Artificial Landslide Research Articles

Artificial landslides monitoring based on wireless ranging using a nonlinear least squares estimation

A wireless ranging system including six base stations and two observation stations was employed to monitor the surface displacement of an artificial landslide occurring in Nanjing Tangshan Town, southeast China, which was simulated by mechanical mining on a hill of artificial accumulation. The range data collected by both base stations and observation stations was devoted to construct observation. Moreover, the nonlinear least squares estimation method was used to obtain the displacement on account of nonlinearity in observation equation. Meanwhile, the DOP values derived from design matrix of observation equation was used to evaluate the spatial configuration of the base stations. The results from the wireless ranging system show that the occurrence of the artificial landslide was detected, and the trajectory of the landslide was showed through continuous observation. These findings demonstrate that the experimental design, wireless ranging system, as well as the displacement estimation algorithm can provide effective means to monitor and evaluate the status of landslides and unstable slope effectively in engineering applications.

Dynamics of pore water pressure at the soil–bedrock interface recorded during a rainfall-induced shallow landslide in a steep natural forested headwater catchment, Taiwan

The generation of subsurface saturation is highly related to shallow landslide initiation. Although many studies have relied on experiments to report the generation processes of subsurface saturation that triggers shallow artificial landslides, studies based on detailed in situ monitoring data sets or pre- and post-slide data sets for a natural landslide are still rare. This study recorded the dynamics of pore water pressure at the soil–bedrock interface with high spatiotemporal resolution concurrently with the occurrence of a shallow landslide in a steep natural forested headwater catchment. Using event-based analyses, we explored patterns in the generation of subsurface saturation and other main hydrological factors triggering the landslide. The landslide was not induced by the event with the greatest rainfall amount but by a smaller event with intermittent rainfall over a long duration of 9 days and intense rainfall from the seventh day. The landslide occurred as a result of record-high subsurface saturation generation with a spatial mean pore water pressure of 17.5 cmH2O and a saturation ratio of 0.89 at the site. It was attributed to the landslide event that began during wet conditions with a mean pore water pressure of 7.2 cmH2O. Although the rainfall contributed a near-uniform increase in pore water pressure at all measurement points, high pore water pressure was recorded within the landslide area in the downslope area of the site where subsurface saturation existed perennially. Heterogeneous distribution of subsurface saturation, including perennial and ephemeral saturation, was likely related to the extent of the landslide area. In addition, the two biggest events in the observation period caused subsurface displacements in the year before the landslide. The subsurface displacements weakened the geological structure and enlarged the amount of perennial saturation, which all reduced slope stability and facilitated the landslide. At least two origins of subsurface saturation should be a general feature for a headwater catchment (e.g., vertically downward infiltrated water and an upward rise in groundwater), and the different generation processes of subsurface saturation should be considered separately in future stability analysis models or disaster warning systems for shallow landslides.

Mogućnost upotrebe zgure visoke peći kao agregata u betonu

Large quantities of material are obtained for waste disposal in industrial production of basic iron. It is a long habit of waste management after industrial production of base iron without previous processing or selection. On the places of waste disposal, the contamination of soil and/or water is evident, and it resulted in permanent land degradation and frequent formation of artificial landslides. These facts gave birth to the idea to investigate the possibility of using industrial by-products of iron manufacturing for construction purposes, i.e. concrete aggregate. In order to determine the possibility of blast furnace slag as concrete aggregate, it was necessary to examine physical and chemical properties of slag, and thereafter to prepare concrete samples. The use of slag from ''Željezara' Works (Arcelor Mital, Zenica) was experimentally proved as possible concrete aggregate, which could lead to reduction of this waste material, while preserving natural aggregate that was often used in production of concrete. By using slag in concrete production, environmental pollution will be reduced, and on the other hand, nature will remain 'untouched', since smaller quantities of natural aggregate will be used.

Monitoring and Measurement of an Artificial Landslide Dam Using UAV Images and Image-Based Modeling

Because of heavy rains or earthquakes, landslide and debris flows may flow into rivers and block river channel so to become a landslide dam. Due to the relatively loose nature and the absence of proper engineering spillway, landslide dams are often vulnerable to catastrophic failure by overtopping and breaching, and cause severe flooding in downstream area possibly with serious casualties, such as life loss and property damage. Therefore, the technology development of time-effective monitoring landslide dams becomes an important issue in disaster mitigation. However, the monitoring and assessment of landslide is often difficult due to the timeliness and effectiveness over an unreachable location. Since the timing of dam failure and the magnitude of the resulting flooding downstream are highly affected by the landslide dam size and geometry, the three-dimensional measurement of landslide dam is an essential task in the mitigation act following the occurrence of a landslide lake. Taking responsiveness and efficiency into consideration, this research proposed a process for the monitoring and assessment of landslide dam by employing unmanned aerial vehicles (UAVs) for aerial surveying and Image based modeling (IBM) for aerial surveying and a 3D model reconstruction of an artificial landslide dam built in a real Landou stream within Hui-Sun experimental forest in Nantou, Taiwan, as a full-scale on-site experiment. The result shows that a 3D terrain model can be successfully constructed based on the UAV images through IBM process. Especially, the volume and stability of landslide dam is the most urgent information needed to be acquired for mitigation strategy making so that the failure of landslide dams due to dam breach and erosion by the overflow stream can be predicted and prepared.

Using Custom Fiber Bragg Grating-Based Sensors to Monitor Artificial Landslides.

Four custom fiber Bragg grating (FBG)-based sensors are developed to monitor an artificial landslide located in Nanjing, China. The sensors are composed of a rod and two FBGs. Based on the strength of the rods, two sensors are referred to as “hard sensors” (Sensor 1 and Sensor 2), the other two are referred to as “soft sensors” (Sensor 3 and Sensor 4). The two FBGs are fixed on each sensor rod at distances of 50 cm and 100 cm from the top of the rod (an upper FBG and a lower FBG). In the experiment presented in this paper, the sensors are installed on a slope on which an artificial landslide is generated through both machine-based and manual excavation. The fiber sensing system consists of the four custom FBG-based sensors, optical fiber, a static fiber grating demodulation instrument (SM125), and a PC with the necessary software. Experimental data was collected in the presence of an artificial landslide, and the results show that the lower FBGs are more sensitive than the upper FBGs for all four of the custom sensors. It was also found that Sensor 2 and Sensor 4 are more capable of monitoring small-scale landslides than Sensor 1 and Sensor 3, and this is mainly due to their placement location with respect to the landslide. The stronger rods used in the hard sensors make them more adaptable to the harsh environments of large landslides. Thus, hard sensors should be fixed near the landslide, while soft sensors should be placed farther away from the landslide. In addition, a clear tendency of strain variation can be detected by the soft sensors, which can be used to predict landslides and raise a hazard alarm.

ON GEOMORPHOLOGIC ASPECT OF RADIOWASTES DISPOSAL INTO OCEAN-BED (PAPER 2. THE OUTLINES OF NEW RD TECHNOLOGY)

The disposal of the exhaust nuclear fuel and radiowastes into the ocean-bed under clastic deposits on the continental margin may serve as alternative to the established practice of land burial. The landslides are an important lithodynamic factor within this geomorphologic zone. The artificial landslides may form the clastic deposits flow to cover the storage containers previously located on the bottom. The choice of appropriate places in the ocean is practically indefinite.

Evaluation of slope stability by finite element method using observed displacement of landslide

To monitor land deformation in detail, we ran a large-scale field test in which an artificial landslide was induced by the application of a load to a natural slope. The measured landslide displacement was reproduced numerically through the use of finite element model analysis with a two-dimensional elasto-viscoplastic model. The analysis suggested that the strength of the sliding surface decreased as the landslide mass moved. We propose a simple method for estimating safety factors. The method involves back-calculation of shear strength parameters through reproduction of observed landslide displacements and calculating the ratio of driving force to resisting force acting on the sliding surface as modeled by joint elements. This ratio, the “stability index”, shows the same trend as safety factors calculated by a two-dimensional limit equilibrium method and a shear strength reduction method that use back-calculated shear strength parameters estimated from the limit equilibrium state. The results indicate that the stability index may be applicable to the assessment of slope stability.

Effect of pixel size on cartographic representation of shallow and deep-seated landslide, and its collateral effects on the forecasting of landslides by SINMAP and Multiple Logistic Regression landslide models

It is important to evaluate the influence of pixel resolution on cartographic representations of landslides to assess models for detection of unstable hillslopes. However, little work has been done on the effect of the resolution of Digital Elevation Models on landslide modeling. This paper uses artificial landslides to evaluate how pixel size affects the cartographic representation of shallow and deep-seated landslides. Published landslide sizes and manual modification of contour lines are used to produce artificial depletion landslide topography. Two landslide models are used: Stability Index MAPping (SINMAP) and Multiple Logistic Regression (MLR). The two models are embedded in a GIS system to facilitate the analysis. The evaluation is conducted at 1 m, 5 m, 10 m, and 30 m pixel resolutions. As the pixel size increases, the landslide loses cartographic representation. The result is a biased model prediction. In tests on real topography in landslide terrain, MLR predictions match existing landslides better than do SINMAP predictions, if the MLR model has enough pixels to obtain reliable statistics. SINMAP more consistently produces a similar susceptibility map over a range of pixel resolutions. In general, MLR over-predicts while SINMAP under-predicts landslides as pixels coarsen.

Optimal estimator for assessing landslide model performance

Abstract. The commonly used success rate (SR) in evaluating cell-based landslide model performance is based on the ratio of successfully predicted landslide sites over total actual landslide sites without considering the performance in predicting stable cells. We proposed a modified SR (MSR), in which the performance of stable cell prediction is included. The advantage of MSR is to avoid over- and under-prediction while upholding the stable sensitivity throughout all simulated cases. Stochastic analyses are conducted by using artificial landslide maps and simulations with a full range of performances (from worst to perfect) in both stable and unstable cell predictions. Stochastic analyses reveal mathematical responses of estimators to various model results in calculating performance. The Kappa method, which is commonly used for satellite image analysis, is improper for landslide modeling giving inconsistent performance when landslide coverage changes. To examine differences among SR and MSR in real model application, we applied the SHALSTAB model onto a mountainous watershed in Taiwan. Case study shows that stable and unstable cell predictions are inter-exclusive in SHALSTAB model. The optimal estimator should compromise landslide over- and under-prediction. According to our 4000 simulations, the best simulation generated by MSR projects 83 hits over 131 actual landslide sites while the unstable cells cover only 16% of the studied watershed. By contrast, despite the fact that the best simulation deduced from SR projects 120 hits over 131 actual landslide sites, this high performance is only obtained when unstable cells cover an incredibly high landslide cover (~75%) of the entire watershed exhibiting a significant landslide over-prediction.

Movement of Melting Snow on the Ground and Prediction of Landslides

It has been found that many landslides occur in snowy areas. According to our researches, the relation has been found between the occurrence of landslides and the depth of snowcover. In order to clarify this phenomenon, an automatic observation apparatus was introduced and an artificial landslide was produced. It was suggested that the landslide would be predicted by the investigation of constant strength c and φ of clay in the sliding zone, the behavior of the compound shearing force depending on the gap hydraulic pressure and the pressure of the air enclosed in the ground, and the worsening of sliding zone of permeability.