Applied Mechanics and Materials Vols. 170-173

Abstract: In this paper, prestressed concrete continuous box grider with prestressing method was introduced, including construction technology, construction methods, main construction equipment, the main materials and semifinished products and the dispose of main problems in the construction of the processing.

Abstract: Based on the measured single-stage blasting vibration signal, time-frequency characteristics of two single-stage superposing signals were analyzed under the condition of different millisecond intervals ranging from 1ms to 350ms, also, variation laws of dominant frequency, amplitude and energy of the blasting vibration superposing signal with the delay time and the determination method of rational millisecond interval of similar engineering were put forward. Then, changing laws of the millisecond interval with the interference effect was obtained. It is found that, millisecond delay blasting does not follow the disturbance vibration reduction theory strictly that the vibration effect is weakened when interval is (2n-1)T/2 and strengthened when interval is nT, and the more similar the vibration characteristics of single-stage signals are, the larger the maximum amplitude declining rate of the obtained superposing signal is.

Abstract: This paper aims to achieve a crane real-time software programming methodology for estimating the fatigue life,the core idea of this method is to capture the whole life cycle of real-time stress load,gets real-time fatigue life results by using JIS and FEM and compares the two results.The method is more accurate than the traditional one and has guiding significance for real-time fatigue life estimation of port machinery.

Abstract: Geotechnical centrifuges are globally used to investigate the structures which of behaviors are strongly dependent on the physical properties of soil. A new 1.4 m diameter 450 g-Tonne drum centrifuge GT450/1.4, manufactured by Broadbent & G-max company, has been installed at Dalian University of Technology in 2009. Control and data acquisition systems are provided in modular form, allowing a flexible choice of sampling and recording modes. The details including the development of the facility, the additional accessories required and a centrifugal test of submarine landslide are described.

Abstract: According to the differential equation of thin elastic vibrating plate and the similarity theory, the similar relationships of corresponding parameters between model and prototype as well as between the ice-like material and the real ice are established. A high accuracy non-contact laser displacement measuring system is developed to obtain the surface deformation of the ice-like material. A speed measurement and positioning system is established for the moving air cushion load. At different moving speed of air cushion load, a series of experiments of the deformation of ice-like material are carried out in towing channel which the depth of water is variable. At critical speed the maximum deformation of ice-like material can be caused, and the theory is derived and analyzed. Research results present the basis of ice-breaking for practical air cushion vehicle (ACV).

Abstract: Blasting construction of Houyuntai Mountain tunnels has vibration influence on ground masonry structures. 3-D finite element model is established to analyze this problem which indicates the house’s vibration response velocity induced by blasting loads. According to this analysis, the structure range of removal and strengthening is assured based on the allowable safety standard of 0.02~0.025m/s of blasting vibration. They include that the houses in 20m range of both sides of horizontal tunnel axis should be removed; the security in 20~28m range is not good, as a result the houses should be removed or strengthened; and the security over 28m range is good for houses. Moreover, some factors such as construction quality can influence houses’ anti-vibration safety.

Abstract: Integral space concrete roof is a kind of new structure, it has the following characteristics: its integrity is very strong and the structure size is larger, its construction method is different from the general of roof structure. In order to promote its application, its construction method is researched by to adopt the technology of "high in-situ construction" and in combination with the construction a grain storehouse. In this paper, the key points of the construction is analysed and the key technology is researched, that’s including: the design of the holding bracket; the construction design of the high tension pedestal and the tension of the prestressed steel, etc. Then put forward the key points of the construction. Finally, the construction method of the roof is summarized, and the application conclusion is obtained.

Abstract: The signal to noise ration of air-coupled ultrasonic testing is very poor and there is long time pulse residue, so it need adopt appropriate signal processing method to enhancing the SNR of received signal. Factors, which affect the received signal in ultrasonic testing process, is analyzed, phase sensitivity detection technology is presented to process the received signal, and ultrasonic testing information can be acquired by the calculation of phase signal. The principle of super-heterodyne receiver and phase sensitivity detector is introduced; some problem which should be pay attention in ultrasonic testing process is explained. Based on the research result, air-coupled ultrasonic testing system with phase sensitivity detector is constituted. Experiment results of image testing on carbon fiber reinforced plastic plate indicated that, phase sensitivity detection technology can improved signal to noise ratio of system and testing effect in evidence.

Abstract: A lot of large area lands were made in China coastal areas by dredging sludge from the sea. The dredged fill ground had a very low bearing capacity which should be increased as soon as possible to meet the requirements of constructions. However, conventional vacuum preloading could not be used for this purpose because the sand cushion could not be laid on the sludge ground due to the very low bearing capacity. To solve this problem, a modified vacuum preloading method without sand cushion was proposed. This method has been successfully tested and applied in the reclamation project in Wenzhou. Based on this project, the technological process and the key technology were introduced and the reinforcement effect was analyzed. Project results showed the modified vacuum preloading method could achieve a good reinforcement effect on large area dredged fill ground in a short period. It is worth to promote the application of this method in coastal reclamation projects.

Abstract: By analyzing various factors which influence and constraint roadway construction speed in huaheng coal mine, some improved technical measures about fast construction are introduced, such as improve blasting technology, choose appropriate rock breaking equipment and improve the fast construction supporting facilities, select the right support patterns and scientific construction organization management. Take east roadway in huaheng coal mine as example, there are three key aspects: the method of mucking and haulage, drilling and blasting techniques and supporting technology. In solving the problem of loading and transport, some mechanized equipments such as LW150C bucket loader, SSD(B)20 shuttle mining car and CMJ17A full-hydraulic excavating jumbo are used, and the mechanized organization such as loading, transfer, transport and unloading is innovated. By improving bolt installation construction technology and optimizing construction management to achieve simultaneously operating of multiple procedure, increase drilling speed and shorten mucking time, which improved the roadway excavation speed and security significantly.