Secondary Geological Hazard Research Articles

Numerical Simulation of Surface Subsidence and Fracture Evolution Caused by Pulang Copper Mine Mining

Subsidence of the earth’s surface induced by mining activities has always been a critical concern in the relevant research fields. This subsidence disrupts the original geological structures and can lead to secondary geological hazards, environmental degradation, and threats to human lives and property. An in-depth investigation of this issue led to us using the three-dimensional finite-difference numerical simulation software FLAC3D 6.0 in this study. The research focuses on the Prang Copper Mine subsidence area in Yunnan Province, China, with a particular emphasis on the comprehensive analysis of the formation mechanisms of a large-scale crack appearing on the south side of the subsidence area. The study also includes a predictive analysis of the future development trends of this crack. The simulation results indicate that the crack formation was a consequence of the combined effects of uneven surface subsidence induced by underground structural interfaces and underground mining activities. As mining activities continued, the non-uniform subsidence of the surface intensified. The northward (Y-axis) displacement difference of characteristic points A and B on both sides of the crack continuously increased, signifying the widening of the crack. Mining activities also influence the displacement in the X-axis direction, potentially posing risks to support structures on either side of existing drainage channels. Therefore, effective control measures are warranted. Furthermore, this study highlights the possibility that new mining activities may further exacerbate subsidence on the south side of the subsidence area. This research provides valuable insights into the complexity of surface subsidence and its associated risks, offering guidance for mining activity planning and safety measures.

Study on Preparation and Performance of Foamed Lightweight Soil Grouting Material for Goaf Treatment.

The harm goafs and other underground cavities cause to roads, which could lead to secondary geological hazards, has attracted increased attention. This study focuses on developing and evaluating the effectiveness of foamed lightweight soil grouting material for goaf treatment. The study examines the foam stability of different foaming agent dilution ratios by analyzing foam density, foaming ratio, settlement distance, and bleeding volume. The results show that there is no significant variation in foam settlement distance for different dilution ratios, and the difference in foaming ratio does not exceed 0.4 times. However, the bleeding volume is positively correlated with the dilution ratio of the foaming agent. At a dilution ratio of 60×, the bleeding volume is about 1.5 times greater than that at 40×, which reduces foam stability. Furthermore, an appropriate amount of sodium dodecyl benzene sulfonate improves both the foaming ability of the foaming agent and the stability of the foam. Additionally, this study investigates how the water-solid ratio affects the basic physical properties, water absorption, and stability of foamed lightweight soil. Foamed lightweight soil with target volumetric weights of 6.0 kN/m3 and 7.0 kN/m3 meet the flow value requirement of 170~190 mm when the water-solid ratio ranges are set at 1:1.6~1:1.9 and 1:1.9~1:2.0, respectively. With an increasing proportion of solids in the water-solid ratio, the unconfined compressive strength initially increases and then decreases after 7 and 28 days, reaching its maximum value when the water-solid ratio is between 1:1.7 and 1:1.8. The values of unconfined compressive strength at 28 days are approximately 1.5-2 times higher than those at 7 days. When the water ratio is excessively high, the water absorption rate of foamed lightweight soil increases, resulting in the formation of connected pores inside the material. Therefore, the water-solid ratio should not be set at 1:1.6. During the dry-wet cycle test, the unconfined compressive strength of foamed lightweight soil decreases, but the rate of strength loss is relatively low. The prepared foamed lightweight soil meets the durability requirements during dry-wet cycles. The outcomes of this study may aid the development of enhanced approaches for goaf treatment using foamed lightweight soil grout material.

Land Cover Changing Pattern in Pre- and Post-Earthquake Affected Area from Remote Sensing Data: A Case of Lushan County, Sichuan Province

Extremely hard-hit areas face frequent secondary geological hazards and difficulties in vegetation recovery, and subsequent effects have a significant impact on land cover changes. At present, there is a lack of research on the dynamic restoration of, and changes in, the ecological environment before and after an earthquake, and especially a lack of quantitative assessment of the impact of earthquakes on land cover at the microscopic scale of spatial distribution of landscape indices. Taking the Lushan earthquake in Sichuan Province as an example, this paper obtained land cover data from the study area between 2012 and 2020, and analyzes the spatial distribution characteristics and influencing factors of land cover change frequency by using a comprehensive land cover degree index, land cover transfer matrix and landscape ecology index. The results show that the types of cropland, forest, built-up and bare land have changed significantly in the study area. During the earthquake recovery period, the comprehensive land cover index of the study area showed an increasing trend, and land cover has been continuously improved under the effect of artificial measures and natural restoration. After 2013, patch density (PD) and landscape shape index (LSI) values decreased and aggregation index (AI) values increased for the vast majority of landscape land classes, indicating a benign ecological development across the region in the post-earthquake period. The research results are not only helpful to establish scientific ecological environmental management in the earthquake-stricken areas, but also helpful to formulate medium- and long-term ecological environmental monitoring and ecological restoration plans based on land cover change patterns.

Determinants of People’s Secondary Hazards Risk Perception: A Case Study in Wenchuan Earthquake Disaster Areas of China

Few studies have examined people’s subjective perceptions of risk after secondary disasters. This study selected 12 towns in the areas where secondary geological hazards (SGH) occurred after the Wenchuan earthquake as the survey research areas and obtained a total of 957 valid samples to assess the risk perceptions of residents and the factors influencing them 10 years after the disaster. Using four indicators (possibility, awareness, apprehension, and impact) to construct the Resident Risk Perception Index (RRPI), the results show that residents in the affected areas have high, moderate, and low-risk perceptions of SGH at 27.59, 48.38, and 24.03% respectively. The study found that people who suffered in the past from geological disasters had a higher risk perception. Perceptions of secondary geological hazard risk varied significantly with age, education, marital status, and experience. It was also found that residents in the 30–40 age group have the highest risk perception, young people in the 20–30 age group have the highest risk awareness, and older people over 60 are more fearful of SGH. The study recommends awareness campaigns and adequate disaster preparedness exercises to improve the risk perception of local people, especially to foster ownership of learning about disasters among residents.

A Research on Landslides Automatic Extraction Model Based on the Improved Mask R-CNN

Landslides are the most common and destructive secondary geological hazards caused by earthquakes. It is difficult to extract landslides automatically based on remote sensing data, which is import for the scenario of disaster emergency rescue. The literature review showed that the current landslides extraction methods mostly depend on expert interpretation which was low automation and thus was unable to provide sufficient information for earthquake rescue in time. To solve the above problem, an end-to-end improved Mask R-CNN model was proposed. The main innovations of this paper were (1) replacing the feature extraction layer with an effective ResNeXt module to extract the landslides. (2) Increasing the bottom-up channel in the feature pyramid network to make full use of low-level positioning and high-level semantic information. (3) Adding edge losses to the loss function to improve the accuracy of the landslide boundary detection accuracy. At the end of this paper, Jiuzhaigou County, Sichuan Province, was used as the study area to evaluate the new model. Results showed that the new method had a precision of 95.8%, a recall of 93.1%, and an overall accuracy (OA) of 94.7%. Compared with the traditional Mask R-CNN model, they have been significantly improved by 13.9%, 13.4%, and 9.9%, respectively. It was proved that the new method was effective in the landslides automatic extraction.

Characteristics and triggering mechanism of Xinmo landslide on 24 June 2017 in Sichuan, China

At 5: 39 AM on 24 June 2017, a huge landslide-debris avalanche occurred on Fugui Mountain at Xinmo village, Diexi town, Maoxian county, Sichuan province, China. The debris blocked the Songpinggou River for about 2 km, resulting in a heavy loss of both human lives and properties (10 deaths, 3 injuries, 73 missing, and 103 houses completely destroyed). The objectives of this paper are to understand the overall process and triggering factors of this landslide and to explore the affecting factors for its long term evolution before failure. Post event surveys were carried out the day after the landslide occurrence. Information was gathered from literature and on-site investigation and measurement. Topography, landforms, lithology, geological setting, earthquake history, meteorological and hydrological data of the area were analysed. Aerial photographs and other remote sensing information were used for evaluation and discussion. Eye witnesses also provided a lot of helpful information for us to understand the process of initiation, development and deposition. The depositional characteristics of the moving material as well as the traces of the movement, the structural features of the main scarp and the seismic waves induced by the slide are presented and discussed in detail in this paper. The results show that the mechanism of the landslide is a sudden rupture of the main block caused by the instability of a secondary block at a higher position. After the initiation, the failed rock mass at higher position overloaded the main block at the lower elevation and collapsed in tandem. Fragmentation of the rock mass occurred later, thus forming a debris avalanche with high mobility. This landslide case indicates that such seismic events could influence geological hazards for over 80 years and this study provides reference to the long term susceptibility and risk assessment of secondary geological hazards from earthquake.

A secondary sludge flow hazard induced by shallow-source seismic activity in karst mining area, Guangxi, South China: localized karstification in anticline

On the 16th of June 2013, a small-magnitude, shallow-source seismic activity just occurred at a karst mining area. No serious ground damage occurred, but it induced a secondary geological hazard. The wastewater and sludge leaked from the mining water reservoir which caused a great economic loss and groundwater contamination through multilevel underground karst channels. The seismic swarm was located along the Youjiang fault, an active fault zone whose kinematics is controlled by the regional tectonic stress field with NW300° compression and NE30° extension. The tectonic fractures are sealed by calcite, and stylolites have permeabilities of less than 0.01 mD. The localized intensive karstification occurred at the core of Yalang anticline, which is the result of a local extension stress environment and hydrogeological conditions. The seismic activity in the study area is not strong enough to cause ground destruction, but did alter the flow dynamics of groundwater. The seismic activity may have caused a temporary high pressure fluid in the fault zone. The karst system blocked by sediments can be dredged by the fluid pressure. Then, the karstification of limestone massif could be re-activated.

A new fast method for earthquake-triggered secondary geological hazard information extraction from high-resolution remote sensing imagery

Earthquake-triggered secondary geological hazards usually significantly augment the destruction caused by an earthquake due to their rapid impact, long duration and high repeatability. Seismic disaster losses are often exacerbated and can cause substantial difficulties for rescue, relief and post-disaster reconstruction. The quick acquisition of disaster information is important to aid relief efforts in the 72 critical hours after an earthquake occurs. Currently, computer-aided interpretation of remotely sensed imagery of a single time phase plays a central role in information extraction for geological hazards, whereas automated interpretation is relatively limited. Because high-resolution remotely sensed imagery is rich in textures and spatial details of the imaged objects, such as their size, shape and neighborhood relationship, geologic hazard investigations employing such imagery can offer more accurate results. In this paper, a rapid method for earthquake-triggered secondary geological hazard information extraction from high-resolution remotely sensed imagery is proposed and is demonstrated to be a fast and automatic method that uses multiple image features of a hazard.

Dynamic process analysis for the formation of Yangjiagou landslide-dammed lake triggered by the Wenchuan earthquake, China

The damming of rivers by landslides resulting in the formation of a lake was one of the typical secondary geological hazards triggered by the Wenchuan earthquake which occurred on May 12, 2008. Some landslide-dammed lakes were at a high risk of causing further damage since the rainstorm season was expected soon after the earthquake. Understanding the dynamic processes in the formation of landslide-dammed lakes is helpful in planning the mitigation measures. The Yangjiagou landslide-dammed lake was selected as a case study to investigate the typical processes of dam formation. The dynamic simulation of the formation of the Yangjiagou landslide-dammed lake was divided into two steps: the landslide step and the overflow/overtopping step. Two-dimensional discrete element method (DEM) was adopted to investigate the mechanics of the Yangjiagou landslide. The landslide process was found to be controlled by the bond strength and residual friction coefficient of the DEM models. Computational results show that the formation of the landslide dam took approximately 35 s. The maximum velocity of a typical particle was approximately 26.8 m/s. The shallow-water equation and finite difference method were used to analyze the hydrodynamic mechanisms of the overflow process of the landslide-dammed lake. Computational results show that overflow would have occurred 15.1 h after the river was blocked, and overtopping failure occurs for the landslide dam in the rainstorm season when the water flow is large enough, causing a major disaster.

Controlling parameter analyses and hazard mapping for earthquake-triggered landslides: an example from a square region in Beichuan County, Sichuan Province, China

On May 12, 2008, at 1428 hours (Beijing time), a catastrophic earthquake, with a magnitude of Ms 8.0, struck the Sichuan Province, China. About 200,000 landslides, as a secondary geological hazard associated with the earthquake, were triggered over a broad area. These landslides were of almost all types such as shallow, disrupted landslides, rock falls, deep-seated landslides, and rock avalanches. Some of these landslides damaged and destroyed large part of some towns, blocked roads, dammed rivers, and caused other serious damages. The purpose of this study is to detect correlations between landslide occurrence and the surface rupture plane, ground shaking conditions (measured by peak ground acceleration, PGA), lithology, slope gradient, slope aspect, topographic position, and distance from drainages by using two indices, landslide area percentage (LAP) and the landslide number density (LND), based on geographic information system (GIS) technology and statistical analysis method in a square region (study area) of Beichuan County, Sichuan Province, China. There were 5,096 landslides related with the earthquake which were delineated by visual interpretation and selected field checking throughout the study area. The total area (horizontal projection) of the 5,096 landslides is about 41.103 km2. The LAP, which is defined as the percentage of the plane area affected by landslides, was 10.276 %, and the LND, means the number of landslides per square kilometers, was 12.74 landslides/km2. Statistical analysis results show that both LAP and LND have a positive correlation with slope gradient and a negative correlation with distance from the surface rupture. However, the correlation between the occurrence of landslides with PGA, topographic position, and distance from drainages are uncertain, or has just a little positive correlation. The correlation between landslide and slope aspect also shows the effect of the directivity of the seismic wave. The Zbq formation had the most concentrated landslide activity with the LND value of 21.78 landslides/km,2 and the ∈1q Gr. geological units had the highest LAP value. Furthermore, weight index (Wi) model is performed with a GIS platform to derive landslide hazard index map. The success rate of the model was 71.615 % and, thus, it was valid. In addition, comparison of five landslide controlling parameters’ influence on landslide occurrences was also carried out.

Geological Disasters Induced by Wenchuan Earthquake and Site Selection for Post-Earthquake Reconstruction

Based on the field investigation for secondary geological hazards induced by 5.12 Wenchuan Earthquake, the types of geological disasters during or after earthquake are analyzed in this paper. The main secondary geological hazards are rock fall and collapse, landslide, debris flow, dammed lake，sand liquefaction and so on. The development and distribution rules of secondary geo-hazards, with a long-term sustainability and a formation of hazard chains, are of relation with earthquake fault zone, and consistent with seismic intensity. The buildings located in secondary geo-hazards areas with a high risk are damaged severely, thus the site selection for post-earthquake reconstruction and related geotechnical engineering issue are discussed, which are useful in reconstruction of Wenchuan earthquake area.

The Remote Sensing Investigation of the Secondary Geological Hazards Situation in the West Mountain Area of Qingchuan County in Sichuan Province and Suggestions Concerning Prevention and Control

In this paper,the west mountain area of Qingchuan County,one of the most serious earthquake hazards areas in Wenchuan County with representative significance,was chosen as the study area.The relations between the special structural position and the secondary geological hazards were analyzed,the remote sensing interpretation keys to the secondary geological hazards were established,the predominant types of the secondary geological hazards in this area were summarized,and the hazards situation in this area were estimated.On such a basis,some reasonable suggestions concerning the prevention and control of such hazards are put forward.

Secondary geological hazard analysis in Beichuan after the Wenchuan earthquake and recommendations for reconstruction

The Wenchuan earthquake, also known as 2008 Sichuan Earthquake, occurred along the Longmenshan fault zone on 12 May 2008 at 14:28:01.42 CST (06:28:01.42 UTC). It caused serious damage to structures in the region. Beichuan is a town which is within these severely damaged areas. According to the earthquake intensity distribution map of 2008 Wenchuan earthquake officially released by the China Earthquake Administration, the earthquake intensity in Beichuan was XI on the China seismic intensity scale. As the earthquake occurred in a mountainous area, there were thousands of landslides, rockfalls, debris flows, and surface ruptures triggered by the earthquake over a broad area. These secondary geological hazards substantially increased the human, social and economic impact of the earthquake. This paper presents a post-earthquake analysis on the secondary geological hazards in Beichuan. The risk analyses associated with construction of the National Earthquake Memorial Museum in Beichuan are assessed and recommendations on risk mitigations for the mass reconstruction over the ruins are also provided based on this field study.

Co‐seismic Faults and Geological Hazards and Incidence of Active Fault of Wenchuan Ms 8.0 Earthquake, Sichuan, China

Abstract:There are two co‐seismic faults which developed when the Wenchuan earthquake happened. One occurred along the active fault zone in the central Longmen Mts. and the other in the front of Longmen Mts. The length of which is more than 270 km and about 80 km respectively. The co‐seismic fault shows a reverse flexure belt with strike of N45°–60°E in the ground, which caused uplift at its northwest side and subsidence at the southeast. The fault face dips to the northwest with a dip angle ranging from 50° to 60°. The vertical offset of the co‐seismic fault ranges 2.5–3.0 m along the Yingxiu‐Beichuan co‐seismic fault, and 1.5–1.1 m along the Doujiangyan‐Hanwang fault. Movement of the coseismic fault presents obvious segmented features along the active fault zone in central Longmen Mts. For instance, in the section from Yingxiu to Leigu town, thrust without evident slip occurred; while from Beichuan to Qingchuan, thrust and dextral strike‐slip take place. Main movement along the front Longmen Mts. shows thrust without slip and segmented features. The area of earthquake intensity more than IX degree and the distribution of secondary geological hazards occurred along the hanging wall of co‐seismic faults, and were consistent with the area of aftershock, and its width is less than 40 km from co‐seismic faults in the hanging wall. The secondary geological hazards, collapses, landslides, debris flows et al., concentrated in the hanging wall of co‐seismic fault within 0–20 km from co‐seismic fault.

A study on coal mining under large reservoir areas

At present, the easily mineable coal resources have been depleted in China, and it is very necessary and urgent to mine under hydraulic projects for continuous production and sustainable development of the society. In this paper, the coal field of Shenjiazhuang Colliery, which mostly lies under the Yuecheng reservoir area, is studied. By using a comprehensive study involving field engineering geologic survey, indoor rock mechanics test, in situ test, statistical analysis of mine well discharge, water quality analysis, theoretical calculation and numerical simulation, it is concluded that coal mining would not affect safe operation or bring any secondary geological hazard to the reservoir area. This paper provides an important scientific basis for achieving double profits for both departments of water and coal resources and helping departments related make further decisions. In addition, the research reported in the current paper can be served as a reference for similar projects, such as the coal mines under the Xiaolangdi reservoir area, under the Xifeihe Dam and under the mid-route South-to-North Water Transfer Project.