Jiangsu Key Laboratory of Urban Underground Engineering and Environmental Safety

Nanjing, China

Jiangsu Key Laboratory of Urban Underground Engineering and Environmental Safety

Nanjing, China
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Du G.,Nanjing Southeast University | Du G.,Jiangsu Key Laboratory of Urban Underground Engineering and Environmental Safety | Luo T.,Nanjing Southeast University | Luo T.,Jiangsu Key Laboratory of Urban Underground Engineering and Environmental Safety | And 3 more authors.
Dongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Southeast University (Natural Science Edition) | Year: 2017

In order to increase the accuracy of liquefaction assessment on liquefiable foundation, the liquefiable foundation of the Suqian-Xinyi highway was treated by the resonant compaction method, and piezocone penetration test (CPTU) and standard penetration test (SPT) were carried out on the liquefiable foundation. The soil behavior type index (Ic) obtained from CPTU and the standard penetration test index (N63.5) obtained from SPT are analyzed. The results show that N63.5 of saturated sands and silts is a linear function of Ic (N63.5=-18.8Ic+52.0). The larger the Ic, the smaller the N63.5 will be, and the soil is more close to clay. Based on the fitting relationship between N63.5 and Ic, a new liquefaction discrimination method is established. The liquefaction of saturated sands and silts foundation can be assessed by using N63.5 based on the Code of Seismic Design of Building. N63.5 is expressed by single Ic and Ic is acquired from CPTU. Compared with the SPT assessment method proposed in the code, this method can provide continuous standard penetration test value. Compared with the cyclic resistance ratio method based on cone penetration test, the calculation of the method is very simple. © 2017, Editorial Department of Journal of Southeast University. All right reserved.


Liu B.,Nanjing Southeast University | Liu B.,Jiangsu Key Laboratory of Urban Underground Engineering and Environmental Safety | Xi P.,State and Local Joint Engineering Laboratory of Structure Health Monitoring and Disaster prevention | Guo Y.,Anhui Institute of Building Research & Design | And 2 more authors.
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2017

In order to investigate the load transfer mechanisms and bearing behavior of soil displacement screw (SDS) pile, a field full-scale test was carried out by BOTDA-based optical fiber sensing technique through embedding optical fiber in piles to detect the pile strain distribution under loading. Then the axial force, the side friction and the tip resistance of SDS pile were also analyzed. The bearing behavior of SDS pile was also compared with that of continuous flight auger (CFA) pile constructed in the same test field. The results indicate that distributed optical fiber monitoring can conveniently obtain load transfer mechanisms of piles. The tip resistance of SDS pile is smaller than that of CFA pile under the same load applied on the pile top, and the tip resistance of SDS pile accounts for about 8% of the whole load when reaching the ultimate bearing capacity, which implies that SDS pile can be considered as friction pile or end bearing friction pile in the design. The ultimate bearing capacity of SDS pile can be increased by 67% compared with that of CFA pile with the same pile parameters and soil conditions. The positive soil compacting effect induced by drilling construction leads to the increase of stress level, which promotes the side friction and therefore improves the bearing capacity of SDS pile. © 2017, Central South University Press. All right reserved.


Zhang G.,Nanjing Southeast University | Zhang G.,Jiangsu Key Laboratory of Urban Underground Engineering and Environmental Safety | Xia C.,Tongji University | Zhao X.,Beijing University of Technology | Zhou S.,Tongji University
Applied Thermal Engineering | Year: 2016

A tunnel lining ground heat exchanger (GHE) uses surrounding rock as heat source and transfers heat through absorber pipes buried in the tunnel lining. In order to evaluate the effect of ventilation on the thermal performance of tunnel lining GHEs, thermal response field tests considering ventilation were performed in Linchang tunnel, and a 3D numerical model of tunnel lining GHEs was built and verified with the field monitoring data. The study results show that (i) the ventilation has a significant influence on the temperature field of surrounding rock; (ii) the heat exchange rate rises exponentially as convective heat transfer coefficient (CHTC) increases, and it increases significantly with the decreasing thickness of secondary lining; (iii) the heat exchange rate presents a linear variation as the inlet temperature increases, the growth gradient of the heat exchange rate rises exponentially as the CHTC increases and decreases gradually with the running time increase. © 2015 Elsevier Ltd. All rights reserved.


Zhang D.-W.,Nanjing Southeast University | Zhang D.-W.,Jiangsu Key Laboratory of Urban Underground Engineering and Environmental Safety | Cao Z.-G.,Nanjing Southeast University | Cao Z.-G.,Jiangsu Key Laboratory of Urban Underground Engineering and Environmental Safety | And 3 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2015

In order to explore the application potential of electrical resistivity method in the field of solidified heavy metal-contaminated soils, the artificial contaminated soils with five different lead contents are solidified using cement, and then their electrical resistivities and unconfined compressive strengths after various curing periods are tested. The relationship between the electrical resistivity and unconfined compressive strength is discussed. The test results show that the cement hydration reaction results in an increase of the electrical resistivity of solidified samples, but the electrical resistivity decreases with the increase of after-curing porosity, degree of saturation and lead content. A key parameter (nt·e100wPb)/ (aw·T0.5) (e is the Euler's number) is proposed to comprehensively reflect the effects of the lead content, cement hydration reaction and dense state of soils on the electrical resistivity of solidified soils. The Archie's electrical resistivity formula is extended to solidified heavy metal-contaminated soils by replacing the porosity by the key parameter. There is a power function relationship between the strength and the electrical resistivity while the lead content of solidified soils is certain. The electrical resistivity method can be used as a non-destructive, economical and continuous way to evaluate the quality of solidified heavy metal-contaminated soils. ©, 2015, Chinese Society of Civil Engineering. All right reserved.


Liu Z.-B.,Nanjing Southeast University | Liu Z.-B.,Jiangsu Key Laboratory of Urban Underground Engineering and Environmental Safety | Liu S.-Y.,Nanjing Southeast University | Liu S.-Y.,Jiangsu Key Laboratory of Urban Underground Engineering and Environmental Safety | And 5 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2015

To learn the pore pressure response characteristics of PHC pipe pile composite foundation in interactive marine and terrestrial deposit of Yangtze River Estuary, a test site is selected at the northern connection project of Chongming-Qidong Bridge, and then field tests are conducted to study the variation of pore pressure at different depths during embankment loading. At the same time, the meteorology and hydrogeololgy of the local area are investigated. The test results indicate that the water table is greatly influenced by local precipitation and seasonal fluctuations of groundwater. The variation of the water table in one year may reach 1. 6 m, which must be considered in the pore pressure analysis of foundation soils. The excessive pore pressure of shallow soils fluctuates sharply and dissipates quickly due to their good permeability. While the excessive pore pressure of deep soils may be accumulated and gradually increase owing to their low permeability and embankment loading. The excessive pore pressure in the reinforced zone of the pipe pile composite foundation is low and dissipates quickly, but that in the underlying soft layer is relatively high and dissipates slowly. Therefore, the consolidation property of the underlying soft layer in the interactive marine and terrestrial deposit of Yangtze River Estuary should be paid attention to. ©, 2015, Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering. All right reserved.


Liu S.-Y.,Jiangsu Key Laboratory of Urban Underground Engineering and Environmental Safety | Liu S.-Y.,Nanjing Southeast University | Li C.,Jiangsu Key Laboratory of Urban Underground Engineering and Environmental Safety | Li C.,Nanjing Southeast University
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2015

The carbonated deep mixing method is an innovative CO2 consuming method for ground improvement, in which the MgO binder is firstly mixed with the soft soils and then CO2 is injected for carbonating in few hours. Using the carbonated mixing method, higher soil-MgO stabilized strength can be obtained in very short time. The influence of MgO activity on the stabilization efficiency and its mechanism were studied in this paper. A typical clay from Wuhan was used as the target soil and three different activities of MgO were selected as binders for laboratory tests. The results show that the carbonated degree with different active MgO binders can be predominantly completed in 3~6 hours and reaches stability after 24 hours. There are almost the same volume expansion of about 16% during carbonating process at all MgO binders. While the MgO activity has significant influences on the efficiency of the carbonated mixing method. With the higher activity MgO binder, the higher carbonated degree and more carbonated products forming denser texture are observed. Its unconfined compressive strength after carbonating 6 hours with higher activity MgO gets to the similar strength of 28 day-cured cement-stabilized soils. The final strength with higher activity MgO carbonated mixing soils can reach 2.5 MPa, while that with much lower activity MgO is only 0.5 MPa. The carbonated MgO-stabilized soils have considerable lower pH value (9.0~9.6) than the pH value (12) of the cement-stabilized soils. ©, 2014, Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering. All right reserved.


Chen W.,Nanjing Southeast University | Chen W.,Jiangsu Key Laboratory of Urban Underground Engineering and Environmental Safety | Zhu Z.,Nanjing Southeast University | Zhu Z.,Jiangsu Key Laboratory of Urban Underground Engineering and Environmental Safety | Li L.,Hohai University
Shuili Xuebao/Journal of Hydraulic Engineering | Year: 2015

COD (Chemical Oxygen Demand) is one of the important indexes of landfill leachate. The shale is a kind of mineral with a high specific surface area, which potentially can retain the COD from leachate. Sorption experiments were conducted to compare the absorptive performance of the crushed shale with different grain size with that of, clay, ash and bentonite. The result showed that the crushed shale with the grain size of 0.075~2.0 mm displayed higher sorption rate for COD than the others. The hydraulic conductivity tests showed that the permeability of the mixes of crushed shale and clay was less than 1×10-7 cm/s, which meets the demand of the hydraulic conductivity of liner, when the ratio of the added shale was less than 10%. ©, 2015, Shuili Xuebao/Journal of Hydraulic Engineering. All right reserved.


Deng Y.,Nanjing Southeast University | Deng Y.,Jiangsu Key Laboratory of Urban Underground Engineering and Environmental Safety | Yue X.,Nanjing Southeast University | Yue X.,Jiangsu Key Laboratory of Urban Underground Engineering and Environmental Safety | And 5 more authors.
Engineering Geology | Year: 2015

Metakaolin (MK), widely used for high-performance concrete admixtures, is introduced into improving the percolation behaviors of cement-stabilized soft clays, which is a key performance when analyzing the permeability and consolidation in the grounds modified by deep mixing methods etc., the underground water seepage and the migration of pollutants in waterproof curtains by grouting methods etc. To investigate MK effect on the hydraulic conductivity of cement stabilized soils, the flexible wall permeameter was developed and mercury intrusion porosimetry (MIP) tests were performed. The results show that the addition can reduce the hydraulic conductivity 10-100 times when MK content arrives at 3% to 5%, which attributes to less total porosity and pore diameter. As the cement stabilized soils not only belong to a kind of special soils in geotechnical engineering, but also belong to cement-based reinforced materials, it is further discussed whether the unique expression of the hydraulic conductivity of these porous materials (clay, cement stabilized soils, cement pastes and concretes) existed. The results present that there is a good correlation between the hydraulic conductivity, the void ratio and median throat pore diameter for each kind of materials from clays to concretes respectively, and the hydraulic conductivity qualitatively increases with the void ratio and median throat pore diameter whatever clays, cemented soils and pastes or concretes. After several attempts, the combined variable nD502 was adopted to normalize the macro and micro characterization of porosity, and the relatively unique relation depicting the hydraulic conductivity of these materials was proposed. © 2015 Elsevier B.V.

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