CT- and multi-monitoring ready thermo-frozen-hydro-mechanical 3D loading system

鉴于即将到来的气候变化，冻土材料的分析对于城市地区的适应或缓解以及对正在发生的地质现象的理解具有根本的重要性。由于底土的高刚性，目前存在的永久冻土对于确保其中封装的有机碳和稳定现有的土壤结构至关重要，例如冰冻圈中的持续和季节性冻土（冰冻土）、堤防、地基。在这里，必须提高对改变耦合的冷冻-水-机械土壤特性的基本理解，以便除了通过融化或循环，交替融化/冻结上层冻土的过渡而改变的化学，生物过程外，所产生的水力，机械变化，如风化，刚度和强度的损失，霜冻相关的混合和侵蚀可以进行评估和建模。在交替解冻/冻结条件下，冰分离、冰积累和低温变态等低温过程的变化也是未知的。在适应城市生活和缓解日益增加的城市热点的过程中，基础设施的制冷变得更加重要。要做到这一点，城市冰库必须按地质规模建造。这方面的初步研究已经在进行中。从结构工程的角度来看，具有承载能力或防止破坏的冻结过程是已知的。循环冻结过程，如使用冰库所需的那些过程，就其影响而言是完全未知的。冻融循环滞后对Atterberg极限下体积孔隙空间和结构变化的影响以及机械强度和压缩性退化的影响很少被分析，并且对细颗粒比例较大的沉积物有显著影响。对这些沉积物的周期性冻融循环进行可靠的地质力学预测尚不可能。为了模拟冻土的循环冻水力学材料行为，需要进行大量不同的实验试验，为此需要购买以前不存在的实验室装置。对于土样的实验三维分析，需要获得一个循环冷冻-热-水-机械加载的三维压力系统，除了循环冻结/解冻外，还允许在样品上和测试过程中直接安装进一步的监测设备（用于颗粒图像速度的数码相机、热像仪、激光技术、μCT、雷达等）。这样就可以将结构的局部变化以高分辨率的层析成像或地面图的形式记录下来，并转移到建模中。

In view of the upcoming climate change, the analysis of frozen soil materials is of fundamental importance for the adaptation or mitigation in urban areas as well as for the understanding of occurring geological phenomena. The currently existing permafrost soils are essential in securing the organic carbons encapsulated therein and in stabilizing the existing soil structures, such as constantly and seasonally frozen soils (cryosols) in the cryosphere, embankments, foundations, due to the high rigidity of the subsoil. Here, the basic understanding of changing the coupled cryo-hydro-mechanical soil properties must be improved, so that in addition to the changed chemical, biological processes through the thawing or the transition of the cyclical, alternating thawing / freezing of upper cryosols, the resulting hydraulic, mechanical Changes such as weathering, loss of stiffness and strength, frost-related mixing and erosion can be assessed and modeled. Changes in the cryopedogenic processes such as ice segregation, ice accumulation and cryometamorphosis under alternating thawing / freezing are also unknown.In the adaptation of urban life and the mitigation of increasing urban heat hotspots, the cooling of infrastructures becomes more important. To do this, urban ice stores must be built on a geological scale. Initial research on this is already in progress. From a structural engineering point of view, freezing processes with the load-bearing capacity or protection against failure are known. Cyclical freezing processes, such as those required for the use of ice storages, are completely unknown in terms of their effects. The effects of cyclical freeze-thaw hysteresis on the volumetric pore space and structure changes, in the Atterberg limits or mechanical strength and compressibility degradations have hardly been analyzed and have significant effects on sediments with a larger proportion of fine particles. Secure geomechanical forecasts for these sediments for cyclical freeze-thaw cycles are not yet possible.For the modeling of the cyclic cryo-hydro-mechanical material behavior of frozen soils, a large number of different experimental tests are to be carried out, for which a previously non-existent laboratory device is to be purchased. For the experimental 3D analyzes of the soil samples, a 3-dimensional pressure system for cyclical cryo-thermo-hydro-mechanical loading is to be acquired, which in addition to the cyclical freezing / thawing, the additional installation of further monitoring devices (digital cameras for particle image Velocity, thermography cameras, laser technology, μCT's, radar, etc.) are allowed directly on the sample and during the test process, so that local changes in the structure can be recorded in high resolution as tomography or surface plot and transferred to the modeling.