Experimental and numerical analysis of secondary disasters induced by oxygen rich combustion within a tunnel

Various physical parameters, including gas concentrations (O2, CO, CH4, and H2) and temperatures at dif- ferent air velocities, were determined for full scale wood fires in the Chongqing Coal Research Institute fire test tunnel. Both experimental measurements and numerical simulations are discussed. The numer- ical analysis was performed with the computational fluid dynamics software package ''FLUENT''. The results show that the experimental data agree with the simulation results. The results verify that Roberts' theory of burning is correct. They also prove that the air velocity is the key factor that determines the type of combustion. Also, it is shown that secondary disasters are unlikely for oxygen rich combustion with a limited fire load.

Comparative study of experiment and numerical analysis of secondary disasters induced by wood fire in tunnel

Studied the changes of heat physical parameters, gas concentration of O_2, CO,CH_4 and H_2, and temperature through full scale wood fire experiments in a tunnel and simulationby FLUNET, a kind of computational fluid dynamics software.The results showthat the wood fire experiment and simulation are both oxygen-enriched combustions,which show that the simulation results coincide with the experiment.The results also provethat it is difficult for oxygen-enriched combustion to cause secondary disasters.Somesuggestions were put forward to prevent the occurrence of secondary disasters effectively.

Characteristics and Prevention of Secondary Geological Disasters of Wenchuan Earthquake

In the research, secondary geological disasters of Wenchuan earthquake were defined and the consequences were illustrated based on geological disasters, such as collapse, landslide and debris flow, and threats of barrier lakes. In addition, the characteristics of secondary disasters were analyzed, as follows： Rupture of geological faults lays foundation in terms of geological structure; loose solids provide resources of an earthquake; abundant rainfall and large runoffs are driving forces of an earthquake; rainstorm, flood, and long-term high temperature are major inducing factors. Furthermore, suggestions on prevention of secondary disasters were proposed in terms of prevention before, at and after an earthquake. Finally, the scientific and practical significances of secondary disasters were illustrated.

RS and GIS-based Statistical Analysis of Secondary Geological Disasters after the 2008 Wenchuan Earthquake

Using RS and GIS means, this article analyzes the general geological characteristics and the structural belt distribution features in Wenchuan County, Sichuan province, P.R. China as well as the characteristics of the large-scale landslides, mud-rock flows, earthquake lakes, etc., after the earthquake on May 12, 2008. Based on the above work, comprehensive indoor and outdoor research is launched on disaster distribution characteristics and their relationship with earthquakes, terrains, strata, lithology, and structures. Weights of evidence method is utilized to quantitatively analyze and evaluate the spatial distribution of secondary geological disasters after the earthquake occurred. 3 remedying grades for secondary geological disasters are derived from the results of the weights of Evidence, followed by suggestions given to remedy earthquake secondary disasters.

Risk Assessment of Secondary Geological Disasters Induced by the Yushu Earthquake

The Yushu Ms 7.1 earthquake occurred on April 14,2010 in Qinghai Province,China.It induced a mass of secondary geological disasters,such as collapses,landslides,and debris flows.Risk assessment maps are important for geological disaster prevention and mitigation,and also can serve as a guide for post-earthquake reconstruction.Firstly,a hazard assessment index system of secondary geological disasters in the earthquake region was built in this paper,which was based on detailed analysis of environmental and triggering factors closely related to geological disasters in the study area.GIS technology was utilized to extract and analyze the assessment index.Hazard assessment maps of secondary geological disasters were obtained by spatial modeling and overlaying analysis.Secondly,an analysis of the vulnerability of hazard bearing bodies in the area was conducted,important information,such as, population density,percentage of arable land, industrial and agricultural outputs per unit area were regarded as assessment indices to evaluate socioeconomic vulnerability.Thirdly,the risk level of secondary geological disasters of the area was obtained by the formula:Risk=Hazard×Vulnerability. Risk assessment maps were categorized into four levels,including"low","moderate","high"and"very high".These results show that some urban areas are at very high risk,including Jiegu,Chengwen,Xiaxiula and Sahuteng towns.This research can provide some references and suggestions to improve decisionmaking support for emergency relief and post- earthquake reconstruction in the study area.

Earthquake disaster chain model based on complex networks for urban engineering systems

According to news reports on severe earthquakes since 2008,a total of 51 cases with magnitudes of 6.0 or above were analyzed,and 14 frequently occurring secondary disasters were identified.A disaster chain model was developed using principles from complex network theory.The vulnerability and risk level of each edge in this model were calculated,and high-risk edges and disaster chains were identified.The analysis reveals that the edge“floods→building collapses”has the highest vulnerability.Implementing measures to mitigate this edge is crucial for delaying the spread of secondary disasters.The highest risk is associated with the edge“building collapses→casualties,”and increased risks are also identified for chains such as“earthquake→building collapses→casualties,”“earthquake→landslides and debris flows→dammed lakes,”and“dammed lakes→floods→building collapses.”Following an earthquake,the prompt implementation of measures is crucial to effectively disrupt these chains and minimize the damage from secondary disasters.

THE TYPHOON DISASTERS AND RELATED EFFECTS IN CHINA

China is one of the countries which were affected very seriously by tropical cyclones. In this paper, the active features of tropical cyclones which affected and landfell over China, the distinguishing characteristics of typhoon disasters and related formation laws have been studied, and the impact of trphoon disasters on China's socio-economic development have been discussed. The study reveals that typhoon disasters which affected China are characterized by high freqency in occurrence, violent in sudden occurrence, remarkable effects in China,widescope in impact and severe intensities in disasters, and this type of disaster was caused by huge gales, rainstorms, storm surges and reatal chain-disasters.Typhoon disasters have not only caused great casualties but also exerted severe effects on every economic departments in China. There is an annual increasing tendency in direct economic loss caused by taphoon disasters and since 1990, the annual average economic loss has totalled up to over lo billion RMB yuan.

Progress and Prospects of the Natural Restoration of Damaged Vegetation after the Earthquake

Vegetation plays an important role in soil and water conservation, water conservation and carbon sequestration of an ecosystem. The restoration of damaged vegetation is of great significance to the maintenance of species diversity and the restoration of the regional ecological environment. It is also one of the most effective measures to improve the fragile ecosystem. This paper summarizes the research results from decades of damaged vegetation recovery in the process of vegetation recovery, the main driving factor and the restoration mode.

Influence analysis of flow rule in mine fire during injecting inert gases

According to the action law of gas flow during injecting inert gases as the research main line, and hydromechanics and thermodynamics theories, the characteristic of gas delamination that was caused by injecting inert gases to closed fire zone was analyzed. The criterion was brought forward, which could scale disappearing probability of turbulent state. Formation mechanism of gas layer in turbulent state was discussed primarily. Simultaneously, the condition was pointed out, which could makc the gas in turbulent state by injecting different gases. The mathematical model about dynamic changes of oxygen and methane concentration in the process of injecting gases was erected. The mixture mechanism about injecting different flow inert gases and flammable gas layer in closed fire zone was revealed.

Overview of China’s Emergency Early Warning in 2021

This research uses the 59th-70th national emergency early warning information release monthly report data of China to study the total number of emergency early warnings in 2021, the general situation of early warning categories and regional distribution differences. The results show that: 1) there are 387,075 early warning information in China in 2021, and the early warning has obvious seasonality. 2) The issuance of early warnings is obviously related to the seasons, and the issuance of early warnings varies from month to month. The issuance of one kind of early warning can easily lead to the issuance of another kind of early warning, that is, the early warnings are closely related, and some specific disasters are easy to cause secondary disasters. 3) There are differences in the number of early warnings in each province. 4) The reason for the peak of early warnings in July and the large proportion of red early warnings in Henan Province is the sudden heavy rainstorm in Henan Province in July;the physical mechanism of this heavy rainstorm is sufficient water vapor, strong uplifting movement and stable situation and a long existence time.

Comparative Study of Emergency Logistics Path Planning

As natural disasters attract extensive attention worldwide,it is significant for governments and researchers to determine how to deliver emergency supplies after natural disasters.Considering the disaster victims' urgent needs for supplies after the disaster,based on the previous research,the path planning model from the shortest path and the optimal time was created in this paper.As in the actual road the outbreak of emergencies might cause some secondary disasters,including landslides triggered by heavy rain,paralysis of traffic together with a large crowd caused by earthquakes,the theory and method of the complex network to explore the topological structure characteristics of the whole network in the affected area were applied.Then,combining with the actual situation of the road network,the reliability analysis of the points,edges as well as topological structures were presented and a mathematical model based on reliability was proposed.Finally,two kinds of emergency logistics path planning models were compared and analyzed by some examples.The results showed that the relationship between time optimality and reliability was relevant.Emergency logistics path planning should not only consider the optimal transportation time of emergency logistics,but also pay attention to the reliability of transportation from a global perspective.