Secondary Geological Disasters Research Articles

Simulation of landslide dam failure due to overtopping considering wide-graded soil erosion

Landslide dams, as a particular type of secondary geological disaster, can cause serious flood disasters. Therefore, accurately predicting potential dam failure processes is crucial for developing reasonable emergency response plans. Currently, several landslide dam failure models have been proposed, but most of these models do not appropriately consider the wide gradation of landslide dam materials, which is essential for accurate erosion calculations. Therefore, this research proposes a relative exposure formula under three-dimensional conditions to account for the concealment and exposure effects between large and small particles in wide-graded soil. Based on this, the incipient velocity of wide-graded soil is derived, and a mathematical model of overtopping failure of landslide dams is established. As part of the model, a numerical solution process is also developed to ensure convergence. To evaluate the performance of this new mathematical model, the discharge process of Tangjiashan landslide dam was used as a real-world case for dam failure calculation. The calculated results of key dam failure outcomes were compared with actual measurements, showing that the results of this model are largely consistent with actual measurements, with the error controlled within 10%. Additionally, the mathematical model proposed in this article was compared with two other existing dam failure models, revealing that the model proposed here has advantages in controlling the error of key dam failure outcomes, mainly due to the comprehensive consideration of erosion calculation in wide-graded soil. To further evaluate the stability of the model, the breach processes of the “11.3” Baige landslide dam and the Yigong landslide dam were also calculated, and the results showed reasonable consistency. Based on the model presented in this article, the influence of the grading width of landslide dam materials on key dam failure outcomes was discussed. It was found that grading width significantly affects the development process of breach flow. Specifically, wider grading width leads to smaller peak values of breach flow and later peak times. Additionally, the final size of the breach is affected by grading width, as it has a significant impact on erosion strength, although the sensitivity of this parameter is relatively weak. Given the significant impact of grading width on the dam failure process, especially for landslide dams containing wide-graded soil, it is essential to fully consider the wide grading of materials for accurate dam failure calculations.

Effects of grassland vegetation roots on soil infiltration rate in Xiazangtan super large scale landslide distribution area in the upper reaches of the Yellow River, China

In order to study the infiltration characteristics of grassland soil in the super large scale landslides distribution area in the upper reaches of the Yellow River, this study selected the Xiazangtan super large scale distribution area in Jianzha County as the study area. Through experiments and numerical simulations, plant roots characteristics, soil physical properties and infiltration characteristics of naturally grazed grassland and enclosed grassland with different slope directions were compared and analyzed, and the influence of rainfall on seepage field and stability of the two grassland slopes were discussed. The results show that the highest soil moisture infiltration capacity (FIR) is found on the shady slope of the enclosed grassland (2.25), followed by the sunny slope of the enclosed grassland (1.23) and the shady slope of the naturally grazed grassland (−0.87). Correlation analysis show that soil water content, root dry weight density, total soil porosity, number of forks and root length are positively correlated with infiltration rate (P＜0.05), whereas soil dry density is negatively correlated with infiltration rate (P＜0.05). The results of stepwise regression analyses show that soil water content, total soil porosity, root length and number of forks are the main factors affecting soil infiltration capacity. And the ability of roots to increase soil infiltration by improving soil properties is higher than the effect of roots itself. After 60 min of simulated rainfall, the safety factors of the shady slopes of naturally grazed grassland and enclosed grassland are reduced by 29.56% and 19.63%, respectively, comparing to those before rainfall. Therefore, in this study, the roots play a crucial role in regulating soil infiltration and enhance slope stability by increasing soil water content, soil total porosity and shear strength while decreasing soil dry density. The results of this study provide theoretical evidence and practical guidance for the effective prevention and control of secondary geological disasters such as soil erosion and shallow landslide on the slope of river banks in the study area by using plant ecological measures.

FS_YOLOv8: A Deep Learning Network for Ground Fissures Instance Segmentation in UAV Images of the Coal Mining Area

Abstract. The ground fissures caused by coal mining have seriously affected the ecological environment of the land. Timely and accurate identification and landfill treatment of ground fissures can avoid secondary geological disasters in coal mine areas. At present, the fissure identification methods based on deep learning show excellent performance on roads and walls, etc. Nevertheless, the automatic and reliable segmentation of ground fissures in remote sensing images poses a challenge for deep learning networks, due to the diverse and complex texture information included in the mining ground fissures and background. To overcome these challenges, we propose an improved YOLOv8 instance segmentation network to automatically and efficiently segment the ground fissures in coal mining areas. In detail, a model called FS_YOLOv8 is proposed. The DSPP (Dynamic Snake convolutional Pyramid Pooling) module is incorporated into the FS_YOLOv8 model to establish a multi-scale dynamic snake convolution feature aggregation structure. This module replaces the conventional convolution found in the SPPF module of YOLOv8 and aims to enhance the model's ability to extract features related to fissures with tubular structures. Furthermore, the D-LKA (Deformable Large Kernel Attention) module is employed to autonomously collect fissure context information. To enhance the detection capability of challenging samples in remote sensing images with intricate background and fissure texture, we employ a Slide Loss function. Ultimately, the ground fissure dataset of unmanned aerial vehicle (UAV) images in coal mine areas is subjected to experimental analysis. The experimental findings demonstrate that FS_YOLOv8 exhibits exceptional proficiency in segmenting ground fissures within intricate and expansive mining areas.

Enhancing post-seismic landslide susceptibility modeling in China through a time-variant approach: a spatio-temporal analysis

ABSTRACTThe pre-phase landslides will have a legacy effect on future landslides, changing the landslide susceptibility. This study attempts to establish a reasonable post-seismic landslide susceptibility model and analyze the spatio-temporal characteristics of landslide susceptibility in the Jiuzhaigou MS7.0 earthquake-struck region. Firstly, an integrated ‘space-ground’ monitoring technology is used to establish a multi-temporal post-seismic landslide dataset. Then, the buffer analysis method documents the spatio-temporal characteristics of post-seismic landslides. Thirdly, the distance is selected as an indicator to quantify the legacy effect. An improved time-variant model is established to evaluate the post-seismic landslide susceptibility. Finally, the spatio-temporal characteristics of landslide susceptibility are generalized, to sum up the changing law. Our results show that the post-seismic landslides are gradually closer to the pre-phase landslides with time. Distance is a critical factor in measuring the impact of pre-phase landslides on future landslides, which can improve the assessment accuracy of the post-seismic landslide susceptibility model. After a large seismic event, the correlation between landslide susceptibility and earthquakes gradually weakens. Post-seismic landslide prevention should focus on the pre-phase landslide expansion triggered by rainfall. Moreover, it should clean up the landslide deposits in time and reasonably dredge the debris flows to avoid secondary geological disasters.

Experimental study on slope morphological characteristics and stability analysis of GCHP engineering in the loess plateau

Construction gully slope to terrace (STT) is one of soil and water conservation measure in Gully Consolidation and Highland Protection (GCHP) Project. If the design is unreasonable, not only can’t play its due role, but even more severe soil erosion will occur. In order to quantify the relationship between drainage system of STT and soil erosion, this paper took Fengbao gully head in Dongzhi Plateau as a prototype, and analyzed the hydraulic erosion process of gully head with and without drainage system. Based on the actual precipitation in the area where the prototype is located, three groups of slopes (scenario 1 is an untreated slope, scenario 2 is only STT treatment, and scenario 3 is a STT with a relatively complete drainage system). A series of scouring experiments (flow rates of 0.43, 0.32, 0.86, 1.62, 1.24 and 0.32 m3/h) were carried out on the physical model. The results show that secondary geological disasters such as landslides and diarrhea are more likely to occur on the STT without drainage system than on the untreated slope. Having a relatively perfect drainage system can reduce the sediment concentration to a great extent. The sediment concentration produced by each scouring experiment in scenario 1 is 270.27%, 1018.63%, 479.21%, 250.38%, 556.78% and 151.18% higher than that in scenario 3, respectively. The sediment concentration produced by each scouring experiment in scenario 2 is 486.03%, 1625.21%, 536.96%, 959.29%, 158.94% and 316.67% higher than that in scenario 3, respectively. The sediment concentration fluctuated continuously with time, with multiple peaks and valleys. It is considered that the first few years of construction, if the slope surface after leveling is still exposed, the drainage pipe is suspended to drain and collect water, and the pipeline mouth is directly washed away, which may cause more serious erosion. This study can provide a scientific basis for soil and water conservation and ecological environment construction in the Loess Plateau and the health management of the GCHP Project.

Impacts of Different Gully Consolidation and Highland Protection Models on the Runoff and Sediment Yield in Small Watershed of the Chinese Loess Plateau—A Case Study of Fengbugou in Qingyang City of Gansu

The Gully Consolidation and Highland Protection (GCHP) project is crucial in preventing gully erosion in the Loess Plateau. However, there are new problems after the completion of the GCHP project, such as secondary disasters caused by sudden changes in water flow paths. To study the impact of different GCHP measures on runoff and sediment production, we conducted a series of scouring experiments using the similarity principle, taking Fengbao Gully, Xifeng District, Qingyang City, Gansu Province, as a prototype. Moreover, three scenarios in the GCHP project (landfill (LT), nondrained terraced (NDT), and terrace with a drainage system (DT)) are established. Seasonal rainfall simulation experiments are conducted with a constant slope. The results showed that during summer rainfall, the 10 min runoff depth of LT is 67.83~276.03% higher than that of NDT. However, in spring and autumn, the runoff depth of NDT is 4.12~39.84% higher than LT’s. The sediment yield of LT is 0.06–5.58 times higher than that of NDT and 1.91–25.58 times higher than that of DT. The sediment yield of NDT is 0.46–4.02 times higher than that of LT and 2.27–23.93 times higher than that of DT, indicating that, under the same conditions, the effect of slope replacement with terraces for GCHP is better than that of gully head landfill in reducing soil erosion and secondary geological disasters. Furthermore, imperfect terrace construction can result in increased sediment yield. This study provides a scientific basis for the maintenance and later management of GCHP and helps implement soil and water conservation measures in similar regions worldwide.

Risk Assessment of Earthquake–Landslide Hazard Chain Based on CF-SVM and Newmark Model—Using Changbai Mountain as an Example

Changbai Mountain is an important part of the development and opening pilot area of Changjitu. It is the birthplace of Songhua River, Yalu River, and Tumen River, and is known as the source of the three rivers. Millions of people live in the basin. A volcanic eruption accompanied by earthquakes would lead to a large number of landslides, debris flows, and show a chain effect, the formation of a secondary geological disaster chain, which is a serious threat to people’s lives and property safety. This paper selected indexes from three aspects: the hazard of earthquake-induced geological disaster chain, the exposure and vulnerability of disaster-bearing bodies, and the risk assessment of earthquake-induced geological disaster chain. The sensitivity values of each influence factor were calculated by the certainty factor (CF) using the support vector machine, and then, the susceptibility assessment was obtained. The cumulative displacement calculated by the Newmark model represented the potential risk intensity. We considered the Changbai Mountain volcanic earthquake–landslide disaster chain as an example. The results of risk assessment showed that the extremely high and high risk areas were mainly located within the 12 km radius of Tianchi Lake, and the other areas in the study area were mainly associated with very low to low risk values. The verification results showed that the receiver operating characteristic (ROC) curve area was 0.8373, indicating that the method was very effective in the identification and assessment of seismic hazard chain risk. In these high-risk areas, relevant countermeasures should be formulated to prevent the risk of geological disasters, strengthen the implementation of regional disaster prevention and reduction work, and ensure the safety of residents’ lives and property.

Preliminary results on a near-real-time rock slope damage monitoring system based on relative velocity changes following the September 5, 2022 MS 6.8 Luding, China earthquake

Relative seismic velocity change (dv/v) is important for monitoring changes in subsurface material properties and evaluating earthquake-induced rock slope damage in a geological disaster-prone region. In this paper, we present a rapid damage assessment on three slow-moving rock slopes by measuring dv/v decrease caused by the 2022 ​MS 6.8 Luding earthquake in Southwest China. By applying the stretching method to the cross-correlated seismic wavefields between sensors installed on each slope, we obtain earthquake-induced dv/v decreases of ∼2.1%, ∼0.5%, and ∼0.2% on three slopes at distances ranging from ∼86 to ∼370 ​km to the epicenter, respectively. Moreover, based on seismic data recorded by 16 sensors deployed on the rock slope at a distance of ∼370 ​km away from the epicenter, a localized dv/v decease region was observed at the crest of the slope by calculating the spatial dv/v images before and after the earthquake. We also derive an empirical in situ stress sensitivity of −7.29✕10−8/Pa by relating the dv/v change to the measured peak dynamic stresses. Our results indicate that a rapid dv/v assessment not only can help facilitate on-site emergency response to earthquake-induced secondary geological disasters but also can provide a better understanding of the subsurface geological risks under diverse seismic loadings.

Remote Sensing Land Use Evolution in Earthquake-Stricken Regions of Wenchuan County, China

Earthquakes and their secondary geological disasters have a certain impact on the land cover, which leads to the degradation of the ecological environment and the stability of the ecosystem. At present, there are few studies on the spatial–temporal evolution characteristics of land-use change in earthquake-stricken regions, especially the lack of quantitative evaluation of the impact of earthquakes on land use at the micro-scale. The “5·12” Wenchuan ms8.0 earthquake caused serious damage to the surface resources in the disaster area. The study on the spatial–temporal evolution characteristics of land-use change in the disaster area can provide a reference for the remote sensing dynamic monitoring of the ecological environment. Therefore, based on geographical big data, this paper used a land-use comprehensive degree index, land-use transfer matrix, and landscape ecological index to explore and analyze the spatial–temporal evolution characteristics of land use in Wenchuan County before and after the earthquake. The results showed that the types of cropland, forest, built-up, and bare land changed greatly before and after the earthquake. During the earthquake recovery period, the comprehensive index of land use in the study area basically showed an increasing trend. Under the effect of artificial measures and natural restoration, land use was continuously improved, and vegetation was restored well. After 2008, the Patch Density (PD) and Landscape Shape Index (LSI) values of most landscape types decreased, and the Aggregation Index (AI) values increased, indicating that the ecological environment of the whole region showed a benign development in the post-earthquake period. The results not only contribute to the establishment of scientific ecological environment management in earthquake-stricken regions but also contribute to the formulation of long-term ecological environment monitoring and ecological restoration planning according to the law of land-use change.

To stay or to move? Investigation on residents' migration intention under frequent secondary disasters in Wenchuan earthquake-stricken area.

The deterioration of the living environment caused by the earthquake is the main migration motivation of residents in the area of the secondary earthquake disaster, and their migration intention is one of the most important factors affecting residents' happiness. This paper uses 957 effective survey samples from 12 secondary geological disaster areas after the Wenchuan earthquake to research the migration intention of residents and its influencing factors. It can be found that 45.2% of residents are willing to migrate, which means they have an instinctive reaction to profit-seeking and harm-avoiding, but it has not become a realistic choice. Investigation facts and research results show that the instinctive response of profit-seeking and harm-avoiding drives residents to make different choices. The migration of residents in areas where secondary geological disasters occur is affected not only by disasters such as debris flow, landslides, and collapse, but also by many factors such as life convenience, family income, expectations for future life, gender, education level, psychological feeling. The improved life and the optimization of the economic conditions brought about by the success of post-disaster reconstruction have made the vast majority of people more confident in the future of the disaster-stricken areas, which made most people choose to stay in those areas. This paper will provide policy suggestions for residents' migration and the reconstruction of the local social governance system in secondary geological disaster areas, which is helpful to improve ecological livability and residents' happiness in the Wenchuan earthquake-stricken area.

Study on the Ground Fissure Development Law of Coal Mining Based on UAV Photogrammetry and the Particle Flow Theory

Ground fissures caused by underground coal seam mining easily result in secondary geological disasters and destroy the ecological environment, which seriously impacts the production and life of mining areas and residents. The traditional monitoring methods, such as manual measurement and satellite monitoring, have their disadvantages. Therefore, it is urgent to develop a large-scale monitoring technology for ground fissures and study its development law. In this article, we analyzed the distribution characteristics of ground fissures based on the low-altitude UAV remote sensing images and combined them with field investigation as validation. Moreover, we introduced the particle flow theory to study the development law and formation mechanism of ground fissures. This article takes the 8092 working face of a mine in Ordos City as the study area. The results showed that the accuracy rate of ground fissures based on the visual interpretation of UAV images was 95%. The ground fissures were mainly distributed near the stopping line and the groove of the working face. The plane forms of ground fissures were mainly two types: the linear type and arc type, and the location relationship can be divided into the parallel type and bifurcation type. The types of ground fissures were the tensile type and step type. Whether the upper and lower parts of the key strata were broken simultaneously is the root cause of tensile ground fissures and step ground fissures. The stability of the overlying strata had a significant influence on the change of abutment pressure above the goaf. The process of surface movement and deformation can be divided into three stages: tensile failure of the slope bottom, traction failure of the slope body, and sliding failure of the slope top. In addition, the zero point of the surface horizontal movement value and the maximum surface subsidence were not in the center of the goaf. Due to the horizontal slip of the downhill direction in the horizontal movement on the surface, the value of the downhill direction subsidence was zero. However, the value of the horizontal movement was not zero, and there was even a large horizontal movement. In conclusion, the research results can provide a useful reference for the rapid monitoring of large-scale geological disasters caused by underground coal seam mining and the application of the particle flow theory.

Dynamic monitoring and analysis of the earthquake Worst-hit area based on remote sensing

The earthquake and its secondary geological disasters have some long-term effects on vegetation recovery, and the spatiotemporal differentiation of vegetation coverage in earthquake-stricken areas are often not valued by researchers. Beichuan County in Sichuan Province is the worst-hit area during Wenchuan earthquake, tracking the vegetation coverage in this disaster area can provide feedback for post-earthquake ecological restoration. Based on remote sensing (RS) and Geographic information system (GIS), this paper relies on dimidiate pixel model (DPM) and vegetation coverage transfer matrix to explore the vegetation coverage of the earthquake worst-hit area. The results show that the overall level of vegetation coverage in Beichuan county is high, and earthquakes are dominant in the areas with high vegetation coverage. Besides, earthquake can do most severe damages to the areas with high vegetation coverage, followed by medium damage impacting to the areas with medium vegetation coverage, but the damage of other areas are relatively small. From 2007 to 2020, the average vegetation coverage in Beichuan County decreased from 0.835 in 2007 to 0.755 in 2008, then gradually recovered to 0.826 in 2020, experiencing a sharp decline and then a steady increase. The recovery of vegetation coverage is improved over time, but the spatiotemporal differences of the recovery process are obvious. Elevation has the largest driving force on vegetation coverage (q = 0.569, p less than 0.001), followed by temperature and rainfall; the interaction between factors has a significant increasement in the spatial differentiation of vegetation coverage, indicating that vegetation coverage is a combination result of multiple factors. The research findings can help construct the scientific management of the eco-environment in the disaster area, it can also help builda medium to long-term ecological restoration plan according to the variation in vegetation coverage.

Research on Intelligent Evaluation Model of Railway Internationalized Earthquake Emergency Rescue Talents Based on Analytic Hierarchy Process and Fuzzy Theory

Earthquakes occur frequently in the 21st century and cause a large number of casualties; induced secondary geological disasters will cause more serious casualties. How to reasonably deal with the earthquake disaster to carry out emergency rescue work is becoming increasingly urgent; the ability level of earthquake disaster emergency rescue personnel is directly related to the follow-up relief effect. Based on this, aiming at the emergency rescue ability of nationalized railway management talents in high-intensity earthquake areas around the world, this paper will use the methods of analytic hierarchy process and fuzzy theory to construct an intelligent evaluation model of railway international earthquake emergency rescue personnel ability. In addition, this paper carries out a questionnaire survey of experts in related fields and model empirical research and puts forward optimization measures and suggestions for the personnel training of railway international earthquake emergency rescue in high-intensity seismic areas based on the results of model evaluation.

Risk assessment on the CCUS project using risk breakdown structure methodology: A case study on Jilin oilfield CO2‐EOR Hei‐79 block

AbstractThe risk potential matrix method can be used as a reference for the optimization of the traditional risk matrix in geological CO2 storage. This study used monitoring data for environmentally sensitive receptors in the Jilin Oilfield CO2‐enhanced oil recovery (CO2‐EOR) Hei‐79 block in conjunction with a hazard event store to create an updated risk assessment of CO2 capture, use, and storage (CCUS) as a guide for risk management. The assessment built upon the overall project operation status to evaluate six and five sub‐categories of hazard and sensitivity, respectively. The environmental sensitivity threshold integrated ecosystems and secondary geological disasters to amplify potential risks. The results of the risk assessment of the CO2‐EOR Hei‐79 block in the Jilin Oilfield showed that despite an overall risk level of Ⅱ, the hazard level resulted in an unacceptable increase in overall risk. Formations are usually stimulated by fracturing in Jilin Oilfield, particularly for oil and gas production. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd.

Livelihood Adaptation of Rural Households under Livelihood Stress: Evidence from Sichuan Province, China

The welfare of many poor and low-income rural households is vulnerable to earthquakes and secondary geological disasters. The academic literature, however, pays little attention to the livelihood pressure, adaptability, and livelihood strategies of these households. Based on the survey data of 327 rural households in the Wenchuan and Lushan earthquake-stricken areas in the Sichuan Province, the livelihood pressure, adaptability, and livelihood strategy characteristics of rural households were analyzed, and the disordered multi-classification logistic regression model was constructed to explore the correlation between the above-mentioned variables. The results show that: (1) Rural households face the greatest economic pressure and the least social pressure; rural households have the strongest adaptability in social capital and the lowest adaptability in financial capital. The proportion of rural households that chose the aid livelihood strategy was the highest, while the proportion of rural households that chose the adjustment livelihood strategy was the lowest. (2) Compared with the expanded livelihood strategy, (a) When the health pressure is higher, the rural households are more inclined to choose the expanded livelihood strategy, followed by the contractive livelihood strategy and, finally, the aid livelihood strategies; (b), the higher the physical capital, the more often the rural households tend to choose the expanded livelihood strategy compared to the adjustment livelihood strategy; (c), The higher the financial capital of farm households, the more they prefer contractive livelihood strategies compared to the expanded livelihood strategy and (d), compared with the aid livelihood strategy, rural households with greater economic pressure are more inclined to choose the expanded livelihood strategy.This study can provide a reference for the establishment of relevant policies related to the adaptation capacity of rural households in the earthquake hazard zone.

Disaster risk management models for rural relocation communities of mountainous southwestern China under the stress of geological disasters

Southwestern mountainous China is a vast, underdeveloped ethnic minority area with frequent geological disasters caused widespread poverty and therefore the inability to resist them, and relocation is one of the important measures targeted to geological disaster prevention and poverty alleviation there. We argue that it is crucial to explore effective management models for rural communities relocated in the context of disaster risk management (DRM). We identify two dominating types of relocation communities (the characteristic tourism type and the urbanization type) and changes in livelihood assets and strategies and in ecological-living-industrial land spaces of the two types, and discuss the common and different traits of two types of DRM models and the effects on village residents’ livelihood regarding mudslide risk management in Changde Village and unstable landslide risk management in Dabashan Village, then further research deficiencies of the models and countermeasures in policy and institutional dimensions, based on the Vulnerability and Capacity Approach and the Sustainable Livelihood Approach. Our results indicate that the DRM models of the communities should be different depending on what is the vulnerability and capacity of the focal community. In disaster preparedness and response, relocation is not an expedient measure, and a well-rounded management model integrated disaster reduction with sustainable livelihood, poverty alleviation can improve risk-resistance capacity and enhances resilience of the community. The measures to adjust models facilitate to strengthen resilience of the community. Attentions must be paid to avoid secondary geological disasters risks caused by infrastructure construction in the process of relocation.

Characteristics and development trend of secondary geological disasters caused by earthquakes

the secondary geological disasters caused by earthquakes are the most developed, the largest in scale and the most destructive.Based on the large earthquakes in the world in recent years, the secondary geological disasters caused by earthquakes and their damages are analyzedAt the same time, the development trend of geological hazards in the future is predicted.

Laboratory-scale investigation of the 3-D geometry of landslide dams in a U-shaped valley

Landslide dams form when a landslide obstructs narrow and steep valleys in mountainous areas. Since these dams may fail over a short time and cause secondary geological disasters in the downstream area, the stability of such dams must be assessed in an accurate and timely manner. The three-dimensional (3-D) geometry of a landslide dam, which is one of the essential indices for stability analyses, is highly influenced by the landslide dam formation conditions, including the sliding surface dip-angle and the valley topography. However, few studies have focused on the correlation between the 3-D geometry and formation conditions of a landslide dam. A photogrammetric system was used to develop a laboratory apparatus to simulate the formation process of a landslide dam and construct a digital model for the 3-D geometry of a landslide dam in a U-shaped valley. Then, a series of experiments were designed to systematically investigate the formation process and the 3-D geometry of landslide dams under different combinations of valley bed inclinations (0, 4°, 8°, and 12°) and sliding surface dip-angles (30°, 45°, 60°, and 75°). The results indicate that the sliding surface dip-angle has a significant effect on the length and height of a landslide dam, whereas the valley bed inclination has a limited effect on the length and height compared with its effect on the relative angles of a landslide dam. In addition, the cross-sectional profiles of landslide dams can be classified into three categories, namely, symmetric, asymmetric and flat shapes, and these profiles are predominantly affected by the sliding surface dip-angle instead of the valley bed inclination. Subsequently, a mathematical model for predicting the 3-D geometry of a landslide dam was presented according to the experimental results, and it was verified by the experimental data and 42 historical cases of landslide dams. Based on the proposed model, the predicted 3-D geometry of the Tangjiashan landslide dam triggered by the Wenchuan earthquake of 2008 was consistent with its actual geometry, which confirmed the reliability of the prediction model in practical applications. The findings of our study contribute to the establishment of evidence-based disaster prevention and mitigation measures for landslide dams.

STUDY OF DISASTER EFFECT AND DISASTER MITIGATION MODEL OF ZEMUHE FAULT ZONE

The Zemuhe fault zone has large sinistral strike slip faults, which locates at the southeastern margin of the Tibetan Plateau and the eastern boundary of Sichuan-Yunnan rhombic block projections. It has the characteristics of complex terrain and strong tectonic earthquake, active and serious secondary geological disasters due to its special tectonic position, crustal deformation and faulting. The Daqing fault is located in the faulted valley basin. The Daqing Liangzi uplift area is the largest in the secondary fault of the Zemuhe fault zone. The Daqing Liangzi is the earthquake center of the magnitude 7.5 earthquake in 1850. The river valley retains the remains of glacier activities, geological disaster development. So the Daqing fault as a research object has a good typical and representative. According to the geological background condition of the disaster, the response characteristics of the slope under the action of the earthquake power and the mechanism of the slope instability, the fault disaster pattern are divided into 3 categories, 7 sub-categories and 15 types. The division of the categories is mainly based on the types of geological disasters, sub-categories to consider the disaster dynamic response process and slope instability evolution model, which is the most significant difference in the failure of the slope instability. The sub-class division is mainly based on the slope of the geological structure and stability of the form of the difference. This paper systematically reveals the genesis mechanism and the disaster model of the geological fault of Daqing fault.

Analysis of influence of natural disaster on the economy and prediction of recovery time based on grey forecasting–difference comparison model: a case study in the upper Min River

After the 2008 Wenchuan earthquake, secondary geological disasters occurred frequently and caused huge economic losses in the upper reaches of Min River. In this paper, 2003–2012 GDP data of the upper Min River were divided into two states: no disaster (2003–2007) and disaster (2008–2012). With the support of Excel and Matlab7.0 software, the data were, respectively, used to construct no disaster GM (1,1) model and disaster GM (1,1) model. Then two forecasting models were compared to establish grey forecasting–difference comparison model on the regional economic effects of natural disasters (including Wenchuan earthquake and secondary mountain hazards) and presumably analysed the influence degree and its recovery. Conclusions are drawn as follows: (1) The variation of 2003–2012 GDP in the upper reaches of Min River is shown as inclined “N”, so regional economy is affected by natural disasters significantly; (2) Using non-disaster or disaster of grey forecasting model to speculate 2008–2012 GDP and test c, p value, the results show the “good” rating that indicates the model can be used for pcrct rediction of regional GDP; (3) It obtains the I value from using grey forecasting-difference comparison model that shows a irregular “几” font variation around the 2008 year; (4) The development of natural disasters has different effects on regional economic recovery. The upper reaches of Min River can be restored to the level of non-disaster in 2014–2015. And the recovery time of these counties is that:Wenchuan County in 2015–2016, Li County in 2011–2012, Mao County in 2020–2021, Songpan Country in 2015–2016, Heishui County cannot be restored. The research results can serve as a guide and reference for the post-disaster of the regional social and economic development, overall planning and sustainability.