Papers by Keyword: Shield

Abstract: Numerous cases on tunnel fires emphasized the importance of fire protection of tunnel lining and indicated that fire may cause severe damages to tunnel lining in term of concrete spalling, reduction of physical-mechanical characteristics and load bearing capacity. Hybrid Fiber Reinforced Concrete (HFRC) as a new type of composite building materials has excellent physical and mechanical properties. Compared with ordinary concrete, HFRC’s tensile strength, flexural strength, abrasion resistance, impact resistance, corrosion resistance, fatigue resistance, toughness and cracking resistance, antiknock properties can be increased. Due to the problems existed in the traditional shield tunnel concrete lining segment, the research of new kind of lining segment becomes an important field of the shield tunneling research. The research of hybrid fiber reinforced concrete segment is lacking in application example in China, still in starting stage. The probability for the application of the fiber reinforced concrete segment and some other related questions are discussed in the paper, and it will promote the research and the application of new lining segment in our country.

Abstract: The exact determination of emissivity and the following determination of the surface temperature of glossy materials can be carried out e. g. after applying a material with a known value of emissivity on the surface (e. g. self-adhesive foil or spray tint). The contribution deals with other possibility of determination of surface temperature and the influence of emissivity of glossy materials using a metal shield that reduces the negative influence of the reflected radiation during the termographical measurement.

Abstract: It is possible to measure the surface temperature of a peripheral wall in a certain point with an advantage when using a technical device for elimination of reflected radiation. Other advantages of the diagnostics of the peripheral wall using the infrared termographic system after removing the mentioned technical device from the wall is, that if we determine (using the technical device) the surface temperature in a determined point, then we are, after inserting it into the termographic systém, able to determine retroactively the real value of the apparent reflected temperature, and this is even done with higher accuracy. Then we use the value for a termographic measuring of all the surface of the peripheral wall, keeping the same angle of scanning.

Abstract: In order to simulate moment distribution on linings of tunnel excavated by shield, FEM-based procedure is proposed. According to geological data of tunnel excavated by shield, FEM model is performed, and the moment, axial force and shear force distributions on linings are computed. The maximum moment on segments decreases while Poisson’s ratio of soil materials touching to segments increases. The moment value and distribution vary with Young’s modulus of soil materials. The maximum positive moment on linings is approximately equal to the maximum negative moment.

Abstract: Segment floating is a common problem met in the construction of large-diameter crossing-river shield tunnel. The factors affecting segment floating are discussed first and analyzed by numerical simulation, including the properties of grouting material, the speed of shield tunneling, grouting pressure difference, the tunnel longitudinal stiffness, frictional force between segment rings and weight of the supporting system. The simulation results indicate that segment floating will reduce by shortening slurry’s initial solidification time, slowing shielding speed, improving the tunnel longitudinal stiffness as well as increasing the frictional force between segment rings. And some measures are given such as applying new rapid-setting slurries, shear pins, rubber mats with high friction coefficient and pre-stressed bolts

Abstract: With the further development of urban construction, engineering blasting has had a wide range of applications. However, its application environment has become more and more complex relatively. Underwater blasting, one of the applications of engineering blasting, has been increasingly used in construction of subsea tunnel and immersed tube in recent years though it has a complex influence on surroundings in operation. For the study of shock wave absorption technology of underwater blasting, this paper analyses the effectiveness of bubble curtain shielding technology used in the underwater explosion by field experiment. The test result shows that intensity of underwater shock wave approximately reduced by 80% after passing through the bubble curtain, which indicates that the bubble curtain can effectively reduce the shock wave pressure in water; vibration caused by shock wave in water approximately reduced by 20% after passing through the bubble curtain, which reflects propagation law of shock wave has changed due to the effect of the curtain.

Abstract: Basing on the theory of maag cylindrical diffusion, back grout diffusion radius and grouting pressure formula of shield tunnel were derived in two cases of the viscosity time-dependent behavior or not.The distribution law of diffusion radius and the pressure to segments were obtained by applicating the spreading model in some project.The results show that grout diffusion radius and grouting pressure both increase with the increasing of grouting time and grouting pressure whether considering the viscosity time-dependent behavior or not.In the same grouting time (pressure),the calculated values that unconsidering the viscosity time-dependent behavior are bigger than the values of considering.

Abstract: This paper firstly introduces the composition and mathematical description of the capacitance sensor, meanwhile, establishes the mathematical and finite element model of it. According to previous finite element model as mention above, this paper bases on FEM to compile the program and calculate the distribution of potential with shield and no shield. The program obtains result of the contour figuer of every node. Then comparing the potential value on nodes at the same place. In terms of previous analysis result, this essay amis to change electrode plate width and the length of radial shielding electrode by the order. In the meantime, it also research Potential value change in the same area and analyze the influence of potential distribution in those electrodes that were affected by the width of electrode and length of radial shielding electrode. In the end, this study obtains a lot of useful conclusions for the capacitance sensor design.

Abstract: According to the relationship of tunnel depth, the foundation forms of adjacent building (structures), the importance and the location of the tunnel in Nanjing Metro Line 3, the formation properties of the site is combined to carry out the analysis of key and difficult points on the worksite monitoring objects, the implementation methods of the interval shield monitoring is studied, which provides reference for similar engineering projects.

Abstract: Beijing subway line 6 crossing under the existing line 4 is the first domestic method of using the mined tunnels crossing under the existing interval shield tunnel, during the crossing process, the key of engineering control is the displacement of existing line and construction line. Dynamic numerical simulation for the crossing process has been made by FLAC3D, and the displacement and its change law of the existing line and construction line with the different WSS reinforcement measures are obtained.The conclusion show that the WSS reinforcement measures of upper semi-section achieves the balance of safety and economy,but the uplift of WSS to the existing line should be noted in the actual construction.