Research and instability of the ground. This

Research Proposal: Climate Change Impacts on Embankments in Permafrost RegionsName: Wang YikaiSupervisor: Prof. Charles W. W. NgAbstractFor the past few decades, earth temperature has been rising due to climate warming, leading to permafrost degradation and instability of the ground. This is problematic for all infrastructure built on permafrost, especially for roads and railways. Thaw settlement and soil consolidation promote embankment subsidence and the development of cracks, potholes, and depressions. In this proposal, literature related to key factors of permafrost under climate change are discussed. Based on the previous researches, future directions of study related to embankment behaviours are introduced as well.1. IntroductionPermafrost is defined as ground that remains below 0? Celsius for a period of two or more consecutive years. In high-latitude regions of Earth, temperatures have risen 0.6 °C per decade over the last 30 years, twice as fast as the global average. This is causing normally frozen the ground to thaw (Brown and Romanovsky, 2008). Specific geotechnical issues that necessitate input include slope stability, thaw settlement and frost heave, ditching, upheaval buckling. and others. The violate climate change could have a destructive effect on the existing embankments, contributing to the corruption of structures and degradation of serviceability. 2. Literature Review2.1 ConsolidationBased on Terzaghi’s consolidation theory and semi-empirical thawing boundary, Morgenstern and Nixon (1971) proposed a one-dimensional thaw consolidation theory. This theory was proved to have a low accuracy on displacement for restraint of small strain assumption when ice-rich permafrost was involved. With this theory, Qi et al. (2012) analysed the seasonal thaw settlement development of permafrost embankment. In these works, the displacement was often emphasized and used to verify the applicability of each theory. In these works, the displacement was often emphasized and used to verify the applicability of each theory.2.2 Water migration Measuring pour water pressure in permafrost is always challenging because of the complex freeze-thaw progress. Water migration, as well as volumetric change, contribute to this process. The cause of water migration is subdivided into direct migration which is powered by the hydraulic head and coupling migration due to temperature, concentration, and electric potential. For direct migration, the hydraulic head is hard to predict because the frozen soil beneath the melting region would block water from drainage and lead to an excess water pressure. The swell and shrinkage process would also complicate this issue. As for indirect migration, water is mainly driven by temperature potential. However, due to the lack of understanding in microscope study, pressure and water-ice-soil interaction are not well modeled. The Clausius-Clapeyron Equation (which describe the relationship between vapor pressure and temperature) cannot describe this process because it assumes a constant temperature and pressure.3. Key ObjectivesThe primary objective of my study is to predict the climate change effect on the embankments. This would be accomplished by investigating the novel drainage design, embankment foundation design, cooling system design, and performance study to develop adaption plans incorporating climate change.4. Research Methods4.1 Centrifuge testFor centrifuge modeling, Ketcham (1991) has given a broad overview of the centrifuge modeling technique applied to soil freezing and thawing. It has been used in application to practical engineering problems. Yang then explores the correctness of Miller’s postulated centrifuge modeling laws, by collecting experimental data on the development of frost heave in soil with no surface surcharge (Yang. D, 1998). In their studies, the temperature-controlled chamber can be realized by two systems——thermal insulation system which is achieved by latex membrane and temperature control system which adjust the boundary system at bottom and surface layer by vortex streams.4.2 Numerical ModellingNumerical models are flexible enough to accommodate highly variable materials, geometries and boundary conditions. Most thermal models for geoscience applications are implemented by simulating vertical ground temperature profiles in one dimension employing a finite difference or finite-element. Based on Shoop and Bigl’s (1997) study, couples of numerical modelling methods are developed. The FROST numerical model is a popular one which combines heat flow and moisture flow model. 5.  Proposed TimescaleThis timetable mainly focusses on the preparation of my MPhil study which is from now to next September.Time Dec-Jan Supra-permafrost pore water pressure and its effect on structuresJan-Apr Hydrothermal effects and the creep of permafrost Apr-May Centrifuge and numerical modelling in permafrost embankments May-Sep Preliminary test plan, if possible, finish the numerical model before entry6.    Reference1 Brown, J. & Romanovsky, V. E.(2008). Report from the International Permafrost Association: state of permafrost in the first decade of the 21st century. Permafr. Periglac. Process. 19, 255–260 2 Carlslaw HS, Jaeger JC. 1959. Conduction ofheat in solids. Oxford University Press:Oxford.3 Clausius, R. (1850).  On the motive power of heat and the laws which can be deduced therefrom regarding the theory of heat. Annalen der Physik (in German). 155: 500–524. 4 Deming D, Chapman DS. (1989). Thermal histo-ries and hydrocarbon generation: Example from Utah-Wyoming thrust belt. American Association of Petroleum Geologists Bulletin73(12): 1455–1471.5 Ketcham, S., Black, P., & Pretto, R. (1997). Frost Heave Loading of Constrained Footing by Centrifuge Modeling. Journal of Geotechnical and Geoenvironmental Engineering, 123(9), 874-880.6 Morgenstern, N.R., Nixon, J.F. (1971). One dimensional consolidation of thawing soils. J. Can. Geotech. 8(4), 558– 565 7 Qi, J.L., Yao, X.L., Yu, F., Liu, Y.Z. (2012). Study on thaw consolidation of permafrost under roadway embankment. Cold Reg. Sci. Technol. 81, 48–54.8 Shoop. S. A, and Bigl, S. R. (1997). “Moisture migration during freeze and thaw of unsaturated soils: Modeling and large scale experiments” Cold Regions Sci. and Technol., 25(1), 33-459 Yang, D., & Goodings, D. (1998). Climatic Soil Freezing Modeled in Centrifuge. Journal of Geotechnical and Geoenvironmental Engineering,124(12), 1186-1194


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