scholarly journals Force and Deformation Characteristics during the Reconstruction and Expansion of Shallow Single-Tube Tunnels into Large-Span Multiarch Tunnels

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Yanling Jia ◽  
Yongxu Xia ◽  
Xindong Chen ◽  
Yongdi Zhou ◽  
Xingbo Han ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Numerical Simulation ◽  
Great Influence ◽  
Surrounding Rock ◽  
Surface Subsidence ◽  
Stress And Strain ◽  
Partition Wall ◽  
Single Tube ◽  
Left And Right ◽  
The Right

At present, there are an ever-increasing number of tunnel expansion projects in China. Studying the mechanical properties of the expanded tunnels is of great significance for guiding their safe construction. Through model testing and numerical simulation, the mechanical properties of a double-arch tunnel constructed through the expansion of the middle pilot heading from an existing single-tube tunnel were studied. The variation characteristics of the surface subsidence, surrounding rock stress, and stress and strain of the middle partition wall and lining during the tunnel reconstruction and expansion were investigated. The mechanism for transferring stress and strain between the left and right tunnel tubes was studied by a numerical simulation method. The results showed that the surface subsidence caused by the excavation of the left (i.e., the subsequent) tunnel tube was larger, and the maximum surface subsidence occurred at the right (i.e., the first) tunnel tube. The surrounding rock on the middle wall was the sensitive part of the tunnel excavation, the stress of the surrounding rock at the left spandrel of the right tunnel tube fluctuated and exhibited the most complex variation, and the stress of the surrounding rock at the right spandrel of the left tunnel tube exhibited the largest variation. The excavation of the left tunnel tube had a great influence on the forces of the middle partition wall and the lining structure of the right tunnel tube, the middle partition wall was subjected to eccentric compression towards the left tunnel tube, and the stress at the left spandrel under the initial support of the right tunnel tube exhibited complex variations. The excavation of the left and right tunnel tubes had a great influence on the stability of the surrounding rock, as well as on the force-induced deformation of the middle partition wall and the support structure, within the width of the single tunnel tube span behind the tunnel working face. Due to the different construction sequences, the stress and strain at the symmetric measurement points of the middle partition wall, as well as the left and right tunnel support structures, were very different.

scholarly journals Study on the Effect of Heat-Input on the Thickness of the Heat-Affected Zone of the SUS316L Steel Welded Joint by Numerical Simulation

2021 ◽  
Vol 31 (5) ◽  
pp. 68-74
Keyword(s):  
Numerical Simulation ◽  
Heat Affected Zone ◽  
Heat Input ◽  
Welded Joint ◽  
Plate Thickness ◽  
Great Influence ◽  
Thickness Direction ◽  
Welding Joint ◽  
Simulation Results ◽  
The Right

The thickness of the heat-affected zone (HAZ) has a great influence on the strength of the welded joint, so one of the important tasks is to control the HAZ to a small enough level, through using the suitable heat-input (qd). In this study, the authors use SYSWELD software to compute and build a relationship between the heat-input and the thickness of the heat-affected zone in the plate thickness direction to find the right heat-input for researched welding joint. The simulation results show that when welding the root pass with qd > 552 J/mm and the cap pass with 754 J/mm < qd < 1066 J/mm, the thickness of HAZ were increased with a function almost linearly.

scholarly journals Analysis of suspension bridge tunnel-type anchorage construction on the stability of surrounding rock

2020 ◽  
Vol 198 ◽  
pp. 02006
Author(s):  
Nana Li ◽  
Yongqiang Zhou ◽  
Yanqiang Zhao ◽  
Guiju Li
Keyword(s):  
Suspension Bridge ◽  
Surrounding Rock ◽  
Construction Process ◽  
Analysis Model ◽  
Stability Of Surrounding Rock ◽  
Numerical Software ◽  
Left And Right ◽  
Simulation Results ◽  
The Stability ◽  
The Right

In order to study the interaction between the left and right tunnels of suspension bridge tunnel-type anchorage, the finite difference numerical software is used to analyze the mechanical properties of the surrounding rock during the construction process. A numerical analysis model based on FLAC3D is established to analyze the stress, displacement and plastic zone changes of the surrounding rock of right tunnel anchor cavern during the construction of left tunnel anchor cavern. The right tunnel anchor cavern is excavated firstly, and then the left tunnel anchor cavern is excavated. The numerical simulation results show that the main displacement of the right tunnel occurs in the construction stage of the anchor plug body and the rear anchor cavern of the left tunnel. During the excavation of the left tunnel, the plastic zones of the left and right tunnel anchor caverns are only connected above the middle of the waist wall. Therefore, it is suggested that during the construction process, especially in the excavation stage of the anchor plug body and the rear anchor cavern, the area above the middle of the tunnel waist wall should be strengthened in time to ensure the construction safety.

scholarly journals Mechanical Properties and Application of Right-Hand Rolling-Thread Steel Bolt in Deep and High-Stress Roadway

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 346 ◽  
Author(s):  
Jinpeng Zhang ◽  
Limin Liu ◽  
Jun Shao ◽  
Qinghai Li
Keyword(s):  
Mechanical Properties ◽  
High Stress ◽  
Surrounding Rock ◽  
Left Hand ◽  
Pull Out ◽  
Right Hand ◽  
Section Area ◽  
Surrounding Rock Control ◽  
The Right ◽  
Steel Bolts

The left-hand rolling-thread steel bolt has been proposed as a new bolt for controlling roadway surrounding rock. To explore the mechanism of a left-hand rolling-thread steel bolt in roadway surrounding rock control, its pretightening forces, tensile strengths, anchoring forces, and maximum working resistances were compared to normal right-hand full-thread steel bolts in the engineering context of the 1301 haulage roadway in the Daxing Coal Mine. Then, the left-hand threaded steel bolt was applied to the 1301 haulage roadway that the right-hand threaded steel bolt failed to control. The results indicated that due to the different effective tensile section area, the yield strength and tensile strength of the left-hand threaded steel bolt with the same material and diameter were more than 10% larger than those of the right-hand threaded steel bolt. Due to the different thread directions, the anchoring forces of the Φ18 and Φ20 left-hand threaded steel bolts were 46.2% and 33.3% greater than those of the right-hand threaded steel bolts, respectively. In the 1301 haulage roadway, the maximum pull-out force of the left-hand rolling-thread steel bolt with the same diameter was obviously greater than that of the right-hand full thread steel bolt. The displacements of the 1301 haulage roadway supported by the left-hand threaded steel bolt were not great. So, the left-hand threaded steel bolt can effectively control the surrounding rock in the 1301 haulage roadway.

ACSR Strands Stress Numerical Simulation

2012 ◽  
Vol 256-259 ◽  
pp. 710-713
Author(s):  
Li Qin ◽  
Jun Kuo Li ◽  
Qiang Fu
Keyword(s):  
Mechanical Properties ◽  
Numerical Simulation ◽  
Finite Element Method ◽  
Finite Element ◽  
Principal Part ◽  
Concentration Level ◽  
Structural Characteristics ◽  
Stress And Strain ◽  
Electricity Power ◽  
Distribution Of Stress

As an important carrier of electricity power, ACSR is a principal part of power system and is directly related to the transmission line reliability and safety. ACSR strands stress analysis is the foundation of studying ACSR mechanical properties. In this paper, finite element method is used to analysis the Acsr strands stress. The structural characteristics of Acsr is considered and the complete Acsr model is created by ansys to simulate the distribution of stress and strain under appropriate boundary conditions. The Conclusions are drawn that both the state of strands stress and the stress concentration level are related with its structural properties. The strands of out layers bears more stress and firstly comes into plastic strain. The results of the research is helpful to the further study of ACSR strength and conductor fatigue life.

scholarly journals Micro Fracture Behavior of Composite Honeycomb Sandwich Structure

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 135
Author(s):  
Guangjian Bi ◽  
Jianping Yin ◽  
Zhijun Wang ◽  
Zijian Jia
Keyword(s):  
Mechanical Properties ◽  
Numerical Simulation ◽  
Fracture Energy ◽  
Energy Absorption ◽  
Sandwich Structure ◽  
Great Influence ◽  
Energy Curve ◽  
Energy Calculation ◽  
Honeycomb Sandwich ◽  
Honeycomb Sandwich Structure

To study the influence of structure size and composite forms on the mechanical properties of the composite double honeycomb sandwich structure, a composite double honeycomb sandwich structure was initially designed. The dynamic response of a composite double-layer honeycomb sandwich structure under high-speed impact was studied through theoretical analysis and numerical simulation. Ls-dyna software was used to simulate the initially designed composite structure. According to the numerical simulation results and the proposed method for calculating the fracture energy of the composite double honeycomb sandwich structure, the effects of different composite forms on the mechanical properties were analyzed. The results show that the proposed fracture energy calculation method can effectively describe the variation trend of the honeycomb structure and the micro-element fracture situation in the valid time. The fracture energy curve has a high sensitivity to cell density and material, and the strength of the top core has a great influence on the overall energy absorption. Compared with the traditional honeycomb protection structure, the energy absorption of the initially designed composite honeycomb sandwich structure was improved effectively.

scholarly journals Mechanical state analysis of different variants of piled rafts

2015 ◽  
Vol 10 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Michail Samofalov ◽  
Vytautas Papinigis ◽  
Mantas Tūnaitis
Keyword(s):  
Mechanical Properties ◽  
Numerical Simulation ◽  
Strain State ◽  
Design Methods ◽  
Current Paper ◽  
Stress And Strain ◽  
Bending Moments ◽  
Mechanical State ◽  
Piled Raft ◽  
Rational Case

Traditional raft design methods describe unpiled and fully piled rafts. The current paper aims to discuss intermediate raft design variants when the raft is at the same time partially supported by piles and partially rests on the ground. The loading conditions of all variants as well as mechanical properties assumed to be identical, general numerical simulation assumptions are also the same. The task is to analyse the stress and strain state of the raft for all variants (unpiled raft, partially piled raft, fully piled raft), to compare the results and to determine the most rational case. Raft settlements, bending moments and expenses of the materials are compared on the basis of the results.

Biaxial mechanical properties of the pericardium in normal and volume overload dogs

1985 ◽  
Vol 249 (2) ◽  
pp. H222-H230 ◽  
Author(s):  
M. C. Lee ◽  
M. M. LeWinter ◽  
G. Freeman ◽  
R. Shabetai ◽  
Y. C. Fung
Keyword(s):  
Mechanical Properties ◽  
Volume Overload ◽  
Physiological Saline ◽  
Aortocaval Shunt ◽  
Tension Level ◽  
Left And Right ◽  
The Right ◽  
Biaxial Mechanical Properties ◽  
Cardiac Dilatation

The two-dimensional mechanical properties of the pericardium from dogs with a normal or chronically enlarged heart were studied in vitro. A 3.0-cm-square piece of the pericardium overlying the right and/or left ventricle was excised. An approximately 1.0-cm-square target was marked at the center, and its dimension was measured electrooptically. When immersed in physiological saline at 37 degrees C, the specimen was stretched and unloaded sinusoidally in one direction while force in the transverse direction was held constant. The tension-stretch relationship was highly reproducible and was insensitive to strain rate in the range of 0.002-0.1 Hz. Hysteresis was present. The pericardium was mostly anisotropic; however, the direction of maximal compliance varied among dogs. The elastic properties of the pericardium overlying the left and right ventricles were the same in most cases. Substantial stress relaxation was observed; in contrast, insignificant creep developed over 30 min. In five dogs with chronic cardiac dilatation due to an infrarenal aortocaval shunt, the tension-stretch curves were shifted significantly to the right (i.e., greater deformation at the same tension level). However, the pericardial viscoelastic properties and thickness were unchanged. In other words, chronic cardiac dilatation resulted in a more compliant pericardium.

scholarly journals Study of the stability of tunnel construction based on double-heading advance construction method

2020 ◽  
Vol 12 (1) ◽  
pp. 168781401989696 ◽  
Author(s):  
Zhanping Song ◽  
Guilin Shi ◽  
Baoyun Zhao ◽  
Keming Zhao ◽  
Junbao Wang
Keyword(s):  
Numerical Simulation ◽  
Construction Method ◽  
Field Monitoring ◽  
Surrounding Rock ◽  
Tunnel Construction ◽  
Successful Implementation ◽  
Simulation Results ◽  
The Stability ◽  
Sand Stratum ◽  
The Right

The deformation and significant settlement of surrounding rock often occur during tunnel construction with the condition of abundant water and weak cementing sand. In order to study the construction method and stability under such soft stratum, this article takes Taoshuping tunnel as the engineering background and puts forward a new tunnel construction method—double-heading advance construction method by comparing the advantages and disadvantages of various traditional construction schemes. The numerical simulation of tunnel construction process using this method is carried out to illustrate the rationality and feasibility of the method. The conclusions are drawn by comparing the numerical simulation results with the field monitoring data analysis. The numerical simulation results show that the maximum settlement value caused by excavation construction is in the parts 5 and 6 of the upper half-section and the part 7 of the central section. The settlement values of parts 5, 6, and 7 accounted for 32.4%, 24.3%, and 18.9% of the total settlement values, respectively. So, the supporting measures for double-heading advance excavation construction of these three parts should be strengthened properly. The stress of the right hance changes greatly before and after the demolition of temporary support. The maximum positive value of stress is 23 kPa and the maximum negative value of stress is −32 kPa. Therefore, the length of temporary bracing should be strictly controlled during construction and the monitoring of the right hance area should be strengthened. Furthermore, it is necessary to strengthen the supporting measures and monitoring in the right spandrel area as the surrounding rock pressure in the right spandrel area is higher than the left spandrel area. The optimum excavation height of the upper half-section in Taoshuping tunnel is determined to be 5.4 m and the reasonable excavation distance between parts 1 and 5 is determined to be 25–30 m by parameter optimization. Finally, the variation law of numerical simulation and field monitoring results is consistent, which shows that the double-heading advance construction method has a better effect on the stability control of surrounding rock, and the rationality and feasibility of this method are validated effectively. Therefore, the double-heading advance method is suitable for tunnel construction in the sand stratum with rich water and weak cementation, and the successful implementation of this method in Taoshuping tunnel also provides a reference for subsequent tunnel construction in the sand stratum with rich water and weak cementation.

scholarly journals Complex Function Solution for Deformation and Failure Mechanism of Inclined Coal Seam Roadway

2021 ◽  
Author(s):  
Xianyu Xiong ◽  
Jun Dai ◽  
Xinnian chen ◽  
Yibo Ouyang
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Failure Mechanism ◽  
Physical Simulation ◽  
Complex Function ◽  
Surrounding Rock ◽  
Simulation Test ◽  
Deformation And Failure ◽  
Stress And Deformation ◽  
The Right

Abstract The stressed environment of the inclined coal seam roadway is complex and changeable, and the damage degree of surrounding rock increases, threatening the safe mining of coal mines. To improve the effectiveness of stability control of surrounding rock of this kind of roadway, the deformation and failure law of the inclined coal seam roadway is analyzed based on the complex function theory. It optimizes the solution process and accuracy of the mapping function coefficient and deduces the analytical solution of surrounding rock stress and deformation inclined coal seam roadway. The deformation and failure mechanism of surrounding rock in inclined coal seam roadway is revealed theoretically and verified by numerical simulation and physical simulation test. The results show that the stress and deformation of roadway surrounding rock in inclined coal seam show obvious asymmetric distribution characteristics. The stress and deformation of roadway surrounding rock on the right side are greater than on the left side. The two sides of the roadway, the right side of the roof and the roof angle of the right side, are the key positions of roadway stress concentration and deformation. According to the variation law of stress and deformation distribution of roadway surrounding rock, roadway cyclic deformation and failure theory is put forward. The numerical simulation and physical simulation test show that the deformation and failure law of roadway is consistent with the theoretical analysis results, and the cyclic deformation and failure mechanism of roadway in inclined coal seam is verified.

scholarly journals Experimental Research on the Mechanical Properties of Tailing Microcrystalline Foam Glass

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2048 ◽  
Author(s):  
Jinliang Bian ◽  
Wanlin Cao ◽  
Lin Yang ◽  
Cunqiang Xiong
Keyword(s):  
Mechanical Properties ◽  
Modulus Of Elasticity ◽  
Foam Glass ◽  
Experimental Studies ◽  
Great Influence ◽  
Future Research ◽  
Stress And Strain ◽  
Light Weight ◽  
Foaming Agent ◽  
Strength Tests

Tailing microcrystalline foam glass (TMFG) is a building material that not only has the characteristics of light weight, fire resistance, and thermal insulation, but also has decorative applications. TMFG has a broad application prospect, but there has been little research on the macroscale mechanical properties of this material. In order to analyze TMFG basic mechanical properties, a series of experimental studies were carried out by performing the four-point flexural, shear, uniaxial compression, and splitting tensile strength tests. The research showed that the foaming agent (SiC) had a great influence on the mechanical properties of the material. With the reduction of the amount of SiC, the strength of the material and brittle failure increased. The microcrystalline decoration surface improved the flexural strength and compression strength of the tailing microcrystalline foam glass. The modulus of elasticity and the Poisson’s ratio are discussed, and a formula for the modulus of elasticity is proposed. Based on the analysis of the stress and strain curves, a constitutive model is proposed for the application of tailing microcrystalline foam glass and future research on this material.

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