Three Dimensional Numerical Simulation of Rock Core Discing Based on Strain Soft Model

2011 ◽  
Vol 187 ◽  
pp. 565-569
Author(s):  
An Nan Jiang ◽  
Zheng Wen Zeng
Keyword(s):  
Numerical Simulation ◽  
Stress Concentration ◽  
Three Dimensional ◽  
Drilling Depth ◽  
Feedback Analysis ◽  
Concentration Degree ◽  
Pressure Stress ◽  
Core Discing

Aiming at the complexity of rock discing mechanics, and the theory being not mature, the paper carried out three-dimensional numerical simulation for rock core discing based on strain soft model. The strain soft theory is introduced firstly, then numerically simulated how the depth of lug boss and original stress affect the rock core destroy pattern(discing if occurs, the thickness of disk), obtained the characters of rock core discing. Along with the drilling depth increases, the stress concentration scope below lug boss also increases, as well as the pressure stress concentration degree of side corner below of lug boss. Rock core discing can be induced respectively by shear action and tension action, sometimes it is combined by both of them. The destroy pattern of them especially destroy sequence are different. The strain soft numerical simulation could be used in original stress feedback analysis, has significant meaning.

Influence of Slope Gradient on Distribution Rule of Geostress Field in River Valleys

2013 ◽  
Vol 404 ◽  
pp. 365-370 ◽  
Author(s):  
Qi Tao Pei ◽  
Hai Bo Li ◽  
Ya Qun Liu ◽  
Jun Gang Jiang
Keyword(s):  
Numerical Simulation ◽  
Stress Concentration ◽  
Principal Stress ◽  
Three Dimensional ◽  
Maximum Principal Stress ◽  
Slope Gradient ◽  
Bank Slope ◽  
Distribution Rule ◽  
River Valleys ◽  
Gradient Change

During the construction of hydropower station, the change of slope gradient in river valleys often takes place. In order to study influence of slope gradient change on distribution rule of geostress field, the three dimensional unloading models under different slope gradients were established by finite difference software (FLAC3D). After numerical simulation, the results were as follows: (1) The phenomenon of stress concentration at the bottom of river valleys was obvious, which appeared the typical stress fold. Both the depth of stress concentration zone and the principal stress values significantly increased with the increment of slope gradient. (2) Maximum principal stress values increased less in shallow part of upper bank slope (low stress zone) but increased more in the nearby slope foot with the increment of slope gradient, causing great difference in geostress field of bank slope. (3) There was some difference in released energy of bank slope due to slope gradient change in river valleys. In order to distinguish the difference, stress relief zone was further divided into stress stably released zone and stress instability released zone. Finally, take Ada dam area of the western route project of South-to-North Water Transfer as an example, the results by numerical simulation were reliable through comparing the distribution rule of geostress field for the dam, which could provide important reference for stability of the design and construction of steep and narrow river valleys.

Improvement of performance of bolt-nut connections, Part I: Simulations

2014 ◽  
Vol 228 (17) ◽  
pp. 3069-3077 ◽  
Author(s):  
GH Majzoobi ◽  
M Agh-Mohammad Dabbagh ◽  
P Asgari ◽  
MK Pipelzadeh ◽  
SJ Hardy
Keyword(s):  
Numerical Simulation ◽  
Fatigue Life ◽  
Stress Concentration ◽  
Numerical Simulations ◽  
Load Distribution ◽  
Inflection Point ◽  
Close Agreement ◽  
Three Dimensional ◽  
Fatigue Tests

The performance of bolt-nut connections can be improved by enhancing fatigue life of the connections. This can be accomplished by reducing the stress concentration in the threads of the connection. This investigation consists of two parts. In this part (part I), load distribution in threads of some ISO bolts is computed by three-dimensional numerical simulation and Stockley-proposed relations. The results show a close agreement between Stockley relations and the simulations for nearly all bolt sizes. The results indicate that stress concentration is nearly constant regardless of the bolt size. It is also found that the load percentage carried by the first thread varies from 35% for M6 and reaches to 58% for M20 and M30 ISO bolts. The results suggest that the rate of load distribution changes at a point of inflection, i.e. the rate after the inflection point diminishes as the bolt size decreases, whereas before this point, the trend of the rate is reversed. In part II (to be submitted separately), various techniques are employed for the reduction of stress concentration and enhancement of fatigue life of the connections. The techniques are evaluated by numerical simulations and fatigue tests.

scholarly journals A Nonlinear Optimization Technique of Tunnel Construction Based on DE and LSSVM

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Xing Jun ◽  
Jiang Annan ◽  
Wen Zhiwu ◽  
Qiu Jingping
Keyword(s):  
Numerical Simulation ◽  
Support Vector Machine ◽  
Nonlinear Optimization ◽  
Computing Time ◽  
Optimization Technique ◽  
Three Dimensional ◽  
Least Square ◽  
Support Vector ◽  
Tunnel Construction ◽  
Feedback Analysis

Tunnel construction is a dynamic controlling system with observability and controllability; the feedback analysis requires identifying geophysics parameters and adjusting supporting parameters, and both of them are optimisation problems. The paper proposed a nonlinear optimization technique based on difference evolution arithmetic (DEA), least square support vector machine (LSSVM), and three dimensional numerical simulation. This method employs support vector machine with optimal architecture trained by the difference evolution arithmetic, instead of the time-consuming finite element analysis. Firstly, the three dimensional numerical simulation is used to create training and testing samples for LSSVM model construction. Then the nonlinear relationship between rock or anchoring parameters and displacement is constructed by support vector machine. Finally, the geophysics and supporting parameters are obtained by DE optimization arithmetic. The technique overcomes the conventional optimization method shortages of expending too much computing time and easily being limited in local optimal solution. This technique was verified by applying it to the feedback analysis of Dalian Metro in China, and the influence of the parameters of LSSVM and DE on the simulation ability of the algorithm was investigated.

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