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Xu P.,Zhengzhou University | Xu P.,China Construction Seventh Engineering Division Corporation Ltd. | Han Y.,Zhengzhou Rail Traffic Co. | Duan H.,China Railway 11th Bureau Group Co. | Fang S.,China Railway 11th Bureau Group Co.
Geotechnical and Geological Engineering | Year: 2015

Zhengzhou is a second-tier cities in P. R. China and is just located at Yellow River alluvial landforms where the soils are divided into four strata combinations of flood alluvial deposit based on the lithology, sedimentary environment and geomorphic units. Zijingshan Station is one of the most important stations of the total subway lines in Zhengzhou, the first and second subway lines join together at Zijingshan Station, the transfer station foundation pit has the maximum depth of 31.2 m under the ground surface and is now the deepest one in Henan Province that Zhengzhou is belonged to, and so to monitor and analyze the environmental effects induced by this type of deep foundation pit excavation is necessary and important for the foundation pits of similar deep subway stations and buildings in future. During Zijingshan Station foundation pit excavation and main station structure construction, water tables, settlements and lateral deformations around the transfer section and standard section were all measured and analyzed in time, and some conclusions are drawn out, which are that (1) the water tables are controlled to be stable when artificial ground freezing was adopted and the stable changing ratios are all <0.7 mm/day, (2) the maximum ground settlement is not adjacent to the underground continuous walls but at the overpass bridge pier with a certain distance away from the foundation pit edge, which is seriously affected by both large traffic flows and foundation pit excavation, (3) the maximum lateral deformations of the standard section are focused at the position of about 3.0 m under the ground surface, while those of the transfer section are at about 11.0 m under the ground surface; (4) the measured and monitored items such as stable water table decreasing ratio, maximum settlements and lateral deformations all meet with the local building foundation specifications. The first subway line of Zhengzhou that contains Zijingshan Station has been put to use, the environmental effects caused by foundation pit excavation are all controlled to be stable until now, and so underground continuous walls and horizontal supports are the prior selection for the deep foundation pit in Yellow River alluvial landforms. © 2015, Springer International Publishing Switzerland.

Bai Y.,Southwest Jiaotong University | Qi T.,Southwest Jiaotong University | Li Y.,China Railway 11th Bureau Group Co. | Wu Z.,Southwest Jiaotong University
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2013

When shield crossed the sandy cobble stratum in Chengdu metro No.1 and No.2 lines, the induced surface subsidence reached as high as dozens of times. Surface collapse deformation curve is influenced by many factors, and the influences of the factors on surface collapse deformation curve show the nonlinear characteristics. So the surface collapse deformation curve is difficult to solve with mathematical formulas. Least squares support vector is a machine learning method based on the statistical learning theory. It can avoid shortcomings of traditional neural network and analyze influencing rule on the result with complicated factors. Thereby least squares support vector machine method was introduced to establish prediction model for surface collapse deformation. Prediction model took physico-mechanical parameters of stratum, buried depth of shield and ground loss value as input parameters. Though testing sample data, the prediction mode has strong generalization ability, and its prediction result has high accuracy and reliability.

Li C.,Wuhan University | Li C.,China Railway 11th Bureau Group Co. | Wen G.,Wuhan University
Applied Mechanics and Materials | Year: 2012

The energy release and depressurization method is often used for the hidden cavity with extra big mass and high pressure in a tunnel. It is critical to determine the minimal depth of safe overburden for the release hole at lower position and the pressure at high position to be released. According to actual data collected from a cavity of Maluqing tunnel of Hubei, this paper performs the computer simulation and analysis for the safety of the release hole at lower position in the cavity and determines the critical safe depth to disclose the cavity is determined tentatively by using the finite differential software of FLAC3D. The simulated results in accord well with the actual situation show the rationality and validity of this numerical simulation. © (2012) Trans Tech Publications, Switzerland.

Li X.-Z.,China Three Gorges University | Li X.-Z.,Chongqing University | Wang G.-F.,China Railway 11th Bureau Group Co. | Li X.-L.,Transportation Group | Zhu Z.-R.,China Three Gorges University
Advanced Materials Research | Year: 2014

Taking Jin Chuan phyllite tunnel as the research object, and based on numerical simulation of surrounding rock graded III, IV and V, the paper studied the stress characteristics of initial support and four other representative locations such as two arch vault, arch spandrel, arch haunch, and arch foot during and after the process of construction. The paper focuses on the stress characteristics of secondary lining in different locations after stability and the change of stress in different locations of initial lining before and after the secondary lining construction. © (2014) Trans Tech Publications, Switzerland.

Huang M.,Fuzhou University | Zhang X.,China Railway 11th Bureau Group Co. | Xu M.-K.,Fuzhou University | Cai L.-Q.,Fuzhou University
Advanced Materials Research | Year: 2011

With 19 groups of data associated with inrush or bursting water from karst cavity, obtained from Yichang-Wanxian Railway Maluqing Tunnel field test, conceptual models of Karst Water Burst Flood (KWBF) was brought forward by statistical analysis and phenomenological induction. KWBF is super-large amount of artesian water together with mud, which statically deposited in karst cavity, suddenly released into tunnel. KWBF has 3 kinds of characteristic: large scale of cavity water, high hydraulic pressure, high bed load content, dynamic supply of ground water, strong destroyed power; no foreboding, paroxysmal and intermittence, antinomy between paroxysmal and arrearage; force majeure, difficulty forecast, etc. Forecasting of Karst Water Burst Flood is conducted with rainfall seeping theory and statistical analysis method, while the base data are obtained from field quantity observation technical such as rainfall, hydrograph measure. Because of pressure dispersion between inside and outside of the cavity, seepage enlarge is evolved into conflux so that deprive groundwater from aquifer aqueduct and fracture, so, the water together with mud release suddenly from karst into tunnel. The key effect factor on KWBF is water count and silted or filling degree of conflux aqueduct. It is the essential numerical criterion that the daily rainfall must be less than 20mm if construction in the tunnel after the karst cavity has been broken through. To evade risk during construction temporary stage and permanent working stage, measure of energy releasing and pressure reducing (ERPR) must be accept. In addition, it was suggested that the key parameter of risk control for karst tunnel is water count and its cumulating velocity, mechanics characteristic of bed load filling in the conflux aqueduct. © (2011) Trans Tech Publications, Switzerland.

Li X.Z.,Chongqing University | Li X.Z.,China Three Gorges University | Wang G.F.,China Railway 11th Bureau Group Co. | Zhu Z.R.,China Three Gorges University
Applied Mechanics and Materials | Year: 2014

Taking Liang Zhuang phyllite tunnel as the research object, the paper tries to analyze the variation rules of formation stress and initial support stress in the construction process based on numerical simulation of surrounding rocks grade III, IV and V, and also by using the measured data to have a better analysis of the stress state of surrounding rocks and support in the construction process, thus to grasp the rules for better construction. The result shows that the maximum compressive stress of initial support increases in the process of excavation, while the maximum formation stress is relatively stable in the process of excavation, with a slightly down trend, and whether there is a rock bolt or not, it doesn't have an obvious effect on the distribution and size of initial support stress. © (2014) Trans Tech Publications, Switzerland.

Xin-zhe L.,Chongqing University | Xin-zhe L.,China Three Gorges University | Geng-feng W.,China Railway 11th Bureau Group Co. | Zhen-qiang W.,Chongqing University
Electronic Journal of Geotechnical Engineering | Year: 2014

Soft rock tunnel, when constructed in traditional methods, often encounters with technical problems such as large deformation, non-convergence, and so on. This paper takes a certain water-enriched phyllite section of a tunnel as the study object, makes an in-situ study of the supporting system of the tunnel, and analyzes the stress state of the surrounding rock and supporting structure. The results indicate: (1) Deformation of the supporting structure increases sharply at the initial stage, and then becomes stable three weeks after the supporting structure has been constructed. (2) Shotcrete stress increases fast at the initial stage, and then becomes stable in about 15 days. (3) Steel arch stress increases sharply at the initial stage, and then becomes stable quickly. (4) Longitudinal link bar plays a certain role in maintaining the integrity and the stability of the tunnel supporting system. (5) In maintaining the stability of supporting system, the systematic rock bolts doesn't play an obvious role, but the feet-lock rock bolt does. © 2013, EJGE.

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