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Du H.,National University of Singapore | Du S.,China Railway 15th Bureau Group Co. | Liu X.,University of Queensland
Construction and Building Materials | Year: 2014

This study investigated the durability properties of concrete containing nano-silica at dosages of 0.3% and 0.9%, respectively. Due to the nano-filler effect and the pozzolanic reaction, the microstructure became more homogeneous and less porous, especially at the interfacial transition zone (ITZ), which led to reduced permeability. Tests on the durability properties verified the beneficial effects of nano-silica. The channels for harmful agents through the cement composites were partially filled and blocked. The pore size distribution also indicated that the large capillary pores were refined by the nano-silica, due to the combined contribution of the nano-filler effect and the pozzolanic reaction. © 2014 Elsevier Ltd. All rights reserved.


Du H.,National University of Singapore | Du S.,China Railway 15th Bureau Group Co. | Liu X.,University of Queensland
Construction and Building Materials | Year: 2015

This paper investigated the influence of nano-silica (NS) on the mechanical and transport properties of lightweight concrete (LWC). The resistance of LWC to water and chloride ions penetration was enhanced despite strength marginally increased. Water penetration depth, moisture sorptivity, chloride migration and diffusion coefficient was reduced by 23% and 49%, 23% and 10%, 5% and 0%, 22% and 12% compared to the two reference LWC mixes (pure cement and 60% slag blended cement), respectively with 1% NS. Such improvements were attributed to more compact microstructures because the micropore system was refined and the interface between aggregates and paste was enhanced. © 2015 Elsevier Ltd. All rights reserved.


Zhang G.,Tongji University | Xia C.,Tongji University | Ma X.,China Railway 15th Bureau Group Co. | Li P.,China Railway 15th Bureau Group Co. | Wei Q.,China Railway 15th Bureau Group Co.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2012

In order to prevent freezing damage of tunnels in cold region, tunnel heating system using heat pump was introduced for the first time at Linchang tunnel in Inner Mongolia Autonomous Region of China. The rock-soil thermal response test was carried out to study the influence of the inlet temperature, flow rate and pipes distance on extracted heat and the influence of heat exchange on temperature field of surrounding rock and primary lining. It can be found that the extracted heat varies with the inlet temperature linearly and with flow rate exponentially. Although the extracted heat can be improved by increasing the flow rate, there is more resistance to fluid in heat exchange pipes, it will be uneconomical if the flow rate is great; it is suggested that the flow rate is no more than 0.75 m 3/h. The affected depth of surrounding rock temperature is 75 cm when the heat exchange pipes distance is 100 cm, and is 100 cm when the heat exchange pips distance is 50 cm. The less the heat exchange pipes distance, the greater the affect depth of surrounding rock temperature and the temperature increment.


Li A.,China Railway 15th Bureau Group Co.
Modern Tunnelling Technology | Year: 2014

Water leakage is still a common and hazardous disease in cut-and-cover tunnel, though this construction method is often used in the municipal and urban rail transit constructions, and it is of great importance to assure tunnel to be waterproof. One practical project, which waterproofing construction is carried out on tunnel roof by spraying non-curing rubberized bitumen waterproof coating and pasting waterproof sheet, is studied in this paper. And sound effect of water-resistance is achieved regarding practical application of above research achievements. ©, 2015, Editorial Office of "Modern Tunnelling Technology". All right reserved.


Li A.,China Railway 15th Bureau Group Co. | Li C.,China Railway 15th Bureau Group Co. | Dong Y.,China Railway 15th Bureau Group Co.
Modern Tunnelling Technology | Year: 2014

Along the Yangtze River, it is challenging to construct a deep foundation pit due to widely distributed and thick muddy soil, a high confined water level, and complex geological conditions. In this paper, based on the Meizizhou river-crossing passage of the Nanjing YOG transportation axis project, a tri-axial soil-mixing pile retaining structure constructed using the SMW method is studied systematically. By combining data from the field piling test and the laboratory experiment, main construction technology parameters, like water cement ratio, cement content, drilling speed, and lifting speed, are determined and the displacement law of the SMW retaining structure is analyzed in light of field test results. Engineering practices show that the SMW retaining structure has a good supporting effect under the above geological conditions, and this paper provides a reference for the construction of retaining structures for large-scale, deep foundation pits. ©, 2014, Editorial Office of "Modern Tunnelling Technology". All right reserved.


Wan Y.,China Railway 15th Bureau Group Co. | Li X.,China Railway 15th Bureau Group Co.
Modern Tunnelling Technology | Year: 2014

It is difficult for the high pressure jet grouting pile under high confined water to meet the designed requirements regarding diameter and strength, and the effect of water seepage prevention is poor during construction of deep foundation pit. To prevent water seepage in foundation pit, the dual triple-tube high-pressure jet grouting piles were adopted at joints of diaphragm walls of certain project. With control of construction parameters and quality, it was found that the diameter of inner pile and strength of pile shaft fully meet the requirements of design by site test. No seepages occurred at joints of retaining structure in the process of excavation of foundation pit, which indicated that the technology of dual triple-tube high-pressure jet grouting piles is suitable for construction under such complex geological conditions as silty soil and sand, and effective to prevent water seepage at joints of retaining structure. ©, 2015, Editorial Office of "Modern Tunnelling Technology". All right reserved.


In groundwater-rich area, large-scale dewatering of deep foundation pit may result in water level lowering outside the foundation pit, cause ground surface settlement and affect the existing buildings. Combined with the construction cases and aimed at the extra-deep and extra-large foundation pit along the Yangtze River, this paper calculated the groundwater level and settlement around the foundation pit with an established model, adopted recharging technique for settlement control of adjacent buildings under long-term dewatering, and monitored their settlements by setting measuring points around the buildings. And based on the comparison of measured and theoretical results, it can be seen that the adopted recharging technique can effectively reduce the adjacent building settlement. ©, 2015, Editorial Office of "Modern Tunnelling Technology". All right reserved.


Geng H.,China Railway 15th Bureau Group Co. | Yue Q.,Qingdao Technological University
Modern Tunnelling Technology | Year: 2014

In order to improve the stability of foundation pit and facilitate excavators and workers' operations in pit, dewatering measures are needed for foundation pit with abundant groundwater. In this paper, the divisional de-watering method is put forward for the ultra deep foundation pit in floodplain area along Yangtze River, by which the dewatering divisions are determined based on site strata, groundwater conditions, design parameters for foundation pit, base slab position, and divisional dewatering is conducted by means of dewatering well for groundwater, dewatering well for confined water and relief well according to the engineering character in each division. The engineering practices indicate that the design and construction method of divisional dewatering in foundation pit are feasible and can be taken as reference for similar projects. ©, 2015, Editorial Office of "Modern Tunnelling Technology". All right reserved.


Wei J.,China Railway 15th Bureau Group Co.
Modern Tunnelling Technology | Year: 2014

As a foundation pit support structure, diaphragm wall can be used for controlling deformation and preventing leakage. However, water leakage may also occur under the complicated geological conditions. Based on a large-scale foundation pit construction, this paper summarized the common joint types of diaphragm wall, analyzed the reasons for its water leakage and gave relevant sealing measures from the view of design, construction and dynamic monitoring. And aimed at the slight and serious water leakages, two new sealing structures integrated with drainage and plugging were proposed, providing reference for similar projects. ©, 2015, Editorial Office of "Modern Tunnelling Technology". All right reserved.


Ren J.X.,Shaanxi University of Science and Technology | Ren J.X.,China Railway 15th Bureau Group Co. | Yang F.,Shaanxi University of Science and Technology | Yang F.,China Railway 15th Bureau Group Co.
Transit Development in Rock Mechanics-Recognition, Thinking and Innovation - Proceedings of the 3rd ISRM Young Scholars Symposium on Rock Mechanics, 2014 | Year: 2015

The failure mechanism of haulage gate surrounding rock in 402103 fully-mechanized topcoal caving face of some deep coal mines of Bin-Chang Mining Region in Shan-xi province are studied. The results show that haulage gate surrounding rock in deep coal mine has the characteristics of big deformation, asymmetry stress distribution of surrounding rock complex. Based on the support idea, which is first pressure released, second pressure relief, third anti-pressure, support and on-site monitoring program for haulage gate in 402103 fully-mechanized top-coal caving face is carried out. The practice shows that the design support parameters of crossheading are reasonable, and the supporting effect meets the needs of safety production. © 2015 Taylor & Francis Group, London.

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