模型试验研究是探讨土体-结构系统的力学响应机制的重要手段之一。针对西安地铁二号线地铁隧道模型模拟中存在的问题，首先讨论了隧道结构模型试验相似比尺关系，分析了模型试验中相似材料的选用原则和关键问题，然后基于两种不同的几何相似程度，比较讨论了模型几何相似程度对隧道模型和隧道原型结构之间应力与弯矩结果的影响程度，在同等条件下两种不同的几何相似比尺设计的缩尺模型导致隧道原型结构的应力值的差异超过12%，隧道原型结构的弯矩值的差异超过140%。研究结果表明，几何相似程度决定了模型相似比尺设计的合理性，从而成为模型试验能否合理、高精度地反映和模拟原型结构力学响应的关键性制约因素之一。

The model test study is one of the important means to explore the mechanical response mechanism of soil and structure system. Aimed at model simulation of Xi'an Metro Line 2 tunnel, this paper firstly discusses the similar scale relation of tunnel structure model test, analyzes the selected principles and the key problems of similarity material in model test. Then based on two different geometry similarity levels, the effects of geometric similarity levels on the results of stress and bending moment between the model and prototype tunnel structure are compared and discussed, and the stress error of tunnel prototype structure is more than 12%; while the error of bending moment is more than 140%. The study results show that the geometric similarity level determines the rationality design of model similarity scale, thus it becomes one of the key restriction factors whether the model test can reasonably and accurately simulate the mechanical response of prototype structure.