Development of Designing Technology for Chilled Gas Pipeline Utilizing the Mechanical Properties of Frozen Soil and Ice Layer

采用轴对称冻结装置，对圆柱形试件的周长进行约束，得到了管道与结霜球边界处的约束法向应力，并进行了结霜强度试验。通过改变管内流动的防冻液的温度，可以控制结霜球的生长，可以预期试件内部的内应力分布和边界处的法向应力会发生相应的变化。通过7例不同约束条件下的试验，观察了冻结剂粘结强度的变化。结果表明，边界处的正应力是影响胶结强度的重要因素之一，由于正应力的影响，剪切应力与相对位移的关系呈现非线性，而应力的强度增强了胶结的耐久性。管道与冻球相互作用的建模改进了分析应力评估模型，考虑了作用于试件周界的约束应力变化所对应的试件内部应力分布。在此基础上，利用数值方法对边界处的法向应力进行了估计，并成功地评价了法向应力对固结强度的影响。该模型可扩展为多维评价模型，作为设计的实用模型。研究结果为冻胀作用下冷冻天然气管道设计方法的建立奠定了基础。

Adfreeze Bond Strength ExperimentAdfreeze Bond Strength Experiment was carried out by an axis-symmetric freezing apparatus with constraining the perimeter of the cylinder shaped specimen in order to give the constraining normal stress at the boundary between the pipe and frost bulb. By changing the temperature of the antifreeze flowing in the pipe, it can be possible to control the growth of the frost bulb and it can be expected that the internal stress distribution within the specimen as well as the normal stress at the boundary vary correspondently. Through 7 cases of the experiment with different constraining conditions, the change in adfreeze bond strength was observed.As a result, the normal stress at the boundary is confirmed as one of the most important factors for adfreeze bond strength and the relationship between shear stress and relative displacement shows nonlinear property due to the effect of the normal stress and the intensity of the stress enhance the durability in bonding.Modeling for Interactive Action between the Pipe and the Frost bulbThe analytical stress evaluation model was improved to consider the stress distribution within the specimen corresponding to the change in the constraining stress acting on the perimeter. Based on this model, it became possible to estimate the normal stress at the boundary and the effect of it on the adfreeze bond strength was successfully evaluated by the means of numerical approach. This model is thought to be expanded to multi-dimensional evaluation model as a practical model for design. It is convinced that fundamental findings for the establishment of designing method for chilled gas pipeline under frost heave action are obtained.