共查询到20条相似文献，搜索用时 390 毫秒
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高速公路隧道下伏小煤窑采空区对衬砌结构稳定影响较大,给隧道施工带来较大风险与潜在危害,按现行技术细则要求对下伏采空区处治范围大、费用高、施工难。笔者以鱼洞Ⅰ号隧道为实例,根据下伏小煤窑采空区规模和特点提出隧道开挖后洞内注浆进行处治措施,通过洞内物探、钻探等手段探明采空区具体位置,采用数值模拟对洞内注浆处治效果进行分析,通过工程实践保证了隧道施工及结构安全。结果表明:隧道下伏采空区对隧道围岩及衬砌结构稳定性影响较大,使得隧道围岩及支护结构最大竖向位移分别达到-0.223 8 m和+0.312 2 m,隧道底板与采空区顶板之间的围岩大部分处于塑性变形状态;现行隧道下伏采空区稳定性评价及处治范围偏于保守,地表注浆处治费用高、难度大;隧道洞内注浆处治下伏小煤窑采空区具有较好效果,隧道结构变形处于可接受范围,可保证隧道施工及结构安全。对于无序开采、资料匮乏、回采率低等隧道下伏小煤窑采空区,采取洞内注浆措施进行处治,可显著减小采空区处治费用及施工难度,为类似工程建设提供参考和借鉴。 相似文献
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矿山经过多年开采留下许多采空区,存在着极大的安全隐惠,所以我们应该对它们进行安全监测.本文介绍了三种常见空区稳定性监测技术:电测法、光测法、声测法. 相似文献
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李本贵 《中南林业科技大学学报(自然科学版)》2006,26(3):78-81
研究了热压过程中内应力的形成机理和板材内部应力状态,探讨了内应力释放对刨花板尺寸稳定性的影响,提出了减小内应力和提高尺寸稳定性的工艺措施.刨花板会发生变形,即尺寸不稳定,源于以下两个基本原因:(1)构成刨花板主体单元的木材有吸湿性;(2)刨花板在热压过程中产生了内应力即残余应力.刨花板内应力释放时,人们可以实实在在地感觉到,例如:刨花板热压结束后,卸板时板坯内会传出嘣、嘣、嘣的声音,或者是规整而无变形的刨花板在开料后会发现有翘曲变形出现.这就是残存在刨花板内部的应力在释放.本文根据木材传热传质的理论、应力松驰理论、相平衡理论对刨花板内应力形成机理和应力状态及内应力释放对刨花板尺寸稳定性的影响进行分析和研究,为生产提供理论指导. 相似文献
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《技术与市场》2014,(2)
目前,我国对上层煤柱下综放沿空回采巷道的矿压显现规律的研究还不够深入,不能有效地对下层煤开采时的围岩变形进行控制,严重制约了工作面安全高效生产,因此加强对上层煤柱下综放沿空回采巷道的矿压规律的探究十分必要。通过对汾矿集团某矿8902综放工作面的开采条件和地质条件的研究,并对上层煤柱下综放沿空回采巷道的矿压进行了现场观测,利用FLAC数值模拟计算对回采巷道应力分布和塑性区发育情况进行了分析。研究结果表明,上层煤柱与下层煤综放回采影响下引起沿空回采巷道的引力重新分布,导致回风巷道顶底和两帮发生很大的变形,有时移动量可达2 m,使回风巷局部断面不足2 m,对工作面的生产造成了严重不良影响。根据上层煤柱下综放沿空回采巷道的矿压显现规律,采取合理的措施(如减少区段煤柱宽度及合理布置回采巷道等),从而控制围岩变形和维护巷道的稳定。 相似文献
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厚层基材喷射植被护坡技术中锚杆力学行为分析与研究 总被引：1，自引：0，他引：1
锚杆是将铁丝格栅和绿化基材混合物固定在坡面岩体上,且埋入岩体深处的受拉构件。锚杆、铁丝格栅与岩体共同承担外荷载、基材混合物层的自重应力等,岩体结构类型、边坡高度及坡比不同,锚杆的锚固深度和间距亦不相同。本文以安楚高速公路不同坡比的石灰岩深层稳定岩石边坡厚层基材喷射植被护坡技术为切入点,通过建立静力平衡方程以及锚杆的抗拉抗拔稳定性验算,对锚杆受力进行分析计算,找出影响锚杆的锚固深度和间距的具体因素,并算出锚杆最佳锚固深度和最佳间距的表达式。 相似文献
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盐胁迫对木槿属两个外来种质生长及叶绿素含量影响 总被引：1，自引：0，他引：1
采用盆栽试验,研究了不同质量分数的NaCl胁迫对木槿属两个新引进植物Hibiscus‘Moy grande’、H.dasycalyx高生长、干物质量、根冠比及叶绿素含量变化等指标的影响。结果表明:4 g/kg盐处理水平时,两种材料的高生长量均与对照无显著差异,H.‘Moy grande’的干物质量积累较对照略有下降,H.dasycalyx干物质量积累则受到显著抑制(P﹤0.05);根冠比测定数据表明盐胁迫对两种材料地上部分的生长抑制强于对根系生长的抑制;盐胁迫下两种材料叶绿素a、叶绿素b含量变化趋势与单位质量叶片叶绿素含量的变化相似,均有不同程度的升高。生长指标分析结果表明H.‘Moy grande’对NaCl胁迫的抗性强于H.dasycalyx。 相似文献
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【目的】揭示北高丛越橘对干旱胁迫的响应机制并筛选出耐旱性较强的越橘品种。【方法】以11个北高丛越橘品种1年生扦插苗为试材,分别为‘蓝丰’‘瑞卡’‘双迪’‘斯巴坦’‘卡拉’‘伊丽莎白’‘钱德勒’‘布里吉塔’‘公爵’‘甜心’‘埃利奥特’,研究干旱胁迫对光合生理特性的影响,并评价不同品种的抗旱性。【结果】干旱胁迫20 d后,北高丛越橘品种脯氨酸含量、丙二醛含量、过氧化氢酶活性、胞间CO_2浓度均显著升高,而净光合速率、蒸腾速率、气孔导度、光系统Ⅱ实际光量子产量和电子传递速率均显著降低。通过主成分分析,将16项生理生化指标转化为3个互相独立的综合指标,累计贡献率达85.74%。主成分1主要反映叶片生理特性、抗氧化酶活性及主要的叶片荧光参数等信息,主成分2主要反映叶片气孔功能信息,主成分3主要反映叶片光合作用相关信息。通过聚类分析,将11个北高丛越橘品种划分为3个类型:‘甜心’‘公爵’和‘蓝丰’为抗旱型,‘布里吉塔’‘伊丽莎白’‘瑞卡’和‘埃利奥特’为中间型,‘钱德勒’‘双迪’‘斯巴坦’和‘卡拉’为不抗旱型。根据抗旱性综合评价值,11个北高丛越橘品种按照抗旱性由高到低排序依次为‘甜心’‘公爵’‘蓝丰’‘布里吉塔’‘伊丽莎白’‘瑞卡’‘埃利奥特’‘卡拉’‘斯巴坦’‘双迪’‘钱德勒’。【结论】采用主成分分析、隶属函数法、聚类分析等相结合的方法对北高丛越橘苗期耐干旱胁迫能力进行评估,可以较好地揭示性状指标与耐干旱胁迫能力的关系。11个北高丛蓝莓品种中‘甜心’‘公爵’和‘蓝丰’耐干旱胁迫能力较强。 相似文献
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We examined relationships between stable isotopes of carbon (delta(13)C) and oxygen (delta(18)O) in tree rings of Callitris columellaris F. Muell in the semi-arid Pilbara region of north-western Australia. To test the hypothesis that stomatal control of photosynthesis decreases during drier periods, we developed delta(13)C and delta(18)O chronologies spanning 1919-1999, and used a permutation regression approach to relate a 21-year running correlation between delta(13)C and delta(18)O to rainfall and temperature at Marble Bar and our study site. The relationship between delta(13)C and delta(18)O switched from being always negative before 1955 to being consistently positive after 1976, suggesting an increase in stomatal control of photosynthesis in recent decades. Changes in the delta(13)C-delta(18)O relationship reflected changes in rainfall, which has increased in the region by 30% since 1976. The correlation between delta(13)C and delta(18)O was positively related to the 21-year running mean of normalized rainfall anomalies at both the study site (P = 0.045, Adj. r(2) = 0.47) and Marble Bar (P = 0.046, Adj. r(2) = 0.48). In addition, the delta(13)C-delta(18)O correlation was negatively related (P = 0.047, Adj. r(2) = 0.61) to temperatures at Marble Bar. Our interpretation of the role of changes in climate affecting the relationship between tree-ring delta(13)C and delta(18)O is supported by evidence from the isotope composition of foliage samples: foliar delta(13)C and delta(18)O were negatively correlated with log stomatal conductance (delta(13)C, r = -0.41; delta(18)O, r = -0.42), whereas the correlation between foliar delta(13)C and delta(18)O was positive (r = 0.63, P = 0.027) after the summer wet period. Our data indicate that stomatal control of photosynthesis in Callitris adjusts to region-wide changes in climate and that, in a warmer and drier world, trees might adapt by increasing non-stomatal control of photosynthesis. 相似文献
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The effect of moisture content on the stress wave propagation velocity was investigated in order to estimate the Young’s modulus of full-scale timbers in an air-drying state using the measurement of stress wave propagation velocity above the fiber saturation point. Using Japanese cedar lumber, the velocity and the density under high-moisture condition and air-drying states were measured respectively; after measuring the modulus of elasticity in an air-drying state, the moisture content of each condition was measured. By performing numerical analysis on these data, the relationship between the moisture content and the rate of change of velocity of full-scale timbers was derived. This relationship was used to estimate the Young’s modulus of the timber in the air-drying state from the velocity in high-moisture condition. First, the velocity and the Young’s modulus in an air-drying state were estimated accurately from its density, moisture content and velocity under high-moisture condition. In cases where the density could not be measured, using the database of mechanical properties with the Monte Carlo simulation method, the Young’s modulus of the full-scale timber in an air-drying state might be estimated within 20% accuracy from its moisture content and velocity under high-moisture condition. 相似文献
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锚杆框架梁＋浆砌片石作为一种路堑高边坡防护加固技术，主要适用于高陡岩石、地质条件复杂地段边坡，特别是针对岩石极易风化、崩解、滑动的特征边坡，能有效地保证边坡的稳定性，且结构布置合理。 相似文献
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A. Miksic M. Myntti J. Koivisto L. Salminen M. Alava 《Wood Science and Technology》2013,47(6):1117-1133
The mechanics of fresh wood with and without a fatigue pre-treatment that mimics a mechanical pulping process was experimentally studied. The mechanical properties of Norway spruce samples under compression are considered with the macroscopic stress–strain data and from local strain properties via digital image correlation technique. The results highlight the effects of the orientation of the wood annual rings compared to the loading direction and of the pre-fatigue. The wood presents a low yield point when the annual rings are tilted compared to the load axis, but the Young’s modulus and yield stress are higher when the annual rings are either parallel or perpendicular to the load direction. In the last case, buckling of softest layers occurs. The fatigue treatment makes the wood less stiff as deduced from the decreases of Young’s modulus and yield stress, whatever the orientation of annual rings. Secondly, it creates a thin and localized softened layer. 相似文献
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以焦作中马矿区矸石山对生态环境的破坏为例,借鉴了国内外对煤矸石资源综合利用的实践经验和成果。在介绍中马矿区矸石山的立地情况和社会经济属性的基础上,分析了针对目标矿区煤矸石资源化利用的技术和途径,并探讨了我国煤矿区煤矸石资源化的前景。 相似文献
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Marcin Pietrzykowski 《林业研究》2014,25(1):63-74
In Central Europe,a large portion of post-mining sites were afforested with Scots pine,which is characterized by good adaptability and a tolerance for poor habitat at the beginning of forest ecosystem development.Conversion of monoculture on mine sites into more biodiverse mixed hardwood forests,especially on more fertile deposits,can be an emerging need in this part of Europe in next decades.The ability to classify the forests at these post-mining sites will facilitate proper species selection as well as the management and formation of the developed ecosystem’s stability.This work describes the guidelines that can be followed to assess reclaimed mine soil(RMS)quality,using the mine soil quality index(MSQI)and a classification of developed forest sites as a basis of tree-stand species selection and conversion of pine monocultures.The research was conducted on four post-mining facilities(lignite,hard coal,sulphur,and sand pit mining areas)on different RMS substrates dominant in Central Europe.Soil quality assessment takes into account the following features of the soil:texture soil nutrients(Ca,Mg,K,Na,P);acidity(pH KCl);and Corg-to-Nt ratio in the initial organic horizon.An analysis was conducted of classification systems using the MSQI validation correlation(at p=0.05)with vegetation features affected by succession:aboveground biomass of forest floor and ecological indicators of vascular plants(calculated on the basis of Ellenberg’s(2009)system).Eventually,in the analysed data set,the MSQI ranged from0.270 for soils on quaternary sands to 0.720 for a mix of quaternary loamy sands with neogene clays.Potential forest habitat types and the role of the pine in the next generation of tree stands on different RMS parent rock substrate were proposed. 相似文献