黄土暗穴的成因及其公路工程灾害效应研究

【作者】 李喜安；

【导师】 彭建兵；

【作者基本信息】 长安大学 ， 地质工程， 2004， 博士

【摘要】 本文通过野外调研及系统总结前人研究成果，首次建立了一套系统实用的黄土暗穴分类与命名体系；对黄土高原的黄土暗穴按其发育密度进行了分区，研究总结了黄土暗穴分布的地形地貌规律、土性规律、发育深度等规律；重点针对黄土暗穴的形成条件及形成机理进行了深入研究，首次以水的作用途径、作用方式及其作用结果为主线，将黄土暗穴的形成模式概化为：冲蚀——贯通型、冲蚀——潜蚀——贯通型、湿陷——潜蚀——贯通型、冲蚀——潜蚀——湿陷——潜蚀——贯通型以及复合型模式等五大类型，在此基础上将黄土暗穴的形成演化过程分为孕育期、形成期、发展期、破坏期和消亡期等五个阶段，并发现孕育期以湿陷和潜蚀作用为主，形成期以潜蚀和冲蚀作用为主，发展期以冲蚀作用为主，破坏期以重力坍落和冲蚀为主，从而从根本上统一了关于黄土暗穴成因的观点。 针对黄土暗穴对公路工程危害十分普遍的特点，在全面总结其危害类型的基础上，对黄土暗穴的公路工程灾害及其致灾机理重点进行了研究。借助数值模拟手段，进一步分析了黄土暗穴在静载荷作用下诱发的路基以及边坡应力变化及破坏机制，并对暗穴环境下的路基与边坡的致灾机理进行了深入研究，为黄土地区的公路暗穴等地质灾害的进一步研究开辟了新的空间。 利于各种解析方法综合对比分析，推导并确定了适于计算黄土暗穴临界厚度的解析方法。针对路面经常承受车辆动荷载频繁作用的特点，借助动力有限元数值分析方法，对车辆动荷载作用下下伏黄土暗穴对路基稳定性的影响进行了初步研究，为公路黄土暗穴的防治处理措施的研究提供了必要的理论基础。更多还原

【Abstract】 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.更多还原