堆载作用下土体分层特性对地铁隧道纵向变形的影响研究

Influences of soil characteristics on longitudinal deformation of shield tunnels induced by surface surcharge

随着城市化进程的不断推进,地铁隧道附近可能会出现不同形式的地表堆载,将对地铁隧道的健康状态产生不利影响。现有的方法多是基于Boussinesq解求解地表堆载引起的附加应力,无法考虑土体的分层特性。首先采用Fourier积分变换得到了直角坐标系中竖向荷载作用下层状地基附加应力的基本解;然后将下卧隧道视为Timoshenko梁,基于Winkler地基模型和两阶段法求得隧道纵向位移和内力。为考察地基土成层性对既有隧道性状的影响,对上软下硬、上硬下软两种典型层状地基中的隧道进行了参数分析。结果表明:地基土成层特性对隧道形状影响比较大,相比而言,隧道下卧土层控制沉降的效果要优于隧道上覆土层。

With the development of urbanization in China, it is common to find the surface surcharge in a large scale around the metro tunnels, which will seriously threaten the safety of the lining structures and their service capability. To obtain the additional stress on the axis of shield tunnels caused by the surface surcharge, the Boussinesq’s solution is widely adopted, whereas it cannot be applied in multi-layered soils. In this study, firstly, the additional stress in multi-layered soils is obtained by using the Fourier integral transformation. Secondly, the existing tunnel is regarded as the Timoshenko beam, and the displacements and internal forces exerted on the shield tunnel are obtained based on the two-stage method. From the proposed method, it can be found that the underlying layer has larger influences on the settlement of shield tunnels than those by the overlying soils.