Microscopic properties and sealing performance of new gas drainage drilling sealing material

The geological condition of Chinese coal mines are complex and high gassy, which account for fifty percent to seventy percent. Because of the abundant pores and cracks around the drainage drilling hole, the gas concentration attenuates rapidly, and the effective gas drainage period is short. The traditional sealing materials of yellow mud and cement-sand grout will readily shrink after the drilling hole is sealed, the sealing length is short and the sealing quality is not satisfactory. Currently widely used polyurethane material will shrink when it comes into contact with water, and the price is also very high. In this study, taking cement as a base material, a novel composite sealing material mixed by expansion admixture, additive, and fibrin and coupling agent was developed and the sealing performance and expansion property of the material were also studied and analyzed. The FEI Quanta TM 250 environmental scanning electron microscope was used to investigate the microstructure of material. The results revealed that the new composite sealing material had a desirable expansion performance and a definite fluidity convenient for grouting. The solidified material, combining closely with the drilling wall, possessed an adequate strength and was not easy to shrink. Compared to the conventional polyurethane, the gas drainage concentration by drilling sealing exceeded 40 percent, and the sealing capacity improves 5 times, the sealing effect increases significantly.     

Experimental study on the mechanical properties and consolidation mechanism of microbial grouted backfill

Backfill mining technology is the practice of returning waste materials underground for both disposal and geotechnical stability, however, a challenge with current technologies is that they commonly require cement-based binders which have a relatively high environmental impact. Finding alternatives to cement-based binders can improve environmental performance and this paper proposes microbial grouted backfill (MGB) as a potential solution. In this paper, the effects of the cementation solution concentration (CSC), volume ratio of bacterial solution to cementation solution (VRBC), particle sizes of the aggregates, and the number of grouting batches on the mechanical properties of MGB are studied. The experimental results show that MGB strength increased, up to a peak value, as CSC was increased, before decreasing as CSC was increased further. The results also show that MGB strength increased, up to a peak value, as VRBC decreased, before decreasing as the VRBC was decreased further. The peak strength was achieved at a CSC of 2 mol/L and a VRBC of 1:9. The strength of the MGB also increased as the number of grouting batches increased. Graded MGB samples showed the highest UCS, 25.12 MPa, at particle sizes of 0.2 to 0.8 mm, while full (non-graded) MGB samples displayed mean UCS values ranging from 1.56 MPa when the maximum particle size was 0.2 mm, up to 13 MPa when the maximum particle size was 1.2 mm. MGB samples are consolidated by the calcium carbonate that is precipitated during microbial metabolism, and the strength of MGB increases linearly as calcium carbonate content increases. The calcium carbonate minerals produced in MGB materials are primarily calcite, with secondary amounts of vaterite.     

不同温度条件下水泥注浆液性能的实验研究

针对不同温度条件下水泥注浆施工,在实验室进行了各温度条件下,水灰比对水泥浆液凝结时间、黏度、结石率和析水率影响的实验研究,并对结石率和析水率进行相关性分析。结果表明,随温度升高,浆液的初凝、终凝时间都缩短,但缩短的幅度越来越低;低水灰比时,随温度升高黏度增大,水灰比达到一定高度时,温度对黏度的影响不明显;随温度升高,结石率增大,析水率降低。而随水灰比的增大,浆液性能向相反的方向发展。相关性分析表明结石率和析水率有高度显著的一元线性关系。     

钢桁架受力性能理论分析与试验研究

为使钢桁架结构能够安全、经济以及合理的应用在建筑工程中,本文从试验的方案、试验数据整理、内力的理论计算以及两组数据的对比等方面来探讨将焊接点看作为理想铰接点时,钢桁架结构受力性能的情况,以及其他因素对钢桁架结构受力性能的影响.     

瞬态法测量木材热物性的理论与实验研究

为了有效测量不同含水率木材的热物性，提出了一种新的瞬态平面热源测量法。在一定的简化条件下求解一维有限厚度平板的非稳态导热微分方程，得到了平板木材试样的温度随时间和平板厚度变化的短时间公式，并由此建立了在恒定热流加热条件下木材热物性的瞬态测量实验台。利用此实验台测量了不同含水率的落叶松和红松试样的径向导热系数、热扩散系数和比定压热容等热物性参数并与文献数据进行了比较。结果表明，该瞬态测量方法具有较高的精度，比准稳态法更好地满足了一维导热条件，利用此方法能够有效而快速地对不同含水率的木材进行热物性测量。     

工业型煤冷强度形成机理的实验研究

通过扫描电子显微镜对工业型煤的微观结构进行分析 ,发现工业型煤的冷强度是因粉煤颗粒间分布有凝胶体和各种形态的晶体而形成 ,其强度的大小则取决于形成的晶体在粉煤颗粒间是否形成网络、分布是否均匀、凝胶体包裹煤粒是否密实等因素     

Synthesis, properties and dispersion mechanism of sulphonated acetone-formaldehyde superplasticizer in cementitious system

The synthesis, properties and dispersion mechanism of sulphonated acetone-formaldehyde superplasticizer （SAF） were presented. This superplasticizer was synthesized by the reaction among acetone, formaldehyde, sodium sulfite and pyrosulfite. The structure and property were respectively characterized by IR and surface tension measurement. Performance of SAF in cement was evaluated by paste flow as well as heat calorimetry. The dispersion mechanism was identified via adsorption and zeta potential measurement. The results show that cement paste mixed with SAF shows good fluidity. SAF exerts little retarding effect on cement paste and it behaves like a typical polycondensate superplasticizer. The main dispersion mechanism of SAF is attributed to electrostatic repulsion.     

倾斜球磨机粉磨特点的探讨与实验研究

从理论和实验两方面研讨了倾斜轴球磨机的粉磨机理和性能特点。分析表明，倾斜轴球磨机中球料群的运动是一种空间三维运动，其运动强度比普通球磨机大，摩擦粉碎所占比例比冲击粉碎大，故粉磨效率提高，适宜于制备超细粉，通过石英，方解石两种试料在不同工况下的粉磨实验，分析倾斜轴球磨机的倾斜角，转速等工艺参数对粉磨效率的影响。该项研究为倾斜轴磨机的开发应用提供理论分析和实验依据。     

硫酸盐废水在ABR中的转化机理研究

为研究废水厌氧处理过程中硫酸盐的去除机理,以厌氧折流板反应器（ABR）为工艺,考察了低碳硫比时,不同负荷和水力停留时间（HRT）下硫酸盐的转化规律.试验结果表明：硫酸根在前部隔室被大量还原.随着硫酸盐浓度的增加以及HRT的缩短,硫酸根的还原逐渐向后推移,之后硫酸盐的转化趋于平缓,CODcr的去除也有类似规律.硫离子浓度在前部隔室迅速上升至最大值,在之后的隔室中上下小幅度波动.碱度和挥发性脂肪酸（VFA）先在前部隔室迅速增加,然后在后部隔室缓慢下降.     

Experimental study on rheological deformation and stress properties of limestone

The systematic experiment regarding the general uniaxial compression test and the creep deformations of the typical limestones from the surrounding rock of the highway tunnels were made.The relationship between the axial stress and the delayed deformation steady value was obtained from the creep tests under low loading stresses.By the least square method,the parameters of Nishihara creep model were calculated from the creep curves.The results indicate that the strain change always lags behind the increase o...     

Theoretical and experimental study of initial cracking mechanism of an expansive soil due to moisture-change

Swelling and shrinkage due to moisture-change is one of the characteristics of the expansive soil, which is similar to the behavior of most materials under thermal effect. If the deformation is restricted, stress in expansive soil is caused by the swell-shrinking. The stress is defined as “moisture-change stress” and is adopted to analyze swell-shrinkage deformation based on the elasticity mechanics theory. The state when the total stress becomes equal to the soil tensile strength is considered as the cracking criterion as moisture-change increases. Then, the initial cracking mechanism due to evaporation is revealed as follows: Different rates of moisture loss at different depths result in greater shrinkage deformation on the surface while there is smaller shrinkage deformation at the underlayer in expansive soil; cracks will grow when the nonuniform shrinkage deformation increases to a certain degree. A theoretical model is established, which may be used to calculate the stress caused by moisture-change. The depth of initial cracks growing is predicted by the proposed model in expansive soil. A series of laboratory tests are carried out by exposing expansive soil samples with different moisture-changes. The process of crack propagation is investigated by resistivity method. The test results show good consistency with the predicted results by the proposed theoretical model.     

碳纳米管在水性体系中的分散性能及机理

为了探求碳纳米管在水性体系中的有效分散方法及分散性能,以阿拉伯胶(GA)、曲拉通(Tx100)、十六烷基三甲基溴化铵(TB)、十二烷基磺酸钠(SDS)4种表面活性剂(SAA)为多壁碳纳米管(MWNTs)的分散剂,采用SAA超声分散法及酸处理法制备了11种分散液。结合静置离心法研究了不同种类SAA单掺的分散效果,结果表明:单掺GA对MWNTs分散效果最好,离心170 min后才开始分层。首次采用紫外分光光谱吸光度法评价了不同种类SAA复掺及SAA掺量变化对MWNTs分散性能的影响,测试结果表明:复掺Tx100与GA效果最好;当GA掺量为0.45 g/L时效果最好;比较二者分散效果后知:GA掺量为0.45g/L的悬浮液分散效果最佳。采用傅里叶红外光谱(FTIR)检测混酸氧化后MWNTs表面的基团,分析可知:经混酸处理后,MWNTs表面成功引入了羟基和羧基等官能团。     

LY12大型材生产工艺及性能研究

论述了LY12CZ大型生产中常出现的问题及工艺改进措施，并对最终产品进行了研究，使材料达到了技术条件要求。     

Theoretical and experimental analysis on the mechanism of the Kaiser effect of acoustic emission in brittle rocks

The Kaiser effect is formally described as the absence of detectable acoustic emission （AE） events until the load imposed on the material exceeds the previous applied level and is usually used to estimate geostress. By focusing on the heterogeneity of rock material, the mechanism of the Kaiser effect under cyclic loading is analyzed based on statistic damage mechanics. Two groups of granite specimens have been cyclically loaded with two different loading paths to verify the theoretical results. The heterogeneity of rock is the real reason that causes irrecoverable damage on the Kaiser effect of acoustic emission in cyclic loading. The Kaiser effect reflects the damaged state in rocks rather than the previous stress imposed on it. Applications for using the Kaiser effect to estimate geostress were discussed here. It is shown that the commonly used uniaxial loading method for estimating geostress is not in accor- dance with the theoretical and experimental results. The analysis is of importance to use the Kaiser effect correctly for estimating geostress or in other fields. 2008 University of Science and Technology Beijing. All rights reserved.     

Theoretical and experimental study of the thermal conductivity of nanoporous media

The nanoparticle thermal conductivity and nanoscale thermal contact resistance were investigated by molecular dynamics(MD) simulations to further understand nanoscale porous media thermal conductivity.Macroscale porous media thermal conductivity models were then revised for nanoporous media.The effective thermal conductivities of two packed beds with nanoscale nickel particles and a packed bed with microscale nickel particles were then measured using the Hot Disk.The measured results show that the nano/microscale porous media thermal conductivities were much less than the thermal conductivities of the solid particles.Comparison of the measured and calculated results shows that the revised combined parallel-series model and the revised Hsu-Cheng model can accurately predict the effective thermal conductivities of micro-and nanoparticle packed beds.     

可燃制冷剂爆炸极限及抑制的理论与实验研究

对影响可燃制冷剂爆炸极限的因素进行了讨论分析,指出仅凭测试的爆炸极限来确定可燃工质的爆炸范围是不可靠的,应考虑测试条件和安全系数。用具有阻燃作用的制冷剂与可燃制冷剂组成混合制冷剂抑制可燃制冷剂的可燃性,研制了可燃工质爆炸极限测试装置,对18种抑制后的混合制冷剂爆炸极限进行了实验研究。     

岩质边坡滑坡机理与稳定性研究

所研究的边坡为露天岩质边坡，已出现多次滑坡，根据对边坡岩体的物理力学性质测试，现场工程地质调查，现场动力学测试及滑体位移观测，提出了确定边坡潜在滑动面的计算模型，确定出了优势滑动面及破坏模式．通过极限平衡及有限元分析计算，给出了合理边坡角．针对现在的滑体和将来的潜在滑体，提出了相应的处理方案和预防措施。     

岩质边坡滑坡机理与稳定性研究

所研究的边坡为露天岩质边坡,已出现多次滑坡,根据对边坡岩体的物理力学性质测试,现场工程地质调查,现场动力学测试及滑体位移观测,提出了确定边坡潜在滑动面的计算模型,确定出了优势滑动面及破坏模式.通过极限平衡及有限元分析计算,给出了合理边坡角.针对现在的滑体和将来的潜在滑体,提出了相应的处理方案和预防措施.     

现代钢铁企业物流技术的理论研究

剖析我国钢铁企业物流技术的发展历程，详细分析了现代钢铁企业从原、燃料及辅助物料采购进厂到入炉冶炼、半成品向下一道工序流转，直至加工各种产品销售出厂整个生产过程中的物流特性及规律，得出吨钢厂外、厂内理论运输指标。     

Theoretical and experimental study on non-linear vibration characteristic of gear transmission system

In order to investigate the vibration of gear transmission system with clearance, a vibratory test-bed of the gear transmission system was designed. The non-linear dynamic model of the system was presented, with consideration of the effects of nonlinear dynamic gear mesh excitation, flexible rotors and bearings. Integration method was used to investigate the non-linear dynamic response of the system. The results imply that when the mesh frequency is near the natural frequency of gear pair, it is the first primary resonance, the bifurcation appears, and the vibration becomes to be chaotic motion rapidly. When the speed is close to the natural frequency of the first-order bending vibration, it is the second primary resonance, the periodic motion changes to chaos by period doubling bifurcation. The vibratory measurement of test-bed of the gear transmission system was performed. Accelerometers were employed to measure the high frequency vibration. Experimental results show that the vibration acceleration of the gear transmission system includes mesh frequency and sideband. The numerical calculation results of low speed can be validated by experimental results basically. It means that the presented non-linear dynamic model of the gear transmission system is right.