Jurassic landslides are widely developed in the Three Gorges Reservoir area. The study of the strength and deformation failure characteristics of the soft rock interlayer under different water pressures is of great theoretical significance to the long-term stability evaluation of the reservoir bank slope. MTS triaxial compression tests were carried out on the argillaceous siltstone of Shaximiao Formation, a typical soft rock of Jurassic in the Three Gorges Reservoir area, to study the strength and deformation damage characteristics of the rock under different water pressures. Based on fracture mechanics and effective stress principle, the mechanism of crack initiation and crack propagation under hydro-mechanical coupling effect was analyzed. It was found that water pressure can reduce the peak compressive strength of rock. With the increase of water pressure, the length and dip angle of dominant cracks increase, and the number of secondary cracks also shows a trend of increasing. The primary crack initiation and secondary crack propagation were controlled by K_Ⅱ and K_Ⅰ stress intensity factors, respectively. The maximum initiation angle of the primary crack was 70.5°. The critical propagation length of the secondary crack increases with the increase of the primary crack length. When the dip angle of the primary crack is about 45°, the propagation length of the secondary crack reaches the maximum under the same conditions. The results show that the existence of water pressure is conducive to the crack propagation, and the geometric characteristics of primary cracks also have a great influence on the crack propagation law.This study provides some theoretical guidance for the long-term stability evaluation of the reservoir bank rock mass.

The identification and analysis of the deposit slope stability is the focus of geological disaster prevention and control. Taking dense-fine grained slopes and loose gravel slopes as examples, a series of flume tests under rainfall infiltration were carried out. The effects of density, material composition, slope angle and vegetation coverage on slope stability and rainfall threshold were systematically analyzed. The results show that under rainfall infiltration, the dense-fine grained slope with uniform material composition and high density was more stable, resulting in a higher rainfall threshold and a lower catastrophability. The slope with non-uniformmaterial composition and loose gravel was more likely to fail than the slope with dense fine particles. The influence of the stone content on the stability of the slope is greater than that of the slope gradient. The critical rainfall of landslides increases first and then decreases with an increasing vegetation coverage; that is, when rainfall infiltration causes the slope soil to be supersaturated, the higher vegetation coverage will trigger the whole deformation of slope and vegetation due to the strong development of vegetation roots, which increases the catastrophability of the slope.The research results can provide a theoretical basis for the instability mechanism and stability evaluation of deposit slopes.

Inverse grading deposits are commonly found in circulation and accumulation areas of high-speed and long-distance landslides. Due to its special structure of large particle size at the top and small at the bottom and strong permeability, the accumulation is highly susceptible to unstable failure. In this study, using a self-designed device, seepage erosion tests were conducted on seven sets of inverse grading soil samples with continuous and discontinuous particle gradation of particle size 0.075-20 mm to investigate the parameter changes and fine particle migration patterns and laws during seepage erosion of inverse grading sand mass. The results show that the fine particle content and nonuniformity coefficient have an important influence on the seepage erosion of the inverse grading soil samples. The higher the fine particle content, the greater the nonuniformity coefficient and the lower the initial seepage coefficient. After the occurrence of cross-layer tube surge particles, the bottom layer of particle loss is the most, and the particle size of 0.075-0.125 mm particle loss ratio is the largest.The seepage capacity of the inverse grading sand mass depends mainly on the content of fine particles at the bottom. The higher the content of fine particles is, the greater the critical hydraulic gradient will be.In continuous graded soil samples, the relationship between the hydraulic gradient is quadratically related to the percolation coefficient.Soil samples with discontinuous particle gradation are stabilized when the content of fine particles exceeds 45%.After tube gushing occurred in the reverse grain sequence accumulation body, the particles show a migration pattern of stripping-precipitation-stripping-precipitation alternately eroded particles in the middle and lower layers. The study has theoretical and practical significance for the formation mechanism and prevention of such disasters.

The Jiangba deformed body is located approximately 5 km downstream of Jiangba village, Niwu Township, Jiali County, Tibet, on the right bank of Yigong Zangbo. Multiple surface avalanche traces are visible in the remote sensing images, and there is a threat of landslides and river blockage due to the instability of the mountain. There is an urgent need to identify the stability of the slope, the overall deformation characteristics and possible disaster threats to achieve the purpose of early prevention and plan ahead. In this study, a comprehensive research and evaluation method of "multistage image remote sensing interpretation monitoring +InSAR deformation analysis + field investigation" was adopted to interpret and analyze the slope surface of the deformed body in detail, and it is shown that the deformed body is currently in a state of "overall stability and local collapse". In recent years, the boundary of the deformed body has not changed significantly, and many small-scale landslides have occurred in the southern and eastern slope foothills. Under the influence of external environmental changes, the possibility of high collapse-debris flow still exists in the middle and upper parts of the deformed body.

The newly filled soil in reclamation areas shows a significant consolidation effect, resulting in severe ground settlements and inducing extremely adverse impacts on the stability of foundations on site. Based on the continuous boundary conditions, this paper establishes a one-dimensional filled soil-native seabed consolidation theory with consideration of the self-weight of the filled soil and the bedding characteristics of the seabed simultaneously, and derives an analytical solutions to the response of the excess pore water pressure and the consolidation degree through the eigenfunction method. The proposed solution is subsequently verified through the degradation of the boundary conditions and mathematical models. By virtue of the proposed solution, a parametric study is conducted to investigate the influence of the spatio-temporal impact factors (including the self-weight of the filled soil, moduli of the filled soil, time factor, and additional load at ground) on the consolidation. The main conclusions can be drawn as follows: ①The self-weight of the filled soil drives the consolidation of the newly filled ground and should not be ignored in practical engineering. ②The effect of the permeability coefficient on the dissipation of the excess pore water pressure is relatively complicated. In case of change in the penetrability of a certain soil layer, it will have opposite influences on the excess pore water pressure of the overlying and underlying soil layers. ③The volume compressibility of the soil has a significant influence on the excess water pressure. And the influence of the volume compressibility of the deeply buried soil is more significant. ④The additional load caused by, for instance, the stacking at the ground, will slow down the consolidation of the site.

To accurately evaluate the blasting effect of tunnel demolition, guarantee the normal traffic of vehicles during the blasting for insitu two-to-four lane expansion in the municipal tunnels, and reduce the risk of blasting demolition as well as expansion of existing tunnel linings, a comprehensive evaluation model of the tunnel blasting effect based on EAHP was established with the matter-element theory. First, 29 evaluation factors were selected from 5 aspects: blasting scheme design, surroundings of blasting area, blasting quality, blasting materials, blasting safety technology, and 5 evaluation grades were demarcated. Second, the primary correlation function established with extension transformation was adopted to calculate the correlation degree of influencing factors of blasting effects to the evaluation grade, an analytic hierarchy process (AHP) method was introduced to determine the index weight, and the blasting effect grade was determined according to the principle of maximum correlation degree. Therefore, an integrated evaluation method based on Extenics-AHP, namely, EAHP, was established. The results showed that this method was applied to the blasting effect evaluation of the insitu two-to-four lane expansion project in Loushan Tunnel in Zhejiang Province, and the blasting effect evaluation result was K_max=K₂=-0.030 9, namely, the blasting effect evaluation level of the insitu two-to-four lane expansion in the tunnel was "good blasting effect", which was consistent with the actual condition of the project. Therefore, the evaluation indexes and weight coefficients selected based on EAHP model were reasonable and reliable, and the maximum correlation degree obtained by extension transformation could also better reflect the grade of the tunnel blasting effect, indicating this evaluation method had better adaptability to tunnel blasting effect evaluation.

To ensure the safety of life and property of residents on landslides and reveal the deformation and failure law of masonry buildings on landslides, it is necessary to carry out a simulation study on the deformation and failure process of masonry buildings under the action of landslide deformation. A refined model of a masonry building was established based on the contact separation modeling method in ABAQUS, and the viscous contact interface was used to simulate the effect of mortar in the wall. Comparing the results of the numerical simulation with the physical model test results, the main conclusion is as follows: through the comparison of macroscopic deformation characteristics and microscopic stress and strain data obtained from physical and numerical model tests, the load-strain curve of the numerical model test agrees well with that of the physical model test, and their strain clouds are consistent, proving the validity of the numerical simulation method. The law of crack propagation and strain distribution of building walls in landslide tension areas is revealed, which can provide a basis for the protection design of masonry buildings in landslide tension areas.

To explore the accuracy of the calculation method of the jacking force of circular curved pipe jacking under different pipe-soil contact characteristics, in combination with the curved steel pipe jacking project of Gongbei Tunnel of Hong Kong-Zhuhai-Macao Bridge, this paper adopted several commonly used jacking force calculation formulas for the curved pipe jacking at home and abroad and jacking force finite element analysis model with consideration of grouting effect and the pipe-soil contact range established with ABAQUS to calculate the jacking force. It was found by contrast with the pipe jacking force data: ①The calculated value of jacking force: JMTA formula≫Shanghai normative formula>Shimada formula, where it was considered that the calculated value of the lower limit of Shimada formula of 1/3 pipe-soil contact was relatively close to the measured value. ②Through numerical simulation, it was found that the simulated jacking force of 1/3 pipe-soil contact characteristics was gradually close to the one of 1/2 pipe-soil contact characteristics; in the grouting state, the previously measured jacking force was close to the one of 1/2 pipe-soil contact characteristics. When the jacking force tended to be stable, the measured jacking force was close to the one of 1/3 pipe-soil contact characteristics. Therefore, the numerical model could predict the jacking force of the pipe jacking under the same working condition and had a certain guiding significance for actual construction.

To follow the national development concept of "Lucid waters and lush mountains are invaluable assets", the reuse of abandoned mines has become a hotspot. A reasonable stability analysis method to reinforce the slope must be proposed. However, the shape of common mine slope is close to a circle or an ellipse, and thus the three-dimensional space effect of stability cannot be ignored. Based on the strength reduction method of FLAC3D, an axisymmetric numerical analysis method was proposed. Through comparative calculation and analysis, some conclusions can be obtained as follows: (1)For concave slopes with circular-likeshape, the safety factor calculated by the axisymmetric model is more accurate than that of the traditional plane strain model, the calculation time of the proposed model is less, and the proposed model is also applicable to various types of slopes. (2)The safety factor obtained from the axisymmetric model is close to the results obtained from the 3-D model, while the safety factor obtained from the traditional plane strain model is conservative.(3)The calculation results of the axisymmetric model are also consistent with the results from the literature. The proposed model is further applied to the stability analysis of a mine slope reinforcement in Changsha Ice World, which can also be applied in the slope stability evaluation of similar projects.

Susceptibility evaluation is the basis of regional landslide risk early warning and stability analysis. Scientific and reasonable division of evaluation unit is the key to landslide susceptibility evaluation. For large-scale fine landslide susceptibility evaluation, the traditional slope unit division method based on hydrology and geomorphology generally results in low accuracy of the evaluation. In this paper, an improved slope unit method based on the slope geological environment is proposed. Dazhou Town was selected as an example and the obtained results from the proposed model were compared with the results from hydrological analysis method and curvature watershed method. The results show that the size uniformity of the evaluation units divided by the proposed method is better, and no fine units or deformed long strip units were generated. The overall morphological characteristics of the evaluation unit are more reasonable, and the morphological index is between 1 and 2, which generally presents circular-like or square-like shape. At the same time, the superposition degree between the results of the improved slope unit division and the range of the existing disaster boundary is the highest, which can better reflect the physical significance of landslide risk assessment. The proposed model has significant potential for improving the accuracy of regional landslide susceptibility evaluation.

Wettability is one of the important physical properties of reservoir rock surfaces, and it is a key factor affecting capillary force, relative permeability, bound water saturation and fluid micro-distribution. Based on the molecular simulation method, this paper made a study of the wetting behavior of a graphite surface (organic surface) modified by the oxygen-containing functional groups and the distribution characteristics of the methane-water system in organic slit pores. The results showed that the interaction energy between the water molecules and the surface decreased and the wetting contact angle of the organic matter surface increased with the increase in the oxygen-containing functional groups; with the increase in the temperature, the interaction energy between the organic matter surface and the water molecules increased, and the wetting contact angle decreased; in the graphite slit pore model with symmetrical C/O ratio, water molecules were symmetrically distributed near the wall of oxygen-containing functionalized graphite, and with the decreasing in the C/O ratio, the relative concentration of water molecules increased and the diffusion coefficient decreased, while methane molecules were clustered in the center of the pore. In the graphite slit pore model with asymmetric C/O ratio, the water molecules were asymmetrically distributed near the wall of the oxygenated functionalized graphite, while the methane molecules were clustered in the center of the pore, where the side with a low C/O ratio had strong hydrophilicity on the wall and a high relative concentration of water molecules, while the side with a high C/O ratio had strong hydrophobicity on the wall and a low relative concentration of water molecules. The research findings were extremely significant to make a study of the influences of shale reservoir characteristics.

The tight sandstone reservoir of Jurassic Lianggaoshan Formation in Fuxing area, Sichuan Basin has shown good exploration potential recently. Represented by wells X and Z, the tested industrial oil and gas flows have been obtained. In order to further understand the development characteristics and control factors of tight sandstone reservoirs of Jurassic Lianggaoshan Formation in the Fuxing area, through core observation, ordinary thin section identification, scanning electron microscope observation and multiple test results, the target layer in the study area is analyzed in detail. The results reveal that the tight sandstone reservoir of Lianggaoshan Formation is generally characterized by low porosity and low permeability, and the reservoir space is dominated by inorganic pores with a pore radius of 10-50 μm. Throat width is 2-10 μm。According to the influence of different diagenesis on reservoir physical properties, compaction and partial cementation are classified as destructive diagenesis, while dissolution, tectonism and cementation with chlorite cementation are divided into constructive diagenesis. This study makes clear that the subaqueous distributary channels of the delta front is the most favorable to the development of Lianggaoshan Formation sandstone reservoir. The cementation with dissolution, tectonism and chlorite cementation can improve the physical properties of Lianggaoshan Formation tight sandstone reservoir.

The Chang 7 Member of the Ordos Basin has favorable shale oil resource potentiality. The exploration and development of sandstone interlayer shale oil in the Chang 7 Member has made substantial breakthroughs. The exploration and development potential of shale oil is huge, and will be a significant oil and gas alternative resource in the Changqing Oilfield in the future, but its related geological fundamental research is relatively weak. Based on the observation, description and systematic sampling of the centimeter-level core of the full core section of Chang 7 Member in Well Ning228, a series of experimental test analyses and identification outcomes indicated that Chang 7 Member primarily developed four rock types: Black shale, dark mudstone, siltstone and tuff. The overall conditions of source rocks in the Chang 7 member are superior, the organic carbon content of shale is high, and the hydrocarbon generation potential is large. The organic matter types are mainly type Ⅰ and type Ⅱ, which are in the low mature-mature stage, and the black shale has higher organic matter abundance. The main reservoir spaces of the Chang 7 Member are primary pores and secondary pores. Mud shale primarily develops organic pores and inorganic pores. Fine sandstone mainly develops residual intergranular pores, intragranular pores and intergranular pores. Tuff mainly develops intergranular pores and mineral intragranular pores. The overall oil-bearing property of the Chang 7 Member is good, but the mobility difference is large. The fluid mobility in sandstone and tuff is good, and the mobility inshale is poor. In short, fine anatomical analysis of typical interlayer shale oil provides favorable guidance for promoting the large-scale development of shale oil in the Ordos Basin.

The turbidite reservoir in the third Member of the Shahejie Formation is an important field for oil and gas accumulation in the Dongying Sag. The obvious carbonate-rich characteristics of the water during the sedimentation period seriously affect the accuracy of geophysical prediction and the quality of the reservoir. Therefore, it is particularly important to carry out studies on salinity reconstruction of the paleo-aqueous medium in the study area. The authors integrated multiple test data of trace elements, clay minerals, carbon and oxygen isotopes, etc. to explore the quantitative links between different reconstruction methods and establish a set of comprehensive characterization methods to quantitatively reconstruct the vertical and horizontal differences of paleosalinity in the study area. On this basis, the authors further explore the mechanisms controlling the distribution pattern of paleosalinity. The study showed that the high salinity areas were mainly distributed in the Tuo-Sheng fault zone, the north slope of the Caoqiao area, the central anticline zone and the slope zone, while the low salinity areas were mainly distributed in the recharge area of freshwater and the deep depressions. The paleoclimate cycle controls the longitudinal water salinity cycle and the nature and supply of the source input control the difference in the plane water body near the source channel. The local high-salinity water body were caused by the upwelling of deep brine from the fourth Member of the Shahejie Formation. The results indicate that the next direction of turbidite exploration should target the freshwater-affected areas around the paleo-delta and the freshwater dilution areas around the sag center.

The division accuracy of a single-genesis sand body in a river channel determines the evaluation resolution of residual oil content and limits the efficiency of oil production. The following methods were used to describe the underwater distributary channel of the M oilfield in the Nanpu Depression. First, the seismic attribute was optimized to identify the boundary of a single channel-lobe complex. Then, the channel main stream line was traced with the constraint of the geological knowledge base of the braided river delta front, and the channel boundary was delineated using acoustic inversion technology. Finally, the results of channel characterization were verified with dynamic data. The research shows that the M Oilfield has multiple channel-lobe complexes developed in the same period. Even a single channel-lobe complex contains 2-8 channels. The width of the underwater distributary channel ranges from 80-240 m, with a maximum width of 440 m. The thickness of asingle channel sand body is 2.6-5.8 m, and the width-thickness ratio of the channel ranges from 25∶1 to 78∶1. The dynamic verification data and drilling results show that the prediction accuracy of channel distribution is 90%. The high prediction accuracy of the channel sand body distribution can promote the evaluation resolution of residual oil content, and provide constructive guidance for later development and management. The method has a certain reference value in the underwater distributary channel characterization of the braided river delta front reservoir in the complicated fault block.

Huge and thick black shale was deposited in the Mianyang-Changning intracratonic sag of the Sichuan Basin, which is a favorable target for shale gas exploration in the future. Taking the paleofluid preserved in the Qiongzhusi Formation shale as the research object, based on the petrological and optical characteristics of fracture veins observed in cores and thin sections, the source and origin of the paleofluid were analyzed by carbon and oxygen isotope testing, the formation pressure evolution of shale gas was simulated by using BasinMod software, and the preservation conditions of Qiongzhusi Formation shale gas in the central portion and surrounding areas of the Mianyang-Changning intracratonic sag were discussed. The results show that fracture vein rarely appears in the Qiongzhusi Formation shale of wells GS17 and MX9. While multiple groups of bed-parallel and high-angle fractures appear in Well W201, which are filled with mesocrystalline to coarse crystalline calcite, fibrous calcite, saddle dolomite, barite, and quartz. Carbon and oxygen isotopes indicate that fracture veins were generated by fluids of hydrothermal solution or organic matter decarboxylation. Hydrocarbon generation, particularly the crude oil cracking, induced the strong overpressure in the Qiongzhusi Formation of the intracratonic sag and the Gaoshiti-Moxi area, and the overpressure has been preserved thus far. Although overpressure was also developed in the Weiyuan structure, it dissipated in the late tectonic movement. Compared with the intracratonic sag and Gaoshiti-Moxi area, the late preservation conditions of shale gas in the Weiyuan area were relatively harsh, but some local overpressure areas need to be focused on.

More and more attention has been paid to the sedimentary forward modeling (SFM) since the study on the sedimentology is targeted toward quantification, process orientation and systematization. This review first stated the main input and output data of the current sedimentary forward modeling and sorted out the determination methods of the input parameters. Then it reviewed the classification methods of the sedimentary forward modeling, and the classification principles included principle of simulation, number of simulation processes, types of simulation results, simulation dimension, simulation scale, data fidelity and source region covering source-sink system. Subsequently, it introduced the sedimentary forward modeling methods for the different sedimentary systems of clastic series, including hillside landform, river and deep-draft waterway, delta, lobe and landslide. It also described some classic simulation programs for the individual series, indicated the sedimentary characteristics of this series to be essentially simulated and their corresponding principles of simulation and covered multiple simulation methods as much as possible to expand the understanding of the sedimentary forward modeling. Finally, it looked into the development of the sedimentary forward modeling believed it would be targeted toward the three-dimension visualization, multi-process integration and multi-discipline integration, proposed to strengthen the training of compound talents in computer, mathematics, mechanics and geosciences; strengthened the experimental study on the sedimentary forward modeling hypothesis to study the sedimentation theory; tried multiple simulation methods and shifted the application foremost to the research and development foremost.

To understand the controlling mechanism of pore-throat characteristics on gas-water relative permeability characteristics of tight sandstone gas reservoirs and better guide the increase in gas reserves and production, taking the Lower Shihezi Formation reservoir in the J72 well block of the Dongsheng Gas Field as a research object, the effects of microscopic pore-throat parameters on gas and water transport properties were studied by combining various analytical data and lithofacies division. The controlling effect of rock lithofacies on gas content and productivity was revealed.Results show that the lithofacies of the Lower Shihezi Formation in the J72 well block can be classified into conglomerate rock, gravelly sandstone, pebbly coarse-grained sandstone, medium- and fine-grained sandstone, and mudstone lithofacies, of which the pebbly coarse-grained sandstone and gravelly sandstone lithofacies are the high-quality lithofacies. Pore types are mainly secondary intergranular dissolved pores, with an average proportion of 48.5%. The proportion of intergranular dissolved pores in pebbly coarse-grained sandstone lithofacies, gravelly sandstone, and medium- and fine-grained sandstone lithofacies decreases successively.Pore space in the three lithofacies is multifractal, and the proportion of large pores gradually decreases. The high-quality lithofacies has superior physical properties and small comprehensive fractal dimensions. The high-quality lithofacies also has low clay mineral content, large average pore-throat radius, large movable gas porosity, maximum effective gas permeability during gas transport, and high gas-bearing capacity. A comprehensive study shows that high-quality lithofacies is the key factor in controlling the high and stable production of gas wells. The in-depth analysis of the microscopic characteristics of lithofacies provides useful guidance for the efficient development of tight sandstone gas reservoirs.

Natural gas hydrate is a kind of clean energy with great development potential but is still not commercially developed due to the bottlenecks such as exploitation technology, economical efficiency, and environmental effects.In recent years, people have explored the application of hydrate technology in the field of CO₂ capture, seawater desalination, energy storage, gas separation, etc. One of the most challenging and critical problems is how the hydrates are formed and decomposed at any time. This paper summarizes the fundamental research on hydrate decomposition dynamics, including hydrate decomposition properties, influencing factors, and dissociation mechanisms. Moreover, the paper reviews the development of hydrate dissociation dynamics models. The existing models are divided into four categories according to dissociation mechanisms: Thermal dissociation models, intrinsic dynamics models, mass transfer dissociation models and integrated models, and their assumptions, main understanding and limitations are highlighted. Future directions for improving hydrate dissociation dynamics research are foreseen to deepen the understanding of hydrate dissociation dynamics and promote the development and utilization of hydrates.

The Middle Jurassic sandstone reservoirs of the Turpan-Hami Basin are the main targets for unconventional tight oil and gas exploration and development.To better understanding the main controlling factors of pore characteristics in the Middle Jurassic tight sandstones of the Shengbei Sag, Turpan-Hami Basin, a comprehensive investigation referring to lithology, diagenesis, physical properties, and pore structure was conducted on samples obtained from 8 wells. The results indicate that the Middle Jurassic tight sandstone reservoir characterized by low porosity and ultralow permeability primarily contains feldspar lithic sandstones, followed by lithic sandstones.These sandstone reservoirs suffered strong compaction and complicated mineral cementation, replacement, and dissolution. These sandstone reservoirs are dominated by the secondary pores generated by feldspar dissolution, with some residual interparticle pores, quartz dissolution pores, clay mineral interlayer pores, and microfractures.Pore throat of 5-50 nm most widely appears in these reservoirs, while the porosity and permeability of these reservoirs mainly depend on the pore throats of 50 nm-1 μm and 100-800 μm, as indicated by the good positive correlations between pore throats and volumes. Both porosity and permeability correlate positively with the quartz and feldspar contents but negatively with the clay and carbonate contents. These correlations were supposed to be caused by two factors: ①strong compaction led to the loss of most interparticle pores but kept the residual interparticle pores associated with rigid quartz, and caused the occurrence of microfractures and dissolution pores within the quartz; the migration of hydrocarbon fluids containing organic acids into the Middle Jurassic reservoirs resulted in the significant dissolution of feldspar and generation of secondary dissolution pores. This process promoted theoccurrence of pore throats of 50 nm-1 μm and 100-800 μm and improved the porosity and permeability. ②The primary interparticle pores and secondary microfractures were filled with authigenic clay or carbonate cement; the replacement of feldspar by calcite disturbed the positive effects of feldspar dissolution on the porosity and permeability, which reduced the occurrence of 50 nm-1 μm and 100-800 μm pore throats and the physical properties of these reservoirs.Therefore, the occurrence of pores was closely related to the early sedimentary environments and the later diagenesis after deposition.More importantly, mechanical compaction, feldspar dissolution, and authigenic mineral cementation played crucial roles in regulating the occurrence of pores and the physical properties of these sandstone reservoirs in the study area.This study should be helpful in predicting the favorable exploration areas of tight oil and gas in the Middle Jurassic sandstone reservoirs in the Shengbei Sag, Turpan-Hami Basin.

It is generally believed that the provenance of the Neogene sandbar reservoir in the Zhahaquan Oilfield in the western Qaidam Basin is consistent with that of the Paleogene. However, existing studies present different opinions on the provenance during the Paleogene, which makes the provenance of the Neogene unclear and affects the study of sedimentary facies and reservoir configuration in the Zhahaquan area. By using SPSS software, clustering analysis was conducted on the limited heavy mineral data from Neogene in this area.Then, the distribution characteristics of heavy minerals from different samples were studied and compared with the Tiemulik provenance and Qimantag-Dongchaishan provenance.It is considered that the Neogene provenance in the Zhahaquan area originated from Qimantag-Dongchaishan, and there is no evidence of intersection and mixing of the two major provenances. The Qimantag-Dongchaishan provenance can be further divided into two secondary provenances, i.e.one covering only the Zha2 well area, Zha401 well area and Zha7 well area, and the other covering the whole area. There is intersection and mixing of the two secondary provenances. This study clarifies the provenance of Neogene deposits in the Zhahaquan area and provides a significant reference for research on sandbar configuration, especially the migration and superposition of sandbars in this area.

The Qianchuiliu Gold Deposit on the northeastern margin of the Jiaolai Basin is a newly discoverd altered rock type gold deposit, and is a medium-sized gold deposit hosted in the structural alteration zone between Muniushan, Jingshan Group and Queshan monzonitic granites. However, the source of ore-forming materials and the ore genesis are not clear. Based on previous field and analytical studies, the authors conducted sulfur and lead isotopic analyses on gold-bearing pyrite from typical ores as the research target. The δ³⁴S values are high and homogeneous ranging from 10.13‰-12.39‰, with an average of 10.98‰ and polar odds of 2.26‰. These sulfur isotopic results reveal a mixing process of sulfur in the Jingshan Group during the upwelling of deep ore-forming fluid. The ratios of ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb vary from 17.149-18.886, 15.482-15.677, and 37.860-40.073, respectively, suggesting a crust-mantle mixed source. In conclusion, sulfur and lead isotope analysis results of the Qianchuiliu Gold Deposit show a crust-mantle mixed source and are similar to those of typical gold deposits in this region. The gold deposits on the northeastern margin of the Jiaolai Basin formed at the large-scale Yanshanian metallogenic event, indicating great prospecting potential in this area.

Since 2019, major breakthroughs have been made in the prospecting of the Lower Cretaceous sandstone-type uranium deposits in the northern Ordos Basin. The Lower Cretaceous sandstone layer is expected to become another important sandstone-type uranium prospecting target after the Middle Jurassic. Establishing the metallogenic model of the Lower Cretaceous provides a better guide for prospecting work. Based on previous regional geological, drilling cores, and analytical data, the authors systematically summarized the basic geological characteristics of uranium mineralization in the Lower Cretaceous in this area and preliminarily established the uranium metallogenic model of the Lower Cretaceous.The results suggest the six Lower Cretaceous rock types can be divided into three geochemical types. Uranium mineralization mainly occurs in the brown-gray sandstone, which is the transition zone from brown-red sandstone to green sandstone. The green sandstone is formed by oxidation first and then reduction.The metallogenic type is dominated by interlayer oxidation, supplemented by phreatic oxidation in the Late Cretaceous. The Lower Cretaceous "secondary oxidation" uranium metallogenic model can be divided into three stages: first oxidation mineralization stage, large-scale reduction mineralization stage, and second oxidation mineralization stage.These research results can provide a new idea for uranium exploration in new strata of Ordos Basin.

Based on geological surveys and experimental data, numerical modeling of metallogenic dynamics (NMMD) establishes a mathematical model (mathematical-physical equation) that quantitatively characterizes metallogenic processes using the basic laws of mathematics, physics and chemistry. Then, using the finite element or finite difference method, the model is built through efficient computer calculation, simulating the metallogenic dynamic process and its metallogenic response, revealing metallogenic law and guiding prospecting. NMMD integrates theories and methods of geology, mathematics, physics, chemistry, computers and other disciplines and has distinct characteristics of interdisciplinary integration. In recent years, driven by the rapid development of computational science and mathematical geology, important progress has been made in NMMD. This paper summarizes the basic theories and methods of NMMD, compares the characteristics of four metallogenic numerical simulation software programs, and introduces the development and application status of NMMD with progress of the author′s team in the past decade. The main conclusions and understandings are as follows: ①Multi-field coupled metallogenic dynamics numerical simulation is the only feasible method to reproduce the large-scale complex metallogenic process. With the rapid development and improvement of high-performance computing technology and nonlinear dynamics theory, it becomes one of the research hotspots and development directions of modern mathematical geoscience. It is important to reveal the metallogenic mechanism and obtain mineral exploration information, which has great potential for development; ②At present, there are some limitations in NMMD, such as uncertain simulation parameters and incomplete coupling of multifield processes, which will be the focus of its future development. Numerous studies have been devoted to solving these problems; ③Under a new paradigm of scientific research driven by big data, a combination of NMMD and machine learning can effectively invert the metallogenic process and quantitatively predict mineral resources. This method is an important breakthrough in the application of NMMD in deposit genesis and mineral exploration. This paper clarifies the basic methods and key problems of NMMD in promoting the study of deposit genesis and exploration, and expounds the frontier direction of NMMD, which provides basic guidance for the study of computational modeling of metallogenic dynamics.

As an effective risk prevention and control tool for contaminated sites, Monitoring Natural Attenuation (MNA) has been applied worldwide. The core of this technology is to determine the ability and efficiency of pollutant attenuation, which are influenced by the nature of the pollutants themselves, as well as the typical geochemical and hydrogeological conditions and other inherent characteristics of the site. It is of greater practical importance to clarify the influence of the inherent properties of the site on the natural attenuation of pollutants for the rational application of the technology. The authors address the influence of typical site geochemical characteristics and hydrogeological characteristics on the natural attenuation process of pollutants in groundwater and its mechanism. The typical geochemical characteristics, such as the organic matter and mineral composition of sediments, control the adsorption and complexation behavior of pollutants, and participate in the electron transfer process to influence the biodegradation and chemical transformation of pollutants. Hydrogeological characteristics influence the ability of natural attenuation through the differences in permeability, adsorption and desorption capacity caused by the lithologic characteristics of sediments. Groundwater flow rate controls the convection and dispersion of pollutants and affects the dissolution and release of pollutants from sediment to groundwater as well as the kinetic process of biodegradation. In general, due to the complexity of organic matter, mineral and microbial components and the heterogeneity of hydrogeological conditions, the study of the influence of site intrinsic properties on the natural attenuation of pollutants needs to be further strengthened. In particular, we need to identify the spatial and temporal dynamics of pollutant attenuation through long-term site monitoring, and deepen the understanding of the mechanisms underlying the interaction between typical site geochemistry, hydrogeological conditions and pollutants.

Groundwater pollution risk assessment is an effective tool for preventing and controlling groundwater pollution. The study on groundwater pollution risk assessment can serve as a basis for the management of groundwater contaminated sites. The present risk assessments often ignore the spatial variability of pollution within the site and the susceptibility of receptor. This paper proposes a new site groundwater pollution risk index system that can be used for pollution sites with a variety of features. The index system considers the spatial distribution of pollutant at the site and nearby receptors. Based on the four aspects of pollution load, vadose zone vulnerability, aquifer vulnerability, and receptor susceptibility, this paper conducted index screening and weight calculation using the analytical hierarchy process. A site groundwater pollution risk assessment index system was constructed, and the risk was divided into four levels: low, medium, higher, and high. Using the constructed risk index system, the spatial risk distribution of a hexavalent chromium site in Henan Province was studied. The results show that the site was at a medium risk level, with the highest risk at the chrome slag heaps and the southeastern of the buried chrome slag. The potential loss of surrounding receptors and the pollution load are the main causes of groundwater contamination risk at the site. Single parameter sensitivity analysis shows that the effective weights of each index are in line with the theoretical weights, indicating the rationality of the constructed site groundwater pollution risk assessment system, which can be applied to other sites with characteristic pollutants.

In arid and semiarid regions, lake-basin ecosystems are an important part of watershed security barriers, playing an important role in maintaining the stability of ecological patterns. However, the ecological environment of the lake-basin system has been gradually degraded in recent years, and its change process is accompanied by a complex dynamic mechanism. In the present study, we explored the spatial variability of the ecological environment of the lake-basin system and its drivers by taking Baozhainao Lake in the Mu Us Sandy Land of the Ordos Basin as the study area.In-situ dynamic monitoring, sample survey, statistical analysis and numerical simulation were employed. The distribution patterns of typical vegetation in the basin were determined and the mechanisms underlying the mutual feedbacks between subsurface hydrological process and lakeshore ecosystem was explored. The results show that the Baozhainao lake-basin ecosystem consists of four zoning types, namely, the lake zone, the lake nearshore fluctuation zone, the lakeshore beach zone, and the lakeshore wind beach zone. From the lake to the beach zone, the depth of water table increased gradually and the vegetation type transitions from water-loving and salt-tolerant to drought-tolerant. It was further found that the presence of vegetation on the lake shore significantly affects the circulation mode of the groundwater flow system. The conversion between lake and groundwater occurs mainly in the local groundwater flow system, resulting in a significant reduction in groundwater recharge to the lake.The results of this study can provide a scientific basis for the restoration and conservation of plant species diversity and vegetated ecosystems in the lake nearshore fluctuation zoneand lakeshore wind beach zone in arid regions.

To study the formation mechanism and hydration characteristics of geothermal resources and provide a reference for the comprehensive utilization and development of resources. Collect the water samples from Midi River in Bijie City, Guizhou Province, analyze the hydrochemical characteristics, and adopt the Piper trilinear diagram, geothermal and landmark method and audio magnetotelluric method to study the geothermal hydration and formation mechanism of Midi River. The research indicates: affected by Pingzhai dome structure, the internal joint structure in the dome is very developed in this region, which is conducive to the migration of deep thermal water to the relatively low area in the dome, forming the convective underground thermal water resources of the fold dome structure.Through regional fault detection, it is inferred that there are five shattered fault zones (or fissures) in this region, among which F₄ and F₁₃ faults have steep occurrence and shallow downward extension; F₉ is more pronounced and tends to be northwest; F₁ has a nearly northsouth trend, tends to northwest, and extends deeper; F₁₇ and F₁₈ are more obvious, but the extension is shallow. It is inferred that the F₁ fault has good thermal control lability and is a favorable position for underground thermal water upwelling. Heating of the surrounding rock is obtained within 2 500 m depth of runoff after receiving infiltration recharge water from atmospheric precipitation in the rim of Pingzhai dome, and a deep pressure-bearing thermal reservoir is formed in the dolomite of Dengying Formation of Sinian System under the action of overlying Cambrian clastic rock water-resisting and heat-preservation overburden. The analysis of hydrochemical characteristics shows that geothermal water is low-salinity water. Na⁺ is the main positive ion in geothermal well water, accounting for approximately 45%, followed by Ca²⁺ and Mg²⁺, accounting for approximately 49%. HCO₃^- accounts for the main negative ion, SO₄^2- accounts for 39%, and Cl^- accounts for almost no, so the chemical type of geothermal water is HCO₃^-·SO₄^2--Na·Ca; the geothermal reservoir temperature of the geothermal well is 53.98℃, the geothermal gradient is 2.85℃/100 m, and the circulation depth of the geothermal water is approximately 2 500 m.The research results have a good guiding significance for the exploitation and utilization of geothermal resources in Bijie City, Guizhou Province.

Compared with coring data, well logging data contain much lithologic information with the advantages of strong continuity and low cost. The machine learning method is applied to explore the correlation between the log curves and the lithology of the actual coring samples, realize the automatic identification of the lithology of the reservoirs, reduce the lithologic identification cost, improve the identification efficiency and accuracy and provides an effective tool for the evaluation of the reservoirs. Based on the lithology classification standard, the sample classification scheme is approximately selected and a machine learning lithologic identification method combined with the vertical reservoir information is proposed to design an experimental scheme. The depth window is used to carry out the sequence sampling of the conventional logging data and the known lithologic data to generate training samples. Logistic regression, support vector machine, random forest, convolutional neural networks and stacking ensemble learning are used to build machine learning models to identify the lithology of original samples of strongly heterogeneous rock formations in an oilfield in Xinjiang. The results show that when the width of the depth window matches the thickness of the rock layer well, the accuracy of lithologic identification obtained by each machine learning method is greatly improved after preprocessing the original strong non-equilibrium sample with the method in this paper. The width of the depth window determines the identification accuracy of the rock layer thickness. A thinner depth window can identify a thinner rock layer, while a thicker depth window contains more vertical information, which can obtain higher identification accuracy at the corresponding rock thickness. The machine learning lithologic identification method combined with vertical reservoir information is proposed, which provides an economical and effective reference solution for the automatic and effective identification of heterogeneous thin rock layers.

As a newly developed embankment type, back-to-back mechanically stabilized earth(MSE) walls have been increasingly used for the construction of roads and embankments in recent years due to their great earthquake-resistant performance, and a large number of these walls are built in tiered configurations to meet the needs of construction. However, the available literature on the seismic response of tiered back-to-back MSE walls is very limited, and existing design guidelines do not provide a clear earthquake-resistant design approach for these walls. Based on previous analysis, a finite-element procedure was used to simulate the seismic response of two-tiered back-to-back MSE walls under earthquake loading. In this study, the backfill soil was simulated using the hardening soil model with small-strain stiffness (HSS model), and the block-block, and soil-block interactions under earthquake loading were considered. To gain insight into the seismic behavior of reinforced soil structures, 18 ground motion records at class I sites around the world were scaled to a peak acceleration of 0.4g and employed as the excitation motions, which had very different frequency characteristics and earthquake intensities. The results showed that an appropriate tier offset decreased the residual deformations and effectively increased the seismic stability of the walls; the deformation mode for two-tiered back-to-back MSE walls subject to seismic loading was mainly influenced by the frequency characteristics of the input ground motion as well as the fundamental frequency of these walls, and the change in the distribution of structure mass and stiffness due to the change in tier offset modified the structural vibration mode to a certain extent. It was also found that there existed good correlations between the maximum reinforcement load and the Arias intensity(I_A^input), the duration T_d, the tier off-set C, the predominant frequency f_i of the input ground motion, and the natural resonant frequency check spelling of the wall, which identified the influence of these factors on the earthquake-resistant performance of back-to-back MSE walls from one side. The research results can provide reference for practical engineering design.

Shale oil reservoirs, characterized by no productivity, are developed by horizontal drilling and volume fracturing, and it is very important to optimize shale fracable intervals based on engineering quality logging evaluation. The Paleogene Funing Formation shale in the Subei Basin is taken as a typical example in this study. A sonic scanner is used to calculate the elastic parameters, including Poisson's ratio and Young's modulus. Dynamic and static parameters are converted through core analysis data. The brittleness index and in situ stress are calculated according to Poisson's ratio and Young's modulus. In addition, a one-dimensional rock mechanics model was constructed with the shear slowness in a single well to calculate three components of in situ stress. Finally, considering the difference in the brittleness index and horizontal stress differences between different layers, brittleness index (BI) and (BI/(σ_H-σ_h)) were selected to describe the engineering quality. According to oil test data, the larger the brittleness index and the smaller the horizontal stress are, the higher the capacity after fracturing. A cross plot of the brittleness index and BI/(σ_H-σ_h) is established to divide the reservoir types. Consequently, there are two types, including I high productivity(engineering quality characterization parameters >2.2) and Ⅱ medium-low productivity (engineering quality characterization parameters < 2.2), in the Paleogene Funing Formation in the Subei Basin. High productivity produces oil after fracturing, which suggests that the classification results of sweet spots depending on the engineering quality characterization parameters are better. Logging evaluation of the engineering quality of shale oil reservoirs can provide a theoretical basis and technical guidance for optimizing favorable fracability and high productivity layers and provide scientific guidance for drilling and fracturing layer optimization of shale reservoirs.

High-voltage electropulse boring (EPB) is a new drilling method with great potential for drilling and industrialization. The existing high-voltage electropulse boring damage model based on PFC2D does not calibrate the parameters of the rock used in the rock-breaking test, so it is impossible to ensure that the simulated model is consistent with the mechanical properties of the rock in the actual rock-breaking test. The parameters of natural rock were calibrated based on the data results of indoor uniaxial compression and Brazilian splitting tests. Based on the calibrated micro parameters, a geometric model consistent with the size of the high-voltage EPB test was established, and the EPB process was simulated. The simulation results indicated that the shear failure mainly occurred in the process of high-voltage EPB, accompanied by a certain amount of tensile failure. Then, the EPB test was carried out with the high-voltage EPB test system, and an irregular broken hole with a diameter of 60 mm and a depth of 22.5 mm was obtained. The breaking effect was visualized by point cloud software. The results of the EPB rock-breaking test verified the effectiveness of the calibrated parameters. Finally, the influence of the fractures on the rock-breaking effect of high-voltage EPB was studied through the geometric model established with the calibrated parameters. The results showed that the existence of fractures would reduce the energy consumption in the rock-breaking process, and the crushing area tended to develop in the direction of fractures.

Inverting Rayleigh wave dispersion curves to obtain S-wave velocity profiles is one of the most important steps in near-surface Rayleigh wave exploration. Rayleigh wave inversion is a multi-extremum, nonlinear problem, and this paper introduces the antlion optimizer to solve this type of problem. The antlion optimizer is a swarm intelligence algorithm, which is a global optimizer that imitates the behavior of the antlion setting trap predation, which converges faster and reduces the effect of different parameter settings on the result. By using the antlion optimizer to invert the dispersion curve of the typical theoretical geological model, the inversion results show that the antlion optimizer can be applied to the inversion of the dispersion curve with high accuracy, and the advantages and practicality of the dispersion curve inversion based on the antlion optimizer are verified in the measured data compared with the traditional nonlinear methods.

In gravity inversion, traditional inversion methods usually generate smooth inversion results, that is, there are no obvious boundaries between different geological units. Fuzzy C-Means (FCM) algorithm is introduced into the inversion to solve the problem mentioned above to improve the accuracy and spatial resolution of inversion results. However, when the volume of an anomalous body is much smaller than that of the surrounding rock, and the weight coefficient of the FCM clustering term in the objective function is not selected properly, the algorithm is prone to cause uniform shrinkage of the anomaly inversion results, resulting in lower inversion accuracy, or even failure of the inversion.The main reason for the inversion failure is usually because the total volume of the anomalous bodies is much smaller than the volume of the surrounding rock.For this reason, in this paper, the scaling factor is introduced into the FCM clustering term of the objective function to balance the membership degree of the model parameters to each cluster, so as to reduce the influence of small anomalous body volume compared with the surrounding rock volume. By establishing a simple positive correlation between the scaling exponent e_k and the distance s_normal from the normalized clustering center and the real clustering center, the scaling factor ρ_k is continuously updated during the inversion process, which significantly reduces the difficulty in selecting the weight coefficient of the FCM clustering term in the objective function, and avoids the problem of volume shrinkage of the inverted anomalous bodies, thus enhancing the stability of the inversion. The numerical experiments of inversion with theoretical gravity anomaly data and actual data inversion show that the improved algorithm has higher inversion stability and accuracy compared with the previous FCM method.

It is necessary to plat the multiple-map sheet data sets into a single map when processing the geochemical data from the entire map sheet and compiling a large-scale geochemical map, but step effects might readily arise where different map sheets converge. There are currently few papers that compare and optimize various methods, and most systematic error-related studies focus on a specific way to correct and assess the step effect of geochemical data in a particular area. With the map sheet from the Yuanyi, Bajiabielichier, Goulixiang, and Zhiyi in Gouli region of Qinghai Province as a case study, this paper applies the framing standardization method, normalized method, and contrast method to perform systematic error correction and method optimization on 1∶50 000 stream sediment geochemical data and provides the effective method reference for the systematic error processing of the geochemical prospecting data of the rock cuttings. The results indicate that these three methods have distinct effects on systematic error correction.After the original data are corrected, the background difference between adjacent map sheets is basically eliminated, the step effect is effectively weakened, the geochemical zoning is continuous, the strong anomalies are appropriately suppressed, and the weak anomalies are appropriately enhanced and represented in the background. After the same element is corrected with various methods, there are differences in the anomalous area, form of anomalies, and goodness of fit with the mineral deposit (point). The goodness of fit between anomalies and known deposits (points) after correction with the framing standardization method and normalized method is 75%; the anomalies are evenly distributed throughout the region, but individual ore-induced anomalies are weakened, and the influence of invalid anomalies cannot be avoided. The nonmineral anomaly in the high background area can be effectively suppressed by the contrast method, and the mineral-induced anomaly in the low background area can be strengthened. The anomaly's goodness of fit with the deposit (point) is 87.5%, the invalid anomaly's influence is minimal, and the geological background has the maximum goodness of fit. Combined with the study on the physical geological body conditions in the region of interest, the contrast method is more suitable for the correction of systematic errors in stream sediment geochemical survey data on different map sheets in the Gouli Region and can be selected and applied in geochemical data processing under similar topographic and geomorphic conditions in Northwest China.