Study on Crack Mechanism for Concrete Bedding Cushion on Rock

2010 ◽  
Vol 163-167 ◽  
pp. 1291-1295 ◽  
Author(s):  
Min Zhi Liu ◽  
Sheng Qiang ◽  
Zhen Yang Zhu

Bedding cushion cracking in concrete dam is widespread, and has not been completely prevented [1,2]. There are many cracking causes of bedding cushion, including construction difficulty and structure requirements for concrete dam. Based on the method of FEM simulative calculation of temperature and stress fields of mass concrete using water cooling pipes, this paper makes relatively in-depth study on crack mechanism for concrete bedding cushion on rock. It is revealed that all three factors of uneven thickness of bedding cushion, thickness of new dam concrete placed on cushion after off period and foundation gallery upon bedding cushion have great influence on the tensile stress of bedding cushion and should be paid special attention during construction. The calculation results show that the tensile stress of thinner concrete cushion layer is much greater than the thicker one, and the thinner upon new concrete will also make greater tensile stress in cushion. As a result, both the thinner cushion layer and the cushion with thinner new concrete on it would have a bigger chance to crack than others. The mechanism is used to explain reasonably a dam crack in construction. Then some cracking prevention measures, which should have reference value for the construction of bedding cushion, are put forward in this paper.

2020 ◽  
Vol 165 ◽  
pp. 04037
Author(s):  
Zhi-Gang Yang ◽  
Jin-Lan Song ◽  
Yan-Fang Hu ◽  
Kun-Fa Lee

For studying the influence of cooling pipes on the mass concrete construction, the dam is taken an example to build the ANSYS finite element model. The model simulates dam concrete construction based on two projects, one without cooling pipes and the other with cooling water pipes provided. The data comparison and analyzing will be in three aspects: temperature, stress and displacement. The result shows that the cooling pipes not only can indeed reduce the concrete temperature in a short time, making the concrete reach the steady temperature more quickly, but also help to alleviate the concrete temperature stress. However, the reductions of temperature do not make a great influence on the displacement during the construction process.


2020 ◽  
Vol 37 (8) ◽  
pp. 2619-2640
Author(s):  
Zhenyang Zhu ◽  
Yi Liu ◽  
Zhe Fan ◽  
Sheng Qiang ◽  
Zhiqiang Xie ◽  
...  

Purpose The buried pipe element method can be used to calculate the temperature of mass concrete through highly efficient computing. However, in this method, temperatures along cooling pipes and the convection coefficient of the cooling pipe boundary should be improved to achieve higher accuracy. Thus, there is a need to propose a method for improvement. Design/methodology/approach According to the principle of heat balance and the temperature gradient characteristics of concrete around cooling pipes, a method to calculate the water temperature along cooling pipes using the buried pipe element method is proposed in this study. By comparing the results of a discrete algorithm and the buried pipe element method, it was discovered that the convection coefficient of the cooling pipe boundary for the buried pipe element method is only related to the thermal conductivity of concrete; therefore, it can be calculated by inverse analysis. Findings The results show that the buried pipe element method can achieve the same accuracy as the discrete method and simulate the temperature field of mass concrete with cooling pipes efficiently and accurately. Originality/value This new method can improve the calculation accuracy of the embedded element method and make the calculation results more reasonable and reliable.


Author(s):  
ZH Yuan ◽  
SY Guo ◽  
SN Zhang ◽  
JQ Zhao ◽  
WJ Lu ◽  
...  

Based on the suspension of a missile using folding rotary wings and airbags, in order to improve the basic parameters and motion characteristics of the rotor during the unfolding process and analyze the aerodynamic characteristics of the entire device in the suspension state, after proposing a scheme of double-spin mechanism, the main folding and unfolding mechanism, initial driving device, rotating driving device, and locking mechanism were designed, and the simulation research is studied by the Automatic Dynamic Analysis of Mechanical System and Ansys Fluent Fluid Simulation software, respectively. The results show that the rotation rate was controlled at 41.8 mm/s, the various motion parameters are reasonable, and the operation process is relatively smooth, with high reliability. The speed and pressure value at the tip of the rotor are higher and the aerodynamic disturbance is obvious, which has a great influence on the aerodynamic performance. The speed and pressure distribution of the surrounding flow field is stable, the lift provided is 46 N, and the lift coefficient is 0.55, which can ensure the long-time suspension state of the missile. This paper puts forward a valuable design idea and has practical reference value for the research of the suspended missile.


2017 ◽  
Author(s):  
Keshi You ◽  
Feng Wang ◽  
Liujiang Wang ◽  
Zhongwei Zhao ◽  
Yun Liu

2018 ◽  
Vol 38 ◽  
pp. 03020 ◽  
Author(s):  
Zheng Si ◽  
Qian Zhang ◽  
Ling Zhi Huang ◽  
Dan Yang

Most existing temperature field calculation programs have relative defects. In the present paper, based on merits of ANSYS platform, a temperature field calculation program of mass concrete structure is developed and demonstrated. According to actual pouring progress and thermodynamic parameters, a roller-compacted concrete dam is simulated. The difference of maximum temperature between calculated and measured values of measuring points is less than 1.8°C. Furthermore, the relative difference is -5%–5%. This result shows that the calculation program developed based on ANSYS platform can simulate and calculate the temperature field of mass concrete structure.


2019 ◽  
pp. 48-57
Author(s):  
Nina Klymenko

The article deals with the concept of a general theory of forensic expertology, the conditions for its creation, the place of forensic expert science in the system of legal sciences, the limits of its subject matter, the issues of interaction and the relationship of the science of forensic science and forensic expertology. The system and structure of the general theory of forensic expertology and its tasks are given. Separate articles of the Criminal Procedure, Civil Procedure, Administrative, Economic, Customs and Other Codes of Ukraine, the Law of Ukraine “On Forensic Expertise” of 1994 and the constitutional confirmation (article 92, paragraph 14 of the Constitution of Ukraine) of the legislative provision of forensic expertise are the further legal basis development of legal, organizational and managerial directions of forensic expertology. Forensic expertology does not only preserves the “birthmarks” of forensic science, but also, in turn, influences the dialectics of the development of the subject of forensic science and the content of its scientific fields (forensic techniques, forensic tactics and forensic methos). In particular, it requires clarifying the well-established view of the unity of forensic techniques for the investigator and expert. The first is made to collect “trace information”, the second is used for its in-depth study based on special knowledge in order to turn it into evidence-based information. Different goals are provided with different means of content. It is more accurate to raise the question of interaction, the “docking” of two, although closely related, but independent branches of scientific and technical means serving justice. The tasks of the general theory of forensic expertise (expert studies) are similar to the tasks of forensic science. They can be divided into general and special. General task is the creation of a scientific base for the purpose of the functioning and development of the industry of the use of special knowledge in examinations for the needs of legal proceedings, assistance in the fight against crime and other offenses, resolution of civil law disputes. Special task is the study of the laws of formation and development of specific types of forensic expertises, the expansion of their capabilities; development and improvement of expert technologies, tools, methods and techniques; the formation of the scientific foundations of new types of forensic expertises in connection with the emergence of new objects (computer, art history, etc.); developing expert crime prevention measures; development of an automated workplace software (AWS) for an expert of various types of research, study and implementation of advanced expert experience; forecasting expert practice processes and research tasks. Specific tasks are the up-to-date tasks that the practice puts before so the science of expert science to meet the needs that have arisen. Key words: forensic expertology, forensic expertise, legal science, theory.


2020 ◽  
Vol 12 (11) ◽  
pp. 168781402097353
Author(s):  
Wang Yanhua ◽  
Huang Longlong ◽  
Liu Yong ◽  
Xu Jingsong

At present, in the aspect of numerical simulation of cycloid pump, most studies focused on CFD (Computational Fluid Dynamics) in analyzing the pump performance under different service conditions (such as speed, temperature, etc.). The characteristics of the pump under FSI (Fluid Solid Interaction) have not been considered yet. By means of the dynamic mesh technique in the rotating domain, the fluid structure coupling interface is set up on a cycloidal pump model building in COMSOL. The simulation results obtained by applying CFD and FSI are improved by experimental verification. The results show that: (1) the average flow rate of FSI simulation is closer to the test results, and the mean values of CFD and FSI pressure are closer to the actual outlet boundary settings; (2) by comparing the velocity and pressure of rotation region of CFD and FSI at different temperatures, it is concluded that the pressure CFD calculated in the region is more than FSI, and the velocity CFD calculated is less than FSI; (3) by comparing the pressure distribution at some contact point of the fluid structure coupling interface, it is concluded that the fluctuation value of the pressure of CFD with time is greater than that of FSI. Through the comparison, it is found that the coupling has a great influence on the calculation results. The FSI analysis of the pump makes the analysis results more real and more conducive to the analysis of the flow field and rotor dynamics characteristics of the pump.


2014 ◽  
Vol 1006-1007 ◽  
pp. 275-279
Author(s):  
Guo Qing Liu ◽  
Cheng Xu

The bullet-rifle coupling model of sniper rifle has established to study the impact of bullet mass eccentricity on initial disturbance. This coupling model was established based on nonlinear finite element method and used to simulate the launch process of sniper rifle under the condition of gravity static equilibrium in the method of the mixing calculation which had advantages of both dynamic explicit algorithm and static implicit algorithm. The impact of different initial position of mass center on bullet swing angular displacement and centroid displacement was considered. Numerical calculation results shows that bullet mass eccentricity has a great influence on initial disturbance, the bullet swing angular displacement and centroid displacement is closely related to initial position of mass center. In addition, there is proportionality between bullet swing angular displacement and axial velocity before it reaches limit. That is helpful to carry out further study of how to control the influence of mass eccentricity on initial disturbance.


2011 ◽  
Vol 194-196 ◽  
pp. 248-254
Author(s):  
Shao Jun Chu ◽  
Pei Xiao Liu ◽  
Pei Xian Chen

The burden calculation of ferromanganese alloy was calculated based on the slag composition and designed product. The calculation results showed the total error rate of this method was 1.53% and the error rate of ore, coke and silicon was 4.66%, 1.71%, and 5.66% respectively, which was much better than using the traditional elements recovery method with the total error rate was 8.00% and the silicon error rate reached to 18.55%. This new method is more accurate than the traditional method and much closer to the actual production data. And it can apply to different ferroalloy factories because it is based on phase diagram and the mass conservation law. At the same time, the calculation result can reflect the gap between enterprise production craft level and ideal production level. This method has certain reference value to improve production technology, product quality and economic profit of enterprise.


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