To investigate the effects of freeze-thaw (FT) cycles on the mechanical properties of coarse-grained soil in southeastern Xizang under different moisture contents, this study focuses on coarse-grained soil from a large landslide deposit in Linzhi City, Xizang. FT cycle tests, triaxial shear tests, and numerical simulations were employed to systematically examine the comprehensive impact of varying FT cycles, moisture content, and confining pressure on the soil's mechanical characteristics. The results show that FT cycles significantly affect the stress-strain behavior of coarse-grained soil in southeastern Xizang. The degree of strain softening increased from approximately 11.6% initially to 31.2% after 15 FT cycles, with shear strength decreasing by an average of 31.8%. Specifically, cohesion decreased by 38% to 55% after 0 to 15 FT cycles, and the internal friction angle decreased by approximately 29% to 32%. Additionally, higher moisture content led to more pronounced strain softening and strength degradation, while increased confining pressure effectively mitigated these deteriorative effects. Numerical simulation results indicated that as moisture content increased from 7.6% to 11.6%, the number of FT cycles required to reach the critical instability state decreased from approximately 150 to 106, and finally to only 15, with the maximum equivalent plastic strain increasing from 0.20 to 2.47. The findings of this study provide key mechanical parameters for understanding the formation and evolution of FT landslide disasters in southeastern Xizang and lay a scientific foundation for the assessment and long-term prevention of cold-region geological hazards.

Commercial software packages for FEM analysis have been used to numerically simulate the behaviour of the complex systems of bentonite-bonded sand mould under pressure and subjected to stress distributions and to predict their performance. The Drucker-Prager model and the Mohr-Coulomb model are two well-known mathematical models used to describe the plastic non-linear behaviour of the soil. Conducting direct shear tests on varying densities of sand can provide the individual parameters necessary for the simulation of the moulding process. A new approach is based on making relationships between micro-mechanical parameters and changes in sand density during the compaction process. COMSOL Multiphysics is a popular software tool used to implement FEM simulations. The steps involved drawing geometry, inserting material properties, mesh generation and time-dependent density, and solving the model. The boundary conditions depend on the particular problem being analysed, which defines the external forces and constraints acting on the structure. The use of a coarse mesh and stationary study may be a computationally efficient approach for the evaluation of the compaction process of green sand. The study found that the maximum displacement value is 6.1*10-3 mm, the maximum volumetric strain value is 8.88*10-5, and the von Mises stress is 4.14*103 N/m2. On a utilise des progiciels commerciaux disponibles pour l'analyse FEM pour simuler numeriquement le comportement des systemes complexes de moules en sable lie a la bentonite sous pression et soumis a des distributions de contraintes, et pour predire leurs performances. Le modele Drucker-Prager et le modele Mohr-Coulomb sont deux modeles mathematiques bien connus utilises pour decrire le comportement plastique non lineaire du sol. Mener des essais de cisaillement directs sur des densites variables de sable peut fournir les parametres individuels necessaires a la simulation du procede de moulage. Une nouvelle approche est basee sur l'etablissement de relations entre les parametres micromecaniques et les changements de densite du sable au cours du procede de compactage. COMSOL Multiphysics est un outil logiciel populaire utilise pour mettre en oe uvre des simulations FEM. Les etapes impliquaient le dessin de la geometrie, l'insertion des proprietes des materiaux, la generation du maillage et de la densite en fonction du temps, ainsi que la resolution du modele. Les conditions aux limites dependent du probleme particulier analyse, qui definit les forces et les contraintes externes agissant sur la structure. L'utilisation d'un maillage grossier et d'une etude stationnaire peut constituer une approche informatique efficace pour evaluer le procede de compactage du sable vert. L'etude a trouve que la valeur de deplacement maximale etait de 6.1*10-3 mm, la valeur de deformation volumetrique maximale etait de 8.88*10-5 et la valeur de contrainte de von Mises etait de 4.14*103 N/m2.

Diaphragm walls are rectangular shaped cast in place deep foundations. There are two critical phenomena occurring, according to which the final quality can be affected: bentonite suspension exfiltration and concrete placement. Some imperfections seem to appear recurrently on the surface of the final wall. The defects are known as shadowing pathologies. The main reasons can be attributed to the dual effect of exfiltration mechanisms and kinematics of concrete flow. The objective of this study is developing a numerical tool to prevent the appearance of shadowing pathologies by visualizing the concrete flow in the presence of a bentonite suspension. This paper presents the results obtained from 2D and 3D models of diaphragm wall construction using COMSOL Multiphysics. The CFD model helped in solving a multifluid and particularly a two-phase flow. The 2D modeling has considered a fresh slurry and an exfiltrated (or polluted) suspension neighboring soil and followed concrete flow with two rheological behaviors in two reinforcement configurations. Then, 3D simulations were compared to actual experimentation results, which were undertaken to construct diaphragm walls in the laboratory. By comparing the results of the simulations to the experimental outcomes, it has been possible to validate the model. The resulting simulations could clearly explain the occurrence of the pathology where the flow pattern and volume fraction of the fluid flow were determined. From the results obtained, it can be conducted that a compliant concrete mix but at the lower limit for the consistency recommendations, leads to pathologies, just like a polluted slurry.

渠道设置复合保温材料会削减基土冻胀力，削减渠道坡板不均匀冻胀后产生的位移，但研究尚未探明渠道复合保温材料抗冻机理。以新疆玛纳斯电站引水梯形渠道衬砌结构下施加高分子聚合材料为实际工程背景，考虑复合材料界面接触热阻本构及冻土与复合材料的相互作用关系，依据渠道热力耦合机理建立了寒区渠道混凝土衬砌保温结构冻胀模型，提出了3种新型复合材料保温形式，并采用COMSOL Multiphysics5.2a进行数值仿真对比分析。结果表明：与普通渠道相比，3种保温形式均具有一定的效果，且第3种保温形式的抗冻性和保温效果最明显，该形式作用下渠阴坡、渠阳坡、底板最大法向冻胀位移分别为9.63、4.74、1.87 cm,形式1、形式2、形式3较原型渠道冻胀力分别减少65.8%、76.2%、89.5%。

多年冻土内部的水热过程是影响冻土区生态环境演变、干旱区水资源利用及地表工程结构稳定性的重要因素。然而传统的水热耦合理论模型忽略了非饱和土体中水分对流传热作用,在水分场与温度场耦合理论模型的数值实现上仍有困难。以垂直土柱单向冻结实验为基础,通过COMSOL Multiphysics软件的数学模块实现考虑冰水相变和水分对流的温度场和水分场偏微分方程的耦合求解,分析了冻土水分对流与温度变化的关系。结果表明:(1)COMSOL可以实现冻土水热参数、冰水相变潜热以及边界条件的灵活定义,容易实现水热两场耦合分析;(2)对于含水量较高的土体,水分对流传热作用不可忽略。