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An intersection of two roman glareatae roads and an underground stretch of a Roman aqueduct ( rivus subterraneus ) were found in the locality of Colle Oliva, during an emergency archaeological investigation (between 11/2018 and 3/2019). The aqueduct has been detected in several test trenches and some profiles have been obtained. These data shade some light about the Roman hydraulic technology and they show how the land morphology affected the shape and the path of the aqueduct.

For the study of the layout of the roadway in the coal pillar and floor strata co-mining working face at the Zhaogu No.2 mine, a mechanical model of the segmental coal pillar within the working face was established through theoretical calculations. The analysis considered the stress state of the coal pillar area under different collapse conditions in the goaf after upper strata mining. Additionally, FLAC 3D numerical simulation software was used to simulate the stress distribution in the roadway for different layout positions during strata mining, thereby clarifying the impact of working face mining on the side roadway of the segmental coal pillar. The results show that the collapse of the goaf after upper strata mining significantly affects the stress distribution in the coal pillar area. To ensure safety during mining, roadway excavation and working face recovery should be conducted after the upper strata have fully collapsed during strata mining. The co-mining working face roadway should be positioned beneath the original upper strata goaf, avoiding stress concentration areas in the coal pillar location. Ultimately, it is determined that the side roadway for the lower strata working face should be arranged with an offset of 10 m outward. Practical on-site experience has demonstrated that under this offset, there is minimal deformation of the surrounding rock in the coal pillar side roadway, meeting the safety production requirements of the working face.

Roadway deformation is a comprehensive response to changes in surrounding rock masses as well as the geological environment. Deformation patterns survey can help us to understand rock masses, especially soft swelling rock mass and guide roadway renovation. In this paper, an overall deformation analysis method for a largely deformed roadway in soft swelling rock mass has been proposed based on 3D mobile laser scanning. The application procedures of the proposed method mainly include point cloud data acquisition, data pre-processing, coordinate transformation, surface change detection and visualization. In the proposed method, the reference point cloud is created according to the roadway design to overcome the issue of the missing original roadway profile point cloud. By incorporating the K-nearest neighbor algorithm, a point-to-plane distance calculation algorithm is developed for the source and the reference point cloud data to detect roadway deformation. Taking the main haulage roadway in skarn rock mass at − 480 m level of Taiping Mine as an example, the deformation patterns of this roadway were analyzed using the proposed method. The results reveal that the roadway deformed seriously up to 1187 mm and the roadway deformation characterizes asymmetry and non-uniformity. The accuracy of the proposed method can meet engineering requirements by comparing the calculated and measured results. Aiming at the asymmetrical deformation patterns of this roadway, an asymmetrical support methodology has been suggested for the roadway renovation. The proposed deformation analysis method provides a reliable tool for largely deformed underground workings in soft swelling rock mass.HighlightsAn overall deformation analysis method based on 3D mobile laser scanning has been proposed for largely deformed roadway in soft swelling rock mass.In the proposed method, a surface change detection algorithm has been developed by incorporating the K-nearest neighbor algorithm for the source and the reference point clouds.Taking Anhui Taiping Mine as an engineering case, the deformation patterns of the roadway in skarn rock masses have been revealed to be distinct asymmetry and non-uniformity using the proposed method.

Squeezing failure is a common failure mechanism experienced in underground coal mine roadways due mainly to mining-induced stresses, which are much higher than the strength of rock mass surrounding an entry. In this study, numerical simulation was carried out to investigate the mechanisms of roadway squeezing using a novel UDEC Trigon approach. A numerical roadway model was created based on a case study at the Zhangcun coal mine in China. Coal extraction using the longwall mining method was simulated in the model with calculation of the mining-induced stresses. The process of roadway squeezing under severe mining-induced stresses was realistically captured in the model. Deformation phenomena observed in field, including roof sag, wall convexity and failed rock bolts are realistically produced in the UDEC Trigon model.

Coal pillar is a crucial element formed during underground coal mining, playing a significant role in ensuring coal mining operations are conducted safely. Historically, research on coal pillars has primarily focused on regular-shaped pillars, with limited attention given to special-shaped pillars. Therefore, this paper aims to investigate the special-shaped coal pillar formed after the excavation of the newly constructed 3307 headgate in Dayang Coal Mine, China. The primary object of this paper is to elucidate the mechanism behind the instability failure of special-shaped coal pillars and verify the influence of various geological conditions on their stability. To accomplish these goals, numerical simulation techniques were employed to analyze the stress distribution patterns and plastic zone failure characteristics of special-shaped coal pillar. The investigation revealed the presence of stress concentration phenomena within special-shaped coal pillar, where the stress peak values were directly correlated with the width of the pillar. Moreover, it was observed that as the width of coal pillar decreased, the stress curve gradually transitioned from a bimodal shape to a unimodal shape. Additionally, the ratio of the plastic zone within coal pillar increased as the width decreased, with pronounced tensile failures occurring at sharp corners. Building upon theoretical analysis and numerical simulation results, the interior of special-shaped coal pillar was classified into four distinct zones: damaged zone, progressive zone, stable zone, and special zone. Based on this zoning approach, a stability control technology was developed, employing a combination of \"pier pillar support + flexible formwork concrete + grouting reinforcement + high-strength cable and bolt + U-steel.\" Subsequently, an industrial experiment was conducted to validate the efficacy of this control technology. Field monitoring results demonstrated that the newly excavated roadway exhibited minimal deformation and damage, thereby satisfying the requirements for safe and efficient mine production over the anticipated service life.HighlightsThe failure characteristics and bearing mechanism of special-shaped coal pillars were analyzed, and a mechanical model was established, allowing exploration of the influence of different geological conditions on pillar stability.The stress evolution and plastic zone development characteristics of special-shaped coal pillar during the whole cycle were studied.A zoning criterion for special-shaped coal pillar was proposed, along with corresponding control measures, which were successfully applied to the site, effectively controlled the deformation of roadway.

Support technology faces challenges in view of the large deformation of surrounding rock in three-soft coal roadways under high horizontal stress in Zijin Coal Mine, China. Geostress near the tested working face of the mine was measured and its distribution law was analyzed through theoretical analysis, numerical simulation analysis, and field measurement. The original supporting scheme of the three-soft coal roadway on the tested working face was analyzed to discover the deformation and failure mechanism of the surrounding rock of the original supporting roadway and the control measures. An optimized support scheme of H-G (hollow grouting) anchor cables, high strength bolts, W-shaped steel belts, metal meshes, and sprayed concretes was proposed for field applications. Based on the roadway in the tested 3201 working face at Zijin Coal Mine, the technical parameters for optimizing the combined support of the roadway were determined. The following results were be obtained through field measurement. The roadway was kept intact after excavation and the optimized support scheme was adopted in the three-soft coal roadway. No obvious deformation in appearance existed in the roof, floor, and roadway coal sides. Compared with the original support scheme, the stability of the roadways was improved visibly. The displacement of the roadway roof decreased from 100 to 30 mm, and that of the roadway coal walls decreased from more than 100 mm to less than 50 mm. This work verifies the effectiveness of a combined support scheme of H-G anchor cables, high strength bolts, W-shaped steel belts, metal meshes, and sprayed concretes to control deformations of surrounding rock in three-soft coal roadways. The new support scheme has good social and economic benefits and can be used as a reference for other roadway supports under similar conditions.

Backfill coal mining technology has drawn widespread attention due to its benefits of “controlling surface deformation and subsidence, reducing mining-induced disturbance in the stope, and recycling solid mine wastes”. However, the backfill coal mining technology is still progressing slowly in China. The geological environment of China’s mining areas is complex and highly diversified, and backfill coal mining is expected to fulfill different goals in a wide range of engineering scenarios. These facts explain the poor reproducibility of backfill coal mining projects. This study reviews the existing backfill coal mining systems in China. Based on findings from a survey of engineering cases, we summarize five types of new backfill coal mining methods classified by deployment style; namely, borehole grouting backfill, roadway backfill, borehole–roadway backfill, in situ backfill, and roadway-in-situ backfill. A total of 15 backfill coal mining methods falling into the above five categories are described. An engineering design workflow for backfill coal mining consisting of five steps is proposed; namely, identifying the targets of backfill, analyzing the feasibility of deploying the backfill system, comparing the engineering quantities of different engineering schemes, estimating the economic efficiency of backfill, and backfill performance tracking and monitoring. Real cases of backfill engineering design are analyzed to inform the fast and reasonable design of backfill strategy for specific working faces in certain coal mines.

Roadway instability has always been a major concern in deep underground coal mines where the surrounding rock strata and coal seams are weak and the in situ stresses are high. Under the high overburden and tectonic stresses, roadways could collapse or experience excessive deformation, which not only endangers mining personnel but could also reduce the functionality of the roadway and halt production. This paper describes a case study on the stability of roadways in an underground coal mine in Shanxi Province, China. The mine was using a longwall method to extract coal at a depth of approximately 350 m. Both the coal seam and surrounding rock strata were extremely weak and vulnerable to weathering. Large roadway deformation and severe roadway instabilities had been experienced in the past, hence, an investigation of the roadway failure mechanism and new support designs were needed. This study started with an in situ stress measurement programme to determine the stress orientation and magnitude in the mine. It was found that the major horizontal stress was more than twice the vertical stress in the East–West direction, perpendicular to the gateroads of the longwall panel. The high horizontal stresses and low strength of coal and surrounding rock strata were the main causes of roadway instabilities. Detailed numerical modeling was conducted to evaluate the roadway stability and deformation under different roof support scenarios. Based on the modeling results, a new roadway support design was proposed, which included an optimal cable/bolt arrangement, full length grouting, and high pre-tensioning of bolts and cables. It was expected the new design could reduce the roadway deformation by 50 %. A field experiment using the new support design was carried out by the mine in a 100 m long roadway section. Detailed extensometry and stress monitorings were conducted in the experimental roadway section as well as sections using the old support design. The experimental section produced a much better roadway profile than the previous roadway sections. The monitoring data indicated that the roadway deformation in the experimental section was at least 40–50 % less than the previous sections. This case study demonstrated that through careful investigation and optimal support design, roadway stability in soft rock conditions can be significantly improved.

Rocks are a natural material with strong heterogeneity, and the heterogeneity affects the behavior and failure patterns of rocks and rock masses. Therefore, the factor of rock heterogeneity should not be neglected in cases of highly heterogeneous rock masses. In this study, the effect of heterogeneity on the rock mass stability in an underground coal mine roadway is investigated by introducing a stability analysis method that considers rock heterogeneity. The stability analysis method is combined with field investigation, laboratory testing, and numerical simulation. The rock mass heterogeneity is considered in the light of equivalent material properties, which are the heterogeneous rock mass properties weakened by heterogeneously distributed fractures. A Weibull distribution model is implemented into FLAC3D to characterize the rock mass heterogeneity. Sensitivity analyses regarding the rock mass properties and the mesh dependency are conducted to understand their effect on roadway deformation. A parametric study is performed to investigate the effect of the homogeneity index and other parameters that describe the rock mass fracturing intensity. The results show that the degree of rock mass heterogeneity has a significant effect on the roof deformation, failure extent, and other input parameters that describe the rock mass heterogeneity. The simulation results that are in good agreement with heterogeneity parameter data are estimated in the field. Thus, this method can be used as a back-analysis technique to obtain the homogeneity index and other input parameters through comparison to field deformation data, and can be applied to other engineering cases involving highly heterogeneous rock.

Fault structures near underground coal mine return roadways frequently influence the deformation of surrounding rock, thereby constraining roadway stability. However, when the roof deformation is not clear in the case of a roadway through a normal fault, it will directly affect the establishment of a reasonable control program for the roof. Based on elastic-plasticity theory, this paper proposes a method for calculating the maximum deformation position of the roof plate in a roadway through a normal fault. This method accurately determines the maximum deformation position while considering the variation in widths between the upper and lower roof plates. Numerical simulations revealed the dual characteristics of asymmetric deformation in the roof plate and the asymmetric morphology of the plastic zone during the mining period. Furthermore, it delineated the significant impact of the width of the roof plate of the lower disc on roof deformation. A statistical analysis was conducted on the standard deviation (S) and coefficient of variation (CV) of both the theoretical and numerical simulation results, as well as the error rate between them. The analysis responded well to the reliability of the study results. The proposed reinforcement support program effectively guided the stability control of the roof plate in the roadway through the normal fault at the site. The research findings provide valuable insights for predicting and controlling roof deformation in roadways and tunnels under similar engineering conditions.HighlightsA theoretical calculation method of the maximum deformation location of the roof plate of the roadway through a normal fault is proposed.The asymmetric deformation characteristic of the roof plate of the roadway through the normal fault is revealed.Significant sensitivities of the surface deformation of the roof plate and the area of the plastic zone to the width of the roof plate of the lower disk are obtained.The feasibility of the theoretical predictive analysis of the location of maximum roof deformation in a roadway through a normal fault is determined.