Uncertainties about natural gas source and hydrocarbon accumulation seriously restrict oil and gas exploration in the Lianggaoshan Formation(J_(2) l)in the Eastern Sichuan Basin,which has demonstrated great exploratio...Uncertainties about natural gas source and hydrocarbon accumulation seriously restrict oil and gas exploration in the Lianggaoshan Formation(J_(2) l)in the Eastern Sichuan Basin,which has demonstrated great exploration potential in recent years.This study determines the origin of natural gas and the hydrocarbon accumulation model of J_(2) l in the Eastern Sichuan Basin.A new sample pretreatment method named gas purge-microsyringe extraction was employed and confi rmed to be a practical and eff ective method for preparing condensate oil and collecting source rock extract samples.The source rocks of J_(2) l exhibited moderate to good qualities,characterized by high TOC values,dominance of type Ⅱ_(1) and Ⅱ_(2) kerogens,and high thermal maturities.Biomarker and aromatic characteristics revealed that the source rocks of J_(2) l were deposited in brackish water with weak anoxic conditions.The natural gas in J_(2) l was an organic thermogenic gas generated from the secondary cracking of crude oil,indicating that this natural gas was mainly derived from the source rocks of J_(2) l.The condensate oil-source rock correlation further confi rmed the accuracy of the gas-source correlation results.Based on burial,thermal and hydrocarbon-generating histories,two hydrocarbon charging periods(141–133 Ma and 119–112 Ma)and four hydrocarbon accumulation periods of J_(2) l were determined.Combined with structural evolution,depositional histories and reservoir conditions,a simple gas reservoir accumulation model of J_(2) l was developed,which was identifi ed as a“self-generating and self-storing”gas reservoir.展开更多
Cohesion(c) and friction angle(φ) of rock are important parameters required for reliability analysis of rock slope stability. There is correlation between c and φ which affects results of reliability analysis of roc...Cohesion(c) and friction angle(φ) of rock are important parameters required for reliability analysis of rock slope stability. There is correlation between c and φ which affects results of reliability analysis of rock slope stability. However, the characterization of joint probability distribution of c and φ through which their correlation can be estimated requires a large amount of rock property data, which are often not available for most rock engineering projects. As a result, the correlation between c and φ is often ignored or simply assumed during reliability studies, which may lead to bias estimation of failure probability. In probabilistic rock slope stability analysis, the influence of ignoring or simply assuming the correlation of the rock strength parameters(i.e., c and φ) on the reliability of rock slopes has not been fully investigated. In this study, a Bayesian approach is developed to characterize the correlation between c and φ, and an expanded reliability-based design(RBD) approach is developed to assess the influence of correlation between c and φ on reliability of a rock slope. The Bayesian approach characterizes the sitespecific joint probability distribution of c and φ, and quantifies the correlation between c and φ using available limited data pairs of c and φ from a rock project. The expanded RBD approach uses the joint probability distribution of c and φ obtained through the Bayesian approach as inputs, to determine the reliability of a rock slope. The approach gives insight into the propagation of the correlation between c and φ through their joint probability into the reliability analysis, and their influence on the calculated reliability of the rock slope. The approaches may be applied in practice with little additional effort from a conventional analysis. The proposed approaches are illustrated using real c and φ data pairs obtained from laboratory tests of fractured rock at Forsmark, Sweden.展开更多
In this paper, uniaxial compression tests were carried out on a series of composite rock specimens with different dip angles, which were made from two types of rock-like material with different strength. The acoustic ...In this paper, uniaxial compression tests were carried out on a series of composite rock specimens with different dip angles, which were made from two types of rock-like material with different strength. The acoustic emission technique was used to monitor the acoustic signal characteristics of composite rock specimens during the entire loading process. At the same time, an optical non-contact 3 D digital image correlation technique was used to study the evolution of axial strain field and the maximal strain field before and after the peak strength at different stress levels during the loading process. The effect of bedding plane inclination on the deformation and strength during uniaxial loading was analyzed. The methods of solving the elastic constants of hard and weak rock were described. The damage evolution process, deformation and failure mechanism, and failure mode during uniaxial loading were fully determined. The experimental results show that the θ = 0?–45?specimens had obvious plastic deformation during loading, and the brittleness of the θ = 60?–90?specimens gradually increased during the loading process. When the anisotropic angle θincreased from 0?to 90?, the peak strength, peak strain,and apparent elastic modulus all decreased initially and then increased. The failure mode of the composite rock specimen during uniaxial loading can be divided into three categories:tensile fracture across the discontinuities(θ = 0?–30?), slid-ing failure along the discontinuities(θ = 45?–75?), and tensile-split along the discontinuities(θ = 90?). The axial strain of the weak and hard rock layers in the composite rock specimen during the loading process was significantly different from that of the θ = 0?–45?specimens and was almost the same as that of the θ = 60?–90?specimens. As for the strain localization highlighted in the maximum principal strain field, the θ = 0?–30?specimens appeared in the rock matrix approximately parallel to the loading direction,while in the θ = 45?–90?specimens it appeared at the hard and weak rock layer interface.展开更多
The origin of the marine oils in the Tarim Basin has long been a disputed topic. A total of 58 DST （drill stem test） crude oil and 8 rock samples were investigated using a comprehensive geochemical method to charact...The origin of the marine oils in the Tarim Basin has long been a disputed topic. A total of 58 DST （drill stem test） crude oil and 8 rock samples were investigated using a comprehensive geochemical method to characterize and identify the origin of the Ordovician oils in the Tazhong Uplift, Tarim Basin, northwest China. Detailed oil–oil and oil–source rock correlations show that the majority of the oils have typical biomarker characteristics of the Middle-Upper Ordovician （O2＋3） source rock and the related crude oil. These characteristics include a distinct ＂V-shaped＂ relative abundance of C27, C28 and C29 regular steranes, low abundance of dinosterane, 24-norcholestanes, triaromatic dinosteroids and gammacerane. Only a few oils display typical biomarker characteristics indicating the Cambrian–Lower Ordovician （∈-O1） genetic affinity, such as linear or anti ＂L＂ shape distribution of C27, C28 and C29 regular sterane, with relatively high concentrations of dinosterane, 24-norcholestanes, triaromatic dinosteroids and gammacerane. It appears that most of the Ordovician oils in the Tazhong Uplift were derived from the O2＋3 intervals, as suggested by previous studies. However, the compound specific n-alkane stable carbon isotope data indicate that the Ordovician oils are mixtures from both the ∈-O1 and O2＋3 source rocks rather than from the O2＋3 strata alone. It was calculated that the proportion of the∈-O1 genetic affinity oils mixed is about 10.8%-74.1%, with an increasing trend with increasing burial depth. This new oil-mixing model is critical for understanding hydrocarbon generation and accumulation mechanisms in the region, and may have important implications for further hydrocarbon exploration in the Tarim Basin.展开更多
The anisotropy induced by rock bedding structures is usually manifested in the mechanical behaviors and failure modes of rocks.Brazilian tests are conducted for seven groups of shale specimens featuring different bedd...The anisotropy induced by rock bedding structures is usually manifested in the mechanical behaviors and failure modes of rocks.Brazilian tests are conducted for seven groups of shale specimens featuring different bedding angles. Acoustic emission (AE) and digital image correlation (DIC) technologies are used to monitor the in-situ failure of the specimens. Furthermore, the crack morphology of damaged samples is observed through scanning electron microscopy (SEM). Results reveal the structural dependence on the tensile mechanical behavior of shales. The shale disk exhibits compression in the early stage of the experiment with varying locations and durations. The location of the compression area moves downward and gradually disappears when the bedding angle increases. The macroscopic failure is well characterized by AE event location results, and the dominant frequency distribution is related to the bedding angle. The b-value is found to be stress-dependent.The crack turning angle between layers and the number of cracks crossing the bedding both increase with the bedding angle, indicating competition between crack propagations. SEM results revealed that the failure modes of the samples can be classified into three types:tensile failure along beddings with shear failure of the matrix, ladder shear failure along beddings with tensile failure of the matrix, and shear failure along multiple beddings with tensile failure of the matrix.展开更多
Aiming at the large deformation and support problems of high-stress and broken-expansion surrounding rock, and taking 1 000 m level roadway of Mine II in Jinchuan as the research object, an investigation on the deform...Aiming at the large deformation and support problems of high-stress and broken-expansion surrounding rock, and taking 1 000 m level roadway of Mine II in Jinchuan as the research object, an investigation on the deformation and damage of roadway surrounding rock and an analysis of its mechanism were carried out. The gray correlation theory was used in support scheme optimization design. First, causes and mechanism of deformation of the 1 000 m horizontal transport channel were analyzed through field investigation, laboratory test and data processing methods. We arguued that poor engineering geological conditions and deep pressure increases were the main factors, and the deformation mechanism was mainly the ground deformation pressure. Second, the gray correlation theory was used to construct supporting optimization decision method in the deep roadway. This method more comprehensively considers various factors, including construction, costs, and supporting material functions. The combined support with pre-stressed anchor cables, shotcrete layer, bolt and metal net was put forward according to the actual roadway engineering characteristics. Finally, 4 support schemes were put forward for new roadways. The gray relational theory was applied to optimizing the supporting method, undertaking technical and economic comparison to obtain the correlation degree, and accordingly the schemes were evaluated. It was concluded as follows： the best was the flexible retaining scheme using the steel strand anchor; the second best was the one using plate anchors on the top and rigid common screw steel bolt on the two sides; the ttiird was; the rigid common screw steel bolt in full section of roadway; and the worst is the planished steel rigid support. The optimized scheme was applied to the 1000 m level of new excavation roadway. The results show that the roadway surrounding rock can reach a stable state after 5 to 6 months monitoring, with a convergence rate less than 1 mm/d.展开更多
Three-dimensional(3D)printing technology is increasingly used in experimental research of geotechnical engineering.Compared to other materials,3D layer-by-layer printing specimens are extremely similar to the inherent...Three-dimensional(3D)printing technology is increasingly used in experimental research of geotechnical engineering.Compared to other materials,3D layer-by-layer printing specimens are extremely similar to the inherent properties of natural layered rock masses.In this paper,soft-hard interbedded rock masses with different dip angles were prepared based on 3D printing(3DP)sand core technology.Uniaxial compression creep tests were conducted to investigate its anisotropic creep behavior based on digital imaging correlation(DIC)technology.The results show that the anisotropic creep behavior of the 3DP soft-hard interbedded rock mass is mainly affected by the dip angles of the weak interlayer when the stress is at low levels.As the stress level increases,the effect of creep stress on its creep anisotropy increases significantly,and the dip angle is no longer the main factor.The minimum value of the long-term strength and creep failure strength always appears in the weak interlayer within 30°–60°,which explains why the failure of the layered rock mass is controlled by the weak interlayer and generally emerges at 45°.The tests results are verified by comparing with theoretical and other published studies.The feasibility of the 3DP soft-hard interbedded rock mass provides broad prospects and application values for 3DP technology in future experimental research.展开更多
The origin and source of the petroleum in the Jurassic reservoirs within the eastern Fukang sub-depression were geochemically investigated.They show thermal maturities matching the peak generation stage,while the cond...The origin and source of the petroleum in the Jurassic reservoirs within the eastern Fukang sub-depression were geochemically investigated.They show thermal maturities matching the peak generation stage,while the condensates are at the early stage of intense cracking.Oils and condensates may have experienced mild evaporative fractionation,while mixing of severely biodegraded with non-biodegraded oils has occurred.Using biomarkers and isotopes,petroleums were classified into GroupⅠ,ⅡandⅢgenetic groups,with GroupⅢfurther divided intoⅢa andⅢb subgroups.GroupⅠpetroleum displays heavy carbon isotopes,a strong predominance of pristine over phytane,high C_(19)and C_(20)tricyclic and C_(24)tetracyclic terpanes,low gammacerane,and dominant C_(29)steranes,while GroupⅡshows light carbon isotopes,a predominance of phytane over pristine,high C_(21)and C_(23)tricyclic with low C_(24)tetracyclic terpanes,high gammacerane and dominant C_(27)steranes.GroupⅢa petroleum shows mixing compositions of GroupⅠandⅡ,while GroupⅢb displays similar compositions to Group I,but with significantly higher Ts,C_(29)Ts and C_(30)diahopane proportions.Oil-source rock correlation suggests GroupⅠandⅡpetroleums originate from Jurassic and Permian source rocks,respectively,while GroupⅢa are mixtures sourced from these rocks andⅢb are mixtures from Jurassic and Triassic source rocks.展开更多
This study considers the Upper Cretaceous Qingshankou Formation,Yaojia Formation,and the first member of the Nenjiang Formation in the Western Slope of the northern Songliao Basin.Dark mudstone with high abundances of...This study considers the Upper Cretaceous Qingshankou Formation,Yaojia Formation,and the first member of the Nenjiang Formation in the Western Slope of the northern Songliao Basin.Dark mudstone with high abundances of organic matter of Gulong and Qijia sags are considered to be significant source rocks in the study area.To evaluate their development characteristics,differences and effectiveness,geochemical parameters are analyzed.One-dimensional basin modeling and hydrocarbon evolution are also applied to discuss the effectiveness of source rocks.Through the biomarker characteristics,the source–source,oil–oil,and oil–source correlations are assessed and the sources of crude oils in different rock units are determined.Based on the results,Gulong and Qijia source rocks have different organic matter primarily detrived from mixed sources and plankton,respectively.Gulong source rock has higher thermal evolution degree than Qijia source rock.The biomarker parameters of the source rocks are compared with 31 crude oil samples.The studied crude oils can be divided into two groups.The oil–source correlations show that group I oils from Qing II–III,Yao I,and Yao II–III members were probably derived from Gulong source rock and that only group II oils from Nen I member were derived from Qijia source rock.展开更多
Studied forecasting and controlling the blasting fragmentation by using artifi- cial neural network for multi-ingredients. At the same time, according to the characteris- tic of multi-parameters input to network model...Studied forecasting and controlling the blasting fragmentation by using artifi- cial neural network for multi-ingredients. At the same time, according to the characteris- tic of multi-parameters input to network model, the gray correlation theory was employed to find out key factors, which can not only save time of computation and parameters in- put, but improve the stability of the model.展开更多
In the future time the exploration of marine oil and gas will be one of the significant domains in China. In this paper the biomarker assemblage characteristics of oilshow in the Nanlinghu Formation of the Majiashan p...In the future time the exploration of marine oil and gas will be one of the significant domains in China. In this paper the biomarker assemblage characteristics of oilshow in the Nanlinghu Formation of the Majiashan pro- file, which is located in Chaoxian County, south of Anhui Province, are described in the light of gas chromatogra- phy/mass spectrometric (GCMS) analysis on the qualitative and quantitative basis. Based on the investigation of the biomarker assemblage characteristics of possible source rocks developed in the area studied, a conclusion is drawn that the oilshow was generated from the Nanlinghu Formation source rocks (abbreviated as T1n), instead of the Qixia Formation source rocks (abbreviated as P1q). It is pointed out that the T1n is of strong potential for future oil explora- tion, and therefore much attention should be paid to it.展开更多
Ten series of aromatic hydrocarbon compounds (biphenyl, naphthalene, phenanthrene, anthracene, retene, chrysene, benzoanthracene, dibenzofuran, fluorene, dibenzothiophene) isolated from seven Triassic and Jurassic lac...Ten series of aromatic hydrocarbon compounds (biphenyl, naphthalene, phenanthrene, anthracene, retene, chrysene, benzoanthracene, dibenzofuran, fluorene, dibenzothiophene) isolated from seven Triassic and Jurassic lacustrine mudstone samples and three swamp coal samples, as well as five crude oil samples collected in the Kuche depression of the Tarim Basin, NW China, have been analysed by GC-MS techniques. It is found that the relative abundances of dibenzofuran series are higher in the three swamp coal samples than those in the lacustrine mudstone samples. Based on the similar relative abundances of dibenzofuran series, especially dibenzofuran compound, in the TICs of aromatic hydrocarbons, crude oils from wells SA3 (K), YTK5 (E, K) and QL1 (E) are thought to have been derived predominantly from the coals of the Lower Jurassic Yangxia Formation or Middle Jurassic Kezilenuer Formation, whereas those from wells YM7 (O) and YH1 (E) were derived mainly from Triassic and Jurassic lacustrine mudstones in the Kuche depression. This is the first report about how to distinguish coal-generated oils from lacustrine mudstone-generated oils in the Kuche depression in terms of the dibenzofuran series. The present paper has enlightening and directive significance for further oil-source rock correlations and oil and/or gas exploration in the Kuche depression of the Tarim Basin.展开更多
Understanding the origins of potential source rocks and unraveling the intricate connections between reservoir oils and their source formations in the Siwa Basin(Western Desert,Egypt)necessitate a thorough oil-source ...Understanding the origins of potential source rocks and unraveling the intricate connections between reservoir oils and their source formations in the Siwa Basin(Western Desert,Egypt)necessitate a thorough oil-source correlation investigation.This objective is achieved through a meticulous analysis of well-log responses,Rock-Eval pyrolysis,and biomarker data.The analysis of Total Organic Carbon across 31 samples representing Paleozoic formations in the Siwa A-1X well reveals a spectrum of organic richness ranging from 0.17 wt%to 2.04 wt%,thereby highlighting diverse levels of organic content and the presence of both Type II and Type III kerogen.Examination of the fingerprint characteristics of eight samples from the well suggests that the Dhiffah Formation comprises a blend of terrestrial and marine organic matter.Notably,a significant contribution from more oxidized residual organic matter and gas-prone Type III kerogen is observed.Contrarily,the Desouky and Zeitoun formations exhibit mixed organic matter indicative of a transitional environment,and thus featuring a pronounced marine influence within a more reducing setting,which is associated with Type II kerogen.Through analysis of five oil samples from different wells—SIWA L-1X,SIWA R-3X,SIWA D-1X,PTAH 5X,and PTAH 6X,it is evident that terrestrial organic matter,augmented by considerable marine input,was deposited in an oxidizing environment,and contains Type III kerogen.Geochemical scrutiny confirms the coexistence of mixed terrestrial organic matter within varying redox environments.Noteworthy is the uniformity of identified kerogen Types II and III across all samples,known to have potential for hydrocarbon generation.The discovery presented in this paper unveils captivating prospects concerning the genesis of oil in the Jurassic Safa reservoir,suggesting potential links to Paleozoic sources or even originating from the Safa Member itself.These revelations mark a substantial advancement in understanding source rock dynamics and their intricate relationship with reservoir oils within the Siwa Basin.By illuminating the processes of hydrocarbon genesis in the region,this study significantly enriches our knowledge base.展开更多
The deformation field around sub-cracks was calculated using the digital speckle correlation method. First, the uni-axial compression tests on sandstone samples containing a pre- fabricated fracture were made. Photomi...The deformation field around sub-cracks was calculated using the digital speckle correlation method. First, the uni-axial compression tests on sandstone samples containing a pre- fabricated fracture were made. Photomicrographs showing the characteristics of the sub-crack development were taken using a scanning electron microscope （SEM）. From these photomicrographs, the real-time images showing the initiation, growth and coalescence of sub-cracks and micro-cracks in the sandstone specimens were obtained and the effects of loading level as well as grain boundaries on the development of cracks were analyzed. Second, the intensity images of the sandstone specimen surface were captured from the observations of the SEM corresponding to different loading levels. Then correlation computation was carried out for the sequential pairs of intensity images to evaluate the displacement components, as well as the strain field. The results show that the deformation varies in different areas separated by sub-cracks during rock damage processes.展开更多
1 Introduction Stratigraphic correlation is the most important basic work in oil and gas exploration and development,Scientific and reasonable stratigraphic correlation is the premise of developing fine reservoir desc...1 Introduction Stratigraphic correlation is the most important basic work in oil and gas exploration and development,Scientific and reasonable stratigraphic correlation is the premise of developing fine reservoir description,and it is展开更多
Although earthquake lights have been known since ancient times,it has not been easy to study them.It was not until the 60s that the first photographs of them were taken.During the Peruvian earthquake in 2007,it was po...Although earthquake lights have been known since ancient times,it has not been easy to study them.It was not until the 60s that the first photographs of them were taken.During the Peruvian earthquake in 2007,it was possible to obtain the fi rst fi lm recording on earthquake lights.Likewise,during the earthquakes in Ecuador in 2016 and in Mexico in 2017,two fi lms of the earthquake lights were recorded.These fi lm recordings have helped in the study of earthquake lights,both for their objectivity and for their informational content.Several causal mechanisms have been proposed to explain earthquake lights:piezoelectricity,radon emanation,fluid diffusion,friction-vaporization,positive holes and dipole currents,among others.In this work a time difference correlation between earthquake lights and seismic ground accelerations was found and we use both seismic data and fi lm recordings of earthquake lights to explain its origin.In the discussion section it is suggested that fracturing of rocks manifest itself to some extent in the form of static electricity producing earthquake lights through induction The induction model proposed is new and it can explain the formation of EQL,even if the earth’s crust has layers of large electrical resistivity.The model also explains the formation of seismic lights without the need for special conditions on the earth’s surface or in the atmosphere.A better understanding of the earthquake lights generation process can improve our understanding of seismicity and help in the prediction of earthquakes.展开更多
The overall heat transfer coefficient(OHTC)of rock fractures is a fundamental parameter for characterizing the heat transfer behavior of rock fractures in hot dry rock(HDR)geothermal mining.Although a number of practi...The overall heat transfer coefficient(OHTC)of rock fractures is a fundamental parameter for characterizing the heat transfer behavior of rock fractures in hot dry rock(HDR)geothermal mining.Although a number of practical formulae for heat transfer coefficients have been developed in the literature,there is still no widely accepted analytical solution.This paper constructs highly accurate analytical solutions for the temperatures of the inner fracture wall and the fluid.Then they are employed to develop new definition-based formulae(formula A and its simplification formula B)of the OHTC,which are well validated by the experimental and numerical simulation results.An empirical correlation formula of heat transfer coefficient is proposed based on the definition-based formulae which can be directly used in the numerical simulations of heat transfer in rock fractures.A site-scale application example of numerical simulation also demonstrates the effectiveness of the empirical correlation formula.展开更多
The microstructure and fabric of rocks largely control their mechanical behavior,and their spatial variations can lead to anisotropic behavior.Metamorphic rocks such as gneiss exhibit anisotropy,and characterizing thi...The microstructure and fabric of rocks largely control their mechanical behavior,and their spatial variations can lead to anisotropic behavior.Metamorphic rocks such as gneiss exhibit anisotropy,and characterizing this anisotropy is crucial in geoscientific and engineering applications including geothermal plays,active fault zones,and mining sites.We investigate a foliated gneiss from the French River area of the Canadian Shield to determine its mechanical properties and assess the impact of anisotropy across different scales.We combined micro-scale experiments(e.g.nanoindentation and optical and electron microscopy),with meso-scale experiments(e.g.unconfined compressive strength(UCS)and indirect tensile test),to attempt bridging the micro-to meso-scale elastic property gap.Our results show that micro-and meso-mechanical properties of gneiss are orientation-dependent across scales.Young's modulus,upscaled from nanoindentation testing,varied between 51 GPa and 74 GPa,while meso-scale Young's modulus from UCS tests varied between 45 GPa and 54 GPa.The ultrasonic velocities(P-and S-wave)exhibited anisotropy of 26%and 24%,respectively,while the estimated UCS anisotropy was 30%,with the highest values observed in the direction parallel to the foliation.The direction of the mineral alignment forming the foliation plane plays a crucial role in determining the failure pattern of the rock.We observed predominantly tensile failure in samples with 0°–15°foliation plane angle,shear-slip failure for samples with 20°–65°,and a conjugate shear failure in the sample at 90°foliation plane angle to the loading direction.These findings provide insight into the anisotropic(orientation-dependent)characterization of foliated metamorphic rocks,which can be useful in rock engineering applications and numerical simulations.展开更多
The destabilization of overhanging rock is a dangerous geological problem.In this study,a generalized model of typical overhanging cliffs from the Three Gorges Reservoir area in China with different fracture angles,fr...The destabilization of overhanging rock is a dangerous geological problem.In this study,a generalized model of typical overhanging cliffs from the Three Gorges Reservoir area in China with different fracture angles,fracture lengths,and free surface depths is constructed to investigate the cracking and deformation behavior of overhanging rocks.Laboratory tests and deformation field monitoring using the digital image correlation(DIC)method are performed on these specimens to reproduce the destabilization and failure process of overhanging rock under external loading.The influence of peak load is found to be the most sensitive to the fracture length,followed by the free surface depth,and to be the least sensitive to the fracture angle.The DIC-based strain fields reveal that the fracture angle and free surface depth significantly alter the crack propagation paths,whereas the influence of the fracture length is weaker.These parameters also affect the crack initiation time.The relative displacement evolution characteristics indicate that fracture angle,fracture length,and free surface depth affect the shape and size of the rotating block,the rotation center,and the rotation pivot point and degree,respectively.The grayscale characteristic evolution trends are similar for all examined overhanging rock specimens.The evolution of the grayscale indices based on DIC can be divided into high-frequency oscillation,smooth decline(or smooth downward concavity),and stable development stages.Furthermore,the multistage properties of the indices can be used to identify the fracture state of overhanging rocks,providing a theoretical basis for graded early warning of rockfall disasters.展开更多
基金supported by the grants from the National Natural Science Foundation of China(grant nos.41902153,42072140,42102133 and 42202170)Natural Science Foundation Project of Chongqing(grant nos.cstc2021jcyj-msxmX0455,CSTB2022NSCQ-JQX0031 and CSTB2022NSCQ-MSX1586)Science and Technology Research Program of Chongqing Municipal Education Commission(grant nos.KJQN202101544,KJZD-M202101502).
文摘Uncertainties about natural gas source and hydrocarbon accumulation seriously restrict oil and gas exploration in the Lianggaoshan Formation(J_(2) l)in the Eastern Sichuan Basin,which has demonstrated great exploration potential in recent years.This study determines the origin of natural gas and the hydrocarbon accumulation model of J_(2) l in the Eastern Sichuan Basin.A new sample pretreatment method named gas purge-microsyringe extraction was employed and confi rmed to be a practical and eff ective method for preparing condensate oil and collecting source rock extract samples.The source rocks of J_(2) l exhibited moderate to good qualities,characterized by high TOC values,dominance of type Ⅱ_(1) and Ⅱ_(2) kerogens,and high thermal maturities.Biomarker and aromatic characteristics revealed that the source rocks of J_(2) l were deposited in brackish water with weak anoxic conditions.The natural gas in J_(2) l was an organic thermogenic gas generated from the secondary cracking of crude oil,indicating that this natural gas was mainly derived from the source rocks of J_(2) l.The condensate oil-source rock correlation further confi rmed the accuracy of the gas-source correlation results.Based on burial,thermal and hydrocarbon-generating histories,two hydrocarbon charging periods(141–133 Ma and 119–112 Ma)and four hydrocarbon accumulation periods of J_(2) l were determined.Combined with structural evolution,depositional histories and reservoir conditions,a simple gas reservoir accumulation model of J_(2) l was developed,which was identifi ed as a“self-generating and self-storing”gas reservoir.
基金supported by grants from the Research Grants Council of the Hong Kong,Special Administrative Region,China [Project No.9042172 (CityU11200115)and Project No.8779012(T22-603/15N)]
文摘Cohesion(c) and friction angle(φ) of rock are important parameters required for reliability analysis of rock slope stability. There is correlation between c and φ which affects results of reliability analysis of rock slope stability. However, the characterization of joint probability distribution of c and φ through which their correlation can be estimated requires a large amount of rock property data, which are often not available for most rock engineering projects. As a result, the correlation between c and φ is often ignored or simply assumed during reliability studies, which may lead to bias estimation of failure probability. In probabilistic rock slope stability analysis, the influence of ignoring or simply assuming the correlation of the rock strength parameters(i.e., c and φ) on the reliability of rock slopes has not been fully investigated. In this study, a Bayesian approach is developed to characterize the correlation between c and φ, and an expanded reliability-based design(RBD) approach is developed to assess the influence of correlation between c and φ on reliability of a rock slope. The Bayesian approach characterizes the sitespecific joint probability distribution of c and φ, and quantifies the correlation between c and φ using available limited data pairs of c and φ from a rock project. The expanded RBD approach uses the joint probability distribution of c and φ obtained through the Bayesian approach as inputs, to determine the reliability of a rock slope. The approach gives insight into the propagation of the correlation between c and φ through their joint probability into the reliability analysis, and their influence on the calculated reliability of the rock slope. The approaches may be applied in practice with little additional effort from a conventional analysis. The proposed approaches are illustrated using real c and φ data pairs obtained from laboratory tests of fractured rock at Forsmark, Sweden.
基金supported by the National Basic Research 973 Program of China (Grant 2014CB046905)the Natural Science Foundation of Jiangsu Province for Distinguished Young Scholars (Grant BK20150005)+1 种基金the Fundamental Research Funds for the Central Universities (China University of Mining and Technology) (Grant 2014XT03)the innovation research project for academic graduate of Jiangsu Province (Grant KYLX16_0536)
文摘In this paper, uniaxial compression tests were carried out on a series of composite rock specimens with different dip angles, which were made from two types of rock-like material with different strength. The acoustic emission technique was used to monitor the acoustic signal characteristics of composite rock specimens during the entire loading process. At the same time, an optical non-contact 3 D digital image correlation technique was used to study the evolution of axial strain field and the maximal strain field before and after the peak strength at different stress levels during the loading process. The effect of bedding plane inclination on the deformation and strength during uniaxial loading was analyzed. The methods of solving the elastic constants of hard and weak rock were described. The damage evolution process, deformation and failure mechanism, and failure mode during uniaxial loading were fully determined. The experimental results show that the θ = 0?–45?specimens had obvious plastic deformation during loading, and the brittleness of the θ = 60?–90?specimens gradually increased during the loading process. When the anisotropic angle θincreased from 0?to 90?, the peak strength, peak strain,and apparent elastic modulus all decreased initially and then increased. The failure mode of the composite rock specimen during uniaxial loading can be divided into three categories:tensile fracture across the discontinuities(θ = 0?–30?), slid-ing failure along the discontinuities(θ = 45?–75?), and tensile-split along the discontinuities(θ = 90?). The axial strain of the weak and hard rock layers in the composite rock specimen during the loading process was significantly different from that of the θ = 0?–45?specimens and was almost the same as that of the θ = 60?–90?specimens. As for the strain localization highlighted in the maximum principal strain field, the θ = 0?–30?specimens appeared in the rock matrix approximately parallel to the loading direction,while in the θ = 45?–90?specimens it appeared at the hard and weak rock layer interface.
基金This study is funded by the Natural Science Research Council of China (973 State Key Research and Development Program 2006CB202308)National Natural Science Foundation of China (Grant No.40973031)
文摘The origin of the marine oils in the Tarim Basin has long been a disputed topic. A total of 58 DST （drill stem test） crude oil and 8 rock samples were investigated using a comprehensive geochemical method to characterize and identify the origin of the Ordovician oils in the Tazhong Uplift, Tarim Basin, northwest China. Detailed oil–oil and oil–source rock correlations show that the majority of the oils have typical biomarker characteristics of the Middle-Upper Ordovician （O2＋3） source rock and the related crude oil. These characteristics include a distinct ＂V-shaped＂ relative abundance of C27, C28 and C29 regular steranes, low abundance of dinosterane, 24-norcholestanes, triaromatic dinosteroids and gammacerane. Only a few oils display typical biomarker characteristics indicating the Cambrian–Lower Ordovician （∈-O1） genetic affinity, such as linear or anti ＂L＂ shape distribution of C27, C28 and C29 regular sterane, with relatively high concentrations of dinosterane, 24-norcholestanes, triaromatic dinosteroids and gammacerane. It appears that most of the Ordovician oils in the Tazhong Uplift were derived from the O2＋3 intervals, as suggested by previous studies. However, the compound specific n-alkane stable carbon isotope data indicate that the Ordovician oils are mixtures from both the ∈-O1 and O2＋3 source rocks rather than from the O2＋3 strata alone. It was calculated that the proportion of the∈-O1 genetic affinity oils mixed is about 10.8%-74.1%, with an increasing trend with increasing burial depth. This new oil-mixing model is critical for understanding hydrocarbon generation and accumulation mechanisms in the region, and may have important implications for further hydrocarbon exploration in the Tarim Basin.
基金financially supported by the National Natural Science Foundation of China (No.51934003)the Major Science and Technology Special Project of Yunnan Province,China(Nos.202102AF080001 and 202102AG050024)。
文摘The anisotropy induced by rock bedding structures is usually manifested in the mechanical behaviors and failure modes of rocks.Brazilian tests are conducted for seven groups of shale specimens featuring different bedding angles. Acoustic emission (AE) and digital image correlation (DIC) technologies are used to monitor the in-situ failure of the specimens. Furthermore, the crack morphology of damaged samples is observed through scanning electron microscopy (SEM). Results reveal the structural dependence on the tensile mechanical behavior of shales. The shale disk exhibits compression in the early stage of the experiment with varying locations and durations. The location of the compression area moves downward and gradually disappears when the bedding angle increases. The macroscopic failure is well characterized by AE event location results, and the dominant frequency distribution is related to the bedding angle. The b-value is found to be stress-dependent.The crack turning angle between layers and the number of cracks crossing the bedding both increase with the bedding angle, indicating competition between crack propagations. SEM results revealed that the failure modes of the samples can be classified into three types:tensile failure along beddings with shear failure of the matrix, ladder shear failure along beddings with tensile failure of the matrix, and shear failure along multiple beddings with tensile failure of the matrix.
基金Funded by Plan Projects of Hunan Provincial Science&Technology Department(2014FJ3046)Scientific Research Fund of Hunan Provincial Education Department(No.14A045)+1 种基金National Natural Science Foundation of China(Grant Nos.51434006,51374105 and 51374106)China Postdoctoral Science Foundation 2014M562135)
文摘Aiming at the large deformation and support problems of high-stress and broken-expansion surrounding rock, and taking 1 000 m level roadway of Mine II in Jinchuan as the research object, an investigation on the deformation and damage of roadway surrounding rock and an analysis of its mechanism were carried out. The gray correlation theory was used in support scheme optimization design. First, causes and mechanism of deformation of the 1 000 m horizontal transport channel were analyzed through field investigation, laboratory test and data processing methods. We arguued that poor engineering geological conditions and deep pressure increases were the main factors, and the deformation mechanism was mainly the ground deformation pressure. Second, the gray correlation theory was used to construct supporting optimization decision method in the deep roadway. This method more comprehensively considers various factors, including construction, costs, and supporting material functions. The combined support with pre-stressed anchor cables, shotcrete layer, bolt and metal net was put forward according to the actual roadway engineering characteristics. Finally, 4 support schemes were put forward for new roadways. The gray relational theory was applied to optimizing the supporting method, undertaking technical and economic comparison to obtain the correlation degree, and accordingly the schemes were evaluated. It was concluded as follows： the best was the flexible retaining scheme using the steel strand anchor; the second best was the one using plate anchors on the top and rigid common screw steel bolt on the two sides; the ttiird was; the rigid common screw steel bolt in full section of roadway; and the worst is the planished steel rigid support. The optimized scheme was applied to the 1000 m level of new excavation roadway. The results show that the roadway surrounding rock can reach a stable state after 5 to 6 months monitoring, with a convergence rate less than 1 mm/d.
基金the support of the National Natural Science Foundation of China(Grant Nos.42207199,52179113,42272333)Zhejiang Postdoctoral Scientific Research Project(Grant Nos.ZJ2022155,ZJ2022156)。
文摘Three-dimensional(3D)printing technology is increasingly used in experimental research of geotechnical engineering.Compared to other materials,3D layer-by-layer printing specimens are extremely similar to the inherent properties of natural layered rock masses.In this paper,soft-hard interbedded rock masses with different dip angles were prepared based on 3D printing(3DP)sand core technology.Uniaxial compression creep tests were conducted to investigate its anisotropic creep behavior based on digital imaging correlation(DIC)technology.The results show that the anisotropic creep behavior of the 3DP soft-hard interbedded rock mass is mainly affected by the dip angles of the weak interlayer when the stress is at low levels.As the stress level increases,the effect of creep stress on its creep anisotropy increases significantly,and the dip angle is no longer the main factor.The minimum value of the long-term strength and creep failure strength always appears in the weak interlayer within 30°–60°,which explains why the failure of the layered rock mass is controlled by the weak interlayer and generally emerges at 45°.The tests results are verified by comparing with theoretical and other published studies.The feasibility of the 3DP soft-hard interbedded rock mass provides broad prospects and application values for 3DP technology in future experimental research.
基金supported by the Fundamental Research Funds for the Central Universities(Grant No.20CX02108A)the Development Fund of the Key Laboratory of Deep Oil&Gas,China University of Petroleum(East China)。
文摘The origin and source of the petroleum in the Jurassic reservoirs within the eastern Fukang sub-depression were geochemically investigated.They show thermal maturities matching the peak generation stage,while the condensates are at the early stage of intense cracking.Oils and condensates may have experienced mild evaporative fractionation,while mixing of severely biodegraded with non-biodegraded oils has occurred.Using biomarkers and isotopes,petroleums were classified into GroupⅠ,ⅡandⅢgenetic groups,with GroupⅢfurther divided intoⅢa andⅢb subgroups.GroupⅠpetroleum displays heavy carbon isotopes,a strong predominance of pristine over phytane,high C_(19)and C_(20)tricyclic and C_(24)tetracyclic terpanes,low gammacerane,and dominant C_(29)steranes,while GroupⅡshows light carbon isotopes,a predominance of phytane over pristine,high C_(21)and C_(23)tricyclic with low C_(24)tetracyclic terpanes,high gammacerane and dominant C_(27)steranes.GroupⅢa petroleum shows mixing compositions of GroupⅠandⅡ,while GroupⅢb displays similar compositions to Group I,but with significantly higher Ts,C_(29)Ts and C_(30)diahopane proportions.Oil-source rock correlation suggests GroupⅠandⅡpetroleums originate from Jurassic and Permian source rocks,respectively,while GroupⅢa are mixtures sourced from these rocks andⅢb are mixtures from Jurassic and Triassic source rocks.
文摘This study considers the Upper Cretaceous Qingshankou Formation,Yaojia Formation,and the first member of the Nenjiang Formation in the Western Slope of the northern Songliao Basin.Dark mudstone with high abundances of organic matter of Gulong and Qijia sags are considered to be significant source rocks in the study area.To evaluate their development characteristics,differences and effectiveness,geochemical parameters are analyzed.One-dimensional basin modeling and hydrocarbon evolution are also applied to discuss the effectiveness of source rocks.Through the biomarker characteristics,the source–source,oil–oil,and oil–source correlations are assessed and the sources of crude oils in different rock units are determined.Based on the results,Gulong and Qijia source rocks have different organic matter primarily detrived from mixed sources and plankton,respectively.Gulong source rock has higher thermal evolution degree than Qijia source rock.The biomarker parameters of the source rocks are compared with 31 crude oil samples.The studied crude oils can be divided into two groups.The oil–source correlations show that group I oils from Qing II–III,Yao I,and Yao II–III members were probably derived from Gulong source rock and that only group II oils from Nen I member were derived from Qijia source rock.
文摘Studied forecasting and controlling the blasting fragmentation by using artifi- cial neural network for multi-ingredients. At the same time, according to the characteris- tic of multi-parameters input to network model, the gray correlation theory was employed to find out key factors, which can not only save time of computation and parameters in- put, but improve the stability of the model.
文摘In the future time the exploration of marine oil and gas will be one of the significant domains in China. In this paper the biomarker assemblage characteristics of oilshow in the Nanlinghu Formation of the Majiashan pro- file, which is located in Chaoxian County, south of Anhui Province, are described in the light of gas chromatogra- phy/mass spectrometric (GCMS) analysis on the qualitative and quantitative basis. Based on the investigation of the biomarker assemblage characteristics of possible source rocks developed in the area studied, a conclusion is drawn that the oilshow was generated from the Nanlinghu Formation source rocks (abbreviated as T1n), instead of the Qixia Formation source rocks (abbreviated as P1q). It is pointed out that the T1n is of strong potential for future oil explora- tion, and therefore much attention should be paid to it.
文摘Ten series of aromatic hydrocarbon compounds (biphenyl, naphthalene, phenanthrene, anthracene, retene, chrysene, benzoanthracene, dibenzofuran, fluorene, dibenzothiophene) isolated from seven Triassic and Jurassic lacustrine mudstone samples and three swamp coal samples, as well as five crude oil samples collected in the Kuche depression of the Tarim Basin, NW China, have been analysed by GC-MS techniques. It is found that the relative abundances of dibenzofuran series are higher in the three swamp coal samples than those in the lacustrine mudstone samples. Based on the similar relative abundances of dibenzofuran series, especially dibenzofuran compound, in the TICs of aromatic hydrocarbons, crude oils from wells SA3 (K), YTK5 (E, K) and QL1 (E) are thought to have been derived predominantly from the coals of the Lower Jurassic Yangxia Formation or Middle Jurassic Kezilenuer Formation, whereas those from wells YM7 (O) and YH1 (E) were derived mainly from Triassic and Jurassic lacustrine mudstones in the Kuche depression. This is the first report about how to distinguish coal-generated oils from lacustrine mudstone-generated oils in the Kuche depression in terms of the dibenzofuran series. The present paper has enlightening and directive significance for further oil-source rock correlations and oil and/or gas exploration in the Kuche depression of the Tarim Basin.
基金the research project is funded by Abdullah Alrushaid Chair for Earth Science Remote Sensing Research at King Saud University,Riyadh,Saudi Arabia.。
文摘Understanding the origins of potential source rocks and unraveling the intricate connections between reservoir oils and their source formations in the Siwa Basin(Western Desert,Egypt)necessitate a thorough oil-source correlation investigation.This objective is achieved through a meticulous analysis of well-log responses,Rock-Eval pyrolysis,and biomarker data.The analysis of Total Organic Carbon across 31 samples representing Paleozoic formations in the Siwa A-1X well reveals a spectrum of organic richness ranging from 0.17 wt%to 2.04 wt%,thereby highlighting diverse levels of organic content and the presence of both Type II and Type III kerogen.Examination of the fingerprint characteristics of eight samples from the well suggests that the Dhiffah Formation comprises a blend of terrestrial and marine organic matter.Notably,a significant contribution from more oxidized residual organic matter and gas-prone Type III kerogen is observed.Contrarily,the Desouky and Zeitoun formations exhibit mixed organic matter indicative of a transitional environment,and thus featuring a pronounced marine influence within a more reducing setting,which is associated with Type II kerogen.Through analysis of five oil samples from different wells—SIWA L-1X,SIWA R-3X,SIWA D-1X,PTAH 5X,and PTAH 6X,it is evident that terrestrial organic matter,augmented by considerable marine input,was deposited in an oxidizing environment,and contains Type III kerogen.Geochemical scrutiny confirms the coexistence of mixed terrestrial organic matter within varying redox environments.Noteworthy is the uniformity of identified kerogen Types II and III across all samples,known to have potential for hydrocarbon generation.The discovery presented in this paper unveils captivating prospects concerning the genesis of oil in the Jurassic Safa reservoir,suggesting potential links to Paleozoic sources or even originating from the Safa Member itself.These revelations mark a substantial advancement in understanding source rock dynamics and their intricate relationship with reservoir oils within the Siwa Basin.By illuminating the processes of hydrocarbon genesis in the region,this study significantly enriches our knowledge base.
基金supported by the NaturalScience Foundation of China(contract no.40821062)
文摘The deformation field around sub-cracks was calculated using the digital speckle correlation method. First, the uni-axial compression tests on sandstone samples containing a pre- fabricated fracture were made. Photomicrographs showing the characteristics of the sub-crack development were taken using a scanning electron microscope （SEM）. From these photomicrographs, the real-time images showing the initiation, growth and coalescence of sub-cracks and micro-cracks in the sandstone specimens were obtained and the effects of loading level as well as grain boundaries on the development of cracks were analyzed. Second, the intensity images of the sandstone specimen surface were captured from the observations of the SEM corresponding to different loading levels. Then correlation computation was carried out for the sequential pairs of intensity images to evaluate the displacement components, as well as the strain field. The results show that the deformation varies in different areas separated by sub-cracks during rock damage processes.
基金the National Natural Science Foundation of China(Grant No. 41172106) for financial support of this work
文摘1 Introduction Stratigraphic correlation is the most important basic work in oil and gas exploration and development,Scientific and reasonable stratigraphic correlation is the premise of developing fine reservoir description,and it is
文摘Although earthquake lights have been known since ancient times,it has not been easy to study them.It was not until the 60s that the first photographs of them were taken.During the Peruvian earthquake in 2007,it was possible to obtain the fi rst fi lm recording on earthquake lights.Likewise,during the earthquakes in Ecuador in 2016 and in Mexico in 2017,two fi lms of the earthquake lights were recorded.These fi lm recordings have helped in the study of earthquake lights,both for their objectivity and for their informational content.Several causal mechanisms have been proposed to explain earthquake lights:piezoelectricity,radon emanation,fluid diffusion,friction-vaporization,positive holes and dipole currents,among others.In this work a time difference correlation between earthquake lights and seismic ground accelerations was found and we use both seismic data and fi lm recordings of earthquake lights to explain its origin.In the discussion section it is suggested that fracturing of rocks manifest itself to some extent in the form of static electricity producing earthquake lights through induction The induction model proposed is new and it can explain the formation of EQL,even if the earth’s crust has layers of large electrical resistivity.The model also explains the formation of seismic lights without the need for special conditions on the earth’s surface or in the atmosphere.A better understanding of the earthquake lights generation process can improve our understanding of seismicity and help in the prediction of earthquakes.
基金support of this work by the National Natural Science Foundation of China (Grant Nos.41972316 and 41672252).
文摘The overall heat transfer coefficient(OHTC)of rock fractures is a fundamental parameter for characterizing the heat transfer behavior of rock fractures in hot dry rock(HDR)geothermal mining.Although a number of practical formulae for heat transfer coefficients have been developed in the literature,there is still no widely accepted analytical solution.This paper constructs highly accurate analytical solutions for the temperatures of the inner fracture wall and the fluid.Then they are employed to develop new definition-based formulae(formula A and its simplification formula B)of the OHTC,which are well validated by the experimental and numerical simulation results.An empirical correlation formula of heat transfer coefficient is proposed based on the definition-based formulae which can be directly used in the numerical simulations of heat transfer in rock fractures.A site-scale application example of numerical simulation also demonstrates the effectiveness of the empirical correlation formula.
基金funded by the Natural Sciences and Engineering Research Council of Canada(NSERC)Discovery Grants(Grant No.341275)the NSERC/Energi Simulation Industrial Research Chair program,and State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Open Fund(Grant No.SKLGP2024K001).
文摘The microstructure and fabric of rocks largely control their mechanical behavior,and their spatial variations can lead to anisotropic behavior.Metamorphic rocks such as gneiss exhibit anisotropy,and characterizing this anisotropy is crucial in geoscientific and engineering applications including geothermal plays,active fault zones,and mining sites.We investigate a foliated gneiss from the French River area of the Canadian Shield to determine its mechanical properties and assess the impact of anisotropy across different scales.We combined micro-scale experiments(e.g.nanoindentation and optical and electron microscopy),with meso-scale experiments(e.g.unconfined compressive strength(UCS)and indirect tensile test),to attempt bridging the micro-to meso-scale elastic property gap.Our results show that micro-and meso-mechanical properties of gneiss are orientation-dependent across scales.Young's modulus,upscaled from nanoindentation testing,varied between 51 GPa and 74 GPa,while meso-scale Young's modulus from UCS tests varied between 45 GPa and 54 GPa.The ultrasonic velocities(P-and S-wave)exhibited anisotropy of 26%and 24%,respectively,while the estimated UCS anisotropy was 30%,with the highest values observed in the direction parallel to the foliation.The direction of the mineral alignment forming the foliation plane plays a crucial role in determining the failure pattern of the rock.We observed predominantly tensile failure in samples with 0°–15°foliation plane angle,shear-slip failure for samples with 20°–65°,and a conjugate shear failure in the sample at 90°foliation plane angle to the loading direction.These findings provide insight into the anisotropic(orientation-dependent)characterization of foliated metamorphic rocks,which can be useful in rock engineering applications and numerical simulations.
基金supported by the China National Natural Science Foundation(Grant No.42362034)the Applied Basic Research Foundation of Yunnan Province,China(Grant No.202401AS070068).
文摘The destabilization of overhanging rock is a dangerous geological problem.In this study,a generalized model of typical overhanging cliffs from the Three Gorges Reservoir area in China with different fracture angles,fracture lengths,and free surface depths is constructed to investigate the cracking and deformation behavior of overhanging rocks.Laboratory tests and deformation field monitoring using the digital image correlation(DIC)method are performed on these specimens to reproduce the destabilization and failure process of overhanging rock under external loading.The influence of peak load is found to be the most sensitive to the fracture length,followed by the free surface depth,and to be the least sensitive to the fracture angle.The DIC-based strain fields reveal that the fracture angle and free surface depth significantly alter the crack propagation paths,whereas the influence of the fracture length is weaker.These parameters also affect the crack initiation time.The relative displacement evolution characteristics indicate that fracture angle,fracture length,and free surface depth affect the shape and size of the rotating block,the rotation center,and the rotation pivot point and degree,respectively.The grayscale characteristic evolution trends are similar for all examined overhanging rock specimens.The evolution of the grayscale indices based on DIC can be divided into high-frequency oscillation,smooth decline(or smooth downward concavity),and stable development stages.Furthermore,the multistage properties of the indices can be used to identify the fracture state of overhanging rocks,providing a theoretical basis for graded early warning of rockfall disasters.
