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Feng K.,Shanghai Geotechnical Investigations and Design Institute Co. | Huang T.-Y.,Suzhou University of Science and Technology
Research of Environmental Sciences | Year: 2014

Greenhouse gas emissions (CH4 and N2O) from municipal solid waste landfills were investigated using the gas chromatography (GC)-static chamber method. The diurnal variations of CH4 and N2O emissions in three different landfill areas were monitored. In addition, greenhouse gas emissions under different conditions of landfill lifts, landfill age (4-13 a), cover soil type (80-100 cm), and gas collection systems were investigated. The rhythms of CH4 and N2O fluxes from MSW landfills were studied diurnally, and under over four selected seasons. The results showed that CH4 and N2O emissions varied substantially with landfill age and depth. Compared with the oldest landfill age (10-15 a) and the deepest depth (80-100 cm), the minimum emissions observed varied by two orders of magnitude. The landfill showed significant spatial and temporal variations, due to great natural heterogeneities. Although the diurnal and seasonal variations of CH4 and N2O fluxes in the three selected landfill sites were different from each other, the least emission fluxes were observed in spring, with the CH4 flux of 30 and N2O flux of 186.49 μg/(m2·h). CH4 and N2O fluxes were higher in summer and during the transitions of the autumn/winter and winter/spring. About 70% of the greenhouse gases were emitted in the evening. The landfill is a highly heterogeneous system. CH4 fluxes were not significantly correlated with soil temperature and soil water content during the measurement, while N2O fluxes were positively correlated with soil temperature and soil water content. The diurnal and seasonal variations of CH4 fluxes showed better stability, with variation coefficients in the range of 13% to 405% and 43% to 429% separately. There were great diurnal and seasonal variations of N2O emissions, with variation coefficients in the range of 15% to 1005% and 17% to 1552% separately. This implies that low frequency measurements are likely resulting in greatly over-or under-estimated N2O emissions. It is necessary to provide full-time monitoring and control of greenhouse gas emissions. ©, 2014, Editorial Department of Molecular Catalysis. All right reserved.


Tan Y.,Tongji University | Wang D.,Shanghai Geotechnical Investigations and Design Institute Company Ltd
Journal of Performance of Constructed Facilities | Year: 2015

Via analyzing the field instrumentation data, this study examines the structural behaviors of the multipropped diaphragm wall for excavation of the outer rectangular pit. The circumferential stresses in waler beams as well as boundary beams were closely related to the corresponding wall deflections. Braced struts might lead to stress-concentration in the retaining structures. Because of the uneven vertical movements of floor slabs, boundary beams suffered bending stresses. The stresses in interior columns were governed by the weights of cast floor slabs and rebounds of basal soils. The significant upward movements of interior columns and heavy floor slabs indicate that the released stresses due to soil removal outweighed the heavy weights of the retaining structures. The excavation-induced lateral loads against the retaining wall were mainly carried by the rigid floor slabs and concrete beams, which were up to 10 times or more those carried by the temporary propped struts. The comparison between the field data and the design analysis results shows that the theoretical beam-on-elastic-foundation design models can make a relative reasonable estimation on the wall deflections for the unpropped circular diaphragm wall, but highly underestimated the wall deflections of the multipropped rectangular diaphragm wall. The potential adverse effects resulting from structural deficiencies (e.g., openings on floor slabs for soil discharge) and pit-size effects on weakening the capabilities of cast floor slabs or braced struts to constrain wall deflection should be taken into account in design analysis of top-down excavations. © 2014 American Society of Civil Engineers.


Yu D.-H.,Tongji University | Yin J.,Shanghai Geotechnical Investigations and Design Institute Co.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2010

The composite soil nailing wall is a kind of support for foundation pits. This method has been widely used in the project practice in recent years because of its excellent behaviors and low cost. The deformation and failure mechanism of composite soil nailing wall and the method to calculate its overall stability of foundation pits in Shanghai soft clay are discussed. The FEM is introduced to analyze the displacement and overall safety of the composite soil nailing wall. A case of composite soil nailing wall is employed to validate the proposed FEM. It is suggested that the displacement and overall safety factor should be considered together.


Gao G.,Tongji University | Li N.,Shanghai Geotechnical Investigations and Design Institute Co. | Gu X.,Tongji University
Soil Dynamics and Earthquake Engineering | Year: 2015

In this paper, a series of field experiments were carried out to investigate the active vibration isolation for a surface foundation using horizontal wave impedance block (WIB) in a multilayered ground under vertical excitations. The velocity amplitude of ground vibration was measured and the root-mean-square (RMS) velocity is used to evaluate the vibration mitigation effect of the WIB. The influences of the size, the embedded depth and the shear modulus of the WIB on the vibration mitigation were also systematically examined under different loading conditions. The experimental results convincingly indicate that WIB is effective to reduce the ground vibration, especially at high excitation frequencies. The vibration mitigation effect of the WIB would be improved when its size and shear modulus increase or the embedded depth decreases. The results also showed that the WIB may amplify rather than reduce the ground vibration when its shear modulus is smaller or the embedded depth is larger than a threshold value. Meanwhile, an improved 3D semi-analytical boundary element method (BEM) combined with a thin layer method (TLM) was proposed to account for the rectangular shape of the used WIB and the laminated characteristics of the actual ground condition in analyzing the vibration mitigation of machine foundations. Comparisons between the field experiments and the numerical analyses were also made to validate the proposed BEM. © 2014 Elsevier Ltd.


Tan Y.,Tongji University | Lan H.,Shanghai Geotechnical Investigations and Design Institute Company Ltd
Journal of Performance of Constructed Facilities | Year: 2012

To ensure the safety of adjacent 16.7-m-high concrete frame structures (cooling towers) and buried pipelines in service during installation of 83 prestressed high-strength concrete (PHC) pipe piles, the behavior of the ground, the buried pipelines, and cooling towers was monitored by a comprehensive instrumentation program. The field measurements included the following: (1) time histories of the particle velocities and corresponding Fourier spectra in three mutually perpendicular directions at various pile penetration depths and (2) vertical and horizontal movements of the buried pipelines caused by pile installation. Based on the analysis of the field data, the following major findings were obtained: (1) unlike the driving of prestressed concrete piles or cast in situ piles, the vibration velocity in the vertical direction was not greater than that in the plane during PHC pipe pile driving; (2) the amplitudes of the peak particle velocities were relatively independent of the pile penetration depths because of the complex soil conditions; (3) both the ground and the concrete structure experienced primarily high-frequency vibrations, which attenuated rapidly over time; (4) during the pile driving, only slight vibration amplification was observed at the upper levels of the existing concrete frame structure as a result of the soil-structure interaction - the concrete structure had a much wider frequency band (around 0-300 Hz) than the ground (around 0-100 Hz); and (5) the method of installing the piles close to the existing facilities before installing those a distance away effectively mitigated the potential adverse effects on the buried pipelines. © 2012 American Society of Civil Engineers.


Tan Y.,Tongji University | Wang D.,Shanghai Geotechnical Investigations and Design Institute Company Ltd
Journal of Performance of Constructed Facilities | Year: 2015

The excavation of a large-sized foundation pit for one skyscraper in Shanghai required installation of a 100-m diameter unpropped circular diaphragm wall at the pit center first, followed by installation of a multipropped rectangular diaphragm wall at the periphery. Due to the limited paper length, this study just focuses on the structural behaviors of the inner circular wall and those of the outer rectangular wall will be presented in a companion paper. The circular diaphragm wall exhibited apparent spatial arching effects during excavation and only slight differences were observed in its maximum lateral movements along the circumference. Like braced struts, waler beams mainly carried the load due to soil removal in the proximity. In contrast, the circular diaphragm wall carried the hoop stresses due to soil removal throughout the excavation. The vertical bending stresses in diaphragm wall panels were symmetric about their neutral axes. Although the adopted remedial measure effectively mitigated their potential adverse effects on wall deformations, structural deficiencies (e.g., diaphragm wall panels encountered the existing long driven piles at several locations) resulted in some detrimental effects (e.g., tension stress development in concrete and uneven stress distributions in retaining structures). Throughout the construction, the stress development patterns in concrete corresponded well with those in reinforcing rebars, which indicated that the retaining structures were not overstressed. The comparisons between the design analysis results and the field measurements show that the adopted beam-on-elastic-foundation method can make relatively reasonable estimation on excavation-induced deflections of the unpropped circular retaining wall. © 2014 American Society of Civil Engineers.


Guo D.-P.,Shanghai Geotechnical Investigations and Design Institute Co.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2014

According to the design example of a foundation pit, a method for design and analysis of bracing system for the junction of basement floor No.1 and No.2 is introduced. Meanwhile, the geotechnical FEM software Z_SOIL. PC 2013 is adopted to calculate the model by using 3D numerical analysis method. The results of the numerical analysis are compared with the measured ones, indicating the feasibility of the proposed design method. Finally, some experience of the project is summarized.


Yin J.,Shanghai Geotechnical Investigations and Design Institute Co.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2010

The theoretical foundation of the hardening soil model (HSS model) with small strain stiffness is introduced. The method to determine the parameters of the HSS model is proposed. The experimental parameters of the HSS model of Shanghai soft clay are given. Two projects of deep foundation excavation in Shanghai are analyzed by use of the fluid-solid FEM. The results of numerical analysis agree with the measured data. The feasibility of the HSS model and the accuracy of the recommended parameters are validated.


Mei Z.J.,Shanghai Geotechnical Investigations and Design Institute Co.
Applied Mechanics and Materials | Year: 2013

Through the field vibration measurement of 50m and 80m deep holes under road traffic load, the attenuation law of displacement in holes with depth under traffic and traffic-free conditions was discussed in the time and frequency domains. Some conclusions were drawn as follows: RMS attenuation factor was close to 0.2 and the displacement is obviously reduced at a depth of about 40m; the peak frequency decreased as the depth gradually increased. Compared with the attenuation law in elastic half-space Rayleigh wave, it was found that the horizontal displacement reduced more slowly than the elastic half-space Rayleigh wave and the attenuation factor was gradually close to the attenuation curve of the elastic half-space Rayleigh wave with the increase of the depth; the attenuation factor of the vertical displacement gradually reduced as the depth increased and reduced much faster than elastic half-space Rayleigh wave. © (2013) Trans Tech Pudlications, Switzerland.


Xu F.,Shanghai Geotechnical Investigations and Design Institute Co.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2011

With the uncertainty of constraint condition of pile top, the lateral capacity of a single pile is hard to be evaluated precisely by theoretical computation or by routine static load tests when the horizontal earthquake action of pile foundations is checked. By investigating the calculation of the lateral capacity of a single pile of an existing building and testing through prototype tests, the lateral capacity of single pile under the constraint condition of pile top is acquired, which matches with the one under real working condition. The conclusion and methodology will be useful for the relevant calculation of lateral capacity of piles.

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