浅埋矩形顶管的“整体背土效应”研究

近年来,矩形顶管在地下空间开发中的应用越来越多,国内外学者针对顶管施工对周边地层的影响、顶推力、摩阻力、减摩措施、管节结构等进行了大量研究,并取得了丰硕的成果。但针对浅埋矩形顶管对其正上方土体整体影响的研究较少。结合矩形顶管浅覆土掘进试验,分析了正上方土体的整体破坏过程,提出“整体背土效应”概念。引入4个假定,建立了正上方土体简化模型,提出整体背土效应的前提条件与破坏条件,并给出了相应的预判方法。采用管土全接触理论、库伦剪切破坏强度准则与朗肯土压力理论进行分析,最终得出整体背土效应与顶程、管节宽度、管土摩阻力以及埋深的相互关系,并进行了算例分析。为今后类似工程避免整体背土效应提供一种新的预判分析理论。

Overall-carrying-soil effect of shallow buried rectangular pipe jacking

The shallow-buried rectangular pipe jacking project has gradually increased in recent years. The worldwide researchers have achieved fruitful achievements on thrust, friction and pipe structure. However, there are few researches on the carrying-soil effect of rectangular pipe jacking. So the mechanism of carrying-soil effect is analyzed, and the concept and failure process of the overall-carrying-soil effect are proposed. Four assumptions are proposed to establish the simplified model, and its basic and critical conditions are put forward. Based on the theory of pipe-soil contact, the Coulomb's shear failure strength criterion and the theory of Langham's earth pressure, the prejudgment theory is obtained, which reflects the relationship among overall-carrying-soil effect, jacking length, segment width, pipe soil friction and depth. Then an example is given. The conclusions may provide a theoretical reference for avoiding the overall-carrying-soil effect.