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Abstract Laying long horizontal borehole (LHB) in mining‐induced strata fractures for coal‐bed gas drainage in the goaf is a pivotal method for eliminating safety hazards, preventing atmospheric pollution, and realizing gas utilization. A crucial premise of this method is to determine the effective drainage range of the borehole, a key parameter directly affecting boreholes spacing and drainage efficiency. In this study, a model of gas seepage during LHB drainage within a circular equipotential boundary was presented, and the complex variable function theory and the mirror principle were adopted for deriving the complex potential function of gas flow under the condition of LHB drainage and the drainage volume function of a single center borehole. Besides, the main indicator to determinate the effective drainage range of LHB was given. Specifically, the indicator refers to the distance between the turning point (the point at which the change rate of the gas flow velocity is −0.002 around the borehole) and the center of the borehole. Subsequently, numerical simulation was conducted to obtain the effective drainage range of LHB within mining‐induced fractures of overlying strata, that is, 4 m

Abstract The gases released by underground coal mining pose a threat to mine safety, lead to resource wastage, and contribute to environmental pollution. Employing long horizontal boreholes (LHB) for gas extraction proves to be an effective solution. However, accurately determining the LHB's position within the overlying rock strata is challenging due to complex mining and geological conditions. This study introduces a novel “zone‐position” method for identifying the optimal LHB placement, utilizing both physical simulation tests and theoretical analysis. The approach comprises two steps. Initially, it identifies the appropriate LHB layout zone within the overlying strata. It delineates four subzones within the fractured zone, among which the stable fractured subzone (SFSZ) is identified as the most favorable for LHB placement. The boundaries of the SFSZ are also defined. Subsequently, the method focuses on pinpointing the LHB's precise location within the SFSZ, proposing a criterion that considers gas accumulation, strata permeability, and LHB stability. Application of this method in engineering projects demonstrates that the gas extracted by LHBs accounts for about 60% of the total gas emission. Furthermore, the volume of gas extracted at the optimal LHB location reaches up to 5.52 m3 min−1, triple that of other locations.

The empirical relationships between tensile strength, mode I and mode II fracture toughness obtained by previous studies have the problem of a small amount of data for fitting, and more data are needed for further study. There is a discrepancy between the theoretical prediction and the experimental results of the relationship between mode II and mode I fracture toughness. Because of this, a review is conducted to determine the relationships among tensile strength, mode I fracture toughness, and mode II fracture toughness from the data gathered from the available literature. The results indicate that the mode I and mode II fracture toughness have linear relationships with tensile strength with the linear coefficient of 0.141 and 0.219, respectively. The linear coefficient between mode II and mode I fracture toughness is 2.389, indicating that the classical mixed mode criteria are mistaken the empirical relationship between mode II and mode I fracture toughness. The microcracking mechanism and failure model are quantified and compared in detail among tensile test, mode I and mode II fracture toughness tests based on moment tensor. It found that the nature of the source can be related to each other, which gives some light on the reason for the existence of certain relationships between these macroscopic parameters from a microcracking perspective.

The loblolly pine (Pinus taeda L.) is one of the most profitable forest species worldwide owing to its quick growth, high wood yields, and strong adaptability. The AP2/ERF gene family plays a widespread role in the physiological processes of plant defense responses and the biosynthesis of metabolites. Nevertheless, there are no reports on this gene family in loblolly pine (P. taeda). In this study, a total of 303 members of the AP2/ERF gene family were identified. Through multiple sequence alignment and phylogenetic analysis, they were classified into four subfamilies, including AP2 (34), RAV (17), ERF (251), and Soloist (1). An analysis of the conservation domains, conserved motifs, and gene structure revealed that every PtAP2/ERF transcription factor (TF) had at least one AP2 domain. While evolutionary conservation was displayed within the same subfamilies, the distribution of conserved domains, conserved motifs, and gene architectures varied between subfamilies. Cis-element analysis revealed abundant light-responsive elements, phytohormone-responsive elements, and stress-responsive elements in the promoter of the PtAP2/ERF genes. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of potential target genes showed that the AP2/ERF gene family might play a critical role in plant growth and development, the response to environmental stresses, and metabolite biosynthesis. Utilizing quantitative real-time PCR (qRT-PCR), we examined the expression patterns of 10 randomly selected genes from Group IX after 6 h of treatments with mechanical injury, ethephon (Eth), and methyl jasmonate (MeJA). The AP2/ERF gene family in the loblolly pine was systematically analyzed for the first time in this study, offering a theoretical basis for exploring the functions and applications of AP2/ERF genes.

Abstract Traditional cemented paste backfilling continues to face the shortcomings such as paste leakage, poor adaptability to geological structures and insufficient roof-contact. To solve the limitations, a novel L-shaped cemented paste backfilling (LCPB) technology was proposed in this study. It is to set L-shaped filling zones and partition zones in the goaf to perform interval and multiple filling. A mechanical model was established to calculate backfilling body strength, widths of L-shaped filling zones and partition zones and backfilled ratio and etc. The results of a case study showed that: (1) The LCPB mining has a high backfilled ratio, without prominent ground pressure. The maximum values of roof-to-floor convergence of the working face and roadway were 58 mm and 259 mm, respectively. It could effectively control the deformation of surrounding rock and achieve roadway retention. (2) When the floor strata were intact, the maximum floor damage depth was less than 4 m, and the floor near the fault was 10–12 m. The secondary lift height of the confined water was about 5 m near the fault. The LCPB mining allows for safety mining above a confined aquifer. (3) The maximum surface inclination and curvature were 1.75 mm/m and 0.06 mm/m2, respectively. The draw angle was 11.3°, and the subsidence factor was 0.085. The ground surface deformation was reduced to be less than that allowed in the first level of the building damage (inclination and curvature of 3 mm/m and 0.2 mm/m2, respectively).

The mining of the part of the inclined ore body below a goaf is crucial for improving resource extraction and safe production. In this study, the cementation properties of crushed stone during the mining of the inclined ore body were investigated by means of laboratory experiments, theoretical analysis, and numerical simulation. Additionally, orthogonal experiments were performed to assess how factors like water–cement ratio, crushed-stone particle size, and cement–sand ratio affect the strength of the grouting concretion body (GCB). Furthermore, the fluidity of the slurry under different ratios was also measured. Considering both the fluidity of the slurry and the strength of the GCB, the optimal ratios of the slurry were determined to be a water–cement ratio of 2.5:1 and a cement–sand ratio of 1:4. This ratio was then used for crushed-stone cementing under the poorest crushed-stone particle size conditions, based on which mechanical parameters were obtained from experiments. Theoretical analysis equated the problem of the grouting range to the width of the plastic zone of surrounding rock, and a conclusion was reached that the width of the GCB should be at least 29 m. The numerical simulation results reveal that among 30 mining rooms formed below the GCB, 24 mining rooms are in a stable state and 6 mining rooms are partially damaged on a small scale. As a whole, the GCB formed by grout filling into the goaf manages to effectively support the stope below, and it is verified that the theoretical calculation method of the width of the GCB is feasible.

The pressure-relief gas drainage in longwall mining goaf is an important part of the simultaneous extraction of coal and gas in the green mining technology system. The horizontal-directional long boreholes arranged in overlying strata for pressure-relief gas drainage have been widely used in recent years. The boreholes in mining overburden are different from the high drainage roadway and ordinary high-level boreholes. When the pressure-relief gas is extracted from the overburden of goaf, the boreholes response and sensitivity to the mining overburden damage and gas migration have some significant particularities. Through theoretical analysis, numerical simulation and engineering example verification, the position characteristics and pressure-relief gas drainage mechanism of horizontal-directional long boreholes in mining overburden were studied. The technical principle of extracting pressure-relief gas by horizontal-directional long boreholes was described. Combined with laboratory tests and numerical simulation, three position characteristics of hori-zontal-directional long boreholes were analyzed. The gas accumulation degree at the borehole area is high, which provides the concentration conditions for borehole gas drainage. The fractures at the borehole area are relatively developed, which provides gas source guarantee for borehole drainage. The stratum at the borehole area is less affected by mining, which provides stability conditions for the borehole. On this basis, the drainage mechanism of horizontal-directional long boreholes was revealed from three aspects: the degree of gas accumulation in mining fractures, the permeability of mining strata and the stability of mining boreholes. The theoretical criteria for determining the position of horizontal-directional long boreholes was proposed, and the method for determining the position of the boreholes drainage was given, which were verified by numerical simulation and engineering examples. The research results show that according to the borehole position criteria, the maximum pure volume of gas drainage of the borehole arranged is 2.59 m3/min, which is 2.56 times that of other comparative boreholes. Affected by horizontal-directional long boreholes drainage, the maximum gas volume fraction in return airway is 0.11%−0.72%, and the gas volume is 0.69−2.79 m3/min, which verifies the reasonability of pressure-relief gas drainage based on the position determination method of horizontal-directional long boreholes. The research results can provide a technical basis for the layout of horizontal-directional long boreholes to extract the pressure-relief gas in goaf, thereby improving the pres-sure-relief gas extraction rate and promoting the development of green mining technology of the mine.

Recovery of the coal buried under buildings, railways and water bodies and the residual coal in irregularly arranged fully mechanized mining faces is a common engineering problem facing underground coal mining. In this study, a mining technology of continuous driving and gangue backfilling (CDGB) was proposed. The technology, which can not only alleviate ground subsidence and gangue discharge, but also release the above-mentioned coals, contributes to green and efficient sustainable development of mining. The stability of the system of the solidified body-reserved coal pillar combination (S-C combination) is crucial to the CDGB technology. Therefore, it is of great significance to explore the mechanical and damage characteristics of S-C combination in the synergistic bearing process. First, four sets of different-shaped S-C combination specimens were fabricated and a S-C combination bearing structure in CDGB was constructed to explore the differences in mechanical characteristics and damage modes of different-shaped S-C combination specimens during CDGB. Subsequently, their surface strain field evolutions and acoustic emission (AE) response characteristics in the load-bearing process were obtained with the aid of the digital image correlation technique and the AE signal monitoring system. Furthermore, a damage evolution model based on AE parameters and mechanical parameters was established to clarify the damage evolution law. The following results were obtained: (1) The free area of S-C combination can serve as a quantitative index to evaluate the stability of the overburden control system; (2) The concept of critical value k of the free area was first proposed. When the free area exceeds the critical value k (free area ratio greater than 1.13), the deformation resistance and the free area changes becomes negatively correlated; (3) As the free area expands, the failure of the S-C combination specimen evolves from tensile failure to shear failure. The distribution characteristics of the axial strain field also verified such a change in the failure mode; (4) When the free area expands, the peak AE count gradually changes from “double peaks” to “a single peak”. In this process, the expansion of free area shortens the time for accumulating and releasing energy during loading. Micro cracks generated in the specimen change from a phased steep growth to a continuous increase, and the process in which micro cracks develop, converge, intersect and connect to form macro cracks accelerates. The damage evolution law concluded based on AE parameters and mechanical parameters can well characterize the damage evolution process of S-C combination, providing certain reference for the study on the synergistic bearing of S-C combination during CDGB.

The characteristics of surface subsidence under the condition of repeated mining in weakly cemented strata are of great significance to the safe and efficient mining and ecological restoration of coal resources in weakly cemented mining areas in western China. Theoretical analysis, similar simulation, numerical simulation and field monitoring are used to study the migration law of overlying strata and surface subsidence model under repeated mining conditions in weakly cemented strata, and the model is applied in engineering. The bulking characteristics of weakly cemented rock and the influence mechanism of repeated mining overburden strata movement on surface subsidence are discussed through theoretical analysis. The ‘maximum surface subsidence model under the condition of repeated mining in weakly cemented strata’ is established. There is a linear relationship between the bulking coefficient of weakly cemented rock, the mining thickness of lower coal and the maximum surface subsidence of weakly cemented strata. Through similar simulation and numerical simulation, the characteristics of repeated mining overburden and surface subsidence in weakly cemented strata are analyzed. The research results show that the development law of the separation height of the initial mining and repeated mining of the weakly cemented strata is basically the same, and both show a step-like rise. The surface subsidence curve of repeated mining is asymmetrically distributed, and the maximum subsidence value is biased towards the side of open cut. The maximum development height of overlying strata, the maximum surface subsidence value and the surface subsidence coefficient after initial mining and repeated mining are given. The established maximum surface subsidence model is used to predict the maximum surface subsidence value on site. The predicted value of the maximum surface subsidence model is similar to the measured value on site during the mining process of the working face, which verifies the rationality of the ' maximum surface subsidence model under the condition of repeated mining of weakly cemented strata '. At the same time, the predicted value of the maximum surface subsidence after the mining of the working face can provide a reference for the actual work on site.

In-depth understanding of the influence of different hole defect structures on the dynamic mechanical properties and fracture behavior of rocks is an important theoretical guidance for the design of roadway support, rock engineering stability evaluation and mine pressure bump dynamic disaster prevention. The dynamic fracture behavior of limestone specimens containing different hole defects under impact loading was investigated. The fracture characteristics of the limestone specimens containing double-hole and crack were tested under impact conditions by using a split Hopkinson pressure bar (SHPB) impact loading system. The whole process of dynamic crack initiation, propagation and penetration was recorded by the high-speed camera. The dynamic compressive strength, dynamic deformation modulus, failure mode and crack extension behaviour of the double-hole limestone under impact loading were further analyzed by combining image processing method. The results show that the peak strain of specimen varies from 0.00297 to 0.00493 when the double-hole defects appear asymmetric. This is due to uneven stresses prone to earlier compression damage. The asymmetric growth of the hole spacing has a greater weakening effect on the peak strength of limestone specimens. The larger the spacing of the asymmetric hole defects, the higher the degree of weakening of the peak strength of the specimens. The shape, spacing and asymmetry of the double hole defects in the limestone specimens all have the significant effect on dynamic compressive strength. The hole defects in the lower part of the limestone specimen have a significant effect on the propagation of the primary crack. This deflects the direction of initial tensile crack extension, resulting in the main mode of damage being a shear-tensile composite fracture. Among the damage modes of the limestone specimens, far-field tensile and shear cracks of types V and VI are more common. In addition, the cracking velocity considering the extension path fractal effect is 1.01−1.17 times of the apparent crack extension velocity. When the hole defects are asymmetrically distributed and widely spaced, the final number of cracks formed is smaller, the crack expansion velocity is reduced, and it is more favorable to suppress the rock chip flaking phenomenon on the rock surface.

Although the function of tRNAs in the translational process is well established, it remains controversial whether tRNA abundance is tightly associated with translational efficiency (TE) in mammals. Moreover, how critically the expression of tRNAs contributes to the establishment of tissue-specific proteomes in mammals has not been well addressed. Here, we measured both tRNA expression using demethylase-tRNA sequencing (DM-tRNA-seq) and TE of mRNAs using ribosome-tagging sequencing (RiboTag-seq) in the brain, heart, and testis of mice. Remarkable variation in the expression of tRNA isodecoders was observed among different tissues. When the statistical effect of isodecoder-grouping on reducing variations is considered through permutating the anticodons, we observed an expected reduction in the variation of anticodon expression across all samples, an unexpected smaller variation of anticodon usage bias, and an unexpected larger variation of tRNA isotype expression at amino acid level. Regardless of whether or not they share the same anticodons, the isodecoders encoding the same amino acids are co-expressed across different tissues. Based on the expression of tRNAs and the TE of mRNAs, we find that the tRNA adaptation index (tAI) and TE are significantly correlated in the same tissues but not between tissues; and tRNA expression and the amino acid composition of translating peptides are positively correlated in the same tissues but not between tissues. We therefore hypothesize that the tissue-specific expression of tRNAs might be due to post-transcriptional mechanisms. This study provides a resource for tRNA and translation studies, as well as novel insights into the dynamics of tRNAs and their roles in translational regulation.

The elastic modulus of rocks is a measure of the ability of rocks to resist elastic deformation. It is related to the size of rocks and can effectively measure the internal physical and mechanical strength of rocks. The development of joint fractures is the main reason for the size effect of rocks. Therefore, exploring the influence of joint roughness on the elastic modulus of rocks of different sizes is of great significance in mining rock mechanics. The article investigates the size effect of joint roughness on elastic modulus of rocks by establishing simulation schemes for 30 working conditions. By analyzing the stress-strain curves of rocks with different roughness and sizes, the deformation and failure patterns of rocks with different sizes were obtained. Research has found that the elastic modulus of rocks is in a power function relationship with joint roughness, while the elastic modulus of rocks is negatively exponentially related to rock size; The characteristic elastic modulus of rocks is in a power function relationship with joint roughness. The above relationships not only reveal the variation of rock elastic modulus with size, but also reveal the influence of joint roughness on elastic modulus, providing important basis for understanding the stability of mining rock engineering.

The compression deformation and particle breakage of gangue filling materials are significantly affected by different particle size gradations. To study the mechanical behavior of mixed size gangue backfilling materials in-depth, a physical compression experiment of mixed size gangue was carried out by designing a scheme based on Talbot's theory and fractal theory was used to quantify the breakage degree of mixed size gangue particles. Then, a discrete element numerical simulation was used to study the particle breakage mechanism of mixed size gangue in the compaction process. The results show that under the same vertical load, the settlement decreases monotonically with the increase in the Talbot's exponent (n), and the filling effect is significantly enhanced. The particle size distribution of mixed size gangue sample after compression has extremely good fractal characteristics. The fractal dimension has superior linear function regression relationship with n and crushing ratio. The fractal dimension decreases with increasing n. and the crushing ratio declines with increasing fractal dimension. Large-particle-size gangue is mainly broken at the initial stage of loading, while the crushing ratio of small-particle-size gangue gradually increases after the compaction stage. Large-particle-size gangue is the main bearing structure of the strong force chain, thus forming a strong skeletal structure. In the process of axial loading, cracks are mainly distributed near the “force chain skeleton”, and the contact forces around the skeleton are the first to be broken. This phenomenon causes the breakage of gangue particles, the rearrangement of particle positions and greater subsidence to fill the pores.

Taking Daliuta Coal Mine in Western Shendong mining area as the engineering background, this paper selected typical shallow buried high-intensity mining panel 52307 to establish the observation station for surface movement. Combined RTK technology and 3D laser scanning technology for real-time monitoring, based on key layer theory and CISPM comprehensive surface subsidence prediction model software, the characteristics of surface movement and deformation, surface movement angular parameters and surface cracks in high-intensity mining of shallow buried was studied. The results showed that with the advance of the panel from the set-up room, the surface subsidence was small at the set-up room position and then increased suddenly and rapidly. Simultaneously, the subsidence curve became steep sharply. When the maximum subsidence value was reached, the subsidence velocity tended to slow down. The surface movement deformation was mainly concentrated in the middle of the panel, while the subsidence deformation around the panel and the influence range of surface movement was small. The surface movement angular parameters were quite larger in the Daliuta coal mine area, while the bedrock movement angle and boundary angle reached 87.7 ° and 84.1 ° respectively. The surface cracks caused by mining were in an overall “C” shape, mainly distributed in the middle of the panel. Then, As the working face continued to advance, the ground fissures continue to slowly extend, develop, and gradually close from the set-up room to the tailgate side, eventually forming a continuous surrounding "funnel" shape. Ground fissures always lagged behind the working face position and the lag distance of surface cracks increases linearly with the mining speed. According to the analysis of surface subsidence law and surface cracks development, it was concluded that under the condition of high-intensity mining of shallow buried with thick coal seam, due to the high mining intensity of the working face, fast advancing speed, single key layer structure and low occurrence horizon, the roof activity was intense and easy to slide and lose stability. As a result, it was appeared resulting in rapid convergence around the surface movement basin, serious damage in the middle, and intensive development of ground fissures.

Coal will occupy the main position in China's energy structure for a long time, and the negative externalities of its exploitation have a serious impact on the ground surface and its appurtenances. With the proposal of the dual carbon strategy, the coal-based energy determines that green and safe coal mining should be the priority direction of China's energy development. Taking Xinyi coalmine, which is mined in unstable coal seams with large mining depth, as the research area, the surface response characteristic and subsidence law under the different mining degrees were clarified. Meanwhile, the damage mechanism of buildings was revealed, which was from no obvious damage to Grade Ⅳ under the extremely insufficient mining to subcritical mining. Based on the sustainable development and green production in coalmines, the overburden grout injection technique under buildings that does not affect the normal production was proposed, and its technical principle was described. A weighted grey relational analysis model was established, and obtained that the panel width was the main factor affecting the overburden failure height under subcritical mining. According to the definition of overburden failure degree proposed by the author, the feasibility of overburden grout injection technique under buildings was analyzed and the key parameters, such as slurry diffusion radius, borehole position and depth, grouting system and technology, were determined and successfully applied. The engineering application shows that the maximum surface subsidence after grouting is 253 mm, and the building damage is within the Grade I. Meanwhile, 5.82 Mt of coal resources under the buildings have been liberated, which realizes high quality coal mining, low environmental damage, green and low-carbon, and also provides a reference for the sustainable development of coal enterprises, especially for the exhausted coalmines that recover coal pillars.

The deformation and re-crushing characteristics of different lithological caving crushed gangues in mine goaf directly affect the overburden strata movement, which significantly affects the surface subsidence of mining goaf. The effect of particle size on the re-crushing characteristics of different lithological caving crushed gangues in mine goaf is investigated in this study based on an innovative compression–AE (acoustic emission) measuring method. The results showed the following: (1) The compression deformation was divided into three stages: rapid, slow, and stable compaction. With the increase in axial pressure, the large particle skeletons were destroyed, medium particles were displaced and slid, and small particles filled the pores. (2) For singular lithologies, stress was positively correlated with pressure, and porosity was negatively correlated with stress. The composite sample was between the singular gangue samples. (3) The fractal dimension of crushed gangue samples was exponentially related to the proportion of gangue in singular and combined lithologies. (4) The cumulative AE count and energy of the combined lithological gangue samples were between those of the singular samples. The research results provide a theoretical foundation for further research into the characteristics of the overlying strata, surface movement, and safety management of the goaf.

Abstract To address the increasing labor cost of resin tapping, more efficient methods for resin tapping need to be developed. This study aimed to evaluate the features of resinosis as affected by stimulant pastes in Pinus elliottii × P. caribaea, which is also one of the predominant resin-producing species hybrids in South China. The resin yields and resin compositions were assessed in 33 P. elliottii × P. caribaea F1 families, with the application of four kinds of chemical stimulants, potassium (K2SO4) paste, naphthalene acetic acid (NAA) paste, benzoic acid (BA) paste and 2-chloroethylphosphonic acid (CEPA) paste. Our results showed that all four pastes significantly increased the resin yield by at least 20% at each tapping, and 3- to fivefold increases were detected at the beginning of each year. The correlations between resin yield and growth at each tapping ranged from uncorrelated to moderately positively correlated, indicating that resin yield was mostly but not always determined by tree size. The concentration of each resin component did not change with the stimulant applications. In P. elliottii × P. caribaea, selecting a larger tree diameter at breast height and employing the chemical stimulants at the first several tapping rounds are efficient tapping procedures. Moreover, the K2SO4-based stimulant can be recommended considering its promoting effects on resin yield and the low cost of the chemicals required to produce it.

The contradiction between efficient coal mining and arable land capacity enhancement in the coal–grain production overlapping area has constrained grain output and threatened food security. In this study, DInSAR was used to extract the mining subsidence areas (SAs). Multiple red-edged vegetation indices were introduced to explore the growth differences between winter wheat in the SAs and Check Areas (CKs). A crop health index (SACHI) was proposed to comprehensively evaluate the health of winter wheat in SAs. The results showed that: (1) Compared with the CKs, the onset of over wintering season (OWS), start of growing season (SOS), and end of growing season (EOS) of winter wheat lagged behind in the SAs. (2) The winter wheat growths were slower in the SAs and their decline rates were faster than that in the CKs. (3) The SACHI could effectively synthesize the information contained in each component and was highly correlated with them. (4) Mining subsidence had a significant impact on the winter wheat health in the length of growing season (LOS), while the impact was weakened during the OWS. Based on the multi-vegetation indices and the SACHI, the impact of mining subsidence on the winter wheat health can be effectively diagnosed and estimated.

Abstract Background Microsatellite instability (MSI) accounts for about 15% of colorectal cancer and is associated with prognosis. Today, MSI is usually detected by polymerase chain reaction amplification of specific microsatellite markers. However, the instability is identified by comparing the length of microsatellite repeats in tumor and normal samples. In this work, we developed a qualitative transcriptional signature to individually predict MSI status for right-sided colon cancer (RCC) based on tumor samples. Results Using RCC samples, based on the relative expression orderings (REOs) of gene pairs, we extracted a signature consisting of 10 gene pairs (10-GPS) to predict MSI status for RCC through a feature selection process. A sample is predicted as MSI when the gene expression orderings of at least 7 gene pairs vote for MSI; otherwise the microsatellite stability (MSS). The classification performance reached the largest F-score in the training dataset. This signature was verified in four independent datasets of RCCs with the F-scores of 1, 0.9630, 0.9412 and 0.8798, respectively. Additionally, the hierarchical clustering analyses and molecular features also supported the correctness of the reclassifications of the MSI status by 10-GPS. Conclusions The qualitative transcriptional signature can be used to classify MSI status of RCC samples at the individualized level.

A part of colorectal cancer which is characterized by simultaneous numerous hypermethylation CpG islands sites is defined as CpG island methylator phenotype (CIMP) status. Stage II and III CIMP−positive (CIMP+) right-sided colon cancer (RCC) patients have a better prognosis than CIMP−negative (CIMP−) RCC treated with surgery alone. However, there is no gold standard available in defining CIMP status. In this work, we selected the gene pairs whose relative expression orderings (REOs) were associated with the CIMP status, to develop a qualitative transcriptional signature to individually predict CIMP status for stage II and III RCC. Based on the REOs of gene pairs, a signature composed of 19 gene pairs was developed to predict the CIMP status of RCC through a feature selection process. A sample is predicted as CIMP+ when the gene expression orderings of at least 12 gene pairs vote for CIMP+; otherwise the CIMP−. The difference of prognosis between the predicted CIMP+ and CIMP− groups was more significantly different than the original CIMP status groups. There were more differential methylation and expression characteristics between the two predicted groups. The hierarchical clustering analysis showed that the signature could perform better for predicting CIMP status of RCC than current methods. In conclusion, the qualitative transcriptional signature for classifying CIMP status at the individualized level can predict outcome and guide therapy for RCC patients.

The height of fractured zone (HFZ) at the high-intensity longwall mining panel plays a vital role in the safety analysis of coal mining under bodies of water. This paper described definitions of the high-intensity mining. The processes of overburden failure transfer (OFT) were analyzed, which were divided into the development stage and the termination stage. Through theoretical analysis, the limited suspension-distance and the limited overhanging distance were proposed to judge the damage of each stratum. Mechanical models of strata suspended integrity and overhanging stability were established. A theoretical method to predict the HFZ at the high-intensity longwall mining panel was put forward based on the processes of OFT. Taking a high-intensity longwall mining panel (No. 11915 panel) as an example, the theoretical method proposed, the engineering analogy and the empirical formulas in the Regulation were used to predict the HFZ. The results show that the theoretical result is consistent with the engineering analogies’ result and empirical formulas’ result. The rationality and reliability of the theoretical method proposed is verified. Keywords: High-intensity mining, Overburden failure, Height of fractured zone, Overlying strata movement

To ensure safety mining during shallow horizontal coal mining based on the monitoring data of the roof weighting of a typical mining engineering in China, the load distribution characteristics of the roof in the mining field were analysed, and the mechanical model of the pressure-arch in the surrounding rock was established. Then the evolution characteristics of the pressure-arch and elastic energy were revealed during shallow coal mining by theoretical and numerical analyses. Results show that the continuous pressure-arch can form when the horizontal stress exceeds the vertical stress, and the elastic energy of the roof is released by the mining unloading effect. The caved zone of the overlying strata is formed below the inner boundary of the pressure-arch. The elastic energy is accumulated in the pressure-arch and the energy becomes the highest at the front arch foot. The sliding of the caved zone along the shear zone in the mining field can induce the strong roof weighting. The concentrated stress and the released energy during each mining stage increase with the working face advancing, and the height of the shear zone also increases. This study can provide a theoretical reference for similar mining engineering.

It is important to study the mining technology under structures for raising the coal resources recovery ratio. Based on the geological and mining conditions, the top coal caving harmonic mining technique in thick coal seam beneath the earth dam was put forward and studied. The 5 factors such as the panel mining direction, panel size, panel location, panel mining sequence and panel advance velocity were taken into account in this technique. The dam movement and deformation were predicted after the thick coal seam mining and the effects of mining on the dam were studied. By setting up the surveying stations on the dam, the movement and deformation of the dam were observed during mining. By taking some protective measures on the dam, the top coal caving mining technique in thick coal seam beneath the earth dam was carried out successfully. The study demonstrates that harmonic mining in thick coal seam is feasible under the dam. The safety of the earth dam after mining was ensured and the coal resources recovery ratio was improved. Keywords: Earth dam, Thick coal seam, Top coal caving mining, Harmonic mining, Mining damages and protection

There are risks of water burst and sand inrush in the working face of the Northwest Mining Area in China. Based on the 22407 working face of Halagou coal mine, the evolution characteristics and mechanism of a two-zone failure mode of the overburden strata in shallow buried thick seam mining were thoroughly analysed using physical modelling, theoretical analysis, on-site observation, and other research methods. A method to calculate the overburden fissure width was also proposed. The analysis results indicated that the evolution of a two-zone failure mode of the overburden strata mainly includes four stages: gestation, formation, transformation, and stabilization. In the transformation stage, a fracture zone is transformed into a caving zone. The caving zone and fracture zone are separately transferred to the working face direction based on the structure type of key strata of voussoir beam and cantilever beam after the heights of the two zones stabilize, and the “two-belt” cracks are mainly composed of inclined and horizontal fissures. Based on this study, the mechanism of the two-zone failure mode of overburden strata development was analysed according to the mining height and overburden strata key layer structure. This paper serves as a guide for safe and green mining on shallow buried thick seams.

In China's northwest coal mining area, the excavation of shallow buried thick coal seams has caused serious damage to the phreatic water layer and induced deterioration of the ecological environment. Backfilling is a basic method of controlling the loss of groundwater and reducing surface subsidence. In order to reduce the porosity of the backfill material and control the compression ratio of the backfill body, the grain gradation of the local aeolian sand was studied based on the geological conditions of the shallow buried coal seam in the Yulin mining area, Shaanxi province. Subsequently, aeolian sand was selected as the backfilling aggregate, and tests were implemented. The optimum proportion and slurry concentration of the backfill material were then obtained. The engineering application shows that the strength and stability of the backfill body based on the close packing theory can satisfy the requirements of supporting the overlying strata, and the integrity of overburden strata is competent. The maximum accumulated surface subsidence was measured to be 38mm, indicating that the aeolian sand-based backfill material in shallow and thick underground coal seam mining is able to protect the eco-environment and control the geo-environmental hazards, which are critical for the sustainable development of the mining industry and economic growth.

The severe overburden failure induced by high-intensity mining is the essence of eco-environmental problems in Northwest China, and the degree of overburden failure is closely related to the location and failure of key strata (KS), which controls part of the strata in the overburden. In order to solve the problems of traditional KS based on mechanical parameters and numerical simulation methods that are time consuming, complex, expensive, and work intensive, it is necessary to find a simple and fast KS identification method. Based on the KS theory, which has been successfully applied in the field practice for nearly 30 years, and its current identification method by calculation or software, the magnetotelluric (MT) detection method was selected. According to the principle of MT detection method, the main influencing factors were analyzed. By summing up the relationship between the geological characteristics of the KS and its apparent resistivity (AR), the AR trends of ten kinds of lithology are given, and the identification mechanism of the MT detection method is revealed. Through the field measurement in Daliuta coalmine and the accuracy verification by the theory calculation, the KS obtained by the two methods are consistent. The results show that the MT detection method can be used to quickly identify the KS, and it is simple, convenient, and fast. It provides a reference for optimizing mining technology, mine pressure control, and mine precision.

In the ecologically fragile mining area of northwest China, high-intensity mining has seriously affected the aquifer and surface eco-environment. In order to better implement water-preserved mining in ecologically fragile areas, the aquifer failure characteristics should be first detected accurately; therefore, it is necessary to find a convenient and fast detection method. Based on the analysis of the basic principles and influencing factors of the magnetotelluric (MT) method, the feasibility of using the MT method to detect aquifer failure is verified by testing the mined area with MT detection and field borehole measurement. Subsequently, the failure characteristics of overburden and unconsolidated aquifers under high-intensity mining are studied by MT detection and physical simulation. By comparing the physical simulation with the field measurement from the aspects of the maximum surface subsidence, interval of periodic weighting and step cracks, the reliability of the height of the water flowing fracture zone and caving zone obtained from physical simulation is verified. The analysis from MT detection and physical simulation shows that the results of the two methods are in accord with each other, which further confirms that the MT method can be used to detect the failure of overburdened structures and aquifers. The penetrating fractures are the main channel for the downward seepage of water resources, which is caused by the “two-zone” of overburden model and located in the “dimple” shape in the apparent resistivity (AR) isogram. It can provide a reference and technical support for the corresponding new water-preserved mining technology and the construction of digital mines.

Mining-induced surface subsidence causes a series of environmental hazards and social problems, including farmland destruction, waterlogging and building damage in the subsidence area. To reduce mining damages, an innovative method of controlling the surface movement scope via artificial weak planes generated by hydraulic fracturing technology was proposed in this paper. Numerical models were built to analyze the influence of weak planes with different heights and dips on the overlying strata movement. The numerical simulation results showed that the weak planes structure cut off the development of the overlying strata displacement to the surface and affected the surface movement scope. When the weak planes’ dips were bigger than the angle of critical deformation, with the increase of the weak planes’ heights (0−120 m) the advance angle of influence changed from 53.61° to 59.15°, and the advance distance of influence changed from 173.31 m to 140.27 m which decreased by 30.04 m. In applications at Sihe coal mine in China, directional hydraulic fracturing technology was used in panel 5304 to form artificial weak planes in overlying strata. The measured surface subsidence and deformation value met the numerical simulation results and the mining-induced surface movement scope reduced. Moreover, no damage occurred to the surface buildings which were predicted to be in the affected area after extraction. This technology provided a new method to protect the surface structures from damages and had great benefits for the sustainable development of coal mines.

High voltage line towers in mining areas are sensitive to surface deformation caused by mining. Protective coal pillar design for high voltage towers is one of the commonly-used technical measures. Aiming to solve the coal mining safety problem under the Ultra High Voltage transmission line in Sihe Coal Mine of Shanxi Province, the angle and size of protective coal pillars with the vertical line method were analyzed in this paper. The effect of additional displacement caused by landslide or slippage mining in mountain areas and repeated mining was considered. Based on the principle of the vertical line method, the protective coal pillar range and size were calculated. The amount of coal deposited in coal pillars for high voltage line towers was compared and analyzed between the vertical line method and the linear structure method. The results showed that the angle of critical deformation decreased by 2~10° caused by slippage due to mining in a mountainous area, and the angle in the uphill direction of building decreased more than that in the downhill direction; when multi-seams were mined repeatedly, the angle of critical deformation in the lower seam coal mining was reduced by 5~10° compared with that of the upper seam. The protective coal pillar design with the vertical line method can protect the high voltage line towers more effectively, and the amount of protective coal pillars with the vertical line method was 5.8 million tons less, which avoided the waste of coal resources.