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In China, a substantial portion of highway asphalt pavements are no longer capable of accommodating increasing traffic volumes and necessitate renovation and expansion. Prior to commencing such activities, it is crucial to evaluate the performance of the existing asphalt pavements. This study developed a novel normal cloud framework integrating a comprehensive weighted indicator system for existing asphalt pavement. Five key performance indicators including riding quality index (RQI), rutting area ratio (Rr), cracking area ratio (Cr), patching area ratio (Pr), and pavement structural strength index (PSSI) were selected to holistically represent the pavement condition in highway renovation and expansion projects. Subsequently, a method was proposed to determine the weights of these indicators by integrating the analytic hierarchy process (AHP) and entropy. A normal cloud model was constructed to address data characteristics and representation of indicator fuzziness/randomness through digital cloud modeling. The model was applied to 12 sections of the Jingjintang Expressway (Tianjin section). The results revealed only one section where the normal cloud model differed from the pavement maintenance quality assessment (PQI) model. The 3D ground-penetrating radar detection results of this different section indicated that the normal cloud model more closely aligned with the road structure condition. Compared to absolute pass/fail criteria of the traditional PQI model, the cloud model offered enhanced sensitivity to define graded condition assessments essential for reconstruction planning and decision analysis. Therefore, the normal cloud model is more suitable for assessing the performance of existing asphalt pavements in highway reconstruction and extension projects compared to the PQI model. [ABSTRACT FROM AUTHOR]

Soil layers affect the vertical movement of moisture and salt, eventually resulting in land cover and land use pattern changes. This study explored the ability of ground penetrating radar (GPR) to detect soil layers in the modern Yellow River Delta of China and assessed its accuracy. It was found that soil moisture and salt had a strong dampening effect on the electromagnetic wave signal which resulted in blurred GPR images of the soil profile below 1 m. The cultivated soil layers of different crop types, such as rice, wheat, corn and cotton, were accurately identified in GPR images. To estimate an individual soil layer thickness, the propagation velocity of the electromagnetic wave was calculated using soil mass moisture content, and the propagation time was confirmed by comparing the GPR image with the amplitude–time plot of the soil profile. The estimated thickness was 1.02 times the thickness determined in the field and the average estimation error was 0.04 m, which was 24.09% of the soil layer thickness determined in the field. The second derivative value of envelope amplitude energy with time (SDEA) was used to describe the amplitude change in the soil layers. The SDEA has negative logarithmic and power function relationships with soil mass moisture content and electrical conductivity, respectively. The present results provide a reference database for future quantitative soil investigation in the sedimentary plain area using GPR. [ABSTRACT FROM AUTHOR]

Since Mars is far away from Earth, the propagation delay between Mars and Earth is very large. To ensure the effective use of the link transmission bandwidth, China's first Mars exploration mission has put forward a demand for data compression for all scientific payloads. The on-board mature algorithms for data compression are mainly focused on optical images and microwave imaging radar applications. No articles have been published on data compression methods that are applied to subsurface-penetrating radar. Based on the background of this application, this paper proposes a logarithmic lossy compression algorithm which can meet the mission requirements for high compression ratios of 4:1 and 2.5:1. Its compression error is less than that of the block adaptive quantization (BAQ) algorithm. The algorithm is not only easy to implement on field-programmable gate array (FPGA) platforms, but also offers simple ground decompression and fast imaging. The experimental results show that high compression ratios of 4:1 and 2.5:1 can be realized, even if the data in and between traces do not have a strong correlation. And its relative error is less than 2%, which is a new type of high-efficiency data compression method that can be implemented on-board to meet with the demand of subsurface penetrating radar. [ABSTRACT FROM AUTHOR]

Identification of slope subsurface strata for natural soil slopes is essential to assess the stability of potential landslides. The highly variable strata in a slope are hard to characterize by traditional boreholes at limited locations. Ground-penetrating radar (GPR) is a non-destructive method that is capable of capturing continuous subsurface information. However, the accuracy of subsurface identification using GPRs is still an open issue. This work systematically investigates the capability of the GPR technique to identify different strata via both laboratory experiments and on-site examination. Six large-scale models were constructed with various stratigraphic interfaces (i.e., sand–rock, clay–rock, clay–sand, interbedded clay, water table, and V–shaped sand–rock). The continuous interfaces of the strata in these models were obtained using a GPR, and the depths at different points of the interfaces were interpreted. The interpreted depths along the interface were compared with the measured values to quantify the interpretation accuracy. Results show that the depths of interfaces should be interpreted with the relative permittivity, back-calculated using on-site borehole information instead of empirical values. The relative errors of the depth of horizontal interfaces of different strata range within ±5%. The relative and absolute errors of the V–shaped sand–rock interface depths are in the ranges of [−9.9%, 10.5%] and [−107, 119] mm, respectively. Finally, the GPR technique was used in the field to identify the strata of a slope from Tanglang Mountain in China. The continuous profile of the subsurface strata was successfully identified with a relative error within ±5%. [ABSTRACT FROM AUTHOR]

In China, approximately 346.3 x 104 km² of the karst rocks are distributed, accounting for about one-third of the country's land area. Karst groundwater channels are common geological phenomena in concealed karst areas. Various karst caves and underground channels widely developed cause the complex groundwater system dominated by pipe flow, which promotes the transport of groundwater, soil, and rocks, resulting in complex geological issues for urban underground space development and utilization in karst areas. In these areas, ground collapse disasters occur from time to time. In geothermal areas, karst groundwater channels are often accompanied by frequent heat exchange, directly affecting the quality of geothermal development. Therefore, conducting exploration of karst underground channels is of great significance for the development of urban underground space and the prevention of geological disasters in karst areas. Due to the high degree of spatial variability of karst channels, it is a challenge for conventional two-dimensional detection methods to complete the geophysical imaging, which in turn results in the difficulty of conventional karst detection. Geophysical exploration is widely used due to its wide applicability, large detection depth, and accuracy. However, different geophysical methods have different advantages in terms of detection depth, resolution and practicality. The Ground Penetrating Radar has the characteristics of high efficiency and high resolution, but it is mainly applied to the exposed and shallow-covered karst due to factors such as limited penetration depth, irregular terrain, and clay content. Electromagnetic and seismic exploration can generate better results in the exploration of buried karst. In addition, microgravity exploration can be used to detect shallow karst caves and fill-type karst caves. Electrical resistivity tomography (ERT) is the most commonly used geophysical method for karst exploration, and has been applied to various karst geological environments, such as cave exploration, the exploration of water-filled karst groundwater channel, the detection of urban underground cavity, and engineering surveys. In this study, 3D ERT was used for fine detection of concealed karst underground channels in the urban area. Combining with geophysical numerical simulation and application examples, the effectiveness of 3D on karst underground channels with different filling types was analyzed. The research results show that 3D ERT has a significant improvement in data volume and resolution compared to 2D ERT. 3D ERT can more intuitively characterize the three-dimensional electrical structure characteristics of the target body and has advantages in imaging karst groundwater channels. Through the three-dimensional electrical imaging of the karst groundwater channel in Yuanquan village, Wuhan City, the groundwater migration characteristics of the low-temperature hot spring are revealed. The analyses of geophysical prospecting and drilling show that two low-temperature hydrothermal vent groups in this area are directly connected by karst underground channels and connected with north-west fault structures, reflecting a hydrodynamic process. In this process, deep hot water firstly circulates along the fault fracture zone to shallow karst channels, and after its horizontal migration at a certain distance, deep hot water exposes at the surface in the form of spring near the fracture zone, and the contact zone of carbonate rock and schist. In this study, the three-dimensional electrical structure imaging of karst groundwater channel near the hot spring point has been jointly realized by geophysical exploration and drilling, and the trends of fractured fault zone and karst channel have been displayed. Study results show that the low-temperature hydrothermal spring is connected to the karst groundwater system through deep faults. In view of this, it is proposed to carry out systematic geothermal explorationin the area to find out the hydrogeological conditions of hydrothermal spring, the groundwater circulation and heat interaction processes. In addition, the study results may provide support for the temperature increase of the hydrothermal spring and for the development of urban geothermal energy. [ABSTRACT FROM AUTHOR]

China accomplished a historic milestone in 2020 when the mission Chang'e-5 (CE-5) to the Lunar's surface was successfully launched. An extraordinary component of this mission is the "Lunar Regolith Penetrating Radar" (LRPR) housed within its lander, which currently stands as the most advanced payload in terms of vertical resolution among all penetrating radars employed in lunar exploration. This provides an unprecedented opportunity for high-precision research into the interior structure of the shallow lunar regolith. Previous studies have achieved fruitful research results based on the data from LRPR, updating our perception of the shallow-level regolith of the Moon. This paper provides an overview of the new advancements achieved by the LRPR in observing the basic structure of the shallow regolith of the Moon. It places special emphasis on the role played by the LRPR in revealing details about the shallow lunar regolith's structure, its estimated dielectric properties, the provenance of the regolith materials from the landing area, and its interpretation of the geological stratification at the landing site. Lastly, it envisions the application and developmental trends of in situ radar technology in future lunar exploration. [ABSTRACT FROM AUTHOR]

China has successfully carried out five lunar exploration missions since 2007. These missions indicate that China has successfully implemented a three-step lunar exploration program of "orbiting, landing, and returning". Among them, the Lunar Penetrating Radar (LPR) carried by the Yutu-2 rover in the Chang'E-4 (CE-4) mission is the only one still operating on the far side of the Moon. Up to now, the Yutu-2 radar has measured a large amount of scientific data, and its observations are of great significance to human cognition of the geological evolution of the lunar surface and the exploration of possible lunar in situ resources. This paper reviews the scientific results obtained by previous researchers based on the radar exploration data of Yutu-2, focusing mainly on three aspects, e.g., the geological structure of the shallow surface at the CE-4 landing site, the dielectric properties of the shallow subsurface materials and the special geological features. Finally, the prospects of Yutu-2 radar research priorities and future exploration, and the application trend of Moon-based ground-penetrating radar are given. [ABSTRACT FROM AUTHOR]

The mine roadway built in the same thick rock stratum will not change the lithologic medium in front of the roadway under the influence of the small structure of the mine, which makes the mine radar face many difficulties in structural interpretation. In the coal measure strata in southwest China, the coal seam roof is the weak aquifer of the Kayitou (T1k) group. The mine structure is the excellent drainage boundary of an aquifer, resulting in the water content of the structural belt being different from that of the surrounding rock. This paper proposes a method to identify hidden structures in mine roadways using the autoregressive and moving average power spectrum energy enveloping medium water content inversion technique. Based on the actual water content of strata in the study area, 48 roadway models are constructed. The finite‐difference time‐domain algorithm was used to obtain the forward data and calculate the volumetric water content of the model. The structure of the roadway model is accurately identified by the water content difference. In the numerical simulation study, the segmentation frequency of high‐frequency and low‐frequency envelope of the autoregressive and moving average spectrum of 100‐MHz radar antenna is determined to be 155 MHz, and the value range of water content calculation regulation parameter k is determined. The high‐ and low‐frequency envelope inversion characteristics of the autoregressive and moving average spectrum of different tunnel media models are summarized and analysed. To solve the calculation problem of energy envelope selection of autoregressive and moving average power spectrum of engineering data, the k‐nearest neighbour machine learning algorithm was used to learn and classify the power spectrum features of different tunnel models. The detection application is analysed through the whole‐rock medium and coal and rock medium roadway in the study area. The results show that the method can effectively identify the location and strike characteristics of the hidden structures in front of the roadway. [ABSTRACT FROM AUTHOR]

The epikarst together with its soil stocks (subcutaneous structure) are crucial to the fact that they may contribute to the canopy growth and can significantly influence the ecological restoration and organic carbon sequestration. Geophysical techniques especially, the ground penetrating radar (GPR) are advantageous for such investigations. However, the complicated karst environment due to numerous influencing factors (i.e., the forest, epikarst slope, peak-cluster depression, soil humidity, high voltage power lines) can significantly influence the exploration with GPR. In the past, such applications were limited to local scales without considering the aforementioned factors together. Hence, the present study analyses the influences of these factors on the performance and reliability of GPR results considering the central Guizhou plateau of south-west China as a case study. These site-specific findings are summarized into a GPR application potential zonation map at the catchment scale. The zones were rated as low, moderate and high potential degree regions, each reflecting results reliability which can be considered as a cost-effective feasibility reference for the future GPR applications in complex karst terrain characterization, as well as the areas having similar karstic conditions. [ABSTRACT FROM AUTHOR]

Lacustrine beach ridges are often used to reconstruct past lake levels. However, the sedimentary architecture involved in their sedimentary evolution remains unclear, particularly for embayed beaches. To better understand the sedimentary processes, the sedimentary architecture and geomorphology of an embayed beach on the southern of Qinghai Lake were investigated using ground penetrating radar (GPR), trenches, and modern beach observation. The embayed beach's deposits are composed of three major sedimentary facies: washover deposition, fair-weather swash deposition, and lagoonal deposition. According to the variations in sedimentary facies, the formation of the embayed beach can be divided into two stages: lake-level highstand and lake-level lowstand. During lake-level highstand stage, geomorphic changes primarily occur in the cross-shore direction. A single beach ridge with washover lobes and sheets developed along the entire embayed beach. During lake-level lowstand stage, the sediments are mainly transported alongshore within the embayed beach. The northern end shows progradational complex deposits including beach ridge, lagoon and beach system, while only a beach ridge is present at the southern end. Hydrodynamic changes in two stages lead to the heterogeneity of sediment distribution, reflected in the morphology and the sedimentary architecture. The interaction of topography and hydrodynamics controls the formation and evolution of the embayed beach. This study improves the understanding of the sedimentary processes involved in embayed beaches. [ABSTRACT FROM AUTHOR]

The Guizhou Province is located in karst mountainous area, so it is very important for the future layout and planning of the city to study the underground geological structure of the city based on seismic detection technology. In this paper, taking the underground active fault detection in the Liupanshui City, Guizhou Province, China as an example, a set of appropriate evaluation techniques for the accurate spatial location, structural characteristics and latest activities of the fault suit for mountainous area are proposed. Through pre-stack noise suppression, amplitude fidelity and consistency processing, and multiple iterative analysis of velocity residual statics, the resolution of the geological structure of the underground rock has been significantly improved. Based on the detailed interpretation of the shallow seismic data and the regional geological analysis, it is concluded that the main fault strike of the Weining – Shuicheng section of the Weining - Shuicheng fault is NW, mainly normal fault, the dip direction is mainly southwest, partly northeast and the dip angle is 60-70°. The strata of the two fault plates are strongly compressed and broken, and the limestone and dolomite are generally recrystallized, and calcite veins and masses can be seen. [ABSTRACT FROM AUTHOR]

In order to achieve a rapid and accurate identification of soil stratification information and accelerate the development of smart agriculture, this paper conducted soil stratification experiments on agricultural soils in the Mollisols area of Northeast China using Ground Penetrating Radar (GPR) and obtained different types of soil with frequencies of 500 MHz, 250 MHz, and 100 MHz antennas. The soil profile data were obtained for 500 MHz, 250 MHz, and 100 MHz antennas, and the dielectric properties of each type of soil were analyzed. In the image processing procedure, wavelet analysis was first used to decompose the pre-processed radar signal and reconstruct the high-frequency information to obtain the reconstructed signal containing the stratification information. Secondly, the reconstructed signal is taken as an envelope to enhance the stratification information. The Hilbert transform is applied to the envelope signal to find the time-domain variation of the instantaneous frequency and determine the time-domain location of the stratification. Finally, the dielectric constant of each soil horizon is used to obtain the propagation velocity of the electromagnetic wave at the corresponding position to obtain the stratification position of each soil horizon. The research results show that the 500 MHz radar antenna can accurately delineate Ap/Ah, horizon and the absolute accuracy of the stratification is within 5 cm. The effect on the soil stratification below the tillage horizon is not apparent, and the absolute accuracy of the 250 MHz and 100 MHz radar antennas on the stratification is within 9 cm. The overwhelming majority of the overall calculation errors are kept to within 15%. Based on the three central frequency antennas, the soil horizon detection rate reaches 93.3%, which can achieve accurate stratification of soil profiles within 1 m. The experimental and image processing methods used are practical and feasible; however, the GPR will show a missed detection for soil horizons with only slight differences in dielectric properties. Overall, this study can quickly and accurately determine the information of each soil stratification, ultimately providing technical support for acquiring soil configuration information and developing smart agriculture. [ABSTRACT FROM AUTHOR]

The karstification process causes mineral dissolution and mechanical removal of carbonate rocks, creating multiscale secondary porosity that greatly affects the development of karst reservoirs. The carbonate rock weathering is mainly nucleated from fractures and bedding planes and spreads out for large areas, forming a ghost-rock karst system divided by different weathering intensities. Locally, where the hydrodynamic conditions are high total removal of the weathered rock lead to the rise of the cave network and eventually the collapse or subsidence of dolines and other karst landforms. This case study presents the use of 2D and 3D GPR data to map karst levels and features in depth of a karst system in the semiarid region of NE Brazil. Synthetic GPR data and direct observation on doline crack walls support the division of karst units into ghost-rock, alterite, and residual soil zones, marked by low-amplitude reflections, and fresh to slightly weathered bedrock, indicated by vertical high-amplitude GPR zones. High-resolution aerial images and digital elevation model provide the surface geometry and distribution of karst landforms, controlled by an orthogonal weathering/fracture system identified in the GPR profiles and time slices. In addition, the karst system was vertically divided into four zones and the area of occurrence of karst units in each zone was estimated. Pore space was then calculated for each zone, assuming porosities to the filling material. We analyzed the estimated pore space distribution compared with a gas-bearing karst reservoir in China. [ABSTRACT FROM AUTHOR]

As a pavement maintenance technology, hot in-place recycling (HIR) can realize full utilization of reclaimed asphalt pavement (RAP), significantly saving non-renewable resources and project costs. However, due to variability of material properties, recycled mixtures gradation, and temperature control in construction, HIR-maintained pavement usually suffers from segregation, affecting performance and service life. To control construction quality and prolong service life, a segregation evaluation system of HIR-maintained pavement is proposed. This evaluation system, including calculation of segregation indexes, determination of segregation zones, and discrimination of segregation types, is established based on digital image processing (DIP) and surface texture distribution characteristics. In addition, it is verified by a case study of qualified HIR projects in Jiangsu Province in China. According to the empirical acceptance requirements of maintenance projects, discriminative zones for segregation types are established at 95% confidence level. Fluctuation curves of segregation indexes and image tests of four segregation types identified by segregation zones show that segregation indexes are well correlated with texture distribution characteristics and segregation degree, confirming the effectiveness and accuracy of the segregation evaluation system. Therefore, the segregation evaluation system of HIR-maintained projects proposed in this paper can realize real-time monitoring, rapid diagnosis, evaluation, and treatment decision-making of recycled pavement segregation degree. [ABSTRACT FROM AUTHOR]

The detection of lava tubes beneath the surfaces of the Moon and Mars has been a popular research topic and challenge in planetary radar observation. In recent years, the Moon–based ground penetrating radar (GPR) carried by the Chinese Chang'e–3/–4 mission, the RIMFAX radar carried by the Mars mission Perseverance, and the RoSPR radar and MOSIR radar carried by China's Tianwen–1 orbiter have extensively promoted the exploration of the underground space of extraterrestrial bodies, which is crucial for the future utilization and development of these spaces. This paper expounds on the principles, methods, and detection results of using GPR to detect lava tubes on the Moon and Mars. First, lava tubes' formation mechanism and morphological characteristics are outlined, followed by an introduction to GPR's working principles and classification. The advantages, disadvantages, and prospects of different types of radar in detecting the lava tubes are analyzed. Finally, the distribution of lava tubes on the Moon and Mars is briefly summarized, and the potential utilization of lava tubes is discussed. We believe that the GPR technique is an effective geophysical method for exploring the underground structures of the Moon and Mars, and the lava tubes beneath the surface of extraterrestrial bodies can provide important references for selecting future Moon and Mars bases. [ABSTRACT FROM AUTHOR]

As the number and length of high-speed railway tunnels increase in China, implicit defects such as insufficient lining thicknesses, voids, and poor compaction have become increasingly common, posing a serious threat to train operation safety. It is, therefore, imperative to conduct a comprehensive census of the defects within the tunnel linings. In response to this problem, this study proposes a high-speed railway tunnel detection method based on vehicle-mounted air-coupled GPR. Building on a forward simulation of air-coupled GPR, the study proposes the F-K filtering and BP migration algorithms based on the practical considerations of random noise and imaging interference from the inherent equipment. Through multi-dimensional quantitative comparisons, these algorithms are shown to improve the spectrum entropy values and instantaneous amplitude ratios by 4.6% and 11.6%; and 120% and 180%, respectively, over the mean and bandpass filtering algorithms, demonstrating their ability to suppress clutter and enhance the internal signal prominence of the lining. The experimental results are consistent with the forward simulation trends, and the verification using the ground-coupled GPR detection confirms that air-coupled GPR can meet the requirements of high-speed railway tunnel lining inspections. A comprehensive GPR detection model is proposed to lay the foundation for a subsequent defect census of high-speed railway tunnels. [ABSTRACT FROM AUTHOR]

There are rich geothermal resources in China and they are widely distributed. After years of continuous exploration and production, most of the shallow geothermal resources have been explored and the current exploration mainly focuses on deep ones. Among a great many geophysical exploration methods, seismic survey is the most effective means of geothermal resource exploration and production, but its weak seismic reflection signal, low S/N ratio and poor imaging of thermal reservoirs due to the seismic geological conditions restrict the production and utilization of deep geothermal resources. It considers through the analysis of the geophysical characteristics of the thermal reservoir that the main causes for the weak seismic reflection signals from deep thermal reservoirs are (1) the shielding effect of the strong wave impedance interface between the thermal reservoir and the caprocks; (2) the small reflection coefficient inside the thermal reservoir; and (3) the serious absorption and attenuation of high-temperature fluids such as hydrothermal fluids and steam in the thermal reservoirs by seismic waves. Accordingly, a series of seismic data acquisition technologies are proposed based on the high-precision vibroseis low-frequency shooting, high-sensitivity geophones long-spread receiving and small bin size highfold technologies, and their application in the seismic acquisition of dry-hot rocks (HDR) in Gonghe Basin, Qinghai, shows a very good application effect. [ABSTRACT FROM AUTHOR]

Ground-penetrating radar (GPR) is an established technology with a wide range of applications for civil engineering, geological research, archaeological studies, and hydrological practices. In this regard, this study applies bibliometric and scientometric assessment to provide a systematic review of the literature on GPR-related research. This study reports the publication trends, sources of publications and subject categories, cooperation of countries, productivity of authors, citations of publications, and clusters of keywords in GPR-related research. The Science Citation Index Expanded (SCI-EXPANDED) and the Social Sciences Citation Index (SSCI), which can be accessed through the Web of Science Core Collection, are used as references. The findings report that the number of publications is 6880 between 2001 and 2021. The number of annual publications has increased significantly, from 139 in 2001 to 576 in 2021. The studies are published in 894 journals, and the annual number of active journals increased from 68 in 2001 to 215 in 2021. Throughout the study, the number of subject categories involved in GPR-related research fluctuated, ranging from 38 in 2001 to 68 in 2021. The research studies originated from 118 countries on 6 continents, where the United States and the People's Republic of China led the research articles. The top five most common keywords are ground-penetrating radar, non-destructive testing, geophysics, electrical resistivity tomography, and radar. After investigating the clusters of keywords, it is determined that civil engineering, geological research, archaeological studies, and hydrological practices are the four main research fields incorporating GPR utilization. This study offers academics and practitioners an in-depth review of the latest research in GPR research as well as a multidisciplinary reference for future studies. [ABSTRACT FROM AUTHOR]

Much of the Martian surface is covered by a weathering layer (regolith or soil) produced by long-term surface processes such as impact gardening, eolian erosion, water weathering, and glacial modifications. China’s first Martian mission, Tianwen-1, employed the Mars Rover Penetrating Radar (RoPeR) to unveil the detailed structure of the regolith layer and assess its loss tangent. The RoPeR radargram revealed the local regolith layer to be highly heterogeneous and geologically complex and characterized by structures that resemble partial or complete crater walls and near-surface impact lenses at a very shallow depth. However, comparable radar data from the Lunar far side are rather uniform, despite the two surfaces being geologically contemporary. The close-to-surface crater presented in this study shows no detectable surface expression, which suggests an accelerated occultation rate for small craters on the surface of Mars as compared to the rate on the Moon. This is probably due to the relentless eolian processes on the Martian surface that led to the burial of the crater and thus shielded it from further erosion. The high loss tangent indicates that the regolith at the Tianwen-1 landing site is not dominated by water ice. [ABSTRACT FROM AUTHOR]

In recent years, China has entered a period of rapid urban development, but most of the cities with rapid development still have ground hardening, which makes it difficult for rainwater to penetrate and discharge. In order to achieve the rapid drainage of accumulated water in the city, nanotechnology was introduced, and permeable concrete based on NC and NS nanomaterials was proposed. Combined with finite element analysis, the permeable properties and mechanical properties of permeable concrete mixed with nanomaterials were analyzed. A comprehensive performance analysis of pervious concrete shows that the viscosity of permeable concrete mixed with nanomaterials is significantly higher than that of non-mixed pervious concrete, and the permeability coefficient of permeable concrete mixed with nanomaterials can reach 0.43 cm/s. A finite element analysis shows that the incorporation of nanomaterials can improve the compressive strength of permeable concrete. At the same time, under a rainwater environment simulation, the rainwater retention time of pervious concrete is only 2.35 s. The above results show that the incorporation of nanomaterials into pervious concrete can improve the water permeability of pervious concrete, improve the mechanical properties of pervious concrete, and increase its service life, which is of great significance to urban development and urban management. [ABSTRACT FROM AUTHOR]

Ground penetrating radar (GPR) has proven to be a very effective method for examining ice thickness. However, two preconditions must be met for this approach to be useful; the round-trip travel time of electromagnetic (EM) waves and radar transmission speed in the ice must be known. These issues are problematic because many factors affect radar transmission speed in ice, including impurities, physical properties such as porosity and density, and temperature. Results show that if these factors are not taken into account and a signal velocity of 0.17 m/ns in pure ice is used to estimate thickness, overestimates will result. We carried out a series of GPR surveys using dual channel host 200 MHz shielded antennas at the Toudaoguai Hydrological Station on the Yellow River, China, and collected samples to analyze ice impurities and physical properties. The results show that the ice crystal types include frazil, granular, and column at the Toudaoguai Hydrologic Station section. Our analysis of ice gas bubble and sediment content showed that the gas bubble volume content is between 11.95 and 13.0% in the frazil ice and between 7.9% and 8.6% in granular and columnar ice. At the same time, the ice sediment content ranged between 0.11‰ and 0.57‰, and the average was 0.24‰ in granular and columnar ice, which was about one-tenth that of the suspended sediment concentration in water. Additionally, a combination of GPR data as well as ice impurities, porosity, density, and temperature enabled us to provide insights on the variability of radar transmission speed and the equivalent dielectric permittivity in river ice. Our extensive observations reveal that radar transmission speed falls between 0.141 m/ns and 0.164 m/ns and that the equivalent dielectric permittivity of river ice increases in concert with ice temperature. [ABSTRACT FROM AUTHOR]

The Rover-mounted Subsurface Penetrating Radar (RoSPR) is one of the scientific payloads onboard China's first independent Mars exploration mission, Tianwen-1. The radar aims to characterize the thickness of the upper Martian soil and investigate the subsurface stratigraphy by collecting and processing the data. This article is mainly divided into two parts, the introduction of data pre-processing and analysis of pre-processed radar signals, aiming at helping scientists make more effective use of radar data. The first part describes the operating principle of the RoSPR and the procedure of radar data pre-processing at all levels. Data pre-processing is mainly designed to transfer the raw data format to a common PDS (Planetary Data System) and eliminate the influence of the instrument. In the signal analysis part, the performances of both self-check signals and echo signals of low- and high-frequency channels are analyzed, which indicate a stable radar system and are useful for background removal. Phase and time calibration is of great importance for improving data quality and making the radar data more accurate. Moreover, further processing is required to obtain clear radar images, such as filtering, background removal and gain setting. [ABSTRACT FROM AUTHOR]

Since early 2019, the Lunar Penetrating Radar (LPR) onboard Chang'e‐4 (CE‐4)'s Yutu‐2 rover has been gathering data relating to the subsurface structure of the Von Kármán crater within the South Pole‐Aitken Basin (SPA) on the lunar farside. Low‐frequency radar data have the potential of carrying geological information of about 300 m worth of strata below the traversed path. Forty‐two days' data have revealed a bifurcated structure within the layered structure beneath the CE‐4 surveying area for the first time, affecting the overlying reflectors between 90 and 310 m. This study suggests that, based on the morphological characteristics, thickness, depth (timing sequence) and direction of the newly found structure, its origin might be linked to the deposition of ejecta from the Schrödinger impact. The local stratigraphy is interpreted as consisting of distinct geological layers, corresponding to the superposition of ejecta from different impact craters, paleo‐regolith, and basaltic lava flows. Plain Language Summary: A radar (the Lunar Penetrating Radar, or LPR), built to look at the rocks below the surface, is presently traveling across an area of the lunar farside onboard a rover, called Yutu‐2 sent by China to shed some light on the striking difference between the Earth‐facing side of the Moon and its farside. So far, the radar has revealed layered structures interpreted as distinct volcanic flows, thus helping to unravel their history. The rover has been surveying the floor of the Von Kármán crater inside one of the oldest and largest impact structures of the Moon, the South Pole‐Aitken (SPA) Basin. By analyzing 42 lunar days of data, we found a new layer with a hunched upper surface and a relatively flat bottom inserted into a multilayered structure. Based on the morphology, thickness, depth, and direction of the new feature, we argue that its source could represent the ejecta deposition from one of the ancient lunar impact basins: Schrödinger. The subsurface structure revealed by the radar shows a complicated geologic history on the farside including multiple lava eruption events, the deposition of ejecta from different impact craters and weathering layers that develop during the quiescent stage. Key Points: The CH‐1 Lunar Penetrating Radar data of Chang'e‐4 reveals ∼300 m deep subsurface stratigraphy of the lunar farsideA unique bifurcated structure that resembles an ejecta discontinuity affects the overlying and underlying strataThe geologic evolution of the Von Kármán crater and the ejecta layer might be connected to the Schrödinger basin [ABSTRACT FROM AUTHOR]

Compared with other piles with the same cross-sectional area, "U-shaped" structural section sheet pile can increase the moment of inertia of the structure's section. Due to the large excavation depth of the open section of the "Yin Jiang Ji Huai" river canal project in Anhui province, China, the unprotected excavated inclined canal slope covers a large land area, which results in the current situation of high housing demolition costs and a shortage of land resources in densely populated areas. In this study, the non-destructive testing of a U-shaped sheet-pile wall to protect the vertical slope of the underwater expansive soil in the canal project is studied, which is of great significance in reducing the construction area and minimizing the cost of construction. It is necessary to test the structural integrity of the U-shaped sheet pile, which is also vital to ensuring the whole project quality. Ground penetrating radar (GPR) is used to detect the structural integrity of the U-shaped sheet pile in expansive soil. On the basis of identification and conversion of the original GPR data format, the processing methods based on the time-varying automatic gain and wavelet analysis are implemented. This case study proves that the GPR testing method is effective to estimate the quality of the U-shaped sheet pile. [ABSTRACT FROM AUTHOR]

The spatial variability in soil water content in the Daliuta mining area in western China was studied before and after coal mining using ground penetrating radar and geostatistical methods. The relationships among soil water content, soil physical properties, topographical factors, and vegetation density were analysed using classical statistics. The average surface soil water content changed slightly between the two detection events at the centre of the subsidence, from 0.084 cm3/cm3 to 0.079 cm3/cm3; there, the distribution of the soil water content was more closely related to terrain than any of the other factors being considered. Along the subsidence boundary, the surface soil water content decreased significantly after mining, from 0.099 cm3/cm3 to 0.083 cm3/cm3 at one location. The total soil porosity, soil organic matter, and soil clay content were positively correlated with soil water content before mining. However, after mining, the relationship between total soil porosity and soil water content significantly strengthened while the relationships between other soil physical and chemical properties and soil water content weakened. Vegetation was determined to be the main factor controlling the surface soil water content before and after coal mining at one location in a small (1,600 m2) area of the subsidence boundary. [ABSTRACT FROM AUTHOR]

Mars Orbiter Subsurface Investigation Radar (MOSIR) is carried by China's first Mars probe, Tianwen‐1 orbiter, investigating the Martian subsurface stratification. Surface clutter from topography off‐nadir will overlap with the subsurface echoes, which affects the recognition of Martian subsurface reflections. Surface clutter simulation can effectively distinguish the nadir and off‐nadir radar echoes. In this paper, we choose the facet method to model the Mars surface topography and combine the roughness parameter with the radar backscatter function. We also provide an analytic expression of the echo phase considering the distance variation in the whole facet. The Chinese first Mars landing site is on Utopia Planitia, which is also one of the key investigating regions of MOSIR. Therefore, we also carried on surface clutter simulation of this region and generated simulation radargram with the Chirp Scaling algorithm. Furthermore, we use the contrast method to compensate for ionospheric error introduced by the NeMars Mars ionosphere model. Our surface clutter simulation program will significantly support MOSIR subsurface investigation, and provide a chance to verify the related data processing. Key Points: Wavelength‐scale surface roughness is introduced into the proposed surface clutter simulation methodThe proposed surface clutter simulation method is applied to verify the ionospheric error correction approachEcho peak power simulated by the proposed method is in good agreement with MRO SHARAD radargram [ABSTRACT FROM AUTHOR]

Methods for the analysis and integration of multi-source geophysical datasets are fundamental technologies for three-dimensional (3D) geological modeling and subsurface mineral exploration. Such methods are critical for improving the understanding of subsurface geology, especially in an area with little prior geological information. The clustering algorithm is an important sub-paradigm of unsupervised machine learning algorithms of exploratory data structure in feature space. Traditional k-means clustering has been utilized widely for constructing 3D pseudo-lithology models from multi-source geophysical datasets due to its simplicity and robustness. This paper introduces an improved k-means clustering, namely the adaptive feature weighted k-means (AFW k-means) algorithm. The significant advantages of this proposed algorithm are that it selects the initial centroids based on feature attributes and updates automatically each feature weight during the training process. We utilized the AFW k-means algorithm to produce a 3D pseudo-lithology model in the Qingchengzi Pb–Zn–Ag–Au district, China. This study demonstrates the AFW k-means clustering can perform better than the traditional k-means clustering in 3D pseudo-lithological modeling. The 3D Early Cretaceous diorite batholith model obtained by the AFW k-means algorithm in this study can be beneficial for guiding subsurface Au exploration in the study area. [ABSTRACT FROM AUTHOR]

The gob-side roadway technology is widely used in coal mining in China, as it can improves the recovery rate of coal resources and alleviate the shortage of mining replacement. However, it is still difficult to control the stability of surrounding rock in gob-side roadway under deeper mining depth and more complex stress environment. With the auxiliary transportation roadway 30207 (ATR 30207) of the Muduchaideng Coal Mine as engineering background, this paper introduces the engineering case of gob-side roadway characterized by deep buried, long-distance, and large section. Through comprehensive methods, we studied and put forward the efficient excavation-support cooperation technology for surrounding rock of gob-side roadway. The research shows that the head-on cutting of gob-side roadway causes the stress to transfer and gradually adjust in the heading face to form a steady-state advanced abutment stress field. The coupling effect of the advanced abutment stress and the lateral abutment stress of goaf are the main reasons for repeated hole collapse of anchor cable drilling in solid coal rib, development and expansion of the roof separation fracture, and the low excavation speed. Supposed that upon the heading face support is completed, the next excavation-support cycle is quickly started during the early stage of stress adjustment, and the time effect can be fully utilized to alleviate the disturbance intensity of the advanced abutment stress in the heading face, as well as reduce the damage of rock mass. This paper puts forward the time-effect collaborative control countermeasures of the roof and rib in gob-side roadway of "hole collapse anchor cable of solid coal rib lag construction and waits for pressure relief and rapid excavation-support cycle in the heading face." Engineering practice shows that the mine pressure behavior of roadway roof and solid coal rib is effectively controlled, and the roadway forming speed is greatly improved, which can provide reference for the efficient excavation-support design of gob-side roadway under the conditions of deep buried, long-distance, and large section in similar deep mines. [ABSTRACT FROM AUTHOR]

In karst topography, hidden caves or underground rivers may imperil the safety of tunnels. It is critical to accurately detect the location and geometric shape of hidden karst caves for assessing the safety of tunnels. This paper reports a case where a large karst cave was exposed during the construction of the Nongmo tunnel in Duan County, Guangxi, China. A 2D ground‐penetrating radar survey was employed to preliminarily detect the distribution of hidden karst caves along the tunnel axis. Advanced drilling was used to obtain the velocity of electromagnetic waves and verify the 2D ground‐penetrating radar detection. Ground‐penetrating radar 3D grid detection was carried out for further detecting the geometric shape of the hidden karst caves. Rotary thrust power ratio, which is a function of drilling speed, rotating speed, propulsion pressure and torque, was proposed to reflect the integrity of the surrounding rocks. It was found that the depth of the peak value in the rotary thrust power ratio curve is consistent with that of the amplitude jump in ground‐penetrating radar A‐scans and in time–frequency distributions. The results of 3D attributes analysis indicate that due to the variation of highlights in different ground‐penetrating radar signal attributes, the obtained karst cave shapes using different attributes would be various. A multi‐attributes fusion method was proposed to generate a data volume considering various attributes. The 2D geometric shapes at different depths were obtained using the anomalous body lineament in the generated date volume slices. The 3D geometric shapes were reproduced by combining the obtained 2D geometric shapes at various depths. Based on different detection and analysis methods, the outline shape of karst caves at YK364 + 199 ∼ YK364 + 184 of the Nongmo tunnel was revealed in detail. [ABSTRACT FROM AUTHOR]

Coal mining has an important influence on the soil water content in the vadose zone. In this study, during April, August and October 2015 and June 2016, ground-penetrating radar was used to detect the soil water content of the shallow sand layer (< 10 m) of the Daliuta mining area, Shaanxi Province, China. Average envelope amplitude, auto-regression and moving average joint inversion methods were used to invert the soil water content, and the soil water content detected by ground-penetrating radar was corrected by a time domain reflectometer and laboratory measurements. The results indicated that ground-penetrating radar could measure the soil water content with an accuracy similar to that of the time domain reflectometer. The accuracy of soil water content estimates obtained by utilizing average envelope amplitude, auto-regression and moving average joint inversion methods was improved by 23.5% on average. Coal mining reduced the soil water content of the sand layer and increased the coefficient of soil water content variation. The soil water content returned to its original state after the mining settlement had stabilized, while the spatial distribution of soil water content was unable to return to its original state within a short time period. The water content of the sand layer in the centre of the subsidence basin (110–350 m) increased significantly (1.05%) after mining and was identified as the most favourable area for ecological restoration. This study provides a reference for the ecological reconstruction of subsidence areas resulting from coal mining. [ABSTRACT FROM AUTHOR]

The insulation state of high-voltage cables in coal mines directly influences the reliability of power supply in coal mines and the level of safe production. In this paper, the degradation mechanism of cable insulation is analyzed, and an online monitoring technology of cable insulation in coal mines based on decision tree is proposed, the technical principle of the judgment method of cable degradation based on decision tree is studied, the feasibility of this technology is verified through simulation, the existing online monitoring solutions for cable insulation are analyzed, and a wide-area synchronous measurement and monitoring system for cable insulation is designed. This technology has been applied in Chinese coal mine enterprises in China and achieved a good effect. [ABSTRACT FROM AUTHOR]

At present, many levees contain a large number of loose bodies as a result of poor-quality construction, biological damage and other factors. In this context, loose bodies refer to soil with a relative density less than a specified value. Taking the Huaishu River levee in China as an example, this paper studies the distribution characteristics of loose bodies in the levee using statistical methods. First, ground-penetrating radar and other geophysical exploration methods are used to investigate loose bodies in the levee. The frequency distribution and Shapiro–Wilk method are then employed to study the distribution characteristics of the area and depth of loose bodies. The influence of loose bodies on the seepage field of the levee is then examined considering the spatial distribution of the loose bodies. It was found that the areas of loose bodies in the western and eastern upstream slope obey a logarithmic normal distribution. In the shallow layer (depth 0–1 m), loose bodies appear relatively frequently, and the frequency initially increases with depth before decreasing. The maximum hydraulic gradient of the levee initially increases and then decreases as the depth of the loose body increases. [ABSTRACT FROM AUTHOR]

The complex formation process of reconstructed soil triggers the high spatial variability of soil physical properties, for which traditional soil sampling methods are not applicable due to the destructive and time-consuming modes. Ground penetrating radar (GPR) can collect continuous and high-resolution data flexibly, but the technology has rarely been employed to detect reconstructed soil properties in opencast coalmine regions. This study explored the applicability and accuracy of GPR in measuring reconstructed soil bulk density (RSBD) in southern dump, expanded western dump, and internal dump of the Antaibao open-pit mine, China. The variations of RSBD and the relationships between the dielectric constant and RSBD were analyzed based on ring knife sampling weighing, GPR detection, variance analysis, and fitting analysis. The results showed that (1) RSBD exhibited significant variations in different dumps and at different depths of the same profile. (2) RSBD differences in different dumps could be qualitatively analyzed based on the large-amplitude signals in GPR images. (3) When the soil volume moisture content ranged from 15 to 25%, RSBD was found to be negatively correlated with the dielectric constant. GPR has the potential to be widely employed to detect RSBD in reclaimed lands, which can contribute to the development of non-destructive quality testing of land reclamation. [ABSTRACT FROM AUTHOR]

The slow excavation speed of coal roadways has always been a key factor restricting the safe and efficient production of large-scale coal mines in China, and the problem of unbalanced mining replacement caused by this is widespread. This paper takes the S1231 heading face of the Ningtiaota coal mine of Shaanxi Coal and Chemical Industry Group as the research object, analyzes the characteristics of the stress evolution of coal roadway driving, reveals the principle of low-density cross-border support, and proposes a low-density cross-border support plan. Using FLAC3D to study the roadway stress-displacement evolution law of the new support scheme during the driving and mining phases, the results show that the peak stress during the driving is 5.3 MPa, and the coal pillar side stress concentration is the most obvious during the mining period, with the peak value being 7.9 MPa. The moving distances of the two banks are both 10 mm, which verifies the feasibility of low-density cross-border support. Field application shows that during roadway excavation, the amount of roof subsidence and the displacement of the two sides are 9 mm and 11 mm, respectively, and the development depth of roof cracks is controlled within 0.5 m. The overall control effect is good, and the speed of coal roadway driving is increased by 77.19% compared with the original. The new support builds a thick roof anchor structure to ensure the safety and stability of the roadway. At the same time, by reducing the number of bolts, the bolt support time has been greatly reduced, effectively alleviating the tight situation of mining replacement, and providing solutions for mines under the same conditions. [ABSTRACT FROM AUTHOR]

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Estimating resistivity distributions within dam structures accurately using electrical resistivity tomography (ERT) poses a significant challenge due to the limited 2D acquisition scheme, the 3D heterogeneity of near-surface materials, and the dynamic nature of fluid transport. To address this challenge, we present a new strategy by simultaneously inverting multiple collinear ERT datasets acquired from various standard electrode arrays. This strategy incorporates the coupling of the intrinsic parameter relationship into the objective function, constraining the inversion solution space by balancing the distinct resolution characteristics associated with the electrode arrays involved in the joint inversion process. Using synthetic Karst and infiltration models, we demonstrate that our strategy can yield accurate inversion results for both the Wenner and dipole-dipole datasets. Application of this strategy to a field case at Nanshan Dam in southeast China, which involves Wenner, Wenner-Schlumberger, and dipole-dipole surveys, successfully delineates preferential fluid seepage pathways. These findings are further corroborated by consistent inferred reflectors in Ground Penetrating Radar (GPR) profiles. The synthetic and field examples highlight the effectiveness of our strategy in achieving accurate and unified resistivity estimates by integrating multiple ERT datasets. • Multiple ERT datasets from various electrode arrays are jointly inverted. • A unified resistivity distribution across all resultant models is recovered. • The joint imaging of multiple ERT datasets is applied to detect a dam in China. • Preferential seepage pathways at the dam are delineated. [ABSTRACT FROM AUTHOR]

Integrated geophysical surveys using ground penetrating radar (GPR), seismic and electrical resistivity tomography, are carried out to characterize the subsidence, combining with engineering examples in the Glauber's salt mining area in the northwestern region of Gansu Province, China. Because some of the dissolved ore bodies in the Glauber's salt mining area are accompanied by the top and floor, the geophysical response of the floor strata has different physical properties. It is theoretically feasible to use resistivity imaging, GPR and seismic methods to detect. However, it is very necessary to choose an effective geophysical method through experimentation. the limitations of electrical resistivity tomography method and GPR are discussed: in actual work, if the electrical difference between the target body and the surrounding rock is not large enough, the conventional electrical resistivity tomography method cannot be used for fine detection; due to factors such as human noise from the mine's annex, the GPR electromagnetic wave reflection method cannot carry out effective work. Seismic refraction tomography processing is discussed and it was found that the interpretation results of refraction wave tomography can better distinguish the strata in the sub-survey area, which has an excellent effect on the delineation of the range of dissolution and collapse in Glauber's salt mine. Theory and engineering examples prove that seismic refraction wave tomography technology has good applicability in the detection of underground dissolution areas in Glauber's salt mines. [ABSTRACT FROM AUTHOR]

Tunnel lining defects are one of the most common problems that tunnels experience during operation, and they can pose severe safety risks. The most popular nondestructive testing method for detecting tunnel lining defects is ground penetrating radar (GPR), one of the basic geophysical applications. However, detection responses might differ significantly from the real shape of tunnel lining defects, making it challenging to identify and interpret. When data quality is poor, interpretation and identification become more challenging, resulting in a high cost of tunnel repairs. The improved back projection (BP) imaging and robust principal component analysis (RPCA) are used in this work to offer a GPR data processing method. Even in the event of poor data quality, our method could recover GPR responses, allowing the shapes and locations of tunnel lining flaws to be clearly depicted. With BP imaging, this approach recovers the tunnel defects' responses to better forms and positions, and with RPCA, it further isolates the target imaging from clutters. Several synthetic data demonstrate that the approach presented in this work may successfully repair and extract the positions and forms of lining defects, making them easier to identify and comprehend. Furthermore, our technique was used to GPR data gathered from the Qiyue Mountain Tunnel in China, yielding more accurate findings than the traditional method, which was validated by the actual scenario to illustrate the efficiency of our method on real data. [ABSTRACT FROM AUTHOR]

A group of Han dynasty tombs were found in a small town in central eastern China. It is difficult to infer the underground structures of the cemetery based on surface information. Geophysical methods are nonintrusive technology that can be used in archaeological excavations to provide important underground information. Multiple geophysical methods including total magnetic field (TMF), self‐potential (SP), direct‐current resistivity (DCR) and ground‐penetrating radar (GPR) were used to investigate the structure of ancient tombs. Total magnetic anomaly (TMA) and SP data can be used to obtain the projections of anomalous bodies on earth surface. DCR and GPR data can be used to gauge and further determine the spatial locations and depths of the anomalies. The results of the integrated geophysical interpretation were used to optimize the excavation plans and were verified by the subsequent works, such as coffin chambers, dromoi, ancient building foundations and funeral pit. Integrated geophysical survey can effectively reduce the uncertainly of a single method and obtain the targets more accurately. [ABSTRACT FROM AUTHOR]

This study investigated the development and formation of ground fissures at panel 12,401 of the Shangwan Colliery in the Shendong mining area, characterized by the current largest mining height and an aeolian sand surface in China. An integrated monitoring method was employed to examine the ground subsidence, distribution and development pattern of ground fissures, and the relationship between fissure width and depth, including an unmanned aerial vehicle, ground penetrating radar, and real-time kinematic and manual measurements. Then, the development and formation mechanisms of ground fissures were elucidated through theoretical analysis and physical simulation. The results indicate that ultra large mining height longwall panel extraction causes a greater ground subsidence and horizontal deformation than those of the conventions, resulting in more severe damage in the permanent margin area. The ratio of burial depth to mining height (H/M) decreases to less than 30 due to the ultra large mining height, and deep-burial panel displays the characteristics of shallow coal seam mining, such as "step subsidence". The sliding instability of the primary key stratum causes the simultaneous cutting-off of the aeolian sand layer to form step-like ground fissures. The cause of the tensile fissures is the horizontal surface deformation exceeding the deformation threshold of the aeolian sand layer, and the dynamic tensile fissures were self-restored in 2 weeks as the panel advanced. Step-like fissures connected the working face with the ground, but the depth of the tensile fissures was less than 5.0 m and increased linearly with the fissure width. [ABSTRACT FROM AUTHOR]

The North China Craton is the oldest continental block, and has suffered from large-scale lithospheric thinning and destruction, which in turn led to gold deposits in northern China. The decratonic gold deposits in the North China Craton became the most important gold deposits in China, and geophysical methods are key means to detect and discover gold deposits there. In this paper, based on the geological and petrophysical characteristics of the North China Craton, the geological model of the decratonic gold deposits is transformed into a geophysical model. At present, two methods of geophysical exploration of decratonic gold deposits are in use: rapid and efficient exploration on the scale of the ore concentration area, and large depth exploration on the scale of the deposit area. In detail, the airborne electromagnetic, magnetic and gravity methods are used to detect the shallow (1,500 m) anomaly area on the scale of the ore concentration area. Through the ground-controlled source electromagnetic and ground magnetotelluric methods, explorations for targets at significant depth (5,000 m) are carried out in the mining area. Then, taking the Liaodong ore concentration area as an example, geophysical methods are used to discover two prospecting areas around the Jianshanzi Fault in the Qingchengzi ore concentration area, Baiyun-Xiaotongjiapuzi deep prospecting area, and Qingchengzi deep prospecting area. Next, three prospecting areas are delineated around the Jixingou Fault in the Wulong mining area, Wulong deep prospecting area, Weishagou deep prospecting area, and Chang'an deep prospecting area. The anomalies in the ore concentration area and mining area are revealed by means of three-dimensional exploration methods, thereby providing technical support for the exploration of metal minerals such as decratonic gold deposits. [ABSTRACT FROM AUTHOR]

Historically, the occurrence of Froude supercritical flow and preservation of its deposits was considered rare in natural systems. Over recent years, a growing body of evidence indicates that Froude supercritical flow is a significant formative flow across the terrestrial and marine landscapes, and responsible for much of the sedimentary record from rivers to deepwater systems. This riverbank, trench, ground penetrating radar and modern riverbed dataset from the Bantanzi stream in the Daihai Lake basin, northern China, documents a linked river and delta succession dominated by sedimentary structures formed by supercritical flow. This study links the sedimentary structures in river deposits to modern bedforms in the dry riverbed, and discusses how the sedimentary structures and the supercritical flow morphodynamics change from the river to the delta front. In addition to well‐known decimetre to metre‐scale sedimentary structures produced by supercritical flow in the river deposits, centimetre‐scale sedimentary structures were found on the delta front that were quantitatively linked to deposition from cyclic step migration, utilizing a theoretical framework. This work further documents two types of clinoform geometries in delta foresets. One of these clinoform geometries is consistent with deltaic processes controlled by hydraulic jumps at the river mouth, and the other with hydraulic jumps at the base of delta foresets. Comparison with flume experiments and quantitative assessment show that ephemeral rivers, like the Bantanzi stream, are likely to produce supercritical flow also on their delta fronts, and link the supercritical flow occurrences to the highly seasonal and intense monsoon precipitation in this semi‐arid region. This work sheds light on current fundamental understanding of sediment transport and deposition processes from river to delta and highlights the effect of cyclic steps in these processes. [ABSTRACT FROM AUTHOR]

Based on an analysis of current research regarding dune migration and deformation monitoring methods, high-precision ground-based synthetic aperture radar (GB-InSAR) interferometry was used for continuous dynamic monitoring of the migration and deformation of dunes in Changli Gold Coast in Hebei Province, China, a typical area of coastal dunes. Methods for interpretation and key data processing were investigated. The results showed that the maximum deformation of dunes reached 7 mm during the monitoring period and that the deformation of the topset of the dune was greater than that of the slope foot. With GB-InSAR technology, millimeter-scale deformation can be effectively recognized. This method can be applied to monitor real-time dynamic micro-deformation of coastal dunes because of its excellent precision. It offers good application prospects if popularized and applied in coastal dune migration monitoring. This study not only enriches the research methods and content for studying coastal wind–sand issues but also provides a scientific basis for the protection and development of the study area. [ABSTRACT FROM AUTHOR]

Large-scale underground cavern projects are complicated in terms of construction technology, engineering quality, and safety. Moreover, the timely collection of vital construction information is difficult due to the complexity of the data and poor timeliness. In order to ensure the completion of construction progress and construction safety, this paper developed a real-time analysis and early-warning safety system for deep large underground caverns to automatically generate the early-warning level and corresponding emergency plans. There were two innovations involved in this system. On the one hand, a wireless monitoring and transmission platform is proposed to collect time-variable information from underground caverns. On the other hand, an early-warning safety framework is advanced, which contains abnormal recognition and early-warning information examination and verification, to support the whole-process management of integral safety for underground caverns. The system has been implemented successfully in an underground cavern construction project for Lianghekou Hydropower Station in China. The application demonstrates the proposed integration technology of real-time analysis and safety early warning can rapidly recognize abnormalities from massive monitoring data and provides a more accurate and reliable stepwise evaluation process for early warning. [ABSTRACT FROM AUTHOR]

• Many techniques were applied in Beishan Exploration Tunnel to study EDZ. • Damage process was divided into blasting damage stage and progressive damage stage. • The mechanism of micro-cracks after blasting was analyzed by the feature of AE wave. • The shape of EDZ by blasting was delineated using GPR and p-wave velocity. • Techniques used for in-situ EDZ characterization were evaluated. Detailed characterization of the Excavation Damage Zone (EDZ) is an important issue for the high-level radioactive waste (HLW) geological disposal engineering, which is closely related to the long-term safety of the HLW repository. With drill-blast experiment in Beishan Exploration Tunnel (BET, a platform for the field experiment and validation of potential technologies used for China's HLW disposal engineering in crystalline rock), systematic field tests were carried out to evaluate the suitability of techniques in characterizing EDZ, and to study EDZ characteristic in crystalline tunnel. A series of investigation technologies were used to delineate EDZ and to examine the process of its formation, which includes: p-wave velocity measurement, ground penetrating radar (GPR), acoustic emission (AE) monitoring and borehole televiewer. P-wave velocity measurement along borehole reveal that wave velocity decreased significantly (more than 10%) in 30 cm to 50 cm from the excavation surface, and this zone is defined as EDZ. Clear images of borehole televiewer were obtained, which is helpful for EDZ delineation. GPR and borehole radar were also used for EDZ delineation. Strong reflection signals were detected in the range of 10 cm to 25 cm by GPR with high frequency antenna, indicating significant changes of physical properties of rock-mass in the zone, which is defined as Highly Damaged Zone (HDZ). Moreover, the formation process of EDZ induced by blast in crystalline rock tunnel was analyzed using AE monitoring. Damage process of surrounding rock was divided into blasting damage stage and progressive damage stage. AE events location show the induced cracking activities were clustering within 30 cm to 100 cm from excavation surface. With the experience from field investigation and result analysis, the feasibility and suitability of the techniques for EDZ characterization is evaluated. Finally a specialized EDZ characterization technique system is proposed for underground research laboratory construction in crystalline host rock in Beishan area. [ABSTRACT FROM AUTHOR]

Although ground multi-branch horizontal wells can maximally connect the fractures in a coal reservoir and greatly increase the single well yield, this type of well is not appropriate in many mining areas in China, since conventional drainage and recovery must be carried out on the ground. In this work, a new coalbed methane (CBM) recovery technology is proposed, which is characterized by docking ground multi-branch horizontal wells with underground boreholes. In addition, three specific docking schemes are also given. In order to improve the efficiency of CBM recovery and avoid the huge investment of purchasing ground drainage and recovery equipment in LiuLin Block, an engineering test for connecting ground multi-branch horizontal wells with underground boreholes was carried out at the 24307 working face of the Shaqu coal mine. The engineering practice has proven that the CBM recovery technology characterized by docking ground multi-branch horizontal wells with underground boreholes captures CBM more efficiently than conventional underground CBM recovery, and it enables underground drainage and recovery when compared to conventional ground CBM recovery, thus avoiding the huge investment in purchasing ground drainage and recovery equipment, and increasing economic efficiency as well as improving the applicability of horizontal multi-branch horizontal wells. [ABSTRACT FROM AUTHOR]

Precise irrigation has been a highly urgent need to realize a quick, accurate, and non-destructive acquisition for the distribution of moisture content in reclaimed soil, particularly in coal mining subsidence areas. Consequently, traditional measurement can be replaced with Ground-Penetrating Radar (GPR), a new type of near-earth microwave remote sensing with large-scale continuous detection, fast, non-destructive, and low-cost. GPR has also been widely used in the detection of water content in soil. However, GPR is rarely used in the detection of water content in reclaimed soil, due to the complex composition of reclaimed soil and the fast attenuation of electromagnetic waves in cohesive soil. Fortunately, spectrum analysis can convert the radar data (signal change) from the time domain to the frequency domain. Energy distribution of signal frequency can be used to alleviate a large wave speed error under different media. In this study, the soil of a subsided reclamation area in Huaibei City, Anhui Province of China was taken as the research object. A control group was set up in the surrounding normal areas. The Chirp-Z-transform (CZT) was used to find the characteristic frequency. Rayleigh scattering was selected to analyze the characteristic spectrum response of radar signals under volumetric water content in soil. Various regressions were used to establish inversion models of water cut. The results showed that the frequency of peak (FP) using the Rayleigh scattering had an excellent correlation with the volumetric water content of reclaimed soil, where the correlation coefficient reached 0.90, indicating that the radar signal FP was feasible to invert the soil volumetric water content of the reclaimed area. Moreover, the CZT effectively identified the characteristic frequency in a higher resolution without changing the original frequency spectrum. The correlation coefficient between FP and soil moisture content was improved from 0.77 to 0.93, compared with the fast Fourier transform (FFT). In addition, the spectrum of radar signal in the reclaimed area demonstrated a greater drift than that in the non-reclaimed area under the same change of water content. The bulk density was also one of the factors that affect the radar signal. The highest accuracy was achieved in the exponential regression, where the verification precisions were R2 =0.84, and RMSE=1.97%, showing that the frequency spectrum analysis was an effective way to invert the moisture content of cultivated soil. When large construction equipment was used to compact the reconstructed soil, there will be a larger influence on the distribution of soil moisture content and the fertility of reclaimed soil. The findings can provide an insightful theoretical basis and technical support for rapidly monitoring the soil quality and precision irrigation in reclaimed areas. [ABSTRACT FROM AUTHOR]

With the rapid development of tunnel engineering in China, geological conditions encountered in tunnel construction are becoming more and more complex. Construction safety has become the top priority of tunnel construction. To avoid geological hazards such as landslides, water inrush, and mud gushing caused by blind construction, ground penetrating radar (GPR) is widely used in the medium distance ahead of a tunnel face. The advanced prediction of GPR is often interfered by factors such as environment, operation, data processing, image interpretation, and other factors, which cause final results to have errors. Therefore, it is highly necessary to track and test prediction effects, and also, to choose scientific and effective evaluation methods for accuracy of the prediction result. Based on the geological radar forecast data of the Yujiashan tunnel, this paper sums up the interference factors of the ground radar forecast and discusses the advantages and disadvantages of different evaluation methods. On this basis, the analytic hierarchy process (AHP) which has many applications in earth sciences, physics, nanotechnology and etc., is improved by integrating the principle of maximum membership of fuzzy comprehensive evaluation. Then, a four-level evaluation model is established, which judges the accuracy of GPR geological prediction. Meanwhile, two geological predictions in the Yujiashan tunnel are selected to be applied in the model. Finally, the recognition level of the accuracy evaluation model is more accurate. The comparison between the actual excavation exposure and the radar image interpretation results shows that the geological radar advance prediction results are more accurate. This verifies the rationality and applicability of using the improved AHP to evaluate the accuracy of geological radar advance prediction. [ABSTRACT FROM AUTHOR]

Shallow-buried high-intensity mining (SHM) activities commonly in China's western mining area will lead to the decrease of groundwater level and soil water content (SWC), which will aggravate the further deterioration of the local fragile ecological environment. In this study, the applicability and limitations of six typical soil dielectric models were comprehensively evaluated based on ground penetrating radar (GPR) technology and shallow drilling methods. Moreover, experiments were performed to test the variation of SWC in Ningtiaota minefield affected by the SHM. The results show that the fitting effect of the four empirical models and two semi-empirical models on the clay is better than that of the medium sand. Among the six models, the Ledieu model has the best performance for medium sand, and the Topp model for clay. After SHM, the shallow SWC decreases as a whole. The decreasing range is 4.37–15.84%, showing a gradual downward trend compared with the one before mining. The shorter the lagging working face distance, the greater the drop of SWC will be. The longer the lagging working face distance, the smaller the drop of SWC will be showing a gradual and stable trend. [ABSTRACT FROM AUTHOR]