云冈石窟危岩发育的成因分析

摘要

云冈石窟发育危岩,在国内砂岩石窟中具有代表性;对云冈石窟危岩发育的成因分析,可指导砂岩类石窟危岩的防治.采用工程地质的研究方法,从内在环境条件和外在环境条件两个层面,对云冈石窟区域危岩的发育条件进行系统分析.箱形向斜和断裂是云冈石窟区域危岩发育的宏观构造成因,近东西向的张裂隙和北东向剪切裂隙直接控制石窟区域内危岩的发育.石窟陡崖的高差直接控制岩坡卸荷带的发育规模,也决定着危岩体的致灾能量.软硬相间的岩层差异风化形成陡崖和岩腔,构成危岩体形态.裂隙水及降雨直接影响岩体稳定性.冻融、温差、干湿交替长期作用于岩体,导致危岩体稳定性不断劣化.人工开凿洞窟破坏崖壁应力状态,是危岩失稳的影响因素.云冈石窟危岩体成因分析结果为指导危岩体防治提供了重要依据,对危岩体稳定性分析具有重要意义.%Perilous rock is one of the main geological hazards in sandstone grottoes, especially in Yungang Grottoes. The study on causes for perilous rocks is useful for prevention and cure of perilous rocks in sandstone caves. In this paper, the various influence factors of perilous rocks were analyzed in detail by engineering geology method. Box-like synclines and fractures were macroscopic tectonic origins of perilous rocks. The near E-W tensile cracks and N-E shear fissures directly controlled the perilous rocks' evolution. The differences in height between cliffs directly controlled the development scale of the unloading zone of slopes, and determined the hazard energy of perilous rocks, and the differences in weathering of soft-hard alternate multilayers generated cliffs and cavity to form perilous rock's shape. Fissure waters and rainfalls directly affected the stability of perilous rocks. The stability of perilous rocks which had undergone long-term effects of freezing-and-thawing, temperature differences and alternate drying-watering continued to be deteriorated, and engineering activities are the main triggering cause of the perilous rocks' instability. The result provides an important basis for prevention and cure of perilous rock masses, and is valuable to analyze the stability of Yungang Grottoes.