Single Stratum Research Articles

Types of connected components of the singular locus of the moduli space of compact Riemann surfaces

AbstractIn 2012 G. Bartolini and M. Izquierdo showed that all equisymmetric strata of Broughton’s stratification, corresponding to the actions of groups of order 2 and 3 on Riemann surfaces of genus g are contained in the same connected component $$\mathcal {C}_g^{2,3}$$ C g 2 , 3 of the singular locus $$\mathcal {S}_g$$ S g . The other components that were known to the literature were those composed of points of certain single strata. This motivated the question of whether the singular locus can contain connected components different from $$\mathcal {C}_g^{2,3}$$ C g 2 , 3 and being the union of at least two strata. The existence of such components was proved for infinitely many genera by G. Gromadzki and the author. In this paper, we will describe and classify all types of connected components of the singular locus. In particular, we prove that every connected component different than $$\mathcal {C}_g^{2,3}$$ C g 2 , 3 coincides with some Cornalba component, and we give necessary and sufficient conditions for a cyclic action to define such a component.

Mathematical modelling for strata deformation caused by rectangular pipe jacking construction in composite layered ground

In this study, analytical solutions of vertical deformation of ground surface and horizontal displacement of strata are derived combining the Mindlin solution and the mirror method due to rectangular pipe jacking tunneling in composite strata, which considers the combined effect of five factors of additional excavation pressure, friction of rectangular pipe jacking and soils, segment-soil friction, grouting filling and strata loss, respectively. The theoretical calculation results were verified against the measured data in two project cases. Moreover, effect factors of rectangular jacking pipe cross-sectional dimensions, embedment of tunnel axial depth, elasticity modulus on the interlayer and the Poisson's ratio of the interlayer on strata deformation is investigated. The results imply that the theoretical calculation values obtained using this method are more closely correlated with the observed values compared to those computed using the single stratum model. The primary cause of terrene upheaval in front of the working surface is the increased excavation pressure on the working face and the horizontal displacement of the deep soils and the surface subsidence behind the excavation face is resulting from the soil loss as the main influencing factor. The varying cross-section size of pipe jacking is able to impact on the vertical deformation of the soil, but it has a limited impact on the lateral displacement of the strata. The affection of the buried depth of the tunnel axis on strata deformation is more notable in the rectangular pipe jacking construction. As the axial tunnel depth growth, the ground surface maximum subsidence value gradually decreases, while the crest value of horizontal distortion mildly increases. When the rise of the interlayered modulus of elasticity, the maximum earth surface subsidence enlarged gradually while the subsidence trough slight diminution. Moreover, the greatest horizontal displacement exhibits a relatively minor fluctuation, but there is a trend of upward movement in the position. The influence of Poisson's ratio of the interlayer on the strata deformation is comparatively weak.

Patients with Down Syndrome and High-Risk B-Acute Lymphoblastic Leukemia Demonstrate Improved Outcomes on a Modified Chemotherapy Regimen: A Report from Children's Oncology Group Study AALL1131

Introduction: Children with Down syndrome (DS) have a 20-fold increased risk of developing B-acute lymphoblastic leukemia (B-ALL), and demonstrate an increased risk of both relapse and treatment-related mortality (TRM). The Children's Oncology Group (COG) High-Risk (HR) B-ALL trial AALL0232 was permanently closed to DS HR patients due to excessive TRM, primarily due to overwhelming sepsis during times of severe neutropenia. On the successor HR B-ALL trial AALL1131, a primary objective for DS patients was therefore to reduce TRM by enhancing supportive care and modifying some elements of therapy. Methods: DS HR patients were treated on a single non-randomized stratum, with several modifications compared to non-DS HR patients. The majority of DS HR patients received a three-drug Induction, with only slow early responders (M2/M3 marrow at Induction day 15) receiving a single dose of anthracycline (daunorubicin 50 mg/m 2). Interim Maintenance 1 (IM-1) consisted of four IV courses of intermediate dose (ID; 2,000 mg/m 2) rather than high-dose methotrexate (HD MTX; 5,000 mg/m 2), with leucovorin rescue beginning earlier, at hour 30 and advancing if tolerated to hour 36, rather than at hour 42. Maintenance modifications included administration of vincristine/steroid pulses every 12 instead of every 4 weeks, and equal duration of therapy for boys and girls. Results: Patient characteristics (Table 1) were similar among the 280 DS HR patients and 5,612 non-DS HR patients except for more frequent bone marrow minimal residual disease (BM MRD) >0.01% in DS vs non-DS patients both at end of Induction (EOI; 54.1% vs 34.9%, p <0.0001) and at end of consolidation (EOC; 23.9% vs 12.0%, p=0.001). DS HR patients were also less likely to have favorable or unfavorable cytogenetics (p <0.0001). In terms of tolerability of the modified IM-1 phase, the duration was significantly longer in DS vs non-DS patients (mean 80.0 ± 16.6 days vs 74.0 ± 14 days, p <0.0001), and delays over 14 days were significantly more frequent (9.7% vs 4.7%, p=0.001). Nevertheless severe toxicities during IM-1 were low, with only 2 DS HR cases of grade 4 mucositis, 2 grade 4 infections, and 1 grade 5 event (sudden death, not otherwise specified). AALL1131 successfully achieved an induction death rate <10% in DS HR patients, although the rate remained significantly higher than in non-DS patients (3.6% vs 1.7%, p=0.035). Event-free survival (EFS) and overall survival (OS) in DS HR patients were improved compared to outcomes on older trials but remained significantly lower than non-DS patients (Figure 1), with 5-year EFS 69.1 ± 3.1% vs 79.5 ± 0.6% (p <0.0001), and 5-year OS 83.3 ± 2.5% vs 88.4 ± 0.5% (p=0.0005). Among DS HR patients, outcomes were particularly poor among those with EOC MRD >0.01% compared to those with EOC MRD <0.01% (5-year EFS 25.8 + 9.9% vs 62.2 + 6.6%, p <0.0021; 5-year OS 54.0 + 12.2% vs 88.1 + 4.5%, p <0.0003). Conclusion: AALL1131 achieved the goal of decreasing induction mortality for DS HR patients, and the modified IM-1 phase utilizing ID MTX with early leucovorin rescue was well-tolerated, with minimal grade 4-5 toxicities, despite a longer mean duration and more frequent treatment delays compared to non-DS patients receiving HD MTX. DS HR patients continued to demonstrate disparities in EOI and EOC MRD levels, as well as in 5-year EFS and OS. Innovative strategies utilizing targeted therapies and immunotherapy are needed to further improve outcomes for patients with DS HR ALL.

Methodology reporting improved over time in 176,469 randomized controlled trials

ObjectivesTo describe randomized controlled trial (RCT) methodology reporting over time. Study Design and SettingWe used a deep learning-based sentence classification model based on the Consolidated Standards of Reporting Trials (CONSORT) statement, considered minimum requirements for reporting RCTs. We included 176,469 RCT reports published between 1966 and 2018. We analyzed the reporting trends over 5-year time periods, grouping trials from 1966 to 1990 in a single stratum. We also explored the effect of journal impact factor (JIF) and medical discipline. ResultsPopulation, Intervention, Comparator, Outcome (PICO) items were commonly reported during each period, and reporting increased over time (e.g., interventions: 79.1% during 1966–1990 to 87.5% during 2010–2018). Reporting of some methods information has increased, although there is room for improvement (e.g., sequence generation: 10.8–41.8%). Some items are reported infrequently (e.g., allocation concealment: 5.1–19.3%). The number of items reported and JIF are weakly correlated (Pearson's r (162,702) = 0.16, P < 0.001). The differences in the proportion of items reported between disciplines are small (<10%). ConclusionOur analysis provides large-scale quantitative support for the hypothesis that RCT methodology reporting has improved over time. Extending these models to all CONSORT items could facilitate compliance checking during manuscript authoring and peer review, and support metaresearch.

On the structure of connected components of the moduli spaces of compact Riemann surfaces

Using the Broughton’s equisymmetric stratification of the moduli space of compact Riemann surfaces of genus g ge 2, Bartolini, Costa and Izquierdo have shown that its singular locus S_{g} is disconnected except for g = 3, 4, 7, 13, 17, 19, 59. One of a lot of problems motivated by this result concerns the study of its connected components, both from the quantitative and qualitative points of view. In 2012, Bartolini and Izquierdo have shown that all strata corresponding to the actions of Z_{2} and Z_{3} are contained in a single connected component C^{2,3}_g. The other components which were known to these authors were those composed by single strata and they asked whether there are components different from C^{2,3}_ g being the union at least two equisymmetric strata. The aim of this paper is to give an affirmative answer to this question, by showing that there are connected components composed of precisely two strata in S_{g} for g = rp(p -1)/2 where r ge 6 and p > 5r + 3 is a prime for which pr + 2 is also a prime.

Leaf functional traits and pathogens: Linking coffee leaf rust with intraspecific trait variation in diversified agroecosystems.

Research has demonstrated that intraspecific functional trait variation underpins plant responses to environmental variability. However, few studies have evaluated how trait variation shifts in response to plant pathogens, even though pathogens are a major driver of plant demography and diversity, and despite evidence of plants expressing distinct strategies in response to pathogen pressures. Understanding trait-pathogen relationships can provide a more realistic understanding of global patterns of functional trait variation. We examined leaf intraspecific trait variability (ITV) in response to foliar disease severity, using Coffea arabica cv. Caturra as a model species. We quantified coffee leaf rust (CLR) severity-a fungal disease prominent in coffee systems-and measured key coffee leaf functional traits under contrasting, but widespread, management conditions in an agroforestry system. We found that coffee plants express significant ITV, which is largely related to shade tree treatment and leaf position within coffee canopy strata. Yet within a single plant canopy stratum, CLR severity increased with increasing resource conserving trait values. However, coffee leaves with visible signs of disease expressed overall greater resource acquiring trait values, as compared to plants without visible signs of disease. We provide among the first evidence that leaf traits are correlated with foliar disease severity in coffee, and that functional trait relationships and syndromes shift in response to increased disease prevalence in this plant-pathogen system. In doing so, we address a vital gap in our understanding of global patterns of functional trait variation and highlight the need to further explore the potential role of pathogens within established global trait relationships and spectra.

Sources of Formation of the Cossack Officer in Ukraine (second half of the 16th — middle of the 17th century)

The article clarifies the sources of the formation of Cossack officer in the second half of the 16th to the middle of the 17th centuries. It is emphasized that this cohort, as a rule, included financially well-off and educated people with the appropriate intellectual potential and level of culture. With the establishment of the military register, the senior ranks included mainly the nobility, who from a young age, in the spirit of the traditions of the time, attended the school of chivalry in Zaporozhye. It was often joined by representatives of the princely class: Zbarazhsky, Zaslavsky, Koretsky, Ruzhynsky, and Vyshnevetsky. The eldership was also replenished with descendants of boyars and peasants, who had to look for places in the social structure of the Polish-Lithuanian Commonwealth. The nature of occupations, ethnicity, values established in its environment contributed to the consolidation of the Cossack elite into a single social stratum. Important factors in this process were also the struggle of the Cossacks for the defense of their constitutional rights and the support of Orthodoxy in Ukraine.

Research on Leakage Mechanism of Underwater Shield Tunnels with Different Soil Layers during Operation Period

Different soil layer properties have great influence on tunnel leakage. In this paper, the finite element software is used to analyze the homogeneous leakage model of different soil layers and different degrees of lining deterioration. The working conditions of different soil layer properties and different degrees of lining deterioration are established by means of soil layer permeability coefficient and lining permeability coefficient, and the law of tunnel leakage under each working condition is analyzed. This paper innovatively explores the relationship between the severity of tunnel seepage caused by different lining deterioration and the soil layer properties of the tunnel. Finally, by comparing the field survey data of Dinghuaimen with the leakage law and mechanism summarized by the model, the reliability and feasibility of the model method to explore the leakage mechanism are verified. The model test results are consistent with the project survey data. In this paper, the seepage law and mechanism of underwater shield tunnel are explored and the result shows: (1) The leakage laws and stress distribution laws of a single homogeneous soil layer with different strata properties are similar. The flow velocity in the lower half of the tunnel lining is greater than the upper half, and the maximum velocity occurs at the arch foot; the velocity inside the lining is much smaller than that inside the soil layer. The maximum absolute value of the axial stress of the lining occurs at the arch waist on the left and right sides, and the minimum values of the axial stress of absolute values all occur at the dome. (2) The leakage of underwater tunnels is related to the properties of soil layers. The larger the soil permeability coefficient is, the more serious the deterioration of the tunnel lining will be, and the more serious the tunnel leakage will be. (3) The leakage of complex strata follows the law of leakage in a single homogeneous stratum. The leakage of the tunnel is the most serious in the fine sand layer with the largest permeability coefficient. Moreover, when the seepage phenomenon occurs, the water flow tends to seep along the fine sand layer to the tunnel.

Research on Formation Mechanism and Evolution Pattern of Bed Separation Zone during Repeated Mining in Multiple Coal Seams

Mastering the formation mechanism and dynamic evolution pattern of bed separation zone during repeated mining is the key to the success or failure of separation grouting injection technology. Taking a mine in Ningdong as the engineering background, using the research methods of theoretical analysis, numerical simulated, and field measurement, four overburden structure models of single or multiple key strata with repeated mining and single or multiple key strata without repeated mining were constructed. The evolution pattern of bed separation zone was studied from four aspects: bed separation zone development mechanism, formation position, development form, and change of clearance. The results showed that when a single key stratum of repeated mining exists between coal seams, it is difficult to form a large separation area because there is no key stratum during the upper coal mining, and a separation area will be formed below the key stratum when mining the lower coal. When the key stratum exists above all coal seams, a large separation zone will be formed under the key stratum when the upper coal is mined. When mining the lower coal, when the coal seam spacing is less than 4 times of the mining height of the lower coal, the crack will penetrate the upper coal floor. If the key stratum is not completely broken, secondary separation may occur. When multiple key strata are all located above all coal seams, there will be bed separation zone under the high-level key stratum. When multiple key strata and coal seams are distributed at intervals, the separation below the high-level key stratum during upper coal mining and the separation below the low-level key stratum during lower coal mining are formed. Because the high-level key stratum bends and sinks after being affected by the mining of coal 1, the clearance of bed separation during mining coal 2 is slightly less than that during mining coal 1, which is contrary to the pattern that the greater the bed separation clearance increases with the increase of mining height.

Deformation and Control of Super-Large-Diameter Shield in the Upper-Soft and Lower-Hard Ground Crossing the Embankment

Compared with the small diameter and the single stratum shield tunnel, the surface subsidence is much greater when the large-diameter shield passes through the upper-soft and lower-hard stratum. In this case, it is particularly important to control the deformation of the embankment when the large-diameter shield passes underneath the embankment. Taking a tunnel project underneath the north embankment in Zhuhai as an engineering example, this paper investigates the deformation characteristics and safety control measures of a super-large-diameter (i.e., 15.80 m) shield tunnel underneath the embankment under complex stratum conditions in upper-soft and lower-hard strata, using on-site monitoring and three-dimensional numerical simulations. The results of the numerical simulation show that grouting can effectively reduce the settlement of the embankment. Grouting is applied to practical engineering, and the monitoring data are in agreement with the numerical simulation results. The surface subsidence of the embankment gradually increases as the shield tail leaves the monitoring section and finally stabilizes. After the shield machine has passed through the embankment, the horizontal deformation troughs on the embankment’s surface conform to the Gaussian normal distribution. The maximum settlement occurs in the area directly above the central axis of the tunnel. The deformation trough covers an area about four times the diameter of the tunnel on both sides of its center line.

Composition and structure of a low semi-thorn shrubland in Northeastern Mexico

Background: The plant community in southern Texas and the adjacent region in Mexico is Tamaulipan thornscrub (MET). However, the recently published proposals for quantitative hierarchical classification have evidenced the presence of more communities and the need for quantitative descriptions of these associations to determine their conservation status.&#x0D; Question: What is the structure and floristic composition of a semi-thorn shrubland in Reynosa’s northwestern region?&#x0D; Studied species: Tamaulipan low semi-thorn scrubland.&#x0D; Study site and dates: Hills in Reynosa’s northwestern region (Tamaulipas), Mexico. August 2018-July 2019.&#x0D; Methods: Abundance, height and coverage of each plant species were measured on 33 plots of 10 × 10 m. Horizontal structure was analyzed by Importance Value Index, vertical structure was estimated through a modification of the Pretzsch Index and in addition alpha diversity indices were calculated.&#x0D; Results: Richness was 55 species, within 54 genera and 25 families. The importance values were centered mainly in small, spineless shrub species ( Lippia graveolens , Calliandra conferta , Turnera diffusa and Krameria ramosissima ). The vertical structure presented four defined strata with 50 % of species equally represented in all strata and the remaining 50 % restricted to a single stratum (A = 2.86, Amax = 5.39, Arel = 52.98 %). The species with the highest proportional density were distributed only in stratum IV (0-1.12 m).&#x0D; Conclusions: The community is a clearly defined low semi-thorn scrubland. The structural characteristics indicate that it can be a possible transition plant association between MET and piedmont scrub. This reinforces the proposals of the recently published classification systems.&#x0D; &#x0D; &#x0D; Translate&#x0D; stop&#x0D; &#x0D; &#x0D; &#x0D; &#x0D; &#x0D; Translate&#x0D; stop&#x0D; &#x0D; &#x0D;

Research on Roof Structure and Determination of Working Resistance of Shallow Buried Single Key Stratum Based on Grid Drillhole Field Method

Abstract The roof structure of the stope is the core of revealing the weighting mechanism and determining the working resistance of support. The Shenfu Dongsheng coal field of China has abundant reserves of shallow coal seam. The phenomena of strong ground pressure and step subsidence caused by the mining of shallow buried single key stratum (SBSKS) poses a serious threat to the fragile environment. Revealing the shape and movement process of roof structure of SBSKS is the primary prerequisite for ensuring safe mining of working face. Firstly, the field measurement technology of the space grid-like drill field was developed to construct vertical holes and incline holes in the auxiliary headgate gateway and tailgate airway ahead of the working face and to obtain the measured data of the broken position and vertical displacement of the roof by the drilling peep and multipoint displacement. Secondly, the key parameters of the stope roof were analyzed by the grid drillhole filed method, for example, the inclined roof break angle, the rotation angle, the thickness of equivalent immediate roof (EIR), and the roof structure-articulated level and shape. Then, we combined with the mining face comparison of compression laws revealing the time and space relationship between the movement of the roof structure and the roof weighting, and three more dangerous states of the roof were determined. Finally, the roof structure of SBSKS is moved upward through the field research on the 22201 working face, the “high step rock beam” structure and the advanced breaking position of the roof are obtained, and the calculation equation of the support resistance in large mining height face is given. The research results provide scientific guidance for the safety of SBSKS coal seam and provide technical support for green mining in ecologically fragile mining areas.

Research on Stratum Identification Method Based on TBM Tunneling Characteristic Parameters

In order to obtain continuous stratum information during TBM tunneling, using TBM tunneling parameters, stratum recognition is carried out through the K‐nearest neighbor model, and the model is improved by the entropy weight method to improve the stratum recognition rate. By analyzing the correlation between TBM tunneling characteristic parameters and stratum, the tunneling characteristic parameter vector which is most sensitive to the stratum is obtained by sensitivity analysis, and the stratum recognition model based on the K‐nearest neighbor algorithm is established. Aiming at the problem that the model has a large error in complex formation recognition, a formation recognition model based on the entropy weight K‐nearest neighbor algorithm is established, and the wrong data of the K‐nearest neighbor model is recalculated. The recognition rate of the stratum in the new model is increased from 90.95% to 98.55%. The results show that the K‐nearest neighbor model has a better recognition effect for the interval with single stratum distribution, and the recognition rate of entropy weight K‐nearest neighbor model for complex stratum is significantly improved, which provides an effective method to obtain stratum information by using tunneling characteristic parameters.

Roof structure of shallow coal seam group mining in Western China.

In order to realize roof control of shallow coal seam group mining in Western China, combining with engineering statistics, physical simulation and theoretical analysis, the roof weighting characteristics during lower coal seam mining were revealed, and the classification of shallow coal seam group was proposed. Based on this, mechanical models of roof structure were set up, and the calculation method of support resistance was determined. The results show that the roof weighting is closely related to the interburden thickness and the mining height of lower coal seam, considering the ratio of interburden thickness to the mining height, as well as the key stratum structure, the classification of shallow coal seam group was put forward. The first type is shallow coal seam group with no key stratum (SCSG-No), its roof pressure is mainly affected by caving roof of upper coal seam, and the interburden roof forms slanting pillar-beam structure. The second type is shallow coal seam group with single key stratum (SCSG-S), interburden roof represents step voussoir beam structure. The third type is shallow coal seam group with double key strata (SCSG-D), interburden roof can form double key strata structure, the lower key stratum forms slanting step voussoir beam structure, while the upper key stratum forms voussoir beam structure, besides, longwall face represents large—small periodic weighting. Through establishing the roof structure models, the calculation formulas of support resistance were determined, it can provide basis for roof control and promote safe mining in Western China.

Bracken fern (Pteridium aquilinum (L.) Kuhn) overgrowth on dry Alpine grassland impedes Red List Orthoptera but supports local orthopteran beta diversity

The native bracken fern (Pteridium aquilinum (L.) Kuhn) has become increasingly invasive in abandoned or undergrazed Alpine grasslands. Bracken stands are generally assumed to be poor in species, but there is still very little information about the impact on the fauna. We recorded Orthoptera communities of 24 sample plots with varying bracken cover. Compared to plots with only sparse or medium bracken cover, species richness was highly significantly lower in densely overgrown plots, while the former two did not differ markedly. Multivariate ordination analyses revealed gradients with unequal orthopteran communities, showing distinct patterns of bracken cover clustering. Based on indicator values, 13 of 23 Orthoptera species turned out to be significantly or marginally significantly associated with a single bracken cover stratum or a combination of two strata, whereby all nine Red List species were primarily restricted to sparse or medium bracken cover. However, some generalist species were found to favor denser bracken stands, such as Tettigonia viridissima, contributing to the local Orthoptera beta diversity. Our data suggest that ongoing rotational sheep grazing with temporary paddocks is regarded as the most preferable management system. However, selected parts of the study area, which have only sparse vegetation and no pressure of bracken or scrub overgrowth, are recommended to be alternately left ungrazed for a few years to allow for the coexistence of different successional stages. Low-intensity bracken control measures, situationally by mowing or uprooting, are considered appropriate and should be pursued.Implications for insect conservationEven though most specialized and rare Orthoptera species in Western Europe tend to prefer sparsely vegetated areas, subareas with medium to even dense vegetation cover might promote certain generalist species, leading to a higher local species richness.

Distribution and abundance of sei whales off the west coast of the Falkland Islands

AbstractLittle information exists on the current status of Southern Hemisphere sei whales (Balaenoptera borealis). We assessed their distribution and abundance along the west coast of the Falkland Islands (southwest Atlantic) during February and March 2018, using line transect and nonsystematic surveys. Abundance estimates were generated for a single survey stratum using design‐ and model‐based approaches. Sightings of sei whales and unidentified baleen whales (most, if not all, likely to be sei whales) occurred from the coast to the 100 m depth isobath that marked the offshore boundary of the stratum. The modeled distribution predicted highest whale densities in King George Bay and in the waters between Weddell Island and the Passage Islands. Sei whale abundance was estimated as 716 animals (CV = 0.22; 95% CI [448, 1,144]; density = 0.20 whales/km2) using the design‐based approach, and 707 animals (CV = 0.11; 95% CI [566, 877]; density = 0.20 whales/km2) using the model‐based approach. For sei whales and unidentified baleen whales combined, the equivalent estimates were 916 animals (CV = 0.19; 95% CI [606, 1,384]; density = 0.26 whales/km2) and 895 animals (CV = 0.074; 95% CI [777, 1,032]; density = 0.25 whales/km2). The data indicate that the Falkland Islands inner shelf region may support globally important seasonal feeding aggregations of sei whales, and potentially qualify as a Key Biodiversity Area.

Influence of Valleys Terrain on Pressure of Fully Mechanized Working Faces in Shallow Coal Seams

The absence of a key stratum during overburden rock movement is crucial to the mining pressure of fully mechanized coal mining faces. Using physical and numerical simulations, the 21304 mechanized mining in Daliuta and Huojitu coal mining faces 1−2 appeared twice during a pressure frame accident analysis. The results indicate that a lack of key overlying strata is crucial to the mining of lower coal seams, particularly for the upper sections of a single key stratum of coal. When the key stratum of the upper coal seam is absent, a stable masonry structure is formed after mining. It is easy to form stable stacked strata at the bottom of a coal seam. When developing gullies in deep terrains, the formation of the key stratum will be an upper rock fracture affected by the impact, resulting in a partial absence of the key stratum. When the key stratum is absent, the mining of upslope working faces and the probability of dynamic strata pressure increase with the overburden on the working face and mining of downslope faces. The face mine pressure development laws on the upper and lower coal seam mining were similar, mainly manifesting as “slope section &gt;valley bottom section &gt;back slope section.”

The Influence of Overburden Structure on Mine Ground Pressure Appearance in Working Face with Super-large Mining Height: a Case Study in Shendong Mining Area

The Shendong mining area where is located in the northwest of China has the highest fully mechanized working face in the world. The purpose of this paper is to understand the causes of abnormal mine ground pressure appearance (MGPA) on the fully mechanized mining working face with super-large height in Shendong mining area. Field monitoring, physical similarity material test and UDEC numerical simulation were used to investigate the influencing factors of abnormal MGPA on the super-large mining height working face. The results show that the simultaneous breaking movement of multiple key strata will transfer more load than that of a single key stratum, which intensifies the MGPA in working face. The distance between primary key stratum and coal seam determines MGPA, but this distance is limited to 115 m above the coal seam. The results of this study are of guiding significance to control the MGPA in Shendong mining area.

Breaking and Instability Movement Characteristics of High-Position Double-Layer Hard Thick Strata due to Longwall Mining

With multilayer hard roof occurring above the mining area, the strata behaviors will be significantly affected by their special characteristics and interaction. In this paper, relying on the mining background of panel 1061 of a coalmine, the breaking instability of double-layer hard thick strata (DLHTS) and the precursory information of disasters are studied by using theoretical analysis, numerical simulation, and physical simulation. Results show that the DLHTS have bearing, blocking, and controlling effects. Prior to DLHTS breaking, the horizontal development of stress concentration zone and plastic zone can be controlled, and the overburden movement is gentle, while during the breaking process, the stress drops abruptly, the plastic zone expands longitudinally rapidly, the overburden moves notably, and the energy release is sharp, which is likely to directly cause strong dynamic pressure. Moreover, the DLHTS can interact with and influence each other; that is to say, the breaking of lower magmatic rock (LMR) can provide sufficient space for that of upper magmatic rock (UMR), while the UMR breaking can promote the LMR periodic breaking in turn and cause its secondary instability, thereby easily causing complex or composite dynamic disasters’ formation. Hence, compared with single hard thick stratum occurrence, the strata behaviors affected by DLHTS breaking and instability are normal and more intense. Study results can provide a scientific basis for the prevention and control of dynamic disaster with hard thick stratum occurrence and important guidance value for promoting safe and efficient production of coalmines.

The Bearing Capacity Evaluations of a Spread Footing on Single Thick Stratum or Two-Layered Cohesive Soils

Nowadays many countries plan to increase the percentages of renewable energies by developing offshore wind power. Due to the large sizes of offshore foundations, such as spudcan footings of jack-up barges or pile anchors of wind turbines, the affected soil depth range caused by the foundation under loading can be relatively deep, so the affected range may include a single thick layer or stratified soils. This paper utilizes limit analysis and FLAC numerical simulation to investigate the bearing capacity of a footing on single thick stratum or two-layered cohesive soils. Under nature deposition condition, the undrained shear strength of most cohesive soil approximately increases linearly as the depth increases. The closed-form upper bound solutions of fully rough or fully smooth footings on thick cohesive soils are provided, for the purpose of fast evaluations in practical engineering, and the outcomes are within the results from the FLAC simulation and slip circle method. The problems of punch-through shear failure or soil squeezing could be critical for two-layered soils under some conditions, and the associated bearing factors and the failure mechanisms from different methods are demonstrated and discussed in the article.