湿陷性黄土与地铁地下结构相互作用机理研究

Study on Interaction Mechanism between Collapsible Loess and the Subway Underground Structure

为研究湿陷性黄土与地铁地下结构相互作用机理,文章基于黄土地区地铁工程经验,通过理论分析探讨了地铁工程地基承载力工作原理、黄土地层中地下结构的土压力作用原理等,指出了地铁结构作为地下中空构筑物与一般工业与民用基础的区别;通过实例计算研究了地铁结构基底压力、黄土湿陷引起的结构侧向土压力及顶部土压力变化规律。研究结果表明:1)地铁地下结构工作原理不适用于地基土体侧向滑移并被挤出的传统与经典地基承载力理论,它产生的基底压力小于原基底土的自重压力,类似于地基与基础设计中有利的补偿性基础;2)黄土饱和浸水湿陷瞬间,土的抗剪强度是饱和快剪指标,其侧压力系数趋近于1.0,设计时应予以考虑;3)黄土地层中如隧道洞身范围土体发生湿陷变形,隧道顶板所受的竖向土压力值较未发生湿陷变形时显著增大,设计时应予以考虑。

In order to study the interaction mechanism between collapsible loess and underground structure of the metro,the working principle of foundation bearing capacity of metro underground engineering and the principle of earth pressure acting on underground structure in loess stratum were discussed through theoretical analysis based on the experience of underground engineering in loess area.The differences between underground structure as underground hollow structure and general industrial and civil foundation were presented.The variations of base pressure,lateral earth pressure and top earth pressure caused by collapsibility of loess in underground structure of metro were studied through case calculations.The results show that:(1)the working principle of metro underground structure is not applicable to the traditional and classical theory of bearing capacity of foundation soil which is laterally slipping and extruded,and the base pressure generated is less than the self-weight pressure of original base soil and the base is similar to the favorable compensatory foundation in foundation and foundation design;(2)shear strength of loess is a saturated fast shear index at the moment of loess collapsing due to saturated water soaking,the lateral pressure coefficient approaches 1.0 which should be taken into account in design;(3)In loess stratum,if collapsible deformation of soil occurs within the scope of tunnel main body,the vertical earth pressure on tunnel roof increases significantly compared with that without collapsible deformation,which should be considered in design.