scholarly journals Mechanical Characteristics of Structures and Ground Deformation Caused by Shield Tunneling Under-Passing Highways in Complex Geological Conditions Based on the MJS Method

2021 ◽  
Vol 11 (19) ◽  
pp. 9323
Author(s):  
Zikun Li ◽  
Jianbing Lv ◽  
Xiaodong Xie ◽  
Helin Fu ◽  
Juan Huang ◽  
...  
Keyword(s):  
Mechanical Characteristics ◽  
Ground Deformation ◽  
Soft Rock ◽  
Ground Subsidence ◽  
Height Ratio ◽  
Shield Tunneling ◽  
Shortest Distance ◽  
Geological Conditions ◽  
Narrow Space ◽  
Rock Strata

This study defined the height ratio of soft-rock strata and established a numerical model for analyzing shield construction in upper-soft, lower-hard composite strata together with field monitoring data. In this way, the influence of shield tunneling while passing under the pile foundation of the culvert at a short distance (the shortest distance is 1.4 m) in the typical upper-soft, lower-hard composite strata in Guangzhou can be examined. Moreover, the reinforcement effects of the ground, the bridges, and the culverts, using the strata-reinforcing plan dominated by the metro jet system (MJS) in a narrow space, are evaluated. Based on the results, (i) the maximum ground subsidence is found at the position in which the height ratio of the soft rock is 1.0. (ii) However, differential subsidence might be found in the subsequent shield construction when the soft-rock height ratio of the adjacent excavated surface ranges from 0 to 0.2 and from 0.5 to 1. (iii) The concentrated release of stress has a greater impact on the structure than the geological conditions of the shield tunneling face. (iv) Reinforcing with the MJS method contains the concentrated release of stress. This study can provide a reference for controlling the deformation of the under-crossing structure in the shield construction of the upper-soft, lower-hard composite strata.

Analysis on the Mechanical Behavior of Pipe Roof and Rock Bolt of Shallow and Unsymmetrical Tunnel in Soft Rock

2012 ◽  
Vol 443-444 ◽  
pp. 267-271
Author(s):  
Xu Dong Cheng ◽  
Peng Ju Qin
Keyword(s):  
Soft Rock ◽  
Surrounding Rock ◽  
Mechanical Behaviors ◽  
Maximum Displacement ◽  
Tunnel Excavation ◽  
Finite Element Software ◽  
Highway Tunnel ◽  
Geological Conditions ◽  
The Impact ◽  
Rock Strata

In this paper, the mechanical behaviors of pipe roof and bolt of shallow and unsymmetrical tunnel in soft rock are analyzed. Through the finite element software Phase2.0, combined with the geological conditions that construction site often appear, the mechanical behaviors of pipe roof and bolt and surrounding rock in the process of horseshoe highway tunnel construction in the condition that surface is soft rock and underground for the bedrock are analyzed. Research results show that: after tunnel excavation in soft rock, surrounding rock near the tunnel is easy to suffer soft-rock large deformation even failure, which needs to timely support；Due to the impact of the unsymmetrical tunnel, the mechanical behaviors of surrounding rock are unsymmetrical, such as the maximum displacement of tunnel around 0.4 m distant from apex of arch ring, the stress is asymmetrical on both sides of the tunnel arch ring etc; In addition, pipe roof can effectively prevent from the displacement of soft rock strata, improve tunnel strength factor, reduce the plastic zone of surrounding rock. This paper provides theoretical basis for the design of pipe roof and bolt.

scholarly journals Land subsidence inversion method application for salt mining-induced rock mass movement

2017 ◽  
Vol 33 (3) ◽  
pp. 179-200 ◽  
Author(s):  
Ryszard Hejmanowski ◽  
Agnieszka A. Malinowska
Keyword(s):  
Land Subsidence ◽  
Least Squares Method ◽  
Underground Mining ◽  
Ground Deformation ◽  
Mass Movement ◽  
Ground Movement ◽  
Ground Subsidence ◽  
Inversion Method ◽  
Salt Mines ◽  
Geological Conditions

AbstractThe modeling of strains and deformations in salt mine areas encounters considerable difficulties because of the varying strength properties of salt, the complex morphological build of dome deposits and the rheological properties of salt. These properties have impacted the development of salt extraction for hundreds of years and the fact that the accurate determining of strains in a given specified moment and place are burdened with high uncertainty. Numerical modeling is useful when the model is reduced to one or several salt chambers. A broader range of underground post mining void considerably lowers the accuracy and efficiency of the calculations of such models. Stochastic models allow for a 3D modeling of the entire mining complex deposit, provided the model has been parametrized in detail. The methods of strains and deformations modeling were presented on the example of one of the biggest salt mines in Europe, where a volume of over 21 million m3 of salt was extracted. The stochastic model could be parametrized thanks to the documented results of measurements of convergence of the underground mining panels and leveling on the surface. The use of land subsidence inversion in the least squares method allowed for estimating the optimum values of parameters of the model. Ground deformation modeling was performed using the two-parameter time function, which allows for a simulation to be carried out in time. In the simulation, the convergence of underground excavations and the transition in time the effects of convergence into ground subsidence was taken into account. The detailed analysis of the geological conditions lead to modeling deviation of the subsidence trough. The accuracy of the modeling results was qualitatively and quantitatively confirmed by a comparison of the modeled to measured values of the vertical ground movement. The scaled model can be applied in future mining extraction projects in order to predict the strains and deformations for an arbitrary moment in time.

scholarly journals Subsidence Monitoring of Fill Area in Yan’an New District Based on Sentinel-1A Time Series Imagery

2021 ◽  
Vol 13 (15) ◽  
pp. 3044
Author(s):  
Mingjie Liao ◽  
Rui Zhang ◽  
Jichao Lv ◽  
Bin Yu ◽  
Jiatai Pang ◽  
...  
Keyword(s):  
Time Series ◽  
Large Scale ◽  
Ground Deformation ◽  
Dynamic Change ◽  
Deformation Monitoring ◽  
Chinese Loess Plateau ◽  
Ground Subsidence ◽  
Shanxi Province ◽  
Environment Change ◽  
Loess Area

In recent years, many cities in the Chinese loess plateau (especially in Shanxi province) have encountered ground subsidence problems due to the construction of underground projects and the exploitation of underground resources. With the completion of the world’s largest geotechnical project, called “mountain excavation and city construction,” in a collapsible loess area, the Yan’an city also appeared to have uneven ground subsidence. To obtain the spatial distribution characteristics and the time-series evolution trend of the subsidence, we selected Yan’an New District (YAND) as the specific study area and presented an improved time-series InSAR (TS-InSAR) method for experimental research. Based on 89 Sentinel-1A images collected between December 2017 to December 2020, we conducted comprehensive research and analysis on the spatial and temporal evolution of surface subsidence in YAND. The monitoring results showed that the YAND is relatively stable in general, with deformation rates mainly in the range of −10 to 10 mm/yr. However, three significant subsidence funnels existed in the fill area, with a maximum subsidence rate of 100 mm/yr. From 2017 to 2020, the subsidence funnels enlarged, and their subsidence rates accelerated. Further analysis proved that the main factors induced the severe ground subsidence in the study area, including the compressibility and collapsibility of loess, rapid urban construction, geological environment change, traffic circulation load, and dynamic change of groundwater. The experimental results indicated that the improved TS-InSAR method is adaptive to monitoring uneven subsidence of deep loess area. Moreover, related data and information would provide reference to the large-scale ground deformation monitoring and in similar loess areas.

Numerical Analysis of Metro Station Construction by Large-Diameter Shield and Pile-Beam-Arch Method

2011 ◽  
Vol 368-373 ◽  
pp. 2711-2715 ◽  
Author(s):  
De Yun Ding ◽  
Xiu Ren Yang ◽  
Wei Dong Lu ◽  
Wei Ning Liu ◽  
Mei Yan ◽  
...  
Keyword(s):  
Ground Deformation ◽  
Large Diameter ◽  
Element Model ◽  
Construction Method ◽  
Shield Tunnel ◽  
Outer Diameter ◽  
Shield Tunneling ◽  
Metro Station ◽  
Dimensional Finite Element ◽  
New Construction

In more and more complicated urban building environment, a new construction method that metro engineering is constructed by large-diameter shield and shallow mining method can be regarded as a great attempt in China. By taking the Gaojiayuan station of Beijing metro line 14 as an engineering background, the main construction steps for the platform of the metro station built by a large-size shield with an outer diameter of 10 m and the Pile-Beam-Arch (PBA) method are introduced. Based on the soil-structure interaction theory, a two-dimensional finite element model is used to simulate the shield tunneling and the platform construction by the PBA method to enlarge the shield tunnel. The ground deformation and structural stress of the platform are predicted. The numerical results can be regarded as a valuable reference for the application of the new construction method in Beijing metro line 14.

scholarly journals A Comprehensive Review of the Mechanical Behavior of Suspension Bridge Tunnel-Type Anchorage

2019 ◽  
Vol 2019 ◽  
pp. 1-19 ◽  
Author(s):  
Yafeng Han ◽  
Xinrong Liu ◽  
Ning Wei ◽  
Dongliang Li ◽  
Zhiyun Deng ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Failure Modes ◽  
Load Transfer ◽  
Mechanical Response ◽  
Soft Rock ◽  
Suspension Bridge ◽  
Development Trend ◽  
Factors Affecting ◽  
Research Results ◽  
Rock Strata

The recent surge of interest towards the mechanical response of rock mass produced by tunnel-type anchorage (TTA) has generated a handful of theories and an array of empirical explorations on the topic. However, none of these have attempted to arrange the existing achievements in a systematic way. The present work puts forward an integrative framework laid out over three levels of explanation and practical approach, mechanical behavior, and calculation method of the ultimate pullout force to compare and integrate the existing findings in a meaningful way. First, it reviews the application of TTA in China and analyzes its future development trend. Then, it summarizes the research results of TTA in terms of load transfer characteristics, deformation characteristics, failure modes, and calculation of ultimate uplift resistance. Finally, it introduces four field model tests in soft rock (mainly mudstone formations), and some research results are obtained. Furthermore, it compares the mechanical behavior of TTA in hard rock strata and soft rock strata, highlighting the main factors affecting the stability of TTA in soft rock formation. This paper proposes a series of focused topics for future investigation that would allow deconstruction of the drivers and constraints of the development of TTA.

scholarly journals Front Stress Distribution Under the Impact of Cutting Height to Caving Height Ratio in Extra-thick Longwall Top Coal Caving Technology

2020 ◽  
Vol 1 (2) ◽  
Author(s):  
Bui MANH TUNG ◽  
Nguyen VAN QUANG ◽  
Nguyen PHI HUNG ◽  
Vo NGOC DUNG ◽  
Do HOANG HIEP
Keyword(s):  
Stress Distribution ◽  
Peak Stress ◽  
Height Ratio ◽  
Research Orientation ◽  
Geological Conditions ◽  
The Face ◽  
New Research ◽  
Longwall Top Coal Caving ◽  
Cutting Height ◽  
The Impact

The extraction with higher cutting height for extra-thick seam is the new research orientation in longwall caving technology. Due to the increase of top coal thickness and of cutting height which leads to the change of cutting/caving height ratio, the rule of roof failure (including top coal caving) and the distribution of stress around the face alter correspondingly. This paper is based on the geological conditions of face 8102 of Tashan-DaTong mine, employing the numerical model by UDEC2D code, analysing the effect of cutting/caving height ratio on the law of stress distribution ahead of the face. When the ratio of cutting/caving height decreases and the cutting height increases, the results of the research have shown that: (i)- peak stress redistributes further ahead of the face and its value manifestly drops; (ii)- the plastic deformation ahead of face significant increases and the zone of plastic strain also expands. It is therefore concluded that the variation of cutting/caving height ratio results in the redistribution of roof pressure, which contributes to the control of roof failure and face stability.

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