scholarly journals Numerical Study on Thermal Damage Behavior and Heat Insulation Protection in a High-Temperature Tunnel

2021 ◽  
Vol 11 (15) ◽  
pp. 7010
Author(s):  
Fangchao Kang ◽  
Yingchun Li ◽  
Chun’an Tang ◽  
Tianjiao Li ◽  
Kaikai Wang
Keyword(s):  
High Temperature ◽  
Thermal Insulation ◽  
Thermal Damage ◽  
Cold Shock ◽  
Numerical Study ◽  
Coupling Model ◽  
Tunnel Support ◽  
Mechanical Coupling ◽  
Thermal Cracks ◽  
Rock Temperature

Deepening our understanding of temperature and stress evolution in high-temperature tunnels is indispensable for tunnel support and associated disaster prevention as the rock temperature is remarkably high in hot dry rock (HDR) utilization and similar tunnel engineering. In this paper, we established a two-dimensional thermal–mechanical coupling model through RFPA2D-thermal, by which the temperature and stress field of the surrounding rock in a high-temperature tunnel with and without thermal insulation layer (TIL) were studied, followed by the evolution of thermal cracks. The associated sensitivity analysis of the TIL and airflow factors were then carried out. We found that (1) the tunnel rock is unevenly cooled down by the cold airflow, which induces thermal stress and damages the rock element when it exceeds the tensile strength of the rock mass. Those damaged rock elements accumulate and coalesce into visible cracks in the tunnel rock as the ventilation time goes, reducing the tunnel stability. (2) TIL effectively reduces the heat exchange between the airflow and tunnel rock and weakens the cold shock by the airflow, delaying the crack initiation which provides efficient time to adopt engineering measures for tunnel supporting. (3) TIL parameters are of pivotal importance to the long-term cold shock by the airflow. Increasing the TIL thickness and reducing the TIL thermal conductivity both significantly enhance the thermal insulation effect. The results cover the gap in the study of cold shock in high-temperature tunnels, which is helpful in designs to prevent thermal damage in high-temperature tunnels.

scholarly journals Numerical Study on Damage Zones Induced by Excavation and Ventilation in a High-Temperature Tunnel at Depth

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4773
Author(s):  
Jianyu Li ◽  
Hong Li ◽  
Zheming Zhu ◽  
Ye Tao ◽  
Chun’an Tang
Keyword(s):  
High Temperature ◽  
Lateral Pressure ◽  
Numerical Study ◽  
Pressure Coefficient ◽  
Fracture Morphology ◽  
In Situ Stress ◽  
Surrounding Rock ◽  
Geothermal System ◽  
Mechanical Coupling ◽  
Lateral Pressure Coefficient

Geothermal power is being regarded as depending on techniques derived from hydrocarbon production in worldwide current strategy. However, it has artificially been developed far less than its natural potentials due to technical restrictions. This paper introduces the Enhanced Geothermal System based on Excavation (EGS-E), which is an innovative scheme of geothermal energy extraction. Then, based on cohesion-weakening-friction-strengthening model (CWFS) and literature investigation of granite test at high temperature, the initiation, propagation of excavation damaged zones (EDZs) under unloading and the EDZs scale in EGS-E closed to hydrostatic pressure state is studied. Finally, we have a discussion about the further evolution of surrounding rock stress and EDZs during ventilation is studied by thermal-mechanical coupling. The results show that the influence of high temperature damage on the mechanical parameters of granite should be considered; Lateral pressure coefficient affects the fracture morphology and scale of tunnel surrounding rock, and EDZs area is larger when the lateral pressure coefficient is 1.0 or 1.2; Ventilation of high temperature and high in-situ stress tunnel have a significant effect on the EDZs scale; Additional tensile stress is generated in the shallow of tunnel surrounding rock, and the compressive stress concentration transfers to the deep. EDZs experiences three expansion stages of slow, rapid and deceleration with cooling time, and the thermal insulation layer prolongs the slow growth stage.

Numerical Study on Bending Behavior of Copper Alloy Thin Plate by Single Pulse Laser

2014 ◽  
Vol 1003 ◽  
pp. 113-116
Author(s):  
Su Qin Jiang ◽  
Ai Hui Liu ◽  
Xue Ting Wang ◽  
Jian Hua Wu ◽  
Bo Kui Li
Keyword(s):  
Thin Plate ◽  
Pulse Laser ◽  
Copper Alloy ◽  
Numerical Study ◽  
Dynamic Change ◽  
Single Pulse ◽  
Coupling Model ◽  
Laser Forming ◽  
Bottom Surface ◽  
Mechanical Coupling

To study the bending characteristics of copper alloy thin plate by single pulse laser, the thermal mechanical coupling model of pulsed laser forming (PLF) was established; the dynamic change and steady distribution for the fields of temperature, stress& strain and displacement were analyzed. The results show n that during the pulse laser heating stage, the temperature gradient along the thickness direction is far less than that of the heat affected zone; due to the constraints of materials around the heating field, the compressive stress and negative strain are appeared, the cantilever end of sample produces warping deformations; in the cooling stage, the temperature of top and bottom surface material drops rapidly, the sample is with a negative bending and reduced deformation. This is related to the transferring of the stress change and the recovery of part of the elastic deformation in heating area.

scholarly journals Destruction Law of Borehole Surrounding Rock of Granite under Thermo-Hydro-Mechanical Coupling

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Jinwen Wu ◽  
Zijun Feng ◽  
Shuping Chen ◽  
Wenmei Han
Keyword(s):  
High Temperature ◽  
Fracture Morphology ◽  
Surrounding Rock ◽  
Borehole Stability ◽  
Thermally Induced ◽  
Mechanical Coupling ◽  
Thermal Cracks ◽  
Fracture Development ◽  
Initial Fracture ◽  
High Temperature Steam

The destruction of the rock that surrounds boreholes under thermo-hydro-mechanical coupling is an important factor for borehole stability in hot dry rock (HDR) geothermal energy extraction. Failure experiments for granite under triaxial stress ( σ 1 > σ 2 > σ 3 ) were conducted as 500°C superheated steam was transported through the borehole. High-temperature steam leads to large thermal cracks in the surrounding rock, which are randomly distributed around the borehole and gradually expand outwards. The randomly distributed thermally induced microcracks increase the complexity of the initial fracture morphology around the borehole and contribute to the appearance of multiple branch fractures. Fracture development is negligibly affected by ground stresses during the initial stages. However, fractures are deflected towards the maximum horizontal principal stress under ground stresses during later periods. During fracture propagation, high-temperature steam more easily penetrates the rock because its viscosity is lower than water. Towards the end of the crack expansion, the steam loses heat and liquefies, which increases the elongation resistance, and results in the arrest and intermittent expansion of the cracks.

scholarly journals Simulation and experimental study of a new structural rubber seal for the roller-cone bit under high temperature

2020 ◽  
Vol 12 (12) ◽  
pp. 168781402098562
Author(s):  
Lin Chen ◽  
Wei Lin ◽  
Yiwei Han ◽  
Zhijiu Ai ◽  
Yuchun Kuang ◽  
...  
Keyword(s):  
High Temperature ◽  
Service Life ◽  
Structural Parameters ◽  
Coupling Model ◽  
Optimization Method ◽  
Butadiene Rubber ◽  
Three Dimension ◽  
Mechanical Coupling ◽  
Sealing Performance ◽  
Ring Seal

Seal element is an important component of roller-cone bit. In order to improve the sealing performance and service life of roller-cone bit under high temperature, a new seal structure with multi-segment arcs is designed and the structural parameters of this sealing ring are optimized by response surface method and finite element method. Firstly, the hydrogenated nitrile-butadiene rubber is used to improve the seal performance under high temperature, and the uniaxial, planar, and biaxial tensile experiments are carried out to study the constitutive model of this rubber. Then, a three-dimension transient thermo-mechanical coupling model is established. The comparison of sealing performance between the new structural seal and the traditional O-ring seal is implemented under high temperature through the proposed FEM and laboratory experiments. The results show that the new structural seal has lower contact pressure and Mises stress than the standard O-ring seal, and the service life of the former is almost twice of the later one. Additionally, a composite drill bit using the new structural seal is applied to a deep drilling. After servicing a certain time, it shows that the wearing capacity is very small. The results show that the new structure seal ring can adapt to high temperature environment and the optimization method is feasible.

Damage Analysis of Thermal-Mechanical Coupling on Concrete Member under High Temperature

2013 ◽  
Vol 639-640 ◽  
pp. 1187-1192
Author(s):  
Shui Ping Yin ◽  
Song Hua Tang ◽  
Yong Hong Li ◽  
Chao Chen ◽  
Fang Tian ◽  
...  
Keyword(s):  
High Temperature ◽  
Structural Damage ◽  
Damage Mechanics ◽  
Thermal Damage ◽  
Damage Model ◽  
Damage Analysis ◽  
Concrete Member ◽  
Cumulative Impact ◽  
Mechanical Coupling ◽  
Structural Resistance

The fire has brought great harm to human, so it is of vital significance to establish a scientific method of structural fire resistance design to avoid personnel casualties and economic loss in the destroy or collapse of the structure in fire. The mechanical properties of materials deteriorate at the high temperature of the fire, and the structure can be damaged easily, so the damage cumulative impact must be considered in the structural resistance capability to fire. Damage mechanics is a powerful tool in the study of structural damage and destroy. In the paper, the damage mechanics is introduced into the calculation of resistance capability to fire of concrete structure, and the thermal-damage analysis of concrete member is achieved through the second development on ANSYS platform by using the residual strength thermal-damage model at high temperature.

scholarly journals Evolution regularity of temperature field of active heat insulation roadway considering thermal insulation spraying and grouting: A case study of Zhujidong Coal Mine, China

2021 ◽  
Vol 40 (1) ◽  
pp. 151-170
Author(s):  
Weijing Yao ◽  
Happiness Lyimo ◽  
Jianyong Pang
Keyword(s):  
Sensitivity Analysis ◽  
Temperature Field ◽  
Thermal Insulation ◽  
Wall Temperature ◽  
Heat Insulation ◽  
Surrounding Rock ◽  
Rock Temperature ◽  
Grouting Materials ◽  
Zone Radius ◽  
Thermal Conductivities

Abstract To study the active heat insulation roadways of high-temperature mines considering thermal insulation and injection, a high-temperature −965 m return air roadway of Zhujidong Coal Mine (Anhui Province, China) is selected as a prototype. The ANSYS numerical simulation method is used for the sensitivity analysis of heat insulation grouting layers with different thermal conductivities and zone ranges and heat insulation spray layers with different thermal conductivities and thicknesses; thus, their effects on the heat-adjusting zone radius, surrounding rock temperature field, and wall temperature are studied. The results show that the tunneling head temperature of the Zhujidong Mine is >27°C all year round, consequently causing serious heat damage. The heat insulation circle formed by thermal insulation spraying and grouting can effectively alleviate the disturbance of roadway airflow to the surrounding rock temperature field, thereby significantly reducing the heat-adjusting zone radius and wall temperature. The decrease in the thermal conductivities of the grouting and spray layers, expansion of the grouting layer zone, and increase in the spray layer thickness help effectively reduce the heat-adjusting zone radius and wall temperature. This trend decreases significantly with the ventilation time. A sensitivity analysis shows that the use of spraying and grouting materials of low thermal conductivity for thermal insulation is a primary factor in determining the temperature field distribution, while the range of the grouting layer zone and the spray layer thickness are secondary factors. The influence of the increased surrounding rock radial depth and ventilation time is negligible. Thus, the application of thermal insulation spraying and grouting is essential for the thermal environment control of mine roadways. Furthermore, the research and development of new spraying and grouting materials with good thermal insulation capabilities should be considered.

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