AGECON Ltd.

Hong Kong, China

AGECON Ltd.

Hong Kong, China

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Meng L.,Chengdu University of Technology | Li T.,Chengdu University of Technology | Jiang Y.,Quality Supervision Station of Sichuan | Wang R.,Southwest Subsidiary Company of China Airport | Li Y.,AGECON Ltd.
Tunnelling and Underground Space Technology | Year: 2013

The Zhegu mountain tunnel is a typical long, deep-buried highway tunnel at a high altitude, subjected to low temperatures and high geostress. The tunnel is excavated in carbon phyllite and slate at depths of up to 1000. m below ground, which has resulted in extreme deformation, especially in a depth of 3. m from the tunnel perimeter. The maximum deformation was monitored to be 60. cm, with a maximum deformation speed of 39.3. mm/day. In addition, it took 60-120. days to complete 90% of the deformation. The deformation of the Zhegu mountain tunnel is characterized by serious subsidence of the arch, squeezing outwards of sidewalls, buckling failure of sidewalls and local collapse. The swelling of soft rock is found not to be a main factor of large deformation in the subject tunnel. Three mechanisms of large deformation are derived based on the characteristics and geological conditions, which are plastic flow of soft rock, shear sliding of wedges, and bending of thin-layered soft rock. © 2013.


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.


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.


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.


Li Y.,Taiyuan University of Technology | Li Y.,AGECON Ltd.
Bulletin of Engineering Geology and the Environment | Year: 2013

The effects of particle shape and size distribution on the constitutive behavior of composite soils with a wide range of particle size were investigated. Two comparable sets of specimens were prepared: (1) mixtures of fines (clay and silt) and an ideal coarse fraction (glass sand and beads), and (2) mixtures of fines and natural coarse fraction (river sand and crushed granite gravels). Direct shear box testing was undertaken on 34 samples and the structure of the shear surfaces, change in volume and water content and the particle shape coefficient of the sheared specimens were examined. The results indicate that the contraction/dilation a specimen exhibits is restrained within the shear zone while the outer zones remain unchanged during shearing. An increased coarse fraction leads to an increase in constant volume shear strength. In addition, increasing elongation or decreasing convexity of the coarse fraction increases the constant volume friction angle. The overall roughness of the shear surface at constant volume state is negatively related to particle smoothness (convexity) and positively related to the area of the shear surface occupied by particles with particular shapes. Two equations are proposed for the estimation of constant volume friction angle based on the proportion and shape coefficient of the coarse fraction. It is hoped this will assist in considering the shear strength of mixed soils when the size of the coarse fraction makes laboratory testing difficult. © 2013 Springer-Verlag Berlin Heidelberg.


Liu H.-X.,Chengdu University of Technology | Xu Q.,Chengdu University of Technology | Li Y.-R.,AGECON Ltd.
Journal of Mountain Science | Year: 2014

Studies on landslides by the 2008 Wenchuan earthquake showed that topography was of great importance in amplifying the seismic shaking, and among other factors, lithology and slope structure controlled the spatial occurrence of slope failures. The present study carried out experiments on four rock slopes with steep angle of 60° by means of a shaking table. The recorded Wenchuan earthquake waves were scaled to excite the model slopes. Measurements from accelerometers installed on free surface of the model slope were analyzed, with much effort on time-domain acceleration responses to horizontal components of seismic shaking. It was found that the amplification factor of peak horizontal acceleration, RPHA, was increasing with elevation of each model slope, though the upper and lower halves of the slope exhibited different increasing patterns. As excitation intensity was increased, the drastic deterioration of the inner structure of each slope caused the sudden increase of RPHA in the upper slope part. In addition, the model simulating the soft rock slope produced the larger RPHA than the model simulating the hard rock slope by a maximum factor of 2.6. The layered model slope also produced the larger RPHA than the homogeneous model slope by a maximum factor of 2.7. The upper half of a slope was influenced more seriously by the effect of lithology, while the lower half was influenced more seriously by the effect of slope structure. © 2014, Science Press, Institute of Mountain Hazards and Environment, CAS and Springer-Verlag Berlin Heidelberg.


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.


Wang X.Q.,Chengdu University of Technology | Li Y.R.,Taiyuan University of Technology | Li Y.R.,AGECON Ltd. | Yuan Y.,Chengdu University of Technology | And 2 more authors.
Natural Hazards and Earth System Sciences | Year: 2014

Studies on the formation of the ancient Diexi barrier lake on the Mingjiang River, southwestern China, have long been carried out. However, investigations into the correlation between the palaeoclimate and palaeoenvironment and the palaeoseismic events in this area are rarely found in literature. The present study took sediments from the ancient Diexi barrier lake to investigate the palaeoclimate, palaeoenvironment and palaeoseismic events. A drilling at the centre of the barrier lake was conducted and the core of about 260 m long was examined. The palaeoclimate and palaeoenvironment indicators (sporopollen, carbon and oxygen isotopes, organic matter, calcium carbonate, granularity) from the sediments have been tested and analysed, and indicate that there were 10 climatic and environmental periods between 30 000 and 15 000 a BP (before present). The discovered disturbance segments in the core indicate there were at least 10 seismic events during that period. The consistency between climate change and seismic events indicates that a strong seismicity is normally accompanied by a climatic variation. This may be a useful supplement for climate and geohazard predictions in the future. © Author(s) 2014.


Yuan J.K.,Chengdu University of Technology | Li Y.R.,Taiyuan University of Technology | Li Y.R.,AGECON Ltd. | Huang R.Q.,Chengdu University of Technology | Pei X.J.,Chengdu University of Technology
Natural Hazards and Earth System Sciences | Year: 2015

The determination of rockfall impact force is crucial in designing protection measures. In the present study, laboratory tests are carried out by testing the weight and shape of the falling rock fragments, drop height, incident angle, platform on the slideway, and cushion layer on the protection measures to investigate their influences on the impact force. The test results indicate that the impact force is positively exponential to the weight of rockfall and the instantaneous impact velocity of the rockfall approaching the protection measures. The impact velocity is found to be dominated not only by the drop height but also by the shape of rockfall and the length of the platform on the slideway. A great drop height and/or a short platform produces a fast impact velocity. Spherical rockfalls experience a greater impact velocity than cubes and elongated cuboids. A layer of cushion on the protection measures may reduce the impact force to a greater extent. The reduction effects are dominated by the cushion material and the thickness of the cushion layer. The thicker the cushion layer, the greater the reduction effect and the less the impact force. The stiffer the buffer material, the lower the buffering effect and the greater the impact force. The present study indicates that the current standard in China for designing protection measures may overestimate the impact force by not taking into consideration the rockfall shape, platform, and cushion layer. © Author(s) 2015.


Li Y.,Taiyuan University of Technology | Li Y.,AGECON Ltd. | Huang R.,Chengdu University of Technology
International Journal of Rock Mechanics and Mining Sciences | Year: 2015

Numerous empirical equations have been proposed to estimate the joint roughness coefficient (JRC) of a rock fracture based on its fractal dimension (D). A detailed review is made on these various methods, along with a discussion about their usability and limitations. It is found that great variation exists among the previously proposed equations. This is partially because of the limited number of data points used to derive these equations, and partially because of the inconsistency in the methods for determining D. The 10 standard profiles on which most previous equations are based are probably too few for deriving a reliable correlation. Different methods may give different values of D for a given profile. The h- L method is updated in this study to avoid subjectivity involved in identifying the high-order asperities. The compass-walking, box-counting and the updated h- L method are employed to examine a larger population of 112 rock joint profiles. Based on these results, a new set of empirical equations are proposed, which indicate that the fractal dimension estimated from compass-walking and the updated h- L method closely relate to JRC, whereas the values estimated from box-counting do not relate as closely. © 2015 Elsevier Ltd.

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