Abstract When constructing a new railway line, its long length means there are significant financial implications associated with determining the geodynamic ground properties. Therefore, this paper presents recommendations to optimize the efficiency and depth of such a geotechnical site investigation. Firstly, a numerical analysis is performed to investigate the effect of soil layering, soil stiffness and track bending stiffness on critical velocity. It is shown that each of these variables play an important role, however for most practical cases, only the top 8 m of soil is influential. Track dynamics are rarely affected by soil properties at depths below this, meaning this is the maximum required depth of soil investigation. Using this knowledge, a hybrid experimental-analytical methodology is presented, based on a geophysical Spectral Analysis of Surface Waves (SASW) experimental setup to compute the ground dispersion curve and an analytical model to compute the track dispersion curve. The experimental and analytical results are combined directly, to accurately compute the critical velocity. This approach is attractive because: 1) SASW tests are typically accurate to ≈8 m (when using a mobile exciter) thus matching the required depth needed for critical velocity computation, 2) soil property uncertainties are inherently accounted for, 3) the uncertainties associated with SASW inversion are avoided. The approach is attractive when constructing new railway lines and upgrading the speed of existing lines because it can potentially yield site investigation cost savings. In-situ field work is performed to show the practical application of the technique.

中文翻译：

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铁路临界速度评估：一种简单的实验分析方法

摘要 在建设一条新铁路线时，其较长的长度意味着与确定地球动力学地面特性相关的重大财务影响。因此，本文提出了优化此类岩土工程现场调查的效率和深度的建议。首先，进行数值分析以研究土壤分层、土壤刚度和轨道弯曲刚度对临界速度的影响。结果表明，这些变量中的每一个都起着重要作用，但是对于大多数实际情况，只有土壤的顶部 8 m 有影响。跟踪动态很少受低于此深度的土壤特性的影响，这意味着这是土壤调查所需的最大深度。利用这些知识，提出了一种混合实验分析方法，基于表面波地球物理光谱分析 (SASW) 实验装置计算地面频散曲线和分析模型计算轨道频散曲线。直接结合实验和分析结果，准确计算临界速度。这种方法很有吸引力，因为：1) SASW 测试通常精确到 ≈8 m（当使用移动激励器时）从而匹配临界速度计算所需的深度，2) 土壤性质的不确定性是固有的，3) 相关的不确定性避免了 SASW 反转。这种方法在建设新铁路线和提升现有线路的速度时很有吸引力，因为它可以潜在地节省现场调查成本。