Tectonic movements in the North Slope of Biyang Depression are comparatively mild and stable, thus generating two categories of deltas. Elementary reasons for the coexistence of deltas are the existence of the palaeod...Tectonic movements in the North Slope of Biyang Depression are comparatively mild and stable, thus generating two categories of deltas. Elementary reasons for the coexistence of deltas are the existence of the palaeodrainage pattern and the effect of palaeotopography. The sedimentary facies is the most elementary factor controlling the physical property of reservoirs. The layout and spatial combination model of the sand body and faults are the major influential factors on the occurrence of hydrocarbons. Comparative study on Houzhang and Yanglou Braided Deltas as well as Zhangchang and Gucheng Meandering Deltas suggests that the hydrocarbons distribute primarily in the mouth bar subfacies and secondarily in the distal bar subfacies of the braided delta, while the oil-water and aqueous layers are mainly found in the subaquatic distributary channel. Although the sand body of the meandering delta has excellent stratification and high porosity, the thickness is far less than that of the braided delta. Therefore, the yield of hydrocarbon is relatively low. The mudstone of the delta front subfacies is a kind of source rock with a high content of organic matter. The conducting system for oil/gas migration in the North Slope is a composite one comprising faults and sand- stone reservoirs. A large amount of oil/gas from the deep depression first migrated towards the slope along the sand body which stretches and connects with the source rocks, and then redistributed along the faults in the slope. After the movement reached a standstill, the faults formed the occlusion in the up-dip direction of the sand body, generating a great quantity of fault block hydrocarbon reservoirs in the Noah Slope.展开更多
There exist many fluvio-glacial deposits in the valley of Dadu River, Southwest China, which dates back to the Pleistocene. As some of the deposits are located within the seasonal water fluctuation zone of reservoirs,...There exist many fluvio-glacial deposits in the valley of Dadu River, Southwest China, which dates back to the Pleistocene. As some of the deposits are located within the seasonal water fluctuation zone of reservoirs, the seepage of groundwater acts as one of the key factors influencing their stability. Investigation into the sediment properties and permeability is, therefore, crucial for evaluating the sediment stability. In this study, in-situ permeability and sieving tests have been carried out to determine grain size distribution, correlations of permeability and hydraulic gradients, and relations between permeability and sedimentation properties. Test results indicate that the deposits are composed mostly of sands, gravels, cobbles and boulders, and the percentage of fines is less than 5%. The sediments have high densities, low porosities and natural moisture contents. At low hydraulic gradients, the seepage velocity obeys the Darcy＇s law, while a non- Darcy permeability is observed with hydraulic gradient exceeding a certain value （about 0.5 - 0.7）. The linear permeability coefficient ranges from 0.003 to 0.009 cm/s. Seepage failure occurs above a threshold between 1.1 and 1.5. The test data fit well with the non-linear permeability equations suggested by Forchheimer and Izbash. The non-Darcy permeability proves to be in accordance with the seepage equation suggested by Izbash with the power ＇m＇ of about 0.6 - 0.7. The characteristic grain sizes of the studied deposits are found in a narrow range between 0.024 and o.o31 mm, which is much lowerthan the effective grain size （dlo）.展开更多
A study to estimate land surface movement caused by large surface excavations in sedimentary strata is presented.In stratified or jointed strata the stress relief driven movement adjacent to large excavations can be s...A study to estimate land surface movement caused by large surface excavations in sedimentary strata is presented.In stratified or jointed strata the stress relief driven movement adjacent to large excavations can be significantly larger than expected.High lateral stresses measured in Australia and other places around the world indicate that the ratio of horizontal to vertical stress has been particularly high at shallow depths.The in situ strata is in compression and during excavation,stress is relieved towards the opening causing strata movement.Large excavations such as,open cut mines or highway cuttings,can initiate an extensive horizontal slide of surface layers towards the excavation.These ground movements can be damaging to surface structures such as water storage dams and large buildings.Based on stress measurements at shallow depths in Australian coal mines the study presented here calculates and models the extent of potential ground movement along the bedding surface adjacent to large excavations and provides a new prediction tool of land movement at the excavation boundary that can benefit the geotechnical practitioners in the mining industry.展开更多
The Loess Plateau is an earthquake prone region of China, where the effects of loess deposit on ground motion were discovered during the 2008 Wenchuan earthquake(Ms8.0) and the 2013 Minxian-Zhangxian earthquake(Ms6.6)...The Loess Plateau is an earthquake prone region of China, where the effects of loess deposit on ground motion were discovered during the 2008 Wenchuan earthquake(Ms8.0) and the 2013 Minxian-Zhangxian earthquake(Ms6.6). The field investigations, observations, and analyses indicated that large number of casualties and tremendous economic losses were caused not only by collapse and damage of houses with poor seismic performance, landslides, but also amplification effects of site conditions, topography and thickness of loess deposit, on ground motion. In this paper, we chose Dazhai Village and Majiagou Village as the typical loess site affected by the two earthquakes for intensity evaluation, borehole exploration, temporary strong motion array, micro tremor survey, and numerical analysis. The aim is to explore the relations between amplification factors and site conditions in terms of topography and thickness of loess deposit. We also developed site amplification factors of ground motion for engineering design consideration at loess sites. The results showed that the amplification effects are more predominant with increase in thickness of loess deposit and slope height. The amplification mayincrease seismic intensity by 1 degree, PGA and predominant period by 2 times, respectively.展开更多
As one of the biggest marginal seas in the western Pacific margin, the South China Sea （SCS） experienced continental rifting and seafloor spreading during the Cenozoic. The northern continental margin of the SCS is ...As one of the biggest marginal seas in the western Pacific margin, the South China Sea （SCS） experienced continental rifting and seafloor spreading during the Cenozoic. The northern continental margin of the SCS is classified as a passive continental margin. However, its depositional and structural evolution remains controversial, especially in the deep slope area. The lack of data hindered the correlation between continental shelf and oceanic basin, and prevented the establishment of sequence stratigraphic frame of the whole margin. The slope basins in the mid-northern margin of SCS developed in the Cenozoic; the sediments and basin infill recorded the geological history of the continental margin and the SCS spreading. Using multi-channel seismic dataset acquired in three survey cruises during 1987 to 2004, combined with the data of ODP Leg 184 core and industrial wells, we carried out the sequence stratigraphic division and correlation of the Cenozoic in the middle-northern margin of SCS with seismic profiles and sedimentary facies. We interpreted the seismic reflection properties including continuity, amplitude, fi＇equency, reflection terminals, and 15 sequence boundaries of the Cenozoic in the study area, and correlated the well data in geological age. The depositional environment changed from river and lake, shallow bay to open-deep sea, in correspondence to tectonic events of syn-rifting, early drifting, and late drifting stages of basin evolution.展开更多
According to the characteristics of sedimentary facies and their vertical associations, sequence association of sedimentary facies can be divided into 2 types and 28 subtypes. The first type(type A)is a sedimentary se...According to the characteristics of sedimentary facies and their vertical associations, sequence association of sedimentary facies can be divided into 2 types and 28 subtypes. The first type(type A)is a sedimentary sequence without volcanic rocks, including 18 subtypes. The second type(type B)is a volcanogenic succession including 10 subtypes. Each subtype may reflect certain filling condition under certain sedimentary environment. Time and space distribution of different types of sequence associations can reflect tectonics that controlled the basin evolution, sedimentary environments and palaeogeography.展开更多
During the construction of the south caisson anchorage of Taizhou Bridge, the drainage area is located in the lower reaches of the Yangtze River and the permeability of stratums there is considerable. In order to main...During the construction of the south caisson anchorage of Taizhou Bridge, the drainage area is located in the lower reaches of the Yangtze River and the permeability of stratums there is considerable. In order to maintain progress and guarantee safety during the sinking of the caisson, water should be drained in the initial period. Subsequently, detailed information about the aquifer permeability is required to make sure that the drainage will proceed successfully, which consequently necessitates the on-site estimation of the aquifer permeability in the drainage area. Therefore, the traditional pumping test and slug test are implemented respectively on site. The comparison of computational results of these two tests indicates that they are consistent overall. Notwithstanding, as slug test can be conducted with portable facilities in a short time and the manipulation is easy and few people need to be involved, the advantages of slug test is conspicuous compared with the traditional pumping test. It could be speculated that slug test will gain a prevalent application in the measurement of aquifer permeability in the future.展开更多
Atmospheric deposition, a major pathway of metals entering into soils, plays an important role in soil environment, especially in urban regions where a large amount of pollutants are emitted into atmosphere through va...Atmospheric deposition, a major pathway of metals entering into soils, plays an important role in soil environment, especially in urban regions where a large amount of pollutants are emitted into atmosphere through various sources. In order to understand the characteristics of atmospheric deposition in urban area and its relation with natural and anthropogenic sources, a three-year study of atmospheric deposition at three typical sites, industrial zone(IN), urban residential area(RZ) and suburban forested scenic area(FA),was carried out in Nanjing, a metropolitan city in eastern China from 2005 to 2007. The bulk deposition rate and element composition of atmospheric deposition varied spatio-temporally in the urban zones of Nanjing. The concentrations of Cu, Zn, Pb and Ca in the atmospheric deposits were strongly enriched in the whole Nanjing region; however, anthropogenic pollutants in atmospheric deposits were diluted by the input of external mineral dust transported from northwestern China. Source apportionment through principal component analysis(PCA) showed that the background atmospheric deposition at the FA site was the combination of external aerosol and local emission sources. The input of long-range transported Asian dust had an important influence on the urban background deposition, especially in spring when the continental dust from the northwestern China prevailed. Marine aerosol source was observed in summer and autumn, the seasons dominated by summer monsoon in Nanjing. In contrast, the contribution of local anthropogenic emission source was constant regardless of seasons. At the RZ and IN sites, the atmospheric deposition was more significantly affected by the nearby human activities than at the FA site. In addition, different urban activities and both the winter and summer Asian monsoons had substantial impacts on the characteristics of dust deposition in urban Nanjing.展开更多
文摘Tectonic movements in the North Slope of Biyang Depression are comparatively mild and stable, thus generating two categories of deltas. Elementary reasons for the coexistence of deltas are the existence of the palaeodrainage pattern and the effect of palaeotopography. The sedimentary facies is the most elementary factor controlling the physical property of reservoirs. The layout and spatial combination model of the sand body and faults are the major influential factors on the occurrence of hydrocarbons. Comparative study on Houzhang and Yanglou Braided Deltas as well as Zhangchang and Gucheng Meandering Deltas suggests that the hydrocarbons distribute primarily in the mouth bar subfacies and secondarily in the distal bar subfacies of the braided delta, while the oil-water and aqueous layers are mainly found in the subaquatic distributary channel. Although the sand body of the meandering delta has excellent stratification and high porosity, the thickness is far less than that of the braided delta. Therefore, the yield of hydrocarbon is relatively low. The mudstone of the delta front subfacies is a kind of source rock with a high content of organic matter. The conducting system for oil/gas migration in the North Slope is a composite one comprising faults and sand- stone reservoirs. A large amount of oil/gas from the deep depression first migrated towards the slope along the sand body which stretches and connects with the source rocks, and then redistributed along the faults in the slope. After the movement reached a standstill, the faults formed the occlusion in the up-dip direction of the sand body, generating a great quantity of fault block hydrocarbon reservoirs in the Noah Slope.
基金supported by the National Natural Fundation of China (41202212)Independent Subject Foundation of SKLGP (SKLGP2012Z006)
文摘There exist many fluvio-glacial deposits in the valley of Dadu River, Southwest China, which dates back to the Pleistocene. As some of the deposits are located within the seasonal water fluctuation zone of reservoirs, the seepage of groundwater acts as one of the key factors influencing their stability. Investigation into the sediment properties and permeability is, therefore, crucial for evaluating the sediment stability. In this study, in-situ permeability and sieving tests have been carried out to determine grain size distribution, correlations of permeability and hydraulic gradients, and relations between permeability and sedimentation properties. Test results indicate that the deposits are composed mostly of sands, gravels, cobbles and boulders, and the percentage of fines is less than 5%. The sediments have high densities, low porosities and natural moisture contents. At low hydraulic gradients, the seepage velocity obeys the Darcy＇s law, while a non- Darcy permeability is observed with hydraulic gradient exceeding a certain value （about 0.5 - 0.7）. The linear permeability coefficient ranges from 0.003 to 0.009 cm/s. Seepage failure occurs above a threshold between 1.1 and 1.5. The test data fit well with the non-linear permeability equations suggested by Forchheimer and Izbash. The non-Darcy permeability proves to be in accordance with the seepage equation suggested by Izbash with the power ＇m＇ of about 0.6 - 0.7. The characteristic grain sizes of the studied deposits are found in a narrow range between 0.024 and o.o31 mm, which is much lowerthan the effective grain size （dlo）.
文摘A study to estimate land surface movement caused by large surface excavations in sedimentary strata is presented.In stratified or jointed strata the stress relief driven movement adjacent to large excavations can be significantly larger than expected.High lateral stresses measured in Australia and other places around the world indicate that the ratio of horizontal to vertical stress has been particularly high at shallow depths.The in situ strata is in compression and during excavation,stress is relieved towards the opening causing strata movement.Large excavations such as,open cut mines or highway cuttings,can initiate an extensive horizontal slide of surface layers towards the excavation.These ground movements can be damaging to surface structures such as water storage dams and large buildings.Based on stress measurements at shallow depths in Australian coal mines the study presented here calculates and models the extent of potential ground movement along the bedding surface adjacent to large excavations and provides a new prediction tool of land movement at the excavation boundary that can benefit the geotechnical practitioners in the mining industry.
基金financially supported by National Natural Science Foundation of China (No.51478444 & No.41472297)
文摘The Loess Plateau is an earthquake prone region of China, where the effects of loess deposit on ground motion were discovered during the 2008 Wenchuan earthquake(Ms8.0) and the 2013 Minxian-Zhangxian earthquake(Ms6.6). The field investigations, observations, and analyses indicated that large number of casualties and tremendous economic losses were caused not only by collapse and damage of houses with poor seismic performance, landslides, but also amplification effects of site conditions, topography and thickness of loess deposit, on ground motion. In this paper, we chose Dazhai Village and Majiagou Village as the typical loess site affected by the two earthquakes for intensity evaluation, borehole exploration, temporary strong motion array, micro tremor survey, and numerical analysis. The aim is to explore the relations between amplification factors and site conditions in terms of topography and thickness of loess deposit. We also developed site amplification factors of ground motion for engineering design consideration at loess sites. The results showed that the amplification effects are more predominant with increase in thickness of loess deposit and slope height. The amplification mayincrease seismic intensity by 1 degree, PGA and predominant period by 2 times, respectively.
基金Supported by National Basic Research Program of China (973 Program) (No. 2007CB411703)the National Natural Science Foundation of China (No. 40806023)
文摘As one of the biggest marginal seas in the western Pacific margin, the South China Sea （SCS） experienced continental rifting and seafloor spreading during the Cenozoic. The northern continental margin of the SCS is classified as a passive continental margin. However, its depositional and structural evolution remains controversial, especially in the deep slope area. The lack of data hindered the correlation between continental shelf and oceanic basin, and prevented the establishment of sequence stratigraphic frame of the whole margin. The slope basins in the mid-northern margin of SCS developed in the Cenozoic; the sediments and basin infill recorded the geological history of the continental margin and the SCS spreading. Using multi-channel seismic dataset acquired in three survey cruises during 1987 to 2004, combined with the data of ODP Leg 184 core and industrial wells, we carried out the sequence stratigraphic division and correlation of the Cenozoic in the middle-northern margin of SCS with seismic profiles and sedimentary facies. We interpreted the seismic reflection properties including continuity, amplitude, fi＇equency, reflection terminals, and 15 sequence boundaries of the Cenozoic in the study area, and correlated the well data in geological age. The depositional environment changed from river and lake, shallow bay to open-deep sea, in correspondence to tectonic events of syn-rifting, early drifting, and late drifting stages of basin evolution.
文摘According to the characteristics of sedimentary facies and their vertical associations, sequence association of sedimentary facies can be divided into 2 types and 28 subtypes. The first type(type A)is a sedimentary sequence without volcanic rocks, including 18 subtypes. The second type(type B)is a volcanogenic succession including 10 subtypes. Each subtype may reflect certain filling condition under certain sedimentary environment. Time and space distribution of different types of sequence associations can reflect tectonics that controlled the basin evolution, sedimentary environments and palaeogeography.
基金Special Fund of"333"High Level Talent Training Project of Jiangsu ProvinceNational Scienceand Technology Support Program of China ( No. 2009BAG15B02) Key Programs for Science and Technology De-velopment of Chinese Transportation Industry( No. 2008-353-332-150)
文摘During the construction of the south caisson anchorage of Taizhou Bridge, the drainage area is located in the lower reaches of the Yangtze River and the permeability of stratums there is considerable. In order to maintain progress and guarantee safety during the sinking of the caisson, water should be drained in the initial period. Subsequently, detailed information about the aquifer permeability is required to make sure that the drainage will proceed successfully, which consequently necessitates the on-site estimation of the aquifer permeability in the drainage area. Therefore, the traditional pumping test and slug test are implemented respectively on site. The comparison of computational results of these two tests indicates that they are consistent overall. Notwithstanding, as slug test can be conducted with portable facilities in a short time and the manipulation is easy and few people need to be involved, the advantages of slug test is conspicuous compared with the traditional pumping test. It could be speculated that slug test will gain a prevalent application in the measurement of aquifer permeability in the future.
基金supported by the National Natural Science Foundation of China(Nos.41130530 and 40625001)
文摘Atmospheric deposition, a major pathway of metals entering into soils, plays an important role in soil environment, especially in urban regions where a large amount of pollutants are emitted into atmosphere through various sources. In order to understand the characteristics of atmospheric deposition in urban area and its relation with natural and anthropogenic sources, a three-year study of atmospheric deposition at three typical sites, industrial zone(IN), urban residential area(RZ) and suburban forested scenic area(FA),was carried out in Nanjing, a metropolitan city in eastern China from 2005 to 2007. The bulk deposition rate and element composition of atmospheric deposition varied spatio-temporally in the urban zones of Nanjing. The concentrations of Cu, Zn, Pb and Ca in the atmospheric deposits were strongly enriched in the whole Nanjing region; however, anthropogenic pollutants in atmospheric deposits were diluted by the input of external mineral dust transported from northwestern China. Source apportionment through principal component analysis(PCA) showed that the background atmospheric deposition at the FA site was the combination of external aerosol and local emission sources. The input of long-range transported Asian dust had an important influence on the urban background deposition, especially in spring when the continental dust from the northwestern China prevailed. Marine aerosol source was observed in summer and autumn, the seasons dominated by summer monsoon in Nanjing. In contrast, the contribution of local anthropogenic emission source was constant regardless of seasons. At the RZ and IN sites, the atmospheric deposition was more significantly affected by the nearby human activities than at the FA site. In addition, different urban activities and both the winter and summer Asian monsoons had substantial impacts on the characteristics of dust deposition in urban Nanjing.
