Great progress has been made in the formation mechanisms of surface characteristics of gas microseepagesince the start of the 21st century, which is significant for oil-gas exploration. The microseepage in petroliferous basins is dominated by methane, which migrates nearly vertically from source rocks or reservoirs toward ground surface. The chemical, physical, and biological variation characteristics produced on the ground surface approximately reflect the oil reservoirs underground. Therefore, the methane microseepage is an objective and important part of the petroleum seepage system and has replaced microseepage as the most effective window for the tracing of underground reservoirs on the ground surface at present. Methane microseepage can be directly monitored on ground surface and in water and atmosphere, and the component concentrations and isotopic composition of methane-bearing hydrocarbon gases serve as the first-hand important data for the assessment of underground oil and gas. The data indirectly monitored mainly source from microorganisms, vegetation, minerals, radioactivity, and magnetism on the ground surface. Similar to the geochemical exploration data directly obtained, these abnormal data canbe distinguished from the background values of the ground surface far away from the oil reservoirs, and the distribution areas of the anomalies will become important targets of favorable exploration areas. It will play an increasingly important role in the future integrated oil and gas explorationto gain in-depth understanding of methane microseepage mechanisms, avoid single monitoring method and one-sided understanding, transform ideas to adoptsurface integrated monitoring methods, and establish new mathematical analysis systems.

Airborne geophysical techniques represent a cost-effective way for obtaining insights into the crustal geology of the Antarctic. Based on the analysis of the history of Antarctic airbrone geophysical survey and development of facilities and fly-platform applied in the survey, this paper gives a review of the leading scientific application topic of airborne geophysical data i.e.,the crustal structure of Antarctica,the reconstruction and restoration of ancient terrains, magmatism and volcanism identification,and the interaction between Antarctica Ice Shelf and bed rock, which shows that airborne geophysical survey provides effective technical support for Antarctica geosciences research.Our research shows that there is still a blank area for geophysical survey. Based on out review, the combination of airborne magnetic, airborne gravity and ice radar data has provide a new solution to the interaction study of Antarctic Ice shelf and bedrock.

With the increasing demand for oil and gas resources,the exploration and development of oil and gas fields have shifted from conventional to unconventional fields,and tight oil and gas reservoirs have become the current and future focus of the exploration and development of unconventional oil and gas.Most of the tight reservoirs in China are continental sediments with poor lateral continuity,strong vertical heterogeneity,complex lithology,and large changes in physical properties.All these make it difficult to effectively characterize the pore structure of tight reservoirs.The pore structure of reservoirs not only affects the occurrence of oil and gas but also seriously restricts the seepage and efficient exploitation of oil and gas.To analyze the pore structure characteristics of tight reservoirs in a targeted manner,this study systematically investigates relevant literature on the assessment methods of pore structure of tight reservoirs and organizes indirect measurement methods such as semi-permeable plate,direct observation methods such as casting thin sections,and digital core method.Moreover,it dissects the logging-based assessment methods of the pore structure of tight reservoirs,explores the applicability,advantages,and disadvantages of these methods,and further proposes the development trend of pore structure study based on the current status.

This paper collected surface soil above the known concealed deposit the Luoboling porphyry-type copper-molybdenum deposit and acquired samples of ore and surrounding rocks from typical boreholes of the deposit. Then, it analyzed the changes in the contents of six trace elements (Cu, Mo, Ba, Pb, Zn, and V) and the isotopic composition of S and Pb, aiming to verify the ore prospecting effects of the measurement technology of mobile forms of metals in soil and full analysis of fine-grained soil in concealed deposits and to identify the sources of surface geochemical anomalies according to the isotopic composition of Pb and S. The study results are as follows. The total analysis of fine-grained soil showed the best effects in indicating deep ore bodies in the Luoboling deposit, and the areas with high contents of Cu, Ba, and Mo correlated strongly with the distribution of deeply concealed ore bodies. Both the mobile forms of metals in the soil and the total analysis of fine-grained soil showed that it is quite possible that concealed ore bodies occur below sampling points No.14 and 15. Meanwhile, the changes in the contents of V, Pb, and Zn obtained using both methods can accurately delineate the scopes of mineralized rock masses close to the ground surface. However, most of the total sulfur isotopic composition in the soil of anomaly zones inherits from the non-ore-hosting surrounding rocks and masked the contribution from the deep ore bodies. Consequently, sulfur isotopes showed poor effects in indicating the sources of anomalies in the surface soil in the Luoboling deposit. Therefore, it is more reasonable to measure the sulfur isotopic composition according to the mobile forms of metals in the soil. In contrast, the total Pb isotopes in the soil of the anomaly zones inherit the characteristics of the Pb isotopes of deep ore bodies. This serves as direct evidence of full analysis of fine-grained soil in the mineral exploration of coverage areas.Moreover, the changes in the ²⁰⁶Pb/²⁰⁴Pb ratio in the full analysis of surface fine-grained soil correlated strongly with the distribution of underlying concealed ore bodies and thereby can effectively indicate the deep concealed ore bodies.

Based on the systematic collection of information of rare earth element (REE) deposits in North China, this paper analyzes the current situation of REE resources and the temporal-spatial distribution regulation of REE deposits in North China.The mineralization types of the REE deposits in North China mainly include sedimentary and metamorphic type, igneous carbonate magma type, magmatic hydrothermal type, pegmatite type, andion-adsorption type. Given thegeotectonic locations and ore-controlling factorsof REE deposits in North China, the geodynamic background favorable for the formation of the REE deposits includes the ancient metamorphic basement, Archean-Paleoproterozoic rift zones on continental margins, Middle Proterozoic rift zoneson continental margins, and Yanshanian active continental margins in coastal areas of the West Pacific. Thetectonic-sedimentary-magmatic prospecting favorable conditions include volcanic-sedimentary events during the early development of regional deep faults and geosynclines and the magmatic activitiesof alkaline syenitesand alkaline granites. Meanwhile, the geochemical background favorable for REE mineralization consists of high precipitation amount, alluvial plains, and brown soil distribution areas.

As an important part of the Tianshan metallogenic belt in Central Asia, Kyrgyzstan boasts rich mineral resources and completely types of mineral resources. The national scale (1∶1 000 000) geochemical mapping of Kyrgyzstan covers an area of about 170 000 km² across the country and the analyses and tests of 69 elements. It has filled in the blank of national geochemical mapping in Kyrgyzstan and will provide basic geochemical data for studies on basic geology, mineral development, environmental protection, and agricultural production inthe country. According to the regional geologic and structural evolution and geochemical background, the study area is divided into five structural geochemical regions. According to the geological background and the statistical analysis of geochemical parameters of major metallogenic elements, it is considered that Kyrgyzstan is a metallogenic favorable region of Au, Cu, Pb, Sb, Sn, W, and Ag, with notably distributed geochemical anomalies. In detail, the northern Tianshan Mountain shows high anomalies of Au, Cu, Pb, Zn, Ag, Be, and As. The middle Tianshan Mountaincan be divided into the eastern and western parts with the Fergana fault as the boundary. Among them, the western part is rich in Au, Cu, Cr, Mo, and Co, while the eastern part is rich in Au, W, Sn, Co, Cr, and Ni. As for the southern Tianshan Mountain, the western part is characterized by the concentrated distribution of Cu, Co, Cr, Ni, Au, As, Sb,and Hg, while the eastern part is characterized by the distribution of W, Sn, and Bi associations. The analytical results of metallogenic significance are as follows.The Chattkar area in middle Tianshan Mountain is considered the area with the highest prospecting potential in Kyrgyzstan. It has enormous potential for the prospecting of Cu, Pb, Au, and W. It is followed by the Zarejaz area in the eastern part of the southern Tianshan Mountain, which also has great prospecting potential and is highly favorable forthe prospecting of Au, CU, W, and Sn. Besides, the western part of the southern Tianshan Mountain and the Talas-Narun area also enjoygood prospecting potential and are prospecting favorable areas of gold, copper, lead, and zinc polymetallic deposits.

Jiaodong area is one of the major gold producing areas in China, and the deep prospecting in this area is to seek deep breakthroughs and blind spots at present. With the gold concentration area in Jincheng Town in Laizhou City and Ershilidian Town in Haiyang City as an example and based on the prediction and assessment theory and method of deep gold resources, this study summarizes the deep spatial characteristics and relationships of the Archaeozoic-Mesozoic intrusive rocks, Precambrian metamorphic basement, and the strata in Jiaolai Basin in the area and the deep morphology and characteristics of major ore-controlling structures in the area. To this end, section measurement was carried out using the integrated geophysical exploration of high-precision gravity survey, high-precision magnetic survey, and magnetotelluric sounding. Meanwhile, the obtained gravity, magnetic, and resistivity data were comprehensively researched and analyzed in combination with previous results. This study will provide a basis for the late prospecting prediction of deep gold deposits and related researches of the area.

The glutenite reservoirs of the Paleogene Wenchang formation in the Lufeng oilfield in the eastern South China Sea are characterized by complex lithology,low porosity,and strongly heterogeneous pore structure.Since different types of reservoirs show greatly different seepage characteristics,traditional permeability models are difficult to meet the demand for petroleum production and development due to their low calculation precision.Flow units can effectively characterize the internal seepage characteristics of reservoirs.However,the division of flow units based only on flow unit indicators will lead to misclassification.Given the macro and micro hierarchical heterogeneity of reservoirs of the Wenchang Formation,this study establishes a multi-level division method of flow units by combining geological,logging,and core data.Specifically,the first-order flow units are determined according to sedimentary facies.Then the second-order flow units are determined according to the lithology identified by calibrating conventional logging based on core and imaging logging.Finally,the third-order flow units are determined using flow zone indicator (FZI) approaches combined with pore structure.In this manner,a three-level division method of flow units based on sedimentary microfacies-lithology-pore structure is formed.As indicated by application results,this method can effectively avoid the inaccurate classification of flow units and improve the accuracy of permeability calculation,thus having great significance for finding high-quality reservoirs and the efficient development of oil reservoirs.

The Yangshuiwu buried hill is located in the northern part of the Langgu sag,where fractured porous reservoirs are well developed.As indicated by comprehensive geological studies,it is in the direction favorable for hydrocarbon migration and accumulation.However,owing to the deep reservoirs and low imaging accuracy of seismic data,it is difficult to predict effective reservoirs using conventional attributes and the obtained prediction results feature strong multiplicity of solution.Based on full analyses of the geophysical response characteristics of existing drilled wells,this study selects three optimal attributes sensitive to the response of effective reservoirs,namely mean amplitude,variance,and arc length,and calculates the correlation coefficient between the thickness of effective reservoirs and each of the optimal attributes.Then it determines the fusion weight of each attribute according to corresponding correlation coefficient,and finally obtains the fused attribute than can reflect the thickness of effective reservoirs.The fused attribute can be used to effectively reduce the multiplicity of solution compared with single attribute prediction and quantitatively predict effective reservoirs.Practice has proved that the multi-attribute fusion technology is effective and practical and has achieved accurate application results in the Yangshuiwu buried hill.

Shallow seismic reflection (SSR) surveys are an indispensable method in the exploration of urban underground space.Their exploration effects are affected by many aspects such as excitation,receiving factors,acquisition parameters,and processing methods,which should be systematically scientifically demonstrated and selected according to geological tasks.Taking an underground space exploration project in Jinan as an example,the authors discussed the method of improving the resolution of SSR surveys.Through the comprehensive analysis of the collected data,a reasonable seismic geological model was established.Based on this model,the forward analysis and illumination analysis were performed using the fluctuation equation of seismic data acquisition parameters,obtaining a high-density two-dimensional seismic observation plan.Meanwhile,high-resolution reflection images were obtained through the study on targeted data processing techniques such as pre-stack denoising,deconvolution,and velocity field optimization.Excellent exploration results have been achieved in the project.This study will provide reliable geophysical exploration data for the construction of the smart city in Jinan,and can serve as references for the implementation of SSR exploration in this area in the future.

It is critical for climate, water resources, ecology, and engineering construction in China to accurately assess the three-dimensional distribution and periodic change of permafrost. Permafrost is mainly distributed in high-elevation regions in China. Therefore, the surface geophysical prospecting suffers from low efficiency, high cost, and poor transportation in determining the thickness of permafrost in China. In contrast, the airborne electromagnetic methods using resistivity difference enjoy great advantages. This study established a geoelectric model based on the thickness and resistivity of permafrost in Qilian area, Qinghai Province. Then, by simulating the thickness and resistivity of permafrost, low resistance layer under permafrost, flight height, and changes in the angles of receiver coils, this study analyzed the differences in electromagnetic responses under different conditions obtained from one-dimensional forward modeling using time-domain and frequency-domain airborne electromagnetic systems AeroTEM and Impulse. Based on this, this study assessed the capability of airborne electromagnetic methods to detect the top and bottom interfaces of permafrost. According to the simulation results, frequency-domain airborne electromagnetic system Impulse can determine the top interface of the permafrost covered by a marsh, wetland, or moist meadow according to the thickness of melted permafrost under a low noise level. In comparison, time-domain airborne electromagnetic system AeroTEM can determine the bottom interface of the permafrost, with the determination accuracy significantly improving when low-resistivity layers occur beneath the permafrost. Therefore, the top and bottom interfaces of permafrost can be jointly determined using frequency and time-domain airborne electromagnetic data. The results of this study will provide theoretical support for the future application of airborne electromagnetic methods to permafrost surveys in China.

NMO correction is an important step in seismic data processing, but it will produce the wavelet stretching distortion effect in the process of correction. With the increase of offset, the dominant frequency will decrease and the amplitude will increase.Due to stretch distortion, the in-phase axis is not leveled, leading to non-in-phase stacking, which will lead to frequency distortion and resolution decrease of horizontal stacking profile. Therefore, stretch correction is the key to improve the resolution of horizontal stacking profile.The stretching distortion of wavelet is incoherent in the curved sparse domain, and the stretching correction can be regarded as a nonlinear optimization process.By measuring the sparsity of the data in the sparse domain, a fast and effective algorithm is used to optimize the nonlinear problem generated by the wavelet stretching distortion, and finally the purpose of eliminating the wavelet stretching distortion is realized.The curved sparse transform stretching correction method can eliminate the wavelet stretching distortion caused by NMO correction, recover the high frequency information at the far offset and level the in-phase axis.Combining model data and actual data processing, the curved wave sparse stretch correction method can significantly improve the resolution of horizontal superposition profile.

Gravity anomaly continuation from undulating surface to plane can provide gravity data on a flat horizontal plane for frequency-domain data processing and inversion. Based on the theory of conventional interpolation-iteration methods, this study proposed a modified interpolation-iteration method by introducing a correction factor of the undulating observation surface in the iteration and correction process. The improved method accelerated the iterative convergence speed and promoted the continuation effects. The theoretical model-based tests show that this method can be used to achieve stable and effective large-span gravity anomaly continuation from greatly undulating surface to plane. The continuation results presented by this method are better than those obtained using conventional interpolation-iteration methods. The application of Bouguer gravity anomaly data of the Sichuan-Yunnan region demonstrates that the modified interpolation-iteration method effectively enhanced anomalous signals and details and can provide reliable data for subsequent processing and interpretation.

One of the pivotal tasks in energy and resources exploration is identifying geological boundaries such as petroliferous structure, ore-controlling faults, and rock mass boundaries. The edge recognition of gravity and magnetic potential data has unique advantages in the detection of geological boundaries, and has become an indispensable and important means in energy and resources exploration. We have combined interface inversion and normalized vertical derivative of the total horizontal derivative (NVDR_THDR) for potential field data to improve the effect of the potential field edge recognition method for deep small-scale geological bodies. Firstly, we invert the gravity anomaly using density interface inversion method to make the anomaly more prominent of the small-scale geological structures, then the NVDR_THDR technique is used as an edge extraction and enhancement method to deal with the density interface inversion result. The results conducted with rifted basin model and the isolated bodies model show that the proposed method has obvious advantages of edge enhancement and can balance the deep and shallow anomalies to some extent. The real gravity data test of the northern Ordos Basin also show that our method can detect the small-scale faults in the basement of the basin, which indicates that this method can be successfully used in real data processing.

When the magnetic resonance sounding (MRS) method is applied in an environment with high electromagnetic noise, the signal-to-noise ratio of the measured data is often reduced due to the interference of electromagnetic noise. As a result, it is difficult to accurately determine the aquifer distribution using the inversion results, thus reducing the application effects of the method. In this paper, aiming at the common problem of multi-source harmonic noise interference in the field data acquisition using the MRS method, this paper derives the grid search simultaneous removal method based on the model denoising and further proposes the more efficient simulated annealing simultaneous removal method. The simulation results show that both methods can effectively suppress multi-source harmonic noise. Compared with the grid search simultaneous removal method, the efficiency of the simulated annealing simultaneous removal method is improved by 2.35 times in the case of double fundamental frequency harmonics, which greatly reduces the time cost of the denoising process. Meanwhile, the simulated annealing simultaneous removal method allows for great denoising effects of multi-source harmonic noise. Finally, the proposed denoising algorithm was applied to a field example. The comparison of the inversion results and borehole data shows that the simulated annealing simultaneous removal method can effectively suppress the multi-source harmonic noise in the measured data obtained using the MRS method and can significantly improve the application effects of the method.

The Longmaxi Formation is one of the major exploration horizons of shale in China at present. The gas-bearing sediments in the Lower Paleozoic Longmaxi Formation in the Yangtze area, South Sichuan are characterized by low resistivity. Therefore, it is difficult to distinguish the gas-bearing sediments from aquifers only using logging response. Given this, this study investigated the genetic mechanisms of low-resistivity gas-bearing sediments in the study area in depth using existing data of conventional logging, core drilling, and production-related dynamic conditions, as well as a large number of core analyses and experiments, including casting thin sections, QEMSCAN, and X whole-rock diffraction. According to the study results, three major controlling factors in the low-resistivity gas-bearing sediments of the Lower Paleozoic Longmaxi Formation in the Yangtze region, South Sichuan include the additional conductivity of clay minerals, the complete graphitization of over-mature organic matter, and the distribution pattern of organic matter laminae. The practical application results indicate that the low-resistivity gas-bearing sediments in the study area were formed due to the organic matter laminae developing and the partial graphitization of organic matter. That is, the low resistivity of the shale gas reservoirs tends to be caused by the mutual superimposition and effects of multiple factors. Therefore, it is necessary to analyze the geological, logging, and core data according to various zones and horizons and employ the correlation between upper and lower horizons and between adjacent wells to determine the major controlling factors of the low resistivity of the shale gas reservoirs.

The occurrence and development characteristics of concrete cracks are important characterization parameters of concrete health. Given that steel reinforcement is the inherent structure of concrete, this paper proposes a method for monitoring cracks in concrete using steel reinforcement antennae. In this method, a steel reinforcement transmitting and receiving antenna pair embedded in concrete is set, and the cracks in concrete are detected according to the amplitude of the antenna pair' parameter S₂₁ that can reflect electromagnetic wave propagation. To this end, a simulation model based on the CST Studio Suite software was constructed to calculate the amplitude of S₂₁ using the software. The relationship between the amplitude of S₂₁ and the crack state was analyzed. The results show that the state of cracks in concrete has a significant impact on the amplitude of S₂₁, and thus the cracks can be detected according to the characteristics of the amplitude of S₂₁. The cracks can be identified if the ratio between the amplitude of S₂₁ obtained using the models with and without cracks exceeds a certain threshold. Meanwhile, the corresponding frequency band that can identify the cracks is defined as the characteristic frequency band of cracks. The simulation results show that the amplitude of S₂₁ significantly changes with different crack thickness, crack angles, and crack positions. Therefore, the concrete cracks and their characteristics can be judged from the amplitude of S₂₁ by setting up a steel reinforcement transmitting and receiving antenna pair in concrete.

3DVSP common detection point gathers produce different tensile distortion effects at different offsets after conventional processing,especially at the shallow layer and large offset,which affects the imaging quality of the superimposed section.In view of such a situation,the author analyzed the stretch effect reason,deduced the stretch rate formula,and proposed a trace-set cutting method based on stretch rate:to calculate the stretch rate of each point in the trace set of common detection points point by point,determine the range of effective stretch rate,and cut the points with excessive stretch rate.The results of model analysis and actual data processing show that the method is correct and effective.

In marine oil and gas exploration,for the purpose of accurately acquiring the high-precision and high-resolution reflection information of the exploration target and realizing more delicate imaging,broadband acquisition and processing technology of marine seismic has been greatly innovated and developed in recent years.In this paper,the generation mechanism of ghost wave,the classification and characteristics of ghost wave and its manifestation in actual seismic data are studied.The high-resolution radon transform in frequency domain is used as the main processing method to attenuate ghost wave in a broad-band data of a straight slant cable.After the ghost wave suppression processing,the source ghost wave and cable ghost wave of seismic data have been greatly attenuated,and the notch energy has been significantly enhanced.The broadband processing not only broadens the low-frequency component of seismic data,but also broadens the high-frequency component of seismic data;especially,the low-frequency component energy has been significantly enhanced.This method has achieved good results in the application of marine seismic data.

This paper focuses on the forward modeling of the direct current resistivity method. To this end, the Gmsh software-a 3D finite element grid generator-was used to model the anomalous bodies under undulating terrain and conduct relevant irregular grid division. Then partial grid data generated by Gmsh were applied to a 2.5D finite element forward modeling program, and the forward calculation results were analyzed using the well-ground joint observation method. The analytical results show that good effects can be obtained by using irregular grids to fit the undulating terrain and using the well-ground joint observation method to explore the geological conditions under the undulating terrain. The effects of the valley terrain on the anomalous response below using different observation devices were also studied. The results achieved are practically significant and they also prove that the Gmsh software has great application value in the forward modeling and meshing based on the finite element method.

The transient electromagnetic (TEM) method is widely used in coalfield hydrogeological exploration and goaf investigation in China. However, due to the characteristics of the method itself, the vertical resolution of the ground device is low, and thus it is impossible to realize the fine detection of goaves. In a goaf exploration project of a coal mine in Shanxi Province, a simple goaf model of coal measure strata was established according to the study on cores and logging curves, as well as previous experience of electrical exploration. Based on this, numerical simulation was conducted for the ground TEM response of goaves with and without water in a homogeneous half-space and the ground-well TEM response of three-dimensional horizontal thin plates. As confirmed by the characteristics of the ground and ground-well TEM response of goaves in some practical cases, the ground-well TEM has high vertical resolution, which provides an idea for fine exploration of goaves.

The magnetoelectric resistivity (MMR) method is a type of electromagnetic exploration method popular in China in recent years. It enjoys technical advantages in detecting long highly conductive geological bodies such as underground seepages. However, it is yet to be widely applied since it suffers poor anti-interference ability and is liable to be affected by external noises. In recent years, the pseudo-random signal technology has been widely used in the field of geophysical exploration. It allows noises to be reduced through the convolution operation of impulse and step responses, thus greatly improving the anti-interference ability. Based on the exploration principle of the magnetoelectric resistivity method and the principle of the pseudo-random identification system, this paper proposes the method of applying the pseudo-random signal technology to the magnetoelectric resistivity method to improve the anti-interference ability of the latter. Meanwhile, it analyzes the anti-interference effects through leakage model-based experiments, which have verified the feasibility of the proposed method. As indicated by the experimental results, the proposed method has remarkable noise reduction ability and can roughly eliminate the interference of external magnetic fields. Meanwhile, the relative errors at peaks above the leakage channel were less than 3%, indicating extremely strong anti-interference ability. This study lays a basis for the future development of related detection instruments.

The UAV aeromagnetic survey technology has continuously developed and gradually applied to different geomorphic landscape areas. This study aims to verify the application effects of the UAV aeromagnetic survey technology in the desert and semidesert regions in China. To this end, the applicability tests of UAV types were performed according to the characteristics of the natural environment in the desert and semidesert regions. Then the applicability of multi-rotor UAVs and vertical take-off and landing fixed-wing UAVs in the desert and semidesert regions was assessed from the ability to resist wind, terrain-following ability, battery life, efficiency, and the quality of data acquisition. Through the qualitative and quantitative comparative analysis of the results obtained from UAV aeromagnetic surveys and ground magnetic surveys, the practicability and reliability of the UAV aeromagnetic survey technology in the desert and semidesert regions in West China was measured. It is considered that UAV aeromagnetic survey technology enjoys the advantages of high precision of data collection and high efficiency compared to the ground magnetic survey. Therefore, the UAV aeromagnetic survey technology is worthy of widespread application as a geophysical prospecting method and technique.

This study proposes an EMI array sensor based on differential reception, which can effectively improve the comprehensive performance of the EMI system on a vehicle or robot in terms of soil adaptability, positioning accuracy, and anti-interference ability. The EMI array sensor consists of a large transmitting coil and multiple receiving coils, which are horizontally arranged in the transmitting coil. Meanwhile, the receiving coils are a kind of double-D coils to realize differential reception. In this manner, the detection efficiency of unexploded ordnances (UXO) can be effectively improved using the EMI array sensor. The simulated minefield detection test results show that the array sensor proposed in this study can be used for UXO detection and positioning.

Multi-channel gamma-ray spectrometers are necessary for measuring natural and artificial radionuclides. The core of the multi-channel gamma-ray spectrometers is the multi-channel pulse amplitude analysis, which determines the resolution and analysis accuracy of radionuclides. This study introduces the working principle of a multi-channel pulse amplitude analyzer based on linear discharge and describes the methods for analyzing pulse amplitude and obtaining spectrum peaks. Secondly, this study details the design methods of eight important parts of the multi-channel pulse amplitude analyzer, including the design basis, design idea, and feasible schemes. Finally, this study details the logical sequence diagram of the analyzer, laying a foundation for readers to design a multi-channel pulse amplitude analyzer. Using the working principle, design method, and working logic sequence diagram presented in this paper, as well as modern high technology, readers can develop a new type of modern multi-channel pulse analyzer with uniform channel width, excellent differential nonlinearity, and improved resolution of radionuclides, thus better serving the society using gamma-ray spectrum data with higher energy resolution and high measurement accuracy.

Based on the comprehensive collection of samples from the alkaline soil in the Shizuishan area, Ningxia, this study analyzes the geochemical indicators of selenium and available selenium in soil in the area.The results are as follows. The seleniumin soil in the study area is mainly originated from the black rock series in the Helan Mountain area, followed by siltation brought in by the agricultural irrigation water diverted from the Yellow River. The bioavailability of selenium in the study area is at a relatively high level, and the effective selenium enrichment and above covers 79.2% of the whole study area, with an area of about 777.2 km². The content of different forms of selenium is in the order ofresidualselenium>strongly organic matter-bound selenium>humic acid-bound selenium>ion exchangeableselenium≈water-soluble selenium > carbonate-bound selenium≈iron manganese oxide-boundselenium. The total selenium content is limited, while thewater-soluble selenium content is relatively high. The higher the total nitrogen and organic matter content in soil, the higher the total selenium and available selenium content. As the salt content in soil in the study area increases, the bioavailability of seleniumtends to gradually increase. The irrigation-silted soiland thefluvo-aquic soil with a pH value between 7.5 and 9 have moderate total selenium content and high available selenium content, and they are high-quality areas for planting selenium-rich agricultural products.

Copper (Cu) is an essential trace element for the human body. However, there is no recommended value for Cu content in crops in China, and there is no standardon Cu content in soil for developing Cu-rich land resources. This paper takes the Huaying Mountain-Xicao cultivated land areas in Linshui County, Sichuan Province as the study area. Based on the survey results of the Cu contents in surface soil, crops, and root soil obtained from the 1∶50 000 land quality geochemical survey, this study investigated the contents and distribution of Cu in soil and crops and analyzed the influencing factors of the biological enrichment coefficient (BAF) of Cu in corn seeds. Moreover, it established a BAF prediction model of Cu in corn seeds and proposed the optimal ranges of Cu contents for developing Cu-rich corn and land resources. The study results are as follows. The Cu content in the surface soil of the study area ranges from 3.33×10^-6 to 173×10^-6, with an average and a median of 26.85×10^-6 and 25.60×10^-6, respectively. The soil with high Cu content is mainly distributed in the areas in Huaying Mountain in Linshui County where basalts, carbonate rocks, and carbonaceous shales are soil-forming rocks. In contrast, the soil with low Cu content is distributed in areas in Xicao where Jurassic sandshaleserves as soil-forming rocks. The Cu content in corn seeds in the study area ranges from 0.80×10^-6 to 2.71×10^-6, with an average and a median of 1.76×10^-6 and 1.82×10^-6 respectively. To ensure the safety of human beings in terms of Cu intake, the optimal Cu contents in corn seeds and soil in the study area should be 0.756×10^-6~10.080×10^-6 and 12.67×10^-6~169.00×10^-6, respectively.

Based on the heavy metal content data of 1 308 deep soil samples taken from the 1∶250 000 geochemical survey of land qualityin the Bijie area, Guizhou Province, the content distribution and geochemical background characteristics of heavy metals in soil in the area were studied. The geochemical background values of heavy metals in soil in northwestern Guizhou Provinceare significantly higher than those in soil nationwide but are close to those in soil in southwestern China. The heavy metal content in soil in northwestern Guizhou is closely related to the geological background and is significantly different between different geological units. The soil developing in Carboniferous strata has high geochemical background values of Pb and Zn, while the Middle Permian soil formed due to weathering hashigh geochemical background values of Cd and Hg. All these mean that besides heavy metal pollution in soil caused by zinc melting using indigenous methods,another important factor causing the heavy metal enrichment is the high geochemical background values of heavy metals in soil.The statistics show that the management target value of Cd in the Middle Permian weathered soil in northwestern Guizhou is higher than thecontrol value (2.0×10^-6) of Cd stipulated in the Risk Management Standard for Agricultural Land for Soil Pollution in China. It is considered that the differences in geochemical background values of heavy metals in soil between different geological units and their impacts on the ecological environment should be fully considered when determining the management target values of heavy metals in soil in northwestern Guizhou Province.

According to the characteristics of thin eluvium and poor topographic conditions in research area,this paper analyzes the suitability and effectiveness of multi-channel transient surface wave and microtremor survey technology in investigating slope internal structure of the typical slope in Luniao Town,Yuhang District,Hangzhou Ctity.The dispersion curve is extracted using frequency-wave number (F-K) and spatial autocorrelation method(SPAC).Based the velocity profile,the surface silty clay with breccia,completely weathered tuff,strongly weathered tuff and medium-slightly weathered tuff is interpreted.The results show that the surface wave exploration can effectively distinguish the internal structure of slope covered by thin eluvium.Both multi-channel transient surface wave and microtremor survey have a high accuracy in depth interpretation of the interface between strongly weathered and medium-slightly weathered tuff,which is well consistent with the borehole data,and there is a little bit of error in depth interpretation of the interface between surface silty clay with breccia and completely weathered tuff.The data analysis also shows that the fitting relationship between spatial autocorrelation function and Bessel function J₀ is good when frequency less than 15 Hz,and the accuracy lose when it is higher than 15 Hz.Furthermore,the microtremor survey velocity is generally lower than the multi-channel transient surface waves exploration velocity.

The Sichuan-Tibet Railway under construction has a large number of tunnels under high geotemperature and high in-situ geostress.How to improve the accuracy of advanced geological prediction of these tunnels is a major difficulty in railway construction.Taking the Tunnel Seismic Prediction (TSP) method for advanced geological prediction as an example,analyses reveal that there are two major problems in the detection of the tunnels.On is that the use of emulsion explosives and plastic detonating tubes in blastholes under a high rock-temperature is liable to cause misfires,thus affecting data acquisition.The other is that the wave velocity differences between the excavated and unexcavated areas of tunnels under high in-situ geostress are not considered in data processing.Targeting these problems,this paper proposes six improvement measures,namely researching and developing detonation packs with a thermal insulation bag,establishing intelligent engineering assessment systems based on multiple geological information,changing the models of shock initiation of the TSP,popularizing new technologies and methods of advanced geological prediction,researching and developing advanced geological prediction systems suitable for Tunnel Boring Machines (TBMs),and improving the organizational management of geological prediction.All these measures can provide references for efficient detection of advanced geological prediction of tunnels in areas with high geotemperature and high in-situ geostress.