Veracity of debris flow dangerous degree assessment is one of essential in comprehensive assessment of disaster science,and is one of the desires in socio-economic development.This paper establishes the model of debris flow dangerous degree assessment with fuzzy analytic hierarchy process method from five aspects: substance,landform,climate,geological condition and soil use,and twelve estimate factors,to evaluate eight debris flow ravines in Lianlu Hydroelectric Station assessment section of Gansu Province.The result is consistent with the actual,and it shows scientific and feasible with fuzzy analytic hierarchy process method to evaluate debris flow dangerous degree.
Gansu is one of the provinces which are severely effected by geological disasters.Through widespread collection of data and analysis on 102 catastrophic landslides and 15 catastrophic collapses happened in Gansu during 1981―2010, and in association with the geological conditions and rainfall,the distributing characteristics of collapses and landslide within 30 years in Gansu province are studied.The results show that the yearly frequency of collapses and landslides during 1981―2000 was about twice,but it appeared to be on the consecutive rising trend after 2000.In space,the disasters of collapses and landslides were mainly distributed in the central,the east and the southeast of Gansu province,especially the intensity of disasters in Lanzhou city was much higher than other areas.The mechanism of collapse and landslide are complicated,which are combination of many factors like complicated geological environment and mankind's engineering activities.The result can enhance the level of alarm and forecast of collapses and landslides disasters,and provide some constructive suggestions about prevention disasters in Gansu province.
Snow drifting is a typical disaster which blocks traffic lines in cold regions. The occurrence of snow drifting disaster is frequently influenced by topography, but the original topography is transformed to some extent owing to the construction of railway, and the wind flow field of this region thus changed, moreover, the accumulated region of drifting snow and the characteristics of its distribution changes correspondingly. Taking the DK174-184 section of Jinghe-Yining-Huocheng (JYH) railway under construction in Xinjiang for example, an AHP model has been constructed to assess snow drifting hazard along railway after considering the relation between its forming, moving and terrain, ground feature; furthermore, this model has been applied to determine the weights of assessment factors. With the support of GIS, a comprehensive assessment has been conducted. The results agree with the actual situation on the whole, and which can offer scientific references for the prevention and control of snow drifting disaster. This method also provides new ideas for the assessment of snow drifting hazard.
The soil in sliding zone is an essential part of landslides,and closely related to the evolutionary development and landslide stability evaluation.The study of sliding zone soil has been concerned recently and gradually turned to a hotspot because the study is the fundamental content of landslide in engineering geology.However,most of the study of sliding zone soil,at present,mainly has concentrated on physical and mechanical property,lacked of discussing the essential factors which affect the strength of sliding zone soil.Based on the work that have been done,in this paper,we briefly summarize the recognition and the classification of sliding zone,and the current study situation of the strength characteristics of sliding zone soil,and then emphatically give a summary and analysis according to the microstructure,mineral composition,geochemical characteristics and formation mechanism of sliding zone soil,especially the discussion of the effect of these characteristics on the strength of sliding zone soil.The study results suggest that:①the recognition of sliding zone,the classification of sliding zone soil and the analysis of the strength of sliding zone soil need to be further studied,and we ought to do some work to broaden steadily research scopes of sliding zone soil and improve the understanding of the essential factors of affecting its strength;②the research of sliding zone soil should be emphasized on the change of strength with its mineral composition,water,density,grain-size,geochemical characteristics,microorganisms,and the variation laws of microstructure under different conditions,and the effect of water-rock(soil)interaction,permeability and water chemical action on sliding zone soil;③the systematical research of sliding zone soil formation process should be based on the evolutionary viewpoint.More information about sliding zone soil landslide evolutionary progress and environment change should be sought in future.
The paper attempts to represent a case of repeated failures on a high cut slope due to multi-excavation. The characteristics of each failure induced by excavation are analyzed through geological investigation, and then a geological model at different failure stages is proposed. The geological analysis shows that the excavation-induced repeated failures are related to the exposure of the weak bedding plane and the toe unloading of the cut slope. Numerical modeling is conducted based on a sequential method, taking into account the main failure stages of cut slope. The simulation results fairly coincide with the practical phenomena observed in field. It is shown that the decrease in normal stress of displaced mass on cut slope will induce the increase in shear stress in bedding planes and that at the toe of the cut slope. The released stress leads to repeated gravitational instabilities of cut slope due to the decrease in normal stress and the increase in shear stress along the bedding planes of mudstone.
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