青藏铁路路堤纵向裂纹形成与扩展的力学机理

在多年冻土区修建路堤,打破了原来天然地表与外界的热力平衡,引起地下温度场重新分布,使得路堤两侧的天然地表下多年冻土融沉,造成整个路堤应力场局部出现应力集中,导致路堤的两侧出现了大量的纵长宽大裂纹。这些裂纹在上覆荷载作用,尤其是列车动荷载或者地震作用下,有可能发生路堤的突然沉陷,严重危害行车安全。就路堤应力集中现象来讨论裂纹的形成和扩展力学机理,即裂纹扩展主要受拉应力作用,而裂纹的扩展角受剪应力的控制。

Mechanical Mechanism of Longitudinal Crack Formation and Growth in Embankment of Qinghai-Tibetan Railway

To construct embankment in permafrost regions, the thermodynamics balance between original surface and environment is broken o At a result, the temperature field underground redistributes and the permafrost below original surface thaw in each sides of embankment. It comes out partial concentration of stress appears in road bed. So, a lot of longitudinal cracks occur along each sides of embankment. Under some conditions, such as moving train or earthquake, the embankment will probably sink abruptly. These are very dangerous to the train. The mechanical mechanism of crack formation and crack growth based on partial concentration of stress of the roadbed are discussed. Crack growth is controlled by tensile stress and crack growth angle which is controlled by shear stress.