| Since cenozoic era, in the extrusion of the India Plate, because of the strong crustal deformation and the morphogeny of the Q inghai- Tibet Plateau, and climate also has a coupling effect on it, Geological disasters occurred frequently. The Jiawu Gold Mine is located in the Q inghai-Nanshan orogenic belt, in the western Tsaidam Basin in Q inghai- Tibet Plateau. In order to ensure that the mineral resources exploration and development runs smoothly, it is particularly important to prevent unexpected geological disasters, such as debris flow. In this paper, the debris flow in Jia wu Gold Mine is the object of study; we analyze previous research achievements, combining with the actual survey results of the debris flow hazards in the Gold Mine area, we make a summary of the different kinds of debris flow and the regularity of development and layout. O n this basis, we have the most typical and destructive debris flow in Ma-Ridang for our object of study, carry out detailed analysis and research work at the forming condition, basin characteristics, dynamic characteristics, forming process, initiation mechanism of the debris flow, and then make solutions of the Debris flow disasters. Furthermore, some suggestions of countermeasures against debris flow are proposed. The achievements and recognition we have got in this paper, as follow:1.The Jiawu Gold Mine has a large topographic relief and a large height difference, the biggest level difference is 1295 meters. The climate is typically plateau and continental climate, the average annual rainfall is 400-500 mm, concentrated in May to September, and heavy rain season is in July to September. Long service river group formation of the Middle Triassic are well-exposed in this area, structure activity is relatively strong, especially the fault structure, the main orientation is NNW and EW, neotectonism and seismic activity is stronge. The groundwater has a good discharge conditions, weathering in the surface is stronge, rock and soil mediums are loose and fractured, it has a very poor engineering properties. Human mining activities lead to a result; slag are discharged anywhere, adverse engineering geologic phenomena such as debris flow is very active.2.There are 19 debris flow geological hazard spots in the Gold Mine, based on watershed morphology, we classify them two types: slope debris flow and gully debris flow. The former is most common, there are 14 geological hazard spots of this kind in this area, the other 5 are typical gully debris flow, the dimension are different.3. The total length of the Ma-Ridang is 4.16 km, and the basin area is 6.06km2. Level difference between upstream and downstream is more than 1km, the average gradient is 192‰. The Slope Angle of the mountain is 70°, it has afavorable condition to collect surface water and Solid loose material. There are 4 kinds of loose material: including debris deposits(25.12%), Slope residual material(17.88%), Gully debris(54.88%) and Slag deposits(2.12%). The Content sources is reach to 356.833104m3, which can take part in Debris flow process. Annual rainfall concentrate in July and September, rainfall intensity is very high, it is seasonal prevalence for debris flow. This drainage area can be classified into three partitions, the formative region that sea- level elevation is between 3300~3560m, the regional circulation(2950~3300m) and accumulation area(2930~2950m). Debris flow dynamic characteristics under different design outbreak frequency values are different, including unit weight, flow velocity, discharge and impulse force, and with the growth of outbreak cycle, the unit weight and discharge will also increase, there is also a trend of growth of the scale of debris flow.4、The debris flow of Ma-Ridang ditch is a typical handling-slip type, the process of its formation is substantially along with the continuous supply source, which the scale gradually develop and grow. Basin provenance gradation result reveals that the particle size above the 0.05 mm in the source about 80% of the total, it is a typical water-stone stream or dilute debris flow. The research shows that, the velocity and density of debris flow in this basin have the following characteristics, such as: Uw≥5.35m/s;γc≤1.511 t/m3.5、The engineering measures as the main in debris flow disaster prevention scheme of Ma-Ridang ditch,including blocking, drainage and channel-slope support, etc. Biological control measures as a supplement, for example, planting conservation forest. The prevention and control of other debris flow disaster(hazard) points in the mine should follow the following principles: the governance of slope debris flow should be mainly cleaning, planting conservation forest, build ing retaining walls if necessary; the governance of ditch debris flow should mainly clean up channel, build check dam, blocking dam, drainage groove and other engineering facilities if necessary. |
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