高浓度铝酸钠溶液制采砂状氧化铝

本文介绍了在半工业规模条件下,用高浓度铝酸钠溶液(Na_2O_k155g/l,α_k1.55)制取砂状氧化铝的试验研究。试验中掌握了控制粒度平衡的技术,旋流细筛用于氢氧化铝分级、真空降温用于氢氧化铝浆液的冷却获得的产品水氧化铝粒度小于45ηm7.3％,磨损指数24,比表面积63.8m~2/y。精液氧化铝产出率73.7ky/m~3。     

烧结法生产砂状氧化铝

我国的Al_2O_3主要是拜耳烧结联合法和碱石灰烧结法生严的。由烧结法精液生产的Al_2O_3约占Al_2O_3总产量的50%,这种Al_2O_3的强度太低,在焙烧及输送过程中破损严重,不能满足干法烟气净化系统及连继中间下料予焙电解槽的要求。我们根据试验工场的试验结果,研制出了新的碳酸化分解工艺及种子搅拌分解工艺,生产出了粗的和强度高的砂状Al_2O_3。该新工艺的主要特征是: 1.产品砂状Al_2O_3的主要物理性质: 碳分砂状Al_2O_3:粒度%:+150μM8.7,-45μM7.3;磨损指数16.7%。种分砂状Al_2O_3:粒度%:+150μM5.4,-45μM8.4:磨损指数11.6%。 2.不降低碳酸化分解率和产品质量。 3.不降低碳酸化分解及种子搅拌分解槽的产能。 4.不需要分级就能生产出砂状Al_2O_3。     

泡沫稳定性对土压平衡盾构砂卵石渣土改良效果

为确保土压平衡盾构在砂卵石地层施工时切削的渣土具有良好的工程特性,以成都轨道17号线明九区间2号风井—九江北区间为背景,采用不同稳定性的泡沫剂分别掺入卵砾石含量为20%、40%和60%的砂卵石渣土中,开展室内坍落度试验、渗透试验和喷涌试验,研究各种泡沫土流动性、渗透性和时效性的变化规律,探讨泡沫剂稳定性与砂卵石渣土的适应性。结果表明：稳定性好的泡沫能够适应卵砾石含量低于60%的砂卵石土层,即泡沫稳定性的提高有利于扩大砂卵石地层的适用范围;稳定性好的泡沫剂能够保持改良砂卵石渣土掘削排渣全过程良好的流动性、抗渗性;过量的泡沫掺入改良的砂卵石渣土易发生离析,造成改良后的渣土难以达到良好的和易性;泡沫改良砂卵石渣土的喷涌压力可作为检验改良效果的重要指标。     

砂土地层水下盾构隧道开挖面被动破坏数值模拟

基于Mohr-Coulomb强度准则和不相关联的流动法则,采用Abaqus模拟砂土地层水下盾构隧道开挖面被动破坏,分析埋深比C/D、地层上覆水位高度H、砂土内摩擦角φ对地表位移的影响,并探讨开挖面前方土体破坏模式。结果表明：标准开挖面支护压力与C/D、H和砂土φ均呈正相关关系;地表位移受C/D变化影响较大,C/D由0.8增大到1.5,最大纵向和横向位移值分别减小80%和86%;静水压力仅会限制横向地表位移的发展,对纵向地表位移的影响较小;C/D较小时,被动破坏模式呈现延伸至地表的倒棱台形,属于整体破坏;C/D增大至4.3时,土拱无法达到地表,属于局部破坏。     

北京地铁敞口式盾构掘进对砂层土体扰动规律研究

敞口式盾构在砂层掘进时会扰动周围土体,易引起地层坍塌.以北京地铁6号线2期敞口式盾构施工段为工程背景,阐述了国内首台挤压式敞口盾构机机体构造及开挖工序,通过地表沉降和地中水平位移监测,研究了盾构掘进对砂层的扰动特征.结合盾构掘进参数分析,探讨了减少土体扰动的控制措施.研究表明,盾构接近测孔区阶段,土体变形规律最复杂;通过和刚脱离测孔区阶段是土层变形控制的重要环节;盾构隧道轴线两侧1.5倍洞径范围内是土体扰动主要区域.所得结论可为砂土地层敞口式盾构施工地层位移控制提供可鉴参考.     

Spatial distribution of the ghost crab Ocypode quadrata in low‐energy tide‐dominated sandy beaches

The spatial distribution of the ghost crab Ocypode quadrata (Crustacea, Brachyura) was described in five low‐energy tide‐dominated sandy beaches in São Sebastião Channel (Grande, Zimbro, Pitangueiras, Cabelo Gordo, and Segredo). On each beach, the zonation study was performed on five random 1?m wide transects sampled from the water line to the vegetation. In general, individuals occurred above 1?m in height in relation to mean low water (MLW) and peaked between 1.5 and 2.0?m. The sandy beaches were then divided into three 1?m wide strips (tidal levels) parallel to the water line and equivalent to medium intertidal, upper intertidal, and subterrestrial fringe to test the effect of beach and tidal level on the abundance and size of O. quadrata. These strips were sampled as a whole using adjacent 1 m² squares. A previous evaluation showed a positive significant relationship between carapace length and burrow diameter, thus supporting crab size estimates from burrow openings. The smallest individuals occurred mainly in the medium intertidal, but were also recorded in the subterrestrial fringe, which was occupied mainly by large‐sized individuals. In general, the individuals were randomly dispersed within the strips and concentrated in the upper intertidal zone on all the sandy beaches. The density of O. quadrata varied among beaches, with a tendency to lower values on areas with very fine and poorly or moderately sorted sediments and on that most used for recreational activities (Grande). Burrow size also varied among beaches, with a tendency of smaller burrows in areas with coarser sand grains and higher tourism. These results indicate that the effect of human impact on density and size of O. quadrata may be confounded by the high environmental heterogeneity of the studied system, which may make it difficult to utilize this species as an indicator of the conservation status of low‐energy tide‐dominated sandy beaches.     

新疆多泥沙河流水能开发与引水工程管理探索

古尔图河具有防洪、灌溉、发电、旅游、人蓄供水、水库蓄水等综合功能的山区中小型河流;对于水利工程而言,建设是基础,管理是关键,使用是目的,"三分建、七分管",工程管理的好坏,直接影响效益的高低。     

富水砂层土压平衡盾构施工渣土改良试验

针对深圳的富水砂层,采用泡沫、膨润土以及高分子聚合物等添加剂,改良盾构施工渣土,进行现场坍落度试验.基于现场试验结果,通过对土样进行电镜扫描以及压缩、渗透等室内试验研究,分析了改性渣土细观结构以及渗透、压缩特性的变化.对添加剂改善富水砂性土的流塑性、保水性以及开挖面动态土压平衡机理作了较深入的探讨.结果表明,富水砂层中,采用质量比为1∶7、外掺量为8%~10%的膨润土进行渣土改良,可满足施工需求.     

荒漠化动力系统熵理论模式探索

用耗散结构理论分析了荒漠化系统的不同演变状态,指出决定荒漠化状态演变的4个熵阀值和荒漠化发展中的2次突变,圈定出荒漠化良性发展的区间,在此基础上构建了荒漠化动力系统的熵理论模式.该模式为进一步量化分析荒漠化以及进行荒漠化的防治提供理论依据.