软硬不均地层沉管隧道碎石基床力学特性研究

Mechanical characteristics of gravel bed for immersed tube tunnels in heterogeneous ground

为揭示软硬不均地层下沉管隧道碎石基床力学特性,通过有限元分析及理论计算,对沉管隧道纵横向地基沉降及刚度的分布规律、参数敏感性及结构纵向受力响应问题进行量化分析,结果表明:岩基段基底压力分布中间小两侧大,中间位置会出现脱空,软基段为两端小中间大,结构两端会出现脱空;岩基与软基的基底应力值较为接近,但地基刚度相差较大,岩基段为软基段的14倍;岩基段地基纵向刚度受垫层厚度、模量及预压荷载等参数影响变化大,应以岩基段垫层设计厚度作为全线的控制标准;软基段接头平均剪力约为岩基段的3倍;软硬不均地层沉管隧道碎石基床力学特性研究为沉管法隧道在复杂地质条件下推广应用提供了重要参考意义。

In order to reveal the mechanical characteristics of gravel bed of immersed tube tunnel in heterogeneous ground,a quantitative analysis was conducted through finite element analysis and theoretical calculation on the distribution law,parameter sensitivity,and structural longitudinal stress response of the vertical and horizontal foundation settlement and stiffness of the immersed tunnel.The results show that the pressure distribution at the base of the rock foundation section is small in the middle and large on both sides,and hollowing occurs in the middle.The soft foundation section is small at both ends and large in the middle,and hollowing occurs at both ends of the structure.The base stress value of the rock foundation and the soft foundation are relatively close,but the stiffness of the foundation differs greatly,and the rock foundation section is 14 times of the soft foundation section.The longitudinal stiffness of the rock foundation section is greatly affected by the parameters such as the thickness,modulus and preload of the cushion.The design thickness of the cushion layer in the rock foundation section should be used as the control standard for the entire line.The average shear force of the joint of the soft foundation section is about 3 times that of the rock foundation section.The study on the mechanical characteristics of gravel beds for immersed tube tunnels in heterogeneous ground provides an important reference significance for the promotion and application of immersed tube tunnels in complex geological conditions.