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.
青藏高原是世界上最大的高海拔多年冻土区域，具有气候复杂多变、工程地质条件差、生态环境脆弱、冻土环境不稳定的区域特点。寒区公路建设常常引发边坡失稳病害，边坡支护是解决问题的关键。基于COMSOL软件中的(PDE)模块建立方程，进行二次开发，建立周期为10d的冻结模型，通过软件的二次开发，以青海省祁连山中段的冻土为例，建立冻结过程中格宾石笼挡土墙的位移场、水分场、温度场多场耦合的研究，得到格宾石笼挡土墙在高寒地区的冻结特性。基于格宾石笼挡土墙在高寒地区海拔高、低温低等气候特点，结合COMSOL数值模拟软件，建立格宾石笼挡土墙和土层的多场耦合，得到冻结过程中结冻深度为1.2m,结冻区温度为-4—-1℃,分析了冻土路堑中温度场与水分场和位移场的分布和变化规律、最大位移等数据，为高寒地区道路役性能提供了数据支撑和建议。
青藏高原是世界上最大的高海拔多年冻土区域，具有气候复杂多变、工程地质条件差、生态环境脆弱、冻土环境不稳定的区域特点。寒区公路建设常常引发边坡失稳病害，边坡支护是解决问题的关键。基于COMSOL软件中的(PDE)模块建立方程，进行二次开发，建立周期为10d的冻结模型，通过软件的二次开发，以青海省祁连山中段的冻土为例，建立冻结过程中格宾石笼挡土墙的位移场、水分场、温度场多场耦合的研究，得到格宾石笼挡土墙在高寒地区的冻结特性。基于格宾石笼挡土墙在高寒地区海拔高、低温低等气候特点，结合COMSOL数值模拟软件，建立格宾石笼挡土墙和土层的多场耦合，得到冻结过程中结冻深度为1.2m,结冻区温度为-4—-1℃,分析了冻土路堑中温度场与水分场和位移场的分布和变化规律、最大位移等数据，为高寒地区道路役性能提供了数据支撑和建议。
青藏高原是世界上最大的高海拔多年冻土区域，具有气候复杂多变、工程地质条件差、生态环境脆弱、冻土环境不稳定的区域特点。寒区公路建设常常引发边坡失稳病害，边坡支护是解决问题的关键。基于COMSOL软件中的(PDE)模块建立方程，进行二次开发，建立周期为10d的冻结模型，通过软件的二次开发，以青海省祁连山中段的冻土为例，建立冻结过程中格宾石笼挡土墙的位移场、水分场、温度场多场耦合的研究，得到格宾石笼挡土墙在高寒地区的冻结特性。基于格宾石笼挡土墙在高寒地区海拔高、低温低等气候特点，结合COMSOL数值模拟软件，建立格宾石笼挡土墙和土层的多场耦合，得到冻结过程中结冻深度为1.2m,结冻区温度为-4—-1℃,分析了冻土路堑中温度场与水分场和位移场的分布和变化规律、最大位移等数据，为高寒地区道路役性能提供了数据支撑和建议。
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%。
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%。
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%。
为了探究冻融荷载作用下框锚支护边坡的温度、水分、应力场以及锚杆内力的变化，基于传统水热力耦合方程，建立了考虑排水与补水条件的水热力耦合方程。通过COMSOL软件PDE和固体力学模块接口实现温度、水分及应力场的耦合求解，从而建立框锚支护边坡的多场耦合计算模型，较好地反映了冻融过程中各物理量变化规律。进一步结合室外试验，对比分析冻融期内土体温度、位移、未冻水以及锚杆内力等的监测值与计算值，结果表明：冻结期内，未冻水含量沿地表向下由小到大分布，地表温度变化对土体温度最大影响深度约为2.5 m,导致在融化期出现了2条与地表接近平行的融化带，致使未冻水含量由地表向下由大到小再由小到大分布。由应力分布云图得知，支护前在冻结期边坡没有剪应力集中发展趋势，处于稳定状态；在融化期，土体融沉导致在坡顶和坡地面出现明显的剪应力集中，边坡处于不稳定状态；支护后剪应力集中现象消散，表明支护效果良好。在整个冻融期内，锚杆轴力在冻结期增量最大，在融化期轴力大幅度下降但仍比初始时大，说明坡体发生了永久变形，冻胀变形对锚杆内力影响不容忽视，类似土质气候地区边坡工程中需给予重视。