The Impact of Freezing-thawing Process on Slope Stability of Earth Structure in Cold Climate

Procedia Engineering, Volume 143, 2016, Pages 682-688

Alexey A. Korshunov, Sergey P. Doroshenko, Alexander L. Nevzorov

Abstract:The paper deals with assessment of impact of freezing-thawing process on slope stability. Numerical simulation with using coupled thermal–hydraulic–mechanical analysis (software “Geostudio 2012”, Canada) was implemented to make accurate time-dependent forecast of safety factor and defined probable slope failure mechanism of earth structures in cold climate. Results of modelling showed safety factor value was decreased from 2.15 to 1.13 when earth structure's slope is thawing. Significant increase of hydraulic gradient (from 0.1 to 14) was observed in the toe of dam.

Effects of the freeze–thaw (F–T) cycle on the andesitic rocks (Sille-Konya/Turkey) used in construction building

Journal of African Earth Sciences, Volume 109, September 2015, Pages 96-106

Mustafa Fener, İsmail İnce

Abstract:Stones used in the construction of cultural and historical buildings are exposed to various direct or indirect atmospheric effects depending on climatic and seasonal conditions. Stones deteriorate partially or fully as a result of this exposure. Therefore, the historicity of these buildings cannot withstand long. The freeze–thaw (F–T) process is one of the prominent conditions of this kind. Water penetration into the building stone via capillarity promotes weathering. When the temperature falls below 0 °C, the water freezes in the pores and tiny cracks of the building stones, causing volume expansion and exerting pressure on the stones. This cycle occurs most in areas where the temperature fluctuates above and below freezing often and causes and induces undesired weathering within the building stones. The Konya city, having been an old settlement province from 9000 B.C., encompasses quite valuable ancient buildings. Andesitic rocks, which are called Sille Stone in the region, were used in most of these buildings.

In this study, fresh andesitic rocks obtained from the stone quarry were tested in five F–T cycles in the laboratory. Textural changes that occurred in the deteriorated stones were examined by a polarizing microscope. Changes in porosity (n), uniaxial compressive strength (σu), point load strength (IS(50)), Brazilian tensile strength (σt), Böhme abrasion loss (BA), and ultrasonic velocity were statistically evaluated, and the effects of the number of F–T cycles on basic physical and mechanical properties of the stone were determined. In addition, weathering effects in the historical buildings constructed from the Sille andesite were investigated.

Freezing and thawing of montmorillonite — A time-resolved synchrotron X-ray diffraction study

Applied Clay Science, Volume 49, Issue 3, July 2010, Pages 127-134

Per Daniel Svensson, Staffan Hansen

Abstract:The evolution of phases over time during freezing and thawing of unconfined Na- and Ca-montmorillonites (Wyoming, MX-80) was studied with time-resolved synchrotron X-ray diffraction. The clay samples were: (i) powder equilibrated to ambient atmosphere and (ii) pastes of 30 mass% montmorillonite in pure water. The phases were characterised in-situ using a stream of nitrogen gas for temperature control.

The behaviour of montmorillonite during freezing and thawing is important in final repositories for spent nuclear fuel that are using bentonite as a buffer material.

The Na-montmorillonite equilibrated to ambient atmosphere (one-layer hydrate) was unaffected by freezing down to − 50 °C. The Ca-montmorillonite equilibrated to ambient atmosphere (two-layer hydrate) showed a minor decrease in basal spacing (0.11 Å) by freezing down to − 50 °C. The magnitude of the decrease in basal spacing was high compared to the thermal contraction of the similar minerals muscovite and pyrophyllite and some dehydration of the clay was likely to be involved. Wet Na-montmorillonite in pure water was highly affected by freezing causing the osmotic phase to collapse during ice formation to 19 Å (three-layer hydrate) and later to a mixture of two and three-layer hydrates (− 15 °C) and at lower temperatures to two-layer hydrate (16 Å, − 50 °C).

The Ca-montmorillonite in pure water was present as a 19 Å three-layer hydrate at + 20 °C and expanded upon cooling, producing two partly overlapping 001 reflections corresponding to three and four-layer hydrates prior to the ice formation. A mean d-value of the 002 peaks of the four-layer hydrate was determined to be 10.8 Å, which corresponded to a basal spacing of 21.6 Å. To our knowledge this is the first time a distinct four-layer-water hydrate is reported for Ca-montmorillonite in pure water. After the ice formation started, the montmorillonite was dehydrated to three-layer hydrate and at − 15 °C to a mixture of two and three-layer hydrates. At − 50 °C only two-layer hydrate was present.

The ice formation and the dehydration of the montmorillonite occurred simultaneously. The effects of freezing on the montmorillonite were shown to be reversible during the thawing.

The two dimensional diffraction rings gave information on the ice texture. The highly dispersed Na-montmorillonite (high surface area) in pure water facilitated the nucleation of the ice crystals and gave rise to uniformly sized crystals, while the Ca-montmorillonite (not dispersed, lower surface area) gave rise to non-uniformly sized ice crystals.

Assessment of strength development and freeze–thaw performance of cement treated clays at different water contents

Cold Regions Science and Technology, Volume 111, March 2015, Pages 50-59

Tuğba Eskişar, Selim Altun, İrem Kalıpcılar

Abstract:This paper examines the strength characteristics of Portland cement-treated fat and lean clays (CH and CL) under the conditions of freeze–thaw cycles. Specimens of natural clays were mixed with Portland cement in different percentages of 5% and 10%, in terms of the dry mass of soil using two different water contents of 30% and 50% for CH type of clay soil and 20% and 30% for CL type of clay soil to represent different consistencies and workability of soils. Besides, a group of cement free specimens was prepared and/or a group of specimens was not subjected to freeze–thaw cycles for comparison reasons. All specimens were cured for 7 and 28 days in a humidity controlled room at a constant temperature. After curing, specimens were subjected to a maximum of five cycles of closed-system freezing and thawing. Unconfined compression tests and ultrasonic pulse velocity tests were conducted on the specimens. The results of unconfined compression tests were evaluated in terms of water–cement ratio, curing period and the number of freeze–thaw cycles. Consequently, the compressive strength increased with the cement content increment of the clay specimens. While the specimens with highest cement content showed brittle behavior before freeze–thaw tests, they manifested less brittle behavior after freeze–thaw tests. The highest strength values were obtained in the specimens with low water contents. The compressive strength decreased as the freeze–thaw cycles increased, but cement treatment partially prevented the strength loss in freeze–thaw conditions. Generalized equations of strength development were assessed considering the total water–cement ratio and curing time effects for fat and lean clays that were subjected to 0, 1, and 5 cycles of freeze–thaw tests. In this way, this study showed that clay water–cement ratio hypothesis can be used to analyze the strength development of clays at different freeze–thaw cycles. It was observed that a linear correlation existed between the ultrasonic pulse velocity and the unconfined compression strength values. Furthermore, the plasticity index of the specimens subjected to 5 freeze–thaw cycles showed a decrement for the clay which was highly plastic in its native condition. Finally, with this study it is proven that cement treatment techniques can be preferred to enhance the freeze–thaw durability of fat and lean clay soils.

Influence of freeze–thaw dynamics on internal geochemical evolution of low sulfide waste rock

Applied Geochemistry, Volume 61, October 2015, Pages 160-174

Sean A. Sinclair, Nam Pham, Richard T. Amos, David C. Sego, Leslie Smith, David W. Blowes

Abstract:Continuous monitoring of a 15 m high heavily instrumented experimental waste rock pile (0.053 wt.% S) since 2006 at the Diavik diamond mine in northern Canada provided a unique opportunity to study the evolution of fresh run-of-mine waste rock as it evolved over annual freeze–thaw cycles. Samples were collected from soil water solution samplers to measure pore water properties, from twelve 4 to 16 m2 basal collection lysimeters to measure basal leachate properties in the region underlying the crest of the pile (the core), and from basal drains to measure aggregate total pile leachate properties. By 2012, monitoring of pore water geochemistry within the core structure of the test pile revealed an apparent steady state with respect to weathering geochemistry, represented by (i) a flush of pre-existing blasting residuals and applied tracers, (ii) declining pH, (iii) a stepwise progression and subsequent equilibrium with acid-neutralizing phases (depletion of available carbonates; equilibrium with respect to aluminum hydroxide phases and subsequent iron (III) hydroxide phases), and (iv) concordant release of SO4, major cations (Ca, Mg, K, Na, Si), and trace metals (Al, Fe, Ni, Co, Cu, Zn). Distinct, high concentration ‘spring flushes’, characteristic of drainage in northern environments and primarily explained by a combination of fluid residence time and the build-up of oxidation products over the winter, were released from core drainage each season. Following the initial flush, the concentration of all dissolved constituents steadily declined, with distinct minimums prior to freeze-up. The opposite trend was observed in the cumulative pile drainage, in which early season leachate dominated by snowmelt and batter flow had low concentrations and late season leachate dominated by contributions from the core of the pile (indicated by season end merging of core and cumulative drainage geochemistry) had higher concentrations. Northern waste rock pile drainage geochemistry is strongly influenced by freeze–thaw cycling and varying core and batter subsystem contributions to total drainage. A comprehensive understanding of thermal cycling in waste rock piles is an important component of temporal predictions of drainage water composition based on up-scaling or reactive transport modeling.

Soil bacterial growth after a freezing/thawing event

Soil Biology and Biochemistry, Volume 100, September 2016, Pages 229-232

Hannu T. Koponen, Erland Bååth

Abstract:Bacterial growth after freezing/thawing was studied in two soils with a history of annual freezing/thawing events. Soil samples were frozen for 1 week at −3 °C or −18 °C, thawed at +4 °C, and respiration and bacterial growth (estimated using leucine incorporation) were compared with reference soils kept at +4 °C. There were no major differences between soils. A respiration pulse, peaking within 9 h, was found, but after 30–100 h respiration had decreased to that in the reference. Freezing at −18 °C resulted in 2.2–2.5 times higher cumulative respiration than the reference, while at −3 °C 1.6–1.8 times higher respiration was found. Bacterial growth rates immediately after thawing were 43–44% of the reference in the −3 °C and 23–26% in the −18 °C treatment. Growth rates then increased linearly, recovering after 36 h and around 50 h in the −3 °C and −18 °C freezing, respectively. Growth rates then increased further in the −18 °C, but remained lower or similar to the reference in the −3 °C treatment. The microbial response to freezing/thawing thus appeared similar to mild drying/rewetting (type 1 response sensu Meisner et al. (2015)).