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Xiang C.-S.,Lanzhou University of Technology | Xiang C.-S.,Northwest Center for Disaster Mitigation in Civil Engineering | Jiang L.,China Railway 21st Bureau Group Co. | Li Q.-F.,Lanzhou University of Technology
Applied Mechanics and Materials | Year: 2012

The welding quality of the steel structure is one of the most important segments in the whole construction project, especially in the condition of special geographical environment and wicked climate. In this article, by means of the mechanical test and finite element simulation analysis, a welding treating technology has been summarized in the subzero surrounding, which is based on the fundamental of component size selecting, preheat, heat preservation, and change of the ambient temperature including the rising material temperature before welding. Therefore the thermal crack and cold crack can been effectively eliminated. Rigorous controlling the temperature of the welding procedure and scientific construction play an important role to ensure the welding quality of the big span truss beam and column. © (2012) Trans Tech Publications, Switzerland.

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.

Han Y.,Beijing Jiaotong University | Han Y.,China Railway First Survey and Design Institute Group Ltd. | Liu G.,China Railway First Survey and Design Institute Group Ltd. | 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.

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.

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.

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.-F.,Lanzhou University | Bu S.-M.,Lanzhou University | Wang S.-X.,China Railway 21st Bureau Group Co. | Jia M.-X.,Lanzhou University
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2015

Landslide is one of the most serious natural geological disasters. Its production condition is complicated, and it is influenced by various natural geological factors. For its evaluation of stability and selection of treatment scheme, the geophysical exploration method is often used to get the related geological information. In recent years, more and more engineering practices indicate that the single geophysical exploration method has the limitations such as inaccurate and intuitive information. The comprehensive geophysical prospecting method is widely used for its characteristics of comprehensive, rapid and rich information, and it is of great significance to selection of treatment scheme for the landslide. Based on Gaijiayin Mountain landslide on Lanzhou-Chongqing and combined with the landslide survey data, using the high-density resistivity method and the integrated geophysical exploration of the Rayleigh surface wave method the parameters such as velocity and resistivity are obtained, and the scope of the landslide slip surface, depth and sliding are further determined. The deformation, failure, development process and the relevant laws are understood so as to provide powerful evidence for the scheme determination of landslide governance. ©, 2015, Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering. All right reserved.

Lv Q.,Lanzhou University | Wang S.,Lanzhou University | Zhao Y.,China Railway 21st Bureau Group Co.
WIT Transactions on Ecology and the Environment | Year: 2014

Loess roadbed in seasonal frozen soil areas often suffers frequent freeze-thaw cycles which bring negative effects to loess structure and its permeability characteristics. This paper investigated permeability properties and microstructures of modified loess in different ratios of cement, lime and fly ash under the condition of freezing and thawing cycles and gave an optimal proportion of the three additives based on permeability properties. Permeability test results of modified loess are optimistic (around 10-7 cm/s order of magnitudes or lower) even the loess has been through repeated freeze-thaw cycles. The paper then provides a comprehensive suggestion for loess modification: cement of 4%-5% of loess weight, lime of 6% and fly ash of 10%. © 2013 WIT Press.

Jiang A.-N.,Dalian Maritime University | Li P.,Dalian Maritime University | Tang S.-L.,China Railway 21st Bureau Group Co. | Wang J.-X.,Dalian Maritime University
Yantu Lixue/Rock and Soil Mechanics | Year: 2012

Aiming at the conventional back analysis method easily being limited in local optimization and back analysis data being not visualized, a new global intelligent optimization arithmetic-difference evolution (DE) is introduced and combined with stress return mapping nonlinear elastoplastic finite element method(FEM), realizing rapid elastoplastic parameters identification of surrounding rock. Displaying the element stress, element strain and node displacement by image based on visual class library, the visual platform with high performance of tunnel construction back analysis has been realized. After the introduction of arithmetic theory and program design, the engineering application of the platform is also introduced. The application displays that the platform has high computing precision and has visualized computing result, which provides scientific and high effect mean for tunnel back analysis.

Zhao Y.-X.,Lanzhou University | Zhao Y.-X.,China Railway 21st Bureau Group Co. | Zhang H.-Y.,Lanzhou University | Lu Q.-F.,Lanzhou University | Liang X.-B.,Lanzhou University
Yantu Lixue/Rock and Soil Mechanics | Year: 2010

Unsaturated permeability coefficient of compacted loess is studied by the test system of hydraulic conductivity under different dry densities. The relationship between matric suction and permeability coefficient shows that the permeability coefficient decreases with suction increase nonlinearly, and increases with dry density decrease. It is found that dry density has more effect on the permeability coefficient in the low matrix suction than in the high matrix suction. It is indicated that from test results, the relation between permeability coefficient and matrix suction can be fitted with power function model under certain conditions. The relationship between dry densities and parameters is explored for estimating the coefficient of permeability of unsaturated compacted loess.

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