Hard Bed Research Articles

An integrated study on the geochemical, geophysical and geomechanical characteristics of the organic deposits (Coal and CBM) of eastern Sohagpur coalfield, India

Coal mining, especially the underground mines are often encountered with several types of geological constraints, where massive-hard roof and trapped gas are the most serious threats leading to catastrophic (fatal) effects in form of roof falls, mine explosion and gas contamination. Thus, for enhancing the safety of underground coal mines, identification of aforesaid constraints during detailed exploration is very essential. The minable seams of Sohagpur Coalfield are often associated with rich Coal Bed Methane (CBM) content, which enhances their economical importance, but the gas content along with the presence of stable sandstone roof parallely induces challenges during their extraction. CBM also acts as an environmental hazard having twenty-one times more greenhouse effect than carbon dioxide (CO2). Therefore, the present paper attempts to investigate the depositional environment of the high-quality methane-rich sub-bituminous reserves of eastern Sohagpur Coalfield through integration of geochemical, geophysical and geomechanical analysis of the drilled boreholes along with their respective gas content. The results showed that the six major Barakar coal seams possessed nearly consistent distribution in terms of reserve distribution and chemical properties. These seams consisted of good quality reserves (Grade: G5-G8) with high heat values and organic content, and had less impurity content. These coal seams are overlain by stable roof having lower cavablity in form of thick hard medium-grained sandstone beds with moderate elasticity and strength. The seam structures showed a stable profile without any abrupt discontinuity except Bahmni-Chilpa fault in southern part of block. Some of the higher rank coal seams also contained potential CBM content. Statistical analysis was also carried out for understanding the distribution of reserve properties and monitored their interdependence using suitable fitting tools. Thus, the present study helped in summarizing different aspects related to reserve quality, roof properties and gas content for understanding the geology and working environment of coal reserves of less explored but economically important Central Indian coalfields.

Regional subglacial quarrying and abrasion below hard‐bedded palaeo‐ice streams crossing the Shield–Palaeozoic boundary of central Canada: the importance of substrate control

Three‐dimensional surface visualization models derived from high‐resolution LiDAR data provide new information about the type and scale of erosional processes below Late Wisconsin palaeo‐ice streams traversing the boundary between Canadian Shield crystalline rocks with offlapping Palaeozoic limestones in central Ontario. The hard bed is directly analogous to that found below ice streams in East Antarctica and East Greenland and provides insight into the effects of abrupt changes in substrate type on subglacial processes. Erosion of hard crystalline Canadian Shield rock was largely ineffectual consisting of areal abrasion of rounded whalebacks and local lee side plucking. In contrast, fast flow over the strike of gently dipping well‐bedded and jointed Palaeozoic limestones cut large flow‐parallel grooves and ridges akin to mega‐scale glacial lineations reflecting intense abrasion below narrow streams of subglacial debris dominated by hard crystalline Shield clasts (erodents). Regionally extensive plucking of structurally weak, well‐jointed and bedded limestone produced large volumes of rubbly carbonate debris leaving a 25‐km‐wide belt of uncontrolled hummocky rubble terrain (long known as the Dummer Moraine in Southern Ontario) some 350 km long and locally as much as 10 m thick. Subglacial plucking and abrasion under fast flowing ice were highly effective in stripping limestone cover rocks from Precambrian basement, and over many glacial cycles, may have played a role in the location and excavation of numerous large and deep lake basins around the Shield–Palaeozoic boundary zone in North America.

Modified Vecchietti vaginoplasty using self-made single-port laparoscopy in Mayer-Rokitansky-Küster-Hauser syndrome

To introduce the minimally invasive Vecchietti procedure based on single-port laparoscopy with self-made surgical instruments for the surgical management of Mayer-Rokitansky-Küster-Hauser syndrome (MRKH). Surgical video article. The approval of the Institutional Review Board and written consent from the patient were obtained. University hospital. A 22-year-old woman presented with primary amenorrhea and inability to participate in penetrative sexual intercourse. A gynecological examination revealed a phenotypically normal vulva and absence of the vagina. A normal 46,XX karyotype was expressed. Magnetic resonance imaging and ultrasonic imaging of the abdomen and pelvis indicated that the ovaries were normal in size and there was vaginal agenesis with rudimentary uterus. No other congenital malformations were present. The modified Vecchietti procedure involved a transvaginal operation and laparoscopic surgery. The epidural catheter was stretched and made into two wires that were tucked into the core of the Veress needle and then folded into four strings for perineal puncture. A transverse incision of about 3 cm was made in the center of the navel, layer by layer into the abdomen, and placed in a self-made single port (made of a small wound protector and an 8-inch glove), introducing the laparoscope. Under laparoscopic surveillance, the Veress needle was inserted through the vesicorectal space guided by the index finger, which was placed in the rectum. The epidural catheter was pumped from the core into the abdominal cavity under laparoscopy. Subsequently, cystoscopy was performed to ensure that no bladder perforation occurred during the needle insertion. The ball-shaped acrylic device and the two rubber stoppers were attached to the epidural catheter of the vulva. An epidural puncture needle with wire perforated the peritoneum through McBurney's point and the opposite McBurney's point, pulling the epidural catheter out of the abdominal cavity. The epidural catheter was curled around the gauze rolls until the ball-shaped device could be accommodated into the newly created cavity at a sufficient depth. After the surgery, the top of neovagina was lifted about 1 cm every day by tightening gauze rolls to increase the traction, until a neovagina 9 cm long was achieved. The clinical and anatomical data such as the operative time, intraoperative bleeding, duration of hospitalization, and measurement of the final length of the newly created canal 30 days after surgery and 3 months after surgery. The operative time was 30 minutes, and the intraoperative blood loss was 10 mL. The duration of hospitalization was 10 days. Before discharge, the vaginal depth was 9 cm at 5 days after the surgery, and the self-made traction system was removed. A plastic mold was then inserted using povidone-iodine. The vaginal dilator had to be worn day and night. The patient was advised to sit at the corner of a hard bed or chair from time to time to enhance the dilated effect of the vaginal mold. Three months after the surgery, it could be worn each night until regular sexual intercourse was initiated. The canal length 30 days and 3 months after the surgery was nearly 9 cm. The modified Vecchietti vaginoplasty is a simple, safe, cost-effective, and minimally invasive procedure, offering an anatomic and functional neovagina for MRKH patients.

From Hard Bed to Luxury Home: The Metamorphosis of HM Prison Pentridge

ABSTRACT Given all the uncomfortableness, fears, shame, and troubles associated with memories of Australian carceral history, it is surprising that Australians are interested in reusing sites of decommissioned prisons at all. The uncomfortable past juxtaposes basic ideas of preservation, not to mention the further transformation of old gaols to places for comfortable residences and shops. Her Majesty’s Prison Pentridge is used here as a case study, where the exact site of a century-and-a-half of notoriously brutal incarceration and source of uncomfortableness to the local community was transformed to residential and mixed-use developments. Perhaps due to those memories slipping away, or probably due to pragmatic economic opportunities allowed by urban consolidation policies, such acute transformation became possible. This paper joins an unsettled debate surrounding the phenomena of converting old prisons to contemporary buildings and shops inhabited by non-prisoners using Pentridge as a recent example.

Study on the Effect of Canceling Hard Bed on Patients after Renal Needle Biopsy

Objective: To investigate the effect of hard bed on postoperative complications and comfort level of patients after renal puncture biopsy. Methods: A total of 115 patients who underwent renal needle biopsy in the Department of Nephrology of The First Affiliated Hospital of Jinan University from May 2020 to February 2021 were selected, and 57 patients who received hard bed nursing after renal needle biopsy were set as the control group, the others were selected as the observation group. The incidence of postoperative bleeding at the puncture mouth, gross hematuria and dysuria, as well as the postoperative comfort level of 6 h and 18 h were compared between the two groups. Results: There was no significant difference in the incidence of postoperative bleeding, gross hematuria and dysuria between the two groups (P > 0.05), but the comfort scores at 6 h and 18 h in the observation group were higher than those in the control group (P < 0.05). Conclusion: There is no significant difference in the incidence of postoperative complications, such as bleeding at the puncture mouth, gross hematuria and dysuria, among patients with renal needle biopsy, whether to use hard bed nursing or not. Eliminate hard bed nursing can improve the comfort level of patients, reduce the occurrence of pressure ulcers, and relieve the negative psychological emotions of patients.

Low back pain and methods of coping with low back pain in nurses.

This research was conducted to determine low back pain in nurses and their methods of coping with low back pain. This descriptive, cross-sectional study was performed with 356 nurses in three university hospitals in the province of Istanbul in April-August 2016. Percentage calculations and Chi-square tests were used in statistical analyses. The mean age of the nurses in the study was 28.70±5.92, 25.3% were working in intensive care, 46.6% worked 41-48 h a week, and 55.6% stood for 5-8 h within a 24 h period. Low back pain was moderate in 75.8% of participants, and low back pains sometimes affected work efficiency in 43.3% (n=154). In terms of coping, the great majority of participants did not visit a physician, but used analgesics, avoided wearing high-heeled shoes, and slept in hard beds. Statistical significance (p<0.05) was observed between participants' age groups, the unit where they worked, type of duty, the amount of time spent standing, and the amount of time standing in the same position and low back pain. Based on the results obtained, nurses experienced a moderate level of low back pain, and we think that experiencing low back pain is a continuous risk for nurses because of their lengthy hours of work and time spent standing, and that their working hours should, therefore, be adjusted and that correct body mechanics should be included during in-service training.

Site Effect Estimation Using Microtremor Measurements at New Luxor City Proposed Site, South Egypt*

The present study aims mainly at investigating the site effect at the new Luxor city, Egypt, using microtremor measurements. Accordingly, 41 ambient noise recordings were implemented covering the investigated area in a reasonable manner with spacing nearly 1 km between each measurement station. The data were analyzed using Nakamura’s technique. The results show that; the investigated area exhibits low fundamental frequency values ranging between 0.28 - 0.47 Hz and its corresponding amplification factor values vary between 2.3 and 6.8. Consequently, the studied site is characterized by the presence of thick soft sediments overlying a hard bed rock. The seismic vulnerability index (Kg) was estimated, relying on the estimated fundamental frequency (F0) and amplification factor (A0), through the range between 11 and 95 across the mapped area. The obtained Kg values were noticed to be compatible with amplification level results. The central part of the investigated area reflects the higher Kg and A0 values.

Statistical analysis of geological factors controlling bed-bounded fracture density in heterolithic shale reservoirs: The example of the Woodford Shale Formation (Oklahoma, USA)

The geological controlling factors of natural fracture distribution and density in the Woodford Shale Formation are quantitatively investigated in this study. The Upper Woodford Shale member in southern Oklahoma, is exceptionally brittle due to the abundance of recrystallized radiolaria chert beds that alternate with siliceous shale beds. Bed-bounded compressional fractures are well developed in the structural-active region. Two areas were characterized and compared to represent low and high confining pressure conditions respectively. A statistical analysis workflow consisting of Principal Component Analysis (PCA) and Partial Least Square Regression (PLS) was proposed to quantify the controlling factors' relationship and their Variable Importance in Projection (VIP) which reveals the contribution of each controlling factor to the fracture density. The result indicated that natural fractures' occurrence in shale reservoirs are impacted by three controlling factors: rock hardness, hard bed ratio (thickness percentage of hard beds within a stratigraphic unit interval) and bed frequency (number of beds within a unit interval). The contributions from these individual controlling factors are different under different reservoir conditions. Bed frequency (layering anisotropy) is the dominant controlling factor that contributes on average three times more than the hard bed ratio and hardness to fracture density. Hardness's contribution to fracture density in the subsurface scenario is lower by 22% than the surface scenario due to the increase in confining pressure. The analytical results highlight the importance of the layering effect on fracture density which has often been overlooked in geomechanical modeling workflow. A new concept of Fracture Density Index (FDI) is defined and can be further applied to predict fracture density in other unconventional reservoirs.

Differentiation of subglacial conditions on soft and hard bed settings and implications for ice sheet dynamics: a case study from north-central Poland

We reconstruct patterns of subglacial processes on a hard bedrock and a soft bed under the southern sector of Scandinavian Ice Sheet (SIS) occurring in the basal till of the Late Saalian Glaciation at the Wapienno, Barcin and Młodocin sites (north-central Poland). Based on detailed sedimentological studies, two phases of SIS transgression were recognised. In the initial phase of the transgression, the SIS advanced onto a frozen substrate (continuous permafrost). The low permeability of the substratum led to a high subglacial water pressure (SWP) and increased basal sliding. The local increase of SWP led to the development of different types of structures and sediments. On a hard bedrock, with low SWP, abrasion predominated and linear structures were developing, while in the case of high SWP, the ice was decoupled from the hard substrate, pressurised liquefied sediment flowed, and structures of the p-form and s-form type developed. On a soft bed, the ice-bed contact was of a mosaic type and the ice movement had an ice-stream character. The ice-stream developed towards the east in the marginal zone of the SIS and used a W-E oriented valley filled by the Wapienno Formation fluvial complex. During a later phase, the ice movement was slower and did not have a stream character. Its direction changed to SE. The deposition of the main part of the diamicton occurred mainly as a result of the lodgement process.

From hard bed to luxury home: impacts of reusing HM Prison Pentridge on property values

This paper uses statistical analyses to understand the effect of proximity of old prisons on property prices. The study employed semilog hedonic regression models: a quantitative research method applied to assess the impact of proximity to heritage gaols on property prices for a case study of HM Prison Pentridge in the time range between 2015 and 2019. Results demonstrated that the former Pentridge has a variable effect on properties lying in and around its current heritage borders. Pentridge shows a diminution effect on prices of residential properties on its land currently being developed to a mixed-use precinct, as well as its intimate surrounding residences. Inversely, Pentridge shows a positive price effect on properties lying at distances between 400 m and the maximum study range of 1400 m in the case of ‘houses’ and between 600 m and the range of 1000 m in the case of ‘units.’ Findings of this research suggest that prices of properties with direct visual access to Pentridge’s structures are negatively affected. Results also suggest that Pentridge’s current redevelopment project may have contributed positively to property prices lying outside the direct visibility zone. To be able to further validate these interpretations, similar research may consider other variables influencing property valuation, such as direct visibility of the gaol as well as interviews that assess the ‘attractability’ of Pentridge’s redevelopment. Future studies may examine the rate of change in property price along time for each distance band from the gaol borders. Future research may also consider duplicating the methodology to assess the comfortability towards gaols converted to museums, as well as gaols that are still in operation. The originality of this research emerges from the distinct lack of quantitative evidence in the current literature. Most research has investigated uncomfortable heritage focusing on qualitative assessments of memory, stigma, commemoration, and shame, with limited scholarly attention paid towards property depreciation effects as a result of Australia’s prison history, nor increasing effects due to gaols’ reuse and redevelopment. Decision-makers and stakeholders of equivalent dark heritage reuse projects will find this research useful in understanding potential impacts on surrounding property prices. Property valuers and real estate companies operating in Coburg—a suburb of Melbourne, Australia—may use the related tables and figures in guiding their business for the coming years.

Slipping on till

Ice Sheets How do glaciers flow over the ground underlying them? We know that friction, ice stream velocity, and water pressure at the ice bed all matter, but we still do not know how to represent the process over both hard beds (which are solid rock) and soft ones (composed of unconsolidated erosion products called till). Zoet and Iverson present experimental results describing how glacial ice moves over watersaturated till (see the Perspective by Minchew and Joughin). These observations should help to solve the long-standing problem of constructing a generalized slip law that combines the processes of hard-bedded sliding and bed deformation. Science , this issue p. [76][1]; see also p. [29][2] [1]: /lookup/doi/10.1126/science.aaz1183 [2]: /lookup/doi/10.1126/science.abb3566

Spatial epidemiological patterns suggest mechanisms of land-sea transmission for Sarcocystis neurona in a coastal marine mammal

Sarcocystis neurona was recognised as an important cause of mortality in southern sea otters (Enhydra lutris nereis) after an outbreak in April 2004 and has since been detected in many marine mammal species in the Northeast Pacific Ocean. Risk of S. neurona exposure in sea otters is associated with consumption of clams and soft-sediment prey and is temporally associated with runoff events. We examined the spatial distribution of S. neurona exposure risk based on serum antibody testing and assessed risk factors for exposure in animals from California, Washington, British Columbia and Alaska. Significant spatial clustering of seropositive animals was observed in California and Washington, compared with British Columbia and Alaska. Adult males were at greatest risk for exposure to S. neurona, and there were strong associations with terrestrial features (wetlands, cropland, high human housing-unit density). In California, habitats containing soft sediment exhibited greater risk than hard substrate or kelp beds. Consuming a diet rich in clams was also associated with increased exposure risk. These findings suggest a transmission pathway analogous to that described for Toxoplasma gondii, with infectious stages traveling in freshwater runoff and being concentrated in particular locations by marine habitat features, ocean physical processes, and invertebrate bioconcentration.

Effect of particle size distribution on the packing of powder beds: A critical discussion relevant to additive manufacturing

Several additive manufacturing (AM) methods use powder feed materials. Selective laser sintering is an example of a versatile AM method, using feed material in powder form, capable of producing polymer and metallic parts. In the variations of this technique, a laser spot or an electron beam is used to locally sinter or melt a packed powder bed. After the completion of sintering on each layer, further powder is added on top of the existing bed so that the next layer may be joined. A major challenge in this method is controlling the porosity of the powder bed so that the final part has uniform and maximum density. Uniformity in the packing of bed from one layer to the other is important for optimizing the processing parameters. This review is focused on considering the packing characteristics of polydisperse hard particle beds and the determination of the expected density achievable for a given particle size and shape distribution. Models are presented for discrete mixtures as well as continuous distributions. The effect of the initial configuration of a particle bed on its ability to form a highly dense packing is also discussed. Blending of different particle sizes and shapes can be used to substantially increase the packing density, but can also lead to separation or segregation of the bed. Through appropriate control of the particle shape and use of wide distributions, packing densities close to 100 % can theoretically be achieved, but practicality and various effects that appear at small size scales prevent from achieving such high packing densities. Recent advancements have reduced the dependence of AM part quality on the density of the packed particle bed but the packing is still important for considerations such as thermal conductivity of the bed and absorption of laser power in the bed. Improved knowledge of packed bed characteristics can be helpful in developing AM methods for novel material systems.

Debris-bed friction during glacier sliding with ice–bed separation

AbstractTheory and experiments indicate that ice–bed separation during glacier slip over 2-D hard beds causes basal shear stress to reach a maximum at a particular slip velocity and decrease at higher velocities. We use the sliding theory of Lliboutry (1968) to explore how friction between debris particles in sliding ice and a rock bed affects this relationship between shear stress and slip velocity. Particle–bed contact forces and associated debris friction increase with increasing slip velocity, owing to increased rates of ice convergence with up-glacier facing surfaces. However, debris friction on diminished areas of the bed counteracts this effect as cavities grow. Thus, friction from debris alone increases only slightly with slip velocity, and for sediment particles larger than ~60 mm in diameter, debris friction peaks and decreases with increasing slip velocity. The effect on the sliding relationship is to steepen its rising limb and shift its shear stress peak to a slightly higher velocity. These results, which exclude the effect of debris friction on cavity size and debris concentrations above ~15%, indicate that the effect of debris in ice is to increase basal shear stress but not significantly change the form of the sliding relationship.

Subglacial roughness of the Greenland Ice Sheet: relationship with contemporary ice velocity and geology

Abstract. The subglacial environment of the Greenland Ice Sheet (GrIS) is poorly constrained both in its bulk properties, for example geology, the presence of sediment, and the presence of water, and interfacial conditions, such as roughness and bed rheology. There is, therefore, limited understanding of how spatially heterogeneous subglacial properties relate to ice-sheet motion. Here, via analysis of 2 decades of radio-echo sounding data, we present a new systematic analysis of subglacial roughness beneath the GrIS. We use two independent methods to quantify subglacial roughness: first, the variability in along-track topography – enabling an assessment of roughness anisotropy from pairs of orthogonal transects aligned perpendicular and parallel to ice flow and, second, from bed-echo scattering – enabling assessment of fine-scale bed characteristics. We establish the spatial distribution of subglacial roughness and quantify its relationship with ice flow speed and direction. Overall, the beds of fast-flowing regions are observed to be rougher than the slow-flowing interior. Topographic roughness exhibits an exponential scaling relationship with ice surface velocity parallel, but not perpendicular, to flow direction in fast-flowing regions, and the degree of anisotropy is correlated with ice surface speed. In many slow-flowing regions both roughness methods indicate spatially coherent regions of smooth beds, which, through combination with analyses of underlying geology, we conclude is likely due to the presence of a hard flat bed. Consequently, the study provides scope for a spatially variable hard- or soft-bed boundary constraint for ice-sheet models.

Linking bedrock discontinuities to glacial quarrying

AbstractQuarrying and abrasion are the two principal processes responsible for glacial erosion of bedrock. The morphologies of glacier hard beds depend on the relative effectiveness of these two processes, as abrasion tends to smooth bedrock surfaces and quarrying tends to roughen them. Here we analyze concentrations of bedrock discontinuities in the Tsanfleuron forefield, Switzerland, to help determine the geologic conditions that favor glacial quarrying over abrasion. Aerial discontinuity concentrations are measured from scaled drone-based photos where fractures and bedding planes in the bedrock are manually mapped. A Tukey honest significant difference test indicates that aerial concentration of bed-normal bedrock discontinuities is not significantly different between quarried and non-quarried areas of the forefield. Thus, an alternative explanation is needed to account for the spatial variability of quarried areas. To investigate the role that bed-parallel discontinuities might play in quarrying, we use a finite element model to simulate bed-normal fracture propagation within a stepped bed with different step heights. Results indicate that higher steps (larger spacing of bed-parallel discontinuities) propagate bed-normal fractures more readily than smaller steps. Thus, the spacing of bed-parallel discontinuities could exert strong control on quarrying by determining the rate that blocks can be loosened from the host rock.

Sliding dominates slow-flowing margin regions, Greenland Ice Sheet.

On the Greenland Ice Sheet (GrIS), ice flow due to deformation and sliding across the bed delivers ice to lower-elevation marginal regions where it can melt. We measured the two mechanisms of motion using a three-dimensional array of 212 tilt sensors installed within a network of boreholes drilled to the bed in the ablation zone of GrIS. Unexpectedly, sliding completely dominates ice motion all winter, despite a hard bedrock substrate and no concurrent surface meltwater forcing. Modeling constrained by detailed tilt observations made along the basal interface suggests that the high sliding is due to a slippery bed, where sparsely spaced bedrock bumps provide the limited resistance to sliding. The conditions at the site are characterized as typical of ice sheet margins; thus, most ice flow near the margins of GrIS is mainly from sliding, and marginal ice fluxes are near their theoretical maximum for observed surface speeds.

An improved 1-D crustal velocity model for the Central Alborz (Iran) using Particle Swarm Optimization algorithm

Summary We present an improved 1-D velocity model of the crust in the Central Alborz region using one of the powerful methods in global optimization techniques named Fuzzy Self-Tuning Particle Swarm Optimization (hereafter called FST-PSO). The FST-PSO generates random particles (velocity models) in a pre-defined solution space in which after number of iterations they lead to a model that yields best fits to the data. The ability of using any error statistics equally leads the algorithm to be independent of the velocity model form. As the PSO family members use only random processes to generate new models, they are inherently stable and avoid all numerical problems encountered in deterministic methods due to matrix inversion. Taking advantage of fuzzy logics implemented in FST-PSO, no parameters are needed to be adjusted including social, cognitive and inertia for running the program and can be used “out-of-the-box”. The proficiency of this method first is checked on both synthetic and real datasets. Then it is applied on a unique large amount of local earthquakes to calculated 1-D velocity model of the central Alborz, Iran. Relocation of events using our new velocity model and station corrections results to considerable reduction in RMS, horizontal and depth errors which obviously lead to a more precise events catalog. The spatial distribution of station corrections correlates well geological features. The positive delays in this area are consistent with Pliocene to Quaternary sedimentary cover spread in different parts of the study area, while the negative delays indicating on high velocity anomaly beneath the station are observed on hard Igneous rocks mainly around the Mosha fault. Positive delays of few stations located on hard bed rocks can be related to the shallow magma chamber of the Damavand volcano. Updating the seismicity map using this catalog, reveals a good correlation between existing active faults trends like Mosha, Khazar, North Alborz, Garmsar, and Taleghan and well-located earthquakes.

Environmentally sustainable mining: a case study on surface subsidence control of grouting into overburden

This paper presents an investigation on the effect of grouting into multi-bed-separation to control mining-induced surface subsidence. In the overburden without obvious thick-and-hard strata for generating large-scale bed separation, overburden grouting is carried out by increasing the number of boreholes and grouting strata. The scale model test, numerical simulation, and field measurements are used to study distribution and process of bed separation and to compare the overburden failure with surface subsidence due to pre- and post-overburden grouting, with a case study of the Qi’nan Coal Mine, Anhui Province, China. The scale model test and numerical simulation results of the overburden grouting process are in close agreement with those obtained from the field measurements. Filling masses with different diffusion radii are commonly formed in the different bed separation, which are overlaid to control the surface subsidence. It is proven that overburden grouting can successfully mitigate overburden failure and subsidence without obvious hard strata and bed separations. This provides an effective and cost-efficient approach for addressing the surface subsidence and overburden deformation problems due to mining.

Quantifying bed roughness beneath contemporary and palaeo-ice streams

ABSTRACTBed roughness is an important control on ice-stream location and dynamics. The majority of previous bed roughness studies have been based on data derived from radio-echo sounding (RES) transects across Antarctica and Greenland. However, the wide spacing of RES transects means that the links between roughness and flow are poorly constrained. Here, we use Digital Terrain Model/bathymetry data from a well-preserved palaeo-ice stream to investigate basal controls on the behaviour of contemporary ice streams. Artificial transects were set up across the Minch Palaeo-Ice Stream (NW Scotland) to mimic RES flight lines over Institute and Möller Ice Streams (Antarctica). We then explored how different data-resolution, transect orientation and spacing, and different methods, impact roughness measurements. Our results show that fast palaeo-ice flow can occur over a rough, hard bed, not just a smooth, soft bed, as previous work has suggested. Smooth areas of the bed occur over both bedrock and sediment covered regions. Similar trends in bed roughness values were found using Fast Fourier Transform analysis and standard deviation methods. Smoothing of bed roughness results can hide important details. We propose that the typical spacing of RES transects is too wide to capture different landform assemblages and that transect orientation influences bed roughness measurements in both contemporary and palaeo-ice-stream setting.