The concrete compression strength is an effective characteristics among other properties of practical significance. Although coring testing on such members as columns is not recommended. But ...sometimes, for determining the concrete strength in the column, this method should be applied to the reinforced concrete one. Coring in a reinforced concrete column creates a cylindrical cavity in it, which has an apparently negative effect on the bearing capacity of the structural member. The effect of different sizes of cavities on uniaxial compression strength of concrete was investigated based on the experiment and numerical simulation (particle flow code). The results of the experiments show that the cavities have a great influence on the uniaxial compression strength. For example, if the cavity volume is calculated about 14% of the sample volume, it can reduce of the uniaxial compression strength down to 58%. If the cavity diameter is 60% of the sample width, the strength can go down to 74%.
Tunneling operations in urban areas are always associated with surface and subsurface ground movement, which may affect the stability of nearby structures and utilities. One of the main issues in the ...analysis and design of tunnels, is ground movement after the support systems and settlement systems caused by excavation. This paper takes the discrete element calculation software of Universal Distinct Element Code (UDEC) to set three dimensional calculations models to simulate the construction of Esfahan subway tunnel, analyzing the displacement and stress dynamic response during the construction process. The paper also carries out the comparison analysis of the field measurement of the ground movement. The result indicates that the simulation objectively reflected the rules of movement during the construction process. The results show that the tunnels are stable before support system installation and the tunnel induced movement is allowable.
Safety during construction and long-term stability of tunnels is among important factors in the design and implementation of underground spaces. Since tunnels and underground spaces are under dynamic ...loads such as earthquakes and explosions during construction and operation stages, dynamic stability analysis of such structures is of great importance. In this study, the twin tunnels of Shiraz subway were numerically modeled under static and dynamic loads with the help of Universal Distinct Element Code (UDEC). This is a finite element method (FEM) software, is any of a family of numerical methods. Unbalanced forces increase after tunnel excavation and applying static and dynamic loads. Although the increase in unbalanced forces was higher under dynamic loads, under static loads, velocity and displacement changes in the ceiling of the tunnel were higher than the rest of the tunnel. To apply a dynamic load, a sine wave was applied to the lower boundary of the model. After applying the dynamic load, velocity and displacement changes of the tunnel floor were higher than the rest of the tunnel. According to modeling results, the twin tunnels are quite unstable under static and dynamic loads and need a support system.
Slope stability accidents are one of the leading causes of destruction at open pit mining operations. Such interception of the seepage water results in the water inflow from the surrounding aquifer ...towards the mine excavations. In order to design an effective drainage scheme for an open pit mine, prediction of water inflow into the pit is essential. These changes have resulted in some failures and instability problems in different parts of Gol-E-Gohar iron open pit mine. It seems that main parameters which effect the failure and instability of the mine slopes are high pressure of groundwater and system of discontinuities (faults, joins, and bedding planes), which intersect the pit walls. The analysis results indicate that stability of the final pit slopes is sensitive to multi-planar failures and confined water in the walls pit is also a factor adversely affecting the stability. Problems associated with groundwater at the site were also assessed with the analyses of piezometric level and groundwater inflow.
This research studies the effect of gravel pack size on sand production by designing and manufacturing a machine and a numerical model to simulate sand and gravel pack. This machine and the numerical ...model make it possible to test different rock along with various fluids under different stress in order to simulate the production of sand and gravel pack.PFC
3D
software is applied to create this numerical model. The numerical model consists of sand from 0.22 to 1.1 mm and gravel pack from 3.5 to 4.76, 4.76 to 9.9 to 12.6 and 12.6 to 16.8 mm and the physical model holds gravel from 9 to 4.76 and 4.76 to 9.25. The results from modeling demonstrated that sand is produced the least in the numerical model using gravel from 3.5 to4.76 mm and sand is produced less in the physical model containing gravel pack ranging from 4.76 to 9 mm and the fluid left more output discharge. Moreover, the outcomes from physical modeling proved that as time drags on, the fluid production rate got reduced and then reached to a fixed amount after placing gravel pack. So, it is suggested that gravel pack from 9mm to 4.76mm is more suitable from the viewpoints of fluid production rate and prevention of sand production. Based on dimensional analysis and the results from numerical modeling in a condition without gravel pack, a relation is concluded to estimate sand production rate.
Erratum to: Publisher’s Erratum Adushkin, V. V.; Kishkina, S. B.; Kulikov, V. I. ...
Journal of mining science,
2017/9, Letnik:
53, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Due to a technical error volume 53, issue 4, 2017 has been published online with an incorrect cover data. The issue has erroneously been distributed with the cover date July 2018. The correct caver ...date for volume 53, issue 4 should be July 2017.
One of the most important issues in geotechnical studies is bearing capacity. It is also defined as the resistance when the maximum pressure is exerted from the footing to the foundation without ...creating shear failure therein. Since earing capacity is highly correlated with the stability of surface and subsurface structures, researchers have become interested in this subject. The area and geometry impacts on the footing are considered as the two important issues in this regard. In this research, a numerical model based on particle flow code was used in PFC3D software. To do experiments in numerical models, two triple-facet footings were utilized in square, rectangular and circular geometric shapes. Furthermore, these footings held a total area of 64 cm2 and other series included a full area of 49 cm2. In the modeling, the mechanical properties of granite were put into practice and the results of the numerical tests were scrutinized, as well. As a result, it was ascertained that the bearing capacity depends on both the footing geometry and the footing area.
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