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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.

Cao Z.,Xian Metro Ltd. Company | Yang F.,China Railway 15th Bureau Group Co. | Yang F.,Xian University of Science and Technology | Zhang N.,Xian Metro Ltd. Company | Zhang N.,Xian University of Science and Technology
Modern Tunnelling Technology | Year: 2014

Taking the construction of the Dayanta-Beichitou shield-driven tunnel on the Xi'an Metro Line 3 as an example and using the FLAC3D software, this paper studies the laws of building foundation deformation induced by shield construction in a loess area under two working conditions, provides relevant countermeasures for controlling the deformation of the Shanxi Zhenghe Hospital building and gives the monitoring scheme as well. The results show that: the soil layer around the hospital building shall be firstly reinforced by grouting to ensure that the foundation deformation keeps in the allowable value range. Practically, using appropriate excavation parameters and ground reinforcements, the shield underpasses the building safely with an allowable foundation settlement, thus proving that the above control techniques are sound and effective.

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.

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