Stress–Strain Assessments for Buried Oil Pipelines Under Freeze-Thaw Cyclic Conditions

2021 ◽  
Vol 143 (4) ◽  
Author(s):  
Zhen-Chao Teng ◽  
Xiao-Yan Liu ◽  
Yu Liu ◽  
Yu-Xiang Zhao ◽  
Kai-Qi Liu ◽  
...  
Keyword(s):  
Frozen Soil ◽  
Ratchet Effect ◽  
Frost Heaving ◽  
Soil Frost ◽  
Oil Pipeline ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Oil Pipelines ◽  
Freeze Thaw Cycle ◽  
Effect Theory

Abstract In this study, outdoor freeze-thaw cyclic tests on the Q345 steel pipeline portion were conducted to analyze the buried oil pipeline stress evolution in a seasonally frozen soil area, namely, the Mohe–Daqing portion of China–Russia crude oil pipeline. The results obtained show that under the freeze-thaw cycle, the variation trend of soil temperature around the pipeline exhibited a hysteresis pattern, which was similar to that of atmospheric temperatures. The soil frost heaving force was shown to drop with depth, and its value at the pipe top was higher than that at the pipe bottom. With the number of freeze-thaw cycles, the frost heaving force of the soil first increased and finally stabilized, while the principal stress of the pipeline increased gradually, and its extreme value tended to be stable after 7–8 cycles, which was consistent with the “ratchet effect” theory. The above findings made it possible to elaborate on a more efficient freeze-thaw cyclic test setup for clarifying the mechanism of frozen soil/pipeline interactions.

scholarly journals The Effects of Particle Gradation on Salinized Soil in Arid and Cold Regions

Water ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 236
Author(s):  
Xuebang Huang ◽  
Zizhao Zhang ◽  
Ruihua Hao ◽  
Zezhou Guo
Keyword(s):  
Particle Size ◽  
Soil Samples ◽  
Frost Heaving ◽  
Particle Content ◽  
Cold Regions ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Salinized Soil ◽  
Size Grading

Particle size grading impacts salt-frost heaving and dissolution collapse events of salinized soil on northwestern China’s arid and cold region highways. However, the influencing mechanisms remain unclear and the impact of varying particle size grading needs further investigation. Hence, this study focused on these effects and the number of freeze–thaw cycles on the characteristic changes in highway salinized soil in arid and cold regions. Three soil columns with different gradations were prepared to explore the gradation and the number of freeze–thaw cycle affects on salinized soil’s salt-frost heaving and dissolution collapse characteristics. The multi-functional physical simulation platform conducted multiple freeze–thaw cyclic tests in the laboratory. Test results confirmed significant and conclusive effects of gradation and the number of freeze–thaw cycles on salinized soil’s salt-frost heaving and dissolution collapse behaviors. Poorly graded salinized soil with high coarse particle content caused repeated freeze and thaw engineering hazards, significantly affecting salinized soil’s displacement and deformation behaviors during freezing. Contrarily, an increased range of fine particles more easily involved the characteristics of salinized soil during thawing. Therefore, the fourth freeze–thaw cycle was a crucial time node. After four freeze–thaw cycles, the displacement and deformation of original salinized soil and B-grade salinized soil samples (poorly graded with high fine particle content) tended to be stable. In contrast, the displacement and deformation of A-grade salinized soil samples (poorly graded with high coarse particle content) increased the growth rate. The present research results contribute to in-depth knowledge of the effects of gradation and freeze–thaw cycles on the characteristics of salinized soil in northwestern China, providing excellent referenced data support for the prevention and control of highway salinized soil failures and other engineering projects in arid and cold regions of northwest China.

scholarly journals A Freezing-Thawing Damage Characterization Method for Highway Subgrade in Seasonally Frozen Regions Based on Thermal-Hydraulic-Mechanical Coupling Model

Sensors ◽  
2021 ◽  
Vol 21 (18) ◽  
pp. 6251
Author(s):  
Qingsong Deng ◽  
Xiao Liu ◽  
Chao Zeng ◽  
Xianzhi He ◽  
Fengguang Chen ◽  
...  
Keyword(s):  
Rapid Development ◽  
Coupling Model ◽  
Frozen Soil ◽  
Mechanical Coupling ◽  
Damage Area ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Ice Content ◽  
Ice Water

Seasonally frozen soil where uneven freeze–thaw damage is a major cause of highway deterioration has attracted increased attention in China with the rapid development of infrastructure projects. Based on Darcy’s law of unsaturated soil seepage and heat conduction, the thermal–hydraulic–mechanical (THM) coupling model is established considering a variety of effects (i.e., ice–water phase transition, convective heat transfer, and ice blocking effect), and then the numerical solution of thermal–hydraulic fields of subgrade can be obtained. Then, a new concept, namely degree of freeze–thaw damage, is proposed by using the standard deviation of the ice content of subgrade during the annual freeze–thaw cycle. To analyze the freeze–thaw characteristics of highway subgrade, the model is applied in the monitored section of the Golmud to Nagqu portion of China National Highway G109. The results show that: (1) The hydrothermal field of subgrade has an obvious sunny–shady slopes effect, and its transverse distribution is not symmetrical; (2) the freeze–thaw damage area of subgrade obviously decreased under the insulation board measure; (3) under the combined anti-frost measures, the maximum frost heave amount of subgrade is significantly reduced. This study will provide references for the design of highway subgrades in seasonally frozen soil areas.

Study on Influence of Freeze-Thaw Cycles on the Physical-Mechanical Properties of Loess

2012 ◽  
Vol 442 ◽  
pp. 286-290
Author(s):  
Gui Quan Bi
Keyword(s):  
Mechanical Properties ◽  
Water Content ◽  
Water Distribution ◽  
Early Stage ◽  
Frozen Soil ◽  
Dry Density ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Filling Water

Loess foundations in seasonally frozen soil region are subject to severe effect of freeze-thaw cycles. This often results in water redistribution and structure weakening. So it is very important to study the physical-mechanical properties of loess under freeze-thaw cycles. In this paper, systematic study was carried out using freeze-thaw cycle machine. The impacts of freeze-thaw cycles on the physical-mechanical properties of loess including deformation, water distribution and dry density under the condition of filling water to loess samples were investigated. The results proved that the freeze-thaw cycles can increase the water content gradually from the bottom to the top in the loess samples under water supplied condition. The water content gradient reaches maximum at the freeze-thaw interface. The loess samples deform sharply at the early stage of the freeze-thaw cycles and then reach a stable status. The freeze-thaw cycles decrease the dry density of the loess samples gradually. The dry density at the top is lower than that at the bottom, due to more severe freeze-thaw effect at the top of the samples.

Modeling soil freeze-thaw and ice effect on canal bank

1998 ◽  
Vol 35 (4) ◽  
pp. 655-665 ◽  
Author(s):  
Z X Zhang ◽  
R L Kushwaha
Keyword(s):  
Frozen Soil ◽  
Soil Freezing ◽  
Frost Heave ◽  
Energy Status ◽  
Abrupt Increase ◽  
Water Ice ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Initial Soil ◽  
Freeze Thaw Cycle

The experiments for modeling soil freeze-thaw and ice action on canal banks were conducted in a laboratory. In addition to the frost heave that was observed during the period of soil freezing, there was an abrupt increase in frost heave that occurred at the beginning of soil thawing. This phenomenon lasted for over approximately 100 hours, and the frost heave induced during this period reached as much as 22.62 mm. At the same time, peak ice pressures also occurred as the soil was thawing. It has been suggested that the frost heave during initial soil thawing may be associated with the change in energy status at the water-ice interface resulting from the buildup of internal stress in the soil during the formation of ice lenses.Key words: frozen soil, freeze-thaw cycle, frost heave, thawing settlement, canal protection.

Tests and Research on Characteristics of Shear Strength of Cement Improved Soil under Freeze-Thaw Cycle

2014 ◽  
Vol 1015 ◽  
pp. 105-109 ◽  
Author(s):  
An Ping Zhao ◽  
Ai Ping Tang ◽  
Jing Sun ◽  
Xue Mei Yu
Keyword(s):  
Shear Strength ◽  
Traffic Safety ◽  
Frost Damage ◽  
Frozen Soil ◽  
Strong Impact ◽  
Silty Clay ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Cement Soil

Roadbed filling undergo at least one freeze-thaw cycle every year in seasonal frozen soil areas, which will lead subgrade to boiling, settlement, strength weakening etc. and has a strong impact on traffic safety and smooth, need to be solved urgently . In recent years, cement improved soil is applied to dissolve frost damage because it can be obtained locally, and has high performance and low price. However, how to evaluate strength of cement soil under repeated freeze-thaw cycles is the key to its further application in those regions. In the paper, the cement improved silty clay is selected as the object which is most common in Heilongjiang roadbed, many groups of freeze-thaw tests and direct shear tests are conducted at different conditions. From these tests, some conclusions about shear strength index and are obtained: 1. the first freeze-thaw cycle has important effect on cohesion of cement soil, during freeze-thaw cycle, the lower temperature is, the faster is decreasing. 2. decreases with freeze-thaw cycles increase, and there is a peak value existing after the seventh cycle, then reduce rapidly. 3. the internal friction angle appears decreasing – increasing–reducing– increasing trend during cycles but the range of change is little. 4. reduces smaller and increases more when temperature is lower.

scholarly journals Effect of freeze–thaw cycle on physical and mechanical properties and damage characteristics of sandstone

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Longxiao Chen ◽  
Kesheng Li ◽  
Guilei Song ◽  
Deng Zhang ◽  
Chuanxiao Liu
Keyword(s):  
Mechanical Properties ◽  
Shear Failure ◽  
Triaxial Compression ◽  
Physical And Mechanical Properties ◽  
Freeze Thaw ◽  
Damage Characteristics ◽  
Large Pore ◽  
Natural Rock ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle

AbstractRock deterioration under freeze–thaw cycles is a concern for in-service tunnel in cold regions. Previous studies focused on the change of rock mechanical properties under unidirectional stress, but the natural rock mass is under three dimensional stresses. This paper investigates influences of the number of freeze–thaw cycle on sandstone under low confining pressure. Twelve sandstone samples were tested subjected to triaxial compression. Additionally, the damage characteristics of sandstone internal microstructure were obtained by using acoustic emission (AE) and mercury intrusion porosimetry. Results indicated that the mechanical properties of sandstone were significantly reduced by freeze–thaw effect. Sandstone’ peak strength and elastic modulus were 7.28–37.96% and 6.38–40.87% less than for the control, respectively. The proportion of super-large pore and large pore in sandstone increased by 19.53–81.19%. We attributed the reduced sandstone’ mechanical properties to the degenerated sandstone microstructure, which, in turn, was associated with increased sandstone macropores. The macroscopic failure pattern of sandstone changed from splitting failure to shear failure with an increasing of freeze–thaw cycles. Moreover, the activity of AE signal increased at each stage, and the cumulative ringing count also showed upward trend with the increase of freeze–thaw number.

Non-linear creep damage model of sandstone under freeze-thaw cycle

2021 ◽  
Vol 28 (3) ◽  
pp. 954-967
Author(s):  
Jie-lin Li ◽  
Long-yin Zhu ◽  
Ke-ping Zhou ◽  
Hui Chen ◽  
Le Gao ◽  
...  
Keyword(s):  
Damage Model ◽  
Creep Damage ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Linear Creep ◽  
Non Linear ◽  
Freeze Thaw Cycle ◽  
Creep Damage Model

scholarly journals Strength and Microscopic Damage Mechanism of Yellow Sandstone with Holes under Freezing and Thawing

2020 ◽  
Vol 2020 ◽  
pp. 1-13 ◽  
Author(s):  
Huren Rong ◽  
Jingyu Gu ◽  
Miren Rong ◽  
Hong Liu ◽  
Jiayao Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Pore Size ◽  
Power Function ◽  
Damage Mechanism ◽  
Uniaxial Compression Test ◽  
Freezing And Thawing ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Microscopic Damage

In order to study the damage characteristics of the yellow sandstone containing pores under the freeze-thaw cycle, the uniaxial compression test of saturated water-stained yellow sandstones with different freeze-thaw cycles was carried out by rock servo press, the microstructure was qualitatively analyzed by Zeiss 508 stereo microscope, and the microdamage mechanism was quantitatively studied by using specific surface area and pore size analyzer. The mechanism of weakening mechanical properties of single-hole yellow sandstone was expounded from the perspective of microstructure. The results show the following. (1) The number of freeze-thaw cycles and single-pore diameter have significant effects on the strength and elastic modulus of the yellow sandstone; the more the freeze-thaw cycles and the larger the pore size, the lower the strength of the yellow sandstone. (2) The damage modes of the yellow sandstone containing pores under the freeze-thaw cycle are divided into five types, and the yellow sandstone with pores is divided into two areas: the periphery of the hole and the distance from the hole; as the number of freeze-thaw cycles increases, different regions show different microscopic damage patterns. (3) The damage degree of yellow sandstone is different with freeze-thaw cycle and pore size. Freeze-thaw not only affects the mechanical properties of yellow sandstone but also accelerates the damage process of pores. (4) The damage of the yellow sandstone by freeze-thaw is logarithmic function, and the damage of the yellow sandstone is a power function. The damage equation of the yellow sandstone with pores under the freezing and thawing is a log-power function nonlinear change law and presents a good correlation.

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