Genesis, characteristic and disaster effects of loess meso-interfaces: A field geological investigation

Abstract

Loess meso-interfaces are geologically structural surfaces visible to the naked eye (i.e., 0.1 mm to 1 m), mainly including meso-cracks and meso-pores. They disrupt the integrity of loess mass and significantly influence the failure of loess slope. However, the current understandings of the genesis, characteristic, and disaster effects of loess meso-interface are incomplete, particular in a field scale. To address this gap, an extensive field geological investigation was carried out to study the loess meso-interfaces on the Chinese Loess Plateau. Results show that the genesis of loess meso-interfaces includes geo-stress, gravity, biological activity, water, and weathering. The meso-interfaces primarily distribute within the 3.0 m depth of shallow layer on loess slopes. The single meso-cracks are typically shaped as saw-tooth, needle tip, ring, and hook, while the patterns of arborescent morphology, stepped arrangement, feather-like pattern, irregular polygon, cross-cutting arrangement, and parallel lineation are exhibited by the multiple meso-cracks. The dominate width of loess meso-cracks ranges from 0.1 mm to 1 mm, and their angles mainly ranges from 60° to 120°, with a peak intensity around 90°. The three-dimensional morphologies of meso-pores are shaped as ellipsoid, flatten sphere, tube, and pore network connected by tube-like pores. The more irregular the meso-pores, the larger their volume, but the fewer their number. The loess meso-interfaces promote geological disasters in shallow layer on slopes by separating, loosening and providing seepage channels. The development of loess meso-interface is characterized by a successive initiation process, accompanied by the transformation of disaster effects. In addition, the location of loess meso-interface contributes to the different evolution modes of slope disaster.