Shanghai Institute of Geological Survey
Shanghai Institute of Geological Survey
Gu X.,Shanghai JiaoTong University |
Tao S.,Zhejiang GongShang University |
Dai B.,Shanghai Institute of Geological Survey
Urban Forestry and Urban Greening | Year: 2017
To deal with the challenges of nature conservation and public recreation in a rapidly urbanization, many big cities in China have launched country parks programs. However, seldom literature focus on the accessibilities of country parks as public infrastructure. By calculating the spatial accessibility indexes based on the Two-Step Floating Catchment Area (2SFCA) method, this paper evaluates the spatial accessibility of 14 country parks to 240 streets/towns in Shanghai. Our analysis indicates that the spatial differences of the accessibility of streets/towns are significant; the accessibility in Shanghai's central city and the Chongming Islands are lower than those of other urban areas. Based off our results, the spatial accessibility of streets/towns is far from ideal, with 85% of streets/towns having an index value less than 0.0025. Most of Shanghai's residents in streets/towns require a travel time of more than 60. min. The authors suggest that country parks cannot be replaced by urban parks in Shanghai because of their unique functionality and attraction to residents. To improve the spatial accessibility of country parks, the authors advocate for the improvement of population distribution in Shanghai and the integration of road networks and public transportation sites to country parks. Our results for Shanghai are applicable to other big cities that experienced similar rapid urbanization in China, East Asia, and Southeast Asia. © 2017 Elsevier GmbH.
Xu J.,Tongji University |
Tang Y.,Tongji University |
Yan X.,Shanghai Institute of Geological Survey |
Zhou J.,Tongji University
Marine Georesources and Geotechnology | Year: 2017
Excited by the vibration sources in dynamic engineering, the natural frequency and damping factor of the saturated marine sedimentary clay are key dynamic parameters that influence the responses under cyclic loads. Experimental and theoretical methods are proposed in this paper to analyze the natural frequency and the stress-dependent nonlinearity. The experimental method shows that the natural frequency of soils with specific stress state subjected to large cyclic shear strain can be estimated from the data of dynamic triaxial tests based on the amplitude–frequency response curve. Trial and error by the criterion from the half-power bandwidth method is used to determine the optimal fitting. The results of a theoretical study on the free vibration of soil layers are then presented to derive the analytic solution of natural frequency. In addition to the two frequency-independent elements (a lumped mass matrix and a stiffness matrix), the system’s equivalent damping coefficient matrix is iteratively determined based upon the forced vibration experimentally. Finally, the impacts of the resonance phenomenon on the dynamic shear modulus and hysteretic loop are discussed. © 2017 Taylor & Francis
Su X.-S.,Jilin University |
Lu H.,Jilin University |
Zhang W.-J.,Jilin University |
Zhang Y.-L.,Jilin University |
Jiao X.,Shanghai Institute of Geological Survey
Jilin Daxue Xuebao (Diqiu Kexue Ban)/Journal of Jilin University (Earth Science Edition) | Year: 2011
The stable isotope technique tracing the mechanism of petroleum hydrocarbon biodegradation is a newly developed and effective method in recent years. The variations of TPH, DIC and the dominant terminal electron accepters(SO4 2- and so on), δ13C and δ34S of DIC and SO4 2- have been analyzed on the basis of the geological and hydrogeological conditions of a petroleum hydrocarbon contaminated site. The results indicate that the groundwater was contaminated by petroleum hydrocarbons at various degrees and the values of electron accepters and pH increased along the groundwater flow in the central line of the plume while TPH and DIC reduced. The value of δ13C was lower than that of the uncontaminated groundwater and it decreased with DIC along the flow direction. The result of stable carbon isotope balance shows that the increase of DIC of gorundwater is mainly originated from biodegradation of petroleum hydrocarbon. Meanwhile, the values of δ34S decreased along the plume while SO4 2- increased and it can be inferred that the biodegradation of petroleum hydrocarbon with the bacterial sulfate reduction be undergone if the Rayleigh model is assumed.
Cui D.-W.,China University of Mining and Technology |
Wang Y.,China University of Mining and Technology |
Wang Y.,Shanghai Institute of Geological Survey |
Yu J.-C.,China University of Mining and Technology
Meitan Xuebao/Journal of the China Coal Society | Year: 2013
Currently the seismic exploration technique is mainly used to reveal the structure of coal beds, and cannot be used to evaluate the distribution of deformed coal, the permeability of coal beds and their roof/bottom, which are related to gas outburst. In other words, it cannot evaluate the lithology of coal beds and rock strata. In recent years, some geophysicists suggest to investigate the lithology of coal beds and rock strata, and define the deformed coal distribution and gas concentrated area with AVO technique. In this paper, a 3D seismic cube of deformed coal model was initially obtained using seismic simulation. Subsequently, AVO inversions for the 3D seismic cube were calculated using different Zoeppritz approximate equations, and many AVO attributes were obtained. Through the analysis of AVO attributes, it was proposed that the B-value cube inversed with Aki & Richards approximate equation, and the G-value cube and Δσ cube inversed with Shuey approximate equation are used as the basis of AVO interpretation. Finally, AVO inversions for real 3D coal seismic data were performed to define the distribution of deformed coal and gas concentrated areas using AVO attributes.
Yang T.-L.,Tongji University |
Yang T.-L.,Shanghai Institute of Geological Survey |
Gong S.-L.,Shanghai Institute of Geological Survey
Bulletin of Engineering Geology and the Environment | Year: 2010
The upper 75 m of the alluvium beneath Shanghai can be divided into three clay layers. Consolidation of the upper soft clay contributes to the average 3 mm/year land subsidence which occurs in the Shanghai region, despite mitigation measures including reduction in groundwater exploitation from the underlying aquifer and groundwater recharge. Data indicate that the soft clay is semi-dispersed, marginally stable, and susceptible to compaction. The study reports an analysis of the granulometric characteristics and aggregate components, pore-size distribution, microstructure, pore solution composition and cation exchangeability of the soft clay. The results indicate the deformation/consolidation of the soft clay is related to its microscopic physical and chemical characteristics rather than the fluctuation of the groundwater level in the underlying aquifer. © 2010 Springer-Verlag.
Cui Z.-D.,Tongji University |
Cui Z.-D.,Shanghai Institute of Geological Survey |
Tang Y.-Q.,Tongji University
Engineering Geology | Year: 2010
In the urban area of Shanghai, the dewatering of groundwater was controlled strictly and the engineering-environment effect of the high-rise building group became to be the main cause of land subsidence in Shanghai. Based on the high-rise building group in the soft soil area in Shanghai, the mechanism of land subsidence was studied in this paper by the centrifuge model test. The central area of the building group has larger subsidence and the subsidence superimposition effect is obvious. It can exceed the allowance and cause land subsidence hazard. The land subsidence affected by the different building distances was also studied. For smaller building distances, the subsidence superimposition effect is more obvious. The engineering characteristics of soils are controlled by the state of pore structure of soils to a great extent. The parameter of specific subsidence was put forward as a tie to analyze the relationship between land subsidence and pore structure of soils. The pore structure of each soil layer was studied by the mercury intrusion porosimetry test (MIP) and the pore distribution of each soil layer was studied by the fractal theory. There are mainly macropores in silty clay of layer no. 4, clayey soil of layer no. 8, silty sand of layer no. 7 and layer no. 9 in Shanghai. The ink-bottle effect exists in the intrusion stage in the MIP test. There are four different fractal dimensions in silty clay of layer no. 4 and clayey soil of layer no. 8 and three different fractal dimensions in silty sand of layer no. 7 and layer no. 9. © 2010 Elsevier B.V.
Wang J.,Tongji University |
Wu Y.,Tongji University |
Zhang X.,Tongji University |
Liu Y.,Tongji University |
And 2 more authors.
Journal of Hydrology | Year: 2012
Shanghai is one of the cities suffering from land subsidence in China. Land subsidence has caused serious financial losses. Thus, artificial recharge measures have been adopted to compensate the drawdown in shallow, confined aquifers and thereby control land subsidence. In this study, a multi-cycle recharge-recovery field experiment was performed to investigate the response of a shallow, confined aquifer to artificial recharge through a well. In the experiment, a series of recharge-recovery cycles with different recharge volumes and durations, with and without artificial pressure, were performed. The water levels monitored in the recharge and observation wells indicated the response of the aquifer to the multi-cycle recharge-recovery process. Meanwhile, a finite-difference method (FDM) numerical model was established, and its parameters were obtained via a reversed numerical analysis on the experimental data. The responses of the shallow, confined aquifer to the multi-cycle recharge-recovery process were simulated in detail using the model. The calculation results showed that the water level dropped significantly when the recharge ended. Moreover, the efficiency of a multi-cycle recharge was found to be higher than that of a concentrated one under the same recharge volume and time. The relationship between recharge frequency and efficiency, expressed as H=0.29498f 0.40163 and R 2=0.97264, respectively, was obtained through the FDM numerical simulation. In the recharge intervals, the optimal recharge efficiency was achieved when the water level rose to 40% of the peak. © 2012 Elsevier B.V.
Chen J.-F.,Tongji University |
Li H.-L.,Shanghai Institute of Geological Survey |
Liu J.-X.,Tongji University |
Zhou J.,Tongji University
Yantu Lixue/Rock and Soil Mechanics | Year: 2011
A large-size reinforced soil pull-out test was carried out and was simulated by particle flow code(PFC) to investigate the microscopic properties of geogrid-soil interface. The results show that the behavior of trigonometric group particles developed based on "clump" inherent in PFC is close to that of practical sand particles. The upper and lower geogrid-soil interfaces are not symmetrical such that the disturbed area of lower interface is higher than that of upper interface. Under the condition of low compactness of sand as well as low normal stress, the thickness of geogrid-soil interface decreases with increase of normal stress, exhibiting negative linear relationship.
Chen J.,Tongji University |
Zheng X.,Tongji University |
Li H.,Shanghai Institute of Geological Survey |
Zhou J.,Tongji University
Tumu Gongcheng Xuebao/China Civil Engineering Journal | Year: 2011
A numerical simulation was carried out to investigate the behaviour of a geogrid-reinforced soil retaining wall (RSW) with wrap-around facing on soft soil. Particle Flow Code (PFC), a discrete element method program, was used for simulation of the RSW with wrap-around facing while Fast Lagrangian Analysis of Continuum (FLAC), a finite difference method program, was used for simulation of the soft soil foundation. Coupling of discontinuum and continuum methods was realized through Socket I/O connection in FLAC and PFC. Microscopic analyses were performed on the deformation under the retaining wall, particle displacement field under the static load and soil stress distribution. The computed results then were calibrated with the measurements from the physical model test, indicating the coupling discontinuum-continuum method was appropriate.
Chen Y.,Shanghai Institute of Geological Survey |
He Z.,Shanghai Institute of Geological Survey |
Li B.,Shanghai Institute of Geological Survey |
Zhao B.,Shanghai Institute of Geological Survey
Jilin Daxue Xuebao (Diqiu Kexue Ban)/Journal of Jilin University (Earth Science Edition) | Year: 2013
The decrease of Yangtze River sediment discharge into the sea and the consequent impacts on the tidal flat have become a hot topic in recent years. The objective of this paper is, from the aspect of tidal creek development, to examine the morphological responses as well as its driving factor in Chongming Dongtan. We firstly interpreted tidal creeks from the aerial image acquired in 2008, and then, under the support of remote sensing and geographic information system software, various influencing factors for tidal creeks development were extracted: vegetation index and soil wetness were generated using Landsat Thematic Mapper (TM) image; the slope of topography was calculated from newly measured digital elevation data; and the isogram map of sedimentary size was produced from grain-size data on sediment samples. After doing these, zonal statistics method was used to calculate the average value of influencing factors in 22 tidal creek units. At last, Correlation/regression analysis was applied to quantify the contributions of influencing factors. The result shows that vegetation, hydrodynamic condition, sediment type are the dominant factor contributing the current distribution pattern of tidal creeks, followed by man-made projects, while topography and deposition rate are not main driving factors for the creeks evolution. The R of creek density with vegetation greenness, normalized differential vegetation index and surface sediment size are -0.9106, -0.8919 and 0.8734, respectively. From this, we can infer that the distribution pattern of tidal creeks would not have a significant alteration even if sediment discharge from the Yangtze River will decreased dramatically in the following decade.