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Geng P.,Southwest Jiaotong University | Quan Q.,Tianjin Municipal Engineering Design & Research Institute | Wang S.,Southwest Jiaotong University | An J.,Southwest Jiaotong University | Yan Q.,Southwest Jiaotong University
Modern Tunnelling Technology | Year: 2015

Mud and water bursts are common phenomena when tunnels pass through water-rich fault zones and are serious disasters encountered during tunnel construction. In order to explore the formation process of mud and water bursts in tunnels and the influence of fault dip angles on the formation process in order to avoid serious engineering disasters, the processes of mud and water bursts induced by tunnelling in water-rich fault zones with different dip angels were simulated by Discrete Element Method (DEM) based on coupling the particle and fluid. In the simulation process, the development of fractures in surrounding rocks and the amounts of inrushing mud and water were traced and recorded, the formation processes of the mud- and water-bursting channels were analyzed, and the influence of fault dip angles on mud and water bursts was revealed. The study shows that the smaller the fault dip angles, the shorter the vertical distances between the fault and tunnel, and the more likely that mud and water bursts will occur and concentrate at the bottom of the working face. The study results provide a reference for the design of tunnel excavations in water-rich fault zones as well as for the forecast and prevention of mud and water bursts. ©, 2015, Editorial Office of "Modern Tunnelling Technology". All right reserved. Source


Chen J.,Central South University | Zhang J.,Central South University | Li J.,Tianjin Municipal Engineering Design & Research Institute
Sichuan Daxue Xuebao (Gongcheng Kexue Ban)/Journal of Sichuan University (Engineering Science Edition) | Year: 2015

A new method for the definition and measurement of roughness of soil-structure interface was proposed based on reversing the roughness measured by sand filling method. The new method, sand filling method and the method for the measurement of peak-valley distance were used to measure the roughness of the surfaces with semi-circle grooves made by the test and the surface with tooth grooves made by the other research scholars. The comparisons were made according to the results of measurement. The direct shear tests on the interface of red clay-concrete block were carried out using the large-scale direct apparatus. The effects of roughness on the interface characteristics of shear failure and deformation were studied by quantitative analysis and the effect mechanism of roughness were discussed. The results indicated that, for the measurement of roughness of interface, the new method suggested by this paper is more effective than both sand filling method and the method for the measurement of peak-valley distance. The shear failure of interface agrees well with the Mohr-Coulomb strength failure criterion. The roughness has little effects on the internal friction angle. The growth rates of the shear strength and the cohesion reduce with the increment of roughness of interface. With the increment of roughness of interface, the cohesion of interface increases until it approaches to the cohesion of red clay. If the cohesion of interface approaches to that of red clay, the shear failure may occur on the interface or in the soil near the interface. With the increment of the normal stress, the critical roughness decreases, meanwhile, the effects of roughness on shear strength of interface reduce. When the roughness of interface is low, the stress-dropping phenomenon is shown after the shear failure occurs. ©, 2015, Editorial Department of Journal of Sichuan University. All right reserved. Source


Chen J.,Central South University | Zhang J.,Central South University | Li J.,Central South University | Li J.,Tianjin Municipal Engineering Design & Research Institute
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2016

Concrete block surface with different roughness were made and the surface was used as the soil-concrete interface. The interface roughness was measured by sand filling method. The direct shear tests on the interface of red clay-block by using the large-direct shear apparatus were carried out. The influences of interface roughness on the parameters of shear strength, the relationships between shear stress and tangential displacement and the behavior of shear dilatancy & shear shrinkage were studied by quantitative analysis of roughness. The results show that the interface roughness has little influence on the angle of internal friction of red clay-concrete interface. With the interface roughness approaching its marginal value, cohesion of red clay-concrete interface increases with the increase of roughness and its value is approaching that of red clay. The interface roughness has a great influence on the relationships between shear stress and tangential displacement. There is the zone above the interface, in the soil, in which the mechanical properties are affected by the interface roughness. The zone expands with the increment of interface roughness until it reaches the maximum when the roughness also reaches or exceeds its marginal value. The behavior of shear dilatancy of the red clay is shown when the normal stress is low. The interface roughness has little influence on the behavior of shear dilatancy & shear shrinkage of red clay. © 2016, Central South University of Technology. All right reserved. Source


Zhang H.,Tianjin University | Zhai H.,Tianjin University | Ji M.,Tianjin University | Su X.,Tianjin University | And 2 more authors.
Desalination and Water Treatment | Year: 2015

Chromium (Cr) is a toxic compound in wastewater and can cause inhibitory effects on nitrification in a biological treatment system. However, different long-term inhibitory effects of Cr(VI) on ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were seldom investigated in activated sludge systems. In this study, the influences of 1−10 mg/L Cr(VI) on bioactivities and quantities of AOB and NOB in long-term inhibition and recovery periods were investigated. The transformation of inorganic nitrogen, fluorescence in situ hybridization assay for analyzing micro-organism population, and specific oxygen uptake rates of activated sludge were examined. Results show that the inhibitory effect of Cr(VI) on nitrification increased with the Cr(VI) loading concentration and running cycle. The inhibited nitrification can be gradually recovered in a recovery period despite of a high accumulation of Cr (including Cr(VI) and Cr(III)) in activated sludge. AOB were more sensitive than NOB to Cr(VI). AOB recovered fast both in activity and quantity. NOB recovered more slowly than AOB. © 2014, © 2014 Balaban Desalination Publications. All rights reserved. Source


Qian J.,Tongji University | Sun C.,Tongji University | Sun C.,Tianjin Municipal Engineering Design & Research Institute | Zhao H.,Tongji University
Wuhan Ligong Daxue Xuebao (Jiaotong Kexue Yu Gongcheng Ban)/Journal of Wuhan University of Technology (Transportation Science and Engineering) | Year: 2016

Flexible pavement PCI prediction model is a core content in the pavement management system. A PCI-SVM (support vector machine) prediction method with prior knowledge incorporated is proposed in this paper. By the study of prior knowledge such as the PCI deterioration mode and model, the shortcoming that the traditional time series method is not applicable to PCI mutation is overcome. Finally, the above method is validated by PCI data of Shanghai rounding highway, which shows that the average relative error within three years is 1.67% in single SVM extrapolation prediction. Therefore, the proposed method has the advantages of scientific reliability and promising application potential. © 2016, Editorial Department of Journal of Wuhan University of Technology. All right reserved. Source

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