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Li Y.R.,Taiyuan University of Technology | Li Y.R.,AGECON Ltd. | Wen B.P.,Water Resources University | Aydin A.,University of Mississippi | Ju N.P.,Chengdu University of Technology
Engineering Geology | Year: 2013

Reactivation of large-scale landslides along the reservoir banks of the Three Gorges Project (TGP) is recognized as the most likely form of geohazards threatening safety and operation of the dam and the navigation. This study presents an investigation into the naturally drained shear properties of slip zone soils of such landslides. Twenty-seven specimens of slip zone soils of three giant landslides are tested at three shearing rates (0.1, 1 and 10. mm/s) by means of a large ring shear apparatus accommodating abundant coarse particles in the specimens. It is observed that a) soils with higher plasticity index or liquid limit tend to have lower residual shear strength; this influence of the Atterberg limits on the residual shear strength weakens as the shearing rate increases; b) even small variations in the particle size distribution (. PSD) cause notable differences in shear properties. The PSD parameters, such as the coefficient of curvature, sand content, ratio of gravel content to the sum of remaining contents, and ratio of coarse fraction to fine fraction, have close correlations with the residual strength; and c) the residual strength is clearly affected positively by particle symmetry (quantified by elongation) and negatively by surface smoothness (quantified by convexity). © 2013 Elsevier B.V. Source

Liu H.,Chengdu University of Technology | Xu Q.,Chengdu University of Technology | Li Y.,AGECON Ltd. | Fan X.,Chengdu University of Technology | Fan X.,University of Twente
Bulletin of the Seismological Society of America | Year: 2013

Studies on landslides by the 2008 Wenchuan earthquake showed that the topography is of great importance in amplifying the seismic shaking. The present study carried out experiments on rock slopes by means of a shaking table. The recorded Wenchuan earthquake waves are scaled to excite the model slopes. Measurements from accelerometers installed on free surface of the model slope simulating high-strength rocks are analyzed, with much effort on acceleration responses to both horizontal and vertical components of seismic shaking. It is found that the amplification factor of peak horizontal acceleration (PHA) is increasing with elevation of the model slope, though the upper and lower halves of the slope exhibit different increasing patterns. The amplification factor of peak vertical acceleration (PVA) exhibits a lying S-shaped changing trend with the elevation, indicating attenuations of PVAs at the toe and top of a slope. In addition, the XZ-direction shaking produces a horizontal and vertical response stronger than X-direction and Z-direction shaking alone. Both PHA and PVA increase with the excitation intensity.However, the corresponding amplification factors generally decrease, indicating the acceleration response of a slope weakens with the excitation intensity of shaking. Finally the statistic of ratio of PVA to PHA indicates that 85% of the slope height, especially the upper middle part, is likely subject to PVAs greater than or equal to 2=3 of PHA and 32% of the slope height to PVAs greater than or equal to PHA. This indicates the nonignorable role of PVA in responses of a slope to an earthquake and necessity of considering during design work. © 2013 by the Seismological Society of America. Source

Huang R.,Chengdu University of Technology | Huang J.,Chengdu University of Technology | Ju N.,Chengdu University of Technology | Li Y.,AGECON Ltd.
Engineering Geology | Year: 2013

At present, rock mass classification in tunnel construction basically depends upon geologist's knowledge, and normally suffered from bias judgments. Based on rock engineering system and computer programming technology, an approach to automated zonation and classification of rock mass is presented in this paper. Seven parameters are considered and parameter interaction intensity and weighting of each parameter have been analyzed. Discontinuity property is found to be the most important factor influencing rock mass quality. The rock mass quality index, which is the weighted summation of each selected parameter, is put forward for rock mass classification. A computer-aided automated classification system is then developed and used for the Dazhushan tunnel. The classification results show good agreement with that by RMR, indicating that the proposed system can work precisely, with its powerful function for data management and fast implementation. © 2013 Elsevier B.V. Source

Ju N.-P.,Chengdu University of Technology | Huang J.,Chengdu University of Technology | Huang R.-Q.,Chengdu University of Technology | He C.-Y.,Chengdu University of Technology | Li Y.-R.,AGECON Ltd.
Journal of Mountain Science | Year: 2015

Landslides not only cause property losses, but also kill and injure large numbers of people every year in the mountainous areas. These losses and casualties may be avoided to some extent by early warning systems for landslides. In this paper, a realtime monitoring network and a computer-aided automatic early warning system (EWS) are presented with details of their design and an example of application in the Longjingwan landslide, Kaiyang County, Guizhou Province. Then, according to principle simple method of landslide prediction, the setting of alarm levels and the design of appropriate counter-measures are presented. A four-level early warning system (Zero, Outlook, Attention and Warning) has been adopted, and the velocity threshold was selected as the main warning threshold for the landslide occurrence, but expert judgment is included in the EWS to avoid false alarms. A case study shows the applicability and reliability for landslide risk management, and recommendations are presented for other similar projects. © 2015, Science Press, Institute of Mountain Hazards and Environment, CAS and Springer-Verlag Berlin Heidelberg. Source

Li Y.,Chongqing University | Li Y.,Taiyuan University of Technology | Li Y.,AGECON Ltd. | Huang D.,Chongqing University | And 2 more authors.
Rock Mechanics and Rock Engineering | Year: 2014

Strain rate during testing, uniaxial or triaxial, has important influence on the measured mechanical properties of rocks. Uniaxial compression tests were performed at nine pre-specified static-to-quasistatic strain rates (ranging from 1 × 10-5 to 1 × 10-1 s-1) on coarse crystal marble. The aim is to gain deep insight into the influence of strain rate on characteristic stresses, deformation properties and conversion of strain energy of such rock. It is found that the strain rate of 5 × 10-3 s-1 is the threshold to delineate the failure modes the tested coarse marble behaves in. At a strain rate less than this threshold, single-plane shear and conjugate X-shaped shear are the main failure modes, while beyond this threshold, extensile and splitting failures are dominant. The stress for crack initiation, the critical stress for dilation, the peak stress, and Young's modulus are all found to increase with strain rate, with an exception that the above stresses and modulus appear relatively low compared to the strain rate in the range of between 1 × 10-4 and 5 × 10-3 s-1. The pre-peak absorbed strain energy, damage strain energy and elastic strain energy are found to increase with strain rate. In addition, the elastic strain energy stored before peak point favors brittle failure of the specimen, as the more stored elastic energy in the specimen, the stronger the fragmenting. © 2013 Springer-Verlag Wien. Source

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