Basin Subsidence Research Articles

Parameter Acquisition Study of Mining-Induced Surface Subsidence Probability Integral Method Based on RF-AGA-ENN Model

The mining of underground coal resources can trigger geological hazards such as subsidence basins, cave-in pits, and step cracks. In China, the probability integral method (PIM), the most popular method for predicting surface movement deformation caused by coal resource mining, has a prediction accuracy that is mainly influenced by both the measurement data (i.e., quantity and quality) from ground movement observatories and the parameter inversion method. To obtain more accurate PIM parameters in the absence of observational data, we propose a combined machine learning model (RF-AGA-ENN)—random forest (RF) extracts the best combination of features as the input layer of Elman neural network (ENN); ant colony algorithm (ACO) and genetic algorithm (GA) are combined (called AGA) for the weights and thresholds of ENN optimization. The results of the study show that (1) the RF-AGA-ENN model is used to obtain PIM values with MAXRE values between 1.94% and 9.18%, AVERY values between 0.98% and 3.98%, and RMSE values between 0.0050 and 0.9632. (2) Compared with the PIM parameters obtained from BP neural network, RF-ENN, RF-ACO-ENN, and RF-GA-ENN models, the PIM parameters obtained from the RF-AGA-ENN model have better stability and accuracy. (3) According to the PIM parameters obtained by the RF-AGA-ENN model, the predicted and measured values of surface settlement at the 11111 working face have a high degree of agreement. In summary, the RF-AGA-ENN model to obtain the PIM parameters has good application value.

Joint inversion of temperature, vitrinite reflectance and fission tracks in apatite with examples from the eastern North Sea area

AbstractAs sediment accumulation indicates basin subsidence, erosion often is understood as tectonic uplift, but the amplitude and timing may be difficult to determine because the sedimentary record is missing. Quantification of erosion therefore requires indirect evidence, for example thermal indicators such as temperature, vitrinite reflectance and fission tracks in apatite. However, as always, the types and quality of data and the choice of models are important to the results. For example, considering only the thermal evolution of the sedimentary section discards the thermal time constant of the lithosphere and essentially ignores the temporal continuity of the thermal structure. Furthermore, the types and density of thermal indicators determine the solution space of deposition and erosion, the quantification of which calls for the use of inverse methods, which can only be successful when all models are mutually consistent. Here, we use integrated basin modelling and Markov Chain Monte Carlo inversion of four deep boreholes to show that the erosional pattern along the Sorgenfrei–Tornquist Zone (STZ) in the eastern North Sea is consistent with a tectonic model of tectonic inversion based on compression and relaxation of an elastic plate. Three wells in close proximity SW of the STZ have different data and exhibit characteristic differences in erosion estimates but are consistent with the formation of a thick chalk sequence, followed by minor Cenozoic erosion during relaxation inversion. The well on the inversion ridge requires ca. 1.7 km Jurassic‐Early Cretaceous sedimentation followed by Late Cretaceous–Palaeocene erosion during inversion. No well demands thick Cenozoic sedimentation followed by equivalent significant Neogene exhumation. When data are of high quality and models are consistent, the thermal indicator method yields significant results with important tectonic and geodynamic implications.

Changes in the Landform and Water Conditions of the Industri-Alized Urban Area as a Result of Mining Activities

A particularly large accumulation of mining subsidence basins is characteristic for the Silesian Upland in southern Poland. This region is home to one of Europe’s largest coal basins. The objective of the study was to assess the subsidence process on the land surface in an industrialized urban area, as well as their impact on changes in the water cycle. Detailed studies were conducted in an area of 51.26 km2, which covers urban areas—mainly of Świętochłowice and partly Ruda Śląska and Chorzów, as well as Bytom and Zabrze. In the period 1883–1994 land surface depressions were revealed in an area of 38.8 km2, which constitutes 75.7% of the study area. In total, the endorheic areas spread over 6.9 km2. Changes in land reliefs have resulted in distinct water-cycle disturbances at local and regional levels. A generalised water-cycle scheme has been developed for the mining subsidence zone. The main directions of changes in water migration within the endorheic subsidence basin have been indicated, accounting for the situation before and after land subsidence. Consequently, this results in an average excess of 1.7 hm3 of water per year in the water cycle in these areas.

Tectonic Subsidence Modeling of Diachronous Transition From Backarc to Retroarc Basin Development and Uplift During Cordilleran Orogenesis, Patagonian‐Fuegian Andes

AbstractBackstripped tectonic basin subsidence histories are critical for interpreting phases of lithospheric deformation and paleoenvironmental change from the stratigraphic record. This study presents new subsidence modeling of the Rocas Verdes Backarc Basin (RVB) and Magallanes‐Austral retroarc foreland basin (MAB) of southernmost South America to evaluate along‐strike changes in tectonic subsidence related to the Late Jurassic through Miocene history of the Southern Andes. We compiled composite stratigraphic sections for seven basin localities that span 47°–54°S from published sedimentological records of paleoenvironment, paleobathymetry, and geochronology. Modeling results resolve regional trends in basin tectonic subsidence, uplift, and sedimentation rate that influenced the depositional environment during five broad phases of RVB‐MAB development: (a) Late Jurassic tectonic subsidence and basin deepening associated with rift‐related backarc extension that postdated regional diachronous rift‐related magmatism. (b) Southward younging of Early to Late Cretaceous pronounced acceleration in tectonic subsidence interpreted as the initiation of flexural loading and development of the MAB foreland basin system. (c) Late Cretaceous (ca. 85–70 Ma) tectonic uplift within the central foredeep ∼49° to 52°S, coeval with a shift from slope to shelf deposition at these latitudes. (d) A protracted period of low‐magnitude basin uplift and relative tectonic quiescence during the Paleogene, with the exception of southernmost localities; and (e) Synchronous latest Oligocene‐early Miocene tectonic subsidence linked to basin deepening and transgression across the northern and central basin sectors. Backstripped tectonic subsidence analysis corroborates existing interpretations for orogenic development in the RVB‐MAB and sheds new light on complex polyphase basin histories where extension precedes convergence.

Ordovician tectonic transition from passive margin into peripheral foreland in the southern Ordos: A diagnostic insight into the closure of Erlangping Ocean between the North Qinling Arc and North China Block

AbstractAchieving a reliable closure time of a back‐arc ocean is an essential aspect in studies on detailed tectonic processes of an active continental margin and arc–continent collision. This is particularly the case for the northern Qinling Orogen, which records the accretion of the North Qinling Arc (NQA) onto the North China Block (NCB) after the Erlangping back‐arc ocean closure. Sedimentological, petrological and geochronological signatures from the Ordovician successions in the southern Ordos reveal a tectonic transition from passive continental margin to peripheral foreland in the southern NCB at the beginning of Katian. Sedimentological and geochronological investigations reveal an abrupt shift of accelerating basin subsidence and deepening at the earliest Katian, separating ca. 300‐m‐thick shallow‐marine carbonate shelf assemblages from overlying ca. 2000‐m‐thick deep‐water carbonate slope and turbidite associations. Zircon age spectra of the Katian turbidites are characterized by early‐Palaeozoic and Neoproterozoic age clusters, which are different from those of the Middle Ordovician quartz arenites sourced merely from the NCB basement. Instead, these age patterns match well with those of the coeval successions in the northern NQA, indicating a spatially linked abyssal deposystem. Stratigraphic architecture deciphers a typical foreland basin geometry, involving, from south to north, northward‐propagating turbiditic wedge, northward‐backstepping carbonate slope and progressively shoaling carbonate platform, embodying foredeep, forebulge and backbulge, respectively. These characteristics of basin‐fill evolution reflect the northward migration of the flexural wave as a dynamic response to the northward expansion of the thickened NQA thrust wedge. Together with the other geological and geochronological data, our new insights indicate a southward subduction polarity of the Erlangping back‐arc oceanic crust followed by its termination at ca. 450 Ma, which was earlier than that of the main Proto‐Tethyan Shangdan Ocean between the NCB and South China Block. Our new data provide an updated view of the complex history of the Proto‐Tethys closure during the Gondwana assembly.

Novel Method for Monitoring Mining Subsidence Featuring Co-Registration of UAV LiDAR Data and Photogrammetry

Addressing the problem that traditional methods cannot reliably monitor surface subsidence in coal mining, a novel method has been developed for monitoring subsidence in mining areas using time series unmanned aerial vehicle (UAV) photogrammetry in combination with LiDAR. A dynamic subsidence basin based on the differential digital elevation model (DEM) was constructed and accuracy of the proposed method was verified, with the uncertainty of the DEM of difference (DoD) being quantified via co-registration of a dense matching point cloud of the time series UAV data. The root mean square error calculated for the monitoring points on the subsidence DEM was typically between 0.2 m and 0.3 m with a minimum of 0.17 m. The relative error between the maximum subsidence value of the extracted profile line on the main section after fitting and the measured maximum subsidence value was not more than 20%, and the minimum value was 0.7%. The accuracy of the UAV based method was at the decimeter level, and high accuracy in monitoring the maximum subsidence value was attained, confirming that an innovative strategy for monitoring mining subsidence was realized.

Post‐collisional sedimentation of the Early Mesozoic Munamdong Formation in South Korea

Post‐collisional processes cause uplift and exhumation of the overthickened crust together with the formation of sedimentary basins. To determine the influence of post‐collisional processes on sedimentation, we investigated the Early Mesozoic Munamdong Formation of the Yuljeon Basin in the Korean Peninsula, deposited immediately after the orogenic events caused by the collision of the North China Block and South China Block. Facies analysis shows that the Munamdong Formation was deposited in a streamflow‐dominated alluvial fan under tropical/subtropical climatic conditions. Vertically, the Munamdong Formation exhibits a fining‐upward trend with changes in stacking patterns, from highly amalgamated channel conglomerates to floodplain fines, indicating a progressive increase in the creation of accommodation space exceeding sediment supply. Moreover, the types of gravels in the conglomerate beds and the petrographic characteristics of the sandstones suggest that the sediments were supplied rapidly from nearby Precambrian high‐grade metamorphic rocks and Triassic post‐collisional plutons. These results indicate the supply of sediment from restricted sources, implying that the drainage basins did not widen even during intermittent quiescence of basin subsidence. We interpret the fining‐upward trend and uniform composition of sediments to have resulted from rapid uplift and exhumation of the orogenic crust, together with rapid tectonic subsidence, possibly aided by post‐collisional magmatism. This study shows that the Munamdong Formation reflects a close connection between surficial sedimentation and post‐collisional tectonic processes. This study will help to fill the gap of understanding between deep crustal processes and post‐collision sedimentation with insight into the Early Mesozoic tectonic environment of the East Asian continental margins.

Effects of multi-extensional tectonics in a cratonic area: 3D numerical modeling and implications for the Congo basin

Different hypotheses have attempted to explain the long-lasting subsidence of the intracratonic basins, characterized by prolonged intervals of low rate subsidence, alternating with episodic accelerations in subsidence rates. Among them, the Congo Basin (CB) occupies a large part of the Congo Craton, derived from the amalgamation of different cratons. Previous studies demonstrated that the CB formed from a rift phase, during the late Mesoproterozoic. This extensional phase could have been the effect of the action of a slow multi-directional extension on a cratonic lithosphere, which has induced the initial subsidence of the CB. We investigated this tectonic scenario with 3D numerical thermomechanical models, using bi-directional N-S/E-W intra-cratonic extension with uniform velocity applied for up to 200 Myr. We assumed that the amalgamation of several cratonic blocks left a rectangular region with warm and more fertile lithosphere in the model centre, having a size of 10 % or 20 % of the total model area. Numerical results show the formation of an almost circular subsided area in the central part of the model, due to the crustal and lithospheric thinning above the asthenosphere upwelling. We also observe series of topographic highs and lows inside the subsided area and significant uplift at the transition zones towards the almost undeformed cratonic parts. At a later stage (>100 Myr), the topographic depression becomes intersected by two nearly orthogonal, elongated rift structures (quadruple junction), which tend to raise their surface topography. These features well represent the first order heterogeneity characterizing the CB basement, considering that its depth has been further modified by tectonic and climatic events. The formed structures are input for static and dynamic forward gravity models and the outputs compared with the present-day gravity field. In this way, the consistency between the modelled and observed main structures of the CB is demonstrated.

Normality Test for Influence Function of Mining Surface Subsidence Based on Network Observation Station

Coal is the primary energy source in China, while underground mining is the mainstream way of coal mining. By triggering surface movement and deformation, underground mining can cause damage to arable land, buildings, roads, and so on, which is detrimental to the ecological environment in the mining area. In order to assess the severity of damage caused by this to the ground buildings and ecological environment in the mining area, it is necessary to predict mining-induced surface subsidence before the mining activities are carried out. Currently, the most used prediction method is the Probability Integral Method. It is based on probabilistic theory to mathematically demonstrate that the surface downwelling caused by underground extraction conforms to normal distribution. However, there is a lack of validation with measured subsidence basin data. Since the 1960s, China has been paying increased attention to the study of mining subsidence. However, there are still few network stations built across China to monitor subsidence basin. Herein, SPSS software is applied to re-analyze these valuable historical data. By analyzing the observation results and comparing them with the calculation results as obtained by using the probability integral method, it can be found out that the surface subsidence in the center of the subsidence basin conforms to normal distribution, not the subsidence at the edge of the subsidence basin. Therefore, it is inevitable for errors to occur at the edge of the subsidence basin when the normal distribution function is used as the mining influence function to calculate the surface subsidence. This conclusion is expected to provide practical reference for the prediction of surface subsidence in coal mines, and this experience can be extended to the mining of other solid minerals.

Decision-making fusion of InSAR technology and offset tracking to study the deformation of large gradients in mining areas-Xuemiaotan mine as an example

The multi-level disturbance of underground and surface caused by coal mining activities intensifies the deterioration of the ecological environment in the mining area. Among them, the uneven settlement caused by coal mining is the most intuitive manifestation of surface environmental damage. The uneven settlement in the mining area has the characteristics of large settlement magnitude and severe deformation. Therefore, based on 15 Sentinel-1A image data, this paper uses three methods: SBAS InSAR, continuous D-InSAR and offset tracking technology to monitor the surface deformation of the mining area. The results show that the continuous D-InSAR technology SBAS-InSAR technology is applied to the small deformation in the edge area of the subsidence basin. The mining area with low gradient subsidence of SBAS-InSAR can obtain better performance than continuous D-InSAR technology. The offset tracking technique is used to monitor the large gradient deformation in the center of the subsidence basin. Therefore, this paper proposes to expand the quantitative analysis through the spatial coherence threshold and the accuracy and successful image elements of the interference fringe displacement. Combine the advantages of the three methods and overcome the shortcomings of each method, fuse the deformation information of the three methods, and obtain the deformation law of the whole surface subsidence. The results show that the mean absolute error (MAE1-1) of continuity D-InSAR is 0.92 m, the mean absolute error (MAE2-1) of SBAS-InSAR is 0.94 m, and the mean absolute error (MAE3-1) of Offset-tracking is 0.25 m. The results of this fusion method are in good agreement with the measured data, and the mean absolute error (MAE4-1) of vertical displacement is 7 cm. Therefore, the fusion method has advantages over individual methods and provides a new idea in monitoring the large gradient deformation of coal mining subsidence in mining areas.

Deep-water Tectono-Stratigraphy at a Plate Boundary Constrained by Large N-Detrital Zircon and Micropaleontological Approaches: Peninsular Ranges Forearc, Baja California, Mexico

The distribution of sedimentary systems on Earth’s surface is intimately linked to tectonics, therefore, at plate boundaries the stratigraphic archive can unlock the timing and style of tectonism and relative plate motions. Using large-n detrital zircon and micropaleontological analyses, tied to field mapping and data collection, we unravel the timing of strike-slip motion and its influence on the development of a Cretaceous submarine canyon on a long-lived oblique-convergent margin. Structural analysis demonstrates that the canyon bedrock, composed of fluvial rocks (La Bocana Roja Fm., of maximum depositional age (MDA): 93.6±1.1 Ma), underwent both syn- and post-depositional contractional and extensional deformation during the Cenomanian-Turonian in response to dextral strike-slip movement. Relative sea-level rise associated with basin subsidence and hinterland uplift was coincident with incision and fill of a submarine canyon system (Punta Baja Fm., MDA 87.1±1.5 Ma to 84.9±2.0 Ma), which exploited structural lineaments in the bedrock. The canyon was filled by sediment derived from an uplifted magmatic arc during the Coniacian to Santonian, most likely shed from erosional topography associated with plutonic intrusions to the NE. Structural data suggest that oblique dextral strike-slip motion on the Pacific margin controlled the development and location of submarine erosion, and had ended by the earliest Santonian, significantly earlier than previously estimated. Basinward tilting led to uplift, followed by transgression and wave ravinement of the canyon fill, which was then overlain by a shallow-marine to fluvial system. Thus, the canyon was cut, filled, buried, uplifted and rotated basinward, planed off through wave ravinement, and onlapped by shallow-marine to fluvial sediments within an 8 Myr period. Our findings, in part, reconcile contrasting basin evolution models for the Late Mesozoic Pacific margin.

Crustal structure and subsidence mechanisms of the Williston Basin: New constraints from receiver function imaging

Mechanisms responsible for the long-term subsidence of intracontinental basins such as the Williston Basin in North America remain enigmatic, partly due to the thick sedimentary layer commonly found in the basins that prevents reliably imaging the deep crustal and upper mantle structures using some of the most-commonly employed seismic methods such as receiver function analysis. In this study, we used receiver functions recorded by 274 USArray and other stations in the Williston Basin and adjacent areas to investigate the layered structure of the crust in the hydrocarbon-rich intracontinental basin. After the removal of strong reverberations on the receiver functions associated with a low-velocity sedimentary layer using a recently developed time-domain deconvolution approach, two positive arrivals representing downward increases of seismic velocities are imaged beneath the basin and the area to the west. The top interface has a depth of about 40 km at the depocenter of the basin, and gradually shallows eastward to about 30 km beneath the Superior Craton, and the deeper interface has a mean depth of about 65 km beneath the Williston Basin. The layer between the two interfaces may represent an eclogitized or garnet-rich lower crustal layer. The results are consistent with the hypothesis that continuous retrograde metamorphic reactions in the previously-thickened lower crust during the Paleoproterozoic Trans-Hudson Orogeny resulted in the subsidence of the intracontinental Williston Basin.

Last Interglacial sea-level data points from Northwest Europe

Abstract. Abundant numbers of sites and studies exist in NW Europe that document the geographically and geomorphologically diverse coastal record from the Last Interglacial (Eemian, Ipswichian, Marine Isotope Stage 5e). This paper summarises a database of 146 known Last Interglacial sea-level data points from in and around the North Sea (35 entries in the Netherlands, 10 Belgium, 23 in Germany, 17 in Denmark, 9 in Britain) and the English Channel (24 entries for the British and 25 for the French side, 3 on the Channel Isles) believed to be a representative and fairly complete inventory and assessment from ∼80 published sites. The geographic distribution (∼1500 km SW–NE) across the near field of the Scandinavian and British ice sheets and the attention paid to relative and numeric age control are assets of the NW European database. The research history of Last Interglacial coastal environments and sea level for this area is long, methodically diverse and spread through regional literature in several languages. Our review and database compilation effort drew from the original regional literature and paid particular attention to distinguishing between sea-level index points (SLIPs) and marine and terrestrial limiting points. We also incorporated an updated quantification of background rates of basin subsidence for the central and eastern North Sea region, utilising revised mapping of the base Quaternary, to correct for significant basin subsidence in this depocentre. As a result of subsidence, lagoonal and estuarine Last Interglacial shorelines of the Netherlands and the German Bight are preserved below the surface. In contrast, Last Interglacial shorelines along the English Channel are encountered above modern sea level. This paper describes the dominant sea-level indicators from the region compliant with the WALIS database structure and referenced to original data sources (https://doi.org/10.5281/zenodo.6478094, Cohen et al., 2021). The sea-level proxies are mostly obtained from locations with good lithostratigraphic, morphostratigraphic and biostratigraphical constraints. Most continental European sites have chronostratigraphic age control, notably through regional pollen association zones with duration estimates. In all regions, many SLIPs and limiting points have further independent age control from luminescence, uranium series, amino acid racemisation and electron spin resonance dating techniques. Main foreseen usage of this database for the near-field region of the European ice sheets is in glacial isostatic adjustment modelling and fingerprinting Last Interglacial ice sheet melt.

Experimental study on the evolution law of mining‐induced fractures and deformation rock mass structure of gently inclined layered slope

AbstractLandslide induced by underground mining is the main type of geological disaster in Guizhou Province. The spatial position of the mined‐out area is the key factor affecting the deformation evolution of mining landslides. Three typical mining‐induced slopes in western Guizhou Province are selected to establish the engineering geological model. The orthogonal experimental design is carried out with the position of the mined‐out area relative to the slope shoulder (PM) and the slope height (SH) as variables, and the discrete element simulation test is carried out. The influence of the two variables on the evolution of overlying strata fractures and the structure of slope surface deformed rock mass is analyzed by gray relational method. The results show that under the effect of mining, the overlying strata rock on the mined‐out area gradually collapses and produces cracks through the surface. The force chain arch gradually develops from the lower part to the surface rock layer, and the slope surface rock layer is transformed from a cantilever beam embedded at one end to a multisegment articulated beam. Depending on the number of segments of the articulated beam structure, it can be divided into three categories, and the rock mass where the slope collapse occurs is mainly concentrated at the end of the multisegment articulated beam. The central subsidence of the subsidence basin, the length of the end of the articulated beam, the position of the fulcrum, and the rotation angle of the beam structure are the key indicators affecting the stability of the multisegment articulated beam. Gray relational analysis shows that PM is the primary factor to control the output of these indicators. The multiple linear regression model of gray relational degree between PM and SH was constructed, and the prediction formula of gray relational grade was obtained, which realized the multiobjective prediction of the overlying strata rock structure model under the same slope parameters. The results provide the theoretical basis for disaster prevention and mitigation of gently inclined layered mining slopes.

The spatial-temporal variations in dynamic uplift and deep mantle upwelling in the northwest South China Sea margin: Insights into continental rifting and magmatism

Complex subduction system surrounding the South China Sea (SCS) region drove vigorous mantle upwelling, however, its time and pattern are not well constrained. Hot mantle upwelling induced broad OIB-type volcanisms, caused dynamic uplift, altered basin subsidence and was consecutively recorded by strata in the SCS region. The northwest SCS margin is located in the center of diffusive igneous provinces and featured by significant subsidence anomaly and along-strike variable rifting styles and magmatism, being an ideal place to explore the time-space variations in dynamic uplift and mantle upwelling, and reveal the effects on continental rifting and magmatism via seismic interpretation, strain rate calculation and residual subsidence analysis. Results show that the margin experienced two stages of extension during the syn-rifting period (45–23 Ma), a slow strain rate (1.5e-15 to 3.5e-15) in 45–28.4 Ma and a fast, eastward increasing strain rate (4e-15 to 7e-15) in 28.4–23 Ma. Subsidence analysis reveals that the entire margin initiated dynamic uplift and mantle upwelling at ca. 28.4 Ma, then increased to ca. 23 Ma, during which continental stretching and faulting were promoted, but the syn-rifting subsidence was inhibited. In the post-rifting period, mantle upwelling remained vigorous in 23–11.6 Ma, then decayed in 11.6–5.5 Ma to generate a fast post-rifting subsidence. Spatially, the dynamic uplift of more than 1 km has a long bar shape with the wider side in the east sub-basin, implying stronger mantle upwelling occurring in the east, which well explains why higher strain rates, more symmetric rifts and intense post-rifting magmatism (23–11.6 Ma) appeared in the east. Combined with plate reconstructions, it is inferred that the mantle return flow induced by slab subduction of the proto-SCS and the following SCS caused the mantle rising in the northwest SCS margin.

Calculation of Subsidence due to Longwall Mining with Overburden Grouting and Its Application

This paper presents a prediction method of mining-induced surface subsidence due to longwall mining with overburden grouting, which has been proven an effective method to mitigate the overburden failure. This paper proposes a partial overburden grouting (POG) mining method based on surface subsidence basin inversion and innovative longwall panel layout to mitigate overburden failure and subsidence. A prediction model of surface subsidence with overburden grouting, namely, overburden grouting equivalent calculation model (OGECM), is proposed. In this study, an engineering design process and method of POG was established, the strike and dip excavation length and grouting quantity combined as critical indicators for determining the key parameter in surface basin control. In applications at the field grouting test, the surface subsidence characteristics of POG on the side of the opening line of longwall panel were investigated through surface observation station and estimated surface subsidence reduction ratio based on OGECM with grouting compared with those without. The field measurement validated the new subsidence calculation method. POG technology applied to subsidence control has effectiveness in controlling the surface subsidence to less engineering cost but expanding the applications.

Surface Microgravity Monitoring of Underground Water Migration: A Case Study in Wieliczka, Poland

Excessive water inflow in a mine poses a great threat to its operation, especially in the case of a salt mine. In 1992, a rapid outflow of water occurred in the Mina traverse in the Wieliczka Salt Mine, and a number of investigations were undertaken to assess the causes of the outflow and the condition of the rock mass, including the gravity and microgravity surveys discussed in this paper. The first of these was to investigate the rock mass with respect to its geological, hydrogeological properties and mining. The aim of study was to monitor the changes in the rock mass density and the impact of these changes on the subsidence of the ground surface. The surveys provided information on the geological structure of the study area and helped to identify possible routes for water migration. The first data confirmed density changes in the shallow parts of the rock mass, manifested by subsidence of the land surface. However, the subsequent measurements failed to show any significant density changes in the shallow parts of the rock mass, despite the subsidence of the land surface. Therefore, it can be argued that the processes in the rock mass did not cause voids in the shallow parts of the rock mass that could lead to discontinuous deformations. These processes run deep and caused only continuous deformations in the form of subsidence basins.

Spatio-Temporal Evolution Law of Surface Subsidence Basin with Insufficient Exploitation of Deep Coal Resources in Aeolian Sand Area of Western China

Coal is one of the fundamental fossil energy supporting the world’s economy. The synergistic development between efficient coal mining and ecological environment protection is the inevitable requirement for the preservation of global harmony. As the world’s largest coal producer, China has conducted a strategic shift from east to west in terms of the exploitation of its energy resources, posing a serious threat to the fragile ecological environment of the western region. In particular, the surface subsidence caused by coal mining is the root of the ecological deteriotation and the destruction of ground structures. However, it is difficult to reveal the law of large-scale surface subsidence in western mining areas merely by conventional measurement methods such as leveling, on account of the high intensity of coal seam mining, the weakness of the lithology of overlying rock and the large thickness of wind-blown sand strata. In view of this, small baseline subset interferometric synthetic aperture radar (SBAS-InSAR) technology was used in this study to obtain the time series of surface vertical displacement during the whole mining process of the 2401 working face in the Yingpanhao coal mine, Inner Mongolia. Based on the deformation data, the dynamic evolution characteristics of surface subsidence under high intensity mining in the western mining area were analyzed exhaustively. It was found that the surface subsidence is characterized by an extensive coverage range (48.52 km2) with minimal ground settlement (250 mm) in the study area. Meanwhile, the boundary shape of the subsidence basin followed a “circular-parallelogram-trapezoid” changeable process and the coverage area of the basin experienced three stages: a linear increasing period, a temporary stagnation period, and a re-expansion period. Furthermore, there existed an abnormal uplift phenomenon on the east side of the open-off cut in the 2401 working face. Combined with the structure of overlying strata, this paper carried out a preliminary analysis on the reasons of the abovementioned phenomenon. The research results are of vital realistic significance for ground buildings and ecological environmental protection in the aeolian sand mining area in Western China.

Deformation Monitoring and Spatiotemporal Evolution of Mining Area with Unmanned Aerial Vehicle and D-InSAR Technology

The extraction of underground mineral sources has a significant negative impact on the local environment, results in land surface subsidence. As far as subsidence monitoring technology is concerned, leveling is the most accurate. However, leveling can only obtain discrete point data but not the whole area information of the subsidence basin. In this study, Differential Interferometric Synthetic Aperture Radar (D-InSAR) combined with Unmanned Aerial Vehicle (UAV) technology is used to study the subsidence characteristics of the whole working panel. In this analysis, the Huainan mining area is tested as a research area; measured data are compared to the elevation accuracy of the Digital Surface Model (DSM) data, which can be considered for the subsequent works of the mining area. Based on the subsidence affected area, the ground object-type information is recorded to provide basic information for the ecological restoration work after mining so that the data before and after mining can be obtained synchronously. Finally, the differential interference results and Digital Orthophoto Map (DOM) data are combined to assess the spatiotemporal evolution of working panel subsidence and its influence on surface features. The main novelty of the proposed work is combining UAV and D-InSAR to get more accurate analysis of mining subsidence. It can be done using the proposed method.

Subsidence above gas storage in salt caverns predicted with viscoelastic theory

Based on the on-site monitoring data, the surface subsidence in the Jintan underground gas storage site has occurred continuously since the construction and operation of gas storage engineering. Therefore, the prediction of surface subsidence above gas storage in salt caverns is important to ensure the long-term safety of gas storage. Based on the mechanics theory, the formulas of elastic deformation of spherical and cylindrical caverns are derived. The Burgers viscoelastic model is used to describe the creep of rock salt. The viscoelastic analytical solution of the cavern deformation is obtained by using the correspondence principle in viscoelastic theory. It is assumed that the volume of the surface subsidence basin is directly proportional to the shrinkage volume of the cavern. The surface subsidence distribution curve is described by a Gaussian function. The spatiotemporal prediction of surface subsidence above gas storage in salt caverns based on viscoelastic theory is thus developed. The proposed theoretical model is used to analyze the surface subsidence above a gas storage cavern in rock salt in Jintan. The calculated subsidence is compared with the monitoring data. The accuracy of the theoretical model is verified by numerical simulation. The theoretical model can be used to predict the surface subsidence considering the solution stage in which the internal pressure changes with time. Results of this paper can provide guidance and suggestions for engineering practice of gas storage in salt caverns.