盾构法隧道施工数值模拟

盾构法隧道施工在城市地下工程建设中有着广泛的应用前景。分别采用可以考虑土体小应变特性的本构模型与修正剑桥模型对盾构隧道施工进行了数值分析。这两种模型的计算结果的规律性是相似的;采用修正剑桥模型计算的沉降量、开挖影响范围受盾构施工质量的影响不大;采用土体小应变本构模型计算结果对盾构施工质量很敏感。盾构开挖过程中土体的有代表性的应力路径大都在修正剑桥模型屈服面之内,判断为卸载,即使有部分加载路径,根据剑桥模型计算的变形也不大,小应变本构模型合理地定义了加卸载,可以反映土体小应变时的高刚度,随应变增大土体刚度的迅速减小过程,因而较好地反映了施工质量对地表沉降的影响。分析表明小应变本构模型计算结果是合理的,也证明了考虑土体小应变特性的必要性。

Numerical simulation of excavation of shield tunnel

Shield tunnel is an attractive excavation method in the construction of municipal underground engineering. The ground subsidence is the most noticeable problem in the excavation of shield tunnel. The influence of shield tunnel is numerically simulated by adopting the small-strain constitutive model provided by authors, and the modified Cam-clay model, respectively. The computed results of these two models are similar. The ground subsidence and the impacted area in the computed results of the modified Cam-clay model are affected by construction quality slightly, but the computed results of the model provided by authors are sensitive to construction quality. These are related to the judgment of loading-unloading, and the simulation of the small-strain mechanical characteristics are more reasonable in the small-strain constitutive model. The further analysis shows that the computed results of the small-strain constitutive model are more reasonable, and the small-strain mechanical behaviors of soils should be taken into account.