InSAR-derived surface deformation characteristics and mining subsidence parameters in mountain coal mines

Mining-induced surface deformation disrupts ecological balance and impedes economic progress.This study employs SBAS-InSAR with 107-view of ascending and descending SAR data from Sentinel-1,spanning February 2017 to September 2020,to monitor surface deformation in the Fa’er Coal Mine,Guizhou Province.Analysis on the surface deformation time series reveals the relationship between underground mining and surface shifts.Considering geological conditions,mining activities,duration,and ranges,the study determines surface movement parameters for the coal mine.It asserts that mining depth significantly influences surface movement parameters in mountainous mining areas.Increasing mining depth elevates the strike movement angle on the deeper side of the burial depth by 22.84°,while decreasing by 7.74°on the shallower side.Uphill movement angles decrease by 4.06°,while downhill movement angles increase by 15.71°.This emphasizes the technology's suitability for local mining design,which lays the groundwork for resource development,disaster prevention,and ecological protection in analogous contexts.

A model for extracting large deformation mining subsidence using D-InSAR technique and probability integral method

Due to the difficulties in obtaining large deformation mining subsidence using differential Interferometric Synthetic Aperture Radar （D-InSAR） alone, a new algorithm was proposed to extract large deformation mining subsidence using D-InSAR technique and probability integral method. The details of the algorithm are as follows：the control points set, containing correct phase unwrapping points on the subsidence basin edge generated by D-InSAR and several observation points （near the maximum subsidence and inflection points）, was established at first; genetic algorithm （GA） was then used to optimize the parameters of probability integral method; at last, the surface subsidence was deduced according to the optimum parameters. The results of the experiment in Huaibei mining area, China, show that the presented method can generate the correct mining subsidence basin with a few surface observations, and the relative error of maximum subsidence point is about 8.3%, which is much better than that of conventional D-InSAR （relative error is 68.0%）.

Monitoring large-area mining subsidence by GNSS based on IGS stations

In order to monitor large-area mining subsidence accurately, a high-precision global navigation satellite system （GNSS） monitoring network was established based on the nearby international GNSS service （IGS） stations taken as reference points. Given the non-linear motions of IGS stations, the robust Kalman filtering （RKF） model was presented to determine the datum of multi-period monitoring network considering the velocity and weekly solution of IGS stations. The theory proposed was applied to monitoring mining subsidence in northern Anhui coal mine in China. According to the case study, the RKF model to establish monitoring datum is better than the prediction method and the weekly solution from IGS analysis centers （ACs）, and the corresponding precision of deformation can reach up to millimeter level with 4 h observation. The research provides an efficient and accurate approach for monitoring large-area mining subsidence.

Concurrent mining and reclamation for underground coal mining subsidence impacts in China

Large scale underground mining of coal resources in China using longwall mining has resulted in ecological and environment problems, including surface subsidence that is considered serious due to competing interests of prime agricultural lands, food security, and regional economic development. The subsided lands must be rehabilitated soon after mining to be agriculturally productive to minimize loss of farmland. Similarly, precious water resources must also be managed during and after mining to protect this natural resource. Toward these goals, the concept of ＂Concurrent mining and subsidence reclamation （CMR）＂ was proposed by Professor Hu of the China University of Mining and Technology, Beijing （CUMTB）. Over the last two decades CMR concepts have evolved and successfully applied in the field in different parts of China. This innovative technology has increased available farmland during the mining process, and provided better land protection and food security in mining areas even with high groundwater table. The technology has been used in 5 of the 14 large coal bases in China. This paper describes the technology concepts, design and guiding principles for planning with two case studies from different regions to enhance its application both in China and in other countries.

Comprehensive study on ecological restoration and land exploitation of mining subsidence in suburbs of Chinese mining cities

China has nearly a hundred mining cities derived from mining development.While mining development has brought about immense achievements in a city’s economic construction,it has also resulted in different levels of damage to the eco-environment of the mining city,leaving behind a lot of subsided wasteland and heavily confining the sustainable development and transformation there.How to restore and exploit the land and eco-environment disrupted by mining development in an effective way,therefore,has become a pressing challenge that Chinese mining cities are facing.In this paper,the planning and construction of Nanhu Eco-city in the suburb of Tangshan City is analyzed as an example.After characterizing the coal-mining subsided lands in Kailuan Tangshan Mine originated in different periods and under different geological mining conditions and evaluating their safety level,the authors try to demonstrate how eco-restoration and comprehensive land exploitation should be implemented by making the best use of available local resources to achieve "economy-society-environment" sustainability and coexistence in a mining city.

Changes of Precipitation Infiltration Recharge in the Circumstances of Coal Mining Subsidence in the Shen-Dong Coal Field,China

Coal mining subsidence is a universal environmental-geological problem in mining areas. By selecting the Shen-Dong coal mining subsidence area as the research field, this paper studies the changes in precipitation infiltration recharge in the circumstances of coal mining subsidence by means of field geological investigation and laboratory simulation experiments, which is expected to provide a scientific basis for eco-environmental restoration in the mining area. The results indicate that at the unstable stage of subsidence, three types of subsidence in the Shen-Dong mining area have positive effects on the precipitation infiltration recharge, and the type of full-thickness bedrock subsidence has the greatest influence. In the stable stage of subsidence, the precipitation infiltration process after long- term drought and the moisture migration in the aeration zone undergo three different stages： evaporation-infiltration before precipitation, infiltration-upward infiltration-infiltration during precipitation and evaporation-infiltration after precipitation. During a heavy rainfall infiltration process, the wetting front movement in fine sand, coarse sand and dualistic structure of fine-coarse sand consists of two stages： the stage of wetting front movement during precipitation, in which the wetting front movement distance has linear relationship with the depth, and the stage of wetting front movement after precipitation, in which the wetting front movement distance has the power function relationship with the depth. The wetting front movement velocity is influenced by the rainfall amount and the lithology in the aeration zone. However, as the depth increases, the movement velocity will decay exponentially.

Analysis of factors and countermeasures of mining subsidence in Kaiyang Phosphorus Mine

Ground crack and subsidence were investigated in Kaiyang Phosphorus Mine as an example. Contribution factors to cause ground crack and mining subsidence were studied, including mining method, mining depth and ore thickness and stope size, dip angle of orebody, geological structure, nature of overburden and water contents, and roof supports, etc. Countermeasures against cracks and subsidence were put forward. The uniaxial compressive strength of compounded phosphorus gypsum after 28 d of curing period was tested to be more than 1 MPa. Phosphorus gypsum can be used as materials for the backfill of stope. By comparison and numerical simulation, cut and fill mining method with middle-deep drilling holes and ore transportation by blasting force was selected as the optimum mining method in Kaiyang Phosphorus Mine.

SVM model for estimating the parameters of the probability-integral method of predicting mining subsidence

A new mathematical model to estimate the parameters of the probability-integral method for mining subsidence prediction is proposed.Based on least squares support vector machine(LS-SVM) theory, it is capable of improving the precision and reliability of mining subsidence prediction.Many of the geological and mining factors involved are related in a nonlinear way.The new model is based on statistical theory(SLT) and empirical risk minimization(ERM) principles.Typical data collected from observation stations were used for the learning and training samples.The calculated results from the LS-SVM model were compared with the prediction results of a back propagation neural network(BPNN) model.The results show that the parameters were more precisely predicted by the LS-SVM model than by the BPNN model.The LS-SVM model was faster in computation and had better generalized performance.It provides a highly effective method for calculating the predicting parameters of the probability-integral method.

Quantitative prediction of mining subsidence and its impact on the environment

This study is focused on the prediction of mining subsidence and its impact on the environment in the Hongqi mining area. The study was carried out by means of a probability integral model based, in first instance based on field surveys and the analysis of data collected from this area. Isolines of mining sub- sidence were then drawn and the impact caused by mining subsidence on the environment was analyzed quantitatively by spatial analysis with Geographic Information System （GIS）. The results indicate that the subsidence area of the first working-mine can be as large as 2.54 km2, the maximum subsidence is 3440 mrn which will cause 1524 houses to be relocated. The entire subsidence area of the mine can reach 8.09 km2, with a maximum subsidence of 3590 ram. Under these circumstances the value of the loss of ecosystem services Will reach 5.371 million Yuan and the cost of relocating buildings will increase to 6.858 million Yuan.

Role of the different planting age of seabuckthorn forests to soil amelioration in coal mining subsidence land

To investigate the effects of seabuckthorn(Hippophae rhamnoides)on soil amelioration,using the space replacement method,soil physical and chemical indexes as well as the microorganism quantity and soil enzyme activities were analyzed.The results showed that:the soil bulk density of surface soil decreased and soil porosity and field capacity increased after afforestation with seabuckthorn.The plant was found to effectively reduce the soil pH,increase the soil conductivity,soil organic matters and available nutrients.Soil microorganism quantity,soil enzyme activities were both higher in 0-20 cm layer than in 20-40 cm layer.With the increase years of remediation with seabuckthorn,the quantity of soil microorganism and enzyme activities were increasing to a higher level 5 to 8 years later.Our study indicates that seabuckthorn can effectively improve soil physical and chemical properties,increase the quantity of soil microorganisms and enzyme activities,which is of great significance for the ecosystem restoration in mining areas.

Investigation and characterization of mining subsidence in Kaiyang Phosphorus Mine

In Kaiyang Phosphorus Mine, serious environmental and safety problems are caused by large scale mining activities in the past 40 years. These problems include mining subsidence, low recovery ratio, too much dead ore in pillars, and pollution of phosphorus gypsum. Mining subsidence falls into four categories: curved ground and mesa, ground cracks and collapse hole, spalling and eboulement, slope slide and creeping. Measures to treat the mining subsidence were put forward: finding out and managing abandoned stopes, optimizing mining method (cut and fill mining method), selecting proper backfilling materials (phosphogypsum mixtures), avoiding disorder mining operation, and treating highway slopes. These investigations and engineering treatment methods are believed to be able to contribute to the safety extraction of ore and sustainable development in Kaiyang Phosphorus Mine.

Limits to foundation displacement of an extra high voltage transmission tower in a mining subsidence area

Given the background of a transmission tower erected on a particular mining subsidence area,we used finite element modeling to analyze the anti-deformation performance of transmission towers under a number of different load conditions,including horizontal foundation displacement,uneven vertical downward displacement,wind loads and icing conditions.The results show that the failure in stability of a single steel angle iron represents the limit of the tower given ground deformation.We calculated the corresponding limits of foundation displacements.The results indicate that compression displacement of the foundation is more dangerous than tension displacement.Under complex foundation displacement conditions,horizontal foundation displacement is a key factor leading to failure in the stability of towers.Under conditions of compression or tension displacement of the foundation,wind load becomes the key factor.Towers do not fail when foundation displacements are smaller than 1% (under tension) or 0.5% (under horizontal compression or single foundation subsidence) of the distance between two supports.

Extracting mining subsidence land from remote sensing images based on domain knowledge

Extracting mining subsidence land from RS images is one of important research contents for environment monitoring in mining area. The accuracy of traditional extracting models based on spectral features is low. In order to extract subsidence land from RS images with high accuracy, some domain knowledge should be imported and new models should be proposed. This paper, in terms of the disadvantage of traditional extracting models, imports domain knowledge from practice and experience, converts semantic knowledge into digital information, and proposes a new model for the specific task. By selecting Luan mining area as study area, this new model is tested based on GIS and related knowledge. The result shows that the proposed method is more pre- cise than traditional methods and can satisfy the demands of land subsidence monitoring in mining area.

Characteristics of the main polluting trace elements in the water environment of mining subsidence pools

Mining subsidence pools are water bodies formed by soil subsidence near mines. We studied the impact the surrounding coal production activities and power plants have on these waters by measuring the concentrations of harmful trace elements in these waters. The concentration of the four elements F, Hg, Se and As increased by 0.92%, 0.78%, 0.70% and 0.81%, respectively, in the Datong mining subsidence pool from November 2004 to November 2006. The four elements increased by 1.58%, 1.23%, 1.08% and 0.92%, respectively, in the Xie’er mining subsidence pool and 1.16%, 1.06%, 1.02% and 1.01%, respectively, in the Pansan mining subsidence pool over the same time period. The absolute levels of F, Hg, Se and As in the pool are related to the background levels of the elements. A close relationship between nearby coal mines and power plants and increasing levels of the measured elements is noted.

Composition and distribution of main pollution trace element in water environment of mining subsidence

The impact on these water bodies of the surrounding coal production activities and the power plant through research the content and characteristics of harmful trace elements in coal contained in these water bodies.F,Hg,Se and As these four trace ele- ments increased 0.92%,0.78%,0.70% and 0.81% respectively in Datong mining subsi- dence pool from November 2004 to November 2006;the four elements increased 1.58%, 1.23%,1.08% and 0.92% respectively in Xie'er mining subsidence pool;the four ele- ments increased 1.16%,1.06%,1.02% and 1.01% respectively in Pansan mining sub- sidence pool.The conclusions show that the absolute values of F,Hg,Se and As in mining subsidence pool are relate with their background value,while the increase in their concen- tration and their environment of mine and electricity plant surrounded are closely linked.

Mining subsidence monitoring using the method of combining InSAR and GPS technology

Attempted to conduct a dynamic monitoring research on coal mining subsidence in western mining areas by using the method of combining D-InSAR and GPS technology. The observation points were installed on the main section and the three-dimensional coordinates of the points were measured by using the method of dynamic differential GPS. Meanwhile, the radar images of this subsidence area were processed by using the method of interferometry with daris software, and the interferogram of the subsidence area was obtained. Through this study, the GPS monitoring data and the InSAR deformation data were integrated and the dynamic subsidence contours of the experimental area were obtained. GPS/InSAR fusion technology provides a new technological means for large-scale dynamic monitoring of coal mining subsidence in western mountainous mining areas and shows good application prospects in coal mining subsidence monitoring and disaster warning.

MECHANISM OF WATER-SOIL COUPLED ACTION DURING MINING SUBSIDENCE

This paper,on the basis of the scientific research of engineering geological exploration in a mining area,systematically studies the reasons and influence factors of consolidation and deformation of the saturated soil included in the thick loose water-bearing overburden due to mining subsidence,and analyses the dissipation of hyperstatic pore water pressure during the change of original stress and strain state of the soil. Again,by means of the coupled model based on Cambridge model and Biot's three-dimensional consolidation theory,adopting a great many physico-mechanical parameters measured in various soil layers,the paper analyses the consolidation and deformation of saturated soil affected by mining subsidence with elasto-plastic finite element method.Thus,the research not only reveals the regulation of stress,strain,displacement and hyperstatic pore water pressure dissipation in overlying soil mass,but also opens up a new direction and way for the research of mining subsidence.

Time series prediction of mining subsidence based on a SVM

In order to study dynamic laws of surface movements over coal mines due to mining activities,a dynamic prediction model of surface movements was established,based on the theory of support vector machines(SVM) and times-series analysis.An engineering application was used to verify the correctness of the model.Measurements from observation stations were analyzed and processed to obtain equal-time interval surface movement data and subjected to tests of stationary,zero means and normality.Then the data were used to train the SVM model.A time series model was established to predict mining subsidence by rational choices of embedding dimensions and SVM parameters.MAPE and WIA were used as indicators to evaluate the accuracy of the model and for generalization performance.In the end,the model was used to predict future surface movements.Data from observation stations in Huaibei coal mining area were used as an example.The results show that the maximum absolute error of subsidence is 9 mm,the maximum relative error 1.5%,the maximum absolute error of displacement 7 mm and the maximum relative error 1.8%.The accuracy and reliability of the model meet the requirements of on-site engineering.The results of the study provide a new approach to investigate the dynamics of surface movements.

Sediment settlement rate and consolidation time of flling reclamation in coal mining subsidence land

With the continuous growth of the population and the continuous reduction of cultivated land,China’s food security is greatly threatened.In addition,China’s coal mining has been mainly underground mining,causing land subsidence and damaging existing cultivated land.This efect intensifes the contradiction between the growth of the risk population and the reduction of cultivated land.The reclamation of mining subsidence land with Yellow River sediment is often used as an efective way to improve the recovery rate of cultivated land.Shortening the reclamation time and realizing continuous flling are signifcant issues.The work presented in this paper studied the sediment settlement rate and consolidation time by combining theory,feld flling and reclamation tests and numerical simulations.A feld flling test study was carried out in the lowlands of Jibeiwang Village,Qihe County,Shandong Province,China.By calculating the drainage consolidation time,the consolidation factor of 0.015656 m^(2)/d,and the time factor for sediment consolidation of 0.575 were determined.The sediment consolidation time for this test was 9.18 days.The calculation of sediment deposition rate and consolidation time is of great practical signifcance to guide the Yellow River sediment flling,realize continuous flling,and save reclamation time and cost.

Study on Spatial Variation of Soil Moisture in Coal Mining Subsidence Area in Mu Us Sandy Land

In order to explore the spatial distribution and variation characteristics of soil moisture in coal mining subsidence area in Mu Us sandy Land,and provide theoretical basis for the restoration of the mining area,experiments based on a linear sampling and classic statistical and geostatistical methods were conducted. Spatial distribution characteristics and variation of soil moisture in the typical 0 to 100 cm dune area in the subsidence area and the non-subsidence area( control) were studied. The results showed that in the typical sand dune location of nonsubsidence area( control),the probability distribution curves of soil moisture changes in all layers along vertical and horizontal directions were all normal distribution,and it was consistent with the temporal and spatial variation characteristics of soil moisture in conventional dunes in Mu Us sandy land. By contrast,two years after the coal mine collapsed,the variations of soil moisture in different layers along vertical and horizontal directions were different,and soil moisture loss was more serious than that of control dune by nearly 10% to 30%,and the standard deviation varied from 0. 54 to 1. 05,increasing by 52. 08% compared with the non-subsidence area( control). The probability of positive and negative deviation greater than 1 was over 50%,and the coefficient of variation varied from 0. 14 to 0. 28,which was 80% higher than that of nonsubsidence area( control). After collapsing,the average level of soil moisture,standard deviation,variance and variation coefficient had greatly changed,and influence of coal mining subsidence on soil moisture was the most in the middle layer( 30-70 cm),and was not obvious in the surface( 0-20 cm) and lower layer( 80-100 cm). In coal mining subsidence area,the dispersion degree of soil moisture in different layers along the vertical and horizontal direction was greatly improved,which increased spatial variation of soil moisture.