Papers by Keyword: Segment

Abstract: During the construction of a cross-connection tunnel a leakage occurred causing a ground subsidence and subsequent tunnel collapse. Therefore, a water level lowering operation is necessary for the restoration work. However, lowering the water level can increase the surrounding ground stress, resulting in secondary collapse of the tunnel structure and potential stability concerns. To address this issue, a study was conducted to minimize the impact of ground stress on the tunnel segments while supporting the interior of the tunnel through the application of jet grouting to form a modified structure inside the collapsed tunnel. A test was carried out to create a stronger body that could be used with a full-sized corrugated steel pipe at a location close to the site of the accident. By combining urethane with grout at a specific spraying pressure, a tight and high-strength modified body was formed within the corrugated steel pipe without causing any damage to the section.

Abstract: To evaluate the bending performance of a steel fiber-reinforced concrete shield segment, bending testing was conducted on prism specimens and full-scale segments with 30 kg/m³ and 40 kg/m³ steel fiber. The results show that, with increasing fiber content, the ultimate and equivalent flexural strengths increase, while the flexural toughness of the prism concrete specimen increases by approximately 15%. With increasing fiber content, the flexural capacity of the shield tunnel segment increases, the peak load increases by 24%, the crack number increases, and the average crack width decreases. During bending tests, the steel fiber-reinforced concrete segment shows remarkable characteristics of strain hardening and multiple cracking. The embedded parts reduce the cross-sectional area and cause stress concentration in the mid-span; therefore, the main crack form in this region.

Abstract: This paper describes the application of loose-abrasive processes to the manufacture of 1.4 meter, off-axis aspheric, hexagonal mirror-segments. These are prototypes for the 39 m European Extremely Large Telescope (E-ELT). The application of active forces to correct the overall form of segments in the telescope, means that the overall form-accuracy achieved in polishing can be less critical than for a non-active mirror. However, it is a requirement that the base-radii and conic constants of mirror-segments are very closely matched, so that the combined image is not degraded. This means that abrasive processes have to operate with respect to an absolute rather than relative datum. Furthermore, there are stringent requirements on mid-spatial frequency defects on segment surfaces, and on edge-roll. These control stray-light, and ultimately detectability of faint astronomical targets. We describe the CNC abrasive techniques we have developed in response. We then demonstrate the success of the approach, which represents the first time ever that segments have been processed entirely in the hexagonal shape:- a milestone in loose-abrasive processing. Finally, we address up-scale for the unprecedented number of segments required for the E-ELT build-phase.

Abstract: The problems of measurement such as real length and real shape are often met in solving practical engineering problems.The method of changing plane which is used to simplify the problem is researched how to change the relative position of the geometric elements relative to the projective plane in the space. In practical applications,we need to use the method of projection to solve the real length of oblique line and the angle between the oblique line and projective plane.

Abstract: This study is intended to evaluate the feasibility of introducing a single loop-based vehicle detector in preparation for installing the device for permanent traffic volume counts by segment. Existing AVC comprises two loop sensors and one piezo sensor which are costly for installation. Should the vehicle classifications be similar within the section, reliable traffic data collection would be possible using a single-loop alone, which needs to be evaluated. For this, traffic volume and vehicle classifications collected by two AVCs within a section were analyzed with cost-benefit analysis for analyzing the feasibility of applying a single loop-based vehicle detector . As a result of comparing and analyzing the vehicle type ratio in 36 sections where two AVCs are installed respectively, 90% of the total showed the error rate 15% or less, and according to T-test and correlation analysis result, no statistical significance between two locations in vehicle type ratio was found. According to economical feasibility analysis, B/C 12.19, NPV 474.0 bil and IRR 196%. Thus, collection of vehicle type ratio from one AVC in the section and installation of a singl loop-based vehicle detector in a single section would produce more efficient and cost effective count. Further study on cost and benefit through more intensive statistical analysis would be necessary in the coming days.

Abstract: The segment is an important part of the slab caster. the designing and manufacturing of segment directly impact the quality of slab. It is necessary to research and analysis the segment. This paper analyses stress and deformation of segment. Firstly, specify the characteristic of segment structure, legitimately simplify the structure, figure out the force of every bearing box. Secondly, develop the 3-D model with SolidWorks software, then import it into ANSYS software, with which we develop the FEM model. Lastly, analysis FEM stress and deformation of FEM model, so the maximum stress and deformation is obtained. The state of stress is safe, but the stiffness is kind of insufficient. It can be improved in the designing process.

Abstract: In this paper, we study a kind of intelligent and high-accuracy flow measurement system, which is a type of venturi tube flowmeter that surpassed the international standard ISO5167. This paper analyzes the characteristics of the super-size flow measurement in the water transportation and industrial projects, and the choice for suitable flow meters. We study the practical compensation technology for discharging coefficient “C” of the international-standard-exceeding venturi tube, and puts forward water calibration method for venturi tube, and design the intelligent and high-accuracy flow metering system based on computer technology. Furthermore, this paper analyzes the calibration data of water flow, and propose the segment and compensation method for discharging coefficient “C” practically. We solved the limitations of the international-standard-exceeding venturi tubes, and effectively improved the accuracy and range of the flow measurement system.

Abstract: Combine with the practice of Kunming city first-phase subway project construction, detailedly introduce the success construction experiences of shield crossing the dense buildings in the unfavorable conditions of shallow soil covering, big gradient, curve in small radius, complex geological condition and upgrade excavation etc. in the paper. Reasonable choosing the grout of synchronization grouting and the main technical parameters of shield tunneling on supporting pressure of working chamber, tunneling speed, total thrust, cutter head torque and excavation quantity etc., and strengthen the link of secondary grouting and technology management, the amount of settlement and uplift of the ground and the buildings can be effectively controlled.

Abstract: The vibration loads will be produced between wheel and rail on the running of the high-speed Train. The vibration energy will be transferred to the ground formation through the rail, guiding bed and tunnel lining structure, thereby causing vibration between the formation and surface and environmental interference effect problems. Thus the research of related issues caused by the high-speed train vibration has the vital great significance. The train design speed of the Shiziyang shield tunnel for Guangzhou-Shenzhen-Hong Kong passenger dedicated line is up to 350km/h. In this paper the research object is located in the segment of the homogeneous formation of the Shiziyang shield tunnel. The analysis of this paper includes the dynamic response rules of the shield tunnel and formation under the single high-speed train loads and the law of the pore water pressure accumulation and dispersion under train cyclic loading.

Abstract: Tunnel lining concrete segment is the most critical and important structural member of shield tunneling. This investigation designed and produced high-performance composite concrete segment (HCCS). Some key indexes that affect the properties of segment were tested, such as impermeability, volume stability, mechanical property, etc. The results indicated that the impermeability of HCCS concrete cover was excellent and the chloride diffusion coefficient decreased one order of magnitude compared to that of the ordinary segment concrete cover, while the service-life of HCCS increased more than ten-fold. The volume stability of HCCS concrete cover and concrete structure layer were good and the better compatibility in the volume deformation of the whole structure was shown. Furthermore, the mechanical properties of concrete cover and concrete structure layer met the project requirement perfectly, ensuring the higher durability and longer service-life of HCCS effectively.