Pressure stimulated current in progressive failure process of combined coal-rock under uniaxial compression:Response and mechanism

Effective monitoring of the structural health of combined coal-rock under complex geological conditions by pressure stimulated currents(PSCs)has great potential for the understanding of dynamic disasters in underground engineering.To reveal the effect of this way,the uniaxial compression experiments with PSC monitoring were conducted on three types of coal-rock combination samples with different strength combinations.The mechanism explanation of PSCs are investigated by resistivity test,atomic force microscopy(AFM)and computed tomography(CT)methods,and a PSC flow model based on progressive failure process is proposed.The influence of strength combinations on PSCs in the progressive failure process are emphasized.The results show the PSC responses between rock part,coal part and the two components are different,which are affected by multi-scale fracture characteristics and electrical properties.As the rock strength decreases,the progressive failure process changes obviously with the influence range of interface constraint effect decreasing,resulting in the different responses of PSC strength and direction in different parts to fracture behaviors.The PSC flow model is initially validated by the relationship between the accumulated charges of different parts.The results are expected to provide a new reference and method for mining design and roadway quality assessment.

A novel binary effective medium model to describe the prepeak stressstrain relationship of combined bodies of rock-like material and rock

Combined bodies of rock-like material and rock are widely encountered in geotechnical engineering,such as tunnels and mines.The existing theoretical models describing the stress-strain relationship of a combined body lack a binary feature.Based on effective medium theory,this paper presents the governing equation of the“elastic modulus”for combined and single bodies under triaxial compressive tests.A binary effective medium model is then established.Based on the compressive experiment of concretegranite combined bodies,the feasibility of determining the stress threshold based on crack axial strain is discussed,and the model is verified.The model is further extended to coal-rock combined bodies of more diverse types,and the variation laws of the compressive mechanical parameters are then discussed.The results show that the fitting accuracy of the model with the experimental curves of the concretegranite combined bodies and various types of coal-rock combined bodies are over 95%.The crack axial strain method can replace the crack volumetric strain method,which clarifies the physical meanings of the model parameters.The variation laws of matrix parameters and crack parameters are discussed in depth and are expected to be more widely used in geotechnical engineering.

Compression failure conditions of concrete-granite combined body with different roughness interface

Bedrock and concrete lining are typical composite structures in the engineering field and the stability of the geological body and engineering body is directly connected to the mechanical properties of the composite body.Under this background,the study provides the transverse isotropic equivalent model of concrete-granite double-layer composite based on the notion of strain energy equivalence.Assuming that the strength failure of concrete and granite meets the Mohr-Coulomb criterion,then the strength failure model of the combined body considering the joint roughness coefficient(JRC)is derived,and the influences of JRC,the height ratio of concrete to granite,and confining pressure on the strength failure characteristics of the combined body are emphatically analyzed.Finally,the model applicability is illustrated by the uniaxial and triaxial compression tests on concrete monomer,granite monomer and concretegranite composite samples(CGCSs)with different JRCs.The results revealed that the compressive strength of the composite is closer to the concrete with lower strength in the combined body under different confining pressures.Adding interface roughness causes to raise the compressive strength of the composite due to interfacial adhesion between concrete and granite,and a slowing growth trend is observed in compressive strength as roughness.The model can provide a certain reference for the stability design and evaluation of engineering rock mass.

Failure behavior of a rock-coal-rock combined body with a weak coal interlayer

Using an MTS 815 testing machine,the deformation and failure behavior of a rock-coal-rock combined body containing a weak coal interlayer has been investigated and described in this paper.Uniaxial loading leads to the appearance of mixed cracks in the coal body which induce instability and lead to bursts in coal.If the mixed crack propagates at a sufficiently high speed to carry enough energy to damage the roof rock,then coal and rock bursts may occur-this is the main mechanism whereby coal bumps or coal and rock bursts occur after excavation unloading.With increasing confining pressure,the failure strength of a rock-coal-rock combined body gradually increases,and the failure mechanism of the coal interlayer also changes,from mixed crack damage under low confining pressures,to parallel crack damage under medium confining pressures,and finally to single shear crack damage or integral mixed section damage under high confining pressures.In general,it is shown that a weak coal interlayer changes the form of overall coal damage in a rock-coal-rock combined body and reduces the overall stability of a coal body.Therefore,the whole failure behavior of a rock-coal-rock combined body in large cutting height working faces is controlled by these mechanisms.

Experimental and numerical study of coal-rock bimaterial composite bodies under triaxial compression

To accurately predict coal burst hazards and estimate the failure of coal pillars in underground coal mining systems,it is of great significance to understand the mechanical behavior of coal-rock bimaterial composite structures.This paper presents experimental and numerical investigations on the response of rock-coal,coal-rock,and rock-coal-rock bimaterial composite structures under triaxial compression.The triaxial compression experiments are conducted under confining pressures in the range of 0-20 MPa.The resulting inside fracture networks are detected using X-ray-based computed tomography(CT).The experimentally observed data indicate that the mechanical parameters of the rock-coalrock composites are superior to those of the rock-coal and coal-rock combinations.After compression failure,the coal-rock combination specimens are analyzed via X-ray CT.The results display that the failure of the coal-rock composite bodies primarily takes place within the coal.Further,the bursting proneness is reduced by increasing confining pressure.Subsequently,the corresponding numerical simulations of the experiments are carried out by using the particle flow code.The numerical results reveal that coal is vulnerable with regard to energy storage and accumulation.

Firey linear combinations of convex bodies

For convex bodies,the Firey linear combinations were introduced and studied in several papers.In this paper the mean width of the Firey linear combinations of convex bodies is studied,and the lower bound of the mean width of the Firey linear combinations of convex body and its polar body is given.

Experimental Study on Dynamic Mechanical Properties of Sprayed Concrete-Surrounding Rock Combined Body

To investigate the dynamic response problem of the double medium formed by the adherence of sprayed concrete and surrounding rock in the tunnel,a split Hopkinson pressure bar of 75 mm in diameter was adopted at the ages of 3,7 and 10 d.Experimental results showed that dynamic compressive strength and dynamic increase factors(DIF)of the combined bodies increase with the strain rate.With the growth of strain rate,the critical strain of the combined bodies first increases,then deceases.Furthermore,the combined bodies of 3 d reveal the plastic property and brittle property for 7 d and 10 d when the strain rate is over 80/s.The failure characteristic of the sprayed concrete changes from tearing strain damage to crushing damage as the growth of strain rate,and the failure characteristic of rock presents the tensile failure mode as demonstrated by the scanning electron microscope(SEM).

THE DUAL BRUNN-MINKOWSKI INEQUALITIES FOR STAR DUAL OF MIXED INTERSECTION BODIES

In this article, some dual Brunn-Minkowski inequalities are established for star dual of mixed intersection bodies with respect to the harmonic p-combination and p-radial linear combination.

Combined Effects of Exposure to Noise and Vibration on Human Postural Equilibrium under Simulated Driving Conditions

There is little information about drivers’body balance responses to combined exposure of noise and vibration.To fill the gap,this study aims to investigate the combined effects of exposure to noise and whole-body vibration(WBV)on the body balance under simulated driving conditions.For this purpose,30 male participants were exposed to noise level at 85 dB(A)and two vibration levels(0.87 and 1.3 m/s^(2))in five sessions.The design of the study was repeated-measures,and it attempted to assess the effects of 40 minutes of exposure to noise and/or WBV.Moreover,the participants’fatigue was measured with the Borg scale(CR 10).The findings revealed there was a significant change in body sway after WBV and combined noise and WBV exposure(p<0.05).However,no significant difference was found in exposure to noise alone(p>0.05).The effect sizes of exposure to noise,WBV(1.3 m/s^(2)),and combined noise and WBV(1.3 m/s^(2))on body balance were 0.035,0.425,and 0.635,respectively.Also,single exposure to WBV caused more fatigue than single exposure to noise(p<0.05).Combined noise and WBV exposure descriptively caused more fatigue in comparison with the influence of WBV alone.The study concluded that the combined effects of exposure to noise and vibration are more than the sum of them.So,some synergistic effects may be observed in human body balance.It is essential to increase drivers’awareness and revise current health care interventions about new possible effects of combined exposures.

组合运动干预对肥胖女青少年身体成分、心血管风险因素及心肺适能影响的研究

背景目前,全球范围内肥胖儿童青少年数量急剧增加,其中,5~19岁人群肥胖患病率约增加了8倍,2~4岁儿童肥胖患病率约增加了1倍。运动干预对于改善肥胖和增强心肺适能具有重要影响。但缺乏组合运动干预对14~16岁肥胖女青少年影响的研究。目的探讨12周组合运动干预对肥胖女青少年身体成分、心血管风险因素及心肺适能的影响。方法于2022年5—7月在山东曲阜市选取14~16岁肥胖女青少年48名作为研究对象,将48名研究对象进行编号,然后利用随机数字分为试验组(24名)和对照组(24名)。试验组根据纳排标准最后纳入20名女生,整个干预过程持续12周,包括跳绳运动干预和跆拳道运动干预;而对照组在整个12周中不进行任何运动干预和其他饮食或者药物干预。分别在12周运动干预前和运动干预后检测受试者身高、体质量、体脂率、腰围、BMI、血压、空腹血糖(FPG)、胰岛素、胰岛素抵抗指数(HOMA-IR)及最大摄氧量(VO_(2max))等,并比较两组及干预前后各指标的差异。采用Pearson相关性分析探讨肥胖女青少年体脂率、腰围与VO_(2max)的相关性。结果干预前,两组女生年龄、身高、体质量、体脂率、腰围、BMI、收缩压(SBP)、舒张压(DBP)、脉压、FPG、胰岛素、HOMAIR、最大完成次数(Laps)、最大跑速(MAS)、VO_(2max)比较,差异均无统计学意义(P>0.05);12周运动干预后,试验组女生体脂率、腰围、SBP、DBP、FPG、胰岛素、HOMA-IR均低于对照组,而Laps、MAS、VO_(2max)高于对照组(P<0.05);与干预前比较,12周运动干预后试验组女生体脂率、腰围、SBP、DBP、FPG、胰岛素、HOMA-IR均降低,而Laps、MAS、VO_(2max)升高(P<0.05)。相关性分析结果显示,肥胖女青少年体脂率、腰围与VO_(2max)呈负相关(r=-0.55,P<0.001;r=-0.41,P<0.001)。结论12周组合运动干预能够改善肥胖女青少年身体成分和心血管风险因素,同时也能够通过增加VO_(2max)来增强心肺适能。

循环水岩作用下煤岩组合体力学响应及劣化机制

煤矿地下水库的建立解决了我国西部干旱-半干旱生态脆弱区的缺水问题。地下水库不断进行着蓄水-抽水,地下水库水位的反复升降对水库坝体产生反复损伤作用,而半煤岩坝体、煤岩夹矸坝体为地下水库常见的坝体。基于此,设计进行了不同“干燥-饱和”循环次数的砂岩-煤组合体不同围压下的轴向压缩试验,分析循环浸水作用下煤岩组合体力学特性劣化规律和劣化机制。结果表明:(1)随着循环次数的增加,组合体的饱和含水率逐渐增大。饱和含水率与循环次数呈对数关系。(2)随着循环次数的增加,应力-应变曲线压密阶段增长,弹性阶段斜率减小,峰值应力降低,峰值应变增大,屈服阶段愈加明显,应力跌落变缓。(3)随着循环次数的增加,组合体抗压强度逐渐降低,循环1~3次,抗压强度劣化幅度较为明显。抗压强度阶段劣化度具有非均匀性。(4)循环1~5次,黏聚力下降了70.87%,内摩擦角下降了60.65%。(5)循环1~3次,组合体弹性模量下降了53.06%,变形模量下降了61.10%。(6)循环浸水作用下,试样微观裂纹逐渐发育,矿物颗粒由原来的棱角分明的多边形向浑圆形逐渐发展,大的矿物颗粒逐渐崩解为小颗粒,颗粒间胶结作用逐渐弱化,由紧凑致密结构向松散软弱结构转变。(7)循环浸水作用下,水岩发生反复的物理、化学、力学作用,对煤岩产生反复损伤,最终导致宏观力学特性的劣化。

身体与道德:高校生态人格塑造的离身认知与具身转向

人与自然和谐共生的现代化需要以人格的生态化推进为先导,生态人格是应对中国环境问题的必然选择,也是对人类文明生态转向的积极回应。大学生作为中国式现代化事业的建设者和接班人,理应具备资源节约、环境友好的生态人格。当下高校生态人格塑造存在虚假需要与真实需要、工具理性与价值理性、外部环境与内在秩序、知善能力与行善意向等一系列矛盾,究其原因在于传统生态文明教育的重知观念和离身方式。以具身认知修正离身认知所表现出来的机械唯物主义弊端,需要重视认知主体与场域在认知产生中的作用,打造“心理场”“教育场”“文化场”“实践场”等育人场,织补新时代大学生人格的生态缺失,促进个体人格发展的完满,从而成长为新时代生态型高素质人才。

余吾矿煤/岩层组合类型划分及压裂措施

为了划分煤/岩层水力压裂组合类型,以潞安矿区余吾矿3#煤层为研究对象,通过测井解释及力学测试得出顶板岩性及力学特征;采用取心井与测井相结合识别出煤层段的煤体结构;根据水力压裂计算地应力方法结合密度测井得出了地应力状态;由此划分出水力压裂煤/岩层组合类型,并提出了不同组合类型下的水力压裂措施建议。结果表明:研究区水力压裂煤/岩层组合类型可以划分为硬岩硬煤、软岩硬煤、硬岩软煤、软岩软煤组合的过渡型和拉张型等7种类型;硬岩硬煤组合类型时,采用大排量、多液量、低/中砂比、逐级加砂方式能营造出较长裂缝并能有效支撑;软岩硬煤组合时,应避射部分煤层,防止水力压裂裂缝进入煤层与软岩交界面,影响压裂效果;硬岩软煤拉张组合时,建议采用顶板水力压裂;进行硬岩软煤过渡型水力压裂时,根据水平应力与垂直应力的差值优化压裂参数;软岩软煤组合时,不建议采用水力压裂方式进行改造。

基于人体系统的疫病病证结合诊疗模式研究与实践

中医传统疫病辨证方法均以“藏象辨证”作为理论基石,但“藏象辨证”理论具有模糊性、抽象性等特点,不利于当前疫病诊疗体系的发展。在针对2020年武汉新冠肺炎的防治中,在“藏象辨证”基础之上,归纳总结出基于人体系统的疫病病证结合诊疗模式。该模式理论基础包括人体解剖学、藏象学说、药物归经理论,以及现代人体系统理论。原则与方法:病证合参,确定病所;病证合治,系统用药;病证合估,评定疗效。特色与优势:唯物论与辩证法、整体与局部、辨病与辨证、定性与定位、抽象与具象相结合。以疫病诊疗实践为例,阐释该模式的运用过程。该模式的构建促进了对中医和现代医学发展有关问题的深入思考。

高校“强基计划”选拔中的“体智结合”——基于36所高校“强基计划”体测项目的比较与分析

研究目的:研究36所高校“强基计划”招生简章中的体育加试内容设置及分值占比,为高校“强基计划”选拔中的“体智结合”提供帮助。研究方法:采用文献资料法、数理统计法对36所高校的招生简章、体测项目设置以及评分标准进行比较与分析。研究结果:无故不参加体育加试及体育加试不合格的学生不予录取或取消相关资格的学校有24所;条件相同(文化考试总成绩)下优先录取体育加试成绩优秀的为9所。各校体测项目设置与《国家学生体质健康标准》基本一致(选取其中几项),部分高校还选取了《普通人群体育锻炼标准》中相应的内容;各校体测项目的评分标准与《国家学生体质健康标准》高三群体基本一致;少部分高校由院校自主设置评分标准;调查发现还有35所高校未选取耐力跑作为体测项目;仅8所高校体测项目在4项以上;大部分高校选取身体机能和身体形态以及速度、爆发力等作为体测项目。研究结论:人才选拔应“强基先固本”,健康的体魄应作为高校选拔的必要和前提条件。建议:注重基本体质、体能检测,注重基本运动技术技能加试,注重中学与大学体测项目的衔接,体测项目设置个性化。

Effects of water intrusion and loading rate on mechanical properties of and crack propagation in coal–rock combinations

Tackling the problems of underground water storage in collieries in arid regions requires knowledge of the effect of water intrusion and loading rate on the mechanical properties of and crack development in coal–rock combinations. Fifty-four coal–rock combinations were prepared and split equally into groups containing different moisture contents(dry, natural moisture and saturated) to conduct acoustic emission testing under uniaxial compression with loading rates ranging from 0.1 mm/min to 0.6 mm/min. The results show that the peak stress and strength-softening modulus, elastic modulus, strain-softening modulus, and post-peak modulus partly decrease with increasing moisture content and loading rate. In contrast, peak strain increases with increasing moisture content and fluctuates with rising loading rate. More significantly, the relationship between stiffness and stress, combined with accumulated counts of acoustic emission, can be used to precisely predict all phases of crack propagation. This is helpful in studying the impact of moisture content and loading rate on crack propagation and accurately calculating mechanical properties. We also determined that the stress thresholds of crack closure, crack initiation, and crack damage do not vary with changes of moisture content and loading rate, constituting 15.22%, 32.20%, and 80.98% of peak stress, respectively. These outcomes assist in developing approaches to water storage in coal mines, determining the necessary width of waterproof coal–rock pillars, and methods of supporting water-enriched roadways, while also advances understanding the mechanical properties of coal–rock combinations and laws of crack propagation.

刍议慢性心力衰竭的气血津液辨治

气血津液皆中焦脾胃所化生,功能上互生互济,故而气虚、气滞、血虚、血瘀、水饮等气血津液的病理过程也常相继发生。“血不利则为水”阐明了气分、血分、水分的病理因果关系,可用以解释慢性心力衰竭(慢性心衰)的病变过程,认为慢性心衰常见病因皆可导致气的化生及气的功能障碍,进而引起“血不利”,所化之水饮停聚肌肤、脏腑组织间隙导致“水不利”,水饮、瘀血互结日久化热酿毒,则蚀脉伤肌,变证丛生。治疗应补气兼顾理气,活血利水不忘养血,恰当配伍清热解毒药,希冀在减少慢性心衰心血管事件方面获得较好的疗效。

Meat Production Performances of Geese in Different Crossbred Combinations

[Objective] To study the meat production performance of geese in different crossbred combination, and provide a reference for cultivating new multiplication strains of meat geese. [Method] A total of five goose breeds including Taihu goose (T), Wulong goose (WL), Wanxi white goose (WX), Sichuan white goose (SC) and Sanhua goose (SH) were used as research objects, and eight crossbred combinations were designed. The body measurements, slaughter performance, conventional meat quality and muscle composition of 90-day-old geese in eight crossbred combinations were determined and comparatively analyzed. [Result] All the body measurement indexes except thurl width of WXSC combination were the biggest in the eight crossbred combinations. Contrarily, the body measurement indexes of SHSC combination, including average body weight, body slope length, breast depth, breast width, shank length, neck length and half-diving depth were the lowest in the eight crossbred combinations. The live weight, slaughter weight and abdomen fat weight of WXSC combinations ware 3 291.36, 2 956.46 and 77.84 g, respectively, which were the biggest in eight crossbred combinations. The slaughter rate of SHWL combinations was 92.96%, and more than other crossbred combinations. The shear force of SHT and WXWL combinations were the lowest (3.09 kg) and the highest (3.78 kg), respectively. The water holding capacities of SCWL and WXSC combinations were the highest (66.46%) and the lowest (61.48%), respectively. The percentage of moisture content of SHWL and SCT combinations were the highest (73.05%) and the lowest (66.77%), respectively. The crude protein content of SHT and SHWL combinations were the highest (23.32%) and the lowest (21.94%), respectively. The percentage of crude fat content of SHT and SCWL combinations were the highest (3.06%) and the lowest (1.67%), respectively. [Conclusion] The growth rate of WXSC combination is the fastest, and the meat performance of SHT combination is the best.

不同倾角充-岩组合体三轴压缩力学特性及破坏特征

为探究交界面倾角β对充填体与围岩组合体(充-岩组合体)三轴力学特性影响规律,开展β为0°、15°、30°、45°和60°的充-岩组合体三轴压缩试验,对比分析了不同交界面倾角组合体的力学特性、破坏特征与强度演化规律。试验结果表明:当β≤30°时,组合体的应力-应变曲线可划分为孔隙压密、弹性变形、塑性变形和破坏发展4个阶段,其破坏特征以充填体压剪破坏为主;随着交界面倾角增加,组合体在达到峰值强度后应力陡降,无明显塑性变形和破坏发展阶段,其破坏特征由充填体内部压剪破坏逐渐转变为沿交界面滑移破坏;组合体的峰值强度随着交界面倾角增加先增大后减小,β=30°时峰值强度达到极大值。基于单弱面理论得到组合体滑移破坏的交界面临界倾角为57°~68°,其中β=60°时组合体发生沿交界面滑移破坏,理论计算与试验结果相吻合。