基于合理拱轴线的偏压隧道最优断面研究

Study on the optimal shape of biased-pressure tunnel based on rational arch axis

偏压隧道是工程中常见的一种隧道形式,隧道的断面形状会影响到衬砌结构受力性能和围岩的稳定性。针对偏压隧道的断面形状优化设计,基于衬砌合理拱轴线,开展偏压隧道最优断面形状的研究。根据偏压隧道的工程特点,建立初始断面形状为圆形的偏压隧道有限元模型,计算得到隧道衬砌的弯矩、轴力和偏心距。进一步,以偏心距最小作为目标函数,通过反复调整衬砌轴线的位置,使衬砌轴线逐渐逼近合理拱轴线,从而获得偏压隧道的最优断面。在此基础上,对比研究偏压隧道优化前后衬砌的力学性能和隧道围岩的应力分布情况。结果表明,这种最优断面形状的偏压隧道极大改善衬砌结构受力状况,衬砌主要承受轴向压力作用,能够充分发挥混凝土材料的抗压性能,而且隧道围岩的应力分布均匀,避免了隧道围岩的应力集中。

Biased-pressure tunnel is a typical form of tunnel in engineering,and its cross-section shape can affect the mechanical performance of the lining structure and the stability of the surrounding rock-soil.Aiming at the shape optimization of biased-pressure tunnel,in this paper the investigation on optimal tunnel shape is performed based on the rational arch axis.According to its engineering characteristics,the FEM model of biased-pressure tunnel with initial circular shape is established,and the bending moment and axial force of tunnel lining are calculated to obtain the lining eccentricity.In optimization iterations,the lining axis is gradually approximated to the rational arch axis by repositioning the lining axis continuously,and the optimal cross-section of the biased-pressure tunnel is finally obtained when the eccentricity is approaching its minimum.On this basis,the mechanical performance of the lining and the stress distribution in rock-soil around the tunnel are studied.The results show that this tunnel with the optimal cross-sectional shape has a great improvement in mechanical performance of the lining,which is mainly subjected to axial compression and can fully utilize the compressive properties of the concrete material.Besides,the stress distribution in surrounding rock-soil is smooth and the stress concentration can be avoided effectively.