Landslide Stability Research Articles

Analyzing successive landslide dam formation by different triggering mechanisms: The case of the Tangjiawan landslide, Sichuan, China

The catastrophic Tangjiawan landslide, triggered by the 2008 Wenchuan earthquake, blocked the Duba River, impounding one of the most dangerous coseismic barrier lakes in Beichuan, China. The lake was drained by an artificial spillway within one month after the earthquake to minimize the potential dam-breach flooding risk. However, on September 5, 2016, this landslide was reactivated and dammed the river again, creating a 20-m high dam at the same location and resulting in the formation of a barrier lake with a volume of 0.6 million m3. The day after the event we carried out a field investigation of the landslide and obtained a high-resolution image and DEM using UAV. The satellite images from 2005, 2008, 2010 and 2015 were also collected to analyze the evolution of the landslide. Together with multi-temporal DEMs, the geometry and volumes of the displaced mass and the landslide dams and barrier lakes were calculated using image interpretation and 3D spatial analysis with GIS. This landslide is of great scientific interest, as it presents a good example of multiple reactivation of a pre-historical giant landslide under different triggering conditions: a reactivation of an older landslide during the Wenchuan earthquake, and a second reactivation during a rainfall event several years later. Meanwhile from the hazard assessment and prevention perspective, it is also representative as it dammed the river twice in 2008 and 2016, posing threats to both upstream and downstream areas. We infer that the successive landslides in this region could be caused by the strong tectonic activities: including earthquakes and high average uplifting rate. The results of landslide volume analysis using multi-temporal DEMs, contribute to the landslide mechanism analysis, and suggest that the landslide volume estimation is effected by the landslide type, landslide rupture surface location, and resolution of DEM. We also compare the performance of different empirical models of landslide stability and dam-breach flood parameters and discuss their application during the quick assessment of the potential hazard of the landslide dams. Generally, the successive landslide dams at the Tangjiawan site are caused by the successive landslide reactivations on an anti-dip slope controlled by strong tectonic activity and river erosion, involve with a mass of loose materials of previous landslide deposition, and possess high flood risk to the downstream area. The experience gained in this work can be used to assist the hazard assessment and the planning of the emergency measures for similar landslide dams in the future.

The response of pore water pressure to snow accumulation on a low-permeability clay landslide

A snowpack is known to affect landslide stability as the snow loading changes. Furthermore, the snowpack can have effects on the hydrological behavior in the landslide mass. To clarify the response of pore water pressure to snow loading, continuous field-based monitoring of hydraulic and meteorological factors in landslides was conducted for a deposit of extremely low-permeability “quick clay” in Mid-Norway. The pore water pressure increased during every snow-covered period. The pressure exhibited little response to meltwater and/or rain, but corresponded closely to changes in snow accumulation. The increase in pore water pressure during the snow-covered period was considered to be excess pore water pressure generated by undrained snow loading on the extremely low-permeability quick clay. The pore water pressure displayed a positive linear relation with the snow load, and the ratio of the increase in the pore water pressure to the snow load (rusnow) was 0.49–0.53. These values show that approximately half of the snow load contributed to the excess pore water pressure. Continuous field-based monitoring was also conducted for another landslide in relatively high-permeability deposits in Japan, where the pore water pressure showed a relatively low rusnow of about 0.15 and a different timing of the pressure peak. This comparative result indicates that the response characteristics of pore water pressure to the snow loading are strongly affected by the permeability of the landslide mass. Although the excess pore water pressure generated by the snow load theoretically had a negative effect on the slope stability, the value of excess pore water pressure at the monitored landslide was relatively too small to affect its stability.

The influence of the second row of piles in double-row pile retaining walls with the stabilization of landslide

In the practice of designing anti-landslide pile structures along with the single-row walls find use in General multi-row two-row and retaining walls. This assumes that the second row of piles will greatly enhance the bearing capacity of retaining structure. The joint work of the piles in the rows and methods of their calculation are presented in a number of works of domestic and foreign. At the same time conditions the most effective use of the second row in the double row pile retaining walls remain to be studied. Since double-row pile retaining wall, the combined grillage represents a frame of flexible piles on an elastic Foundation, the load distribution between the piles from the existing on the wall of landslide pressure will depend on the flexibility of the piles, the ordinates of the load from the landslide pressure on the first row, the soil properties of landslide slope. To determine the valid picture of the work of anti-slide pile structures was tasked to establish the role of the second row in the work of double-row pile retaining walls. The article presents the results of analytical studies frame construction flexible piles, the combined grillage hard, perceiving landslide pressure. Effective capacity utilization of the second row of piles was assessed using the utilization of the bearing capacity of piles second through 4,000 different designs double row of walls made of piles of various cross-sections, length, their reinforcement, the depth of application of landslide pressure, as well as with different variants of soil conditions. Due to the significant complexity of the implementation many variants of the analytical calculations were carried out with the use of computers.

Landslide stabilization with geogrids in Lech: a pioneer project 25 years ago

This article is not available for publication.

A case study of rainfall‐triggered slope instability using projected extremes

AbstractIn the past years due to climate change the region of South‐East Europe is subjected to extreme weather events with intense rainfall fallowed by activation or reactivation of landslides. In this paper a rainfall‐triggered landslide is investigated on extreme precipitation estimates. Hence, the behaviour of the slope is controlled by the hydro‐mechanical conditions and soil‐atmosphere interaction. In this case study a slope stability of a natural landslide is calculated for projected rainfall of 10 mm/h with 24‐hour duration. In such scenarios due to the excess pore‐water pressure even deep‐sited landslides beside local can exhibit global instability. This study aims to quantitatively assess the impact of intense rainfall on the landslides. The extreme precipitation pattern is considered as loading condition in a fully coupled hydromechanical finite element simulation, where the displacements, matric suctions, and suction stresses are calculated. The results indicate that intense rainfall leads to fast pore‐water pressure build‐up resulting in local strength reduction of the slope. In general, the findings urge to reassess the existing risk maps with more detailed models and higher prognosed precipitation.

Analysis of the causes and effects of landslides in the Carpathian flysch in the area of Milówka and evaluation of their prevention methods

Abstract The paper presents a comprehensive study on the causes and effects of landslides occurring in the gmina Milówka (gmina is the administrative district in Poland, similar to a commune or municipality) from 1947 until today. The analysis includes the identification of probable causes of landslides and a discussion of possible remedial methods, including preventive ones. The following were considered: results of laboratory, geophysical and seismic tests; meteorological data; vegetative and transpirational properties of plants and agricultural crops; intensity of farming; forest clearance. Attention was also paid to the tree-ring eccentricity among spruces. Additionally, a numerical analysis of the current landslide stability was carried out in the Z_Soil program. Finally, it was found that determining the exact value of the stability coefficient is not possible due to the numerous assumptions necessary for the numerical analysis. However, it is possible to predict with high probability which of the slopes are threatened with landslides.

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.

State fusion entropy for continuous and site-specific analysis of landslide stability changing regularities

Abstract. Stability analysis is of great significance to landslide hazard prevention, especially the dynamic stability. However, many existing stability analysis methods are difficult to analyse the continuous landslide stability and its changing regularities in a uniform criterion due to the unique landslide geological conditions. Based on the relationship between displacement monitoring data, deformation states and landslide stability, a state fusion entropy method is herein proposed to derive landslide instability through a comprehensive multi-attribute entropy analysis of deformation states, which are defined by a proposed joint clustering method combining K-means and a cloud model. Taking Xintan landslide as the detailed case study, cumulative state fusion entropy presents an obvious increasing trend after the landslide entered accelerative deformation stage and historical maxima match highly with landslide macroscopic deformation behaviours in key time nodes. Reasonable results are also obtained in its application to several other landslides in the Three Gorges Reservoir in China. Combined with field survey, state fusion entropy may serve for assessing landslide stability and judging landslide evolutionary stages.

Failure Mechanism and Stability Analysis of an Active Landslide in the Xiangjiaba Reservoir Area, Southwest China

Dam construction for hydropower development is a very important subject all around the world, especially in developing countries due to energy crises. Filling of reservoir lakes may trigger or reactivate landslides in reservoir area. Active landslides in populated districts in the Xiangjiaba Reservoir area have become a striking problem for residents, local government and construction engineers. The key objective of this study is to analyze the role of reservoir filling and fluctuation in the activation/reactivation of the landslide as well as the mechanism of landslide from microstructures of pre-sheared slip surface. A large active landslide with a total volume of 1.25 Mm3 at the left margin of Jinsha River in Pingshan County of Sichuan Province, Southwest China, was selected as a case study. Field investigation, field monitoring and laboratory tests were carried out to find out the failure mechanism and the stability of the active landslide. The shear strength test and stability analysis confirm that the water level fluctuations have an adverse effect on slope stability. It is obvious from microstructure analysis that the clay minerals contribute to down-slope movement at micro-scale as well as presence of expansive minerals (e.g., montmorillonite) decreases the strength of soil due to water level rise.

Retrieval of time series three-dimensional landslide surface displacements from multi-angular SAR observations

A major limitation for wide application of Synthetic Aperture Radar (SAR) remote sensing in mapping landslide surface displacements is the intrinsic gap between the ultimate objective of measuring three-dimensional displacements and the limited capability of detecting only one or two-dimensional displacements by repeat-pass SAR observations of identical imaging geometries. Although multi-orbit SAR observations of dissimilar viewing geometries can be jointly analyzed to inverse the three-dimensional displacements, the reliability of inversion results might be highly questionable in case of continuous motion because of the usually asynchronous acquisitions of multi-orbit SAR datasets. Aiming at this problem, we proposed an approach of retrieving time series three-dimensional displacements from multi-angular SAR datasets for step-like landslides in the Three Gorges area in this article. Firstly, time series displacements of a common ground target in the azimuth and line-of-sight (LOS) direction can be estimated using traditional methods of SAR interferometry (InSAR) and SAR pixel offset tracking (POT), respectively. Then, a spline fitting and interpolation procedure was employed to parameterize the displacement history in the sliding/dormant periods of step-like landslides and estimate displacements from multi-angular observations for identical date series. Finally, three-dimensional displacements can be inverted from these synchronized multi-angular measured displacements in traditional ways. As a case study, the proposed method was applied to retrieve the three-dimensional displacements history of the Shuping landslide in the Three Gorges area, China. Comparisons between SAR-measured displacements and measurements of global positioning system (GPS) showed good agreement. Furthermore, temporal correlation analyses suggest that reservoir water level fluctuation and rainfall are the two most important impact factors for the Shuping landslide stability.

FAILURE MECHANISM ANALYSIS CONSIDERS THE HYDROLOGICAL AND SEISMIC CONDITIONS AT CHASHAN SITE IN CENTRAL TAIWAN

Abstract. The investigation results of large-scale landslides in the central part of Taiwan from Central Geologic Survey identified a new, largescale landslide in the Chashan Village of Alishan Township, Chiayi County (ID: D160) which has the potential to influence the safety of Chashan Village residents. In coordination with the surface geological survey, Chashan site can be divided into three potential sliding areas (zones A, B and C). The paper uses GeoStudio for evaluating the stability of different hydrological and seismic scenarios. The results of scenario simulation show that: (1) In the normal and high water level scenarios, the safety factor obtained in zone A is greater than 1.0, and the initial judgment belongs to the stable state; (2) In the earthquake scenarios, the A4 potential sliding mass in zone A will be collapsed; (3) Through the scenario simulation, when the water level in zone A rises more than 25 meters or the PGA exceeds 160 gal, it is possible to cause the collapse of A4 potential sliding mass. The result of the study will contribute that the complex phenomenon between the stability of landslides and hydrogeological conditions can be revealed and clarified through the detailed study on the hydrogeological investigation, observation and the numerical simulation.

A Stability Evaluation Method of the Subgrade Loess Landslide

Landslide is the inevitable geological hazard in all kinds of linear engineering. Based on the principle of fuzzy transformation and the principle of maximum membership degree, a method for the landslide stability was established. The indexes of landslide macroscopic deformation and slope characteristics were chosen as the evaluation factors, which were divided into stability, basic stability, instability and extreme instability. The weights were determined according to the scoring of the present experts. Landslide of the railway station was evaluated by this method, the result is [0.20, 0.23, 0.32, 0.24]. The stability level is unstable. The accuracy of this method is proved by comparing with the standard method.

Matrix permeability of reservoir rocks, Ngatamariki geothermal field, Taupo Volcanic Zone, New Zealand

The Taupo Volcanic Zone (TVZ) hosts 23 geothermal fields, seven of which are currently utilised for power generation. Ngatamariki geothermal field (NGF) is one of the latest geothermal power generation developments in New Zealand (commissioned in 2013), located approximately 15 km north of Taupo. Samples of reservoir rocks were taken from the Tahorakuri Formation and Ngatamariki Intrusive Complex, from five wells at the NGF at depths ranging from 1354 to 3284 m. The samples were categorised according to whether their microstructure was pore or microfracture dominated. Image analysis of thin sections impregnated with an epoxy fluorescent dye was used to characterise and quantify the porosity structures and their physical properties were measured in the laboratory. Our results show that the physical properties of the samples correspond to the relative dominance of microfractures compared to pores. Microfracture-dominated samples have low connected porosity and permeability, and the permeability decreases sharply in response to increasing confining pressure. The pore-dominated samples have high connected porosity and permeability, and lower permeability decrease in response to increasing confining pressure. Samples with both microfractures and pores have a wide range of porosity and relatively high permeability that is moderately sensitive to confining pressure. A general trend of decreasing connected porosity and permeability associated with increasing dry bulk density and sonic velocity occurs with depth; however, variations in these parameters are more closely related to changes in lithology and processes such as dissolution and secondary veining and re-crystallisation. This study provides the first broad matrix permeability characterisation of rocks from depth at Ngatamariki, providing inputs for modelling of the geothermal system. We conclude that the complex response of permeability to confining pressure is in part due to the intricate dissolution, veining, and recrystallization textures of many of these rocks that lead to a wide variety of pore shapes and sizes. While the laboratory results are relevant only to similar rocks in the Taupo Volcanic Zone, the relationships they highlight are applicable to other geothermal fields, as well as rock mechanic applications to, for example, aspects of volcanology, landslide stabilisation, mining, and tunnelling at depth.

Stability Analysis of Partially Submerged Landslide with the Consideration of the Relationship between Porewater Pressure and Seepage Force

For partially submerged landslides, hydrostatic and hydrodynamic pressures, related to water level fluctuation and rainfall, are usually expressed in the form of porewater pressure, seepage force, and buoyancy. There are some connections among them, but it is very easy to confuse one force with another. This paper presents a modified mathematical expression for stability analysis of partially submerged landslide and builds the relationship between porewater pressures and buoyancy acting on the underwater zone of partially submerged landslide and the relationship among porewater pressures, seepage force, and buoyancy acting on partially submerged zone. The porewater pressures acting on the underwater slice are calculated using hydrostatic forces, and the porewater pressures acting on the partially submerged slice are estimated by an approximation of equipotential lines and flow lines under the steady state seepage condition. The resultant of the porewater pressures acting on the underwater slice equals the buoyancy, and that acting on the partially submerged slice is equivalent to the vector sum of seepage force and the buoyancy. The result shows there are two equivalent approaches for considering the effect of water on landslide stability in the limit equilibrium method. One is based on total unit weight and porewater pressures, and the other is in terms of the buoyant weight and the seepage force. The study provides a modified model for simplifying the complex boundary porewater pressures in limit equilibrium analysis for the stability of the partially submerged landslide.

基于FLAC<sup>3D</sup>的夏日滑坡稳定性研究分析

基于FLAC<sup>3D</sup>的夏日滑坡稳定性研究分析

Effect of drag force on stability of residual soil slopes under surface runoff

ABSTRACTTo investigate the effect of drag force on stability of residual soil slopes, a modified approach based on the limit equilibrium method is proposed by establishing a nonlinear coupled mathematical model to calculate the seepage velocities in soils and the runoff velocities at a fluid–solid interface. In this mathematical model, the Navier–Stokes equation and Brinkman-extended Darcy equation are used to describe the incompressible surface runoff and seepage in soils, respectively. Then, the drag force can be derived by adopting Newton's law of internal friction, and the factor of safety (FOS) of residual soil slopes considering drag force can be calculated based on the limit equilibrium method. The modified approach was applied to analyse the stability of rainfall-induced landslides in residual soils in Nanjiang, Sichuan, China, 2011. We found that the runoff depth can significantly control the FOS of the residual soil slopes and cause slope failures. The results of sensitivity analysis highlight the significance for considering drag force due to surface runoff when calculating the FOS of the residual soil slope. The FOS obtained from the modified approach is more reasonable, and this modified approach also can be used for evaluating or predicting rainfall-induced slope instability in residual soils.

The problem of stabilization of landslides in glaciotectonically disturbed areas. Case study: road engineering structure

The process of the construction of engineering structures situated within glacitectonically disturbed areas cause the necessity to link engineering operation with knowledge of geological processes. One of the examples of such a structure was the construction of the west bypass of Zielona Góra. The roadworks were connected with the necessity of deep excavations into glacitectonically disturbed soil structures. This caused intense changes in the soil mass and - as a consequence - loss of slope stability and the construction of landslides. At the construction stage numerous landslides were already active, which additionally increased during intensive road use. In spite of technical stabilization, there was a risk of loss of slope stability, which is a consequence of stresses in soil mass and engineering activity. This article presents the results of the monitoring of the slope stability during intensive road exploitation.

Influence of lime stabilization on shear strength parameters of silty clay soil

Lime soil stabilization is a well-known and often used method. One of the methods of landslide stability improvement is changing soil with materials that have better physical and mechanical characteristics. In most of the methods for determining slope stability, the main input data are internal friction angle and cohesion. The main objective of this paper was to find out if the sampled silty clay soil was suitable for lime stabilization, and to get the values of shear strength parameters from soil samples with and without added lime. The results showed that by increasing lime content, internal friction angle rises, while cohesion values decrease, as well as deformations, all the way to 15% of lime by mass. The changes in internal friction angle, cohesion and deformations were most noticeable between 0 and 5% of added lime. Samples that endured the largest pressures were those containing 10% of lime.

Evaluation criteria of landslide stability

The theoretical issues related to the definition of the landslide movement for rectilinear and circular cylindrical sliding surfaces are considered. Based on the concepts of the theory of measurement errors, an analysis of the impact of the parameters on the landslide velocity is performed. The formulas obtained allow us to calculate the speeds of landslides during seismic and atmospheric action.

Sistematizacija analitičkih i numeričkih metoda proračuna stabilnosti klizišta

According to the analysis of a large number of scientific papers, the authors of the paper presented their own original systematization of the analytical and numerical methods of landslide stability calculation, with a large part of them still to be further improved, implemented and tested on complex 3D landslide models. Methods for calculating the stability of the landslide are classified into five groups: analytical single-step, analytical multi-step (iterations of sliding surfaces), numerical multi-step (iterations of sliding surfaces), numerical incremental-iterative (nonlinear) analysis and numerical incremental-iterative (nonlinear) analysis, applying numerical integration in the time domain. By using the systematization method of calculating the stability of the landslide it can be very effective to consider which type of method is optimal for landslide analysis and which type of method should be considered in the phase of preliminary and final analysis for scientific research and expert projects.