scholarly journals Study on Mechanical Characteristics of Segmental Joints of a Large-Diameter Shield Tunnel under Ultrahigh Water Pressure

Sensors ◽  
2021 ◽  
Vol 21 (24) ◽  
pp. 8392
Author(s):  
Lei Kou ◽  
Zhihui Xiong ◽  
Hao Cui ◽  
Jinjie Zhao
Keyword(s):  
Numerical Simulation ◽  
Theoretical Calculation ◽  
Water Pressure ◽  
Concrete Strength ◽  
Large Diameter ◽  
Simulation Method ◽  
High Water ◽  
Calculation Model ◽  
Bending Stiffness ◽  
High Water Pressure

At present, there is no clear design standard for segmental joints of large-diameter shield tunnels under high water pressure. In this paper, a theoretical calculation model for the bending stiffness of segmental joints under high water pressure is proposed. The numerical simulation method is used to investigate the failure and crack formation processes of single-layer and double-layer lining segments under large axial forces. The effects of axial force, bolt strength, and concrete strength on the bending stiffness of joints are then studied using a theoretical calculation model of segmental joints. The results show that under extremely high water pressure, the influence of double lining on joint stiffness is limited. It is more rational and safe to compute the bending stiffness of segmental joints using this theoretical model rather than the numerical simulation method. The parameter analysis reveals that increasing the bolt strength has a minor impact on bending stiffness and deformation, whereas increasing the concrete strength has the opposite effect. The influence of ultimate bearing capacity and deformation decreases non-linearly as the axial force increases.

scholarly journals Numerical Simulation Three-Dimensional Nonlinear Seepage in a Pumped-Storage Power Station: Case Study

Energies ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 180 ◽  
Author(s):  
Shaohua Hu ◽  
Xinlong Zhou ◽  
Yi Luo ◽  
Guang Zhang
Keyword(s):  
Numerical Simulation ◽  
Water Pressure ◽  
Flow Theory ◽  
High Water ◽  
Control Measures ◽  
Nonlinear Flow ◽  
Heaviside Function ◽  
Power Station ◽  
Pumped Storage ◽  
High Water Pressure

Due to high water pressure in the concrete reinforced hydraulic tunnels, surrounding rocks are confronted with nonlinear seepage problem in the pumped storage power station. In this study, to conduct nonlinear seepage numerical simulation, a nonlinear seepage numerical model combining the Forchheimer nonlinear flow theory, the discrete variational inequality formulation of Signorini’s type and an adaptive penalized Heaviside function is established. This numerical seepage model is employed to the seepage analysis of the hydraulic tunnel surrounding rocks in the Yangjiang pumped-storage power station, which is the highest water pressure tunnel under construction in China. Moreover, the permeability of the surrounding rocks under high water pressure is determined by high pressure packer test and its approximate analytical model. It is shown that the flow in the surrounding rocks is particularly prone to become nonlinear as a result of the high flow velocities and hydraulic gradients in the nearby of the seepage-control measures and the high permeability fault. The nonlinear flow theory generates smaller flow rate than the Darcy flow theory. With the increase of nonlinear flow, this observation would become more remarkable.

scholarly journals A Study on Lining Design of Earth Tunnels with Large Diameter Under High Water Pressure.

1996 ◽  
pp. 123-133
Author(s):  
Hiroshi Motoyama ◽  
Yujiro Wasa ◽  
Makoto Kanai ◽  
Kouji Yoshida
Keyword(s):  
Water Pressure ◽  
Large Diameter ◽  
High Water ◽  
High Water Pressure

scholarly journals Numerical Simulation of Cracking Failure and Weakening Law of Roadway Surrounding Rock under High Stress

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Feng Cheng ◽  
Ai-jun Chen ◽  
Di Wu ◽  
Xian-yuan Tang ◽  
Chun-hui Su
Keyword(s):  
Numerical Simulation ◽  
Plastic Zone ◽  
Strain Softening ◽  
Water Pressure ◽  
High Stress ◽  
Simulation Method ◽  
High Water ◽  
Hydraulic Head ◽  
Effective Porosity ◽  
Metal Mine

In deep roadway mining, high water pressure causes rock mass cracking and weakens the overall strength, affecting the stability of underground metal mine mining roadways. Therefore, using a numerical simulation method, we analyzed the strain softening characteristics of rocks after the inflexion point of elasticity and studied the strain distribution and the minimum support resistance under high-pressure groundwater conditions. Considering the groundwater pressure and effective porosity on the strain softening characteristics of the surrounding rocks, we investigated the critical groundwater pressure under which the surrounding rocks would remain stable. Actual engineering verification helps to obtain the supporting characteristic curves under different influencing factors. We found that water pressure and effective porosity are the significant factors that decide the development scope of the plastic zone. The more significant the increase of the plastic zone, the more notable the changes in the support curve. Moreover, the plastic zone is likely to occur when the hydraulic head is between 30 and 50 m; when the hydraulic head exceeds 50 m, it is likely to produce a relaxation zone.

scholarly journals Influence of High Water Pressure on Static and Dynamic Compressive Strength of Concrete

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Jikai Zhou ◽  
Xiyao Zhao ◽  
Yu Nie ◽  
Yun Tian
Keyword(s):  
Compressive Strength ◽  
Moisture Content ◽  
Water Pressure ◽  
Concrete Strength ◽  
Reduction Rate ◽  
High Water ◽  
Influence Of Water ◽  
Apparent Strain ◽  
Dynamic Compressive Strength ◽  
High Water Pressure

In this paper, an experimental study was conducted on the influence of water pressure on concrete strength. Specimens were put in a self-designed device, applying 0–4 MPa water pressure on concrete, and then taken out for both static and dynamic compressive tests. Results showed that high water pressure caused inevitable damage to concrete, leading to 13.4% reduction in strength under 4 MPa water pressure. Specimens with lower strength grade were damaged more severely while under the same water pressure. Also, as water pressure increased, the moisture content of concrete grew linearly, and the trend for specimens with higher compressive strength was slower. A correlation was established between the water content increment and the reduction rate of strength. Moreover, the dynamic compressive strength decreased as water pressure increased but still higher than the static strength, illustrating an apparent strain rate effect. Meanwhile, water pressure and moisture content increment barely had any influence upon DIF within the testing conditions. Furthermore, equations for calculating both static and dynamic reduction rates of strength were built, based either on water pressure or on moisture content increment caused by that. Equations for strength prediction were also provided.

scholarly journals Structural modifications of lanthanum silicate oxyapatite exposed to high water pressure

2017 ◽  
Vol 37 (5) ◽  
pp. 2149-2158 ◽  
Author(s):  
Aénor Pons ◽  
Emilie Béchade ◽  
Jenny Jouin ◽  
Maggy Colas ◽  
Pierre-Marie Geffroy ◽  
...  
Keyword(s):  
Water Pressure ◽  
High Water ◽  
Structural Modifications ◽  
Lanthanum Silicate ◽  
High Water Pressure

Heat Exchange Calculation of a Regenerative Air Heater with Numerical Simulation Method

2013 ◽  
Vol 860-863 ◽  
pp. 1416-1419
Author(s):  
Ri Guang Wei ◽  
Zhen Xiao Qu ◽  
Jian Qiang Gao
Keyword(s):  
Numerical Simulation ◽  
Simulation Method ◽  
Calculation Model ◽  
Design Parameters ◽  
Practical Calculation ◽  
Air Preheater ◽  
Air Heater ◽  
Pulverized Coal Boiler ◽  
Set Up ◽  
Coal Boiler

According to the structure and working principle of rotary air preheater,the heat transfer calculation model is set up with reasonable simplification. Combining with the design parameters of the rotary air preheater of a 400 t/h pulverized coal boiler unit ,the results of practical calculation show that the said thermodynamic calculation method not only has higher precision of calculation,but also can get the temperature distributions of the gas, air and heat surface in each cross-section of the rotary air preheater. The result of numerical simulation calculation tallies well with the original designed data. It can be used for the heat calculation both two-sectorial and three-sectorial air heater; it can be used for performance analysis of the regenerative air heater.

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