沉管隧道离心模型试验及数值模拟

CENTRIFUGAL MODEL EXPERIMENT AND NUMERICAL SIMULATION OF IMMERSED TUBE TUNNEL

沉管隧道在开挖及回填过程中基底应力分布特征及其与沉管结构的变形特性分析在隧道工程中占重要地位。通过以港-珠-澳沉管隧道天然地基段某一横断面为研究对象,对整个施工过程进行不同垫层厚度的离心模型试验及有限元计算模拟,揭示沉管隧道天然地基开挖回弹及回填再压缩应力分布及变形特征、沉管结构的应变特征及垫层厚度对其影响,为沉管隧道的施工及地基处理方案设计提供参考。结果表明,开挖卸荷使基底产生拱形分布回弹。回填后基底应力呈马鞍形分布,仅中间部分应力随时间及回淤增加而增大;沉管底板应变呈马鞍形分布,工后应变量变化不大。垫层厚度变薄使基底应力分布匀化效果差,回填再压缩量及工后沉降量变大。

Base stress distribution characteristics and the deformation characteristics of immersed tube tunnel in excavation and backfilling process of tunnel engineering occupy an important position. Taking one cross-section of the natural foundation in Hong Kong-Zhuhai-Macao immersed tube tunnel as research object, centrifugal model test and finite element simulation of the whole construction process with different cushion layer thickness were carried out. When excavation rebound and backfilling compression in the immersed tube tunnel, stress distribution and deformation characters of natural foundation, the strain characteristics of immersed tube structure and the influence of cushion layer thickness were revealed, which provided the design basis for the construction of immersed tube tunnel and scheme of ground treatment. The results showed that excavation unloading made basement produce arch distribution rebound. Basal stress distribution was the shape of a saddle after backfill, and only the stress in the middle of base was increasing with time and silting. The strain distribution of immersed tube plate was the shape of a saddle and strain had little change after construction. The thinning of the cushion layer thickness led to a poor smoothing effect on basal stress distribution, and recompression quantity and foundation settlement after construction become large.