High-steep Rock Slope Research Articles

Automatic identification and interpretation of discontinuities of rock slope from a 3D point cloud based on UAV nap-of-the-object photogrammetry

Research on rock slopes has attracted considerable attention in the fields of infrastructure construction and disaster prevention. The search for an efficient and reliable method for discontinuity collection is an important task for various studies of jointed rock slope. Capturing high-precision and complete rock exposure images based on unmanned aerial vehicle (UAV) multi-angle and nap-of-the-object photogrammetry technology is proposed to realize the construction of a millimeter-level 3D point cloud for the high and steep slope. This study develops a new automatic methodology for discontinuity identification and interpretation. A Delaunay triangulation network is created for connecting adjacent points in the point cloud to calculate normal vectors and search for neighbor points efficiently. Combined with the modified region-growing algorithm, an automatic procedure which identifies discontinuities and acquires geometrical parameters efficiently and accurately is established. The proposed approach is applied to the high-steep rock slope on the northern bank of the Sequ Grand Bridge in the Changdu area of Tibet. Compared with the results from the manual survey, the proposed method is more reliable and exhibits high accuracy for discontinuity identification and interpretation on rock exposure.

Research on fine collection and interpretation methods of discontinuities on high-steep rock slopes based on UAV multi-angle nap-of-the-object photogrammetry

Research on fine collection and interpretation methods of discontinuities on high-steep rock slopes based on UAV multi-angle nap-of-the-object photogrammetry

Proposition of UAV multi-angle nap-of-the-object image acquisition framework based on a quality evaluation system for a 3D real scene model of a high-steep rock slope

The 3D real scene model of high-steep rock slope established based on UAV image provides convenience for non-contact identification and interpretation of rock mass structures. The quality of 3D models directly influences the interpretability of rock mass structures. However, quantitative studies on the relationship between these two aspects are scarce. Therefore, this study investigates the influence of indicators such as photography distance (D), model brightness (l), angle between photography optical axis and the discontinuity to be interpreted (θd), and texture distortion area ratio (tdp), among others, on the interpretability of the 3D models. Furthermore, it delves into the relationships among these indicators and their practical application effects in complex high-steep rock slopes. On this foundation, a novel multi-indicator quality evaluation method for 3D models constructed using UAV photogrammetry is introduced for the first time. This method, based on a composite index model and incorporating empirical approaches, classifies the quality of 3D models into five levels. Guided by the quality evaluation results and taking into account the terrain development and geometric characteristics of discontinuities, a technical framework supporting the acquisition of high-quality 3D models is proposed, known as multi-angle nap-of-the-object image acquisition (MNIA). The research indicates that the 3D models established based on MNIA exhibit significantly reduced texture distortion, leading to a substantial improvement in recognizability, with a goodness rate of 79.98%, far surpassing that of oblique photogrammetry (41.18%). This study provides crucial guidance for obtaining high-quality UAV image in complex terrain environments and holds significant engineering application value in the fine identification and interpretation of rock mass structures on high-steep rock slopes.

Discontinuity development patterns and the challenges for 3D discrete fracture network modeling on complicated exposed rock surfaces

Natural slopes usually display complicated exposed rock surfaces that are characterized by complex and substantial terrain undulation and ubiquitous undesirable phenomena such as vegetation cover and rockfalls. This study presents a systematic outcrop research of fracture pattern variations in a complicated rock slope, and the qualitative and quantitative study of the complex phenomena impact on three-dimensional (3D) discrete fracture network (DFN) modeling. As the studies of the outcrop fracture pattern have been so far focused on local variations, thus, we put forward a statistical analysis of global variations. The entire outcrop is partitioned into several subzones, and the subzone-scale variability of fracture geometric properties is analyzed (including the orientation, the density, and the trace length). The results reveal significant variations in fracture characteristics (such as the concentrative degree, the average orientation, the density, and the trace length) among different subzones. Moreover, the density of fracture sets, which is approximately parallel to the slope surface, exhibits a notably higher value compared to other fracture sets across all subzones. To improve the accuracy of the DFN modeling, the effects of three common phenomena resulting from vegetation and rockfalls are qualitatively analyzed and the corresponding quantitative data processing solutions are proposed. Subsequently, the 3D fracture geometric parameters are determined for different areas of the high-steep rock slope in terms of the subzone dimensions. The results show significant variations in the same set of 3D fracture parameters across different regions with density differing by up to tenfold and mean trace length exhibiting differences of 3–4 times. The study results present precise geological structural information, improve modeling accuracy, and provide practical solutions for addressing complex outcrop issues.

Experimental study on instability mechanism and critical intensity of rainfall of high-steep rock slopes under unsaturated conditions

Two critical factors, namely intense precipitation and intricate excavation, can trigger rock mass disasters in mining operations. In this study, an indoor rainfall system was developed to precisely regulate the flow and intensity of precipitation. A large-scale model experiment was conducted on a self-designed physical simulation experiment platform to investigate the failure and instability of high-steep rock slopes under unsaturated conditions. The real-time reproduction of the progressive failure process in high-steep rock slopes enabled the determination of the critical rainfall intensity and revealed the mechanism underlying slope instability. Experiment results indicated that rainfall may be the primary factor contributing to rock mass instability, while continuous pillar mining exacerbates the extent of rock mass failure. The critical failure stage of high-steep rock slopes occurs at a rainfall intensity of 40 mm/h, whereas a rainfall exceeding 50 mm can induce critical instability and precipitation reaching up to 60 mm will result in slope failure. The improved region growing segmentation method (IRGSM) was subsequently employed for image recognition of rock mass deformation in underground mines. Herein an error comparison with the simple linear iterative cluster (SLIC) superpixel method and the original region growing segmentation method (ORGSM) showed that the average identification error in the X and Y directions by the method was reduced significantly (1.82% and 1.80% in IRGSM; 4.70% and 6.26% in SLIC; 9.45% and 12.40% in ORGSM). Ultimately, the relationship between rainfall intensity and failure probability was analyzed using the Monte Carlo method. Moreover, the stability assessment criteria of rock slope under unsaturated condition were quantitatively and accurately evaluated.

A method to interpret fracture aperture of rock slope using adaptive shape and unmanned aerial vehicle multi-angle nap-of-the-object photogrammetry

The aperture of natural rock fractures significantly affects the deformation and strength properties of rock masses, as well as the hydrodynamic properties of fractured rock masses. The conventional measurement methods are inadequate for collecting data on high-steep rock slopes in complex mountainous regions. This study establishes a high-resolution three-dimensional model of a rock slope using unmanned aerial vehicle (UAV) multi-angle nap-of-the-object photogrammetry to obtain edge feature points of fractures. Fracture opening morphology is characterized using coordinate projection and transformation. Fracture central axis is determined using vertical measuring lines, allowing for the interpretation of aperture of adaptive fracture shape. The feasibility and reliability of the new method are verified at a construction site of a railway in southeast Tibet, China. The study shows that the fracture aperture has a significant interval effect and size effect. The optimal sampling length for fractures is approximately 0.5–1 m, and the optimal aperture interpretation results can be achieved when the measuring line spacing is 1% of the sampling length. Tensile fractures in the study area generally have larger apertures than shear fractures, and their tendency to increase with slope height is also greater than that of shear fractures. The aperture of tensile fractures is generally positively correlated with their trace length, while the correlation between the aperture of shear fractures and their trace length appears to be weak. Fractures of different orientations exhibit certain differences in their distribution of aperture, but generally follow the forms of normal, log-normal, and gamma distributions. This study provides essential data support for rock and slope stability evaluation, which is of significant practical importance.

Multi-source monitoring data helps revealing and quantifying the excavation-induced deterioration of rock mass

There exist many high-steep rock slopes in Southwest China due to the construction of large-scale hydropower projects. The study on excavation-induced damage of high rock slopes is vital for disaster prevention and mitigation. Due to the complexity of high-steep rock slopes, assessing the excavation-induced deterioration of rock mass is often challenging. This study used the space-borne Interferometric synthetic aperture radar (InSAR) and multipoint displacement meters to monitor the slope displacements before and after the excavation. Based on the multi-source monitoring data and the parameter estimation method, we evaluated the changes in rock mass properties due to slope excavation. We employed an improved particle swarm optimization algorithm with dynamic topology and adaptive parameter adjustment and a neural network-based surrogate model in the parameter estimation. The degradation of rock mass strength and stiffness coincides with the increased sensitivity of slope deformation to rainfall infiltration. An in-depth analysis indicates that the absence of vegetation protection and excavation-induced deterioration of rock masses are responsible for the noticeable slope deformation during the rainy season. As slope excavation profoundly influences slope stability and deformation, we should pay closer attention to the excavation way and support style. This study also demonstrates the benefits of using multi-source monitoring data in slope deformation analysis. The findings can aid in comprehending the deformation evolution and instability mechanisms of rock slopes excavated at the hydropower sites, thereby contributing to the prevention and mitigation of landslide disasters.

High Steep Rock Slope Instability Mechanism Induced by the Pillar Deterioration in the Mountain Mining Area

In hilly regions, landslides or slope failures are very common phenomena, when underground mineral resources are excavated. In this study, some landslide disasters in a mountain mining area were analyzed. The engineering geological and instability reason were investigated. The numerical simulation of a high steep rock slope disturbed by a room and pillar mine was established. The failure process of a high steep rock slope induced by the pillar deterioration was analyzed to reveal the characteristics of deformation and sliding. The results show that the pillar plays an important role in maintaining the stability of the slope, if the pillar can support the overlying rock mass, only a tiny deformation will be induced. When the pillar fails and the roof caves, the overlying rock mass above the room and pillar goaf will rapidly subside, and the crack evolution of slope is induced, forming the potential slip surface. The landslide mass gradually moves. When the rock mass at the middle and lower of the slope is squeezed out, slope sliding will be induced. The failure process can be divided into four stages as follow: tiny displacement is caused by the mining, roof collapse is caused by the pillar failure, the potential slip surface is formed from the crack evolution; the slope sliding is induced by the fracturing of rock mass at the middle and lower of the slope.

Application of UAV Digital Photogrammetry in Geological Investigation and Stability Evaluation of High-Steep Mine Rock Slope

For the stability analysis of rock slope, it is very critical to obtain the spatial geometric characteristics of the structural surfaces of the rock mass accurately and effectively. As for a high-steep rock slope of an iron ore mine, in order to solve the problems of inefficiency and high risk of traditional manual geological survey, the geological survey and stability evaluation of the slope was carried out by adopting unmanned aerial vehicle digital photogrammetry (UAV-DP) technology. Firstly, a large number of high-resolution images of the slope were obtained by UAV-DP. Then, the structure from motion (SFM) method was used to construct the fine 3D point cloud model of the slope, which was subjected to coplanarity detection and K-means clustering for identifying the structural surfaces. Finally, the stability and failure model of the slope cut by the structural surfaces are analyzed by using the stereo-projection and discrete element methods. The research results show that the error between UAV-DP and manual measurement is within the acceptable range, which demonstrates the reliability of UAV-DP used in the geological investigation. Furthermore, the stability state and failure model of the slope is also consistent well with the field observation.

Stochastic kinematic analysis of rock slope failure angle based on multi algorithm optimization, a case study of the proposed bridge project

ABSTRACT Due to the randomness and complexity of the discontinuity distribution, it is always complicated to analyse the three-dimensional stability problem of discontinuity-controlled rock slope in the field of engineering geology. Specifically, when restricted by poor sampling conditions, the discontinuity data obtained are very limited. To solve this problem, we propose a stochastic kinematic method to estimate the slope failure angle based on limited data. Taking the high-steep rock slope on the right bank of a proposed bridge as an example, the stochastic kinematic method based on multiple algorithms (Monte Carlo simulation, Latin hypercube, and Bayesian estimation) is used to analyse the failure angles of potentially unstable blocks in two modes of plane and wedge failure. After statistical optimisation, the slope failure angles are determined to be 65.69° (plane failure) and 58.65° (wedge failure); this approach is more objective than the empirical formula method and can be used as the basis for judging the slope stability. The method proposed in this study fully considers the randomness of discontinuity distribution and combination, and can use limited sample data to realise failure angle analysis and stability judgement. The result is important as a reference of significance for engineering construction and disaster prevention.

Investigation on the Seismic Wave Propagation Characteristics Excited by Explosion Source in High-Steep Rock Slope Site Using Discrete Element Method

The influence of seismic waves induced by explosion sources on the dynamic response characteristics of rock slope sites is one of the most important problems affecting engineering construction. To investigate the wave propagation characteristics and attenuation law of seismic waves induced by explosive sources in rock sites from the perspective of time and frequency domains, the high-performance matrix discrete element method (MatDEM) is used to carry out numerical simulation tests on a granite rock medium site. The discrete element model of the high-steep rock slope is established by MatDEM, and the dynamic analysis of the rock medium site is conducted by loading blasting vibration load to generate seismic waves. The results show that the seismic waves in the rock site present characteristics of arc propagation attenuation. The maximum attenuation rate of the dynamic response is the fastest within 0.3 s and 25 m from the explosion source. The slope region can weaken the dynamic response of seismic waves generated by the explosion source. In particular, the high-frequency band (>20 Hz) has an obvious filtering effect. The dynamic response of the P-wave induced by the explosive source is greater than that of the S-wave in the bedrock and surface region. The dynamic amplification effect of the P-wave is greater than that of the S-wave in the slope region. The seismic waves in the slope region show an attenuation effect along the slope surface and have a typical elevation amplification effect inside the slope.

Assessment and prevention on the potential rockfall hazard of high-steep rock slope: a case study of Zhongyuntai mountain in Lianyungang, China

Assessment and prevention on the potential rockfall hazard of high-steep rock slope: a case study of Zhongyuntai mountain in Lianyungang, China

Study on Blasting Technology for Open-Pit Layering of Complex Mine Adjacent to High and Steep Slope

In China, mining blasting vibration has seriously threatened the safety and stability of high and steep rock slopes. In this paper, taking the east mining area of Jianshan Phosphorus Mine as the research background, combined with field survey, field blasting test, numerical simulation and theoretical analysis, we systematically studied the adjacent high-steep rock slope and the layered blasting technology of complex ore. Based on wide hole spacing blasting numerical simulation and field tests, the use of 8 × 4 m hole network parameters, oblique line hole-by-hole initiation method, detonator delay using 35 ms between holes, 65 ms between rows and 500 ms within the holes, the rock mass rate was reduced and the drilling workload was decreased. In addition, regression analysis was carried out on a large amount of vibration test data, and the attenuation law and propagation law of blasting vibration of adjacent high and steep slopes were predicted, which provided a reference for mine production blasting. By establishing a mathematical model of cumulative damage of rock mass blasting, it shows that the depth of impact of mining blasting on the slope of Jianshan open-pit was 0–3.6m, but the blasting did not cause overall damage to the adjacent high and steep slopes. In the future, this model can be used to predict rock damage caused by subsequent blasting.

Bearing capacity behaviour of prestressed anchor cable under slope blasting excavation

The stability of high steep rock slopes directly influences the success or failure of whole engineering construction processes. Slope excavation and reinforcement with prestressed anchor cable can effectively improve the stability of the slope. However, the blasting stress waves have a great impact on the anchor cables that have been installed or are under construction. In this paper, a new simulating method of prestressed anchor cables is proposed for high steep rock slopes in consideration of the construction process and the reinforcement mechanism. And a simple simulating method of slope blasting excavation load is developed. The bearing capacity of prestressed anchor cables under slope blasting excavation is analysed via an ideal generalized slope model based on the left bank slope of the Jinping I hydropower station. The results show that the degree by which the distance from the blasting zone, the damping ratio, the maximum single-shot dose and the grade of the prestressed anchor cable impact the bearing capacity behaviours of the prestressed anchor cable decrease over time. Anchor cables are most prone to vibration failure within 5 m from the outer anchor head. The increase in tensile force is the largest on the anchor head at the slope surface. The impact of the maximum single-shot dose and damping ratio on the small-tonnage anchor cable is greater than that on the large-tonnage anchor cable. The anti-explosion performance of the large-tonnage anchor cable is better than that of the small-tonnage anchor cable. The foundations and experience needed to optimize the parameters of blasting excavation and anchor cable design for similar high-slope projects in China or other regions are presented.

A novel dynamic stability analysis method for jointed rock slopes based on block-interface interaction

The dynamic stability evaluation of jointed rock slopes is a complex problem of solving nonlinear and uncertain systems. The interactive method of partitioned finite element and interface element is applied to the solution of the seismic response of jointed rock slopes under earthquake. The contact status of the weak interlayer can be calculated at each moment by the method. Since the balance of the slope slider can be inferred by contact status on weak interlayer, a novel criterion of rock slope instability based on the contact status of the contact surface is proposed. The criterion not only satisfies the requirement for the sudden change of residual deformation but also meets the completely broken of the weak interlayer. Since the interactive method can still converge in the state of slope failed, an adaptive strength reduction method is proposed to search for the safety factor automatically. To verify the effectiveness of the method, the dynamic stability of a classical rock jointed slope is calculated, and then compared with the result in the reference paper. Moreover, the proposed method is applied to analyze the dynamic stability of a high steep rock slope with complex internal joints and the safety factor is calculated successfully.

Stability Monitoring and Analysis of High and Steep Slope of a Hydropower Station

Slope deformation and failure are major challenges for hydropower station engineering. Taking the left bank slope at the exit of the flood discharge tunnel of the Wudongde Hydropower Station in China as an example, the deformation mechanism of the high-steep rock slope was studied. The height of the slope is about 200 m, which is affected by slope excavation, rainfall, and atomized rain. The results of multipoint displacement meters, surface deformation monitoring, and anchoring stress meters showed that the deformation and deformation rate of the slope have increased dramatically. Through the comprehensive analysis of the slope, it is found that the overall lithology of the slope is poor, the excavation disturbance causes the redistribution of the stress in the slope, and the excavation surface is relatively steep, which provides space for the deformation of the slope rock mass. Unloading relaxation leads to a large number of new fissures in the slope rock mass. These new fissures and fault fracture zones provide convenient conditions for rainfall and atomized rain infiltration. The rainwater infiltrated along the slope surface, formed the seepage field in the slope body, and weakened the rock-soil mass parameters. Meanwhile, saturated runoff is formed on the slope, causing large deformation of the slope rock mass. However, the migration of water in the slope has a time effect, and its influence on the stability of the slope also has a time effect. It is difficult for traditional monitoring methods to monitor the resulting changes in internal sliding force of the slope. Therefore, a remote monitoring and early warning system for landslide anchor cable force was introduced to monitor the slope stability changes caused by the impact of water flow and rainfall infiltration, which provided a reasonable and scientific reference for subsequent slope construction.

Cooperative monitoring and numerical investigation on the stability of the south slope of the Fushun west open-pit mine

The south slope of the Fushun west open-pit mine in China is geologically complex and is a high-steep rock slope. In recent years, a larger deformation has appeared in the south slope, with the gradual formation of a potential landsliding block that is estimated to be over 300 m3. The east and south boundaries of the block have been identified using different monitoring techniques. However the west boundary has not yet been clearly delineated, a situation which undermines safety assessments and the slope management of the mine. The focus of this was on how the microseismic technology, DInSAR technique and the numerical method are used to determine the shape and formation of the west boundary of the potential sliding block. We found that the upper part of west boundary as determined by numerical simulation is concordant with that determined by microseismic monitoring. The surface deformation area coincides with the DInSAR monitoring results and damage area based on in situ observations. Numerical simulation provides supplementary information on the distribution of stress and the formation process of the west boundary that cannot be observed directly on-site. The microseismic monitoring system was able to capture the progressive rupture of the west boundary during the deformation of the block. The cooperative monitoring strategy together with the numerical simulation can delineate the sliding surface and provide a method for a comprehensive assessment of the slope stability of other similar open-pit mines.

Stability analysis of earthquake-induced rock slope based on back analysis of shear strength parameters of rock mass

High-steep rock slopes are much more likely to collapse and form weir body due to earthquake. Converting the weir body to hydraulic engineering is a good way to deal with natural disasters. However, it is difficult to evaluate the stability of earthquake-induced rock slope due to the lack of shear strength parameters of rock mass. Based on three-dimension nonlinear finite elements, deformation reinforcement theory was adopted, in which plastic complementary is used to measure the global stability of slope, and unbalanced forces is utilized to identify the damage region. The shear strength parameters has been determined through back analysis based on stability and failure status before and after earthquake and monitoring data after earthquake. Then the stability evaluation under static conditions, dynamic conditions and rainfall conditions has been carried out respectively. The results show that failure mode of the slope under seismic load is consistent with the actual situation when the lowest material parameters are used. The major failure mode of the slope is sliding along the fault F5, and local collapse of the hanging body at the top of the slope under dynamic or rainfall load. The local stability can be improved effectively by excavating and taking bolt anchorages on the top of the slope.

Stability analysis and reinforcement evaluation of high-steep rock slope by microseismic monitoring

The stability of excavated high-steep rock slopes is most significant in the long-term safety of large-scale hydropower projects. Dagangshan rock slope had an unloading fractured zone (XL-316) and a fault (f231) during excavation, which resulted in a high risk of slope instability. Anti-shear tunnels were constructed for enhancing the overall shear resistance and reinforcing the slope at six different elevations. The microseismic technique was employed to investigate microseismic activities during excavation and after reinforcement. An integrated method of microseismic energy density and the magnitude-frequency relation based on microseismic monitoring was proposed to analyse the stability and reinforcement effect of the slope. During excavation, a large number of microseismic events took place with few low-magnitude events and numerous high-magnitude events. The aggravated damage occurred in the major discontinuities during excavation. The number of low-magnitude microseismic events increased after reinforcement, and the b value obviously increased, which means the slope stability was substantially enhanced. Microseismic activities were evidently reduced, and the accumulated microseismic energy increased slowly. The stresses were transferred towards the edge of the anti-shear tunnel, and a small number of low-energy events occurred. The targeted reinforcement has served well for its purpose and improves the mechanical performance of the discontinuities. The application of the proposed method was verified by 3D RFPA-Centrifuge software. The proposed method can be considered as an effective way to evaluate the reinforcement effect and stability of high-steep rock slopes.

Identifying geomechanical parameters of high cut rock slopes by an improved multi-output support vector machine method

Mechanical parameters of geomaterials are very important to slope stability assessment, design, and safety construction. Back analysis is a practical engineering tool which is commonly used to identify geomechanical parameters based on monitored displacement during slope excavation. The key problem is to establish the nonlinear relationship between geomechanical parameters and the monitored displacements at different excavation steps. This paper presents an improved multi-output support vector machine (MSVM) method which integrates the artificial bee colony algorithm (ABC), numerical analysis, and updated displacement monitoring. MSVM was used to map the complex relationship between geomechanical parameters and slope displacement increments. Training samples were chosen following a Latin hypercube model and their data were applied to numerical model. ABC formed the back analysis, searching for optimal geomechanical parameters based on the MSVM model and field-monitored displacement. The proposed method was applied to a high abutment steep rock slope of the Longtan hydropower station in China and successfully represented the relationship between geomechanical parameters and displacement increments. Updating the displacements at different excavation steps improved the precision of recognition. Reasonable mechanical parameters were identified and adopted in the slope stability analysis.