperature and moisture contents by using the test data. The model predictions were compared with the laboratory tests. It was found that the creep displacement rates decreased with the decreasing of soil moisture contents and temperature. Based on the analysis of laboratory test data, design charts were provided to give the allowable pullout capacity for smooth anchors in ice-rich silt.

Description

Thesis (M.S.) University of Alaska Fairbanks, 2011

1. Introduction -- 1.1. Objectives of the research -- 1.2. Research methodology -- 2. Literature review -- 2.1. Background on grouted anchors -- 2.2. Creep behavior of grouted anchors -- 2.3. Factors influencing creep of anchors in permafrost -- 2.4. Existing theories for creep in frozen soil -- 2.5. Design for anchor capacity -- 2.6. Anchor load tests in permafrost -- 3. Anchor load tests and test results -- 3.1. Soil preparation -- 3.2. Laboratory creep test setup -- 3.3. Anchor installation methods -- 3.4. Testing procedures -- 3.5. Test results -- 4. Data analysis and discussion -- 4.1. Comparison with rough anchors based on the design guidelines -- 4.2. Development of a time-dependent creep equations -- 4.3. Effect of soil moisture content and temperature -- 4.4. Design example -- 4.5. Design charts -- 5. Conclusions and recommendations -- 5.1. Conclusions -- 5.2. Recommendations -- References -- Appendix A: Anchor load tests in the laboratory -- A.1. Test anchor configurations and fabrications -- A.2. Load frame configurations and calibrations -- A.3. Displacement measurement -- A.4. Testing procedures -- Appendix B: Anchor load test results -- B.1. Load conditions -- B.2. Creep curves from the nineteen load tests -- Appendix C: Data regression results.

Date

2011-05

Type

Thesis

Collections

Engineering