Risk Assessment On Debris Flow Of Tongguan Goldfield Based On The Forming Mode Of Debris Flow "7.23"

As the scientific basis of disaster reduction practice, the studies of natural disaster riskand control have been increasingly concerned by scientists, socialists and engineering experts.Due to the enormous destructive, debris flow has become one of the hot issues in bothdomestic and overseas researches of natural disasters, and also an important part of the naturaldisaster prediction and disaster prevention and reduction work. Mine debris flow is one of thespecial type which has been paid more attention onto. Currently the research focuses of minedebris flow are mostly emphasized on evaluation and control countermeasures of the regionaland local mine geological disasters and potential pitfalls of gully-debris flow. However, therehas been no study began to investigate the characteristics of the mine debris flow formation aswell as its disasters-causing mode and risk management.This work is constructed based on many projects by Xi’an Institute of Geology andMineral Resources. It analyzes a forming mode of a typical mine debris flow based on suchmethods as GIS technology, remote sensing, field investigation and field and laboratoryexperiments. Finally to optimize the model of its risk assessment can provide reference fordebris flow warning and disaster-relief and reduction work. In addition, an appropriate riskassessment methodology has been adapted to application and then to address the relevantsuggestions of regional debris flow management. The specific results are stated as followed:(1) Debris Flow “7.23” is a regional typical mine debris flow disaster. The flood peakflux of this debris flow crested to455.06m3/s, the maximum flow rate is9.61m/s and theimpact force of the debris flow peak is3.69tf/m2; The volume-weight of this debris flow iscalculated1.47g/cm3, which is a diluent water debris flow with short duration, high velocity,high flow rate. The source materials were from artificial main debris piled terrace, tail slagheap and relict deposit sediments.(2) Debris Flow “7.23” was gully-debris flow induced by instability of shallow comblandslide of strong storm in high-steep topography and geomorphology and human-sourcesmaterial accumulation. Due to the blocked of the gully ditch, it eventually leads to enlarge thedebris flow gully energy so that a total of8people deaths and5serious injuries, and tons ofproperty loss happened, which become the most serious harmful debris flow disaster during recent years.(3) According to the early methods of debris flow risk assessment,this work hascombined with regional mine debris flow material sources characteristics and formationmodes that has optimized the index of the mine debris flow and so to make the riskassessment according to the liner evaluation method. The result indicated that the potentialdamage of regional gully-debris flow is completely higher, so debris flow disaster preventionand control work has to be strengthened immediately.(4) The results of debris flow vulnerability assessment suggested that every gully of thestudy area has been highly potential damaged debris flow gully so that the damage degree oflocal people, domestic economic development and property loss suffered the debris flow wasrelatively bigger.(5) With the risk assessment of gully-debris flow, it indicated the average index ofdisaster-relief work lay in a low level, and the ability to resist the risk is weak.(6) With the consideration of carrying out more completely risk assessment work, it hasinvestigated the potential risk of debris flow and tried to adjust the traditional debris flowmode that to add the disaster-relief ability assessment into the traditional model and carry outthe new regional debris flow risk assessment mode. The results indicated only risk of northgully-debris flow of Dong Tongyu in these18gullies was higher while others were located ina medium risk level. The application of the new risk assessment model is lower than thetraditional one, which could directly reflect the expression of the active or passive resistanceagainst the debris flow hazards in the region of debris flow gully.(7) Considering the status of debris flow risk in the study area, this paper suggests thatlocal government and enterprises should start from risk reduction, risk avoidance, riskforecast and risk transformation, and take effective measures on mine debris flow riskmanagement, which included debris flow control, water conservation in source area, warningsystem, emergency system and education on disaster prevention and reduction.