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Zhang M.,Hubei University | Yin Y.,China Institute of Geo Environment Monitoring | Huang B.,Hubei University
Landslides | Year: 2015

Red beds are widespread in the eastern Sichuan Basin, SW China, and are often called “landslide prone strata”. The dip angle of these red beds is commonly less than 10°, which is much less than the angle of internal friction between the bedding planes. Thus, in theory, failure will not occur along the bedding planes in such strata. We used field methods, numerical modeling, and ring shear tests to investigate the effects of rainfall on landslides in shallow-dipping red beds, using the Qingning landslide in SW China as an example. Our results suggest that the probable mechanisms leading to failure are (1) permeation of rainfall through the cracks at the back of the landslide site that increases the hydrostatic water pressure, which adds to the sliding stress and reduces the effective stress on the failure surface, gradually destabilizing the mass. In the Qingning landslide, the maximum water pressure was as high as 21.8 m before failure. When the factor of safety decreased markedly to 1.015, the sliding mass started to slowly slide. (2) As sliding takes place, the sliding zone soil is under undrained shear and its shear strength decreases sharply to a critical value, which promotes rapid sliding. In the Qingning landslide, the shear resistance of the sliding zone soil decreased markedly to 25.9 kPa as the pore water pressure increased to 118.3 kPa. This study may provide a theoretical basis for landslide forecasting in gently inclined red beds of the eastern Sichuan Basin as well as in similar geological settings worldwide. © 2015, Springer-Verlag Berlin Heidelberg.

Li T.,Tsinghua University | Xiao X.,Tsinghua University | Xue Q.,China Institute of Geo Environment Monitoring
Proceedings - 2012 IEEE Symposium on Robotics and Applications, ISRA 2012 | Year: 2012

In this paper we propose a new unsupervised and domain independent approach for sentiment classification. It takes a few documents as the training set to build a sentiment vocabulary list which will be used to classify the documents according to their sentiment orientation. The system is self-supervised and domain independent. Experimental results show that the classification accuracy of the approach can reach 85.7% which is better than the previous experiments of unsupervised methods. © 2012 IEEE.

Cheng G.M.,China Institute of Geo environment Monitoring | Liu T.Z.,China University of Geosciences | Zhi B.,China University of Geosciences
Applied Mechanics and Materials | Year: 2014

In China, surface subsidence caused by steep coal seam mining has affected the safe operation of pipelines in recent years. The study site is one coal mine, where the gas pipeline from Shanshan to Urumqi is across. FLAC3D was adopted to study subsidence-induced stress on the pipeline, and the numerical model was calibrated with the measurement data. Visualization of alarm levels on the pipeline was obtained by integrating the usage of Fish function embedded in FLAC3D and Tecplot. The simulations reveal that the stress on the pipeline is closely related to the excavation depth. The stress on the pipeline increases with the excavation depth increasing when mining the 1st, 2nd, and 3rd levels, whereas the stress on the pipeline decreases slightly with the excavation depth increasing when mining the fourth, fifth, and sixth levels. The maximum stress on the pipeline occurs after mining the 3rd level. The possible damage to the pipe is at the upper-right side. Therefore, the results are helpful to prevent and reduce the impact of subsidence on the pipeline. © (2014) Trans Tech Publications, Switzerland.

Yin Y.,China Institute of Geo environment Monitoring | Li B.,Institute of Geomechanics | Wang W.,China Institute of Geo environment Monitoring
Landslides | Year: 2015

This paper discusses the effect of the May 12, 2008 Wenchuan earthquake on a landslide where stabilization work had taken place and compares the results to sites without stabilization. Contours of shear strain increment and displacement values obtained using a FLAC3D simulation show that the Wangjiayan landslide, which had stabilization work, was stable before the Wenchuan earthquake. Simulations using input strong motion accelerations from the main shock recorded at Qingping station, within the main seismic fault zone, suggest a shear strain increment about 3,000 times more than it was before the main shock. Although the stability of the stabilized landslide decreased during the earthquake, the displacement values were very small. Modeled displacements suggest that the piles played a major role in keeping the slope from sliding. The anti-slide piles were subjected to high shaking acceleration. The strong ground motion records for a time range of 10 to 30 s show that the piles generally experienced accelerations in the range from 0.0 to 3.0 g, with a few spikes of about 5.0 g. Special observation stations were set up to monitor the slope motion at Qingchuan town, 150 km far from the Wangjiayan landslide, along the main central seismic fault zone, after the Wenchuan earthquake. The variation in acceleration with time and the FOS versus time of the Wangjiayan landslide were investigated using these acceleration records of the aftershocks as input data. The aftershock accelerations did not decrease the stability of the Wangjiayan landslide, but an amplification effect on the acceleration of the slope at different elevations was illustrated. © 2014, Springer-Verlag Berlin Heidelberg.

Peng L.,Wuhan University | Peng L.,China Institute of Geo Environment Monitoring | Niu R.,Wuhan University | Huang B.,Chinese University of Hong Kong | And 3 more authors.
Geomorphology | Year: 2014

This paper aims to develop a novel hybrid model for assessing landslide susceptibility at the regional scale using multisource data to produce a landslide susceptibility map of the Zigui-Badong area near the Three Gorges Reservoir, China. This area is subject to anthropogenic influences because the reservoir's water level fluctuates cyclically between 145 and 175. m; in addition, the area suffers from extreme rainfall events due to the local climate. The area has experienced significant and widespread landslide events in recent years. In our study, a novel hybrid model is proposed to produce landslide susceptibility maps using geographical information systems (GIS) and remote sensing. The hybrid model is based on rough set (RS) theory and a support vector machine (SVM). RS theory is employed as an attribute reduction tool to identify the significant environmental parameters of a landslide, and an SVM is used to predict landslide susceptibility. Four data domains were considered in this research: geological, geomorphological, hydrology, and land cover. The original group of 20 environmental parameters and 202 landslides were used as the inputs to produce a landslide susceptibility map. According to the map, 19.7% of the study area was identified as medium- and high-susceptibility zones encompassing 89.5% of the historical landslides. The results indicate high levels of landslide hazard in and around the main inhabited areas, such as Badong County and other towns, as well as in rural residential areas and transportation areas along the Yangtze River and its tributaries. The predicted map indicates a good correlation between the classified high hazard areas and slope failures confirmed in the field. Furthermore, the quality of the proposed model was comprehensively evaluated, including the degree of model fit, the robustness of the model, the uncertainty associated with the probabilistic estimate, and the model prediction skill. The proposed model was also compared with the general SVM, which demonstrated that the hybrid model has superior prediction skill and higher reliability and confirmed the usefulness of the proposed model for landslide susceptibility mapping at a regional scale. © 2013 Elsevier B.V.

Tong B.,China Institute of Geo Environment Monitoring | Tong B.,Iowa State University | Schaefer V.R.,Iowa State University
International Journal of Geomechanics | Year: 2016

Gravity-type caisson walls are a type of popular but easily damaged waterfront construction structure, especially in seismic regions. Various forms of mitigation have been successfully applied to improve their performance when subjected to liquefaction. Establishment of an effective, reliable, and easily implemented liquefaction remedial design procedure based on commonly used ground improvement technology is important. In this study, following the philosophy of performance-based design, a novel optimization process was developed and applied to a well-known case study. The vibrocompaction method was examined within a framework of a well-calibrated case history to hypothetically improve the seismic performance of a damaged caisson quay wall to an acceptable level. This study includes three major steps: first, the constitutive model used in this study for describing liquefaction was calibrated based on the published data; second, a caisson quay wall case history damaged by liquefaction was simulated as the unimproved benchmark; finally, the vibrocompaction method was applied as the mitigation technique to provide improvement to an acceptable level, and the mitigation design was optimized. The remedial program design characteristics, such as improved soil zone lateral extent in backfill soils and improved zone depth in foundation soils, were optimized. Through a parametric study, insights and recommendations on the establishment of liquefaction remediation design and optimization process for gravity-type caisson wall are provided for further study. © 2016 American Society of Civil Engineers.

Bai S.,Nanjing Normal University | Lu G.,Nanjing Normal University | Wang J.,Nanjing Normal University | Zhou P.,China Institute of Geo Environment Monitoring | Ding L.,Nanjing Normal University
Environmental Earth Sciences | Year: 2011

Landslides have had a huge effect on human life, the environment and local economic development, and therefore they need to be well understood. In this study, we presented an approach for the analysis and modeling of landslide data using rare events logistic regression and applied the approach to an area in Lianyungang, China. Digital orthophotomaps, digital elevation models of the region, geological maps and different GIS layers including settlement, road net and rivers were collected and applied in the analysis. Landslides were identified by monoscopic manual interpretation and validated during the field investigation. To validate the quality of mapping, the data from the study area were divided into a training set and validation set. The result map showed that 4.26% of the study area was identified as having very high susceptibility to landslides, whereas the others were classified as having very low susceptibility (47.2%), low susceptibility (22.21%), medium susceptibility (14.39%) and high susceptibility (11.93%). The quality of the landslide-susceptibility map produced in this paper was validated, and it can be used for planning protective and mitigation measures. The landslide-susceptibility map is a fundamental part of the Lianyungang city landslide risk assessment. © 2010 Springer-Verlag.

Bai S.-B.,Nanjing Normal University | Wang J.,Nanjing Normal University | Lu G.-N.,Nanjing Normal University | Zhou P.-G.,China Institute of Geo Environment Monitoring | And 2 more authors.
Geomorphology | Year: 2010

A detailed landslide susceptibility map was produced using a logistic regression method with datasets developed for a geographic information system (GIS). Known as one of the most landslide-prone areas in China, the Zhongxian-Shizhu segment in the Three Gorges Reservoir region of China was selected as a suitable case to evaluate the frequency and distribution of landslides. The site covered an area of 260.9 km2 with a landslide area of 5.3 km2. Four data domains were used in this study: remote sensing products, thematic maps, geological maps, and topographical maps, all with 25 × 25 m2 pixels or cells. Statistical relationships for landslide susceptibility were developed using landslide and landslide causative factor databases. We extended the application of logistic regression approaches to use all continuous variables as they are, and the landslide density is used to transform these nominal variables to numeric variable. According to the map, 2.8% of the study area was identified as an area with very high-susceptibility, whereas very low-, low-, medium- and high-susceptibility zones covered 18.2%, 36.2%, 26.7%, and 16.1% of the area, respectively. The quality of susceptibility mapping was validated, and the correct classification percentage and root mean square error (RMSE) values for the validation data were 81.4% and 0.392, respectively. Crown Copyright © 2009.

Zhang M.,Hubei Engineering University | Yin Y.,China Institute of Geo Environment Monitoring
Engineering Geology | Year: 2013

The dynamics and occurrence conditions of 43 rapid and long run-out rock avalanches in China were summarized. Their dynamics were classified into 5 types. The standard dynamic type was designated to be "fail, squirt and flow", where part of the landslide path always has a parabolic airborne course because the slide body has an initial speed and the toe of the surface of rupture projects the landslide into the air. The occurrence conditions of rock avalanches of the standard dynamic type are huge kinetic energy, elevated toe to the surface of rupture and enough transport space to run out into. The occurrence conditions of the other four types were then compared with the standard dynamic type. Statistical analysis showed that volume, topography, huge kinetic energy and an elevated toe to the surface of rupture were the principal factors controlling mobility in the rock avalanches. Four of the rapid long run-out rock avalanches, each in a different geological setting, were then examined in more detail to reveal the transport mechanisms leading to their high speed and long runout. The results suggested that besides their huge kinetic energy, high pore water pressure produced by undrained shear and elastic energy released by grain fragmentation were the main transport mechanisms contributing to the long travel distances and high speeds of rock avalanches. Field investigation indicated that air was involved during the transport, but whether it influenced the transport or how much the influence was is still much disputed. © 2013 Elsevier B.V.

Yin Y.,China Institute of Geo Environment Monitoring
Environmental Earth Sciences | Year: 2014

The 2008 Wenchuan earthquake with Ms8.0 triggered extensive throwing-pattern landslides in the area within or near the seismic faults. The resultant landslides from this earthquake brought to the fore the effect of vertical earthquake acceleration on landslide occurrence. The pseudostatic analysis and the dynamic response on landslide stability due to the Wenchuan earthquake are studied with the Chengxi (West Town) catastrophic landslide used as a case study. The results show that the epicenter distance is an important factor which affects the vertical acceleration and thus the stability of landslide. Also, the vertical acceleration was found to have a significant impact on the FOS of landslide if the earthquake magnitude is quite large. Within the seismic fault, the amplitude effect of vertical acceleration is very dominant with the FOS of landslide, for vertical acceleration ranging from positive to negative, having a variation of 25 %. The variation of FOS of landslide for vertical acceleration ranging from positive to negative are 15 and 5 % for landslides near seismic fault and outside seismic fault, respectively. For landslide with a slope angle <45°, the FOS of landslide with both horizontal and vertical accelerations is significantly greater than the one without vertical acceleration. Further, the results computed from both the pseudostatic method and dynamic analysis reveal that the FOS during the earthquake varied significantly whether vertical acceleration is considered or not. The results from this study explain why lots of throwing-pattern catastrophic landslides occurred within 10 km of the seismic fault in the Wenchuan earthquake. © 2013 Springer-Verlag Berlin Heidelberg.

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