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Lv Q.-F.,Lanzhou University | Liu P.-F.,Lanzhou University | Zhao Y.-X.,China Railway 21st Bureau Group Co.
Advanced Materials Research | Year: 2014

Because of evapo-transpiration, compacted loess road embankments were considered to be in a partially saturated state in both arid and semi-arid regions. Based on previous studies and the theory of unsaturated soil mechanics, a numerical analysis of rainfall infiltration in a compacted loess road embankment was conducted. The transient seepage characteristics and moisture migration patterns of the moisture in the embankment were analysed. The results showed that after precipitation, the moisture profile of the compacted loess could be separated into three zones.The data also showed that: under the effect of gravity, the water continued to migrate into the embankment after the rainfall had ended. In time, the saturated zone became partially saturated as the moisture content decreased, whereas the moisture content in the conducting and humid zones increased and the wetting front moved downward. The data also showed that the depth of the conducting and humid zones increased in time, but that the moisture content in the conducting zone increased along a linear gradient with depth, while the moisture content in the humid zone decreased in a similar manner. © (2014) Trans Tech Publications, Switzerland.

Jiang A.N.,Dalian Maritime University | Wang S.Y.,University of Newcastle | Tang S.L.,China Railway 21st Bureau Group Co.
Automation in Construction | Year: 2011

Feedback controls for tunnel construction require identifying geomechanical parameters and adjusting supporting parameters, both of which are optimisation problems. This paper presents an integrated optimisation method for the feedback control of tunnel displacement; it combines the Support Vector Machine (SVM), particle swarm optimisation (PSO) and numerical analysis methods. Initially, the nonlinear relationship between parameters and displacements is efficiently represented by SVM. Numerical analysis is then used to create training and testing samples for SVM recognition. PSO is used to search on the parameters of SVM and to obtain the geomechanical and support parameters. A case study is provided to verify the proposed methodology. This study provides an alternative means for adjusting tunnel construction schemes based on field observations and the optimisation of quantitative integration. © 2010 Elsevier B.V. All rights reserved.

Lu Q.,Lanzhou University | Li X.,Lanzhou University | Zhao Y.,China Railway 21st Bureau Group Co. | Wang S.,Gansu Academy of science
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2014

The modified loess physical and mechanical characteristics such as unconfined compressive strength, permeability coefficient and microstructure were tested under the freeze-thaw cycles of modified loess. According to the comprehensive strength, permeability and freeze-thaw resistance performance of the modified loess, the optimal ratio of the modifier and the influence of freeze-thaw in practical application were proposed. The results show that the loess by adding 4%-5% cement, 6% lime and 10% fly ash can not only has higher compressive strength and lower permeability coefficient, but also can avoid the decreasing of freeze-thaw resistance ability caused by its large stiffness. The micro experiment indicates that combined effect of the three modifiers can change arrangement and bond of soil particles, thus the strength and freeze-thaw resistance ability of modified loess are reinforced.

Han Y.,Beijing Jiaotong University | Han Y.,China Railway First Survey and Design Institute Group Co. | Liu G.,China Railway First Survey and Design Institute Group Co. | Li S.,China Railway 21st Bureau Group Co. | Wang X.,Beijing Jiaotong University
Modern Tunnelling Technology | Year: 2013

Considering the characteristics of water-bearing and slightly cemented sandstone, a double pilot tunnel construction method is proposed using the pros and cons of different conventional construction methods based on the No.3 inclined shaft of the Taoshuping Tunnel on the Lanzhou-Chongqing Railway. Using FLAC3D numerical analysis software, the regularities of ground deformation and the stress condition of the supporting structure during pilot tunnel construction were studied regarding actual geological conditions. The influence of different excavation steps was analyzed. Finally, the most dangerous part of the supporting structure was analyzed. The importance of dewatering in this type of ground is addressed. This study and its application results show that this construction method could control ground deformation effectively.

Tang S.,China Railway 21st Bureau Group Co. | Jiang A.,Dalian Maritime University | Zhao H.,Dalian Maritime University
Advanced Materials Research | Year: 2011

Aiming at the problems of conventional underground engineering feedback analysis methods, such as being limited in local optimization and computing data being very complex, the paper introduced difference evolution arithmetic and visualization toolkit, and combined three dimensional numerical simulation and orthogonal design, developing the intelligent feedback analysis system based on Visual c#. The system theory, software frame and develop method are introduced, the system could be used to calculate and evaluate the state of tunnel surrounding rock based on in-situ monitoring data. The system is applied in an actual tunnel engineering, the analysis results are satisfied, which states it is feasible and has good potential application. © (2011) Trans Tech Publications.

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