Landslide Width Research Articles

Landslide scales affect soil organic carbon accumulation by influencing microbial decomposition of plant-derived carbon after earthquakes

Geological movements can affect carbon distribution patterns and turnover mechanisms in terrestrial ecosystems by altering surface landscape patterns. However, little is known about how changes in surface landscape features after geological hazards affect the microecological mechanisms of soil carbon. In this study, eight landslides with similar standing conditions and formation times but different scales were selected in the geologically active zone of Southwest China. A macro genome sequencing approach was used to study the microbial changes in the soil carbon functions of landslides after earthquakes. The results indicated that the scale of landslide scale was a significant factor affecting soil carbon stocks after earthquake. Among the landslide scale factors, landslide width had a greater effect on soil carbon storage than length or area. Landslide width corresponded with increased microbial decomposition of plant (lignin, hemicellulose) and fungal (chitin) carbon sources, but both chitinous soil content and its decomposition function gene abundance were low and had a small effect on the total carbon pool. The major bacterial phyla (Actinobacteria, Candidatus Rokubacteria, and Acidobacteria) mineralize carbon sources from plant and fungal biomass fractions through their selective adaptation mechanisms based on the landslide scale. Starch and polysaccharide related metabolic pathways differed significantly between landslides at different scales. Overall, our results emphasize the importance of microbes in surface carbon dynamics driven by geological movements. It is also noted that the scale of landscape degradation following geological disturbance is a key indicator that soil carbon and that microbes influence postdisaster soil carbon recovery and accumulation by regulating their selection and utilization of plant-derived carbon. The findings of this study help to estimate the turnover and distribution of terrestrial ecosystem carbon driven by geological movements at a larger scale.

An Analytical Calculation Method and Mechanical Response Laws of Buried Pipelines Subjected to the Impact of Transverse Landslides

When the buried gathering and transportation pipelines cross the landslide area transversally, the migration of the landslide mass can cause the pipelines to be subjected to lateral thrust, which can seriously affect the safe operation of the buried pipelines. In order to study the mechanical response laws of the buried pipelines under the impact of transverse landslides, based on the elastic-plastic foundation beam theory, the mechanical models of buried pipelines are established for three situations, and the analytical solution of pipeline displacement is obtained by genetic algorithm. The influences of landslide thrust, landslide width, soil resistance coefficient, the pipe outer diameter and wall thickness on pipeline peak displacement and peak stress are also investigated. The results show that under the impact of the transverse landslide, with the increase of landslide thrust, the maximum displacement and maximum tensile stress of pipeline increase exponentially, and the failure risk of pipe increases. Secondly, with the increase of landslide width, the maximum displacement of pipeline increases in the beginning and then decreases to be constant, and the maximum tensile stress decreases sharply to be constant. Thirdly, with the increase of soil resistance coefficient, the maximum displacement and maximum tensile stress of pipeline decrease in a negative power trend, and the pipeline is safer. Fourthly, when the pipe outer diameter increases to a certain value, the maximum displacement and maximum tensile stress of the pipeline change very little, hence, pipe outer diameter can be optimized when designing pipe structure. Fifthly, the smaller the pipe wall thickness is, the greater the maximum tensile stress of the pipe is, therefore, pipe corrosion protection should be paid attention to. Sixthly, when the landslide thrust is large, the landslide width is small, or the pipeline outer diameter is small, the maximum tensile stress of the pipeline is located at the centre of the landslide, otherwise, it is located at 0.56L ~ 0.7L away from the landslide centre. In order to ensure the safe operation of the pipeline, the stress state of these two positions should be focused on. It is concluded that the study can provide the basis for the evaluation of pipeline safety status and has practical significance for ensuring the safe operation of buried pipelines.

Study on Mechanical Failure Behavior of Steel-Wire Wound Reinforced Thermoplastic Pipe under Combined Internal Pressure and Soil Landslide Conditions.

A steel-wire wound reinforced thermoplastic pipe (SWW-RTP) has been widely utilized in many industrial areas, and a soil landslide is an inevitable hazardous extreme condition for the SWW-RTP as it is usually buried underground. It is imperative to study the mechanical failure behavior and the failure criterion of the SWW-RTP under the combination of internal pressure and soil landslide conditions, and this paper is the first study to investigate the topic. In this paper, groups of stress-strain curves of high-density polyethylene (HDPE) and steel wires were obtained by uniaxial tensile tests at different strain rates, with the help of a Digital Image Correlation device (DIC). A rate-dependent constitutive model was employed to represent the mechanical behavior of the HDPE and to help deduce the stress-strain curve of the HDPE under the required strain rate, estimated from the static simplification of the dynamic soil landslide. Afterwards, a finite element model of the SWW-RTP, embedded in a cubic of soil, was established with the software ABAQUS. The SWW-RTP model was composed of HDPE solid elements, embedded with steel-wire truss elements, and the soil was characterized with the extended Drucker-Prager model. A quartic polynomial displacement distribution was applied to the soil model to represent the soil landslide. Then, the mechanical response of the SWW-RTP was analyzed. It was found that the failure criterion of the HDPE yield was more suitable for the pipe subjected to internal pressure and soil landslide conditions, instead of the steel-wire strength failure criterion always used in traditional research on the SWW-RTP. Further, the influence of landslide width, internal pressure and steel-wire number were discussed. The larger the width of the landslide area, the gentler the deformation of the pipeline; this resulted in an increase in the maximum landslide and a decrease in the maximum curvature with the width of the landslide area. The relatively high internal pressure was beneficial to the safety of the SWW-RTP under landslide, because the internal pressure could increase the stiffness of the pipeline. The number of steel wires had a limited influence on the maximum landslide required for the SWW-RTP's failure. This work can be useful for the design and safe assessment of the SWW-RTP under internal pressure and soil landslide conditions.

Optimal Route Selection of Offshore Pipelines Subjected to Submarine Landslides

Background: Offshore lifelines (i.e., pipelines and cables) are usually vulnerable to seabed deformations induced by earthquake-triggered geohazards, such as submarine landslides, soil liquefaction, and tectonic faulting. Since the complete avoidance of all areas characterized by offshore geohazards is not always techno-economically feasible, optimal lifeline route selection is deemed necessary for the safety and serviceability of every such infrastructure, in order to minimize the risk of severe environmental and economic consequences. Objective: The current study presents a decision-support tool for the design of offshore high-pressure gas pipelines, capable of performing: (a) the assessment of submarine landslides along a possible pipeline route (i.e., impact force and landslide width), (b) the assessment of their potential impact on the pipeline (i.e., pipeline strains), and (c) the optimal pipeline route selection. Methods: The advanced capabilities of GIS in lifeline optimal route selection are successfully combined with efficient (semi-)analytical models that realistically assess the response of offshore pipelines when subjected to axial or oblique loading conditions due to a submarine landslide. Results: The efficiency of the smart tool is presented through a case study of an offshore pipeline that is crossing potentially unstable slopes -under static and seismic conditions- in the Adriatic Sea. Five alternative routings are proposed based on the adopted design criteria when crossing the seismically unstable slopes and zones characterized by steep inclination. Conclusion: Provided that sufficient and reliable data are available, the developed decision-support tool can be efficiently used for deriving the potentially optimal route of an offshore pipeline.

Investigation on responses and capacity of offshore pipelines subjected to submarine landslides

Offshore pipelines are the main means for transmitting marine oil and gas resources, and they are usually threatened by various geohazards, typically by submarine landslides. However, systematical analyses and solutions for pipeline capacity to resist submarine landslides have been rarely reported. This paper aims to carry out a series of numerical simulations to investigate the responses and capacity of offshore pipelines subjected to submarine landslides. First, a finite element model is developed and validated, in which the pipeline is modeled using beam elements and pipe-soil interaction is modeled using the axial and lateral soil springs with different force-displacement relationships. To further accurately and efficiently assess pipeline performance under the impact of submarine landslides, equivalent boundary conditions are proposed based on the analytical solution. After validation of the equivalent boundary conditions, a series of parametric studies is performed to investigate the capacity of offshore pipelines under the impact of submarine landslides (i.e., critical impact force). Various ranges of soil properties, pipeline burial depths, diameters, steel grades and landslide widths are included in the parametric study. Then through regression and dimensional analysis, the normalized critical impact force is reasonably formulated using the normalized landslide width, normalized axial and lateral soil resistances. Moreover, scour effect induced by seabed currents on the critical impact force is also investigated. Finally, the design charts are achieved and are directly used to predict the critical impact force and evaluate the pipeline safety under the impact of submarine landslides.

Landslide response to vegetation by example of July 25–26, 2013, extreme rainstorm, Tianshui, Gansu Province, China

Loss Plateau of China is an area with long-term vegetation restoration while serious mass movements. Local vegetation does act as sediment reducing role while quantification of their effect on landslides is lacking. This work presents a first research work about the connection between landslides and vegetation by the example of July 25–26, 2013, extreme rainstorm. High-resolution sensing orthoimages, landside width, and simplified infinite slope theory were used to examine landslide distribution and the lateral apparent cohesion of roots. The results reveal that shallow landslides have a higher probability at the transitional slope area. The majority of them have a gradient of 20–25°, locate on south-facing slopes, and areas with sparse vegetation. Vegetation cover, represented by the Green-Red Vegetation Index (GRVI), is the controlling factor of landslide distribution and size. The estimated lateral apparent cohesion of plant roots is not positively related to GRVI, and increase when GRVI > 0.2. The relationship between landslide width and slope gradient indicates that strong root strength may result in larger landslide volume. This result of this work is a pioneering trial in correlating the lateral apparent cohesion from roots and forest crown, which is helpful for understanding the effect of vegetation on landslides.

A new algorithm for landslide geometric and deformation analysis supported by digital elevation models

Geometric analysis of a landslide boundary, in particular, automatic determination of the length and width of landslide and classification is a challenge. In this regard, developing an integrated automatic algorithm to determine and measure length, width, area, failure flow direction, mass displacement material, and to classify a landslide, all at one time seem to be a useful method for updating landslide inventory with reliable outcomes and efficient time for disaster management. This study presents a new automatic mapping and modelling algorithm for landslide geometric analysis include calculating landslide displacement and failure flow direction. We utilized LiDAR high resolution digital elevation model (DEM) (5 m), ASTER DEM (30 m), and Unmanned Aerial Vehicle (UAV) associated with ground truth observations to support the geometric deformation measurements. This study aims to refurbish generating landslide inventory dataset of 2015 by implementing the proposed algorithm in a quicker time than existing and traditional methods. The proposed algorithm is scripted in MATLAB based on the DEMs of before and after a landslide. The proposed new automatic method contributes measure, determine, and calculate (a) length, width, area, (b) the flow direction of the material movement, (c) the volume of the material displacement after the onset of failure, and (d) type of a landslide, in an acceptable accuracy performance. I considered two study areas (1) Alborz Mountain of Iran and (2) Madaling of Guizhou Province in China. The proposed algorithm was validated by (a) the ground truth observations, (b) the existing inventory dataset and (c) implementing the same data in ArcGIS 10.4 to compute the relative measurement errors. The relative error for area, length, width, and volume is 0.16%, 1.67%, 0.30%, 5.50%, respectively.

Model Test Research on the Propagation of Tsunamis and Their Interaction with Navigating Ships

The slope of a reservoir area is unstable and can be destroyed by natural disasters, such as strong earthquakes and rainstorms. Landslide bodies that enter the water and generate landslide surges pose serious safety risks to terminals, ships, and hydraulic structures in a reservoir area. After analyzing landslide data in a reservoir area, a series of comparative tests was carried out to investigate the propagation characteristics of landslide-induced tsunamis in channel reservoirs, and the changes in water level values at various monitoring points in the river channel after the landslides entered the water were explored. The effects of landslide width and thickness on the characteristics of landslide-induced tsunamis were analyzed. The main target was a fixed-velocity ship in landslide-swelling water. The complex nonlinear motion characteristics of the ship on the water were studied to determine the safe navigation range.

Extracting region-specific runout behavior and rainfall thresholds for massive landslides using seismic records: a case study in southern Taiwan

Typhoon Morakot struck Taiwan on 7 August 2009, bringing severe rainfall and landslides. Of the many landslides caused by the storm, 12 large-scale landslides were discovered based on seismic signals recorded from broadband seismic stations. Landslides inventoried from both seismic records and satellite imagery are used as baseline data to evaluate region-specific forensic analyses of landslide features, e.g. disturbed area, width and runout distance (Drunout), associated with landslide-induced seismic signals and signal durations (Δt). The results of these analyses show that (i) the landslide-disturbed area correlated well with signal duration when Δt was over 60 s; (ii) the landslide-disturbed area correlated well with the ratio of the landslide width to runout distance when Δt was under 40 s; (iii) the runout distance of sliding mass exhibited a positive relation with Δt2, satisfying the energy conserved during mass movement. This case study presents a region-specific examination of the Δt-Drunout relationship based on 12 large-scale landslides that occurred during Typhoon Morakot, providing insight into the sliding processes. In addition, the time of landslide initiation was extracted from seismic signals in order to better understand region-specific, large-scale, landslide rainfall thresholds. These relationships indicate that (a) long-duration rainstorms with high cumulative rainfall tend to dictate the occurrence of large-scale landslides; (b) the rainfall threshold for large-scale landslides is found to be higher than in previous studies that also include smaller landslides, defined in this region as I = 60D−0.31, where I is the rainfall intensity (mm/h) and D is the duration (h) of the rainstorm.

Landslides detection and volume estimation in Jinbu area of Korea

ABSTRACTShallow landslides triggered by heavy rainfall are common phenomena in mountainous areas of temperate monsoon regions. On July 2006 intensive shallow landslides occurred in Jinbu area, Korea triggered by heavy rainfall. An inventory of 1412 shallow landslides was constructed from intensive field works and interpretation of web-based aerial photographs, and all landslides detected were mapped across the study area. The measurements were geometrical properties (landslide length, landslide width, landslide depth) of individual landslides to establish the relationship linking landslide area to landslide volume. The relationship linking landslide area to landslide volume was obtained from the inventory of 930 landslides and is a power law function with a scaling exponent γ = 1.02, covers four orders of magnitude of landslide area and landslide volume, and is in reasonable agreement with existing relationships obtained from small scale shallow landslide events. The relationship can be used to estimate the volume of individual landslides with shallow soil depth when the area of landslide is known. However, geological and geomorphological setting should be considered to calculate accurate landslide volume with respect to disaster prevention.

Mechanical behavior of pipelines subjecting to horizontal landslides using a new finite element model with equivalent boundary springs

A new finite element model was developed to analyze the mechanical behavior of pipelines subjecting to horizontal landslides, where equivalent boundary springs were used at the pipeline end. The equivalent boundary spring was used to simulate the interaction of the pipeline-soil outside the model. More specially, an analytical method was derived to calculate the stiffness coefficient of the equivalent boundary spring. The new finite element model was validated by comparing the results of the axial displacement and strain to the referred model, with minor deviations of less than 5.53%. Meanwhile, the effects of different parameters on the mechanical responses of pipelines were discussed, including the friction coefficient, the landslide displacement, the landslide width and the constraint condition at the pipeline end. The results show that larger landslide displacements lead to larger axial displacements and strains of pipelines. Also, larger kinetic friction coefficients can decrease the axial displacement and strain, and constraint conditions at pipeline ends have an impact on the axial displacement and the axial strain.

Landslide distribution and size versus relative relief (Shaanxi Province, China)

The present study aims to investigate the distribution and size of landslides in relation to relative relief. For this, a landslide inventory map of the area was developed from the interpretation of satellite images and detailed field survey. From this we could map 331 landslides in Ningqing County (Shaanxi Province). By using GIS and statistical approaches, we studied the coupling between landslide size distribution and relative relief. From this the control of relative relief on the rollover effect of the size distribution of landslides is obtained. The result shows that the landslide frequency-relative relief distribution is unimodal, with majority of landslides occurring in areas with relative reliefs in between 300 and 400. The relative number density of landslides decreased with the increase in the relative relief; on the contrary, the average area, average length and average width of landslide increased with the increase in relative relief. The percentage of large-scale landslide increased with the increase of relative relief or vice versa. In addition, the cumulative frequency-area distributions of these landslides empirically agree well with a power-law relation with an exponent of 1.776 above a certain size threshold. Below this value, it exhibited an obvious rollover effect. Further analysis has shown that landslide cumulative frequency-area curve is strongly influenced by relative relief. The rollover effect is more obvious with the increase of relative relief. The exponent of power law correlation gradually increased from 0.993 to 1.872 with increasing relative relief.

An improved landslide mobility model

A relatively simple and versatile numerical model known as DAN, developed by Oldrich Hungr for the assessment of landslide mobility, has been enhanced to incorporate the consideration of a trapezoidal-shaped flow channel for more realistic modelling purposes. This enhanced debris mobility model (DMM) has been programmed to run on a spreadsheet and has been calibrated against detailed landslide data in Hong Kong. In contrast to previous work, the enhanced DMM eliminates the limitations inherited from the assumption of a rectangular flow channel with frictionless side boundaries. When using DMM, no predefined width of landslide is needed. The DMM simulates landslide mobility with the flow resistance on the whole wetted perimeter of the channel, calculates the surface width of the landslide based on the cross-sectional geometry of the channel, and is capable of predicting a lobe-shaped debris deposition area. This technical note presents details of the enhancement to the DAN formulation.Key words: landslides, debris flows, runout analysis, landslide mobility, dynamic modelling, numerical methods.

Development of a 3D numerical wave tank for modeling tsunami generation by underwater landslides

A three-dimensional (3D) numerical wave tank (NWT) solving fully nonlinear potential flow theory, with a higher-order boundary element method (BEM), is modified to simulate tsunami generation by underwater landslides. New features are added to the NWT to model underwater landslide geometry and motion and specify corresponding boundary conditions in the BEM model. In particular, a new snake absorbing piston boundary condition is implemented to remove reflection from the onshore and offshore boundaries of the NWT. Model results are favorably compared to recent laboratory experiments. Sensitivity analyses of numerical results to the width and length of the discretization are conducted, to determine optimal numerical parameters. The effect of landslide width on tsunami generated is estimated. Results show that the two-dimensional approximation is applicable when the ratio of landslide width over landslide length is greater than 2. Numerical accuracy is examined and found to be excellent in all cases.