Planar sliding is one of the frequently observed types of failure in rock slopes. Kinematic analysis is a classic and widely used method to examine the potential failure modes in rock masses. The ...accuracy of planar sliding kinematic analysis is significantly influenced by the value assigned to the lateral limit angle γlim. However, the assignment of γlim is currently used generally based on an empirical criterion. This study aims to propose an approach for determining the value of γlim in deterministic and probabilistic kinematic planar sliding analysis. A new perspective is presented to reveal that γlim essentially influences the probability of forming a potential planar sliding block. The procedure to calculate this probability is introduced using the block theory method. It is found that the probability is correlated with the number of discontinuity sets presented in rock masses. Thus, different values of γlim for rock masses with different sets of discontinuities are recommended in both probabilistic and deterministic planar sliding kinematic analyses; whereas a fixed value of γlim is commonly assigned to different types of rock masses in traditional method. Finally, an engineering case was used to compare the proposed and traditional kinematic analysis methods. The error rates of the traditional method vary from 45% to 119%, while that of the proposed method ranges between 1% and 17%. Therefore, it is likely that the proposed method is superior to the traditional one.
Clay hollow brick walls are still popular in building industry, but the prediction of their sound insulation properties is not straightforward due to their inhomogeneous and anisotropic ...characteristics. In this article, a classic approach has been used to determine the sound transmission coefficient of brick walls, assuming an orthotropic behaviour and deriving the mechanical and dynamic characteristics from datasheet information. Different types of walls with horizontal and vertical mortar joints have been analysed. Experimental measurements of the sound reduction index carried out according to ISO 10140-2 standard have been performed, and the resulting values are compared with the predictions in the proposed model. It was found that the sound reduction index can be fairly predicted in the low-frequency range and it is correctly predicted in the mass law region, whereas in the high-frequency range the inner block structure is responsible for a loss of performance which is difficult to predict with the analytical methods.
In this paper, the subject of research is the AZ31B magnesium alloy. Aiming at the poor formability of magnesium alloys at room temperature, we have introduced isothermal local loading technology to ...improve the formability of magnesium alloys. We combined finite element simulations and experiments to study the effects of forming parameters on the forming limit angle and thinning rate of single-point incremental forming under isothermal local loading. The conclusions were further validated by changes in grain size in micrographs. The results showed that the forming limit angle of the AZ31B magnesium alloy sheet increased as the forming temperature increased. Maximum thinning first decreased and then increased, reaching the lowest point at 250 °C. At 250 °C, the grain size is large and evenly distributed, which is the best forming temperature. The radius of the tool head increases, the forming limit angle increases, the maximum thinning rate decreases, and the overall change of the average grain size is relatively small. However, the grain size is more uniform when the radius is 5 mm, and 5 mm is the best tool radius. The feed rate is inversely proportional to the forming limit angle and directly proportional to the maximum thinning rate. Different feed rates have different degrees of compression and elongation of the grains. The forming quality is better when the feed rate is 2 mm. The initial plate thickness is proportional to the limit angle, the maximum thinning rate, and grain size. And 1 mm is the best plate thickness to ensure the forming quality. This paper is important for developing the forming theory of isothermal local loading that can improve the high-performance forming of alloy parts in advanced manufacturing.
In this paper, experimental and numerical simulation studies on the forming limit diagram of single-point incremental forming (SPIF) were described. We proposed a novel method for evaluating the ...forming limit in incremental forming. The proposed method utilizes the forming limit angle and the maximum thinning rate. The effects of the forming and processing parameters on the forming limit of an aluminum sheet during incremental forming were investigated using a combination of simulation analysis and experimental verification. The obtained results show that the forming limit is large for 1060Al and 6061Al when the initial thickness is 1.5 mm for a single parameter change for SPIF. For 1060Al, the step size is in the range of 0.8–1.5 mm. When the step size is 0.8 mm, the incremental forming limit is large and the forming precision is high. For 1060Al and 6061Al, the incremental forming limit is at the maximum level when the tool radius is 6.0 mm, and when the tool radius is 5.0 mm, the best forming precision can be achieved. It is of great theoretical significance and practical engineering value to study the effects of various forming parameters on the forming limit of metal sheet SPIF.
Given an oval
C
in the plane, the
α
-isoptic
C
α
of
C
is the plane curve composed of the points from which
C
can be seen under the angle
π
-
α
. We consider isoptics of ovals parametrized with the ...support function
p
(
t
)
=
a
+
cos
n
t
,
n
∈
N
, and present an example of an oval such that when
α
increases, the
α
-isoptics begin to be convex, then lose their convexity and finally are convex again along a curve intersecting the isoptics orthogonally. Next we give an example of a curve from the same family, for which the curvature of the isoptics changes its sign three times. These changes occur on the symmetry axes of the oval
C
and coincide with the orthogonal trajectories which start at the points with extremal curvature. Finally, we formulate the hypothesis concerning the general case where we expect
n
-
1
convexity limit angles for the isoptics of an oval parametrized by
p
(
t
)
=
a
+
cos
n
t
.
Objectives In order to study the impact of the hydrodynamic performance of foil in the design of a wave glider,Methods on account of the characteristics of the oscillating foil when the wave glider ...is heaving, and based on the Dynamic Fluid Body Interaction(DFBI) module in STAR-CCM+ with the SST k-ω turbulence model, the passive oscillating process of foil when it is forced to heave is simulated. The effects of limit angles,wave heights and frequencies on the thrust coefficient of NACA 0012 flapping foil are investigated.Results We find that the passive rotation method can effectively simulate foil oscillating process, and its thrust coefficient is about 30% smaller than the coefficient obtained by the active rotation method. Moreover, the maximum limit angle of a wave glider of around 20° gives a better hydrodynamic performance. The numerical simulation result indicate that the thrust coefficient increases with the increase of wave height and wave frequency in a certain region.Conclusions This can provide a reference for propulsive performance and hydrodynamic performance under different states of the sea.
Sublevel caving mining causes surface deformation in three distinct zones parallel to the extracted deposit. Most of the published research is focused on the extent of the caved and fracture zones. ...The extent of the largest, continuous deformation zone and, thus, the influence of the mine on its surroundings is not yet fully documented. This study aimed at assessing the extent of surface deformation caused by the mining of a steep iron ore deposit in Norway. For this purpose, an innovative combination of the permanent scatterer (PS) InSAR technique and line-of-sight (LOS) movement data provided by a public web service and geographic information system (GIS) spatial interpolation methods was proposed. Two ascending tracks’ (A102 and A175) datasets spanning the period of 3 June 2016–11 October 2021 were used. Three interpolation methods, inverse distance weighted (IDW), radial basis function (RBF) and ordinary kriging (OK), were analysed in terms of their performance for mapping continuous deformation. The RBF and OK methods with anisotropy returned the lowest root mean square error (RMSE) values. The obtained difference in the maximum extent of deformation amounted to 26 m for the track A102 dataset and 44.5 m for the track A175 dataset, depending on the interpolation method used. The estimated maximum extent of the continuous deformation zone on the hanging-wall side of the sublevel caving mining operation is 663 m. This corresponds to a limit angle of 38.7 degrees, which is lower than in previously published studies. The results show that the influence of sublevel caving mining on the surroundings can be greater than previously thought. The usefulness of public PSInSAR data available from a national online service and spatial interpolation methods for determining the area of mining terrain deformations has been proven. The proposed approach provides a low-cost alternative and complementation for surveys performed about the mine and it is argued that it should be implemented as part of the mine’s monitoring system.
This study deals with the determination of the actual limit angles in the long-term formed subsidence basin in the Czech part of the Upper Silesian Basin (the remaining part lays in Poland). Here ...there was the most extensive underground exploitation of black coal in the north-east of the Czech Republic. A limit angle is absolutely decisive in the determination of deep mining influences in relation to the current and future utilisation of this territory. The two CSM and Paskov mine localities on the edge of the subsidence basin were selected for this study, since they could not have been affected by mining in neighbouring mines. On the grounds of the long-term levelling monitoring of points on the surface which started prior to mining, the horizontal distance between the mined out area and the undisturbed ground surface was identified. The impact of limit angle on the surface was calculated by means of the horizontal distance and the established mining depth. Such identified actual limit angles reached the values of 36° at the CSM Mine and 25° for the Paskov Mine. The calculated values are significantly lower when compared with the currently applied empirical values of 57° for the CSM Mine and 56° for the Paskov Mine. This means that the extent of the undermining effects is unambiguously wider by 611
m at the CSM Mine and by 883
m at the Paskov Mine. This study thus establishes the existence of a significantly vaster area influenced by coal deep mining than previously expected. The identified facts lead to the conclusion that regular revisions and follow-up updates of the empirically determined parameters are recommended.
► This study deals with determination of real limit angles in a subsidence. ► Limit angle is decisive in determination of deep mining influences. ► Horizontal distance between mined area and undisturbed ground surface was identified. ► Limit angle impact was calculated as horizontal distance and established mining depth. ► As a result, regular revisions and updates of empirically determined parameters are recommended.
A comprehensive joint orientation data collection program is necessary to ensure a sufficient degree of confidence in constructing a structural model. This paper investigates the influence of the ...number of joints sampled on the characterisation of the joint dip and dip direction. In a series of numerical experiments, Discrete Fracture Networks (DFNs) were used to model joint set populations. The average joint properties and the variation of the orientation cluster are obtained by simulating vertical and inclined boreholes in three different DFN models. The confidence level in the joint orientation data is calculated with the confidence limit method for different drilling densities. For comparable joint orientation data variability, a similar trend is observed regarding the confidence level and the number of joint sampled. Based on that trend, a series of recommendations were developed to estimate the number of joint to sample for a single joint set in order to reach a targeted level of confidence in the dip and dip direction data. Depending on the project requirements, the use of a range of levels of confidence and degrees of precision in the recommendations, can provide greater flexibility in design decisions. The proposed recommendations can be used to optimize the planning of geotechnical drilling campaigns for new mining projects or to review an existing structural database for an undergoing project identifying gaps in the data.
ncremental sheet forming (ISF) is one the manufacturing methods for sheet metal parts which has an increased rate of flexibility combined with relatively simple and cheap common technological ...equipment. This paper presents the results of researches on ISF performed on a CNC lathe, for thin sheet parts made of DC04Am mild steel. The main objective of the paper was to establish the maximum wall angle of the parts and its dependence on the main parameters of the process: thickness and diameter of the part, the tool radius, the feed rate, the spindle speed and the lubricating/cooling conditions. The tests were performed with original equipment designed by the authors and the results were commented and presented in diagrams and images of the parts. The main conclusion is that ISF on a CNC lathe can be successfully used for manufacturing conical shaped parts made of mild steel thin sheet, having a certain maximum angle of the parts wall, for small sized batches. The limit values of the parameters analyzed are a useful technological database for engineers.
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