Support design method for deep soft-rock tunnels in non-hydrostatic high in-situ stress field

Due to the long-term plate tectonic movements in southwestern China,the in-situ stress field in deep formations is complex.When passing through deep soft-rock mass under non-hydrostatic high in-situ stress field,tunnels will suffer serious asymmetric deformation.There is no available support design method for tunnels under such a situation in existing studies to clarify the support time and support stiffness.This study first analyzed the mechanical behavior of tunnels in non-hydrostatic in-situ stress field and derived the theoretical equations of the ground squeezing curve(GSC)and ground loosening curve(GLC).Then,based on the convergence confinement theory,the support design method of deep soft-rock tunnels under non-hydrostatic high in-situ stress field was established considering both squeezing and loosening pressures.In addition,this method can provide the clear support time and support stiffness of the second layer of initial support.The proposed design method was applied to the Wanhe tunnel of the China-Laos railway in China.Monitoring data indicated that the optimal support scheme had a good effect on controlling the tunnel deformation in non-hydrostatic high in-situ stress field.Field applications showed that the secondary lining could be constructed properly.

Effects of Two Curing Methods on Quality of Yellow Sun-cured Tobacco

[Objective] The aim was to research effects of bamboo split curing method and steely barn curing method on quality of yellow sun-cured tobacco, providing scientific references for optimization of curing technology of yellow sun-cured tobacco. [method] The tobaccos were divided into two groups treated with two methods and the related indices of treated tobaccos were then measured to evaluate effects of curing methods on quality of yellow sun-cured tobacco. [Result] Tobaccos treated with two methods were all dominated by reddish yellow and yellow; exterior quality differed little. In detail, total sugar and reducing sugar in an average level in three locations were all higher with method A than those with method B, but nicotine and total N were lower; comprehensive chemical components in group with method B proved more appropriate with higher K. In addition, sensory qualities of leaves in moderate and bottom locations were better with method B compared with method A; sensory quality of top leaves was better; comprehensive sensory quality of leaves treated with method B proved better. On the other hand, cost for method A was 2.82 times of method B; the area of sun-curing field was 3.27 times and manage- ment work was 1.77 times, which indicated that method B is low-cost and time-saving, which would be a guarantee of tobacco quality. [Conclusion] The research provides scientific references for rational use of tobacco resources and optimization of sun-curing technology.

A review of in-situ high-temperature characterizations for understanding the processes in metallurgical engineering

For the rational manipulation of the production quality of high-temperature metallurgical engineering,there are many challenges in understanding the processes involved because of the black box chemical/electrochemical reactors.To overcome this issue,various in-situ characterization methods have been recently developed to analyze the interactions between the composition,microstructure,and solid-liquid interface of high-temperature electrochemical electrodes and molten salts.In this review,recent progress of in-situ hightemperature characterization techniques is discussed to summarize the advances in understanding the processes in metallurgical engineering.In-situ high-temperature technologies and analytical methods mainly include synchrotron X-ray diffraction(s-XRD),laser scanning confocal microscopy,and X-ray computed microtomography(X-rayμ-CT),which are important platforms for analyzing the structure and morphology of the electrodes to reveal the complexity and variability of their interfaces.In addition,laser-induced breakdown spectroscopy,high-temperature Raman spectroscopy,and ultraviolet-visible absorption spectroscopy provide microscale characterizations of the composition and structure of molten salts.More importantly,the combination of X-rayμ-CT and s-XRD techniques enables the investigation of the chemical reaction mechanisms at the two-phase interface.Therefore,these in-situ methods are essential for analyzing the chemical/electrochemical kinetics of high-temperature reaction processes and establishing the theoretical principles for the efficient and stable operation of chemical/electrochemical metallurgical processes.

Effects of Curing Methods on the Permeability and Mechanism of Cover Concrete

Curing methods are one of the most important factors in determining the quality and compactness of cover concrete.The effect of curing methods on the water absorption and sorptivity coefficient of cover concrete with the substitution ratio of fly ash(FA)and ground granulated blast slag(GGBS)for cement between 30 wt%and 40 wt%was studied by capillary water absorption test.The vacuum saturation test and mercury intrusion test were employed to characterize these differences in the pore structure of cover concrete under different curing methods.With further analysis of the compactness of microstructure by SEM,the mechanism of the impact of curing methods on the permeability of cover concrete was revealed.The results obtained indicate that the effect of curing methods on the water absorption,sorptivity coefficient and porosity of cover concrete shows the trend of natural curing>cover curing>water curing>standard curing.It is also shown that reasonable curing is advantageous to reduce the porosity and permeability of cover concrete.In natural curing conditions,the appearance of porosity increasing and pore structure coarsening is more critical for covering concrete with mineral admixtures than for pure cement concrete.Therefore,the permeability of cover concrete with mineral admixtures is more sensitive to the early-age curing methods.

Stress initialization methods for dynamic numerical simulation of rock mass with high in-situ stress

In the context of deep rock engineering,the in-situ stress state is of major importance as it plays an important role in rock dynamic response behavior.Thus,stress initialization becomes crucial and is the first step for the dynamic response simulation of rock mass in a high in-situ stress field.In this paper,stress initialization methods,including their principles and operating procedures for reproducing steady in-situ stress state in LS-DYNA,are first introduced.Then the most popular four methods,i.e.,explicit dynamic relaxation(DR)method,implicit-explicit sequence method,Dynain file method and quasi-static method,are exemplified through a case analysis by using the RHT and plastic hardening rock material models to simulate rock blasting under in-situ stress condition.Based on the simulations,it is concluded that the stress initialization results obtained by implicit-explicit sequence method and dynain file method are closely related to the rock material model,and the explicit DR method has an obvious advantage in solution time when compared to other methods.Besides that,it is recommended to adopt two separate analyses for the whole numerical simulation of rock mass under the combined action of in-situ stress and dynamic disturbance.

Experimental investigation of interface curing stresses between PMMA and composite using digital speckle correlation method

This paper studies the interface curing stresses between polymethyl methacrylate (PMMA) and composite by means of digital speckle correlation method (DSCM).A new method by combining DSCM with the marker points is developed to measure the interface curing stresses,and the measurement principle is introduced.The interface curing stresses between PMMA and composite with different curing bonding conditions are measured and analyzed,this indicates that the residual stress for furnace heating and furnace cooling is the smallest.Finally,the measurement error is discussed by means of finite element method,the influences of glass microsphere between adhesive and PMMA can be ignored.

Analysis on method for effective in-situ stress measurement in hot dry rock reservoir

With the rapid increase of energy demand and the increasingly highlighted environmental problems, clean, safe and widely distributed geothermal resources have become a hot spot for renewable resources development. The state of in-situ stress is a major control parameter for multiple links including well location, fracture inspiration and reservoir assessment, so how to determine the accurate state of in-situ stress in the deep thermal reservoir becomes a core problem drawing widely attention and urgent to be solved. Based on features of hot dry rock reservoir in terms of temperature and pressure and the comparison analysis, this article proposes the method of Anelastic Strain Recovery(ASR) as an effective method for determining the state of in-situ stress in the area with HDR resources distributed and explains the availability of ASR method by application examples.

Research of in-situ hydraulic test method by using double packer equipment

Double packer equipment for hydraulic test can be used to measure pressure of test zone directly, and it is frequently used to perform many kinds of hydraulic tests and take groundwater sample from borehole. The test method of this equipment mainly includes the test design, implementation, interpretation and synthetic analysis. By adopting the double packer equipment for hydraulic test, the parameter distribution of rock permeability along borehole can be acquired, as well as the connectivity, water conductivity and water bearing capacity of the disclosed structure and the chemical characteristics of the deep groundwater. It is a necessary method for the research and evaluation of the complex hypotonicity terrace site selection under geological conditions. This method is not only suitable for the geological disposal of high level radioactive waste, but also can be used in the site selection of underground facilities such as storage of petroleum and carbon dioxide. Meanwhile, it has a good application prospect in other hydrogeological investigation fields.

A Methodology to Reduce Thermal Gradients Due to the Exothermic Reactions in Resin Transfer Molding Applications

Resin transfer molding(RTM)is among the most used manufacturing processes for composite parts.Initially,the resin cure is initiated by heat supply to the mold.The supplementary heat generated during the reaction can cause thermal gradients in the composite,potentially leading to undesired residual stresses which can cause shrinkage and warpage.In the present numerical study of these processes,a one-dimensional finite difference method is used to predict the temperature evolution and the degree of cure in the course of the resin polymerization;the effect of some parameters on the thermal gradient is then analyzed,namely:the fiber nature,the use of multiple layers of reinforcement with different thermal properties and also the temperature cycle variation.The validity of this numerical model is tested by comparison with experimental and numerical results in the existing literature.

In-situ Characterization of Non-aqueous Nano-dispersion Systems by Freeze-etching TEM and Comparative Study with Laser Scattering Method

In-situ characterization of non-aqueous nano-dispersion systems（NANDS） by freeze-etching transmission electron microscope（FETEM） was reported.To improve just-for-once successive rate of specimen preparation and get good characterization results,an improving specimen preparation method of freezing etching was developed.Size,distribution and morphology of NANDS were directly visualized.Some information of particle dispersion feature and particle density can also be obtained.Reproductivity of the FETEM characterization is excellent.Comparing with laser scattering method,which is liable to give positive error especially for small size particle anchoring disperser,FETEM characterization can give more accurate measurement of particle size.Moreover,FETEM can give dispersion feature of nanoparticle in non-aqueous medium.

Comparison of Benefits of Different Tobacco Loading Methods and Matching Baking Processes in Intensive Curing Houses

[Objectives]To compare the benefits of different tobacco loading methods and supporting baking processes in intensive curing houses.[Methods]Flue-cured tobacco variety K326 was taken as material,and comparative experiment on baking effects of six tobacco loading methods(traditional hanging pole,loose leaf stacking,loose leaf binding and inserting,loose leaf inserting,loose leaf net basket,loose leaf grid)was conducted.[Results]Cost of dry tobacco loading equipment for hanging pole and loose leaf stacking was 0.01 and 0.1 yuan/kg,and cost of tobacco loading by loose leaf basket reached 0.36 yuan/kg.Labor cost for baking dry tobacco by direct stacking of loose leaves reached 2.02 yuan/kg,which was the lowest,while labor cost for binding and inserting loose leaves reached 2.44 yuan/kg,which was the highest.Energy consumption cost of dry tobacco baking with loose leaf grid was 1.06 yuan/kg,which was the lowest,while baking energy consumption cost of loose leaf stacking reached 1.23 yuan/kg,which was the highest.From the perspective of baking income,loose leaf inserting reached 21.36 yuan/kg,which was the lowest,while net basket reached 27.79 yuan/kg,which was the highest,followed by grid(23.46 yuan/kg)and loose leaf binding and inserting(22.5 yuan/kg).[Conclusions]It is worth popularizing the loose leaf binding and inserting and the loose leaf grid baking.

In-situ gas contents of a multi-section coal seam in Sydney basin for coal and gas outburst management

The gas content is crucial for evaluating coal and gas outburst potential in underground coal mining. This study focuses on investigating the in-situ coal seam gas content and gas sorption capacity in a representative coal seam with multiple sections (A1, A2, and A3) in the Sydney basin, where the CO_(2) composition exceeds 90%. The fast direct desorption method and associated devices were described in detail and employed to measure the in-situ gas components (Q_(1), Q_(2), and Q_(3)) of the coal seam. The results show that in-situ total gas content (Q_(T)) ranges from 9.48 m^(3)/t for the A2 section to 14.80 m^(3)/t for the A3 section, surpassing the Level 2 outburst threshold limit value, thereby necessitating gas drainage measures. Among the gas components, Q_(2) demonstrates the highest contribution to Q_(T), ranging between 55% and 70%. Furthermore, high-pressure isothermal gas sorption experiments were conducted on coal samples from each seam section to explore their gas sorption capacity. The Langmuir model accurately characterizes CO_(2) sorption behavior, with ft coefcients (R^(2)) greater than 0.99. Strong positive correlations are observed between in-situ gas content and Langmuir volume, as well as between residual gas content (Q_(3)) and sorption hysteresis. Notably, the A3 seam section is proved to have a higher outburst propensity due to its higher Q_(1) and Q_(2) gas contents, lower sorption hysteresis, and reduced coal toughness f value. The insights derived from the study can contribute to the development of efective gas management strategies and enhance the safety and efciency of coal mining operations.

In-situ stress of coal reservoirs in the Zhengzhuang area of the southern Qinshui Basin and its effects on coalbed methane development

In-situ stress is a critical factor influencing the permeability of coal reservoirs and the production capacity of coalbed methane(CBM)wells.Accurate prediction of in-situ stress and investigation of its influence on coal reservoir permeability and production capacity are significant for CBM development.This study investigated the CBM development zone in the Zhengzhuang area of the Qinshui Basin.According to the low mechanical strength of coal reservoirs,this study derived a calculation model of the in-situ stress of coal reservoirs based on the multi-loop hydraulic fracturing method and analyzed the impacts of initial fractures on the calculated results.Moreover,by combining the data such as the in-situ stress,permeability,and drainage and recovery data of CBM wells,this study revealed the spatial distribution patterns of the current in-situ stress of the coal reservoirs and discussed the impacts of the insitu stress on the permeability and production capacity.The results are as follows.(1)Under given fracturing pressure,longer initial fractures are associated with higher calculated maximum horizontal principal stress values.Therefore,ignoring the effects of the initial fractures will cause the calculated values of the in-situ stress to be less than the actual values.(2)As the burial depth increases,the fracturing pressure,closure pressure,and the maximum and minimum horizontal principal stress of the coal reservoirs in the Zhengzhuang area constantly increase.The average gradients of the maximum and minimum horizontal principal stress are 3.17 MPa/100 m and 2.05 MPa/100 m,respectively.(3)Coal reservoir permeability is significantly controlled by the magnitude and state of the current in-situ stress.The coal reservoir permeability decreases exponentially with an increase in the effective principal stress.Moreover,a low lateral pressure coefficient(less than 1)is associated with minor horizontal compressive effects and high coal reservoir permeability.(4)Under similar conditions,such as resource endowments,CBM well capacity is higher in primary structural coal regions with moderate paleotectonic stress modification,low current in-situ stress,and lateral pressure coefficient of less than 1.

基于化学成分可用性的韶关烟区特色烤烟品种筛选及其评价方法探索

为明确韶关烟区不同特色烤烟品种的烟叶化学成分可用性,以及探索评价烟叶化学成分可用性的最佳方法,以韶关地区的主栽烤烟品种粤烟97为CK,采用化学成分可用性指数和局部惩罚型变权模型对红花大金元、翠碧一号、中烟特香301等3个特色烤烟品种在3个试验点的烟叶化学成分特征及其可用性进行了评价。结果表明:3个特色烤烟品种在韶关烟区不同试验点的化学成分差异较大,化学成分可用性指数分析结果表明,中烟特香301的CCUI值与CK最接近,翠碧一号的居中,红花大金元的最低;局部惩罚型变权模型分析结果表明,中烟特香301的F值(变权)略低于粤烟97的,但高于红花大金元、翠碧一号的。综上,中烟特香301在韶关烟区的化学成分可用性相对较高,可进一步试种研究。

二次翻耕起垄与稻草还田对土壤养分和烟叶产质量的影响

为探讨二次翻耕起垄与稻草还田两种栽培措施及其相互作用对土壤养分和烟叶产质量的影响,以烤烟品种K326为试验材料,按照两种不同翻耕起垄方式(一次性翻耕起垄和先翻耕晒垡再二次翻耕起垄)与是否稻草还田进行随机区组设计,在湖南宜章县烤烟种植区进行田间试验,分析比较各处理间的土壤养分和烟叶产质量差异。结果表明,与一次性翻耕起垄(T1+T2)和无稻草还田(T1+T3)相比,二次翻耕起垄(T3+T4)和稻草还田(T2+T4)能显著增加土壤有机质含量,提高烟叶糖碱比、氮碱比以及烟叶产量、产值和生产效益,并且两者表现出显著的相互作用;此外,二次翻耕起垄还能显著提高烟叶总糖和还原糖含量,并显著降低烟碱含量,使得糖碱比和氮碱比更趋合理。在感官评吸方面,稻草还田能显著提高烟叶感官评吸质量。从生产效益上分析,由于二次翻耕增加了生产成本,对于基础地力较好的砂质土壤,开展一次性翻耕起垄结合稻草还田可获得更好的经济效益。研究结果为湖南烟稻轮作区烤烟种植提供了科学参考依据。

高放废物处置缓冲材料砌块养护方法研究

在高放废物地质处置库中,作为阻滞核素迁移的关键环节,缓冲材料通常以高压实砌块形式放置于废物罐周围。为了保证砌块的工程性能,缓冲材料砌块在制备、储存、运输和安装等各阶段均应进行环境湿度控制,以减少环境湿度对砌块性能的劣化影响。以高庙子膨润土压实试样为研究对象,开展了裸样、覆膜、覆膜+密封等不同包装方式,在0~100%相对湿度环境下的长期养护性能测试。试验结果表明:针对含水率介于13%~15%之间的膨润土压实试样,当环境湿度在80%~92%养护时,试样的质量变化均不超过1%;其中在92%的环境湿度下,试样的质量变化不超过0.3%,为最优养护环境。采用覆膜+密封包装方式,可大幅拓宽环境湿度范围,试样在不同相对湿度下的质量变化大幅减少,当相对湿度超过57%后,试样的质量变化比均不超过1%。其中在相对湿度为92%的养护环境下,试样的质量变化比最小,仅为0.032%。研究结果可为解决米级尺度高放废物地质处置缓冲材料大型砌块长期存储这一难题提供基础参数和技术支撑。

变容积密集烤房的CFD分析与试验研究

为保障密集烤房装烟密度,降低烘烤的能源消耗,研发一套适用于密集烤房的变容积系统。在完成变容积装置的设计后,基于CFD方法模拟分析装置与烟叶的不同距离对烤房内部气体分布均匀性的影响。通过烘烤试验获取实际烘烤数据,对模拟值加以验证。试验结果表明:当隔板与烟叶距离为0 cm时,流速不均匀系数Kv为0.40,温度不均匀系数Kt为0.41,距离为10 cm时,Kv=0.41,Kt=0.43;距离为20 cm时,Kv=0.42,Kt=0.49。装烟区9个测量点的温度模拟值与实测值基本吻合,误差在6%以内。变容积烤房在装烟量为一半时,相比常规烤房的燃料消耗可节约13.4%。研究结果表明:当隔板与烟叶距离为0 cm时烤房内部的气体分布最均匀;CFD模型与数值模拟结果具有可靠性;变容积装置具有较好的保温效果,可保证装烟密度,降低烤烟能耗。

干旱指数法综合评价河南烤烟新品种抗旱性

以中烟100、云烟87和NC89为对照品种,采用PEG(聚乙二醇)模拟干旱试验,结合盆栽控水试验研究干旱胁迫对河南省烤烟新品种的影响,采用干旱指数法综合评价新品种的抗旱性。结果表明,河洛1号抗旱性最强;其次是豫浓香201,在中度干旱胁迫条件下抗旱性较强,重度干旱则影响烟叶正常生长;渠首1号抗旱性与对照品种NC89、中烟100和云烟87基本相当。

基于气候适宜度的吉林省烤烟产量评估

烤烟是吉林省的经济作物之一,也是农民增收的重要作物之一,掌握其产量变化对保障烟农增收十分必要。气候条件是对烤烟产量影响最大的因素,目前预测评估气象因子对吉林省烤烟产量影响方面的研究较少。因此,本文利用指数平滑法分离出1981—2018年吉林省烤烟趋势产量和气象产量,利用隶属函数法确定了旺长期(6月)降水和大田生长期可用时间是影响吉林省烤烟产量的重要气象因子,计算出每个县各个影响因子的适宜度,再通过信息熵值法计算出烤烟产量气候影响因子的权重,并计算出每个地市的综合气候适宜度,最后建立烤烟气象产量与地市综合气候适宜度的多元线性回归模型。结果表明,烟叶旺长期降水和大田生长期可用时间是吉林省烤烟产量的气象限制因素,其中烤烟旺长期降水影响权重占0.81,大田生长期可用时间影响权重占0.19。通过该方法建立的产量预报模型准确率在80%以上,该方法可以用于烤烟产量评估。

基于响应面法的碱硫酸盐激发固废型固化剂组成优化设计

论文采用响应面法对碱-硫酸盐激发固废型固化剂体系进行优化,以赤泥、矿渣、生石灰和脱硫石膏为变量因素,以流态固化土的7 d、28 d无侧限抗压强度和流动扩展度为评价指标,建立预测模型。结果表明:当赤泥掺量为26.6%、矿渣掺量为53.2%、石灰掺量为11.7%、脱硫石膏掺量为8.5%时,流态固化土的工作性能和力学性能均达到最优,响应值的实测值和预测值误差范围控制在5%内,表明该响应面法预测模型预测精度高。