不同土质围岩条件下隧底围岩脱空规律与结构受力特征研究

Cavity Laws and Structural Stress Characteristics of Tunnel Bottom Surrounding Rock under Different Soil Surrounding Rock Conditions

针对铁路隧道隧底围岩脱空病害问题,采用室内试验与数值模拟方法,探明不同土质围岩类型、隧底结构形式条件下隧底围岩脱空演变规律,给出不同土质围岩类型条件下隧底围岩脱空类型;进而,明确不同脱空类型条件下隧底结构受力特征。研究结果表明:1)在相同隧底围岩类型条件下,底板结构形式比仰拱结构形式更易发生围岩脱空现象;相同隧底结构条件下,黏性土、卵石土、砂质土3种隧底围岩的脱空程度依次降低。2)隧底围岩脱空类型主要与围岩类型有关;卵石土、黏性土和砂质土围岩最终脱空类型依次为多处小范围局部脱空、整体性脱空、隧底中心区域大范围脱空。3)在相同围岩脱空类型条件下,底板结构受力特征变化比仰拱结构更为剧烈,应力集中现象更为明显,更易引发隧底结构损坏。4)随着脱空范围增大,隧底结构弯矩变化量、轴力减小量均呈增大趋势,轴力分布逐渐呈"中间大,两端小"的不均匀分布形态。

In order to solve the cavity problem of surrounding rock at tunnel bottom,the cavity evolution of surrounding rock at tunnel bottom under different soil surrounding rock conditions and structural styles are analyzed based on the laboratory experiments and numerical simulations,and the cavity types of tunnel bottom surrounding rock under different soil surrounding rock conditions are given.Furthermore,the stress characteristics of tunnel bottom structure under different caving types are cleared.The results show that:(1)Under the condition of the same tunnel bottom surrounding rock type,the cavity phenomenon is easier caused by floor structure than inverted arch;under the condition of same tunnel bottom structure,the cohesive soil can cause cavity phenomenon most easily,followed by pebble soil and sandy soil.(2)The type of tunnel bottom surrounding rock cavity is mainly related to the type of surrounding rock,and the cavity types of surrounding rocks of pebble soil,cohesive soil and sandy soil are local cavity in a small area,global cavity in a whole area and large scale cavity in the central area of tunnel bottom,respectively.(3)Under the condition of the same cavity type,the stress characteristics of the floor structure vary more dramatically than the inverted arch structure,the stress concentration is more obvious,and the tunnel bottom structure is more prone to damage.(4)With the increase of the cavity range,the variation of bending moment and the decrease of axial force of the tunnel bottom structure all show an increasing trend,and the distribution of the axial force gradually shows an uneven pattern of"large in the middle and small at both ends".