Advanced Materials Research Vols. 243-249

Abstract: Force transmission triangular box as the bracing’s bracket is widely applied in the deep foundation, but its performance was not studied in depth. In order to evaluate the working performance of force transmission triangular box as bracing’s bracket, the paper use the finite element software ANSYS to simulate and analyze its mechanical behavior. The bearing capacity, deformation and stress distribution of the components were discussed and compared with the result from elastic bending theory of small deflections of its end-plate deflection. The dangerous sections of member and the inner force distribution in the general work load status were obtained. And the stress concentration was improved. the results can provide reference for the design and construction.

Abstract: Based on the segmental joint tests, it was found that the practical range of joint flexural rigidity was in range of 8500-29000kN•m/rad. A simplified method for determining the stiffness reduction factor of tunnel lining() was proposed using results from the segmental joint tests in which some parameters were obtained by calibration against a 3D Numerical analysis. The influence of joint flexural rigidity, soil resistance coefficient, thickness of tunnel lining and tunnel calculation radius on the stiffness reduction factor of tunnel lining was examined. The stiffness reduction factor can be simply expressed as a function of joint flexural rigidity ratio, soil resistance coefficient, thickness of tunnel lining and tunnel calculation radius for the typical tunnel lining.

Abstract: Through the survey about the durability of existing railway and road tunnels, it is found that there are different kinds of defects in most tunnels concerning poor durability. This phenomenon exists for a number of reasons among which the main ones are geological conditions , hydrological conditions, types of concrete structures, poor grading, larger second lining thickness, excessive larger stiffness and the poor quality construction. Solutions of these problems are provided in this paper. Specific measures are using multiple composite cementitious materials (the cocktailtreatment), providing composite cementitious materials with mixing station mode, using effective superplasticizer with low water-cement ratio and small water usage, adding appropriate amount of cellulose fibers in concrete, emphasizing the initial support and belittling the secondary lining, using reasonable maintaining technology, using new technology of Waterproof Plate. These measures may serve as reference for tunnels’ design and construction.

Abstract: The aerodynamic numerical simulation model of high-speed railway tunnel was established based on the analyzing of the aerodynamic effect characteristics of high-speed railway tunnel. FLUENT three dimensional compressible flows SIMPLE algorithm was adopted, the three dimensional aerodynamic effect of high-speed railway tunnel was simulated on the condition that the high-speed train was in motion. The pressure changes law in the tunnel was obtained during the whole process when high-speed train traveling, and the pressure-time curve in the tunnel middle cross-section was plotted. It laid a foundation for the further development of tunnel lining dynamics analysis.

Abstract: This paper is a studying on the Al-Shuhadah Bridge lies in the Muthanna province south of Iraq, including the soil investigation taken from the project and analysis for the designed bridge firstly manually by using equations 1 and 2 according to the data provided, secondly by using three dimensional Plaxis program of finite elements. The settlement calculated by the above two ways is nearly similar and considered reasonable values compared with the allowable settlement according to Skempton and McDonald (1956) limitations for maximum settlement and maximum angular distortion. The bearing capacity of the bridge also calculated by using equation 3 and the value is larger than the applied load due to the effect of truck loading, while the study found that the bridge is not suitable to carry the dynamic loads due to the effect of train action; therefore, this bridge is used for the highway only and can success for this purpose.

Abstract: The textural stress has great effect on the stability of rock. According to the measured geo-stress data, through FEM and combined with the linear multivariate regression method, the geo-stress field was conducted. Using these methods, a diversion tunnel of a large-scale hydropower station was analyzed to study the stress distribution. It was shown that the stress concentration was located at the bottom of the wall and the arch top, the stress in the wall was little and the failure happened at the bottom of the wall and the arch top, then the bottom board and some areas far from the tunnel. Under the condition without considering textural stress, the stress concentration area located in the wall and the failure happened at the bottom of the wall, then in the middle of the wall and at the arch top.

Abstract: The thought and method are put forward to deal with the difficulties in prediction of water-gush yield in long tunnels. The conceptual model of hydrogeology should be developed first based on investigating and analyzing the hydrogeology conditions of tunnel. Then, several different models should be adopted together to comprehensive calculate water-gush yield. Finally, by adopting methods of numerical simulating method, rainfall infiltration method and fuzzy comprehensive evaluation method, the comprehensive prediction thought presented above is applied and verified in Nanliang tunnel engineering practice.

Abstract: The work presented in this paper focuses on support time for tunnel, which has much effect on stability of tunnel. Based on loess tunnel of Zhengzhou-Xi’an high-speed passenger rail line in China, large scale model test with geometric proportion 1: 20 was applied to study on different support time. Supplemental numerical analysis was carried out to investigate the effect of release ratio of stress which cannot be covered by model test. It is revealed that it is asynchronous change for deformation, strain and stress of surround rock. If the supporting constructs prematurely, internal force of support would be excessive greatly and if the supporting constructs too late, it will bring excessive slack pressure which leads to the plastic zone unfavorable, even tunnel collapse. The reasonable support time can improve self-bearing capability of surrounding rock and reduce the cost. The limited displacements about 17.8 cm for crown and 12.9 for horizontal convergence are gained. The research results can act as reference for similar materials tunnel and underground engineering construction.

Abstract: Since karst landform distributes widely in south China, highway and railway construction usually adopt the method of embedding long and large tunnel in great depth so that they could pass these karst areas safely. Water outburst and mud outburst accidents occurring on the stable karst area are major hazards in highway and railway construction and operation. The grave mud outburst accident occurring at the entrance of Yuanliangshan Tunnel has the following features: (1) the dissoluble rocks distribute widely, possessing a sound catchment capacity. (2) Water storage structure exists above the elevation of tunnel body; (3) feature of geologic structure and attitude of stratum in that area benefit the development of karst; (4) underground karst pipe is smooth and unobstructed. And there are certain underground rivers. (5) Besides, the thickness of water-proof layer has less power than the hydraulic pressure of ground water. (6) Karst mud outburst hazard features suddenness and concealment. Taken the example of Yuanliangshan Tunnel, the paper conducts preliminary analysis and careful calculation of the speed of karst mud outburst and its impact force, providing some research ground for disaster assessment and prevention.

Abstract: In this paper, Shape Memory Alloy (SMA) Pseudo-Rubber Metal (PRM) was studied, and comparative test with common Pseudo-Rubber Metal was carried out. The enveloped area of hysteresis curve of SMA PRM is clearly larger than that of common PRM, which indicates the damping of SMA PRM overmatches that of common PRM. The stiffness value of SMA PRM and common PRM increases with their distortion amplitude’s increase, and the stiffness value of SMA PRM is less than that of common PRM. The carrying capacity, stiffness and damping of PRM are related with its relative density. The hysteresis behavior of SMA PRM is stable and basically not related with repeating load effect. Moreover, SMA PRM damper device was studied and developed, and comparative test with common Pseudo-Rubber Metal was carried out.