As one of the main controlling factors of oil and gas accumulation,faults are closely related to the distribution of oil and gas reservoirs.Studying how faults control petroliferous basins is particularly important.In...As one of the main controlling factors of oil and gas accumulation,faults are closely related to the distribution of oil and gas reservoirs.Studying how faults control petroliferous basins is particularly important.In this work,we investigated the plane positions of major faults in the China seas and its adjacent areas using the normalized vertical derivative of the total horizontal derivative(NVDR-THDR)of the Bouguer gravity anomaly,the fusion results of gravity and magnetic anomalies,and the residual Bouguer gravity anomaly.The apparent depths of major faults in the China seas and its adjacent areas were inverted using the Tilt-Euler method based on the Bouguer gravity anomaly.The results show that the strikes of the faults in the China seas and its adjacent areas are mainly NE and NW,followed by EW,and near-SN.Among them,the lengths of most ultra-crustal faults are in the range of 1000–3000 km,and their apparent depths lie between 10 km and 40 km.The lengths of crustal faults lie between 300 km and 1000 km,and their apparent depths are between 0 km and 20 km.According to the plane positions and apparent depths of the faults,we put forward the concept of fault influence factor for the first time.Based on this factor,the key areas for oil and gas exploration were found as follows:the east of South North China Basin in the intracontinental rift basins;the southeast region of East China Sea Shelf Basin,the Taixinan and Qiongdongnan basins in the continental margin rift basins;Zhongjiannan Basin in the strike-slip pull-apart basins;the Liyue,Beikang,and the Nanweixi basins in the rifted continental basins.This work provides valuable insights into oil and gas exploration,mineral resource exploration,and deep geological structure research in the China seas and its adjacent areas.展开更多
In this study,the main properties of the hydraulic jump in an asymmetric trapezoidal flume are analyzed experimentally,including the so-called sequent depths,characteristic lengths,and efficiency.In particular,an asym...In this study,the main properties of the hydraulic jump in an asymmetric trapezoidal flume are analyzed experimentally,including the so-called sequent depths,characteristic lengths,and efficiency.In particular,an asymmetric trapezoidal flume with a length of 7 m and a width of 0.304 m is considered,with the bottom of the flume transversely inclined at an angle of m=0.296 and vertical lateral sides.The corresponding inflow Froude number is allowed to range in the interval(1.40<F1<6.11).The properties of this jump are compared to those of hydraulic jumps in channels with other types of cross-sections.A relationship for calculating hydraulic jump efficiency is proposed for the considered flume.For F1>5,the hydraulic jump is found to be more effective than that occurring in triangular and symmetric trapezoidal channels.Also,when■mes>8 and■>5,the hydraulic jump in the asymmetrical trapezoidal channel downstream of a parallelogram sluice gate is completely formed as opposed to the situation where a triangular sluice is considered.展开更多
Early on the morning of June 18,2023,far off the shore of Newfoundland,Canada,the Titan deep-sea submersible began its descent into the depths of the North Atlantic.Aboard was Titan’s inventor and pilot,Stockton Rush...Early on the morning of June 18,2023,far off the shore of Newfoundland,Canada,the Titan deep-sea submersible began its descent into the depths of the North Atlantic.Aboard was Titan’s inventor and pilot,Stockton Rush,along with four“mission specialists,”several of whom may have paid as much as 250000 USD to accompany Rush on a voyage to the site of the infamous Titanic shipwreck on the ocean floor.About two hours later.展开更多
Floating in the depths of the South China Sea,a robotic arm extending from a submersible attempts to pick up a delicate porcelain jar,directed by an archeologist.They must be careful not to even nudge another artifact...Floating in the depths of the South China Sea,a robotic arm extending from a submersible attempts to pick up a delicate porcelain jar,directed by an archeologist.They must be careful not to even nudge another artifact or disturb the seabed for fear of destroying other relics.Song Jianzhong and Dong Jiaxin,both archaeologists at the National Center for Archaeology of the National Cultural Heritage Administration of China,have participated in missions aboard a submersible to the sea bed to investigate the wrecks of two Ming Dynasty(1368-1644)vessels since 2023.展开更多
To reveal the dynamic mechanical characteristics of deep rocks,a series of impact tests under triaxial static stress states corresponding to depths of 300-2400 m were conducted.The results showed that both the strain ...To reveal the dynamic mechanical characteristics of deep rocks,a series of impact tests under triaxial static stress states corresponding to depths of 300-2400 m were conducted.The results showed that both the strain rates and the stress environments in depth significantly affect the mechanical characteristics of rocks.The sensitivity of strain rate to the dynamic strength and deformation modulus shows a negative correlation with depth,indicating that producing penetrative cracks in deep environments is more difficult when damage occurs.The dynamic strength shows a tendency to decrease and then increase slightly,but decreases sharply finally.Transmissivity demonstrates a similar trend as that of strength,whereas reflectivity indicates the opposite trend.Furthermore,two critical depths with high dynamically induced hazard possibilities based on the China Jinping Underground Laboratory(CJPL)were proposed for deep engineering.The first critical depth is 600-900 m,beyond which the sensitivity of rock dynamic characteristics to the strain rate and restraint of circumferential stress decrease,causing instability of surrounding rocks under axial stress condition.The second one lies at 1500-1800 m,where the wave impedance and dynamic strength of deep surrounding rocks drop sharply,and the dissipation energy presents a negative value.It suggests that the dynamic instability of deep surrounding rocks can be divided into dynamic load dominant and dynamic load induced types,depending on the second critical depth.展开更多
At the beginning of the Cenozoic,the atmospheric CO_(2)concentration increased rapidly from~2000 ppmv at 60 Ma to~4600 ppmv at 51 Ma,which is 5–10 times higher than the present value,and then continuous declined from...At the beginning of the Cenozoic,the atmospheric CO_(2)concentration increased rapidly from~2000 ppmv at 60 Ma to~4600 ppmv at 51 Ma,which is 5–10 times higher than the present value,and then continuous declined from~51 to 34 Ma.The cause of this phenomenon is still not well understood.In this study,we demonstrate that the initiation of Cenozoic west Pacific plate subduction,triggered by the hard collision in the Tibetan Plateau,occurred at approximately 51 Ma,coinciding with the tipping point.The water depths of the Pacific subduction zones are mostly below the carbonate compensation depths,while those of the Neo-Tethys were much shallower before the collision and caused far more carbonate subducting.Additionally,more volcanic ashes erupted from the west Pacific subduction zones,which consume CO_(2).The average annual west Pacific volvano eruption is 1.11 km~3,which is higher than previous estimations.The amount of annual CO_(2)absorbed by chemical weathering of additional west Pacific volcanic ashes could be comparable to the silicate weathering by the global river.We propose that the initiation of the western Pacific subduction controlled the long-term reduction of atmospheric CO_(2)concentration.展开更多
Netizen Comments:.Frankly speaking,the film distorts the image ofa strong female wrior into that ofa lovesick wife.The screenwriters'unimaginative and uninspired minds fail to understand the depths of this remarka...Netizen Comments:.Frankly speaking,the film distorts the image ofa strong female wrior into that ofa lovesick wife.The screenwriters'unimaginative and uninspired minds fail to understand the depths of this remarkable and noble spirit.展开更多
The time arrival structure of acoustic pulse signals propagating in ocean waveguides is of great significance for underwater acoustic communication and navigation. Using the deep-sea sound propagation data from the ex...The time arrival structure of acoustic pulse signals propagating in ocean waveguides is of great significance for underwater acoustic communication and navigation. Using the deep-sea sound propagation data from the experiments respectively conducted in the East Indian Ocean(EIO) and the South China Sea(SCS) with explosion sources near the sound channel axis(SCA), long-range transmission loss(TL) and time arrival structure of acoustic pulses for different sound speed profiles(SSPs) are compared. In the EIO environment, sound energy transmitting along the SCA is relatively large, and the corresponding signals arrive first, whereas signals propagating away from the SCA arrive late. In the full receiving depth, it shows a branch structure where the waveform near the SCA arrives earlier than other depths, which is totally different with the characteristics of the sound pulse in the SCS. Combined with the parametric mathematical model of deep-sea sound channel, the influence mechanism of SSP on the time arrival structure of long-range pulse propagation is theoretically analyzed, which well explains the phenomenon observed in the two experiments.展开更多
The area covered by this study is the county of Kakobola and its surroundings. Previous studies show that those related to the study of depths by the gravity method, using other techniques, are not always carried out ...The area covered by this study is the county of Kakobola and its surroundings. Previous studies show that those related to the study of depths by the gravity method, using other techniques, are not always carried out until now. The main goal of this article is the gravimetric characterization of our area by other approach. The interest is not only to map the lineaments and to know their dip, but also to estimate the depths of these different anomalies. The methods used for this study are the first total horizontal derivative (FTHDT), tilt angle (TA), analytical signal (AS) and horizontal gradient magnitude (HGM). The processing of the complete Bouguer anomalies (CBA) data was done mainly through software. Data analysis using the semi-finished body depth method shows depths ranging from 7.49 m to 224.6 m. Data analysis using the AS method shows values ranging from 41.7 mGal/m to 510 mGal/m. The fractures and/or geological contacts in our study area show dips ranging from -73.73° to 68.16° and North-South orientation according to the tilt angle method. The FTHDT shows several lineaments, a NE oriented fracture of Kakobola and low dip values which suggest a tabular structure of the subsurface in our study area. According to the HGM, the study area shows several preferential directions of fractures and/or geological contacts whose the most frequent directions are the NNE-SSW and WNW.展开更多
Soil aggregate stability and organic carbon（OC） are regarded as effective indicators of soil structure and quality. A longterm field experiment was established in 2006 to examine the influence of tillage systems on ...Soil aggregate stability and organic carbon（OC） are regarded as effective indicators of soil structure and quality. A longterm field experiment was established in 2006 to examine the influence of tillage systems on soil aggregation and OC in a sandy loam soil in the Huang-Huai-Hai Plain of China. The study involved eight treatments： plowing every year with（TS） and without residue（T）, plowing every 2 years with（2TS） and without residue（2T）, plowing every 4 years with（4TS） and without residue（4T）, and no plowing with（NTS） and without residue（NT）. In 2013, soil samples were collected at depths of 0–5, 5–10 and 10–20 cm, and separated into three aggregate-size classes： macroaggregates（〉250 μm）, microaggregates（53–250 μm） and the silt＋clay fraction（〈53 μm） using wet sieving method. Soil parameters measured were water-stable aggregates, geometric mean diameter（GMD）, mean weight diameter（MWD） and OC concentrations in different aggregate-size fractions and in bulk soil. The tillage treatments significantly（P〈0.05） influenced soil aggregate stability and OC distribution. Higher MWD and GMD were observed in 2TS, 4TS and NTS as compared to T. With increasing soil depth, the amount of macroaggregates and MWD and GMD values were increased, while the proportions of microaggregates and the silt＋clay fraction were declined. The OC concentrations in different aggregate fractions at all soil depths followed the order of macroaggregates〉microaggregates〉silt＋clay fraction. In the 0–5 cm soil layer, concentrations of macroaggregateassociated OC in 2TS, 4TS and NTS were 14, 56 and 83% higher than for T, whereas T had the greatest concentration of OC associated with the silt＋clay fraction in the 10–20 cm layer. Soil OC concentrations under 4TS and NTS were significantly higher（P〈0.05） than that of T in the 0–10 cm layer. Residue retention promoted formation of macroaggregates, increased macroaggregate-associated OC concentrations an展开更多
To ensure the stability of a tunnel during construction, rock bolts are usually installed, which affects the stress distribution around the tunnel. Therefore, it is necessary to study the effects of rock bolting on th...To ensure the stability of a tunnel during construction, rock bolts are usually installed, which affects the stress distribution around the tunnel. Therefore, it is necessary to study the effects of rock bolting on the stress distribution around the tunnel. In this article, the effects of rock bolting on the stress distribution around the tunnel, including the pesition and orientation of bolts, the overburden depths, and the bolt lengths, are simulated using the ANSYS software with an elnstoplastic model. The effect of multiple bolts of 2 m and 1 m lengths on the stress distribution in the roof and on the lateral sides of a tunnel and at different overburden depths is considered. An important finding is that the tensile stress region that is very dangerous for rock in the bottom of the tunnel grows rapidly with increasing overburden depths when rock bolts are installed only in the roof or on the lateral sides of a tunnel. The determination of the length of the rock bolt used around a tunnel is dependent on the loads and the integrity of the rock mass around the tunnel. In addition, rock bolting around the tunnel can obviously reduce the coefficients and the size of the region of stress concentration, especially when installed in high-stress areas. This fact is very important and essential for the design of tunnels and ensures engineering safety in tunnel engineering.展开更多
干旱导致欧洲河流干涸,多瑙河的水位降到了过去近一个世纪以来的最低水平,埋葬在多瑙河深处的十几艘德国舰船残骸露出水面。主题语境:人与社会篇幅:335词建议用时:7分钟1From the depths of the big Danube River,the huge wrecks (沉船...干旱导致欧洲河流干涸,多瑙河的水位降到了过去近一个世纪以来的最低水平,埋葬在多瑙河深处的十几艘德国舰船残骸露出水面。主题语境:人与社会篇幅:335词建议用时:7分钟1From the depths of the big Danube River,the huge wrecks (沉船) of more than a dozen German ships have risen once again,exposed by a drought that has starved Europe’s rivers and led to some of the lowest water levels of the past century.展开更多
Based on ANSYS/LS-DYNA, the dynamics analysis software, and using nonlinear dynamic finite element method, the process of a submarine pipeline impacted by dropped objects is simulated, Some conclusions are drawn： Fir...Based on ANSYS/LS-DYNA, the dynamics analysis software, and using nonlinear dynamic finite element method, the process of a submarine pipeline impacted by dropped objects is simulated, Some conclusions are drawn： First, the damage depth of suspended pipe is smaller than that of the bare pipe in case of the same fall energy, and with the increase of fall energy, the difference grows; Second, with the falling object＇s speed and mass rising, the deformation of pipeline intensifies at the impact site and the maximum vibration amplitude of submarine pipeline increases; Third, when the fall energy is equal, the smaller the contact area of falling objects and pipeline is, the greater the damage depth of pipeline becomes; Fourth, changes of seabed soil parameters （shear elastic modulus, internal friction angle, density） have less influence on the suspended pipeline＇s dent depths and maximum vibration amplitude,展开更多
Wen et al.'s method developed to obtain wind-wave frequency spectrum in deep water was used to derive the spectrum in finite depth water. The spectrum S(ω) (ω being angular frequency) when normalized with the ze...Wen et al.'s method developed to obtain wind-wave frequency spectrum in deep water was used to derive the spectrum in finite depth water. The spectrum S(ω) (ω being angular frequency) when normalized with the zeroth moment m0 and peak frequency ω0, contains in addition to the peakness factor P= ω0S(ω0)/m0, a depth parameter ω= (2πm0)1/2/d (d being water depth), so the spectrum behavior can be studied for different wave growth stages and water depths.展开更多
The 2019 M_(S)6.0 Changning earthquake occurred in the tectonically stable Sichuan Basin,where the epicenter and its adjacent areas are important shale gas and salt mine production fields,resulting in hot debates on w...The 2019 M_(S)6.0 Changning earthquake occurred in the tectonically stable Sichuan Basin,where the epicenter and its adjacent areas are important shale gas and salt mine production fields,resulting in hot debates on whether the seismogenic mechanism of the 2019 Changning earthquake is related to human activities.As source characteristics and fluid pressure can provide important constraints on whether an earthquake is induced,weinvestigate the seismogenic mechanisms of the mainshock and 9 MW≥4.0 aftershocks.In overall,the mainshock and the majority of the aftershocks are characterized by relatively shallow focal depths(1‒4 km)and significant non-double-couple(non-DC)components.However,the mainshock and the aftershocks differ in two aspects:(1)the compensated-linear-vector-dipole components dominate the non-DC components of the mainshock,whereas the isotropic components dominate the most aftershocks;(2)the fluid overpressure of the mainshock is over 30 MPa,whereas the fluid overpressure of the most aftershocks is less than 10 MPa.Thus,we propose that the mainshock is triggered by weakened fault strength with long-term fluid injection,and that its large non-DC components are associated withcomplex rupture processes.Comparatively,the aftershocks may be triggered by postseismic stress transfer by combining the Coulomb failure stress changes in the poroelastic medium.Our results highlight the possible role of fluid in the occurrence of the Changning earthquake sequence.展开更多
Objective High-pressure(HP)and ultrahigh-pressure(UHP)minerals tend to be preserved in mafic and ultramafic metamorphic rocks(e.g.eclogites and garnet amphibolite)rather than felsic rocks.Generally,HP and UHP rocks ar...Objective High-pressure(HP)and ultrahigh-pressure(UHP)minerals tend to be preserved in mafic and ultramafic metamorphic rocks(e.g.eclogites and garnet amphibolite)rather than felsic rocks.Generally,HP and UHP rocks are thought to be formed as a result of the tectonic burial or subduction of oceanic crust or thicked continental lithosphere to depths corresponding to the eclogite facies metamorphism,followed by fast uplift(Ernst et al.,2007).展开更多
基金The Scientific and Technological Project of China National Offshore Oil Corporation(CNOOC)Research Institute Co.,Ltd.,under contract No.CCL2021RCPS0167KQNthe Fundamental Research Funds for the Central Universities,CHD under contract No.300102261714。
文摘As one of the main controlling factors of oil and gas accumulation,faults are closely related to the distribution of oil and gas reservoirs.Studying how faults control petroliferous basins is particularly important.In this work,we investigated the plane positions of major faults in the China seas and its adjacent areas using the normalized vertical derivative of the total horizontal derivative(NVDR-THDR)of the Bouguer gravity anomaly,the fusion results of gravity and magnetic anomalies,and the residual Bouguer gravity anomaly.The apparent depths of major faults in the China seas and its adjacent areas were inverted using the Tilt-Euler method based on the Bouguer gravity anomaly.The results show that the strikes of the faults in the China seas and its adjacent areas are mainly NE and NW,followed by EW,and near-SN.Among them,the lengths of most ultra-crustal faults are in the range of 1000–3000 km,and their apparent depths lie between 10 km and 40 km.The lengths of crustal faults lie between 300 km and 1000 km,and their apparent depths are between 0 km and 20 km.According to the plane positions and apparent depths of the faults,we put forward the concept of fault influence factor for the first time.Based on this factor,the key areas for oil and gas exploration were found as follows:the east of South North China Basin in the intracontinental rift basins;the southeast region of East China Sea Shelf Basin,the Taixinan and Qiongdongnan basins in the continental margin rift basins;Zhongjiannan Basin in the strike-slip pull-apart basins;the Liyue,Beikang,and the Nanweixi basins in the rifted continental basins.This work provides valuable insights into oil and gas exploration,mineral resource exploration,and deep geological structure research in the China seas and its adjacent areas.
文摘In this study,the main properties of the hydraulic jump in an asymmetric trapezoidal flume are analyzed experimentally,including the so-called sequent depths,characteristic lengths,and efficiency.In particular,an asymmetric trapezoidal flume with a length of 7 m and a width of 0.304 m is considered,with the bottom of the flume transversely inclined at an angle of m=0.296 and vertical lateral sides.The corresponding inflow Froude number is allowed to range in the interval(1.40<F1<6.11).The properties of this jump are compared to those of hydraulic jumps in channels with other types of cross-sections.A relationship for calculating hydraulic jump efficiency is proposed for the considered flume.For F1>5,the hydraulic jump is found to be more effective than that occurring in triangular and symmetric trapezoidal channels.Also,when■mes>8 and■>5,the hydraulic jump in the asymmetrical trapezoidal channel downstream of a parallelogram sluice gate is completely formed as opposed to the situation where a triangular sluice is considered.
文摘Early on the morning of June 18,2023,far off the shore of Newfoundland,Canada,the Titan deep-sea submersible began its descent into the depths of the North Atlantic.Aboard was Titan’s inventor and pilot,Stockton Rush,along with four“mission specialists,”several of whom may have paid as much as 250000 USD to accompany Rush on a voyage to the site of the infamous Titanic shipwreck on the ocean floor.About two hours later.
文摘Floating in the depths of the South China Sea,a robotic arm extending from a submersible attempts to pick up a delicate porcelain jar,directed by an archeologist.They must be careful not to even nudge another artifact or disturb the seabed for fear of destroying other relics.Song Jianzhong and Dong Jiaxin,both archaeologists at the National Center for Archaeology of the National Cultural Heritage Administration of China,have participated in missions aboard a submersible to the sea bed to investigate the wrecks of two Ming Dynasty(1368-1644)vessels since 2023.
基金supported by the National Natural Science Foundation of China(No.U1965203).
文摘To reveal the dynamic mechanical characteristics of deep rocks,a series of impact tests under triaxial static stress states corresponding to depths of 300-2400 m were conducted.The results showed that both the strain rates and the stress environments in depth significantly affect the mechanical characteristics of rocks.The sensitivity of strain rate to the dynamic strength and deformation modulus shows a negative correlation with depth,indicating that producing penetrative cracks in deep environments is more difficult when damage occurs.The dynamic strength shows a tendency to decrease and then increase slightly,but decreases sharply finally.Transmissivity demonstrates a similar trend as that of strength,whereas reflectivity indicates the opposite trend.Furthermore,two critical depths with high dynamically induced hazard possibilities based on the China Jinping Underground Laboratory(CJPL)were proposed for deep engineering.The first critical depth is 600-900 m,beyond which the sensitivity of rock dynamic characteristics to the strain rate and restraint of circumferential stress decrease,causing instability of surrounding rocks under axial stress condition.The second one lies at 1500-1800 m,where the wave impedance and dynamic strength of deep surrounding rocks drop sharply,and the dissipation energy presents a negative value.It suggests that the dynamic instability of deep surrounding rocks can be divided into dynamic load dominant and dynamic load induced types,depending on the second critical depth.
基金supported by NSFC Major Research Plan on‘‘West-Pacific Earth System Multispheric Interactions’’to Prof.Weidong Sun(Grant No.92258303)AND Prof.Tianyu Chen(Grant No.91858105)。
文摘At the beginning of the Cenozoic,the atmospheric CO_(2)concentration increased rapidly from~2000 ppmv at 60 Ma to~4600 ppmv at 51 Ma,which is 5–10 times higher than the present value,and then continuous declined from~51 to 34 Ma.The cause of this phenomenon is still not well understood.In this study,we demonstrate that the initiation of Cenozoic west Pacific plate subduction,triggered by the hard collision in the Tibetan Plateau,occurred at approximately 51 Ma,coinciding with the tipping point.The water depths of the Pacific subduction zones are mostly below the carbonate compensation depths,while those of the Neo-Tethys were much shallower before the collision and caused far more carbonate subducting.Additionally,more volcanic ashes erupted from the west Pacific subduction zones,which consume CO_(2).The average annual west Pacific volvano eruption is 1.11 km~3,which is higher than previous estimations.The amount of annual CO_(2)absorbed by chemical weathering of additional west Pacific volcanic ashes could be comparable to the silicate weathering by the global river.We propose that the initiation of the western Pacific subduction controlled the long-term reduction of atmospheric CO_(2)concentration.
文摘Netizen Comments:.Frankly speaking,the film distorts the image ofa strong female wrior into that ofa lovesick wife.The screenwriters'unimaginative and uninspired minds fail to understand the depths of this remarkable and noble spirit.
基金supported by the National Natural Science Foundation of China (11874061,U22A2012)the Youth Innovation Promotion Association of Chinese Academy of Sciences (2021023)。
文摘The time arrival structure of acoustic pulse signals propagating in ocean waveguides is of great significance for underwater acoustic communication and navigation. Using the deep-sea sound propagation data from the experiments respectively conducted in the East Indian Ocean(EIO) and the South China Sea(SCS) with explosion sources near the sound channel axis(SCA), long-range transmission loss(TL) and time arrival structure of acoustic pulses for different sound speed profiles(SSPs) are compared. In the EIO environment, sound energy transmitting along the SCA is relatively large, and the corresponding signals arrive first, whereas signals propagating away from the SCA arrive late. In the full receiving depth, it shows a branch structure where the waveform near the SCA arrives earlier than other depths, which is totally different with the characteristics of the sound pulse in the SCS. Combined with the parametric mathematical model of deep-sea sound channel, the influence mechanism of SSP on the time arrival structure of long-range pulse propagation is theoretically analyzed, which well explains the phenomenon observed in the two experiments.
文摘The area covered by this study is the county of Kakobola and its surroundings. Previous studies show that those related to the study of depths by the gravity method, using other techniques, are not always carried out until now. The main goal of this article is the gravimetric characterization of our area by other approach. The interest is not only to map the lineaments and to know their dip, but also to estimate the depths of these different anomalies. The methods used for this study are the first total horizontal derivative (FTHDT), tilt angle (TA), analytical signal (AS) and horizontal gradient magnitude (HGM). The processing of the complete Bouguer anomalies (CBA) data was done mainly through software. Data analysis using the semi-finished body depth method shows depths ranging from 7.49 m to 224.6 m. Data analysis using the AS method shows values ranging from 41.7 mGal/m to 510 mGal/m. The fractures and/or geological contacts in our study area show dips ranging from -73.73° to 68.16° and North-South orientation according to the tilt angle method. The FTHDT shows several lineaments, a NE oriented fracture of Kakobola and low dip values which suggest a tabular structure of the subsurface in our study area. According to the HGM, the study area shows several preferential directions of fractures and/or geological contacts whose the most frequent directions are the NNE-SSW and WNW.
基金financially supported by the National Basic Research Program of China(2011CB100504)the Special Fund for Agro-Scientific Research in the Public Interest,China(201203030-06)the Key Program of the Chinese Academy of Sciences(CXJQ120112)
文摘Soil aggregate stability and organic carbon（OC） are regarded as effective indicators of soil structure and quality. A longterm field experiment was established in 2006 to examine the influence of tillage systems on soil aggregation and OC in a sandy loam soil in the Huang-Huai-Hai Plain of China. The study involved eight treatments： plowing every year with（TS） and without residue（T）, plowing every 2 years with（2TS） and without residue（2T）, plowing every 4 years with（4TS） and without residue（4T）, and no plowing with（NTS） and without residue（NT）. In 2013, soil samples were collected at depths of 0–5, 5–10 and 10–20 cm, and separated into three aggregate-size classes： macroaggregates（〉250 μm）, microaggregates（53–250 μm） and the silt＋clay fraction（〈53 μm） using wet sieving method. Soil parameters measured were water-stable aggregates, geometric mean diameter（GMD）, mean weight diameter（MWD） and OC concentrations in different aggregate-size fractions and in bulk soil. The tillage treatments significantly（P〈0.05） influenced soil aggregate stability and OC distribution. Higher MWD and GMD were observed in 2TS, 4TS and NTS as compared to T. With increasing soil depth, the amount of macroaggregates and MWD and GMD values were increased, while the proportions of microaggregates and the silt＋clay fraction were declined. The OC concentrations in different aggregate fractions at all soil depths followed the order of macroaggregates〉microaggregates〉silt＋clay fraction. In the 0–5 cm soil layer, concentrations of macroaggregateassociated OC in 2TS, 4TS and NTS were 14, 56 and 83% higher than for T, whereas T had the greatest concentration of OC associated with the silt＋clay fraction in the 10–20 cm layer. Soil OC concentrations under 4TS and NTS were significantly higher（P〈0.05） than that of T in the 0–10 cm layer. Residue retention promoted formation of macroaggregates, increased macroaggregate-associated OC concentrations an
文摘To ensure the stability of a tunnel during construction, rock bolts are usually installed, which affects the stress distribution around the tunnel. Therefore, it is necessary to study the effects of rock bolting on the stress distribution around the tunnel. In this article, the effects of rock bolting on the stress distribution around the tunnel, including the pesition and orientation of bolts, the overburden depths, and the bolt lengths, are simulated using the ANSYS software with an elnstoplastic model. The effect of multiple bolts of 2 m and 1 m lengths on the stress distribution in the roof and on the lateral sides of a tunnel and at different overburden depths is considered. An important finding is that the tensile stress region that is very dangerous for rock in the bottom of the tunnel grows rapidly with increasing overburden depths when rock bolts are installed only in the roof or on the lateral sides of a tunnel. The determination of the length of the rock bolt used around a tunnel is dependent on the loads and the integrity of the rock mass around the tunnel. In addition, rock bolting around the tunnel can obviously reduce the coefficients and the size of the region of stress concentration, especially when installed in high-stress areas. This fact is very important and essential for the design of tunnels and ensures engineering safety in tunnel engineering.
文摘干旱导致欧洲河流干涸,多瑙河的水位降到了过去近一个世纪以来的最低水平,埋葬在多瑙河深处的十几艘德国舰船残骸露出水面。主题语境:人与社会篇幅:335词建议用时:7分钟1From the depths of the big Danube River,the huge wrecks (沉船) of more than a dozen German ships have risen once again,exposed by a drought that has starved Europe’s rivers and led to some of the lowest water levels of the past century.
文摘Based on ANSYS/LS-DYNA, the dynamics analysis software, and using nonlinear dynamic finite element method, the process of a submarine pipeline impacted by dropped objects is simulated, Some conclusions are drawn： First, the damage depth of suspended pipe is smaller than that of the bare pipe in case of the same fall energy, and with the increase of fall energy, the difference grows; Second, with the falling object＇s speed and mass rising, the deformation of pipeline intensifies at the impact site and the maximum vibration amplitude of submarine pipeline increases; Third, when the fall energy is equal, the smaller the contact area of falling objects and pipeline is, the greater the damage depth of pipeline becomes; Fourth, changes of seabed soil parameters （shear elastic modulus, internal friction angle, density） have less influence on the suspended pipeline＇s dent depths and maximum vibration amplitude,
基金Project supported by the National Natural Science Foundation of China.
文摘Wen et al.'s method developed to obtain wind-wave frequency spectrum in deep water was used to derive the spectrum in finite depth water. The spectrum S(ω) (ω being angular frequency) when normalized with the zeroth moment m0 and peak frequency ω0, contains in addition to the peakness factor P= ω0S(ω0)/m0, a depth parameter ω= (2πm0)1/2/d (d being water depth), so the spectrum behavior can be studied for different wave growth stages and water depths.
基金supported by the high-performance computing platform TS10000 of the School of Geophysics and Geomatics,China University of Geosciences(Wuhan)supported by the National Natural Science Foundation of China(Grant Nos.42274082,42030108,41874053)Fundamental Research Funds for the Central Universities,China University of Geosciences(Wuhan)(Grant No.162301132637).
文摘The 2019 M_(S)6.0 Changning earthquake occurred in the tectonically stable Sichuan Basin,where the epicenter and its adjacent areas are important shale gas and salt mine production fields,resulting in hot debates on whether the seismogenic mechanism of the 2019 Changning earthquake is related to human activities.As source characteristics and fluid pressure can provide important constraints on whether an earthquake is induced,weinvestigate the seismogenic mechanisms of the mainshock and 9 MW≥4.0 aftershocks.In overall,the mainshock and the majority of the aftershocks are characterized by relatively shallow focal depths(1‒4 km)and significant non-double-couple(non-DC)components.However,the mainshock and the aftershocks differ in two aspects:(1)the compensated-linear-vector-dipole components dominate the non-DC components of the mainshock,whereas the isotropic components dominate the most aftershocks;(2)the fluid overpressure of the mainshock is over 30 MPa,whereas the fluid overpressure of the most aftershocks is less than 10 MPa.Thus,we propose that the mainshock is triggered by weakened fault strength with long-term fluid injection,and that its large non-DC components are associated withcomplex rupture processes.Comparatively,the aftershocks may be triggered by postseismic stress transfer by combining the Coulomb failure stress changes in the poroelastic medium.Our results highlight the possible role of fluid in the occurrence of the Changning earthquake sequence.
基金supported by the National Natural Science Foundation of China(grant No.41802234,41602229,42072267)the Fundamental Research Funds for the Central Universities,CHD(300102271207,300102279201,300102279104,300102279204)the Natural Science Foundation of Shaanxi Province,China(2019JQ-209,2019JQ-090,2019JM-312)。
文摘Objective High-pressure(HP)and ultrahigh-pressure(UHP)minerals tend to be preserved in mafic and ultramafic metamorphic rocks(e.g.eclogites and garnet amphibolite)rather than felsic rocks.Generally,HP and UHP rocks are thought to be formed as a result of the tectonic burial or subduction of oceanic crust or thicked continental lithosphere to depths corresponding to the eclogite facies metamorphism,followed by fast uplift(Ernst et al.,2007).
