scholarly journals Dimensionless Charts for Predicting the Range of Goaf Roof Caving

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Jing Zhang ◽  
Rongxing He ◽  
Fengyu Ren ◽  
Zhihua Ouyang
Keyword(s):  
Numerical Simulation ◽  
Quantitative Evaluation ◽  
Working Conditions ◽  
Linear Interpolation ◽  
Hazard Evaluation ◽  
Potential Hazard ◽  
Fracture Spacing ◽  
Fuzzy Function ◽  
Roof Caving ◽  
Zero Growth

In engineering, the method of charts can provide a convenient query for specific engineering problems. To provide the basis for the potential hazard evaluation and rational governance of the goaf, it is necessary to study the quantitative evaluation for the range of goaf roof caving. Undoubtedly, the charts used to visually query the caving range can simplify the workload of the quantitative evaluation. Therefore, the methods of dimensional analysis, numerical simulation, and linear interpolation are introduced to study the dimensionless charts for predicting the caving range. The dimensionless analysis is used to establish the fuzzy function relationship among the influence factors of the goaf roof caving, and the numerical simulation is used to calculate the dimensionless groups in the fuzzy function. Using the linear interpolation, the dimensionless charts in this work can predict the range of goaf roof caving under more working conditions. The results show that the characteristics of the goaf roof caving corresponding to the dimensionless curves are consistent with the actual situation. With the continuous increase of the goaf span l, the dimensionless curves of the caving range experience zero growth, rapid growth, and steady growth. The growth degree varies with the fracture spacing S. Especially in the zero growth phase, the duration of the relatively stable state in the overlying strata of the goaf increases with the increase of fracture spacing S. Moreover, based on the case study of Shirengou Iron Mine, the dimensionless charts obtained in this work can predict the range of goaf roof caving under different working conditions, which indicates the findings of this study have certain guiding significance to the treatment of the goaf.

scholarly journals Prefabricated Urban Underground Utility Tunnels: A Case Study on Mechanical Behaviour with Strain Monitoring and Numerical Simulation

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Yonggang Xiao ◽  
Jubing Zhang ◽  
Jie Cao ◽  
Changhong Li
Keyword(s):  
Numerical Simulation ◽  
Working Conditions ◽  
Failure Modes ◽  
Mechanical Performance ◽  
Low Cost ◽  
Side Wall ◽  
Operating Conditions ◽  
Land Occupation ◽  
Depth Analysis ◽  
Simulation Results

The prefabricated urban utility tunnels (UUTs) have many advantages such as short construction period, low cost, high quality, and small land occupation. However, there is still a lack of in-depth analysis of the mechanical performance of the prefabricated urban utility tunnel (UUT) structure with bolted connections under different working conditions. In this paper, the force performance of a prefabricated UUT in Tongzhou District, Beijing, was studied under different working conditions using two methods: field monitoring and numerical simulation. The multichannel strain monitor was used for monitoring, and the internal wall concrete and bolt strain change data under the two conditions of installation and backfill were obtained. Combined with the construction process of the UUTs, a three-dimensional numerical model was established by COMSOL, where the build-in bolt assembly was used to simulate the longitudinal connection of the tunnel. The simulation results were compared with the measured data to verify the rationality of the computational model. The simulation results showed that the concrete and bolts on the inner wall of the tunnel work well under the two conditions of installation and backfilling; The deformation of the top plate of the prefabricated tunnel was approximately parabolic, with the largest vertical displacement (0.37 mm) in the middle and the most sensitive to the vertical load in the central part of the roof. The central portion of the side wall had the largest displacement (0.17 mm) in the inner concave. The tensile stress of bolt 3 increased the most (30.75 MPa) but was still much smaller than the yield strength of the bolt. The concrete and bolts of the UUT were found to work well through force analysis under operating conditions. In conclusion, analysis of structural forces and deformation failure modes will help design engineers understand the basic mechanisms and select the appropriate UUT structure.

scholarly journals An Approach Based on the Protected Object for Dam-Break Flood Risk Management Exemplified at the Zipingpu Reservoir

2019 ◽  
Vol 16 (19) ◽  
pp. 3786 ◽  
Author(s):  
Fan ◽  
An ◽  
Li ◽  
Li ◽  
Deng ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Risk Management ◽  
Flood Risk ◽  
Demographic Data ◽  
Flood Risk Management ◽  
Dam Break ◽  
Risk Level ◽  
Potential Hazard ◽  
Administrative Division ◽  
Protected Object

Dam-break flooding is a potential hazard for reservoirs that poses a considerable threat to human lives and property in downstream areas. Assessing the dam-break flood risk of the Zipingpu Reservoir in Chengdu, Sichuan Province, China, is critically important because this reservoir is located on the Longmen Shan fault, which experiences high seismic activity. In this paper, we develop an approach based on the protected object for dam-break flood risk management. First, we perform a numerical simulation of dam-break flooding in four possible dam break scenarios. Next, the flood areas are divided into 71 analysis units based on the administrative division. Based on the numerical simulation results and the socio-economic demographic data affected by a flood, the importance and risk level of each analysis unit is confirmed, and the flood risk map is established according to the classification results. Finally, multi-level flood risk management countermeasures are proposed according to the results of the unit classification shown in the map.

scholarly journals Experimental Research and Numerical Simulation on Grouting Quality of Shield Tunnel Based on Impact Echo Method

2016 ◽  
Vol 2016 ◽  
pp. 1-10
Author(s):  
Fei Yao ◽  
Guangyu Chen ◽  
Jianhong Su
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Working Conditions ◽  
Acoustic Impedance ◽  
Shield Tunnel ◽  
Test Results ◽  
Impact Echo ◽  
Simulation Results ◽  
The Impact ◽  
Impact Echo Method

To identify shield grouting quality based on impact echo method, an impact echo test of segment-grouting (SG) test piece was carried out to explore effect of acoustic impedance of grouting layers and grouting defects on impact echo law. A finite element numerical simulation on the impact echo process was implemented. Test results and simulation results were compared. Results demonstrated that, under some working conditions, finite element simulation results and test results both agree with theoretical values. The acoustic impedance ratio of SG material influenced the echo characteristics significantly. But thickness frequency could not be detected under some working conditions because the reflected energy is weak. Frequency feature under grouting defects was more complicated than that under no grouting defects.

Numerical study on instantaneous radial force of a centrifugal pump for different working conditions

2019 ◽  
Vol 37 (2) ◽  
pp. 458-480
Author(s):  
Xiaoqi Jia ◽  
Sheng Yuan ◽  
Zuchao Zhu ◽  
Baoling Cui
Keyword(s):  
Numerical Simulation ◽  
Unsteady Flow ◽  
Centrifugal Pump ◽  
Working Conditions ◽  
Flow Rate ◽  
Pressure Pulsation ◽  
Radial Force ◽  
Leakage Rate ◽  
Content Type ◽  
Three Components

Purpose Instantaneous radial force induced from unsteady flow will intensify vibration noise of the centrifugal pump, especially under off-design working conditions, which will affect safety reliability of pump operation in severe cases. This paper aims to conduct unsteady numerical computation on one centrifugal pump; thus, unsteady fluid radial force upon the impeller and volute is obtained, so as to study the evolution law of instantaneous radial force, the internal relationship between radial force and pressure pulsation, the relationship among each composition of radial force that the impeller received and the influence of leakage rate of front and back chamber on radial force. Design/methodology/approach The unsteady numerical simulation with SST k-ω turbulence model was carried out for a low specific-speed centrifugal pump using computational fluid dynamics codes FLUENT. The performance tests and pressure tests were conducted by a closed loop system. The performance curves and the pressure distribution from numerical simulation agree with that of the experiment conducted. The unsteady pressure distributions and the instantaneous radial forces induced from unsteady flow were analyzed under different flow rates. Contribution degrees of three components of the radial force on the impeller and the relation between the radial force and leakage rate were analyzed. Findings Radial force on the volute and pressure pulsation on the volute wall have the same distribution tendency, but in contrast to the distribution trend of the radial force on the impeller. In the component of radial force that the impeller received, radial force on the blade accounts for the main position. With the decrease of flow rate, ratio of the radial force on front and back casings will be increased; under large flow rate, vortex and flow blockage at volute section will enhance the pressure and radial force fluctuation greatly, and the pulsation degree may be much more intense than that of a smaller flow rate. Originality/value This paper revealed the relation of the radial force and the pressure pulsation. Meanwhile, contribution degrees of three components of the radial force on the impeller under different working conditions as well as the relation between the radial force and leakage rate of front and rear chambers were analyzed.

Calculation Methods for Hazard Evaluation of Diffusely-Reflected Laser Emission at Special Assessment of Working Conditions

2019 ◽  
Vol 7 (3) ◽  
pp. 19-26
Author(s):  
В. Кибовский ◽  
V. Kibovskiy ◽  
Б. Рахманов ◽  
B. Rahmanov ◽  
С. Тихомиров ◽  
...  
Keyword(s):  
Laser Radiation ◽  
Working Conditions ◽  
Laser Emission ◽  
Hazard Evaluation ◽  
Calculation Methods ◽  
Special Assessment

Have been considered calculating methods for hazard evaluation of diffusely-reflected laser radiation at work places for operators of laser technological units (LTU), realized for purposes of special assessment for working conditions (SAWC). Examples for calculating SAWC at work places for operators of modern LTU applied in shipbuilding have been given.

Study of Numerical Simulation in Failure Modes of Waste Dump Slope

2015 ◽  
Vol 1092-1093 ◽  
pp. 748-752 ◽  
Author(s):  
Shao Jie Feng ◽  
Yan Fei Dong ◽  
Shi Guo Sun ◽  
Sheng Lei Kan
Keyword(s):  
Numerical Simulation ◽  
Slope Stability ◽  
Working Conditions ◽  
Failure Modes ◽  
Simulation Method ◽  
Single Step ◽  
Waste Dump ◽  
Numerical Simulation Method ◽  
Dump Slope ◽  
Better Than

Based on the numerical simulation method and a sample slope engineer of waste dump, the failure modes of waste dump slope is analyzed. By means of analyzing working conditions such as different slope angles, single step, many steps, the failure modes of waste dump slope under different working conditions is obtained. The results show that the slope stability of multiple steps waste dump is better than the slope stability of single step waste dump, and the deformation of the slope is small.

Numerical Investigation for Fracture Saturation in Multilayer Sedimentary Rock in Unsymmetrical Case

2013 ◽  
Vol 690-693 ◽  
pp. 3050-3053
Author(s):  
Feng Shan Han ◽  
Li Song
Keyword(s):  
Numerical Simulation ◽  
Layer Thickness ◽  
Sedimentary Rock ◽  
Process Analysis ◽  
Failure Process ◽  
Bottom Layer ◽  
Thickness Ratio ◽  
Fracture Spacing ◽  
Layer Thickness Ratio ◽  
Rock Failure Process

Opening mode fractures in multilayer sedimentary rock often are periodically distributed with fracture spacing scaled to the thickness of the fractured layer. In this paper, based on Rock Failure Process Analysis Code RFPA2D, a three layer model with a central layer and with the different thickness top and bottom layer, progressive formation in multilayer sedimentary rock at fracture saturation in unsymmetrical case is simulated. We investigate the change of the critical fracture spacing to layer thickness ratio as a function of the thickness of the top layer where the bottom layers is much thicker (5 times) than the fractured layer called the unsymmetrical case, in this unsymmetrical case, fracture saturation is simulated. By numerical simulation of RFPA2D, the critical spacing to layer thickness ratio decreases and tend to the same constant value as the thickness of the top layer increases. Numerical simulation shown that for the unsymmetrical case, if the adjacent layers are thicker than 1.5 times the thickness of the fractured layer, the multilayer sedimentary rock can be treated approximately as a system with infinitely thick top and bottom layers at fracture saturation.That should be useful in the design of engineering systems and in the prediction of fracture spacing in hydrocarbon reservoirs and groundwater aquifers.

A Study of the Influences on Stress and Temperature Caused by Different Wire Drawing Parameters by Numerical Simulation

2013 ◽  
Vol 803 ◽  
pp. 489-495
Author(s):  
Peng Jie Sun ◽  
Fen Lou Zhai ◽  
Dong Xu Liu ◽  
Jia Li Yan ◽  
Jing Ning
Keyword(s):  
Numerical Simulation ◽  
Working Conditions ◽  
Cone Angle ◽  
Wire Drawing ◽  
Experimental Results ◽  
Drawing Die ◽  
Drawing Speed ◽  
Temperature Experiment ◽  
Steel Cords ◽  
Hole Structure

This paper analysed the first-step of dry drawing of steel cords by numerical simulation. In different working conditions,a couple of simulations were made to analyses the influences on stress and temperature,different work cone angle,drawing speed,high of die bearing . Afer measuring the actual data of temperature experiment, the experimental results were in good great agreement with numerical simulartion.In this paper,some measures were concluded to reduce the drawing stress and temperature,which have guiding significance for the production of steel cord.Key words:Wire drawing die;Hole structure;Temperature;Decoupling

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