Han Wang

Bio: Han Wang is an academic researcher from University of Science and Technology, Liaoning. The author has contributed to research in topics: Bedding & Ultimate tensile strength. The author has an hindex of 1, co-authored 2 publications receiving 4 citations.

Effect of bedding angle on tunnel slate failure behavior under indirect tension

Abstract: In order to provide guidance for Muzhailin tunnel design and construction, in this study, five groups of slate specimens with different bedding angles (β, angle between bedding plane and vertical a...

Characterization of Heterogeneous Microstructure and Mechanical Properties of Q345R Welded Joints Including Roles of the Welding Process

Abstract: In this paper, the roles of the welding process on the heterogeneous microstructure and mechanical properties of Q345R welded joints were analyzed by a series of tests, including the preparation of welded joints with different welding processes, optical microscope observation, uniaxial tensile tests, and hardness and impact measurements. The experimental results show that with the increase in welding heat input, the content of pre-eutectoid ferrite and the size of the Weidner structure increased, while the hardness and the impact absorption energy of the weld zone decreased gradually. With the increase in heat input, the volume proportion of eutectoid ferrite in the weld increased from 9.90% to 18.78%; the volume proportion of acicular ferrite decreased from 85.10% to 76.21%. With the decrease in heat input, the volume proportion of eutectoid ferrite decreased from 10.58% to 1.45%, and the volume proportion of acicular ferrite increased from 84.21% to 92.74%. Under the influence of the second welding heat, the first weld zone, the fusion zone and part of the heat-affected zone were re-austenitizing, and the distribution of ferrite and pearlite was more uniform. The hardness value of the former weld was lower than that of the second weld, and the distribution was more uniform. The maximum hardness value of the second weld zone and its corresponding heat-affected zone increased with the increase in depth. The distribution of the yield strength and the tensile strength of welded joints was similar to that of hardness.

Bedding Effect of Carbonaceous Slate Failure Behavior at Direct Shear Tests

Abstract: In this study, the carbonaceous slate of Muzhailing tunnel was selected to explore the deformation and failure mechanism of tunnel layered slate under direct shear conditions. Five sets of direct shear tests were carried out on slate with different bedding dip angles (β: 0°, 30°, 45°, 60°, and 90°). The strength parameters, failure mode, fracture topography, dissipated energy, and acoustic emission (AE) characteristics were analyzed in detail to study the bedding effect of slate failure. The results show that the cohesion and internal friction angle of slate increases and decreases linearly with β from 0° to 90°, respectively, and the shear strength of bedding plane is lower than that of matrix. Additionally, the relative roughness (δ) of gray-scale image was defined, and the linear relationship between δ and root-mean-square height (Sq) was established to improve the efficiency of evolution of fracture topography. Furthermore, the shear energy consumption per unit area (us) was calculated, less sensitive to the variation of β. Moreover, a larger AE count and energy release rate were observed when the shear stress decreased, and a relative quiet period was observed before the peak loading. Additionally, both the count and energy release rate linearly decreased with the increase in β, and the proportion of tensile microcracks for vertical bedding is slightly higher than that for horizontal bedding. The main frequency of vertical bedding slate is smaller than that of horizontal bedding, i.e., the size of microcracks of slate with β of 90° is relatively larger. Generally, the frequency bandwidth of slate became narrower when β was varied from 30° to 60°, and the main frequency increased, indicating that the degree of shear failure of matrix is weakened. In contrast, the degree of cracking along the bedding plane increased.

Performance of a deep excavation in Lanzhou strong permeable sandy gravel strata

Abstract: A large air shaft engineered between the Olympic Sports Center Station and Century Avenue Station of the Lanzhou Metro Line one, China, occurred in strong permeable sandy gravel complex strata. The short distance between the Yellow River and the pit (shaft) resulted in many challenges during construction. These challenges mainly included the quick recovery of the water level and the difficulty of plugging the water. Some measures for monitoring the structural safety and response of the surrounding environment were taken. As the data showed, the design combined a bottom-up method with a top-down method using a peripheral cut-off wall for anti-seepage treatment, the underground diaphragm wall and the concrete bracing had a large rigidity, good impermeability and little influence on the surrounding environment in the process of dewatering and excavation, the external plastic concrete cut-off wall could contribute to the groundwater drawdown inside the pit and reduce the soil pressure on the retaining structure of the pit.

Thermal Conductivity Characteristics of Thermal Insulation Materials Immersed in Water for Cold-Region Tunnels

Abstract: This study investigates the distribution of pore water on the basis of the measured mass moisture content after soaking the tunnel insulation material. This study also analyzes the influence of the distribution of pore water on the thermal conductivity of the material on the basis of this mass moisture content. Scanning images of phenolic and polyurethane insulation boards are obtained by computer tomography (CT). The gray volume moisture content (Gv) is deduced based on the CT scanning images, to determine the distribution of pore water (Gv is the ratio of the volume of the water sample (represented by the gray value) to the volume of the saturated water sample (represented by the gray value) which is the gray volume moisture content of the sample). The correlation between gray volume moisture content and mass moisture content is determined by comparing different algorithms of gray volume moisture content and volume moisture content. The relationship between mass moisture content and thermal conductivity can be determined using a self-made quasi-steady-state tester, whereas the relationship between gray volume moisture content and thermal conductivity can be derived indirectly. Related experimental research can predict the thermal conductivity of thermal insulation materials by using a new perspective and shows the influence of pore water distribution on the thermal conductivity of materials.

Bedding Plane Effects on Mechanical Behavior of Surrounding Rock in Mountain Tunneling

Abstract: The layered rock showed the characteristics in Mountain tunnel, Yunnan. A series of uniaxial compression tests and variable angle shear tests were carried out, and the aim was to investigate the effect of the bedding on its mechanical parameters and failure modes. The test results show that the uniaxial compressive strength, elastic modulus, and Poisson's ratio of layered rock present a U-shaped distribution with the increase in bedding orientation from 0° to 90°. All of them have a maximum when the bedding orientation is 0° and a minimum when the bedding orientation is 45°. The failure modes of layered rock can be summarized into three types: the fracture tensile failure parallel to the weak plane of bedding; the shear slip failure along bedding weak plane; and tension-shear composite failure between bedding weak plane and matrix. Based on the testing data and analysis results, it can be concluded that the layered rock specimen with different bedding orientations is an important reason for the anisotropy of mechanical parameters and failure modes.