Landslide Stability Evaluation Research Articles

Integrating data-driven and physically based landslide susceptibility methods using matrix models to predict reservoir landslides

One of the most hazardous types of landslide disasters is reservoir landslides. Spatially predicting the probability of these events when the hydroelectric power station is not impounded can provide a foundation for their prevention and management. A reservoir landslide prediction study was conducted using the reservoir of the Baihetan Hydropower Station in Southwest China as the research area. The study applied both the widely used data-driven landslide susceptibility assessment method and the physics-based landslide stability evaluation approach. Additionally, a matrix prediction model based on a combination of the aforementioned techniques was suggested for reservoir landslide prediction. The applicability of the three approaches was assessed based on the findings of a field investigation of reservoir landslides during the initial impoundment period. The results demonstrated that, in the absence of historical reservoir landslide data, the prediction success rate of the susceptibility mapping method was incredibly poor, at only 30.19%. While the stability prediction approach had an 88.68% success rate, its frequency ratio was only 5.22. The approach significantly overpredicted reservoir landslides, according to a study of the prediction results for regions. On the other hand, the frequency ratio of the matrix prediction model, which combines the two approaches, was 2.24 times that of the stability prediction approach. Thus, the matrix prediction model was found to be more reliable than other methods and capable of predicting the vast majority of reservoir landslides with fewer extremely high probability reservoir landslide areas. To further increase the accuracy of reservoir landslide prediction, it is recommended to use the matrix prediction model.

Evaluating the stability of Outang landslide in the Three Gorges Reservoir area considering the mechanical behavior with large deformation of the slip zone

The large deformation mechanical properties of slip zone soil play an important role in the stability evolution of landslide. The traditional landslide stability evaluation method can only be used to calculate a single stability factor, which cannot dynamically evaluate the landslide stability as it evolves. The large deformation mechanical properties of slip zone soil from Outang landslide in the Three Gorges Reservoir area are investigated by the indoor repeated direct shear test. Based on the damage theory, the shear damage behavior of slip zone soil with large shear displacement is analyzed, and a mechanical model describing the relationship between shear stress and shear displacement in accordance with the mechanical mechanism of landslide is established. Then, the stability of Outang landslide is dynamically evaluated by skillfully combining the mechanical model and the residual thrust method. The results show that the slip zone soil has obvious softening behavior and constant residual strength under the condition of large deformation. The model with clear physical meaning can reflect the large displacement shear mechanical properties of slip zone soil, which is consistent with the test results. The stability factor of Outang landslide gradually decreases and tends to be constant as landslide moves. The mechanical mechanism of the landslide stability evolving with deformation is the strain softening behavior of the slip zone soil, and the mechanical mechanism of the landslide stability evolving with water level is the reduction of effective stress in anti-sliding section under the influence of reservoir water. It is suggested that active measures should be taken in time in the prevention and control of landslide, and the construction of drainage engineering should be paid attention to for large-scale bank landslides.

An application of the high-density electrical resistivity method for detecting slide zones in deep-seated landslides in limestone areas

The deep-seated landslide near the Nanheng town, located in eastern China, is exhibited by the limestone at its bottom. The landslide process is related to the geological succession's weak interlayer covering the bedrock and is characterized by the loose deposit's over-position on the silty clay. A field survey and the 2D high-density electrical method were carried out to detect the overburden thickness, karst cavities and sliding zone location. After confirming the abnormal area, the casing drilling method and numerical simulation were used to verify the geophysical results. The results show that the interpretation results of the slide zone were verified by the FLAC2D simulation on the sliding zone determined by the high-density electrical method and drilling method, and the reliability of the landslide stability evaluation was improved. This research proposes a method for accurately dividing the landslide profile, that is, the high-density electrical resistance tomography (ERT), which is used to preliminarily divide the formation lithology and limestone distribution area, and then the casing drilling method is used to correct the distribution and location of the formation. The sliding zone determined by these two methods can be used in numerical simulations to improve the accuracy of landslide stability evaluations.

Characterizing the 3D hydrogeological structure of a debris landslide using the transient electromagnetic method

Debris landslides are one of the most common types of landslides in the Wenchuan earthquake area. The characteristics of the hydrogeological structure are the basis for landslide stability evaluation and protection treatment. The preferred seepage paths developed in debris landslides control the flow of groundwater and have a direct impact on the soil instability and sliding surface instability. Therefore, it is particularly important to understand the groundwater seepage system. Recently, many joint geophysical surveys have been used to detect the hydrogeological structure of landslides. However, these joint surveys aim to detect structures on a large scale and do not focus on the seepage path systems in debris landslides. It is difficult to detect the 3D structure of the seepage path system in detail, taking into account the portability, penetration, and resolution while meeting the practical needs of landslide prevention. To date, no one method has been identified as the best detection method for characterizing complex 3D hydrogeological structures. To reveal the complex seepage paths efficiently, we investigated a debris landslide in Xishan village, Sichuan Province, China, by using the transient electromagnetic method (TEM), which is a fast and portable method. Additionally, we proposed an effective quasi-3D inversion strategy with kdTree to determine the geoelectric structure and to make a geological interpretation. The interpretation was verified with field engineering surveys, other geophysical surveys, and remote sensing data. The results suggest that the complex 3D structure in this debris landslide is characterized by a dendritic pipe network-like seepage drainage system. In addition, this work assessed the ability to detect different parts of the landslide based on the given resolution. Furthermore, the resolution and detection efficiency of the TEM were compared with those of other geophysical methods. The assessment and comparison demonstrated that the TEM can be used as the main survey method to fulfill the real-world demands of detecting seepage path systems in a debris landslide.

Simultaneous state–parameter estimation of rainfall-induced landslide displacement using data assimilation

Abstract. Landslide displacement prediction has great practical engineering significance to landslide stability evaluation and early warning. The evolution of landslide is a complex dynamic process, and applying a classical prediction method will result in significant error. The data assimilation method offers a new way to merge multisource data with the model. However, data assimilation is still deficient in the ability to meet the demand of dynamic landslide systems. In this paper, simultaneous state and parameter estimation (SSPE) using particle-filter-based data assimilation is applied to predict displacement of the landslide. A landslide SSPE assimilation strategy can make use of time-series displacements and hydrological information for the joint estimation of landslide displacement and model parameters, which can improve the performance considerably. We select Xishan Village, Sichuan Province, China, as the experiment site to test the SSPE assimilation strategy. Based on the comparison of actual monitoring data with prediction values, results strongly suggest the effectiveness and feasibility of the SSPE assimilation strategy in short-term landslide displacement estimation.

TYPICAL APPLICATIONS OF AIRBORNE LIDAR TECHNOLAGY IN GEOLOGICAL INVESTIGATION

Abstract. The technology of airborne light detection and ranging (LiDAR), also referred to as Airborne Laser Scanning, is widely used for high-resolution topographic data acquisition (even under forest cover) with sub-meter planimetric and vertical accuracy. This contribution constructs the real digital terrain model to provide the direct observation data for the landscape analysis in geological domains. Based on the advantage of LiDAR, the authors mainly deal with the applications of LiDAR data to such fields as surface land collapse, landslide and fault structure extraction. The review conclusion shows that airborne LiDAR technology is becoming an indispensable tool for above mentioned issues, especially in the local and large scale investigations of micro-topography. The technology not only can identify the surface collapse, landslide boundary and subtle faulted landform, but also be able to extract the filling parameters of collapsed surface, the geomorphic parameters of landslide stability evaluation and cracks. This technology has extensive prospect of applications in geological investigation.

Influence of uncertainty in the initial groundwater table on long-term stability of reservoir landslides

The seepage calculation of water fluctuation is the crucial precondition for landslide stability evaluation. It is controlled by the initial condition, boundary condition, and soil or rock structure as well as geotechnical parameters. Although the geotechnical parameters and boundary condition have greater influence on seepage and the stability of landslides, the role of the initial groundwater position cannot be ignored. To investigate the influence of an initial groundwater table on landslides, especially the influence of cyclical reservoir water fluctuation on their long-term stability, seven different methods to determine the initial groundwater table were proposed in the presented study, among which one is the actual groundwater table, and the other six are obtained with simplified methods. According to the results of the calculations, at the beginning, there is some difference in the factor of safety among different initial groundwater tables. The maximum value of relative tolerance reduces to less than 1.0 % 160 days later. After a filling–drawdown cycle, the relative tolerance of all methods reduces to less than 0.8 %, which could be ignored. It is also observed that, the closer the hydraulic gradient of the proposed initial groundwater table is to the actual condition, the smaller is the relative tolerance. Therefore, to study the influence of cyclical reservoir water fluctuation on landslide long-term stability, the initial groundwater table could be proposed as (1) equal to reservoir water level and (2) on a straight line with the hydraulic gradient equal to the weighted average of actual groundwater table for simplification.

A 2D integrated FEM model for surface water–groundwater flow of slopes under rainfall condition

Numerical modeling of water infiltration in slopes under rainfall conditions, especially under rainstorm conditions, is a fundamental problem for slope stability assessment. To obtain representative results, surface water–groundwater flow models are incorporated in the simulation. Based on finite element representation of Richards’ equation and of kinematic wave equations, an integrated 2D numerical model (IMCR2D) of the surface water–groundwater system was established. The model has a symmetrical matrix that modifies the flux boundary according to the runoff solution on the slope. IMCR2D was verified using two laboratory experiments, and it showed good agreement with numerical and experimental results. Additional numerical examples were used to study the effect of flux supply from runoff on infiltration. In comparison with SimMd (an existing method), IMCR2D displayed advantages in cases where surface runoff develops in an upper low-permeability section of the slope and flows down into a high-permeability section of the slope. To illustrate the advantages of the new method, the seepage field and stability condition of a case study in the Three Gorges Hydroelectric Reservoir were analyzed using IMCR2D and SimMd. The deformation of a landslide in part reflects its stability, and therefore, we also used displacement monitoring data to estimate the variation of stability conditions from that aspect. Comparison of the two numerical models indicated that flux supply greatly affects the seepage field, and that rainfall plays an important role in landslide stability evaluation, but only when considering flux supply from upper slope surface runoff.

Landslide stability evaluation using high-resolution satellite SAR data in the Three Gorges area

Because of its centimetre-level precision, SAR interferometry (InSAR) has been widely recognized as an effective tool for large-area deformation mapping. However, applications of InSAR technology are limited by temporal–geometric decorrelation and atmospheric disturbance. Large-field displacement could be underestimated as a result of these limitations. A point-like target offset tracking (PTOT) method that solely uses SAR pixel amplitude information through highly accurate image matching can measure 2D displacements in the azimuth and range directions. This method is minimally affected by decorrelation and weather, and it is more suitable for mapping large displacements. In this study, landslide-prone areas were identified using high-resolution TerraSAR-X InSAR data pairs with short normal baselines and temporal baselines covering Zigui County in the Three Gorges area, and the PTOT method was applied to study potential landslides using image pairs with long temporal baselines. An estimate of the cumulative deformation was given. Time series displacements measured at corner reflectors and point-like targets were analysed. The feasibilities of landslide detection using DInSAR and PTOT methods with high-resolution SAR images were then evaluated and summarized.

How to Use COMSOL Multiphysics for Coupled Dual-permeability Hydrological and Slope Stability Modeling

Preferential flow paths, such as cracks, macropores, fissures, pipes etc. are common features of highly heterogeneous slopes. During intense rainstorms, preferential flow has a significant influence on subsurface flow and slope stability. Dual-permeability models are widely used to simulate preferential flow, but have not been incorporated into hydro-mechanical models. In this study, the COMSOL Multiphysics software was used to couple a dual-permeability model with a soil mechanics model for landslide stability evaluation on a hillslope scale with examples of up to 100m spatial scale. Detailed information is provided on how to incorporate current hydrological and soil mechanics theories into COMSOL. The model is benchmarked against two existing solutions and is applied to evaluate the effect of preferential flow on slope stability as an example.

Deformation characteristics and failure mode of the Zhujiadian landslide in the Three Gorges Reservoir, China

Water impoundment of the Three Gorges Reservoir has induced more than 5,000 landslides or potential landslides. These are huge threats to the safety of the dam and the people living in the reservoir area. The deformation characteristics and failure mode of the landslides are important factors in landslide stability evaluation and reinforcement design. The work reported in this paper used the Zhujiadian landslide as an example to study the deformation characteristics and failure mode of the landslides in the Three Gorges Reservoir region. Field investigations were conducted to analyze the structure of the landslide. Then the deformations of the landslide were observed using an integrated monitoring system, including extensometer monitoring for crack development, GPS monitoring for surface displacement, and inclinometer monitoring for internal displacement. The results obtained suggest that the Zhujiadian landslide is a multi-rotational landslide containing three main rotational sub-landslides at present. The deformation and failure of this landslide have developed from front to back. The failure of the front part opens up space for the back part to slide forward into. The coupled actions of the reservoir water and rainfall have led to the failure of the Zhujiadian landslide. Finally, a risk evaluation of the water surge potentially generated by the landslide was conducted by calculating the maximum wave height at the opposite side of the river. The findings of this paper provide some useful information for the stability evaluation and reinforcement design of landslides in similar geological settings in the Three Gorges Reservoir area and in other parts of the world.

GIS is Applied to the Landslide Stability Evaluation - A Case Study of Erman Mountain Landslide

The geological disaster is one of the important research contents of the field of Earth Science. In this paper, the method of theoretical knowledge,field surveys and laboratory experiments is adopted.The Erman Mountain in Hanyuan County is the research object.Analysis the environmental conditions,development characteristics and mechanism. Select the characters of landslide, geological structure, elevation, slope, slope, earthquake, rainfall and other factors as analysis variables. Combine GIS with fuzzy mathematical evaluation method, develop the landslide stability evaluation plug-in and then divide the risk regionalization of study area, in order to avoid occurrence of geological hazards in the area, reduce casualties and property losses. The results show that The occurrence of landslide areas are mainly concentrated in the elevation at about 1600 m and 30° ~ 50° slope area.With the increase of height and slope, the possibility of landslides is increasing.

An Approach for Landslide Stability Evaluation by Numerical Method

For numerical simulation, the shear strength reduction technique (SSRT) is often used to evaluate slope or landslide stability. According to numerical computation results of slopes or landslides analyzed by SSRT, it can be found that with increase of the shear strength reduction factor, some of the soil elements will yield gradually to form a connected plastic zone, which is the potential slip surface of the slope or landslide. In view of the plastic resistance of soils, formation of the connected plastic zone does not always indicate that the landslide is about to failure. Other auxiliary criterion is necessary to predict whether a slope or landslide is in a critical state or not. Here, difference of the incremental percent of horizontal displacement of the outcropping slip surface node is regarded as the auxiliary indicator to distinguish the critical state of slopes or landslides after formation of the potential slip surface. With the ideas mentioned above, stability of a fossil landslide, Xietan landslide has been analyzed for the natural and the long-term reservoir water level conditions. Factors of safety of Xietan landslide by the numerical method have been compared with that by the limit equilibrium method, which indicates that the method used here for evaluating stability of Xietan landslide is feasible. Because numerical method has more advantages over the limit equilibrium method, the approach for evaluating stability of landslide here can be applied to more complicated or three-dimensional landslides or slopes further.

Landslide stability evaluation for Hancheng electric plant applying AE activities

Landslide stability evaluation for Hancheng electric plant applying AE activities