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RISS 인기검색어
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- 저자 : Lianheng Zhao (검색결과 5 건)
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Stability analysis of homogeneous slopes with benches
Zhao, Lianheng,Xia, Peng,Xie, Rongfu,Li, Liang,Zhang, Yingbin,Cheng, Xiao Techno-Press 2017 Geomechanics & engineering Vol.13 No.3
In this paper, with a graphical approach, a series of stability charts for homogeneous slopes with benches are presented based on the upper bound limit analysis theory and strength reduction technique. The objective function of the slope safety factor $F_s$ is optimized by the nonlinear sequential quadratic programming, and a substantial number of examples are illustrated to use the stability charts for homogeneous slopes with benches driven by only the action of the soil weight. These charts can be applied to quick and accurate estimations of the stability status of homogeneous slopes with benches. Moreover, the failure modes and the formula for safety factor Fs of homogeneous slopes with benches are provided to illustrate the stability analysis of slopes with benches, which is validated by samples.
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Dimensionless Parameter Diagrams for the Active and Passive Stability of a Shallow 3D Tunnel Face
Lianheng Zhao,DeJian Li,Feng Yang,Liang Li,Xiao Cheng 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.2
The methods for calculating the elliptical cone’s geometric parameters of multiple elliptical cone sliders were improved by introducing expression of elliptical path in 3D space. This elliptical path is the intersecting line of a cone and inclined cutting plane. Based on upper-bound limit analysis method and an improved method, Sequential Quadratic Programming (SQP) method was employed to obtain optimal upper bound solutions of failure pressure. The effectiveness of this method was verified by a comparative analysis, and a detailed parametric study on the failure pressure and failure modes was presented. In this study, the stability and failure modes of tunnel face are significantly affected by internal friction angle φ and dimensionless parameter C/D for both active and passive failure; by contrast, dimensionless parameters γD/c and σs/c have small effects. It is also found that dimensionless parameters C/D and σs /c have no effect on the results if the failure region does not reach the ground surface.
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Water Inflow Prediction and Grouting Design for Tunnel considering Nonlinear Hydraulic Conductivity
Pan Cheng,Lianheng Zhao,Qiao Li,Liang Li,Shuoyun Zhang 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.9
Grouting prevents groundwater leakage into tunnels, based on the exponent model that expresses the nonlinear variation of the hydraulic conductivity of the surrounding rock, the formulas for predicting the magnitude of water inflow and outer water pressure of the lining after grouting are deduced. The parameter analysis shows how the water inflow decreases as the hydraulic conductivity of the grouting circle diminishes and the thickness of the grouting circle increases. When the parameter α (attenuation coefficient), which expresses the decreasing amplitude of the permeability coefficient of the surrounding rock with depth, is greater than 0, the water inflow increases until it reaches a maximum at a certain depth, and then the inflow decreases to 0 if deep enough. After considering the variation in the hydraulic conductivity of the surrounding rock, the thickness and hydraulic conductivity of the grouting circle may be designed to be too large to reduce the magnitude of the water inflow. Meanwhile, to reach the limited drainage criterion of the tunnel groundwater, the grouting circle thickness decreases gradually as α increases after the nonlinear variation of the hydraulic conductivity of the surrounding rock, which can reduce the cost for plugging the groundwater. Thus, it is critical to consider hydraulic conductivity variation during water inflow predicting and grouting when designing tunnels.
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Investigation on seismic behavior of combined retaining structure with different rock shapes
Yu-liang Lin,Lianheng Zhao,T.Y. Yang,Guo-lin Yang,Xiao-bin Chen 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.73 No.5
A combination of a gravity wall and an anchor beam is widely used to support the high soil deposit on rock mass. In this study, two groups of shaking table test were performed to investigate the responses of such combined retaining structure, where the rock masses were shaped with a flat surface and a curved surface, respectively. Meanwhile, the dynamic numerical analysis was carried out for a comparison or an extensive study. The results were studied and compared between the combined retaining structures with different shaped rock masses with regard to the acceleration response, the earth pressure response, and the axial anchor force. The acceleration response is not significantly influenced by the surface shape of rock mass. The earth pressure response on the combined retaining structure with a flat rock surface is more intensive than the one with a curved rock surface. The anchor force is significantly enlarged by seismic excitation with a main earthquake-induced increment at the first intensive pulse of Wenchuan motion. The value of anchor force in the combined retaining structure with a flat rock surface is generally larger than the one with a curved rock surface. Generally, the combined retaining structure with a curved rock surface presents a better seismic performance.
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Feng Yang,Jian Zhang,Lianheng Zhao,Junsheng Yang 대한토목학회 2016 KSCE Journal of Civil Engineering Vol.20 No.6
The stability of a plane strain tunnel face in a cohesive-frictional soil (idealized as a homogeneously Mohr-Coulomb material) subjected to ground surface surcharge loading was investigated. Continuous loading is applied to the ground surface, and both smooth and rough interface conditions are modeled. The upper-bound solutions with critical load parameters for a practical range of tunnel depth-to-height values, as well as the soil properties, are obtained by using the Upper-bound Finite Element Method with Rigid Translatory Moving Elements (UBFEM-RTME). For practical use, the results are presented in the form of dimensionless stability charts. Failure mechanisms consisting of two groups of slip lines, which explicitly reflect the relative movement of blocks, are also presented. To verify the solutions, the Upper-bound Finite Element Method with Plastic Deformation Elements (UMFEMPDE) has been developed and the collapsed loads are compared with those from UBFEM-RTME. The solutions obtained with these two upper-bound finite element methods are found to be in good agreement with each other.
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