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Research on the design method for uniform wear of shield cutters in sand-pebble strata

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Deep Underground Science and Engineering 2024年第2期3卷 216-230页

作者： Jinxun Zhang Bo Li Guihe Wang Yusheng Jiang Hua Jiang Minglun Yin Zhengyang Sun Beijing Urban Construction group Co. Ltd.BeijingChina China University of geosciences BeijingChina China University of Mining and Technology BeijingChina

During shield tunneling in highly abrasive formations such as sand–pebble strata,nonuniform wear of shield cutters is inevitable due to the different cutting distances.Frequent downtimes and cutter replacements have become major obstacles to long-distance shield driving in sand–pebble strata.Based on the cutter wear characteristics in sand–pebble strata in Beijing,a design methodology for the cutterhead and cutters was established in this study to achieve uniform wear of all cutters by the principle of frictional wear.The applicability of the design method was verified through three-dimensional simulations using the engineering discrete element method.The results show that uniform wear of all cutters on the cutterhead could be achieved by installing different numbers of cutters on each trajectory radius and designing a curved spoke with a certain arch height according to the shield diameter.Under the uniform wear scheme,the cutter wear coefficient is greatly reduced,and the largest shield driving distance is increased by approximately 47%over the engineering scheme.The research results indicate that the problem of nonuniform cutter wear in shield excavation could be overcome,thereby providing guiding significance for theoretical innovation and construction of long-distance shield excavation in highly abrasive strata.

关键词： cutter wear EDEM model long-distance shield driving sand-pebble stratum shield tunnel uniform wear design method

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Study on Shear Strength Characteristics of Basalt-Concrete Bonding Interface Based on in-situ Direct Shear Test

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Journal of Earth Science 2024年第2期35卷 553-567页

作者： Peng Xia Xinli Hu Chunye Ying Shuangshuang Wu Chu Xu Xuan Wang Hao Chen Hang Duan College of Harbour and Coastal Engineering Jimei UniversityXiamen361021China Faculty of Engineering China University of GeosciencesWuhan430074China China Three Gorges Construction group Ltd.Beijing100038China

In rock engineering,the shear strength of the basalt-concrete bonding interface is a key factor affecting the shear performance of hydroelectric dam foundations,embedded rock piles and rock bolts.In this study,30 sets of in-situ direct shear tests were conducted on the basalt-concrete bond interface in the Baihetan dam area to investigate the shear strength characteristics of the basalt-concrete bonding interface.The bonding interface contains two states,i.e.,the bonding interface is not sheared,termed as se(symbolic meaning see Table 1);the bonding interface is sheared with rupture surface,termed as si.The effects of lithology,Joints structure,rock type grade and concrete compressive strength on the shear strength of the concrete-basalt contact surface were investigated.The test results show that the shear strength of the bonding interface(s_(e)&s_(i))of columnar jointed basalt with concrete is greater than that of the bonding interface(s_(e)&s_(i))of non-columnar jointed one with the same rock type grade.When the rock type grade isⅢ_(2),fcol is 1.22 times higher than fncol and ccol is 1.13 times greater than cncol.The shear strength parameters of the basalt-concrete bonding interface differ significantly for different lithologies.The cohesion of the bonding interface(s_(i))of cryptocrystalline basalt with concrete is 2.05 times higher than that of the bonding interface(s_(i))of breccia lava with concrete under the same rock type grade condition.Rock type grade has a large influence on the shear strength of the non-columnar jointed basalt-concrete bonding interface(s_(e)&s_(i)).cnol increases by 33%when the grade of rock type rises fromⅢ_(1)toⅡ_(1).the rock type grade has a greater effect on bonding interface(s_(i))cohesion than the coefficient of friction.When the rock type grade is reduced fromⅢ_(2)toⅢ_(1),f_(ncol)′increases by 2%and c_(ncol)′improves by 44%.The shear strength of the non-columnar jointed basalt-concrete bonding interface(s_(e)&s_(i))increases with the increase of the compressive strength of co

关键词： direct shear test basalt-concrete bonding interface shear strength parameters engineering geogolgy

Provenance of the Lower Jurassic pyroclastic sediments in the Zigui Basin:Implication for crustal thickening in the eastern Qinling orogenic belt

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Science China Earth Sciences 2024年第1期67卷 196-207页

作者： Rong CHAI Jianghai YANG Yuansheng DU Chengshan WANG School of Earth Sciences and Resources China University of Geosciences(Beijing)Beijing 100023China School of Earth Sciences China University of Geosciences(Wuhan)Wuhan 430074China Chinese Academy of Geological Sciences Beijing 100037China

The Late Triassic witnessed significant collisional orogenic events in the Qinling orogenic belt,accompanied by magma underplating and tectonic deformation.These processes potentially resulted in substantial crustal thickening and uplift of the Qinling orogen.However,due to the absence of igneous rock records from this period in the eastern section of the Qinling orogen,the changes in crustal thickness during this orogenic process have not been thoroughly investigated.A series of foreland basins emerged during the Early Mesozoic to the south of the East Qinling orogenic belt.These basins have preserved clastic sedimentary rocks derived from the uplift and erosion of the orogenic belt.These sedimentary records serve as crucial records to reconstruct the evolutionary history of the Qinling orogen.To further clarify the collisional orogenic process of the Qinling orogenic belt,this study conducted in situ volcanic lithic fragment geochemistry,detrital zircon U-Pb chronology and trace element composition analysis on the sandstones of the Lower Jurassic Tongzhuyuan Formation in the Zigui Basin.The results suggest that the sandstones,which exhibit a significant abundance of volcanic lithic fragments,has a characteristic detrital zircon age group of 250–200 Ma,indicating a major provenance from the Triassic volcanic rocks.Combined with regional correlation and paleocurrent analysis,the detrital zircon U-Pb age data show that the source area of volcanic rocks should be in the Qinling orogenic belt to the north of the basin.This interpretation is further supported by the Triassic granitic rocks exposed in the western part of the orogenic belt,representing the magmatism during the Triassic collisional orogenesis in the Qinling orogen.Based on the co-varying relationships between present-day crust thickness with the chemical compositions of granite rocks and zircons,the La/Yb ratio of volcanic lithic fragments in the Tongzhuyuan Formation and the Eu/Eu*ratio of detrital zircons with Triassic ages indicate that the Qinling o

关键词： Qinling orogenic belt Zigui Basin Late Triassic Detrital zircons Crustal thickening

Origin and tectonic setting of low-Si alkaline magma

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Science China Earth Sciences 2024年第5期67卷 1417-1435页

作者： Qiushi ZHOU Rui WANG State Key Laboratory of Geological Processes and Mineral Resources and Institute of Earth SciencesChina University of GeosciencesBeijing 100083China Frontiers Science Center for Deep-time Digital Earth China University of Geosciences(Beijing)Beijing 100083China

Despite of the relatively rare occurrence of alkaline igneous rocks on Earth, they are the most diverse group of igneous rocks due to variations in their mineral assemblages and geochemical compositions. Alkaline igneous rocks are generally characterized by Si undersaturation, and K-Na(and in some cases C) enrichment. Although there is no unified alkaline igneous rock classification scheme, diagrams such as total alkalis-SiO_(2) or K_(2)O-SiO_(2) can be used to classify alkaline igneous rocks. The origins of silica-saturated alkaline rocks(SiO_(2)>52 wt.%) are relatively complex because multiple episodes of magmatism are often involved, therefore most studies have focused on the origins of silica-undersaturated alkaline magmas.Numerous experimental petrological studies have been conducted in the past few decades. Initially, it was considered that enrichment of trace elements was only achieved by low-degree partial melting of mantle peridotite, but the experimental melts could not reproduce the geochemical composition of natural alkaline igneous rocks. Subsequent studies have focused on carbonate-bearing eclogites that represent the average component of subducted oceanic crust. Although experimental studies indicate that silica-undersaturated and alkali-oversaturated melts can be generated from eclogites, some studies have considered that natural silica-undersaturated alkaline igneous rocks are the result of multi-stage source enrichment by incompatible elements. Low-degree partial melts of the mantle can be emplaced in the lithospheric mantle, forming veins consisting of phlogopite, amphibole, and pyroxene. Melting experiments including these components show that the produced melts better reproduce the naturally occurring silica-undersaturated alkaline magmas. Silica-deficient alkaline igneous rocks occur in various tectonic settings. Those in intraplate and divergent settings(i.e., mainly continental rifts) normally involve contributions from recycled components such as subducted slabs at the mantle transition z

关键词： Alkaline igneous rock Tectonic setting Petrogenesis Big data

The organic geochemistry of crude oil in the Saltpond Basin(Ghana):Organic source input,depositional environment,and thermal maturity

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Acta Geochimica 2024年第3期43卷 424-440页

作者： Kojo Amoako Ningning Zhong Nancy Pearl Osei-Boakye Ebenezer Apesegah Research group for Marine Geochemistry(ICBM-MPI Bridging group) Institute for Chemistry and Biology of the Marine Environment(ICBM)School of Mathematics and ScienceCarl von Ossietzky UniversitäOldenburgAmmerläder HeerstraВ114-11826129 OldenburgGermany State Key Laboratory of Petroleum Resources and Prospecting College of GeosciencesChina University of PetroleumBeijing 102249China Petroleum Corporation GNPCPMBPetroleum HouseTemaGhana

The Saltpond Basin,situated within the South Atlantic margin of Ghana,is a significant area for petro-leum exploration but has received relatively limited research attention.Previous studies have examined source rock com-position,but data on crude oil organic chemistry are lack-ing,hindering understanding of the basin’s petroleum system and evolution.To address this gap,we analyzed biomarkers and stable carbon-isotope ratios in Saltpond Basin crude oil using gas chromatography–mass spectrometry and gas chromatography–isotope ratio mass spectrometry to eluci-date organic matter source,depositional environment,and thermal maturity.Findings were compared with oils from the West African segment of the South Atlantic margin,namely the Tano Basin and the Niger Delta Basin,to iden-tify potential correlations and gain insights into regional variations.Molecular and isotopic results unveiled a sig-nificant prevalence of organic matter derived from lower marine organisms.Patterns of organic matter deposition and preservation in Saltpond oil samples suggested a suboxic marine transitional environment,contradicting conventional understanding of terrestrial dominance in such settings.Moreover,the potential for degradation processes to obscure differentiation between terrestrial and marine organic mat-ter origins underscores the complex nature of organic mat-ter dynamics in transitional marine environments.Analysis of molecular thermal maturity indices suggested Saltpond oils were expelled from source rocks exhibiting thermal maturity at the early maturity stage.Correlation analysis unveiled genetic disparities among crude oils sourced from the Saltpond Basin and those from the Tano and Niger Delta Basin,primarily due to variations in source input and depo-sitional environment conditions.Saltpond oil exhibits lower terrestrial organic input than Tano Basin’s crude oils,which also have less terrestrial input than Niger Delta Basin crude oils.Additionally,its paleodepositional environment nota-bly differs from oils in the Tano B

关键词： Biomarkers Carbon isotopes Crude oil Saltpond Basin Ghana

Enhancing Geological Understanding and Identifying Gold Anomalies in the Ailaoshan Orogen

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Acta Geologica Sinica(English Edition) 2024年第2期98卷 441-453页

作者： ZHAO Shiyu YANG Lin SONG Yiwei DONG Yuntao FENG Lihao LI Huajian WU Junyu WANG Qingfei State Key Laboratory of Geological Processes and Mineral Resources China University of GeosciencesBeijing 100083China Xi’an Center of Mineral Resources Survey China Geological SurveyXi’an 710010China Yunnan Gold Mining Industry group Kunming 650299China Jiangxi Provincial Key Laboratory of Genesis and Prospect for Strategic Minerals East China University of TechnologyNanchang 330013China Frontiers Science Center for Deep-time Digital Earth China University of Geosciences(Beijing)Beijing 100083China

The Ailaoshan Orogen in the southeastern Tibet Plateau,situated between the Yangtze and Simao blocks,underwent a complex structural,magmatic,and metamorphic evolution resulting in different tectonic subzones with varying structural lineaments and elemental concentrations.These elements can conceal or reduce anomalies due to the mutual effect between different anomaly areas.Dividing the whole zone into subzones based on tectonic settings,ore cluster areas,or sample catchment basins(Scb),geochemical and structural anomalies associated with gold(Au)mineralization have been identified utilizing mean plus twice standard deviations(Mean+2STD),factor analysis(FA),concentration-area(CA)modeling of stream sediment geochemical data,and lineament density in both the Ailaoshan Orogen and the individual subzones.The FA in the divided 98 Scbs with 6 Scbs containing Au deposits can roughly ascertain unknown rock types,identify specific element associations of known rocks and discern the porphyry or skarn-type Au mineralization.Compared with methods of Mean+2STD and C-A model of data in the whole orogen,which mistake the anomalies as background or act the background as anomalies,the combined methods of FA and C-A in the separate subzones or Scbs works well in regional metallogenic potential analysis.Mapping of lineament densities with a 10-km circle diameter is not suitable to locate Au deposits because of the delineated large areas of medium-high lineament density.In contrast,the use of circle diameters of 1.3 km or 1.7 km in the ore cluster scale delineates areas with a higher concentration of lineament density,consistent with the locations of known Au deposits.By analyzing the map of faults and Au anomalies,two potential prospecting targets,Scbs 1 and 63 with a sandstone as a potential host rock for Au,have been identified in the Ailaoshan Orogen.The use of combined methods in the divided subzones proved to be more effective in improving geological understanding and identifying mineralization anomalies associated with Au,rath

关键词： minerology geochemistry gold stream sediment sample catchment basin concentration-area model lineament density Ailaoshan Orogen

Correlation Study on Grain Size Characteristics and Geotechnical Properties of Surface Sediments in Qingdao Offshore Area

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Journal of Ocean University of China 2024年第3期23卷 721-730页

作者： LI Anlong WANG Panpan GUO Xijun JI Xiangkun SHEN Kunming LIN Lin YAN Zhichao YUAN Lin Key Laboratory of Submarine geosciences and Prospecting Techniques Ministry of Education and College of Marine GeosciencesOcean University of ChinaQingdao 266100China College of Marine Geoscience Ocean University of ChinaQingdao 266100China China Construction Second Engineering Bureau Co. LTDYueyang 414000China Tianjin Research Institute for Water Transport Engineering M.O.T.Tianjin 3000456China Lianyungang Xuwei Port Holding group Co. Ltd.Lianyungang 222042China

The comprehension of sediment grain size parameters and the corresponding sedimentary environment holds paramount importance in elucidating the engineering geological attributes of the subaqueous seabed.This study delineated the sedimentary environment zoning in the northern sea area of Qingdao through cluster analysis of grain size parameters derived from 123 surface sediment samples.The study analyzed the correlation between sediment geotechnical indices and grain size parameters across diverse sedimentary environments.A correlation equation was established for samples exhibiting a strong correlation.The study found four distinct sedimentary environments in the study area:coastal,transitional,shallow sea,and residual.Within the same sedimentary environment,the average grain size and sorting coefficient exhibit significant correlations with geotechnical indices such as water content,density,shear strength,plastic limit,liquid limit,and plastic index.However,notable disparities in the correlation between grain size parameters and geotechnical indices emerge across different sedimentary environments.

关键词： grain size parameters cluster analysis sedimentary environment correlations geotechnical indexes

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Deep Underground Earthquake Observation: Small to Moderate Earthquakes and Microearthquakes Identification

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Journal of Earth Science 2024年

作者： Chang Chen Wentao Wan Yun Wang Jinsong Liu Hongyi Li Qiangqiang Miao Yongsheng He Juan Qi Chao Wang Institute of Geochemistry Chinese Academy of Sciences MWMC Research group School of Geophysics and Information Technology China University of geosciences College of Electrical and Information Engineering Anhui University of Science and Technology Institute of Engineering Protection Engineering Research Institute of Academy of Military Sciences State Kay Laboratory of Geological Processes and Mineral Resources China University of geosciences Beijing China

0 Introduction Small to moderate earthquakes and microearthquakes occur widely and numerously (Luo，

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Geochemical fingerprints and hydrocarbon potential of Paleocene mudrocks in the Tano Basin, Ghana: insights from biomarkers and stable carbon isotopes

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Acta Geochimica 2024年第2期43卷 255-279页

作者： Kojo Amoako Nancy Pearl Osei-Boakye Ningning Zhong N’Guessan Francois De Sales Konan Gordon Foli Prince Opoku Appau Clifford Fenyi Ebenezer Apesegah Research group for Marine Geochemistry(ICBM-MPI Bridging group) Institute for Chemistry and Biology of the Marine Environment(ICBM)Carl von Ossietzky University OldenburgAmmerlander Heerstr.26129 OldenburgGermany State Key Laboratory of Petroleum Resources and Prospecting College of GeosciencesChina University of PetroleumBeijing 102249China Department of Geological Engineering Faculty of Civil and Geo-EngineeringKwame Nkrumah University of Science and TechnologyKumasiGhana Ghana National Gas Company 225 Osibisa CloseAirport WestAccraGhana Petroleum Corporation GNPCPMBPetroleum HouseTemaGhana

The Paleocene mudrocks in Ghana’s Tano Basin have received limited attention despite ongoing efforts to explore hydrocarbon resources.A thorough geochemical analysis is imperative to assess these mudrocks’petroleum generation potential and formulate effective exploration strategies.In this study,a comprehensive geochemical analysis was carried out on ten Paleocene rock cuttings extracted from TP-1,a discovery well within the Tano Basin.Various analytical techniques,including total organic carbon(TOC)analysis,Rock–Eval pyrolysis,gas chromatography-mass spectrometry,and isotope ratio-mass spectrometry,were employed to elucidate their hydrocar-bon potential and organic facies.Theﬁndings in this study were subsequently compared to existing geochemical data on Paleocene source rocks in the South Atlantic marginal basins.The results indicated that the Paleocene samples have TOC content ranging from 0.68 to 2.93 wt%.The prevalent kerogen types identiﬁed in these samples were Type Ⅱ and Type Ⅲ.Molecular and isotope data suggest that the organic matter found in the Paleocene mudrocks can be traced back to land plants and lower aquatic organisms.These mudrocks were deposited in a transi-tional environment withﬂuctuating water salinity,charac-terized by sub-oxic redox conditions.Maturity indices,both bulk and molecular,indicated a spectrum of maturity levels within the Paleocene mudrocks,spanning from immature to marginally mature,with increasing maturity observed with greater depth.In comparison,the organic composition and depositional environments of Paleocene source rocks in the Tano Basin closely resemble those found in the Niger Delta Basin,Douala,and Kribi-Campo Basins,the Kwanza Formation in Angola,and certain Brazilian marginal basins.However,it is worth noting that Paleocene source rocks in some of the basins,such as the Niger Delta and Brazilian marginal basins,exhibit rela-tively higher thermal maturity levels compared to those observed in the current Paleocene samples from the Tano Basin.In conclusion,the compre

关键词： Paleocene source rocks Source input Depositional environment Thermal maturity Hydrocarbon potential Tano Basin West Africa