Influence of Freezing-Thawing on Shear Strength of Frozen Soil in Northeast China

Abstract

In order to study the influence of freezing-thawing cycles on shear strength of seasonal frozen soil in northeast China, silty clay, typical soil in Jilin region, was selected. 20 groups of specimens were carried out by quick shear tests considering soil water content and the number of freezing-thawing cycling. The test results indicate that soil cohesion presents the slight fluctuation with the increase of water content, and the maximum value reaches around the peak of liquid limit. Internal friction angle of soil shows the sharp drop and the extent changes between 40% - 60%. The soil cohesion gradually declines with the increase of the number of freeze-thawing cycling. Therefore, the effect of the first freezing-thawing cycle on soil cohesion is obvious, and cohesion gradually tend to be stable after 7 freezing-thawing cycles. The final value of cohesion is approximate a third to a half of the unfrozen soil. The internal friction angle of soil increases with the augment of cycling number of freezing-thawing, which is related to the water content. The higher water content will bring about the greater growth rate of friction angle.

A novel theoretical model to predict thawing settlement of clayey permafrost

“…In engineering, the increased loading exacerbates the embankment's settlement, particularly when the embankment encases a thick ice layer. Hazirbaba [29] conducted freeze-thaw cycles on remoulded soil in 2019 and discovered settlement is closely related to the excess pore pressure in train cyclic loading [6]. Frost boiling and mud pumping are caused by the dramatically varying pore pressure during the thawing process being unable to easily be released from fine-grain soil.…”

“…The 𝐴 0 − 𝑊 𝑖 linear relationship was also fitted as the 𝐴 0 = 𝑎𝑙𝑛𝑊 𝑖 − 𝑏 mode by some previous researchers [6,10] and the 𝐴 0 = 𝑎𝑙𝑛𝜌 𝑑 − 𝑏 mode was also adopted in the dry density perspective [6,8,11]. The log-linear is better than the linear relation because the log operation converts some nonlinear properties into linear ones.…”

“…Chen [6] is 67.99%, from Guo [10] is 68.91%, from Dong [11] is 75.11%, from Qin [9] is 80.10%, from Chen [8], for the peaty soil is 70.06%, for the grassy charcoalous soil is 81.26% and from Lu [7] is 55.36%. So it can be roughly summarized the maximum 𝐴 0 of clayey permafrost of different regions is between 55% to 82%, and the average maximum value is about 68%.…”

“…𝜉 = 0 or 𝜉 = 1 corresponds to the upper limit or lower limit of 𝜅 − 𝐴 0 distribution lines. (6) The two-exponential-term fittings for 𝜅 − 𝐴 0 under 𝜉 = 0 and 𝜉 = 1 have the same amplitude coefficient, with this property, the area surrounded by maximum 𝐴 0 , a certain value of 𝐴 0 , (𝜅 − 𝐴 0 ) 𝜉=0 and (𝜅 − 𝐴 0 ) 𝜉=1 is defined as the happening probability of the certain value of 𝐴 0 . The happening probability list corresponding to the certain 𝐴 0 can be applied to engineering as a reference.…”

Analysis and Evaluation on Residual Strength of Pipelines with Internal Corrosion Defects in Seasonal Frozen Soil Region

“…The methods and conclusions can provide valuable references for simulation real-time monitoring and safety analysis in the pipeline operation stage. According to the geological exploration data of the frozen soil in Northeast China [18][19][20][21][22][23][24], the modelled depth was selected to be 20 m below the natural ground, the modelled length was 100 m, and the modelled width was 40 m. The soil of buried pipeline was divided into non-frost heaving section (10 m) + transition section (20 m) + frost heaving section (40 m) + transition section (20 m) + non-frost heaving section (10 m) = 100 m. The simplified soil layers from top to bottom were silty clay layer with a thickness of 3 m, fine sand and gravel layer with a thickness of 7 m and weathered bedrock residue layer with a thickness of 10 m. The diameter of the pipeline was 0.762 m, the wall thickness was 0.0175 m, the thickness of the insulation layer was 8 cm, and the buried depth was 1.6 m.…”