Mechanical analysis of effective pressure relief protection range of upper protective seam mining

This paper analyzes the control mechanism of coal and gas outbursts and proposes the concept of an effective pressure relief protection range, based on the stress relief of the underlying coal-rock mass and the development of a plastic zone. Also this study developed a stress change and fracture development model of the underlying coal-rock mass. In addition, the stress and depth of fracture of any point in the floor were deduced with the application of Maple Calculation Software. The specific engineering parameters of the Pingdingshan No. 12 colliery were applied to determine the relationship between the depth of fracture in the floor and the mining height. The pressure-relief principle of the underlying coal-rock mass was analyzed while varying the mining height of the upper protective seam. The findings indicate that as the depth of fracture in the floor increases, the underlying coal-rock mass experiences a limited amount of pressure relief, and the pressure relief protection range becomes narrower.Additionally, the stress distribution evolves from a ‘‘U" shape into a ‘‘V" shape. A 2.0 m mining height of protective seam situates the outburst-prone seam, Ji_(15), within the effective pressure relief protection range. The fracture development and stress-relief ratio rises to 88%, ensuring the pressure-relief effect as well as economic benefits. The measurement data show that: after mining the upper protective seam, the gas pressure of Ji_(15) dropped from 1.78 to 0.35 MPa, demonstrating agreement between the engineering application and the theoretical calculation.

An analysis on the effect of mining height and floor lithology on pressure relief of upper protective layers

In order to understand the effect of mining height and floor lithology at the upper protective layer face on the pressure relief of protected coal seams, this paper uses a numerical simulation method to model the pressure changes at protected coal seam during mining upper protective layer. The results show that the taller the mining height at the upper protective layer face, the greater the protection on protected coal seam due to the higher level of pressure release; the upper protective layer face with hard rock floor impedes the pressure release at the protected coal seam, which affects the overall effect of the pressure release at protected coal seam using the protective layer mining method.

The antipyretic effects of Chai Ge fever relief oral liquid

Backgroud:To verify the antipyretic effect and mechanism of Chai Ge fever relief oral liquid,and to provide evidence for the clinical application of Chai Ge fever relief oral liquid.Methods:By designing three groups of experimental models of yeast-induced rat fever model,endotoxin-induced rabbit fever model,and para-influenza virus-induced rabbit fever model,the antipyretic effect and mechanism of Chai Ge fever relief oral liquid were studied by measuring body temperature before and after treatment and the expressions of protein kinase A(PKA),protein kinase C,arginine vasopressin(AVP),prostaglandin E2 and cyclic adenosine monophosphate(cAMP)in hypothalamus after administration.Results:In the yeast-induced fever model of rats,the body temperature and PKA expression levels in different dose groups of Chai Ge fever relief oral liquid were significantly different from those of the model group 1–3 h after treatment.In the rabbit fever model induced by endotoxin,different dosage groups of Chai Ge fever relief oral liquid have obvious antipyretic effect on 1–3 h after the model is established,and can significantly reduce the expression of AVP and cAMP in hypothalamus.In the para-influenza virus-induced rabbit fever model,each dose group of Chai Ge fever relief oral liquid has obvious antipyretic effect on 1–2 h after the model is established.Conclusion:Chai Ge fever relief oral liquid has good antipyretic effect on fever models induced by yeast,endotoxin and parainfluenza by regulating the expression of PKA,AVP,and cAMP.

Effects of Pre-Operative Single Dose Gabapentin on Postoperative Pain Following Total Abdominal Hysterectomy: A Dose Finding Study

Background & Aims: The multimodal analgesia provides superior pain relief and reduces opioid consumption and its side effects. Gabapentin has been used successfully in multi-modal analgesia in different doses. We designed a double-blind randomized control trial to find the minimal effective dose of gabapentin in multimodal analgesia for postoperative pain following total abdominal hysterectomy. Material & Methods: After informed consent, total of 87 patients were randomly assigned to A, B & C groups to receive gabapentin orally 300 mg, 600 mg, and 900 mg respectively one to two hours before surgery. Postoperatively pain was managed by patient-controlled analgesia (PCA) using pethidine. Pain score, opioid consumption, and side effects of gabapentin were monitored. Rescue analgesia was given and monitored. Results: There was no statistically significant difference among the groups with respect to age, weight, height, pethidine consumption, and rescue analgesia. Mean pain scores were statistically insignificant at baseline, 8, 12, and 24 hours postoperatively. Only at 4 hours, the highest pain score (mean) was found in group A, which is statistically significant. The side effects of gabapentin like nausea, vomiting, somnolence, and dizziness were also statistically insignificant. Conclusion: A single preoperative oral gabapentin 300 mg was found to be minimal effective dose in multimodal analgesic regimen for reducing post-operative pain and analgesic requirement following total abdominal hysterectomy.

Does Anyone Benefit？ - A Quantitative Effect Analysis on US Punitive Tariffs on Chinese PV Imports from a Global Perspective

Financial support from National Science Foundation for Distinguished Youth （Grant No.70925006）, National Natural Sciences Fund Program （Grant No.71103059）, Humanities and Social Sciences Youth Program of the Ministry of Education （Grant No. 10YJC7902930）, is gratefully acknowledged. Authors highly appreciate the comments of anonymous reviewers and take sole responsibility for this paper.

A Study on the Dynamic Adjustment of Pressure Relief Gas Drainage Drilling in Mined-Out Areas

With the development of coal mine equipment mechanization, the wide application of “hole instead of roadway” technology greatly reduces the cost of gas control engineering, but puts forward higher requirements for the effect of gas drainage. At present, the drainage effect of coal mine inspection boreholes is mainly evaluated by the drilling field, but the flow rate and gas concentration of each borehole in the drilling field are not the same, which causes the gas drainage effect not to be correctly mastered. In the present study, the pressure relief drilling in the goaf of the working face of a typical multi-coal seam group high gas outburst mining area was taken as the research object. Through the newly developed portable drilling inspection device, the pure amount of drilling drainage was investigated, and the drilling design was dynamically adjusted. The enhancement of the goaf pressure relief gas control effect ensures the gas safety of the mining face. At the same time, this improves the gas extraction rate and reduces the emission of greenhouse gases. If the data from the borehole investigation can be transmitted in real time and analyzed in big data, the optimal extraction negative pressure can be predicted through a regression algorithm. Under the control of the negative pressure of each borehole by the actuator, the extraction system can have the function of intelligent judgment.

地面井分层卸压的煤系气合采原理及方式探讨

为了进一步认识制约煤系气合采的因素,提高煤系合层排采各产层的产气贡献,分别从动力、通道和气源条件出发,分析了煤系气合采的必备因素。基于改变地应力状态提高储层导流能力以及分层改变储层流体压力,满足多层合采动力条件的原理,提出了地面井分层卸压的煤系气合采方式。该方式通过在地面进行定向钻井,在目标储层中进行高压水射流作业,人工创造卸压空间(缝、槽、穴等),改变地应力状态,降低有效应力伤害,增加储层导流通道的数量和开度,提高目标储层压降传递速率。待储层压力降至符合煤系气合采动力条件时进行合层排采,从而提高煤系合采各产气层的产气贡献。相较于常规增产改造措施,此方式能够减少煤系气储层在有效应力作用下的储层伤害,且有助于提高储层压降传递效率,增强煤系气的解吸和扩散,降低多层煤系气合采过程中的层间干扰。在以上研究基础上,认为地面井分层卸压的合采方式主要适用于储层地应力大、产层间距小的煤系气储层,且有望在薄互层煤系气储层增产改造及层间干扰严重的叠合共生煤系储层开发领域进行应用推广。

爆炸冲击波作用下立井防爆门及风机叶片动态响应特性

研究爆炸冲击波作用下立井防爆门及风机叶片动态响应特性,保证主要通风机连续、安全、可靠运转对保障矿井安全生产意义重大。根据相似理论设计搭建了小尺寸风井-风机-防爆门爆炸传播实验系统,开展了瓦斯爆炸冲击波传播实验,通过实验结果与数值模拟结果对比,验证了瓦斯爆炸冲击波传播数学模型的可靠性;利用分段接力模拟方法结合编写的描述防爆门运动过程udf代码,模拟了羊场湾矿Ⅱ020611回风巷掘进工作面发生瓦斯爆炸时冲击波传播过程,研究了冲击波作用下立井防爆门及风机叶片动态响应特性。研究表明:①冲击波作用下,初期防爆门上远风硐侧超压高于近风硐侧,而后出现高超压区由远风硐侧向近风硐侧移动现象,在超压未达到最大值之前防爆门上超压已分布均匀。②受冲击载荷作用,沿叶片径向方向出现不同的高压区,沿叶片的轴向方向,由叶片边缘向叶片中央超压逐渐增大。冲击波作用下叶片根部弯矩骤然增加至最高值又迅速降低,瓦斯爆炸当量越大,衰减越快。冲击波超压对叶片根部产生弯矩最大值与瓦斯爆炸当量呈对数关系。③对于叶片根部弯矩峰值,防爆门关闭时最大,防爆门被动开启次之,防爆门主动开启时最小。防爆门被动开启时,瓦斯爆炸当量越大,防爆门开启后泄压效果越差,配重对防爆门开启后泄压效果影响有限;相比于被动开启,防爆门主动提前开启可大幅度提高风机处的泄压效果,提高风机在灾变条件下的生存能力。

磨砂射流轴向切顶压裂工艺研发及应用

厚硬顶板大面积悬顶是诱发冲击地压的重要原因之一,针对顶板深孔爆破和常规水力压裂存在的不足,开发了磨砂射流轴向切顶技术。该技术通过在巷道顶板钻孔内实施预制轴向裂缝、定向水力压裂等工序,使巷道走向和倾向方向上均形成最有利于顶板垮落的人造裂缝网,以实现最佳卸压效果。现场应用表明,实施磨砂射流轴向切顶后,目标岩层电磁波吸收系数增强,顶板裂隙明显增加;工作面回采期间,压裂影响区域的支架支撑力在增加,支架主要受力模式从降阻型和恒阻型转变为增阻型,微震能量释放更平稳,有效降低了冲击地压发生风险。在此基础上,分析了磨砂射流轴向切顶卸压防冲机理,即轴向切顶使工作面端头附近形成预制的轴向裂缝,工作面回采期间,顶板沿预制裂缝定向切落,降低了顶板弯曲弹性能转化为巷道围岩压缩弹性能的基础静载Ej和顶板突然断裂产生的强烈附加动载Ed,使巷道围岩不具备冲击启动的载荷条件。

血液透析联合解毒泄浊方治疗慢性肾功能衰竭的临床效果分析

目的分析临床上血液透析联合解毒泄浊方治疗慢性肾功能衰竭的效果。方法选择2022年1月—2023年3月本院收治的120例慢性肾功能衰竭患者为研究对象,随机将其分为观察组和对照组,每组60例。对照组接受血液透析治疗,观察组在对照组的基础上进行解毒泄浊方治疗。3个月后观察两组患者的临床效果、炎症因子及肾功能指标改善情况。结果观察组治疗有效率高于对照组(P<0.05)。治疗后,观察组各项炎症因子(IL-6、CRP、TNF-ɑ)水平均明显低于对照组(P<0.05);观察组Cr、BUN水平明显低于对照组,CCR水平明显高于对照组(P<0.05)。结论血液透析联合解毒泄浊方治疗慢性肾功能衰竭效果显著,安全可靠,值得推广使用。

孤岛工作面长水平深孔全长水力压裂卸压机理及多参量效果分析

为了解决深井孤岛工作面回采巷道面临的强动压问题,分析了孤岛工作面存在的工作面侧向采空区顶板悬顶、后方采空区侧顶板悬顶以及上部高位岩层结构悬顶3种类型,对深孔压裂类型进行了分析,提出了基于长水平孔的全长水力压裂布置方式,在某矿3203孤岛工作面进行了应用;通过在不同层位的目标岩层施工长水平孔压裂,实现了对于孤岛工作面强动压巷道卸压的全长处理。分别在采场和巷道进行矿压观测并选取评价指标,通过多参量、分阶段的分析,可以发现:这种卸压方式能在顶板构筑弱化条带,达到改善本工作面端头和采空区上方顶板空间结构形态、缩短工作面周期来压步距、降低工作面超前支承应力峰值的作用,从时间和空间上优化工作面超前区域应力场的分布状态,转移煤柱与巷道围岩的高应力,减小采动应力的影响,显著降低回采期间的巷道变形量,实现孤岛工作面的安全高效回采。

机械扩孔煤体增透应力变化规律研究

机械扩孔作为一种新型煤层卸压增透强化措施,可广泛适用于低透气性瓦斯煤层。为了探究机械扩孔应力演化规律,通过理论分析,揭示机械扩孔应力分布特征,以车集煤矿2616煤层为研究背景,借助ABAQUS数值模拟软件分析扩孔过程中煤层应力演化规律。结果表明:机械扩孔后孔洞周围煤体应力场存在动态演化过程,由内向外呈圆环状分布,依次为破碎区、塑性区、弹性区和原始应力区;机械扩孔过程中造穴阶段应力扰动范围和应力集中情况都显著大于钻进阶段。

深部强矿压矿井煤层覆岩爆破卸压机理研究

为实现深部矿井开采强矿压的高效治理,本文提出首先在煤层覆岩顶板布置“U”型巷道,然后对“U”型巷道中间的岩层进行集中爆破卸压的强矿压治理方案。以西北矿区某深部强矿压矿井为研究背景,在两种岩性的坚硬顶板中,各设计了两种不同埋深的“U”型巷道布置方案,分别是埋深-800 m、-825 m和埋深-850 m、-875 m。研究结果表明,采用“U”型巷道岩层爆破后,煤层采动过程中的采场应力、位移均有所减小。而“U”型巷道爆破卸压效果不仅与相对层间距有关,还与“U”型巷道所在岩层的岩性有关。在岩层岩性相同的情况下,“U”型巷道与下煤层的相对层间距越小,采场爆破卸压效果越好。

超远距离下组煤层超前开采覆岩应力及裂隙演化规律研究

为探究平煤股份八矿超远距离下组煤层超前开采对上覆煤岩层的影响,采用相似材料模拟实验分析超远距离下组煤层超前开采上覆煤岩层裂隙及应力演化规律,并进行现场验证。研究结果表明:超远距离下组煤层超前开采条件下,随工作面推进,上覆煤岩层裂隙率呈先上升后平稳的趋势,当工作面从187 m推进至272 m,裂隙发育最快;超远距离下组煤层超前开采对上覆煤岩层有卸压效果,但与常规情况下相比卸压滞后距离较大;上覆岩层卸压比戊组煤层大;通过现场验证发现,随工作面推进,矿压呈先上升再下降后稳定的趋势,并将工作面区域分为未干扰区、应力集中区、卸压区和稳定区。研究结论可为平煤矿区远距离下组煤层超前开采、上组煤层工作面瓦斯防治和采区工作面采掘部署提供参考。

动压巷道水力压裂切顶卸压技术研究与应用

针对晋城矿区动压巷道多、服务周期长、服务期间受多次强烈采动影响等特点带来的围岩控制难题,以王坡煤矿典型动压巷道为工程背景,通过现场地应力与围岩强度实测,分析了复用巷道围岩变形破坏的原因,通过分析诱发巷道围岩变形的主要力源,揭示了水力压裂切顶卸压维护复用巷道围岩稳定的作用机理。利用理论计算确定了合理压裂层位高度及相关参数,制定了水力压裂卸压技术方案,并成功应用于井下试验。现场应用效果表明,水力压裂卸压技术有效缩短了工作面悬顶、降低周期来压步距,同时减小来压时动压系数;显著降低了支架所受顶板压力。压裂段巷道顶板移近量减少了55.7%,采动影响范围明显减小,水力压裂能够极大减小复用巷道围岩的收敛量与收敛速度的同时在远场上形成了应力缓冲区,缓解了复用巷道的高应力状态,起到了良好的卸压效果,维护了巷道围岩的相对稳定。

一对一全程导乐陪伴分娩配合镇痛对高龄产妇的效果分析

目的针对高龄产妇开展研究,评估一对一全程导乐陪伴配合镇痛的效果,为临床提供指导。方法选取2022年1月—2023年2月聊城市人民医院产房收治的66例高龄产妇。按护理方法差异分为对照组与观察组,各33例。对照组给予常规分娩护理,观察组给予一对一全程导乐陪伴分娩配合镇痛。比较2组产程时间、分娩疼痛、心理状态、分娩结局及满意度等。结果观察组各产程时间均短于对照组,差异有统计学意义(P<0.05);观察组各产程视觉模拟评分法(visual analogue scale,VAS)评分低于对照组,差异有统计学意义(P<0.05);干预后,观察组爱丁堡产后抑郁表(Edinburgh postnatal depression scale,EPDS)、分娩态度量表(childbirth attitudes questionnaire,CAQ)、焦虑量表(self-rating anxiety scale,SAS)评分低于对照组,差异有统计学意义(P<0.05);观察组产后出血、新生儿窒息、新生儿窘迫等总发生率为3.03%,低于对照组的24.24%,差异有统计学意义(P<0.05);观察组总满意度为100%,高于对照组的81.82%,差异有统计学意义(P<0.05)。结论对高龄产妇施以一对一全程导乐陪伴分娩配合镇痛可获得较好的效果,利于创建轻松且舒适分娩环境,最大程度缓解分娩疼痛,促进产程进展,优化分娩结局。

城市自然式滨水空间的水声环境对人压力恢复的影响研究

城市滨水空间作为城市生态和休闲的重要组成部分,在心理健康和生理恢复中扮演着关键角色。该研究旨在探讨城市滨水空间中复杂的水声环境对人类压力恢复的生理效应,明确多样化水声环境对人体心率(HR)及皮肤电活动(EDA)的影响。通过实验对34名不同年龄、性别和职业背景的受试者进行研究,记录其在仿真多样性水声环境刺激前后的生理指标变化。研究发现,不同声学参数的水声对人的压力恢复产生了不同程度的影响。分析结果表明,城市滨水空间的声环境设计应综合考虑声景对人的客观影响以及人的主观感受,从而实现真正的人本化设计。研究结果为自然驳岸类型滨水空间的设计提供了科学指导,对于提升城市居民的生活质量和促进生态环境的和谐发展具有现实意义。

高压氢气下橡胶密封圈的密封性能研究进展

综述高压氢气下橡胶密封圈的密封性能研究进展,重点介绍氢气在橡胶中的渗透性能和高压氢气下橡胶密封圈密封失效的影响因素以及高压氢气下橡胶密封圈的密封性能分析方法。氢气在橡胶中的渗透性能影响因素为填料种类、氢气压力、橡胶种类,高压氢气下橡胶密封圈密封失效的影响因素主要为泄爆效应和体积膨胀,高压氢气下橡胶密封圈的密封性能分析方法主要包括原位可视化分析和有限元分析。高压氢气密封用橡胶密封圈未来的研究方向是扩展填料和橡胶种类,开发系统性研究和测试设备。

煤层群保护层卸压强化抽采应力—渗流规律研究

为研究煤层群保护层开采及瓦斯抽采影响下的煤层瓦斯运移规律,构建了开采扰动影响下的煤体、岩体渗透率模型,并通过试验进行验证。结合张集煤矿地质条件,运用多物理场耦合模拟软件COMSOL,模拟得到煤层群保护层开采期间采场的卸压增透规律、瓦斯运移规律,以及钻孔不同抽采时间的采场瓦斯含量变化。研究结果表明,8煤作为保护层开采,随着工作面的推进,被保护层卸压范围和卸压程度逐渐增大,4煤层、6煤层最大应力卸压程度分别为27.8%、42.6%,对于6煤层的卸压效果最好;随着工作面推进,采区的瓦斯渗流场范围和渗流速度均增大,瓦斯向8煤层采空区方向涌出;通过保护层开采卸压结合穿层钻孔抽采,提高了瓦斯抽采效率,降低了煤层瓦斯含量,有效降低了煤与瓦斯突出危险性。

机械扩孔有效抽采半径数值模拟及现场应用

为研究掘进工作面机械扩孔的卸压增透效果,以扩孔后的抽采有效影响半径为考察指标,借助COMSOL-Multiphysics数值模拟软件建立机械扩孔模型,动态分析机械扩孔后的瓦斯流场,拟合得出扩孔有效影响半径与抽采时间的关系曲线;通过理论分析和现场考察试验,类比同等工况条件下机械扩孔与普通钻孔的预抽效果,定量探讨2种施工工艺条件下瓦斯流量衰减系数。研究表明,机械扩孔的瓦斯抽采流量平均值为0.0222 m^(3)/min,最低瓦斯抽采流量是初始抽采流量的56.9%,下降幅度为43.1%;而普通钻孔的瓦斯抽采流量平均值为0.006826 m^(3)/min,最低瓦斯抽采流量是初始抽采流量的22.6%,下降幅度达77.4%。机械扩孔抽采浓度由72%降到38%,降幅为47.2%,普通钻孔抽采浓度由39%降到17%,降幅达56.4%,说明机械扩孔卸压增透效果显著。