高应力破裂岩体条件下取消喷射混凝土支护的研究

通过对小官庄铁矿二采区进路和联巷围岩锚喷网支护的现场调查,发现由于其巷道围岩地压大、岩体破碎以及受采动影响,巷道围岩的变形、破坏严重。从理论上分析了喷射混凝土破坏的机理以及喷射混凝土存在的问题,进而确定了采用锚网支护的可行性。为此,取消喷射混凝土支护,对巷道的支护形式进行了重新设计,采用高强预应力锚网支护。现场试验发现,锚网支护效果明显,能满足生产需要,经济效益和社会效益显著。     

The erosion and abrasion characteristics of alumina coatings plasma sprayed under different spraying conditions

A series of plasma sprayed alumina coatings was evaluated regarding their erosion and abrasion characteristics. The coatings were deposited under different spraying conditions, using a commercial axial injection plasma spray system, and with powders of different grit sizes and crystallinity. A sintered bulk alumina and a conventionally sprayed coating, produced by a radial injection air plasma spray technique, were tested as reference materials. To evaluate the importance of energy input the coatings were produced using two different torch nozzle sizes and gas mixtures with a varied amount of hydrogen. The erosion and abrasion results indicate that hydrogen concentration, nozzle size and precursor powder type and size influence the tribological characteristics of the coatings. The wear resistance of the coatings seems to benefit from an increase in hydrogen concentration or torch nozzle size. The effect of precursor powder size on the wear resistance was more complex but indicates that sapphire powders of medium precursor sizes are advantageous to ordinary plasma spraying powders of alumina.     

人工砂石粉含量对喷射混凝土性能影响分析

本文研究了不同强度等级下,人工砂石粉含量和胶凝材料用量对喷射混凝土工作性和强度的影响,通过Design—Expert软件建立相关模型,并采用响应曲面法进行量化分析。研究结果表明：当人工砂的MB值〈1．4时,对于C20喷射混凝土,人工砂石粉含量宜控制在15％以内;对于C25～C30喷射混凝土,人工砂中石粉含量宜控制在12％以内;采用二次方程模型能较好地表征人工砂喷射混凝土回弹率与石粉含量、胶凝材料用量之间的关系。     

纳米SiO2对火焰喷涂HDPE涂层热力学性能的影响

利用电子拉力机、红外光谱仪(FTIR)、透射偏光显微镜(POM)和差示扫描量热仪(DSC)等研究了纳米SiO2(n-SiO2)对火焰喷涂HDPE涂层力学及热性能的影响.红外光谱和XRD分析表明,HDPE及HDPFJ/n-SiO2粉末在喷涂的过程中没有发生氧化或降解作用,表明火焰喷涂法适合制备HDPE及HDPE/n-SiO2复合涂层.DSC分析表明,n-SiO2具有异相成核作用,当n-SiO2用量为1.0%时,复合涂层的过冷度由10.92℃下降为10.73℃.     

热喷涂层强度与厚度关系的实验研究

试验研究了不同热喷涂材料涂层强度与厚度的关系，指出热喷涂层是扁平粒子的积层组织，这些粒子在碰撞凝固的过程中，由于不均匀收缩的原因，会产生残余应力，随厚度和积层粒子数的增加，残余应力会叠加。如果涂层没有足够的塑性，残余应力会导致涂层，强度逐渐减小     

Low-volume wet-process sprayed concrete: hardened properties

This paper, which reports on part of a 3-year research project into wet-process sprayed mortars and concretes for repair, investigates the hardened performance of wet-process sprayed fine concretes. It follows on from an earlier paper by the authors on the performance of hardened wet-process sprayed mortars and some comparisons with these are made here (Austin SA, Robins PJ, Goodier CI (2000). Magz Concr Res 52:195–208). Work has also been completed by the authors on the pumping and rheology of the fine concrete mixes presented here (Austin SA, Goodier, CI, Robins PJ (2005). Mater Struc, RILEM 38:229–237). Nine laboratory-designed fine concretes were pumped and sprayed through a wet-process piston pump and one through a dry-process pump. The properties measured included compressive and flexural strength, tensile bond strength, hardened density, elastic modulus, sorptivity and drying and restrained shrinkage. In situ test specimens were extracted from 500 × 500 × 100 mm deep sprayed panels. Hardened property tests were also conducted on corresponding cast specimens and, where possible, on specimens that had been sprayed directly into a cube or beam mould. The compressive strengths of the cast cubes, although very similar, were usually slightly greater than the in␣situ cubes, the opposite of what was found for wet-sprayed mortars (Austin SA, Robins PJ, Goodier CI (2000). Magz Concr Res 52:195–208). Inconsistent results for compressive and flexural strengths obtained from spraying directly into a steel mould suggest that this method is not as reliable when using a piston pump as it is when using a low-output worm pump (Austin SA, Robins PJ, Goodier CI (2000). Magz Concr Res 52:195–208). The bond strength of all the mixes exceeded 2.1 MPa at 7 days. The values for modulus of elasticity, when compared with the compressive strength, were similar to published data for this relationship. The sorptivity values showed only a slight relationship with the compressive strength. The mixes exhibited a wide range of drying shrinkage, but the data from the restrained specimens suggest an actual repair is influenced as much by ambient conditions as it is by the mix proportions.     

Windows with heat mirrors for energy conservation

Detailed calculations have shown that radiation heat losses through double-pane windows can be substantially reduced by the application of a thin, transparent film, reflective to long-wave radiation (‘heat mirror’). The comparative analysis of different types of ‘heat mirror’ has been carried out, and a tin oxide layer deposited by spray has been recognized as the most suitable for large-scale production. A tin oxide film has been deposited on glass by a spray method using ordinary commercial materials for the substrate, the solvent and the solution. The optical properties of the tin oxide films obtained have been compared with those measured on films deposited by more sophisticated methods; results are as follows: in comparison with vacuum-deposited metallic films or vacuum-deposited SnOx, films, our sprayed SnOx, films have similar or better transmissivity for visible spectra and somewhat (10–30 per cent) lower reflectivity for the infrared portion of the spectrum, but at the same time the prices of material and/or production costs are several orders of magnitude lower.     

喷射混凝土速凝剂的应用与发展

速凝剂是一种非常重要的混凝土外加剂。本文论述了喷射混凝土速凝剂应用和国内外速凝剂的研究发展现状。分析了现有速凝剂存在的主要问题．提出了今后速凝剂的发展趋势。     

梅山铁矿井下渗漏水防治技术

针对梅山铁矿井下防渗漏水对生产安全造成的隐患治理问题,在分析梅山铁矿水文地质条件及矿山开采现状的基础上,开展了井下防渗漏水综合治理技术方案研究与应用。通过现场调查分析了矿山井下渗漏水现状,研究表明地质构造、矿物成分及人为开挖活动是导致部分揭露矿岩在遇水后稳定性下降的主要原因。基于崩落法开采造成地表塌陷,分析了暴雨入渗的特征,并采用水均衡法获得暴雨日入渗率为8%,实现了井下涌水量预测。将井下渗漏水情况分为采区渗水与井筒渗水2种类型。通过综合比较分析,副井、西南井、北风井采用帷幕注浆方案。1#主井采用局部注浆方案;将巷道渗漏水现象细分为顶板淋水、底板及其墙角渗水、巷道墙体预留孔渗水、大面积巷道淋水、渗漏水和围岩中存在异常水包5类,并提出了相应的治理措施。以上方案在梅山铁矿的实施取得了显著效果。     

激光重熔合成AlCo_(x)CrFeNiCu高熵合金涂层组织与耐腐蚀性能北大核心

为了提高机械零部件的腐蚀性能,采用冷喷涂辅助激光重熔合成不同Co含量AlCo_(x)CrFeNiCu(x=0、0.5、1、1.5、2)高熵合金涂层。通过XRD、SEM、EDS、TEM、电化学测试系统等设备检测分析了Co含量的变化对合金涂层相结构、显微组织、耐腐蚀性能的影响。结果表明,激光重熔合成AlCo_(x)CrFeNiCu高熵合金涂层是由简单的BCC和FCC相构成,当x=1时高熵合金涂层的晶格畸变最大,随着Co含量的增加,激光重熔合成AlCo_(x)CrFeNiCu高熵合金涂层的等轴树枝晶由少变多并逐渐细化,柱状树枝晶的间距先增大后减小。在3.5%NaCl腐蚀介质中,当x=0.5时高熵合金涂层中Cu元素轻微偏析,有少量点蚀发生,AlCo_(0.5)CrFeNiCu高熵合金涂层自腐蚀电位最正,腐蚀电流密度达到最小,腐蚀速率2.28×10^(-3)mm/a,表现出良好耐腐蚀性。