B. Alipenhani; A. Majdi; H. Bakhshandeh Amnieh
Abstract
Determining the hydraulic radius of the undercut in the block caving method is one of the key issues in this method. The hydraulic radius is directly related to the minimum caving span. In this research work, the rock mass cavability is investigated using the UDEC and 3DEC software. Since the factors ...
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Determining the hydraulic radius of the undercut in the block caving method is one of the key issues in this method. The hydraulic radius is directly related to the minimum caving span. In this research work, the rock mass cavability is investigated using the UDEC and 3DEC software. Since the factors affecting the cavability are very diverse and numerous, firstly, by 2D modeling in the UDEC software and examining the trend of changes in the minimum caving span, the most important factors including the depth, dip of the joint, number of joints, angle of friction of the joint surface, and joints spacing are selected for the final study. The variation trend of each variable is investigated by keeping the other variables constant (single-factor study) among various factors. In the second step, the minimum caving span for the five main factors and values is determined in the single-factor study using the SPSS software and the multivariate regression method. Then the power function of the minimum caving span is chosen based on the selected variables with a coefficient of determination of 0.76. In continuation, a simple 3D model is built from the undercut. A linear equation is achieved between the results of the 3D and 2D modeling results in similar conditions. In a model with certain conditions, using the equation obtained from the numerical method, the calculated hydraulic radius of caving is 22.5 m, which is close to the result obtained from the Laubscher's empirical method with the same condition (24 m).
Gh.H. Ranjbar; K. Shahriar; K. Ahangari
Abstract
Although segmental tunnel linings are often used for seismic areas, the influence of segment joints on the segmental lining behavior under seismic loading has not been thoroughly considered in the literature. This paper presents the results of a numerical study investigating the effects of the rotational, ...
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Although segmental tunnel linings are often used for seismic areas, the influence of segment joints on the segmental lining behavior under seismic loading has not been thoroughly considered in the literature. This paper presents the results of a numerical study investigating the effects of the rotational, axial, and radial joint stiffness of the longitudinal joints on the structural forces in segmental tunnel lining under seismic loading. A 3D finite element method is adapted to establish elaborate numerical models of the segments. The validity of the numerical model was tested by comparing the results obtained with the well-known analytical methods presented by Wang and Penzien. The results demonstrate that by increasing the rotational stiffness of the segmental joint, the bending moment increases. When the rotational stiffness ratio is less than 0.5, the positive and negative bending moment variations are more. The numerical modeling results show the variations in the bending moment and the difference between the positive and negative bending moment values increased by increasing the acceleration of seismic loading. Moreover, it is significant for the values. By increasing the rotational stiffness ratio of the segmental joint, the axial force ratio decreases. By increasing the axial and shear stiffness ratio of segmental joint, the variations in the bending moment and axial force in segmental lining is not significant and is ignorable in designing segmental lining.
