Frame and rocking wall(FRW)structures have excellent resilient performance during earthquakes.However,the concrete at interfacial corners of rocking walls(RWs)is easily crushed due to local extreme compression during ...Frame and rocking wall(FRW)structures have excellent resilient performance during earthquakes.However,the concrete at interfacial corners of rocking walls(RWs)is easily crushed due to local extreme compression during the rocking process.An innovative RW with a curved interface is proposed to prevent interfacial corners from producing local damage,enhancing its earthquake resilient performance(ERP).The precast wall panel with a curved interface is assembled into an integral self-centering hybrid rocking wall(SCRW)by two post-tensioned unbonded prestressed tendons.Moreover,two ordinary energy dissipation steel rebars and two shear reinforcements are arranged to increase the energy dissipation capacity and lateral resistance.Two SCRW specimens and one monolithic reinforced concrete(RC)shear wall(SW)were tested under pseudo-static loading to compare the ERPs of the proposed SCRW and the SW,focusing on studying the effect of the curved interface on the SCRW.The key resilient performance of rocking effects,failure modes,and hysteretic properties of the SCRW were explored.The results show that nonlinear deformations of the SCRW are concentrated along the interface between the SCRW and the foundation,avoiding damage within the SCRW.The restoring force provided by the prestressed tendons can effectively realize self-centering capacity with small residual deformation,and the resilient performance of the SCRW is better than that of monolithic SW.In addition,the curved interface of the SCRW makes the rocking center change and move inward,partially relieving the stress concentration and crush of concrete.The rocking range of the rocking center is about 41.4%of the width of the SCRW.展开更多
Numerical studies have been conducted for low- and medium-rise rocking structures to investigate their efficiency as earthquake-resisting systems in comparison with conventional structures. Several non-linear time-his...Numerical studies have been conducted for low- and medium-rise rocking structures to investigate their efficiency as earthquake-resisting systems in comparison with conventional structures. Several non-linear time-history analyses have been performed to evaluate seismic performance of selected cases at desired ground shaking levels, based on key parameters such as total and flexural story drifts and residual deformations. The Far-field record set is selected as input ground motions and median peak values of key parameters are taken as best estimates of system response. In addition, in order to evaluate the probability of exceeding relevant damage states, analytical fragility curves have been developed based on the results of the incremental dynamic analysis procedure. Small exceedance probabilities and acceptable margins against collapse, together with minor associated damages in main structural members, can be considered as superior seismic performance for medium-rise rocking systems. Low-rise rocking systems could provide significant performance improvement over their conventional counterparts notwithstanding certain weaknesses in their seismic response.展开更多
This paper presents the results of a parametric study of self-centering seismic retrofit schemes for reinforced concrete (RC) frame buildings. The self-centering retrofit system features flag-shaped hysteresis and min...This paper presents the results of a parametric study of self-centering seismic retrofit schemes for reinforced concrete (RC) frame buildings. The self-centering retrofit system features flag-shaped hysteresis and minimal residual deformation. For comparison purpose,an alternate seismic retrofit scheme that uses a bilinear-hysteresis retrofit system such as buckling-restrained braces (BRB) is also considered in this paper. The parametric study was carried out in a single-degree-of-freedom (SDOF) system framework since a multi-story building structure may be idealized as an equivalent SDOF system and investigation of the performance of this equivalent SDOF system can provide insight into the seismic response of the multi-story building. A peak-oriented hysteresis model which can consider the strength and stiffness degradation is used to describe the hysteretic behavior of RC structures. The parametric study involves two key parameters -the strength ratio and elastic stiffness ratio between the seismic retrofit system and the original RC frame. An ensemble of 172 earthquake ground motion records scaled to the design basis earthquake in California with a probability of exceedance of 10% in 50 years was constructed for the simulation-based parametric study. The effectiveness of the two seismic retrofit schemes considered in this study is evaluated in terms of peak displacement ratio,peak acceleration ratio,energy dissipation demand ratio and residual displacement ratio between the SDOF systems with and without retrofit. It is found from this parametric study that RC structures retrofitted with the self-centering retrofit scheme (SCRS) can achieve a seismic performance level comparable to the bilinear-hysteresis retrofit scheme (BHRS) in terms of peak displacement and energy dissipation demand ratio while having negligible residual displacement after earthquake.展开更多
We developed an anisotropic effective theoretical model for modeling the elastic behavior of anisotropic carbonate reservoirs by combining the anisotropic self-consistent approximation and differential effective mediu...We developed an anisotropic effective theoretical model for modeling the elastic behavior of anisotropic carbonate reservoirs by combining the anisotropic self-consistent approximation and differential effective medium models.By analyzing the measured data from carbonate samples in the TL area,a carbonate pore-structure model for estimating the elastic parameters of carbonate rocks is proposed,which is a prerequisite in the analysis of carbonate reservoirs.A workflow for determining elastic properties of carbonate reservoirs is established in terms of the anisotropic effective theoretical model and the pore-structure model.We performed numerical experiments and compared the theoretical prediction and measured data.The result of the comparison suggests that the proposed anisotropic effective theoretical model can account for the relation between velocity and porosity in carbonate reservoirs.The model forms the basis for developing new tools for predicting and evaluating the properties of carbonate reservoirs.展开更多
Experimental methods,including mercury pressure,nuclear magnetic resonance(NMR)and core(wateroil)displacement,are used to examine the effects of high-multiple water injection(i.e.water injection with high injected por...Experimental methods,including mercury pressure,nuclear magnetic resonance(NMR)and core(wateroil)displacement,are used to examine the effects of high-multiple water injection(i.e.water injection with high injected pore volume)on rock properties,pore structure and oil displacement efficiency of an oilfield in the western South China Sea.The results show an increase in the permeability of rocks along with particle migration,an increase in the pore volume and the average pore throat radius,and enhanced heterogeneity after high-multiple water injection.Compared with normal water injection methods,a high-multiple water injection is more effective in improving the oil displacement efficiency.The degree of recovery increases faster in the early stage due to the expansion of the swept area,and the transition from oil-wet to water-wet.The degree of recovery increases less in the late stage due to various factors,including the enhancement of heterogeneity in the rocks.Considering both the economic aspect and the production limit of water flooding,it is recommended to adopt other technologies to further enhance oil recovery after 300 PV water injection.展开更多
The rock mass consists of rock blocks and structural planes,which can reduce its integrity and strength.Therefore,accurately obtaining the characteristics of the rock mass structural plane is a prerequisite for evalua...The rock mass consists of rock blocks and structural planes,which can reduce its integrity and strength.Therefore,accurately obtaining the characteristics of the rock mass structural plane is a prerequisite for evaluating stability and designing supports in underground engineering.Currently,there are no effective testing methods for the characteristic parameters of the rock mass structural plane in underground engineering.The paper presents the digital drilling technology as a new testing method of rock mass structural planes.Flawed rock specimens with cracks of varying widths and angles were used to simulate the rock mass structural planes,and the multifunctional rock mass digital drilling test system was employed to carry out the digital drilling tests.The analysis focuses on the variation laws of drilling parameters,such as drilling pressure and drilling torque,affected by the characteristics of prefabricated cracks,and clarifies the degradation mechanism of rock equivalent compressive strength.Additionally,an identification model for the characteristic parameters of rock mass structural planes during drilling is established.The test results indicate that the average difference of the characteristics of prefabricated cracks identified by the equivalent compressive strength is 2.45°and 0.82 mm,respectively.The identification model while drilling is verified to be correct due to the high identification accuracy.Based on this,a method for testing the characteristic parameters of the surrounding rock structural plane while drilling is proposed.The research offers a theoretical and methodological foundation for precise in situ identification of structural planes of the surrounding rock in underground engineering.展开更多
Rock–soil aggregate landslides(RSALs) are a common geological hazard in deeply incised valleys in southwestern China. Large-scale RSALs are widely distributed in the upper reaches of the Dadu River, Danba County, Sic...Rock–soil aggregate landslides(RSALs) are a common geological hazard in deeply incised valleys in southwestern China. Large-scale RSALs are widely distributed in the upper reaches of the Dadu River, Danba County, Sichuan Province, and are influenced by slope structure, which can be divided into open, lock, strip, and dumbbell types, as well as soil type and meso-structure, which can be classified as layered rock–soil aggregate, block-soil, and grainsoil. In this study, the evolution of four types of structures, such as layered-dumbbell, block-soil lock, banded block-soil, and block-soil open types, were analyzed by field surveys, surface and deep displacement monitoring, and Flac3 D. It was found that the Danba reach of the Dadu River showed incised valley through the evolution from wide to slow valley affected by internal and external geological processes since the Quaternary Glaciation. In the layered-dumbbell rock–soil aggregate, the main sliding pattern is multi-stage sliding at different depths. Circular sliding in the trailing edge and plane sliding along the bedrock in the front edge body occurin the block-soil-lock type aggregate. Large-scale multi-level and circular sliding over long distances occur in the banded block-soil aggregate. The blocksoil open type is stable, with only circular sliding occurring in local and shallow surfaces of the body. The monitoring and numerical simulation results further show that slope structure and regularity have diversified with RSALs. The results provide a basis for analyzing the stability mechanism of RSALs and preventing RSALs in deeply incised valleys.展开更多
Based on the analysis and comparison of soil temperature, thermal regime and permafrost table under the experimental embankment of crushed rock structures in Beiluhe, results show that crushed rock structures provide ...Based on the analysis and comparison of soil temperature, thermal regime and permafrost table under the experimental embankment of crushed rock structures in Beiluhe, results show that crushed rock structures provide an extensive cooling effect, which produces a rising permafrost table and decreasing soil temperatures. The rise of the permafrost table under the embankment ranges from an increase of 1.08 m to 1.67 m, with an average of 1.27 m from 2004 to 2007. Mean annual soil temperatures under the crushed rock layer embankment decreased significantly from 2005 to 2007, with average decreases of ?1.03 °C at the depth of 0.5 m, ?1.14 °C at the depth of 1.5 m, and ?0.5 °C at the depth of 5 m. During this period, mean annual soil temperatures under the crushed rock cover embankment showed a slight decrease at shallow depths, with an average decrease of ?0.2 °C at the depth of 0.5 m and 1.5 m, but a slight rise at the depth of 5 m. After the crushed rock structures were closed or crammed with sand, the cooling effect of the crushed rock layer embankment was greatly reduced and that of the crushed rock cover embankment was just slightly reduced.展开更多
The Jurassic coal-measure source rocks in the Junggar Basin have drawn considerable attention in recent years. In our hydrocarbon thermal simulation experiments of these rocks, we found that the dark mudstone evaluate...The Jurassic coal-measure source rocks in the Junggar Basin have drawn considerable attention in recent years. In our hydrocarbon thermal simulation experiments of these rocks, we found that the dark mudstone evaluated as good source rock, had a much lower hydrocarbon generation capacity than the coal and carbonaceous mudstone, evaluated as poor source rock. Based on this background, we performed Fourier transform infrared spectroscopy(FTIR) and combined the results of semi-open thermal simulation experiments to explore the association between the molecular structure and hydrocarbon production capacity, with the aim of obtaining a new understanding of hydrocarbon potential of Jurassic coal-measure source rocks from the perspective of molecular structure. The results indicate that coals exhibit lower condensation of aromatic structures and higher relative abundance of aliphatic structures with a higher degree of branched chaining than mudstones and carbonaceous mudstones. Apparent aromaticity(f_a), aromatic abundance parameter I, and degree of condensation(DOC) are negatively correlated with organic matter abundance. The aliphatic structural parameter H demonstrates a substantial positive correlation with organic matter abundance. Furthermore, aliphatic relative abundance factor A is associated with the type of organic matter;the better is the type of the organic matter, the larger is the A value. The combination of the molecular structures with the thermal simulation results shows that the aliphatic hydrogen enrichment of selected carbonaceous mudstone is similar to that of coal. However, the relative abundance of the aliphatic group of it is high, and the DOC of the aromatic structure is low, making the hydrocarbon generation base stronger and easier to crack. Thus, the hydrocarbon generation capacity of carbonaceous mudstone is slightly higher than that of coal. Mudstone has low H and I values, and the DOC is high, indicating that its hydrocarbon base is low, so it has low hydrocarbon generation capacity. Therefore, the molecular structure is closely associated with the hydrocarbon potential of coal-measure source rocks. When evaluating the qualities of coal-measure source rocks, the influence of molecular structure on these rocks should be considered.展开更多
The distribution of oil and gas resources in the South China Sea and adjacent areas is closely related to the structural pattern that helped to define the controlling effect of deep processes on oil-bearing basins.Ign...The distribution of oil and gas resources in the South China Sea and adjacent areas is closely related to the structural pattern that helped to define the controlling effect of deep processes on oil-bearing basins.Igneous rocks can record important information from deep processes.Deep structures such as faults,basin uplift and depression,Cenozoic basement and magnetic basement are all the results of energy exchange within the earth.The study of the relationship between igneous rocks and deep structures is of great significance for the study of the South China Sea.By using the minimum curvature potential field separation technique and the correlation analysis technique of gravitational and magnetic anomalies,the fusion of gravitational and magnetic data reflecting igneous rocks can be obtained,through which the igneous rocks with high susceptibility/high density or high susceptibility/low density can be identified.In this study area,igneous rocks do not develop in the Yinggehai basin,Qiongdongnan basin,Zengmu basin and Brunei-Sabah basin whilst igneous rocks with high susceptibility/high density or high susceptibility/low density are widely-developed in other basins.In undeveloped igneous areas,faults are also undeveloped the Cenozoic thickness is greater,the magnetic basement depth is greater and the Cenozoic thickness is highly positively correlated with the magnetic basement depth.In igneously developed regions,the distribution pattern of the Qiongtai block is mainly controlled by primary faults,while the distribution of the Zhongxisha block,Xunta block and Yongshu-Taiping block is mainly controlled by secondary faults,the Cenozoic thickness having a low correlation with the depth of the magnetic basement.展开更多
Through the description of the deformational features of the surrounding rockaround high stress engineering soft rock roadways,the coupling stabilization principle ofinner and outer structures in surrounding rock was ...Through the description of the deformational features of the surrounding rockaround high stress engineering soft rock roadways,the coupling stabilization principle ofinner and outer structures in surrounding rock was put forward.The supporting principlesof high stress engineering soft rock roadway (high resistance and yielding support,timelysupport,high strength and high stiffness supports) were proposed,which were applied inengineering practices,and obtained better achievements.展开更多
Rock mechanics projects, excavations and rock mass monitoring are day-by-day concerns of professionals and scientists of rock engineer. Technological advances observed in the 20 and 21 centuries provided high precisio...Rock mechanics projects, excavations and rock mass monitoring are day-by-day concerns of professionals and scientists of rock engineer. Technological advances observed in the 20 and 21 centuries provided high precision equipment capable of establishing deformation and estimating the rock mass stress remotely and in real time. In addition, in order to confirm and study the data obtained with theses equipment, numerical programs of modeling became more accessible to schools, research centers and private companies. Monitoring an excavation requires, besides understanding fully the rock structure, precise definitions and goals: why, how, where. This article discusses concepts of monitoring, modeling and calibration, as well as presents examples of applications where these questions were successfully answered.展开更多
Rock slopes with large intersection angles between the strikes of strata and surface(RS-LISS)represent a unique type of layered rock slope.These slopes are usually considered to be well stabilized and less prone to la...Rock slopes with large intersection angles between the strikes of strata and surface(RS-LISS)represent a unique type of layered rock slope.These slopes are usually considered to be well stabilized and less prone to landslides.However,when such slopes contain a significant number of discontinuities,their stability is greatly weakened.This study provided innovative insights into the stability of RS-LISS and conducted an in-depth investigation of their step-path failure mechanisms.The Riyi landslide on the eastern margin of the Qinghai-Tibet Plateau,China,was taken as a typical case and detailed investigations of geological structure and deformation characteristics of the slope were conducted by means of slope mapping,core drilling,and exploratory adits.A large number of steep-dip and gentle-dip joints were discovered in the slope,along with several critical discontinuities such as faults.Analysis shows that the tectonic stresses and river downcutting over geological time played significant roles in the formation of these discontinuities.Based on the investigation results,a numerical model of DFN for the Riyi landslide was developed.The simulation results indicated that the slope could develop a sliding surface characterized by a steep back and a gentle base,formed through the stepped interconnection of various discontinuities.Additionally,the deformation of the rock mass mainly originated from the major fault,progressively extending downward.The sliding mass may slide suddenly as a whole along the stepped bottom surface,with the compressional fracture zones as lateral boundaries,presenting a"drawer-like"movement towards the free surface.展开更多
Large-scale and heavily jointed rocks have inherent planes of anisotropy and secondary structural planes,such as dominant joint sets and random fractures,which result in significant differences in their failure mechan...Large-scale and heavily jointed rocks have inherent planes of anisotropy and secondary structural planes,such as dominant joint sets and random fractures,which result in significant differences in their failure mechanism and deformation behavior compared to other rock types.To address this issue,inherent anisotropic rocks with large-scale and dense joints are considered to be composed of the rock matrix,inherent planes of anisotropy,and secondary structural planes.Then a new implicit continuum model called LayerDFN is developed based on the crack tensor and damage tensor theories to characterize the mechanical properties of inherent anisotropic rocks.Furthermore,the LayerDFN model is implemented in the FLAC3D software,and a series of numerical results for typical example problems is compared with those obtained from the 3DEC,the analytical solutions,similar classical models,laboratory uniaxial compression tests,and field rigid bearing plate tests.The results demonstrate that the LayerDFN model can effectively capture the anisotropic mechanical properties of inherent anisotropic rocks,and can quantitatively characterize the damaging effect of the secondary structural planes.Overall,the numerical method based on the LayerDFN model provides a comprehensive and reliable approach for describing and analyzing the behavior of inherent anisotropic rocks,which will provide valuable insights for engineering design and decision-making processes.展开更多
The most of high/ultrahigh-pressure(HP/UHP)terranes of the world are characterized by the occurrence of numerous pods,lenses or layered blocks of eclogite and amphibolites(e.g.O’Brien,1997;Elvevold and Gilotti,2000;Z...The most of high/ultrahigh-pressure(HP/UHP)terranes of the world are characterized by the occurrence of numerous pods,lenses or layered blocks of eclogite and amphibolites(e.g.O’Brien,1997;Elvevold and Gilotti,2000;Zhang et al.,2003;and references there in).Field and petrological features suggest that amphibolites should展开更多
This study comprehensively uses various methods such as production dynamic analysis,fluid inclusion thermometry and carbon-oxygen isotopic compositions testing,based on outcrop,core,well-logging,3D seismic,geochemistr...This study comprehensively uses various methods such as production dynamic analysis,fluid inclusion thermometry and carbon-oxygen isotopic compositions testing,based on outcrop,core,well-logging,3D seismic,geochemistry experiment and production test data,to systematically explore the control mechanisms of structure and fluid on the scale,quality,effectiveness and connectivity of ultra-deep fault-controlled carbonate fractured-vuggy reservoirs in the Tarim Basin.The results show that reservoir scale is influenced by strike-slip fault scale,structural position,and mechanical stratigraphy.Larger faults tend to correspond to larger reservoir scales.The reservoir scale of contractional overlaps is larger than that of extensional overlaps,while pure strike-slip segments are small.The reservoir scale is enhanced at fault intersection,bend,and tip segments.Vertically,the heterogeneity of reservoir development is controlled by mechanical stratigraphy,with strata of higher brittleness indices being more conducive to the development of fractured-vuggy reservoirs.Multiple phases of strike-slip fault activity and fluid alterations contribute to fractured-vuggy reservoir effectiveness evolution and heterogeneity.Meteoric water activity during the Late Caledonian to Early Hercynian period was the primary phase of fractured-vuggy reservoir formation.Hydrothermal activity in the Late Hercynian period further intensified the heterogeneity of effective reservoir space distribution.The study also reveals that fractured-vuggy reservoir connectivity is influenced by strike-slip fault structural position and present in-situ stress field.The reservoir connectivity of extensional overlaps is larger than that of pure strike-slip segments,while contractional overlaps show worse reservoir connectivity.Additionally,fractured-vuggy reservoirs controlled by strike-slip faults that are nearly parallel to the present in-situ stress direction exhibit excellent connectivity.Overall,high-quality reservoirs are distributed at the fault intersection of extensional overlaps,the central zones of contractional overlaps,pinnate fault zones at intersection,bend,and tip segments of pure strike-slip segments.Vertically,they are concentrated in mechanical stratigraphy with high brittleness indices.展开更多
Significant exploration progress has been made in ultra-deep clastic rocks in the Kuqa Depression,Tarim Basin,over recent years.A new round of comprehensive geological research has formed four new understandings:(1)Es...Significant exploration progress has been made in ultra-deep clastic rocks in the Kuqa Depression,Tarim Basin,over recent years.A new round of comprehensive geological research has formed four new understandings:(1)Establish structural model consisting of multi-detachment composite,multi-stage structural superposition and multi-layer deformation.Multi-stage structural traps are overlapped vertically,and a series of structural traps are discovered in underlying ultra-deep layers.(2)Five sets of high-quality large-scale source rocks of three types of organic phases are developed in the Triassic and Jurassic systems,and forming a good combination of source-reservoir-cap rocks in ultra-deep layers with three sets of large-scale regional reservoir and cap rocks.(3)The formation of large oil and gas fields is controlled by four factors which are source,reservoir,cap rocks and fault.Based on the spatial configuration relationship of these four factors,a new three-dimensional reservoir formation model for ultra-deep clastic rocks in the Kuqa Depression has been established.(4)The next key exploration fields for ultra-deep clastic rocks in the Kuqa Depression include conventional and unconventional oil and gas.The conventional oil and gas fields include the deep multi-layer oil-gas accumulation zone in Kelasu,tight sandstone gas of Jurassic Ahe Formation in the northern structural zone,multi-target layer lithological oil and gas reservoirs in Zhongqiu–Dina structural zone,lithologic-stratigraphic and buried hill composite reservoirs in south slope and other favorable areas.Unconventional oil and gas fields include deep coal rock gas of Jurassic Kezilenuer and Yangxia formations,Triassic Tariqike Formation and Middle-Lower Jurassic and Upper Triassic continental shale gas.The achievements have important reference significance for enriching the theory of ultra-deep clastic rock oil and gas exploration and guiding the future oil and gas exploration deployment.展开更多
The Ordovician carbonate rocks of the Yingshan formation in the Tarim Basin have a complex pore structure owing to diagenetic and secondary structures. Seismic elastic parameters（e.g., wave velocity） depend on poros...The Ordovician carbonate rocks of the Yingshan formation in the Tarim Basin have a complex pore structure owing to diagenetic and secondary structures. Seismic elastic parameters（e.g., wave velocity） depend on porosity and pore structure. We estimated the average specific surface, average pore-throat radius, pore roundness, and average aspect ratio of carbonate rocks from the Tazhong area. High P-wave velocity samples have small average specific surface, small average pore-throat radius, and large average aspect ratio. Differences in the pore structure of dense carbonate samples lead to fluid-related velocity variability. However, the relation between velocity dispersion and average specific surface, or the average aspect ratio, is not linear. For large or small average specific surface, the pore structure of the rock samples becomes uniform, which weakens squirt fl ow and minimizes the residuals of ultrasonic data and predictions with the Gassmann equation. When rigid dissolved（casting mold） pores coexist with less rigid microcracks, there are significant P-wave velocity differences between measurements and predictions.展开更多
With a more complex pore structure system compared with clastic rocks, carbonate rocks have not yet been well described by existing conventional rock physical models concerning the pore structure vagary as well as the...With a more complex pore structure system compared with clastic rocks, carbonate rocks have not yet been well described by existing conventional rock physical models concerning the pore structure vagary as well as the influence on elastic rock properties. We start with a discussion and an analysis about carbonate rock pore structure utilizing rock slices. Then, given appropriate assumptions, we introduce a new approach to modeling carbonate rocks and construct a pore structure algorithm to identify pore structure mutation with a basis on the Gassmann equation and the Eshelby-Walsh ellipsoid inclusion crack theory. Finally, we compute a single well＇s porosity using this new approach with full wave log data and make a comparison with the predicted result of traditional method and simultaneously invert for reservoir parameters. The study results reveal that the rock pore structure can significantly influence the rocks＇ elastic properties and the predicted porosity error of the new modeling approach is merely 0.74%. Therefore, the approach we introduce can effectively decrease the predicted error of reservoir parameters.展开更多
In Northern China, sandstone-type uranium （U） deposits are mostly developed in Mesozoic-Cenozoic basins. These U deposits are usually hosted in unvarying horizons within the basins and exhibit typical U-forming sedi...In Northern China, sandstone-type uranium （U） deposits are mostly developed in Mesozoic-Cenozoic basins. These U deposits are usually hosted in unvarying horizons within the basins and exhibit typical U-forming sedimentary associations, which is referred to as U-bearing rock series. This study describes the structural features of U-bearing rock series within the main Mesozoic-Cenozoic U-producing continental basins in Kazakhstan, Uzbekistan, and Russia in the western segment of the Central Asian Metallogenic Belt （CAMB）, and Northern China in the eastern segment of the CAMB. We analyze the basic structural conditions and sedimentary environments of U-bearing rock series in Northern China and classify their structural styles in typical basins into river valley, basin margin, and intrabasin uplift margin types. The intrabasin uplift margin structural style proposed in this study can be used to indicate directions for the exploration of sandstone-type U deposits hosted in the center of a basin. At the same time, the study of structural style provides a new idea for exploring sandstone-type U deposits in Mesozoic-Cenozoic basins and it is of great significance to prospecting of sandstone-type uranium deposits.展开更多
基金National Key Research and Development Program of China under Grant No.2018YFC0705602。
文摘Frame and rocking wall(FRW)structures have excellent resilient performance during earthquakes.However,the concrete at interfacial corners of rocking walls(RWs)is easily crushed due to local extreme compression during the rocking process.An innovative RW with a curved interface is proposed to prevent interfacial corners from producing local damage,enhancing its earthquake resilient performance(ERP).The precast wall panel with a curved interface is assembled into an integral self-centering hybrid rocking wall(SCRW)by two post-tensioned unbonded prestressed tendons.Moreover,two ordinary energy dissipation steel rebars and two shear reinforcements are arranged to increase the energy dissipation capacity and lateral resistance.Two SCRW specimens and one monolithic reinforced concrete(RC)shear wall(SW)were tested under pseudo-static loading to compare the ERPs of the proposed SCRW and the SW,focusing on studying the effect of the curved interface on the SCRW.The key resilient performance of rocking effects,failure modes,and hysteretic properties of the SCRW were explored.The results show that nonlinear deformations of the SCRW are concentrated along the interface between the SCRW and the foundation,avoiding damage within the SCRW.The restoring force provided by the prestressed tendons can effectively realize self-centering capacity with small residual deformation,and the resilient performance of the SCRW is better than that of monolithic SW.In addition,the curved interface of the SCRW makes the rocking center change and move inward,partially relieving the stress concentration and crush of concrete.The rocking range of the rocking center is about 41.4%of the width of the SCRW.
基金International Institute of Earthquake Engineering and Seismology(IIEES)under the research project No.7143
文摘Numerical studies have been conducted for low- and medium-rise rocking structures to investigate their efficiency as earthquake-resisting systems in comparison with conventional structures. Several non-linear time-history analyses have been performed to evaluate seismic performance of selected cases at desired ground shaking levels, based on key parameters such as total and flexural story drifts and residual deformations. The Far-field record set is selected as input ground motions and median peak values of key parameters are taken as best estimates of system response. In addition, in order to evaluate the probability of exceeding relevant damage states, analytical fragility curves have been developed based on the results of the incremental dynamic analysis procedure. Small exceedance probabilities and acceptable margins against collapse, together with minor associated damages in main structural members, can be considered as superior seismic performance for medium-rise rocking systems. Low-rise rocking systems could provide significant performance improvement over their conventional counterparts notwithstanding certain weaknesses in their seismic response.
基金Univeristy of Maryland,Start-up Grant to the First Author
文摘This paper presents the results of a parametric study of self-centering seismic retrofit schemes for reinforced concrete (RC) frame buildings. The self-centering retrofit system features flag-shaped hysteresis and minimal residual deformation. For comparison purpose,an alternate seismic retrofit scheme that uses a bilinear-hysteresis retrofit system such as buckling-restrained braces (BRB) is also considered in this paper. The parametric study was carried out in a single-degree-of-freedom (SDOF) system framework since a multi-story building structure may be idealized as an equivalent SDOF system and investigation of the performance of this equivalent SDOF system can provide insight into the seismic response of the multi-story building. A peak-oriented hysteresis model which can consider the strength and stiffness degradation is used to describe the hysteretic behavior of RC structures. The parametric study involves two key parameters -the strength ratio and elastic stiffness ratio between the seismic retrofit system and the original RC frame. An ensemble of 172 earthquake ground motion records scaled to the design basis earthquake in California with a probability of exceedance of 10% in 50 years was constructed for the simulation-based parametric study. The effectiveness of the two seismic retrofit schemes considered in this study is evaluated in terms of peak displacement ratio,peak acceleration ratio,energy dissipation demand ratio and residual displacement ratio between the SDOF systems with and without retrofit. It is found from this parametric study that RC structures retrofitted with the self-centering retrofit scheme (SCRS) can achieve a seismic performance level comparable to the bilinear-hysteresis retrofit scheme (BHRS) in terms of peak displacement and energy dissipation demand ratio while having negligible residual displacement after earthquake.
基金supported by the National Natural Science Foundation of China(No.41274136)
文摘We developed an anisotropic effective theoretical model for modeling the elastic behavior of anisotropic carbonate reservoirs by combining the anisotropic self-consistent approximation and differential effective medium models.By analyzing the measured data from carbonate samples in the TL area,a carbonate pore-structure model for estimating the elastic parameters of carbonate rocks is proposed,which is a prerequisite in the analysis of carbonate reservoirs.A workflow for determining elastic properties of carbonate reservoirs is established in terms of the anisotropic effective theoretical model and the pore-structure model.We performed numerical experiments and compared the theoretical prediction and measured data.The result of the comparison suggests that the proposed anisotropic effective theoretical model can account for the relation between velocity and porosity in carbonate reservoirs.The model forms the basis for developing new tools for predicting and evaluating the properties of carbonate reservoirs.
文摘Experimental methods,including mercury pressure,nuclear magnetic resonance(NMR)and core(wateroil)displacement,are used to examine the effects of high-multiple water injection(i.e.water injection with high injected pore volume)on rock properties,pore structure and oil displacement efficiency of an oilfield in the western South China Sea.The results show an increase in the permeability of rocks along with particle migration,an increase in the pore volume and the average pore throat radius,and enhanced heterogeneity after high-multiple water injection.Compared with normal water injection methods,a high-multiple water injection is more effective in improving the oil displacement efficiency.The degree of recovery increases faster in the early stage due to the expansion of the swept area,and the transition from oil-wet to water-wet.The degree of recovery increases less in the late stage due to various factors,including the enhancement of heterogeneity in the rocks.Considering both the economic aspect and the production limit of water flooding,it is recommended to adopt other technologies to further enhance oil recovery after 300 PV water injection.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFC2907600)the National Natural Science Foundation of China(Grant Nos.42277174 and 52204260).
文摘The rock mass consists of rock blocks and structural planes,which can reduce its integrity and strength.Therefore,accurately obtaining the characteristics of the rock mass structural plane is a prerequisite for evaluating stability and designing supports in underground engineering.Currently,there are no effective testing methods for the characteristic parameters of the rock mass structural plane in underground engineering.The paper presents the digital drilling technology as a new testing method of rock mass structural planes.Flawed rock specimens with cracks of varying widths and angles were used to simulate the rock mass structural planes,and the multifunctional rock mass digital drilling test system was employed to carry out the digital drilling tests.The analysis focuses on the variation laws of drilling parameters,such as drilling pressure and drilling torque,affected by the characteristics of prefabricated cracks,and clarifies the degradation mechanism of rock equivalent compressive strength.Additionally,an identification model for the characteristic parameters of rock mass structural planes during drilling is established.The test results indicate that the average difference of the characteristics of prefabricated cracks identified by the equivalent compressive strength is 2.45°and 0.82 mm,respectively.The identification model while drilling is verified to be correct due to the high identification accuracy.Based on this,a method for testing the characteristic parameters of the surrounding rock structural plane while drilling is proposed.The research offers a theoretical and methodological foundation for precise in situ identification of structural planes of the surrounding rock in underground engineering.
基金funded by the National Science Foundation of China(Grant Nos.41702374,4177020938,2018YFC1505406)China Geological Survey projects(Grant Nos.DD20190640,20190505)
文摘Rock–soil aggregate landslides(RSALs) are a common geological hazard in deeply incised valleys in southwestern China. Large-scale RSALs are widely distributed in the upper reaches of the Dadu River, Danba County, Sichuan Province, and are influenced by slope structure, which can be divided into open, lock, strip, and dumbbell types, as well as soil type and meso-structure, which can be classified as layered rock–soil aggregate, block-soil, and grainsoil. In this study, the evolution of four types of structures, such as layered-dumbbell, block-soil lock, banded block-soil, and block-soil open types, were analyzed by field surveys, surface and deep displacement monitoring, and Flac3 D. It was found that the Danba reach of the Dadu River showed incised valley through the evolution from wide to slow valley affected by internal and external geological processes since the Quaternary Glaciation. In the layered-dumbbell rock–soil aggregate, the main sliding pattern is multi-stage sliding at different depths. Circular sliding in the trailing edge and plane sliding along the bedrock in the front edge body occurin the block-soil-lock type aggregate. Large-scale multi-level and circular sliding over long distances occur in the banded block-soil aggregate. The blocksoil open type is stable, with only circular sliding occurring in local and shallow surfaces of the body. The monitoring and numerical simulation results further show that slope structure and regularity have diversified with RSALs. The results provide a basis for analyzing the stability mechanism of RSALs and preventing RSALs in deeply incised valleys.
基金supported by The Outstanding Youth Foundation Project, National Natural Science Foundation of China (Grant No. 40625004) the grant of the Western Project Program of the Chinese Academy of Sciences (No. KZCX2-XB2-10)
文摘Based on the analysis and comparison of soil temperature, thermal regime and permafrost table under the experimental embankment of crushed rock structures in Beiluhe, results show that crushed rock structures provide an extensive cooling effect, which produces a rising permafrost table and decreasing soil temperatures. The rise of the permafrost table under the embankment ranges from an increase of 1.08 m to 1.67 m, with an average of 1.27 m from 2004 to 2007. Mean annual soil temperatures under the crushed rock layer embankment decreased significantly from 2005 to 2007, with average decreases of ?1.03 °C at the depth of 0.5 m, ?1.14 °C at the depth of 1.5 m, and ?0.5 °C at the depth of 5 m. During this period, mean annual soil temperatures under the crushed rock cover embankment showed a slight decrease at shallow depths, with an average decrease of ?0.2 °C at the depth of 0.5 m and 1.5 m, but a slight rise at the depth of 5 m. After the crushed rock structures were closed or crammed with sand, the cooling effect of the crushed rock layer embankment was greatly reduced and that of the crushed rock cover embankment was just slightly reduced.
基金co-funded by the National Natural Science Foundation of China (Grant Nos. 42372160, 42072172)Shandong Province Natural Science Fund for Distinguished Young Scholars (Grant No. JQ201311)the Graduate Scientific and Technological Innovation Project financially supported by Shandong University of Science and Technology (Grant No. SDKDYC190313)。
文摘The Jurassic coal-measure source rocks in the Junggar Basin have drawn considerable attention in recent years. In our hydrocarbon thermal simulation experiments of these rocks, we found that the dark mudstone evaluated as good source rock, had a much lower hydrocarbon generation capacity than the coal and carbonaceous mudstone, evaluated as poor source rock. Based on this background, we performed Fourier transform infrared spectroscopy(FTIR) and combined the results of semi-open thermal simulation experiments to explore the association between the molecular structure and hydrocarbon production capacity, with the aim of obtaining a new understanding of hydrocarbon potential of Jurassic coal-measure source rocks from the perspective of molecular structure. The results indicate that coals exhibit lower condensation of aromatic structures and higher relative abundance of aliphatic structures with a higher degree of branched chaining than mudstones and carbonaceous mudstones. Apparent aromaticity(f_a), aromatic abundance parameter I, and degree of condensation(DOC) are negatively correlated with organic matter abundance. The aliphatic structural parameter H demonstrates a substantial positive correlation with organic matter abundance. Furthermore, aliphatic relative abundance factor A is associated with the type of organic matter;the better is the type of the organic matter, the larger is the A value. The combination of the molecular structures with the thermal simulation results shows that the aliphatic hydrogen enrichment of selected carbonaceous mudstone is similar to that of coal. However, the relative abundance of the aliphatic group of it is high, and the DOC of the aromatic structure is low, making the hydrocarbon generation base stronger and easier to crack. Thus, the hydrocarbon generation capacity of carbonaceous mudstone is slightly higher than that of coal. Mudstone has low H and I values, and the DOC is high, indicating that its hydrocarbon base is low, so it has low hydrocarbon generation capacity. Therefore, the molecular structure is closely associated with the hydrocarbon potential of coal-measure source rocks. When evaluating the qualities of coal-measure source rocks, the influence of molecular structure on these rocks should be considered.
基金supported by CNOOC Research Institute,the Major National R&D project(Grant No.2008 ZX05025)the National R&D project(Grant No.2017 yfc0602202)。
文摘The distribution of oil and gas resources in the South China Sea and adjacent areas is closely related to the structural pattern that helped to define the controlling effect of deep processes on oil-bearing basins.Igneous rocks can record important information from deep processes.Deep structures such as faults,basin uplift and depression,Cenozoic basement and magnetic basement are all the results of energy exchange within the earth.The study of the relationship between igneous rocks and deep structures is of great significance for the study of the South China Sea.By using the minimum curvature potential field separation technique and the correlation analysis technique of gravitational and magnetic anomalies,the fusion of gravitational and magnetic data reflecting igneous rocks can be obtained,through which the igneous rocks with high susceptibility/high density or high susceptibility/low density can be identified.In this study area,igneous rocks do not develop in the Yinggehai basin,Qiongdongnan basin,Zengmu basin and Brunei-Sabah basin whilst igneous rocks with high susceptibility/high density or high susceptibility/low density are widely-developed in other basins.In undeveloped igneous areas,faults are also undeveloped the Cenozoic thickness is greater,the magnetic basement depth is greater and the Cenozoic thickness is highly positively correlated with the magnetic basement depth.In igneously developed regions,the distribution pattern of the Qiongtai block is mainly controlled by primary faults,while the distribution of the Zhongxisha block,Xunta block and Yongshu-Taiping block is mainly controlled by secondary faults,the Cenozoic thickness having a low correlation with the depth of the magnetic basement.
基金Supported by the National Natural Science Fundation of China (50674045)the National "973" Planning Project(2007CB209403)
文摘Through the description of the deformational features of the surrounding rockaround high stress engineering soft rock roadways,the coupling stabilization principle ofinner and outer structures in surrounding rock was put forward.The supporting principlesof high stress engineering soft rock roadway (high resistance and yielding support,timelysupport,high strength and high stiffness supports) were proposed,which were applied inengineering practices,and obtained better achievements.
文摘Rock mechanics projects, excavations and rock mass monitoring are day-by-day concerns of professionals and scientists of rock engineer. Technological advances observed in the 20 and 21 centuries provided high precision equipment capable of establishing deformation and estimating the rock mass stress remotely and in real time. In addition, in order to confirm and study the data obtained with theses equipment, numerical programs of modeling became more accessible to schools, research centers and private companies. Monitoring an excavation requires, besides understanding fully the rock structure, precise definitions and goals: why, how, where. This article discusses concepts of monitoring, modeling and calibration, as well as presents examples of applications where these questions were successfully answered.
基金supported by the National Natural Science Foundation of China(No.U23A2047,No.42277187,No.42307248)Natural Science Foundation of Hebei Province(No.D2022202005)。
文摘Rock slopes with large intersection angles between the strikes of strata and surface(RS-LISS)represent a unique type of layered rock slope.These slopes are usually considered to be well stabilized and less prone to landslides.However,when such slopes contain a significant number of discontinuities,their stability is greatly weakened.This study provided innovative insights into the stability of RS-LISS and conducted an in-depth investigation of their step-path failure mechanisms.The Riyi landslide on the eastern margin of the Qinghai-Tibet Plateau,China,was taken as a typical case and detailed investigations of geological structure and deformation characteristics of the slope were conducted by means of slope mapping,core drilling,and exploratory adits.A large number of steep-dip and gentle-dip joints were discovered in the slope,along with several critical discontinuities such as faults.Analysis shows that the tectonic stresses and river downcutting over geological time played significant roles in the formation of these discontinuities.Based on the investigation results,a numerical model of DFN for the Riyi landslide was developed.The simulation results indicated that the slope could develop a sliding surface characterized by a steep back and a gentle base,formed through the stepped interconnection of various discontinuities.Additionally,the deformation of the rock mass mainly originated from the major fault,progressively extending downward.The sliding mass may slide suddenly as a whole along the stepped bottom surface,with the compressional fracture zones as lateral boundaries,presenting a"drawer-like"movement towards the free surface.
基金supported by financial support from the National Natural Science Foundation of China(Grant Nos.52309122 and U2340229)the Innovation Team of Changjiang River Scientific Research Institute(Grant No.CKSF2024329/YT).
文摘Large-scale and heavily jointed rocks have inherent planes of anisotropy and secondary structural planes,such as dominant joint sets and random fractures,which result in significant differences in their failure mechanism and deformation behavior compared to other rock types.To address this issue,inherent anisotropic rocks with large-scale and dense joints are considered to be composed of the rock matrix,inherent planes of anisotropy,and secondary structural planes.Then a new implicit continuum model called LayerDFN is developed based on the crack tensor and damage tensor theories to characterize the mechanical properties of inherent anisotropic rocks.Furthermore,the LayerDFN model is implemented in the FLAC3D software,and a series of numerical results for typical example problems is compared with those obtained from the 3DEC,the analytical solutions,similar classical models,laboratory uniaxial compression tests,and field rigid bearing plate tests.The results demonstrate that the LayerDFN model can effectively capture the anisotropic mechanical properties of inherent anisotropic rocks,and can quantitatively characterize the damaging effect of the secondary structural planes.Overall,the numerical method based on the LayerDFN model provides a comprehensive and reliable approach for describing and analyzing the behavior of inherent anisotropic rocks,which will provide valuable insights for engineering design and decision-making processes.
文摘The most of high/ultrahigh-pressure(HP/UHP)terranes of the world are characterized by the occurrence of numerous pods,lenses or layered blocks of eclogite and amphibolites(e.g.O’Brien,1997;Elvevold and Gilotti,2000;Zhang et al.,2003;and references there in).Field and petrological features suggest that amphibolites should
基金Supported by the National Natural Science Foundation of China(U21B2062).
文摘This study comprehensively uses various methods such as production dynamic analysis,fluid inclusion thermometry and carbon-oxygen isotopic compositions testing,based on outcrop,core,well-logging,3D seismic,geochemistry experiment and production test data,to systematically explore the control mechanisms of structure and fluid on the scale,quality,effectiveness and connectivity of ultra-deep fault-controlled carbonate fractured-vuggy reservoirs in the Tarim Basin.The results show that reservoir scale is influenced by strike-slip fault scale,structural position,and mechanical stratigraphy.Larger faults tend to correspond to larger reservoir scales.The reservoir scale of contractional overlaps is larger than that of extensional overlaps,while pure strike-slip segments are small.The reservoir scale is enhanced at fault intersection,bend,and tip segments.Vertically,the heterogeneity of reservoir development is controlled by mechanical stratigraphy,with strata of higher brittleness indices being more conducive to the development of fractured-vuggy reservoirs.Multiple phases of strike-slip fault activity and fluid alterations contribute to fractured-vuggy reservoir effectiveness evolution and heterogeneity.Meteoric water activity during the Late Caledonian to Early Hercynian period was the primary phase of fractured-vuggy reservoir formation.Hydrothermal activity in the Late Hercynian period further intensified the heterogeneity of effective reservoir space distribution.The study also reveals that fractured-vuggy reservoir connectivity is influenced by strike-slip fault structural position and present in-situ stress field.The reservoir connectivity of extensional overlaps is larger than that of pure strike-slip segments,while contractional overlaps show worse reservoir connectivity.Additionally,fractured-vuggy reservoirs controlled by strike-slip faults that are nearly parallel to the present in-situ stress direction exhibit excellent connectivity.Overall,high-quality reservoirs are distributed at the fault intersection of extensional overlaps,the central zones of contractional overlaps,pinnate fault zones at intersection,bend,and tip segments of pure strike-slip segments.Vertically,they are concentrated in mechanical stratigraphy with high brittleness indices.
基金Supported by the National Natural Science Foundation of China(U22B6002)PetroChina Science and Technology Project(2023ZZ14).
文摘Significant exploration progress has been made in ultra-deep clastic rocks in the Kuqa Depression,Tarim Basin,over recent years.A new round of comprehensive geological research has formed four new understandings:(1)Establish structural model consisting of multi-detachment composite,multi-stage structural superposition and multi-layer deformation.Multi-stage structural traps are overlapped vertically,and a series of structural traps are discovered in underlying ultra-deep layers.(2)Five sets of high-quality large-scale source rocks of three types of organic phases are developed in the Triassic and Jurassic systems,and forming a good combination of source-reservoir-cap rocks in ultra-deep layers with three sets of large-scale regional reservoir and cap rocks.(3)The formation of large oil and gas fields is controlled by four factors which are source,reservoir,cap rocks and fault.Based on the spatial configuration relationship of these four factors,a new three-dimensional reservoir formation model for ultra-deep clastic rocks in the Kuqa Depression has been established.(4)The next key exploration fields for ultra-deep clastic rocks in the Kuqa Depression include conventional and unconventional oil and gas.The conventional oil and gas fields include the deep multi-layer oil-gas accumulation zone in Kelasu,tight sandstone gas of Jurassic Ahe Formation in the northern structural zone,multi-target layer lithological oil and gas reservoirs in Zhongqiu–Dina structural zone,lithologic-stratigraphic and buried hill composite reservoirs in south slope and other favorable areas.Unconventional oil and gas fields include deep coal rock gas of Jurassic Kezilenuer and Yangxia formations,Triassic Tariqike Formation and Middle-Lower Jurassic and Upper Triassic continental shale gas.The achievements have important reference significance for enriching the theory of ultra-deep clastic rock oil and gas exploration and guiding the future oil and gas exploration deployment.
基金supported by the Natural Science Foundation of China(No.41274138)
文摘The Ordovician carbonate rocks of the Yingshan formation in the Tarim Basin have a complex pore structure owing to diagenetic and secondary structures. Seismic elastic parameters（e.g., wave velocity） depend on porosity and pore structure. We estimated the average specific surface, average pore-throat radius, pore roundness, and average aspect ratio of carbonate rocks from the Tazhong area. High P-wave velocity samples have small average specific surface, small average pore-throat radius, and large average aspect ratio. Differences in the pore structure of dense carbonate samples lead to fluid-related velocity variability. However, the relation between velocity dispersion and average specific surface, or the average aspect ratio, is not linear. For large or small average specific surface, the pore structure of the rock samples becomes uniform, which weakens squirt fl ow and minimizes the residuals of ultrasonic data and predictions with the Gassmann equation. When rigid dissolved（casting mold） pores coexist with less rigid microcracks, there are significant P-wave velocity differences between measurements and predictions.
基金sponsored by the National Nature Science Foundation of China (Grant No.40904034 and 40839905)
文摘With a more complex pore structure system compared with clastic rocks, carbonate rocks have not yet been well described by existing conventional rock physical models concerning the pore structure vagary as well as the influence on elastic rock properties. We start with a discussion and an analysis about carbonate rock pore structure utilizing rock slices. Then, given appropriate assumptions, we introduce a new approach to modeling carbonate rocks and construct a pore structure algorithm to identify pore structure mutation with a basis on the Gassmann equation and the Eshelby-Walsh ellipsoid inclusion crack theory. Finally, we compute a single well＇s porosity using this new approach with full wave log data and make a comparison with the predicted result of traditional method and simultaneously invert for reservoir parameters. The study results reveal that the rock pore structure can significantly influence the rocks＇ elastic properties and the predicted porosity error of the new modeling approach is merely 0.74%. Therefore, the approach we introduce can effectively decrease the predicted error of reservoir parameters.
基金supported by the undertaken units of subprojects of the Program of Survey on Sandstone-Type Uranium Deposits in Northern Chinathe Ministry of Science and Technology of China(Grant 2015CB453000)the Geological Survey project of China(Grant No.DD20160128)
文摘In Northern China, sandstone-type uranium （U） deposits are mostly developed in Mesozoic-Cenozoic basins. These U deposits are usually hosted in unvarying horizons within the basins and exhibit typical U-forming sedimentary associations, which is referred to as U-bearing rock series. This study describes the structural features of U-bearing rock series within the main Mesozoic-Cenozoic U-producing continental basins in Kazakhstan, Uzbekistan, and Russia in the western segment of the Central Asian Metallogenic Belt （CAMB）, and Northern China in the eastern segment of the CAMB. We analyze the basic structural conditions and sedimentary environments of U-bearing rock series in Northern China and classify their structural styles in typical basins into river valley, basin margin, and intrabasin uplift margin types. The intrabasin uplift margin structural style proposed in this study can be used to indicate directions for the exploration of sandstone-type U deposits hosted in the center of a basin. At the same time, the study of structural style provides a new idea for exploring sandstone-type U deposits in Mesozoic-Cenozoic basins and it is of great significance to prospecting of sandstone-type uranium deposits.
