Secondary Disasters Research Articles

System comprehensive risk assessment of urban rainstorm–induced flood-water pollution disasters

The urban rainstorm-induced flood-water pollution disaster is a kind of systematic risk, which may induce secondary disasters that can lead to more serious damage, so this paper first adopts the fuzzy comprehensive evaluation method to determine the flood risk by combining with the submergence depth derived from the risk field and other factors data, and then the grid environmental risk evaluation method, which is improved by increasing the induced possibility based on Bayesian theory, is used to evaluate the flood-induced water pollution risk, and the system comprehensive risk of rainstorm-induced flood-water pollution disasters is finally obtained by constructing risk level matrix, which can well depict the coupling superposition effect. Shenzhen City is selected as the study area, and the results showed that the area with high-risk of both flood and water pollution only accounts for about 0.14% of the total area, mainly distributed in the eastern junction of Longgang district and Pingshan district, where the rainstorms occur frequently and the enterprise risk sources are dense. The system comprehensive risk is mostly very low-low and very high-low, accounting for more than 76% of the total area. It is always necessary to pay attention not only to the areas with high risk level of both disasters, but also to the areas with high risk level of one disaster. The method proposed in this study can not only quantitatively reveal the formation of the induced risk, but also provide reference for early warning.

Study on the Influence of Earthquakes with Different Frequency Content on the Peak Liquid Sloshing Wave Height of Liquid Storage Tank

Liquid storage tank is an irreplaceable and extremely important vessel structure used to store liquid medium. In earthquake disaster, the liquid storage tank will not only be seriously damaged directly, but also cause serious secondary disasters, such as fire, explosion, poisoning, nuclear radiation, etc. The peak liquid sloshing wave height is an important reference index to judge whether the seismic design of the liquid storage tank is reasonable or not. The ratio of peak ground acceleration to peak ground velocity of the earthquake records (shown by A/V ratio) can well represent the characteristics of frequency content of earthquake records. In this paper, the finite element numerical simulation method is used to analyze the seismic response of six rectangular concrete tanks with different liquid heights, and their respective peak liquid sloshing wave heights are calculated. Nine seismic records with different A/V ratios are used, which are low frequency category, medium frequency category and high frequency category and there are three records in each category. At the same time, the equation in Eurocode 8 is used to calculate the peak liquid sloshing wave height of each tank for comparative study. The study results show that the peak liquid sloshing wave height calculated by the Eurocode 8 is greater than that calculated by the finite element method under low frequency and medium frequency earthquake records, indicating that Eurocode 8 is conducive to the preliminary design of the seismic performance of the liquid storage tank. However, in the case of high frequency earthquake records, the calculation result of the finite element method is larger than that of the equation in Eurocode 8. The peak liquid sloshing wave height of the liquid storage tank is more sensitive to the earthquakes with high frequency content, and the Eurocode 8 underestimates the impact of high frequency seismic response on the liquid storage tank.

Fluid-solid Coupling Analysis of Riser based on CFD

The riser is the only channel connecting the submarine pipeline oil gas and offshore platform structures, offshore oil and gas development and utilization of lifelines, offshore pipeline system is the weakest vulnerable link. Due to its long and thin structure, the marine riser is easy to failure and failure in the complex working conditions. Marine vibration pipe safety or not directly affects the marine engineering and the surrounding environment and marine biology, in the event of damage, can cause the economic loss and environmental pollution, will result in a casualties, and even cause serious secondary disasters. Therefore, the safety and reliability of marine riser has been the focus of marine oil and gas industry research. In order to ensure the safety and reliability of the marine riser, it is usually necessary to evaluate the safety and reliability of the marine riser. The two-way fluid-solid coupling analysis of the riser system with a water depth of 500m is carried out by Ansys workbench software. The results show that the maximum flow rate of the flow field at the interface between the fluid and the riser occurs in the middle of the riser near the two ends. As time increases, the maximum flow rate will gradually shift from both ends to the middle of the riser, and the maximum value is 0.85m/s; the maximum stress of the riser will appear at the upper and lower end points, the maximum is 81.43Mpa; the lateral displacement of the upper end of the riser reaches the maximum, about 0.69m; indicating that these positions are the vortex induced lateral vibration of the riser dangerous area; therefore, this part can be improved by structural design or protection to increase the working life of the riser.

Numerical Simulation of Assembly Process and Sealing Reliability of T-Rubber Gasket Pipe Joints

Underground pipelines are vital parts to urban water supply, gas supply, and other lifeline systems, affecting the sustainable development of cities to a great extent. The pipeline joint, which is a weak link, may be seriously damaged during natural disasters such as earthquakes. The failure of pipe joints can cause leakage accidents, resulting in system failure and interruption, and even some secondary disasters. Herein, based on uniaxial and plane tensile test results of a T-rubber gasket material, the assembly process and sealing performance of a T-rubber gasket joint of a ductile iron pipe are numerically simulated using the Ogden third-order strain energy density function to fit the material constant. The simulation accounts for severe nonlinearities, including large deformations, hyperelasticity, and complex contacts. The effects of the assembly friction coefficient, assembly depth, and radial clearance deviation of the socket and spigot on the seal contact pressure are analyzed. The results suggest that the entire history of the deformation and stress variations during assembly can be clearly visualized and accurately calculated. For the different friction coefficients, the assembly depth corresponding to the sliding friction condition of the spigot pipe was 74 mm, while the minimum pushing force required to assemble the T-rubber gasket joint of a DN300 ductile iron pipe was 6.8 kN at the ideal situation with a friction coefficient of 0. The effective contact pressure of the rubber gasket seepage surface under various operating conditions is much higher than the normal pressure of municipal pipelines, thus indicating that the rubber gasket joint exhibits the ideal sealing performance. Furthermore, a certain deviation, which is about 20 mm, is allowed for the assembly depth of the rubber gasket joint such that the axial displacement of the pipe joint can be adapted under an earthquake or ground displacement.

The Dynamic Simulation and Potential Hazards Analysis of the Yigong Landslide in Tibet, China

High-altitude and long-runout landslides, commonly forming chains of secondary disasters, frequently occur in the Yigong Zangbo Basin, which has a complex geologic background. Identifying the potential hazards posed by disaster chains plays a vital role in assessing geohazards. Analysis of the potential hazards related to a landslide that occurred on 9 April 2000, in Tibet, China, known as the Yigong landslide, is studied using remote sensing technology and numerical simulations. Due to the warming of the climate, more extreme dry–wet cycles, and frequent earthquakes, the Yigong landslide area became extremely fragile and more sensitive to perturbations. Based on multiphase optical remote sensing and InSAR (Interferometric Synthetic Aperture Radar) technology, risk monitoring and identification of the Yigong landslide was conducted. The results show that there are two displacement deformation areas. These areas have a maximum displacement deformation rate of 60 mm/year and a maximum accumulative displacement of 160 mm and are likely to reoccur. Additionally, the risks of deformation areas collapsing and blocking the river, which would likely form a disaster chain, were analyzed by prediction simulation based on the numerical back-analysis associated with the 2000 Yigong landslide. The results show that if only one displacement deformation area collapses, the maximum accumulation height would reach 76 m; if the displacement deformation areas both collapse, the maximum accumulation height would reach 106 m. Both conditions would set off disaster chains resulting in river blockages and subsequent flood disasters. Therefore, this work demonstrates that prediction analysis based on remote sensing technology and numerical simulations are effective methods for identifying potential geohazards.

Numerical investigation on mechanical behavior of door systems during seismic excitation

The opening and closing of doors in buildings likely become challenging when earthquakes occur owing to the deformation of the door frames. Although this may delay evacuation, there are no anti-seismic standards for doors defined in the Japanese Building Standards Act, which was amended in 1981. Discussions on doors or door frames from a structural point of view are still rare, even though the behaviors of doors, door frames, and hinges under seismic excitation are critical for avoiding secondary disasters after earthquakes. In this study, a seismic response analysis of a building model with door frames was performed using the adaptively shifted integration (ASI)-Gauss code to find an approach to reduce the deformation of door frames. Numerical results confirmed that the severe damage to the non-structural wall caused by the interlayer deformation of the building allowed both door frames and doors to be severely deformed. The in-plane deformation angles exceeded the angles causing difficulty in opening the doors. A door acted as an element resisting the door frame from deforming on the upper floors, and the door function would be lost on the lower floors by deforming in the out-of-plane direction. Furthermore, the overall deformations of the door frames decreased significantly even on the lower floors, where the interlayer drift angle of the building was larger, by placing the door system in a setback position. This effect was greater when the setback length was longer.

Studi Pengaruh Kejadian Hujan Terhadap Banjir Lahar Di Sungai Gendol Menggunakan SIMLAR

Indonesia is a country with the largest number of active volcanoes in the world and has the potential to erupt. This causes primary and secondary disasters, one of which is secondary disasters caused by lava floods during heavy rains. So disaster mitigation is needed by simulating lava floods to find out the predictions of speed, volume, height and area affected by lava floods. The simulation was carried out using SIMLAR software, carried out on Gendol River which is one of the watersheds that has the threat of lahar flooding. The test was carried out with 3 hyetograph patterns and for each pattern there were 3 simulations with different rainfall intensities, namely 162 mm, 243 mm and 324 mm. From these tests, the speed values ​​in patterns 1, 2 and 3 increased each simulation to the existing simulation. The speed value obtained by pattern 1 at 162 mm rain intensity is 2.35 m/s, at 243 mm rain intensity is 2.48 m/s, and at 324 mm rain intensity is 2.58 m/s. In addition, at high yields, volume and area also increase in each simulation due to the higher rainfall intensity. This proves that the intensity of rain is directly proportional to speed, volume, area and height. In addition, the hyetograph pattern also affects the peak hours when the maximum volume, maximum height and maximum speed are reached.

Disaster-Caused Power Outage Detection at Night Using VIIRS DNB Images

Rapid disaster assessment is critical for public security and rescue. As a secondary disaster of large-scale meteorological disasters, power outages cause severe outcomes and thus need to be monitored efficiently and without being costly. Power outage detection from space-borne remote sensing imagery offers a broader coverage and is more temporally sensitive than ground-based surveys are. However, it is challenging to determine the affected area accurately and quantitatively evaluate its severity. Therefore, a new method is proposed to solve the above problems by building a power outage detection model (PODM) and drawing a power outage spatial distribution map (POSDM). This paper takes the winter storm Uri, of 2021, as the meteorological disaster background and Harris County, Texas, which was seriously affected, as the research object. The proposed method utilises the cloud-free VIIRS DNB nadir and close nadir images (<60 degrees) collected during the 3 months before and 15 days after Uri. The core idea beneath the proposed method is to compare the radiance difference in the affected area before and after the disaster, and a large difference in radiance indicates the happening of power outages. The raw radiance of night light measurement is first corrected to remove lunar and atmospheric effects to improve accuracy. Then, the maximum and minimum pixels in the target area of the image are considered outliers and iteratively eliminated until the standard deviation change before and after elimination is less than 1% to finalize the outlier removals. The case study results in Harris show that the PODM detects 28% of outages (including traffic area) compared to 17% of outages (living area only) reported by ground truth data, indicating general agreement with the proposed method.

The development characteristics and mechanisms of the Xigou debris flow in the Three Gorges Reservoir Region

Debris flow is a common geological hazard in mountainous areas of China, often causing secondary disasters and seriously threatening residents and infrastructure. This paper uses the Xigou debris flow in the Three Gorges Reservoir Region (TGRR) as an example case study, the development characteristics and initiation pattern of which were analyzed based on field investigation. The disaster dynamics software DAN-W was then used to simulate the entire initiation-movement-accumulation process of the debris flow and conduct the debris flow dynamics analysis. The paper also simulated and predicted the movements of landslides in the formation area of a debris flow after its initiation. The results show that the movement duration of the Xigou debris flow was approximately 40 s, the maximum velocity was 37.1 m/s, the maximum thickness of the accumulation was 18.7 m, and the farthest movement distance was 930 m, which are consistent with the field investigation. When the volumes of landslide transformed into a new source material of debris flow are 5 × 104, 10 × 104, 15 × 104, 20 × 104, and 26 × 104 m3, the movement distances of the debris flows are 250, 280, 300, 340, and 375 m, respectively. When the volume of the source material exceeds 20 × 104 m3, debris flow movement can seriously impact the residential houses at the entrance of the gully. This paper can provide a scientific basis for the prevention and mitigation of the Xigou debris flow.

Estimation of broadband ground motion characteristics considering source parameter uncertainty and undetermined site condition in densely populated areas of Pingwu

Three destructive earthquakes occurred in Pingwu and Songpan, Sichuan Province, China, between August 16 and 23, 1976. Due to the seismic monitoring capability at that time, the ground motion characteristics of these earthquakes are very vague. Realistc and reliable strong ground motion input plays an important role in seismic building design and urban-scale earthquake damage simulation. This study reproduces the main broadband ground motion characteristics of the 1976 Ms7.2 Songpan earthquake in densely populated areas of Pingwu. The empirical Green’s function method and finite difference method are used to simulate high-frequency and low-frequency ground motion, respectively, and the broadband ground motion is obtained by superposition within the frequency range. In addition, in combination with the “Recipe” source parameter scheme, various uncertainties in the source parameters are considered, including the source mechanism, source depth, asperity parameters, etc. We obtain 36 kinds of broadband ground motion at six typical locations in the Pingwu area. Moreover, we test the rationality of the obtained broadband ground motion by ground motion prediction equations(GMPEs), and the broadband ground motions are consistent with the local ground motion characteristics. The results show broadband ground motions obtained from the scenario earthquake in this paper can meet the destructive capacity of earthquakes of this magnitude. The hybrid method can effectively compensate for the lack of long-period components of the original empirical Green function method. This research also proves that the peak ground acceleration (PGA) of ground motion is mainly contributed by high-frequency ground motion components. Long-period ground motion contributes most to the peak ground velocity (PGV), and about twice the contribution of high-frequency ground motion. Concerning the Chinese seismic intensity scale (GB/T 17742-2020) and China Seismic Ground Motion Parameter Zoning Map (GB18306-2015), the basic fortification intensity in the Pingwu area is VIII. In this paper, the seismic intensity of PWN is VI-VII, indicating that the buildings at this location are less likely to be damaged after the earthquake. The seismic intensity of other regions is VII-IX and buildings are more likely to be damaged during the earthquake at these locations. There are many mountains and valleys in the Pingwu area, and the probability of landslides, debris flows, and other disasters after an earthquake is very high, and we should give special attention to the impact of secondary disasters caused by earthquakes. It is necessary to prevent dammed lakes and other disasters caused by landslides and debris flows.

3-D Displacement Detection Based on Enhanced Clustering From GNSS Positioning in a Kinematic Mode for Deformation Monitoring

For decades, displacement detection based on global navigation satellite system (GNSS) has increasingly been an important part of deformation monitoring for applications, such as dams, bridges, and high-rise buildings. Automatic identification and extraction of 3-D displacements from GNSS kinematic positioning can provide a basis for emergency response decision-making and play a crucial role in natural and secondary disasters. However, due to the limitation of single epoch positioning accuracy, automatic detection of displacement from GNSS kinematic positioning results is still a challenge. To resolve this, we propose an enhanced <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> -means clustering method to detect displacements from GNSS kinematic positioning, which identifies the displacement by clustering and obtains displacements from adjacent clusters. Results from simulation and field experiments have demonstrated the effectiveness of the proposed method. The accuracy of 3-D displacement extraction from GNSS real-time kinematic (RTK) positioning can reach millimeter level.

Impact and Inspiration of Tonga volcanic Eruption in 2022

People have been puzzled by the problem of volcanic eruptions since ancient times. Because volcanic eruptions are difficult to predict accurately, if people can't take some precautions in advance, sometimes volcanic eruptions will cause great injuries and deaths and hazards. In this context, this review selects the Tonga Volcano as the research object, summarizes the hazards during the eruption of the volcano and the symptom before the eruption, in order to get inspiration for predicting volcanic eruptions. This paper firstly introduces that Tonga volcano is located on the Tonga-Kermadec volcanic arc. When Tonga volcano erupted, it tended to an explosive eruption, which Surtseyan eruption dominated. Secondly, the author analyzes the impact on the capital of Tonga, the surrounding area and the world through the primary disaster, such as the collapse of crater, volcanic ash and SO2. Then, the global impact of secondary disasters after primary disasters is analyzed, such as tsunami and climate change. Thirdly, the author concludes the pre-eruption symptoms, such as surface deformation and ionospheric anomaly. The observation of these anomalies and the establishment of a volcano monitoring system will help people to predict the next volcanic eruption. In addition, it remains to be seen how to detect the symptoms of volcanic eruption in time. Finally, this paper emphasizes that there are few practical applications of volcano monitoring system, and more volcanoes need to be monitored in time. If volcano monitoring systems were made more common around the world, people could minimize the damage caused by volcanoes.

Bidirectional Coupling Analysis of Support Pipeline for Shock Damping of Dilute Debris Flow

With the frequent occurrence of geological disasters and extreme weather, pipeline failure accidents and secondary disasters caused by debris flow continue to occur. Aiming at the impact of thin debris flow on support pipeline, a multi-physical coupling model of debris flow and support pipeline with vibration reduction is established based on the expansion flow model. The expansive fluid model is used to simulate the stress of the support pipeline under the action of thin debris flow. The results show that the impact effect of thin debris flow slurry on the support pipeline is concentrated at the inlet surface of the pipeline and the support, and gradually decreases to both ends. As the velocity of debris flow slurry increases, the stress acting on the support pipeline also increases. When the flow field tends to be stable, the load acting on the support pipeline maintains a stable value. The leading effect of debris flow slurry is the most serious damage to the support pipeline. The research results have a certain reference value for the impact of dilute debris flow in support pipeline.

A spring-like interface between saturated frozen soil and circular tunnel lining under the moving load in cold regions without considering frost heave

The vibration of underground or buried piping during construction and long-term operation causes secondary disasters, and becomes more complex when tubes are buried in cold regions. The interface between saturated frozen soil and lining is regarded as a thin spring-like layer whose thickness could be negligible. In this paper, the dynamic response of saturated frozen soil is studied in frequency domain by using the Helmholtz composition and Fourier transform to obtain analytical solutions of the radial and axial displacement, as well as expressions of the stiffness coefficient (Kr) and damping coefficient (Cr) of the spring-like interface. Numerical results indicate that Kr and Cr are related to physical properties of the lining and its surrounding soil, and the coefficients of the spring-like model could be changed by adjusting lining parameters to improve structure stability under the same load conditions. Also, the viscoelastic contact surface of the spring-like model is considered to have less effect on the surrounding soil than that when the lining has complete contact with the soil under load. The degree of soil freezing significantly affects the axial and radial displacement of the soil when the interface between lining and unsaturated frozen soil is taken into consideration.

A novel urban seismic resilience assessment method considering the weighting of post-earthquake loss and recovery time

Earthquakes impose substantial threats to the built environment of urban communities. To reduce the catastrophic consequences of earthquakes, there is an urgent need to build seismic resilient cites that can better resist seismic damage and enable a rapid post-disaster recovery. This paper gives the definition of urban seismic resilience, and establishes a seismic resilience assessment indicator system for urban built environment that integrates engineering systems, non-engineering systems and secondary disaster risk. A novel urban seismic resilience assessment method based on post-earthquake loss and recovery time is then developed to assess engineering system seismic resilience. Post-earthquake loss is divided into casualties and functionality loss. Adjustment coefficients are applied to account for the effects of non-engineering systems and secondary disaster risks on urban seismic resilience. The analytical hierarchy process is employed to calculate the weights of individual engineering systems. In the end, a city located in southern China is taken as an example to illustrate the proposed method. The assessment results suggest that the urban seismic resilience grade is Ⅱ, which means that the city can effectively resist possible future earthquake disasters.

Influence of Extreme Weather and Its Secondary Disasters on Bridges

Global climate change causes more and more extreme weather happened frequently. It poses a new challenge to the structural safety of civil engineering. Nowadays, bridge engineering designs must consider the possibility of extreme climates and the social, economic, and environmental damage they cause. In this paper, the influence of three kinds of extreme weather on bridges is summarized by the method of comprehensive narration, and the influence of secondary disasters is described. Results show that both extreme weather and secondary disasters can significantly impact bridges. Extreme weather includes rainstorms, typhoons and earthquakes and affects the structure and materials of the bridge. Heavy rain erodes the bridge's structure and material and causes flood and debris flow to harm the bridge. Flood water would continue to impact the pier and cause damage to the understructure of the bridge. Meanwhile, they could also induce secondary disasters such as aftershocks and debris flow, impacting the bridges and disrupting the function of the city.

Temperature field simulation and collapse analysis of steel frame factory under fire

Building collapse is fire-induced secondary disasters. Because of many combustibles, fire-induced collapse accidents occur frequently in the steel frame factory. It causes the economic property and firemen casualties. So this paper carries out the temperature field simulation and collapse analysis of the steel frame factory under fire. The analysis module of ABAQUS is used for simulation in this paper. By comparing room temperature with high temperature, the Mises stress nephogram and displacement nephogram of the steel frame factory are analyzed. It is found that the beams and columns are greatly deformed under fire, especially the steel beams of the bent frame. The local plastic damage is occurred in the fire area of the frame, which may lead to the danger of local collapse. On the other hand, the stress of the column and beam is studied under high temperature. It shows that the stress of them increases first and then decreases.

Toward Interoperable Multi-hazard Modeling: A Disaster Management System for Disaster Model Service Chain

A natural hazard-related disaster event often causes a series of secondary disasters, forming a disaster chain. Modeling the evolution of disaster chains in multi-hazard scenarios is crucial for risk governance and urban resilience. However, existing multi-hazard models are limited by complex model design and fixed disaster types, making it impossible to ensure flexible reactions to complex and diverse scenarios. This study presents a disaster management system for disaster model service chain (DMSC) to implement interoperable multi-hazard modeling. To achieve efficient model interaction in the DMSC, a management module is designed to normalize heterogeneous single-hazard models based on disaster system theory and the Open Geospatial Consortium standards, enabling them to be accessible, reusable, and interoperable. The normalized models are then adaptively orchestrated through an orchestration module to establish optimal executable DMSCs for different multi-hazard scenarios. Taking an earthquake disaster chain as a case study, we demonstrate that the disaster management system shows stable and flexible performance for multi-hazard modeling.

Conserving the unique aquatic ecosystem of the Jiuzhai National Heritage Site after the 2017 earthquake: Achievements and challenges

Water resources are the key link within the unique landscape of the Jiuzhaigou World Natural Heritage Site. However, the earthquake on 8 August 2017 induced serious damage to the ecosystem of the Jiuzhaigou region. Water resource quantity was threatened by the direct destruction of the connectivity between the upstream and downstream river systems, whereas water quality and the original aquatic ecosystem were worsened indirectly by secondary disasters, such as landslides and debris flows triggered by earthquakes. It is urgent to protect water resources to maintain a healthy aquatic ecosystem for the Jiuzhaigou World Natural Heritage Site. Therefore, water resource protection strategies are developed by collaboratively considering water quantity, quality and aquatic ecology, including 1) studying the relationship between upstream and downstream in terms of water supply and connectivity, 2) developing emergency plans for extreme precipitation disasters and ecological water regulation schemes for extreme drought, 3) clarifying the impact of vegetation management measures on water conservation, nutrient cycling and water quality, 4) separating the contributions of earthquakes from related disasters, hydrodynamic changes, and lake bank vegetation succession to lake swamping, 5) identifying the potential water pollution risk caused by ecological restoration projects, analyzing the sources of pollutants such as nitrogen, phosphorus and atmospheric acid deposits and developing control measures, and 6) systematically evaluating aquatic ecological health and determining water ecological protection and restoration measures. This review may provide critical viewpoints for conserving aquatic ecosystems, not only in the Jiuzhai World Natural Heritage Site but also in other global conserved aquatic parks.

Quality of healthcare and admission rates for acute cardiac events during COVID-19 pandemic: a retrospective cohort study on ST-segment-elevation myocardial infarction in China

ObjectiveTo evaluate changes in admission rates for and quality of healthcare of ST-segment-elevation myocardial infarction (STEMI) during the period of the COVID-19 outbreak and postoutbreak.MethodsWe conducted a retrospective study among...