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Rockfalls, a common geohazard in mountainous areas, have destructive impact capacity and may cause failure of dangerous rock masses in their runout range. For slope risk assessment, a thorough understanding of the impact failure processes and dynamic characteristics associated with rockfall movements is necessary. The aim of this study is to investigate the impact of rockfall failure behaviours and disaster processes on the dangerous rock mass along the way through three‐dimensional discontinuous deformation analysis (3D DDA). To validate the reliability and applicability of 3D DDA, numerous laboratory experiments are performed on the impact of downward moving blocks on the unstable block and block system (i.e. single block–single block, single block–block system and block column–block system models) by comparing the displacements, kinetic energies and movement states of blocks. Using the G318 national road in Tibet as an example, 3D DDA simulates the impact and disaster processes associated with upper rockfalls sourced from a complete giant block and multiple discrete blocks on lower dangerous rock mass. Further, rockfall failure modes, movement characteristics, block interactions and impact phenomena are investigated. Results show that 3D DDA can effectively simulate block movement and impact interaction. The upper rockfalls impact the initially stable lower dangerous rock mass, which is the triggering factor for failure of the lower dangerous rock mass. The blocks from the upper rockfalls interact and merge to move downward, increasing the total volume and impact capacity of the rockfalls. It has been discovered that the rockfall disaster caused by the impact of an upper rockfall comprising discrete blocks on a lower dangerous rock mass is more severe than that resulting from the impact of a complete block. Overall, the results of this research can be used to help predict and prevent rockfall disasters. [ABSTRACT FROM AUTHOR]

The hazardous rock zone on the Wansui Mountain slope in Ganzi Town, Ganzi County, has experienced frequent rockfalls over the years, posing a serious threat to the lives and property of residents below. Therefore, it is crucial to conduct stability analysis of the hazardous rock zone and rockfall trajectory prediction for the Wansui Mountain slope. Focusing on the dangerous rock zone of Wansui Mountain's slope, the geometric dimensions and 3D morphology of the zone were obtained using drone oblique photography combined with field surveys. The development characteristics of the dangerous rock zone and the distribution characteristics of the dangerous rock bodies were analyzed, and the stability of the dangerous rocks was assessed. Based on RAMMS-ROCKFALL, considering the geometric shapes of the dangerous rocks and the 3D terrain, potential rockfall trajectories after the collapse of the dangerous rocks were simulated.The results show that:The slope is generally intact, with the main instability modes being falling and toppling due to weathering. A total of seven dangerous rock zones have developed, which are in an unstable state under seismic conditions; the simulation provided the relationships between rolling and bouncing heights, speeds, kinetic energy, trajectories, and positions. By predicting the rockfall trajectories, the threat range and targets of the dangerous rock zone were determined. The prediction results indicate a significant threat to the houses and pedestrians on the streets below the slope of Wansui Mountain, and remedial measures should be taken as soon as possible.The research results indicate that the use of drone oblique photography is beneficial for the stability analysis of dangerous rock bodies on slopes, compensating for the blind spots of traditional surveys, and improving the efficiency and quality of the investigation. This provides a new approach for the investigation of dangerous rock bodies and rockfall trajectory analysis, which has positive significance for disaster mitigation technology research and the management of dangerous rock bodies.

The hazardous rock zone on the Wansui Mountain slope in Ganzi Town, Ganzi County, has experienced frequent rockfalls over the years, posing a serious threat to the lives and property of residents below. Therefore, it is crucial to conduct stability analysis of the hazardous rock zone and rockfall trajectory prediction for the Wansui Mountain slope. Focusing on the dangerous rock zone of Wansui Mountain's slope, the geometric dimensions and 3D morphology of the zone were obtained using drone oblique photography combined with field surveys. The development characteristics of the dangerous rock zone and the distribution characteristics of the dangerous rock bodies were analyzed, and the stability of the dangerous rocks was assessed. Based on RAMMS-ROCKFALL, considering the geometric shapes of the dangerous rocks and the 3D terrain, potential rockfall trajectories after the collapse of the dangerous rocks were simulated.The results show that:The slope is generally intact, with the main instability modes being falling and toppling due to weathering. A total of seven dangerous rock zones have developed, which are in an unstable state under seismic conditions; the simulation provided the relationships between rolling and bouncing heights, speeds, kinetic energy, trajectories, and positions. By predicting the rockfall trajectories, the threat range and targets of the dangerous rock zone were determined. The prediction results indicate a significant threat to the houses and pedestrians on the streets below the slope of Wansui Mountain, and remedial measures should be taken as soon as possible.The research results indicate that the use of drone oblique photography is beneficial for the stability analysis of dangerous rock bodies on slopes, compensating for the blind spots of traditional surveys, and improving the efficiency and quality of the investigation. This provides a new approach for the investigation of dangerous rock bodies and rockfall trajectory analysis, which has positive significance for disaster mitigation technology research and the management of dangerous rock bodies. [ABSTRACT FROM AUTHOR]

As one of the most common failure forms of discontinuity-controlled rock slopes, wedge failure is likely to occur in a wide range of geologic and geometric conditions. In this study, the wedge failure of rock slopes and the movement and disaster processes after failure are investigated using 3D discontinuous deformation analysis (DDA). Compared with the analytical solutions derived from a typical rock wedge model, the performance of the original 3D DDA for analyzing the wedge stability under different geometrical and physical parameters is presented. The deficiency of the joint contact model in 3D DDA under critical state is improved. The improved 3D DDA is used to simulate a rock slope subjected to wedge failure in Tibet Autonomous Region, and the failure of the dangerous rock masses and movement of the formed blocks under different discontinuity cutting are discussed. The improved 3D DDA has high accuracy in calculating wedge critical stability and sliding after failure. The actual wedge slope presents sliding failure along the intersection line of structural planes, and tensile and shear failure and downward dislocations can be observed among blocks. The lateral deviation and deflection of wedge blocks occur constantly, showing 3D kinematic characteristics. With the increase of secondary discontinuities, the influence range of sub-blocks due to wedge failure becomes larger, constituting the geological disaster of the G318 national road. 3D DDA can evaluate wedge stability and analyze kinematic characteristics of wedge blocks, which lay a foundation for formulating disaster prevention countermeasures and reducing human casualties. [ABSTRACT FROM AUTHOR]

To investigate the degree of stability deterioration in toppling dangerous rock mass under different action times, firstly, the vibration load generated by train travel in a single action and its decay law were studied, and the theoretical relational equation of rock strength deterioration under the action of vibration loading was obtained by analyzing the increase in half axle expansion of micro fissures inside the rock. Secondly, the freezing stress of the microfissures was determined according to the rock freezing and swelling theory, and the theoretical relational equation of rock strength deterioration under the action of freeze-thaw cycles was obtained by integrating the rock confinement and moisture migration conditions of the fissures wall. The stability coefficient of the toppling dangerous rock mass exhibited a rapid and then slow decreasing trend with increasing number of actions, which was non-linearly negatively correlated with the train running speed and the initial porosity of the rock, and non-linearly positively correlated with the freezing temperature. Controlling the freezing temperature and initial porosity of rock can significantly reduce the degree of deterioration in the stability of dangerous rock mass. [ABSTRACT FROM AUTHOR]

Rock collapse is the most frequent type of sudden geological hazards in Beijing area. Mostly developed on high-steep slopes, this kind of collapses is difficult to investigate through the traditional contact survey method. In this paper, the three-dimensional (3D) laser scanning is used to investigate Nangang rock collapse in Mentougou District, Beijing. By combining the point cloud data and high-definition image data, the 3D space model of the Nangang collapse is constructed. On this Basis, the development characteristics of structural planes in the study area are analyzed, and three typical dangerous rock masses are selected for characteristic parameters. These parameters provide data support for the stability analysis of dangerous rock masses. Rockfall software is used to simulate and analyze the movement track of these typically dangerous rock masses, and the danger posed by rock collapses to nearby houses is studied. The results of this work provide important references for the exploration and stability evaluation of rock collapses in Beijing. [ABSTRACT FROM AUTHOR]

The steep slopes on both sides of the hydropower station in the southwestern mountainous region develop a multitude of dangerous rock formations. The rolling, collapsing and falling of these hazardous rocks have profound implications on the normal operation of the dam, main buildings, factories, roadways, and slope support systems. At present, the prediction and protection measures against rockfall disasters are predominantly reply on the two-dimensional Rockfall method, which ignores the spatial geometry of these dangerous rocks. In reality, falling rockfalls exhibit three-dimensional motion, and their threat zone extends throughout a three-dimensional geographical space. In view of this, this study is based on the hazard assessment results of the hidden danger investigation in a specific hydropower station of Yunnan Province. It employs field investigations, airborne LiDAR remote sensing measurement technology, and unmanned aerial vehicle (UAV) oblique photography technology to obtain high-precision laser radar point cloud data for the study area. This data is used to constrct detailed rock mass models and authentic three-dimensional scene models. The analysis includes historical rockfall distribution characteristics, rock mass structural characteristics, characteristics of hazardous rock masses in collapse source areas, and unstable modes. Furthermore, the study utilizes Unity3D three-dimensional rockfall analysis methods to simulate the motion characteristics of dangerous falling rocks after collapse. This enables the determination of the trajectory of dangerous falling rocks, as well as parameters such as bounce height, impact energy, and rolling area at different locations. The results indicate that for the right bank dangerous rock area of the hydropower station, a typical dangerous rock mass can achieve a maximum bounce height of up to 7.92 meters, with an impact range of approximately 145 meters. Most of these rocks roll towards the dam, which has multiple levels of passive protection nets and does not pose a threat to important facilities within the power plant. In the case of the right bank dangerous rock area two, after the collapse of dangerous rocks masses, the impact range of the falling rocks is approximately 120 meters, and some of the falling rocks may roll along the road embankment onto the road, potentially posing a threat to the main traffic artery. On the left bank, dangerous rock area one has a massive and unstable typical rock mass, with a maximum bounce height of up to 9.02 meters, ultimately falling into the reservoir storage area. Hazardous rock area two on the left bank has a dense distribution of hazardous rock masses, with a significant quantity, and after collapse, the impact range is approximately 380 meters. However, due to the dense vegetation cover on the slope, most of the falling rocks accumulate on the slope surface, posing a certain threat to pedestrians and vehicles. The related research results can provide valuable insights for the identification of hazardous rock masses and simulation of rockfall events in similar hydropower facilities.

In order to solve the problems of low efficiency, multiple blind spots, and high risks in traditional debris flow exploration, two technical means were adopted: small baseline subset interferometric synthetic aperture radar (SBAS-InSAR) and unmanned aerial vehicle (UAV) low altitude remote sensing (the former obtains highly reliable deformation of vegetation coverage areas through dense images, while the latter obtains high-resolution realistic 3D models through regional network adjustment and other processing) . Integrating deformation and image texture, a survey and analysis of debris flow valleys along a railway in a certain mountainous area was conducted to obtain the spatial and temporal distribution of geological hazards in the watershed. The results show that, through SBAS-InSAR technology, it was found that there were multiple seasonal active hazards in the debris flow valley, with a maximum deformation variable of 28.5 mm/a. Based on the 3D model of UAV, a detailed investigation was conducted on the spatial form, volume, occurrence, and development of the deformation hazard. The largest scale landslide had a volume of 165 000 to 180 000 cubic meters. On site investigations show that the comprehensive remote sensing technology can effectively overcome the challenges of complex mountainous terrain and difficult access for humans, providing a multidimensional perspective for disaster screening. It has the advantages of low personnel investment, wide monitoring area, fast disaster positioning, and high screening accuracy. [ABSTRACT FROM AUTHOR]

Copyright of Acta Geoscientica Sinica is the property of Acta Geoscientica Sinica Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The steep slopes on both sides of the hydropower station in the southwestern mountainous region develop a multitude of dangerous rock formations. The rolling, collapsing and falling of these hazardous rocks have profound implications on the normal operation of the dam, main buildings, factories, roadways, and slope support systems. At present, the prediction and protection measures against rockfall disasters are predominantly reply on the two-dimensional Rockfall method, which ignores the spatial geometry of these dangerous rocks. In reality, falling rockfalls exhibit three-dimensional motion, and their threat zone extends throughout a three-dimensional geographical space. In view of this, this study is based on the hazard assessment results of the hidden danger investigation in a specific hydropower station of Yunnan Province. It employs field investigations, airborne LiDAR remote sensing measurement technology, and unmanned aerial vehicle (UAV) oblique photography technology to obtain high-precision laser radar point cloud data for the study area. This data is used to constrct detailed rock mass models and authentic three-dimensional scene models. The analysis includes historical rockfall distribution characteristics, rock mass structural characteristics, characteristics of hazardous rock masses in collapse source areas, and unstable modes. Furthermore, the study utilizes Unity3D three-dimensional rockfall analysis methods to simulate the motion characteristics of dangerous falling rocks after collapse. This enables the determination of the trajectory of dangerous falling rocks, as well as parameters such as bounce height, impact energy, and rolling area at different locations. The results indicate that for the right bank dangerous rock area of the hydropower station, a typical dangerous rock mass can achieve a maximum bounce height of up to 7.92 meters, with an impact range of approximately 145 meters. Most of these rocks roll towards the dam, which has multiple levels of passive protection nets and does not pose a threat to important facilities within the power plant. In the case of the right bank dangerous rock area two, after the collapse of dangerous rocks masses, the impact range of the falling rocks is approximately 120 meters, and some of the falling rocks may roll along the road embankment onto the road, potentially posing a threat to the main traffic artery. On the left bank, dangerous rock area one has a massive and unstable typical rock mass, with a maximum bounce height of up to 9.02 meters, ultimately falling into the reservoir storage area. Hazardous rock area two on the left bank has a dense distribution of hazardous rock masses, with a significant quantity, and after collapse, the impact range is approximately 380 meters. However, due to the dense vegetation cover on the slope, most of the falling rocks accumulate on the slope surface, posing a certain threat to pedestrians and vehicles. The related research results can provide valuable insights for the identification of hazardous rock masses and simulation of rockfall events in similar hydropower facilities. [ABSTRACT FROM AUTHOR]

Objective In Southwest China, rockfall hazards are extremely developed in high mountains and deep valley areas with high and steep slopes. Due to the large elevation difference and steep slope, the dangerous rock mass on a high-steep slope has remarkable characteristics of suddenness. Thus, a rapid, accurate and convenient interpretation and identification for the source of dangerous rock mass becomes the primary problem of risk analysis of high-steep slopes. At present, the progress of detection makes image-based geological hazard interpretation gradually develop from visual identification to human-computer interactive identification. Among them, the UAV LiDAR system is widely used in geological disaster investigation by integrating both advantages of UAV carrier and LiDAR measurement technology, while the introduction of ground imitation flight technology can make the UAV LiDAR system adapt to complex terrain, obtaining high-precision and high-density point cloud data. Methods On this basis, a UAV survey was carried out on the East side slope of open-pit mine, and a high-precision DOM image and 3D point cloud model were obtained by processing the UAV survey data. As the supplementary materials of the DOM image, the geometric feature parameters of outcrop, including surface roughness and dip, are quantitatively extracted from the point cloud model. On this basis, a set of human-computer interactive identification for dangerous rock masses based on DOM images and geometric features is proposed. Results The application to the East side slope of open-pit mine shows that by superimposing outcrop slope geometric features based on DOM images, the proposed human-computer interactive identification method can significantly improve the efficiency and accuracy of identification, and the identification of overhanging dangerous rock mass is much more robust than visual ones. Conclusion By combining innovative remote sensing technologies, the proposed method provides a fast and convenient solution for the identification of dangerous rock masses on high and steep rocky slopes.

In karst areas, the mountains are bare and the terrain is steep. Once the dangerous rock mass developed instability, it will threaten the lives and properties of the residents. So it is significant to analyze the stability and hazards of the disasters in a timely and accurate manner. Taking the dangerous rock mass of Changchong Group in Heping Community, Songtao County, Guizhou Province as the object, combined with the results of engineering survey, the disaster-generating background of the dangerous rock mass areas, such as topography, geological structure and hydrology, were analyzed, and the development characteristics of the dangerous rock mass were analyzed deeply. The failure mode and influencing factors of dangerous rock mass was demonstrated. On this basis, qualitative and quantitative analysis of the stability of the dangerous rock mass was carried out, and the hazard degree and development trend of the dangerous rock mass are evaluated. The results show that the unique karst landforms, karst features and complex structural planes of the dangerous rock mass developed in karst mountainous areas are the key factors controlling the stability, and rainfall and weathering are the main inducing factors. A preliminary prevention plan has been proposed to provide a reference for subsequent treatment measures.

Dangerous rock mass refers to the rock mass that is cut by the structural plane and fails under certain inducing factors. As one of the common natural geological disasters, it seriously affects the safety of human life and property in mountainous areas. The exploration, stability evaluation and risk evaluation of dangerous rock mass are difficult problems in the research of geological disaster prevention. Affected by human engineering activities, there are many dangerous rock masses in Baimagou, Xindian Town, Mingshan County. Based on the analysis and Research on the distribution and development characteristics of collapse dangerous rock mass in baimagou, this paper preliminarily summarizes the formation, distribution law and disaster mechanism of dangerous rock mass in Guankou formation (K2g) of Upper Cretaceous system, and carries out numerical simulation calculation for four collapse dangerous rock bodies in this area by using Rockfall, calculates their movement speed and trajectory, and calculates the rock bounce height and distance, It provides a reference for the stability evaluation and motion trajectory analysis of dangerous rock mass under such engineering geological conditions.

Copyright of Chinese Journal of Geological Hazard & Control is the property of China Institute of Geological Environmental Monitoring (CIGEM) Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, the Jianchuandong dangerous rock mass in the Three Gorges Reservoir area is taken as an example to study the failure mode and protection of submerged thick-layer dangerous rock mass. Based on field investigation and the monitoring data, it was found that the degradation of the base rock mass under the dry-wet cycles is the main factor to accelerate the deformation of the dangerous rock mass. Its failure mode is determined as slip collapse. According to the deformation and failure characteristics of the dangerous rock mass, the corresponding treatment measure is divided into two parts, inculding the reinforcement of the weak base rock mass, and anchor cable in the upper part of the dangerous rock mass. By comparing the displacement field and the stress field before and after protection, it is found that the prestressed reinforcement of the upper dangerous rock mass can effectively control the deformation of the rock mass, and the reinforcement of base rock mass can effectively control the maximum shear stress of the dangerous rock mass. The comprehensive protection effect is significant to ensure the stability of dangerous rock mass. The protection method can provide important reference for the treatment of submerged dangerous rock mass in the reservoir area.

Copyright of Chinese Journal of Geological Hazard & Control is the property of China Institute of Geological Environmental Monitoring (CIGEM) Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To improve the accuracy of information acquisition, the density-based spatial clustering application with noise (DBSCAN) algorithm was improved based on 3D point clouds. The k-nearest neighbor algorithm and the evaluation criterion based on density ratio S were used to divide the point cloud regions with different densities in order to set parameter e and analyze the point cloud normal vector adaptive. The angle threshold T of normal vectors was introduced to determine the points belonging to the same plane and the points belonging to the same plane were displayed with the same colour. This paper discussed the influence of different parameter combinations on the identification results and enabled a fast analysis of rock joints. The research results could provide a reliable application method for efficient measurement of discontinuity information. [ABSTRACT FROM AUTHOR]

The stability of the slope under excavation in various engineering is a hot issue, and both engineering disturbances and other internal factors have contributed to the instability of the slope. The study focused on the deformation characteristics mechanism of exit slope of Qingshuigou tunnel in Jiasha Town, Gejiu City, Honghe Prefecture, Yunnan, China. Field survey and monitoring are performed to reveal deformation mechanism of the exit slope, which is associated with hydrogeologic conditions, natural weathering, and excavation activities. The exit slope at the interface of the overburdened layer and bedrock has the possibility of landslide through the joint force of rainfall and artificial construction. According to the deformation characteristics of the exit slope and monitoring analysis, the results indicate that the surface displacement at the back scarp of the exit slope is larger than that at the head scarp of the exit slope. The deep displacement at the back scarp is 2–4 times of that at the head scarp of the slope. Based on the geophysical analysis, the overburdened layer mostly has low resistivity. The deformation mechanism of the exit slope is revealed ultimately based on the combined influences of hydrogeologic conditions, natural weathering, and excavation activities. Based on the deformation characteristics and mechanism of the exit slope, comprehensive stabilization treatment measures are proposed to prevent the exit slope from further deformation. [ABSTRACT FROM AUTHOR]

Changes in water level of the Three Gorges Reservoir are easy to induce the deformation and failure of the reservoir slope. Periodic impoundment changes in the groundwater seepage field and stress field in the reservoir slope reduce the shear strength of rock and soil mass, and have a great impact on the stability of the reservoir bank slope and rock mass. It is urgent for the deformation monitoring of bank slopes in the reservoir area. It is difficult to find out the overall change of rock mass by setting fixed observation points, and the terrestrial laser scanning method (TLS) can obtain the point cloud data of the overall rock mass surface with centimeter accuracy, which is very suitable for the monitoring of rock mass of characteristics of no contact with the target, fast acquisition speed and high precision. In this paper, the terrestrial laser scanning method is used to monitor the dangerous rock mass of Jianchuandong in Wuxia county for two years (2017—2018) and three periods data are acquired. The stable rock mass data around the observation target of the first period is selected as datum and the iterative closest point registration (ICP) is carried out with the overlapping point cloud. The registration accuracy of the point cloud is better than ± 2.7 cm, which realizes the accurate alignment of multi-period data. According to the change of dangerous rock mass in the observation period, the datum TIN model of dangerous rock body area is constructed, and the deformation of dangerous rock mass is analyzed with the nearest distance method from point to reference surface combined with the change range of dangerous rock mass. Through the comparative analysis of the 3 periods observation data of the Jianchuandong dangerous rock mass, it is found that the dangerous rock mass has the expansion trend in 2018 compared with the left rock mass in 2017. In the reservoir water storage stage, there are obvious sag changes in some parts of the dangerous rock body, and the local deformation is about 30-70 mm due to the influence of water storage. The experiment proves the correctness and validity of the proposed monitoring method, which provides reference for the monitoring of dangerous rock state and the prevention and control of geological disasters in the Three Gorges Reservoir area.

• A model has been developed to simultaneously consider the degradation of fracture toughness and the frost-induced expansive forces between structural planes, addressing the stability degradation of dangerous rock masses. • The mechanism of microscopic pore evolution within rocks under freezing-thawing cycles is revealed, based on the theory of circular pore expansion. • A model has been developed to characterize the degradation of rock fracture toughness in the bridge segments of dangerous rock masses subjected to freeze–thaw cycles. The instability of dangerous rock masses is primarily caused by the stress intensity factor at the primary structural plane exceeding the fracture toughness of the rock bridge section, which results in the propagation of fractures. Additionally, in cold regions, the fracture toughness of these rock masses gradually decreases due to freeze–thaw cycles. Initially, considering the deterioration of type I and type II fracture toughness in the rock bridge section and the frost heaving force between structural planes, an assessment model for the stability of dangerous rock mass under freeze–thaw cycles is established. Secondly, utilizing the theory of circular hole expansion, along with the Mohr-Coulomb yield criterion and maximum tensile stress criterion, a model is constructed to simulate the degradation of type I and type II fracture toughness in rock bridge segments under the influence of freeze–thaw cycles. The validity of this model was subsequently verified through experimental validation. Finally, through engineering case studies, the degradation pattern of the stability of dangerous rock formations under the action of freeze–thaw cycles was analyzed. The study reveals that the decreasing stability of dangerous rock mass under freeze–thaw conditions is intricately linked to the internal friction angle, elastic modulus, and initial tensile strength of the rocks. Notably, the long-term stability of hard and coarsely textured dangerous rock mass under such conditions generally improves. Conversely, the tensile strength of the rock bridge segment elevates, which is beneficial for the long-term stability of the rock mass. When the residual debris ratio exceeds 0.25, the instability of the rock mass deteriorates more modestly. To maintain long-term stability, managing debris loss or injecting fillers into the pores can be effective strategies. [ABSTRACT FROM AUTHOR]

Copyright of Advanced Engineering Science / Gongcheng Kexue Yu Jishu is the property of Advanced Engineering Science Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A rockfall is a typical dynamic problem of a discontinuous block system originating from a dangerous rock mass and always presents serious geo-hazards along highway slopes in mountainous areas. This study aims to investigate the failure mechanisms and movement characteristics of rockfalls through a three-dimensional discontinuous deformation analysis (3D DDA) method and attempts to comprehensively examine the complicated kinematic process of rockfall disasters. In terms of the initial failure and post-movement characteristics (i.e., motion trajectory and kinetic energy) of a rockfall, the effectiveness of 3D DDA is verified by comparing its results with those of laboratory experiments. Taking the K4580 typical high-steep slope undergoing rockfalls along the G318 national highway in Tibet as an example, the initiation and failure of a single boulder and a large-scale rock mass at the source area were simulated by 3D DDA. Then, the movement characteristics of the boulder and massive collapsing rocks along the slopes of different geometrical characteristics, i.e., the slopes before the landslide and after the shallow and deep landslides, were studied. The results show that the 3D DDA has significant advantages in analysing the failure mechanisms of slope rockfalls and can satisfactorily simulate the spatial movement (e.g., lateral deviation and deflection) of blocks by considering the 3D geometry of the slopes and blocks. The 3D DDA numerical simulation can predict the movement range, deposition position, and affected area of rockfall disasters, which can provide a basis for formulating disaster prevention countermeasures in actual projects. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Geological Hazard & Control is the property of China Institute of Geological Environmental Monitoring (CIGEM) Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Hydrogeology & Engineering Geology / Shuiwendizhi Gongchengdizhi is the property of Hydrogeology & Engineering Geology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As a frequent occurring geomorphological process characterized by high energy and mobility, the rockfall movement is the basis of the disaster prediction and mitigation. In this study, the kinematic evolution behaviors of rockfalls are investigated using three-dimensional discontinuous deformation analysis (3D DDA) based on block kinematics. A series of field experiments are designed by orthogonal experimental method to study the block movement considering the influence of the slope angle, the characteristics of the block itself and the initial falling conditions. Selecting the combination of factors that have the most significant influence on the block movement, the 3D DDA numerical model is established and the effectiveness of 3D DDA is verified by comparing the displacement and kinetic energy evolutions obtained by experiments. Then, the 3D DDA is applied to simulate the rockfalls of Wangxia slope in Chongqing, and the kinematic evolutions of the entire rockfall processes are further studied by analyzing the rock mass instability and the movement trajectory and kinetic energy evolutions of blocks. The experimental results show that slope angle has the greatest influence on block kinematics, followed by block mass, falling height, block shape and falling angle. In the practical slope analysis, the rockfall processes consist of sliding failure, oblique projectile movement, flying over or colliding with the highway, and flying away from the slope, showing 3D movement characteristics due to lateral translation and rotation. The rockfall kinematic evolutions induce slope disasters to the highway, and pose a threat to shipping in Yangtze River channel. The 3D DDA method can quantitatively analyze the failure of dangerous rock masses and the kinematic evolutions of rockfalls after instability, which is helpful to provide revealing insights into the rockfall disaster processes and mechanisms. [ABSTRACT FROM AUTHOR]

In order to study the treatment of a dangerous thick submerged rock mass, the Jianchuandong dangerous rock mass (JDRM) in the Three Gorges reservoir area is analyzed in this paper. Field investigation, on-site monitoring, and laboratory testing were used to analyze the deformation and failure mode of the dangerous rock mass. The analysis shows that the uneven pressure caused by the weight and deterioration of the base of the rock mass during the dry-wet cycles will eventually lead to slump failure of the JDRM. Preventative methods, including anchoring the upper part of the dangerous rock mass and reinforcement of the base of the rock mass, are proposed to improve the stability of the dangerous rock mass. Based on a numerical simulation, we conclude that anchoring the upper dangerous rock mass can effectively control the deformation of the dangerous rock mass and reinforcement of the base of the rock mass can block the slip zone of the dangerous rock mass. The combination of these two preventative methods significantly improves the stability of the dangerous rock mass. By comparing the stability of the dangerous rock mass before and after the implementation of these preventative methods during the dry-wet cycles, it can be seen that the preventative methods can satisfactorily ensure the long-term stability of the dangerous rock mass. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Geological Hazard & Control is the property of China Institute of Geological Environmental Monitoring (CIGEM) Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As the economy of China develops, an increasing number of key traffic projects have been undertaken in the west of China, where there are high, steep rock slopes. The collapse of dangerous rock masses, especially following a strong earthquake, is one of common geological disasters known in rock slope engineering. Therefore, it is important to study the collapse mechanism of dangerous rock masses induced by an earthquake and the analysis approach of its stability. This study provides a simple and convenient method to determine the collapse mechanisms of two types of dangerous rock masses (i.e. cantilever and upright) associated with the definition and calculation of the safety factor, which is based on the flexure theory of a constant-section beam by combining with the maximum tensile-stress criterion to depict the process of crack propagation caused by seismic waves. The calculation results show that there are critical crack depths in each form of the dangerous rock masses. Once the accumulated depth of the crack growth during an earthquake exceeds the critical depth, the collapse will occur. It is also demonstrated that the crack extension amount of each step is not a constant value, and is closely associated with the current accumulated crack depth. The greater the cumulative crack depth, the more easily the crack propagates. Finally, the validity and applicability of the proposed method are verified through two actual engineering examples. [ABSTRACT FROM AUTHOR]

The dynamics analysis of dangerous rock mass simplified into improved shear-beam model is progressed based on the engineering example of Zenziyan in Jinfo Mountain, and the definite problem of seismic response on stratified rock mass is solved to obtain the maximum response rules of absolute acceleration, shear stress and relative displacement of rock strata, then the practical monitoring data are taken to make contrastive analysis of the above calculation results and verify the rationality of stability evaluation using this analytic method which can complement the quantitative calculation means of dangerous rock mass and provide reference for the similar engineering construction designs. [ABSTRACT FROM AUTHOR]

In 2007 and 2008, six big damaging rockfalls occurred at four sites in Wu Gorge, the second gorge of the Three Gorges, China. Detailed surveys and aerial-photographic interpretation identified 104 potentially dangerous rock masses. This paper reviews previous rock-mass risk ratings, examines dangerous rock-mass structure and presents a new assessment system for rockfall risk (ASRFR) in the Wu Gorge area. The ASRFR considers 15 factors: seven factors for hazard and eight factors for consequence. Relative importance weights for these factors are ascertained using an analytic hierarchy process. Using an equation to calculate the risk, the 104 dangerous rock masses were divided into three risk groups: high risk (33 sites), medium risk (33 sites) and low risk (38 sites). The ASRFR analysis can be used to divide the shipping route through the Wu Gorge into seven courses each of one of three classes: safe-route regions, yellow-alarm regions and red-alarm regions. The system provides geological information and a rockfall-risk management tool for local government and the shipment-route department. [ABSTRACT FROM AUTHOR]

To analyze the deformation mechanism and to evaluate the stability of a dangerous rock mass, we investigated the Jianchuandong Dangerous Rock Mass (JDRM) in the Three Gorges Reservoir area. By generalizing the JDRM mechanical model, we found that the damage and degradation of the base rock mass will eventually lead to its collapse. The weight of the upper rock mass and the periodic change in the reservoir water level result in a weakened and increasingly damaged base rock mass. Based on data from laboratory tests, we created constitutive damage models for the base rock mass under dry-wet conditions. Applying these models allowed us to quantify the damage and the stability of the submerged dangerous rock mass over time. In this new method, the effective axial pressure can be determined from the damage variables, and that pressure informs the stability of the dangerous rock mass. This new modeling technique was validated by the similarity between our calculated constraints on the effective axial pressure of the JDRM and the actual on-site pressure monitoring results. Furthermore, because our new methodology reveals that the JDRM will become unstable after two dry-wet cycles, we recommend that measures be taken to reinforce the JDRM as soon as possible. • Generalization of the mechanical model of the submerged dangerous rock mass • Establishment of statistical damage constitutive model of rock under dry-wet cycles • Mechanical damage analysis of the submerged dangerous rock mass [ABSTRACT FROM AUTHOR]