Loess Dark Cave Effect Of The Causes And Highway Engineering Disaster Research

On the basis of field research and systematic analysis of the predecessors' achievements, for the first time this dissertation has established a practical system to classify and denominate hidden holes in loess, zoned the loess plateau according to the developmental density of hidden holes, studied and summarized the intrinsic relations between the distribution of hidden holes and topography, geomorphology, the property of soil, as well as their developmental depth. The genesis and the formation mechanism of hidden holes in loess are lucubrated. According to the path, the mode and the consequence of the action of water, the formation pattern of hidden holes has been generalized as the following five types: abrasion-breakthrough, abrasion-underground erosion-breakthrough, collapse-underground erosion-breakthrough, abrasion-underground erosion--collapse-underground erosion-breakthrough and the compound. Based on this, the formation and evolutionary process of hidden holes in loess is divided into five periods as follows: incubation period, formation period, developmental period, breakdown period, and extinction period. Meanwhile, this paper has fundamentally unified the viewpoint on the causes of hidden holes in loess, collapse and underground erosion as the main causes in incubation period, underground erosion and abrasion in formation period, abrasion in developmental period, gravity collapse and abrasion in breakdown period.Since hidden holes in loess frequently cause damages to highway projects, the study has been focused on the damages and their formation mechanism on the basis of a thorough generalization of their damage types. By means of numerical simulation, this paper has further analyzed the variation of stresses and breakdown mechanism of subgrade and slide slope induced by hidden holes in loess under the effect of dynamic load, preliminarily explored the damage formation mechanism of subgrade and slide slope with hidden holes. It has opened up new room for the further study of such geological disasters in loess area.By means of comprehensive and comparative analysis of various analytic methods, the analytic method has been deduced and established to compute hidden holes' critical thickness. To solve the problem of frequent dynamic load of vehicles on road surface, with the help of finite element numerical analysis, the paper has preliminarily studied the contribution of underlying hidden holes in loess to subgrade stability under the effect of dynamic load of vehicles, providing a necessary theoretical foundation for the study of prevention and treatment measures of hidden holes in highways.