| Ground fissure is a geological phenomenon with ground rupture and significantdeformation. It is also a geological disaster of the Earth’s surface with direct destruction tosoil. This kind of hazard happens widely, destructively and uncommonly distributed in theregion of North China Plain, and even in the plate. With the practice of human’s engineeringactivities being expanded in natural areas, geological activity has become even more reactionto human beings, the contradiction between the two has become increasingly pronounced, aswell as the disasters. In essence, ground fissures are the phenomena of surface rupture whosefracturing factors are developing with some rules in certain media. It reflects the abruptresponse relationship between the non-continuous events of geology or engineering and thecontinuity space-time. Based on the research project “investigation and monitoring to landsubsidence and ground fissures in North China Plain”, the article probed the theory of groundfissures’ nature in order to find out the crack-acting mechanism, the crack-gestated laws, andthe crack-protected measures. This study will provide scientific basis and practical guidancefor the agricultural production, the people’s livelihood, engineering construction, andeconomic development. In this paper, the author analyzed the ground fissures in North ChinaEpicontinental Basin through the means of geological survey, exploration, surveying andmapping, monitoring, test engineering, as well as theoretical analysis, model interpretation,logical argumentation and other theoretical methods. The results of this research include sixaspects.1) The latest distribution of ground fissures in North China Plain was investigated. Itspattern is “one band and four zones”. They are Taihang-faulted band, Cangxian-swelled zone,Jizhong-depressed zone, Linqing-depressed zone, and other zones in the east of TaihangMountain fault, all of which are located in the west of Cangdong fault and the north ofYanshan Mountain Fold belt. The ground fissures have five characteristics that are directionalexpansion, concentrated distribution, associated structure, complexity formation and periodicactivities.2) The crack-gestated mechanism of ground fissures was explained comprehensivelythrough the theoretical research in North China Plain. The gestating, forming and developing of ground fissures contact with a certain time-space environment, including large-scale oneand small-scale one. In the view of microscopic point, ground fissures reflect continuityinterrupt in soil material medium, and they are damaged when the environment changes,which leads to the change of natural conditions that maintain the soil equilibrium and to themicrostructure redistribution. In the view of macro point, as a kind of geological factors, theground fissure with the factors of space, time and dynamic, forms an organic andinterconnected system of ground fissure. The formation of ground fissures is the result of itschange and evolution. In the view of gestating environmental elements, stratigraphic structureis the media factor, and geological structure is the constructed one, and modern tectonic stressand crustal movement are the power ones, and evolution of the block is the time one.3) The mechanism of ground fissures’ formation is analyzed selectively by studying thegeological facts. Due to some factors developing slowly in the long-term and changingsuddenly, the mechanical properties of soil has be weaken so much that the cracks are openedfast and widely and appear on the surface ultimately. They form the crack-opening condition,that is, the mechanisms of deep material, basement tectonics, active faults, groundwater,buried landforms, karst structure and extractive activities.4) The forming modes of ground fissures in North China are summarized for the firsttime through exploration and research. The process of the formation of ground fissuresincludes gestating, opening, developing, evolving, reposing and resurrecting. These sectorsare not always controlled by simple function, but the complex process combining the Earth’sinner power and outside one. The typical modes can be divided into the chaining reaction ofbasin margin’s fault, the lifting dislocation of fault’s block, the creeping reaction of buriedfault, the shearing function of deep structure, the responding to earthquake, aggravation bygroundwater pumping, permeating reaction of surface water, the subsidence of buriedlandforms, and the coupled function of internal and external power.5) The mass mechanism of ground fissures in North China Plain is approached throughthe regional research. At plate scale, the North China region is located in the intersection zonebetween the Eurasian Plate and the Pacific Plate, which is surround by YanshanMountain-uplift, Taihang Mountain-uplift and Taishan Mountain-uplift, and the groundfissures’ distribution reflects the characteristics of selective development in time and space. The remote effects of Qinghai-Tibet-plateau uplifting and the obstructive effects of the Pacificplate offsetting promote the mass phenomenon of ground fissures.6) The risk area of ground fissures in North Chain Plain is divided into four grades-theheight district, the middle-height district, the middle district and the low district, in which theareas in Taihang Mountain faults, Cangdong faults and the western margin faults ofJizhong-depression are the point districts of monitoring and forecasting.Finally, the theoretical value of the ground fissures is that it can help to not only explainthe facts of existing ground fissures, but also forecast the ones being unfound. This study willhelp not only deepen the scientific understanding, but also promote the engineering practice. |
PDF Full Text Request