Evaluating the characteristics of geological structures in karst groundwater inflow, Nowsud Tunnel

Highly permeable geological structures such as dissolution channels, open fractures, and faults create environmental challenges regard to hydrological and hydrogeological aspects of underground construction, often causing significant groundwater inflow during drilling due to the limitations of empirical and analytical methods. This study aims to identify the geological factors influencing water flow into the tunnel. High-flow zones' geological features have been identified and examined for this purpose. According to the geological complexity of the Nowsud tunnel, presence of different formations with different permeability and karstification have led to a high volume of underground inflow water (up to 4700 L/s) to the tunnel. The Nowsud tunnel faces significant geological and hydrogeological challenges due to its passage through the Ilam formation's LI2 unit, characterized by dissolution channels, faults, and fractures. The highest inflow rate (4700 L/s) occurred in the Hz-9 zone within the Zimkan anticline. The relationship between geological features and groundwater inflow indicates that anticlines are more susceptible to inflow than synclines. Additionally, different types of faults exhibit varying hydraulic effects, with strike-slip faults having the most significant impact on groundwater inflow, thrust faults conducting less water into the tunnel, and inflow through normal faults being negligible compared to the other two types of faults. The novelty of this paper lies in its detailed analysis of geological features influencing groundwater inflow into the Nowsud tunnel, providing empirical data on high-flow zones and differentiating the hydraulic effects of various fault types, which enhances the understanding and prediction of groundwater inflow in underground constructions.

Three-dimensional structural models,evolution and petroleum geological significances of transtensional faults in the Ziyang area,central Sichuan Basin,SW China

With drilling and seismic data of Transtensional(strike-slip)Fault System in the Ziyang area of the central Sichuan Basin,SW China plane-section integrated structural interpretation,3-D fault framework model building,fault throw analyzing,and balanced profile restoration,it is pointed out that the transtensional fault system in the Ziyang 3-D seismic survey consists of the northeast-trending F_(I)19 and F_(I)20 fault zones dominated by extensional deformation,as well as 3 sets of northwest-trending en echelon normal faults experienced dextral shear deformation.Among them,the F_(I)19 and F_(I)20 fault zones cut through the Neoproterozoic to Lower Triassic Jialingjiang Formation,presenting a 3-D structure of an“S”-shaped ribbon.And before Permian and during the Early Triassic,the F_(I)19 and F_(I)20 fault zones underwent at least two periods of structural superimposition.Besides,the 3 sets of northwest-trending en echelon normal faults are composed of small normal faults arranged in pairs,with opposite dip directions and partially left-stepped arrangement.And before Permian,they had formed almost,restricting the eastward growth and propagation of the F_(I)19 fault zone.The F_(I)19 and F_(I)20 fault zones communicate multiple sets of source rocks and reservoirs from deep to shallow,and the timing of fault activity matches well with oil and gas generation peaks.If there were favorable Cambrian-Triassic sedimentary facies and reservoirs developing on the local anticlinal belts of both sides of the F_(I)19 and F_(I)20 fault zones,the major reservoirs in this area are expected to achieve breakthroughs in oil and gas exploration.

Research on in situ stress inversion of deep-buried tunnel based on pressure/tension axis mechanism and geological structure

The investigation of the in situ stress distribution has always been a key condition for engineering design of deep tunnels and analysis of surrounding rock stability.In this paper,a comprehensive judgment method coupled with pressure/tension(P/T)axis mechanism and geological structure is proposed to invert the in situ stress in the Duoxiongla tunnel in Tibet.In the process of TBM tunnel excavation,3887 groups of microseismic events were collected by means of microseismic monitoring technology.By studying the temporal and spatial distribution of 3887 groups of microseismic events,42 groups of microseismic data were selected for in situ stress inversion.Then the focal mechanisms of 42 groups of microseisms were inverted.Combined with the analysis of the previous geological survey,the inversion results of the in situ stress were analyzed.According to the focal mechanism of the tunnel area,the linear in situ stress inversion method was used to invert the in situ stress in the source area.Finally,according to the PTGS(pressure/tension axis mechanism and geological structure)comprehensive judgment method proposed in this paper,the in situ stress of the tunnel microseismic region was determined.The results show that there are mainly three groups of fissures and joint surfaces in the tunnel area,and the in situ stress is dominated by the horizontrun tectonic stress;the main driving force of the rupture surface in the excavation process of Duoxiongla tunnel is the horizontal tectonic stress;the distribution of the maximum and minimum principal stress obtained by the inversion is consistent with the distribution of the P/T axis;combined with the linear in situ stress inversion method and the comprehensive judgment of PTGS,the azimuth and dip angles of the three principal stresses are finally determined as N90.71°E,4.06°,N5.35°W,3.06°,and N8.10W,85.32°,respectively.The study verifies the feasibility of microseismic inversion of in situ stress.

Modularized and Parametric Modeling Technology for Finite Element Simulations of Underground Engineering under Complicated Geological Conditions

The surrounding geological conditions and supporting structures of underground engineering are often updated during construction,and these updates require repeated numerical modeling.To improve the numerical modeling efficiency of underground engineering,a modularized and parametric modeling cloud server is developed by using Python codes.The basic framework of the cloud server is as follows:input the modeling parameters into the web platform,implement Rhino software and FLAC3D software to model and run simulations in the cloud server,and return the simulation results to the web platform.The modeling program can automatically generate instructions that can run the modeling process in Rhino based on the input modeling parameters.The main modules of the modeling program include modeling the 3D geological structures,the underground engineering structures,and the supporting structures as well as meshing the geometric models.In particular,various cross-sections of underground caverns are crafted as parametricmodules in themodeling program.Themodularized and parametric modeling program is used for a finite element simulation of the underground powerhouse of the Shuangjiangkou Hydropower Station.This complicatedmodel is rapidly generated for the simulation,and the simulation results are reasonable.Thus,this modularized and parametric modeling program is applicable for three-dimensional finite element simulations and analyses.

Deformation,structure and potential hazard of a landslide based on InSAR in Banbar county,Xizang(Tibet)

The Tibetan Plateau is characterized by complex geological conditions and a relatively fragile ecological environment.In recent years,there has been continuous development and increased human activity in the Tibetan Plateau region,leading to a rising risk of landslides.The landslide in Banbar County,Xizang(Tibet),have been perturbed by ongoing disturbances from human engineering activities,making it susceptible to instability and displaying distinct features.In this study,small baseline subset synthetic aperture radar interferometry(SBAS-InSAR)technology is used to obtain the Line of Sight(LOS)deformation velocity field in the study area,and then the slope-orientation deformation field of the landslide is obtained according to the spatial geometric relationship between the satellite’s LOS direction and the landslide.Subsequently,the landslide thickness is inverted by applying the mass conservation criterion.The results show that the movement area of the landslide is about 6.57×10^(4)m^(2),and the landslide volume is about 1.45×10^(6)m^(3).The maximum estimated thickness and average thickness of the landslide are 39 m and 22 m,respectively.The thickness estimation results align with the findings from on-site investigation,indicating the applicability of this method to large-scale earth slides.The deformation rate of the landslide exhibits a notable correlation with temperature variations,with rainfall playing a supportive role in the deformation process and displaying a certain lag.Human activities exert the most substantial influence on the spatial heterogeneity of landslide deformation,leading to the direct impact of several prominent deformation areas due to human interventions.Simultaneously,utilizing the long short-term memory(LSTM)model to predict landslide displacement,and the forecast results demonstrate the effectiveness of the LSTM model in predicting landslides that are in a continuous development and movement phase.The landslide is still active,and based on the spatial heterogeneity of landslide deformation,new recommendations have been proposed for the future management of the landslide in order to mitigate potential hazards associated with landslide instability.

Geological characteristics and models of fault-foldfracture body in deep tight sandstone of the second member of Upper Triassic Xujiahe Formation in Xinchang structural belt of Sichuan Basin,SW China

In the second member of the Upper Triassic Xujiahe Formation(T_(3)x_(2))in the Xinchang area,western Sichuan Basin,only a low percent of reserves has been recovered,and the geological model of gas reservoir sweet spot remains unclear.Based on a large number of core,field outcrop,test and logging-seismic data,the T_(3)x_(2) gas reservoir in the Xinchang area is examined.The concept of fault-fold-fracture body(FFFB)is proposed,and its types are recognized.The main factors controlling fracture development are identified,and the geological models of FFFB are established.FFFB refers to faults,folds and associated fractures reservoirs.According to the characteristics and genesis,FFFBs can be divided into three types:fault-fracture body,fold-fracture body,and fault-fold body.In the hanging wall of the fault,the closer to the fault,the more developed the effective fractures;the greater the fold amplitude and the closer to the fold hinge plane,the more developed the effective fractures.Two types of geological models of FFFB are established:fault-fold fracture,and matrix storage and permeability.The former can be divided into two subtypes:network fracture,and single structural fracture,and the later can be divided into three subtypes:bedding fracture,low permeability pore,and extremely low permeability pore.The process for evaluating favorable FFFB zones was formed to define favorable development targets and support the well deployment for purpose of high production.The study results provide a reference for the exploration and development of deep tight sandstone oil and gas reservoirs in China.

Relationship between Geological Structures and Hydrocarbon Enrichment of Different Depressions in the Bohai Bay Basin

The Bohai Bay Basin contains many depressions with varying degrees of hydrocarbon enrichment associated with the geological structures of different depressions. This study discussed the relationship between the geological structures and hydrocarbon enrichment of the depressions in the Bohai Bay Basin. Based on the Paleogene strata distribution and the length to width ratio of different depressions, their geological structures are divided into three types in plan-view： open（length/width 〈 2）, narrow（length/width 〉 4） and transitional types（length/width 2-4）. In cross section, the geological structures can be divided into dustpan I, dustpan II and double-faulted types. Based on tectonic evolution and sedimentary characteristics, the depressions are classified into early-formed, inherited and late-formed categories. Generally, narrow depressions are mainly located in the northeast and southwest of the Bohai Bay Basin, while open depressions are dominantly distributed in the central area of the basin; late-formed depressions are mainly around the Bohai sea area, and early-formed depressions are mostly located in the periphery of the basin. Geological structures of the depressions control the formation of the source, reservoir and cap rocks as well as hydrocarbon accumulation setting, and further influence the pay zones and oil-bearing sequence. In detail, dustpan II and doublefaulted depressions mainly have A-type sags, which often possess better hydrocarbon generation conditions than dustpan I ones; hydrocarbons in open dustpan II depressions tend to accumulate in the central uplift areas or buried hill, while those in narrow dustpan I depressions always accumulate in gentle slope belts. The oil-bearing sequence for different evolutional depressions corresponds well with the sedimentary strata of the main development stages of depressions. In early-formed depressions, hydrocarbons are mainly enriched in deeply buried reservoirs, while in late-formed depressions hydrocarbons are abundant in the relatively shallow traps. In summary, most inherited and late-formed dustpan II depressions are enriched in hydrocarbons due to their extensive source rocks and good source-reservoir-seal assemblages, whereas dustpan I and early-formed depressions are relatively poor in hydrocarbons.

Framework system and research flow of uncertainty in 3D geological structure models

Uncertainty in 3D geological structure models has become a bottleneck that restricts the development and application of 3D geological modeling.In order to solve this problem during periods of accuracy assessment,error detection and dynamic correction in 3D geological structure models,we have reviewed the current situation and development trends in 3D geological modeling.The main context of uncertainty in 3D geological structure models is discussed.Major research issues and a general framework system of uncertainty in 3D geological structure models are proposed.We have described in detail the integration of development practices of 3D geological modeling systems,as well as the implementation process for uncertainty evaluation in 3D geological structure models.This study has laid the basis to build theoretical and methodological systems for accuracy assessment and error correction in 3D geological models and can assist in improving 3D modeling techniques under complex geological conditions.

Geological structures of ridges with relation to the definition of three types of seafloor highs stipulated in Article 76

The ridge like seafloor highs with various geological origins can be classed into mid-ocean ridges,transverse ridges related to transform faults,hot spot/mantle plume originated ridges,microcontinent rifted from major continent,intra-plate arc formed by interaction of two oceanic plates,and tectonic ridges uplifted by later tectonic activity.Those ridges moved towards the convergent continental margins along with the underlain plate drifting and formed so-called accreted ridges commonly trending at a high angle to the continental margins.At divergent continental margins,the continental crusts were extended and thinned accompanying with magmatism,which formed high terrains protruding or parallel to the coastal line.The ridges worldwide have various origins and the crustal thicknesses and structures of them are diversity.The crusts beneath the microcontinents,and the transverse ridges along the transform margin,and the seafloor highs beside the passive continental margins are continental,while the crusts of other ridges are oceanic.Article 76 of the United Nations Convention on the Law of the Sea （UNCLOS） has classed the seafloor highs worldwide into three legal categories,namely oceanic ridges,submarine ridges and submarine elevations,for the purpose to delineate the outer limit of the coastal States＇ continental shelf beyond 200 nautical miles.To define the categories of the legal seafloor highs to which the ridges with various geological origins belong,the continuities in morphology and geology including the rock types,crustal structures,origins and tectonic setting of the ridges and the coastal States＇ land mass with its submerged prolongation should be taken into account.If a ridge is continuous both in morphology and geology with the coastal States＇ land mass and its submerged prolongation,it is a submarine elevation stipulated in Article 76.If it is discontinuous in morphology,the ridge should be regarded as oceanic ridges.If a ridge is continuous in morphology but discontinuous in geology with the coastal States＇ land mass and its submerged prolongation,then it is a submarine ridge as stipulated in Article 76.

Application of four-component dipole shear reflection imaging to interpret the geological structure around a deviated well

Acoustic reflection imaging in deep water wells is a new application scope for offshore hydrocarbon exploration.Two-dimensional(2 D)geological structure images can be obtained away from a one-dimensional(1 D)borehole using single-well acoustic reflection imaging.Based on the directivity of dipole source and four-component dipole data,one can achieve the azimuth detection and the three-dimensional(3 D)structural information around the wellbore can be obtained.We first perform matrix rotation on the field fourcomponent data.Then,a series of processing steps are applied to the rotated dipole data to obtain the reflector image.According to the above dipole shear-wave imaging principle,we used four-component cross-dipole logging data from a deviated well in the South China Sea to image geological structures within 50 m of a deviated well,which can delineate the structural configuration and determine its orientation.The configuration of near-borehole bedding boundaries and fault structures from shear-wave imaging results agrees with those from the Inline and Xline seismic profiles of the study area.In addition,the configuration and orientation of the fault structure images are consistent with regional stress maps and the results of the borehole stress anisotropy analysis.Furthermore,the dip azimuth of the bedding boundary images was determined using borehole wall resistivity data.Results of this study indicate that integrating borehole acoustic reflection with seismic imaging not only fills the gap between the two measurement scales but also accurately delineates geological structures in the borehole vicinity.

Research on Geological Structure Mark of Coal and Gas Outbursts in Pingdingshan Mining Area

Based on the study of regional displaying rules of coal and gas outburst controlled by geological structure in Pingdingshan mining area, the geological structure features in outburst sites were investigated emphatically. The combination type, orientation and least seam thickness in outburst sites were put forward. This research provides a geological mark for forecasting gas outbursts in deep mining.

The geological structure background and the crustal structure in the northeastern margin of the Qinghai-Tibetan plateau

The geological structure background, the crustal structure and the shape of Moho in the northeastern margin of the Qinghai-Tibetan plateau are studied. Based on artificial seismic sounding profile as well as geological data. The main results are summarized as follows: (1) The geotectonic subdivisions and the characteristics of main deep and large faults in the northeastern margin of the Qinghai-Tibetan plateau are presented; (2) The general features of the Moho are obtained mainly based on artificial seismic sounding data; (3) There exists well corresponding relation between surface faults and some features of the Moho, which suggests that such complex crustal structure might be the preparation environment of strong earthquakes.

Construction of Subsurface Geological Structures Using a Drilling Database: A Case Study for an Intra-Arc Basin, the Osaka Plain, Southwest Japan

Subsurface geological cross sections of 0 - 200 m depth were constructed using a dense drilling database of the Osaka Plain in the intra-arc Osaka Basin of the Japan island arc, an active plate margin. The cross sections revealed the subsurface geological structures and the geometry of folding and faulting in the basin. The comparison between the constructed subsurface cross sections and the seismic sections of the basement and basin fills at a depth of 1500 - 2000 m showed that the basement and shallow subsurface structures are similar;however, the shallow cross sections were of higher resolution than the deep seismic profiles.

Interpretation of Geological Structures Hosting Potential Gold Deposits in the Konongo Gold Mine Using Airborne Magnetic, Electromagnetic and Radiometric Datasets

The renewed interest in the reactivation of the defunct National Konongo Gold Mine located in the Ashanti Greenstone Belt, calls for a further probe into its geology and the associated mineral hosting structures to discover its mineralization potential. In order to achieve this, airborne magnetic, radiometric and electromagnetic datasets were interpreted to determine the potential gold hosting features in the studied area. The results show the area to consist of the metasediment, the metavolcanic, Tartwaian Formation and their associated granitoids. Results also show that the Tarkwaian sediments, observed largely in the north-eastern side of the site;widen out substantially and truncate in the south. The analysis of the structure lineaments using a rose diagram reveals three main tectonic structures trending in N-S, NNW-SSE, and third the structure trending in the NNE-SSW to NE-SW directions in the area. The dominant structures in the area, form 90% of all the delineated structures and trend in the NE-SW and NNE-SSW direction with the remaining 10% trending in the N-S and NNW-SSE. These structures are associated with the major shear and fracture zones located mainly at the contact between the basin sediments and volcanic belt and also associated with the Tarkwaian Formation. The mapped potential gold mineralization zones located mainly at the contact between the metasediment and the metavolcanic units of the Birimian Supergroup, as well as the Tarkwaian Formation, were mapped by integrating the structures, alteration zones as well as the complex dyke systems. This paper delineates the prominent geological structures with the potential of hosting economic gold mineralization in and around the Konongo Gold Mine.

Lithostratigraphy, Structure, Geological History, Economic Geology and Paleontology of Mari Bugti Hills and Surrounding Areas of Balochistan, South Punjab and North Sindh (Pakistan)

Mari Bugti hills and surroundings belong to Sulaiman basin (fragment of Gondwana) lies under the territory of Balochistan, South Punjab and North Sindh (Pakistan) but luckily have diverse marine and terrestrial sediments varying in age from Triassic to Recent, petroleum and a large number of mineral resources especially huge gypsum and cement resources, numerous suitable anticlinal structures and world-famous paleontology. The large-sized poripuchian titanosaurs, theropods, mesoeucrocodiles, pterosaur, bird and snake were reported from the latest Cretaceous Vitakri Formation, and largest terrestrial mammals and eucrocodiles were reported from the Oligocene Chitarwata Formation and other mammals were also reported from Late Paleogene and Neogene terrestrial deposits. Previously part of this area was not mapped due to remoteness and security problems but recently the mapping of these areas was started. Further, the structural and geological maps of previously omitted parts are added here. After performing the multidisciplinary field investigations by senior author, the corresponding results were obtained. The main objective of this work is to focus on the lithostratigraphic deposits, structure, geological history, economic geology and paleontology of the Mari Bugti Hills and surrounding areas.

Analysis on geological structures influencing gas occurrence at Qidong coalmine

The occurrence state of methane is mostly controlled by coalfield geologicalstructures.The coal-bearing strata at Qidong coalmine experienced many tectonic cyclessince their formation.The gas content made by the complicated structural geologic systemat the coalfield is very different, which is obviously higher on the north side of the Weimiaofracture belt than that on the south side and near itself.This thesis discussed the gas occurrenceregularity based on the geometric characteristics of the geological structure andits regional tectonic evolution.This study can provide a foundation for coalfield exploitationand deal with coal and gas outburst.

The stress state of geological structure and mining dynamic disaster in Fuxin basin

Further evidences show that most mining dynamic disasters are mainly oc- curred nearby NNE and near SN geological structures.In-situ stress measurement in Fuxin basin shows that the orientation of major compressed stress is near EW.At this stress field,geological structures with deferent strike have deferent stress state and dis- place mode.NNE and near SN geological structures are compressed to thrust and come into being high stress zone.NWW and NEE geological structures are tensile to separate and not prone to being low stress zone.NW structure is intervenient of them.So NEE and near SN structures are easy to occurre mining dynamic disasters and NWW and NEE structures is 'safety' comparatively.The mining dynamic disaster is controlled by stress state of geologic structure,which is determined by its strike.

A DESIGN OF THREE-DIMENSIONAL SPATIAL DATA MODEL AND ITS DATA STRUCTURE IN GEOLOGICAL EXPLORATION ENGINEERING

The key to develop 3-D GISs is the study on 3-D data model and data structure. Some of the data models and data structures have been presented by scholars. Because of the complexity of 3-D spatial phenomenon, there are no perfect data structures that can describe all spatial entities. Every data structure has its own advantages and disadvantages. It is difficult to design a single data structure to meet different needs. The important subject in the3-D data models is developing a data model that has integrated vector and raster data structures. A special 3-D spatial data model based on distributing features of spatial entities should be designed. We took the geological exploration engineering as the research background and designed an integrated data model whose data structures integrats vector and raster data byadopting object-oriented technique. Research achievements are presented in this paper.

Rock bridge slice element method in slope stability analysis based on multi-scale geological structure mapping

The searching method of failure surface which consists of complex geological structures in high and steep rock slopes was studied. Based on computer simulation technology and Monte-Carlo method, three dimensional multi-scale geological structures such as engineering scale and statistical scale structures of the slope were simulated. The searching method of failure route which consists of joints and rock bridges was determined via simulation annealing method by considering the shear strength of joints or rock bridges in one supposed route. When shear strengths of all the supposed routes were computed, the least shear strength route was considered failure route. Then, the inclined slice of joint slices and rock bridge slices were separated according to the position of joints and rock bridges. For the rock bridge slices, by distinguishing the failure model, the force direction to the next slice was defined. Finally, the limit equilibrium equations for every slice were established, and the slope stability factor was obtained. One practical example indicates that the discussed method is more closely to the real condition.

Geological structure and dynamic mechanism of the Termit rift basin in West African rift system

Based on seismic and drilling data in the study area,the geological structure and kinematic process of the Termit rift basin were studied using seismic profile interpretation and balanced restoration to find out the dynamic mechanism of the basin.(1)The geological structure of the Termit Basin is represented as a narrow rift basin,with development of series of structural styles in extensional,extensional strike-slip and compressional stress setting.On plane,it is narrow in the north and wide in the south,and transitions from graben to half-graben from north to south;it features a graben controlled by the boundary faults in the north and a fault-overlapped half-graben in the south.(2)Before the Cretaceous,a series of hidden faults developed in the West African rift system,which laid the foundation for the development location and distribution direction of the Termit Basin;during the Cretaceous to Paleogene periods,the basin experienced two phases of rifting in Early Cretaceous and Paleogene,which controlled the initial structure and current structural shape of the basin respectively;during the Neogene to Quaternary,the basin was subjected to weak transformation.(3)In the Precambrian,the Pan-African movement gave rise to a narrow and long weak zone within the African plate,which provided the pre-existing structural conditions for the formation of the Termit Basin.In the Early Cretaceous,affected by the South Atlantic rifting,the Pan African weak zone was reactivated,resulting in the first stage of rifting and the basic structural framework of the Termit Basin.In the Paleogene,affected by the subduction and convergence of the Neo-Tethys Ocean,the African-Arabian plate extended in near E-W trending,and the Termit Basin experienced the second stage of rifting.The oblique extension in this period caused intense structural differentiation,and the current structural pattern of alternate uplifts and depressions took shape gradually.