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Model-independent strength-reduction factor for effect of spatial variability on tunnel with improved soil surrounds
Géotechnique ( IF 5.8 ) Pub Date : 2020-12-14 , DOI: 10.1680/jgeot.19.p.056
Yutao Pan 1 , Yong Liu 2 , Akanksha Tyagi 3 , Fook-Hou Lee 1 , Dian-Qing Li 4
Affiliation  

Spatially variable cement-treated ground can be considered, in design, as a uniform medium with appropriately reduced strength. Various strength reduction factors have been proposed for cement-treated ground under different loading conditions. However, the Tresca and Mohr–Coulomb models, which are widely used to represent the behaviour of the improved soil in geotechnical design, do not replicate the strain-softening behaviour and therefore may not lead to sufficiently cautious reduction factors. This study examines the effect of constitutive models on the strength reduction factor to account for spatial variability for tunnels with improved soil surrounds. The improved ground was simulated using three different constitutive models. The results show that the Mohr–Coulomb model gives the lowest critical stress release ratio, as the yield stress decreases much faster with effective stress than with the Tresca and cohesive Cam Clay (C3) models. However, the most conservative values of strength reduction factor needed to account for spatial variability are generally taken by either the C3 or Mohr–Coulomb model, depending on the drainage condition and geometric configuration. Hence using the highest strength reduction factor for each case allows spatial variability to be conservatively considered for cases where the Tresca or Mohr–Coulomb model is used.

中文翻译:

空间可变性对改善土壤环境的隧道影响的模型独立强度折减系数

在设计上,可以考虑将空间可变的水泥处理过的地面视为强度适当降低的均匀介质。已经提出了在不同载荷条件下用于水泥处理过的地面的各种强度降低因子。但是,Tresca模型和Mohr-Coulomb模型在岩土设计中被广泛用来表示改良土壤的行为,它们不能复制应变软化行为,因此可能不会导致谨慎的降低因子。这项研究检验了本构模型对强度折减系数的影响,以说明具有改善的土壤环境的隧道的空间变异性。使用三种不同的本构模型对改进的地面进行了模拟。结果表明,Mohr-Coulomb模型给出了最低的临界应力释放率,与有效应力相比,屈服应力的降低要快得多,而Tresca和粘性凸轮粘土(C3)模型的屈服应力却要快得多。但是,考虑排水条件和几何构造,通常由C3或Mohr-Coulomb模型采用考虑空间变化所需的强度降低因子的最保守值。因此,对于每种情况,使用最高强度折减系数可以保守地考虑使用Tresca或Mohr-Coulomb模型的情况下的空间变异性。取决于排水条件和几何形状。因此,对于每种情况,使用最高强度折减系数可以保守地考虑使用Tresca或Mohr-Coulomb模型的情况下的空间变异性。取决于排水条件和几何形状。因此,对于每种情况,使用最高强度折减系数可以保守地考虑使用Tresca或Mohr-Coulomb模型的情况下的空间变异性。
更新日期:2020-12-14
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