响应面法优化光聚合CMCTS-g-CPAM及其污泥脱水性能

以羧甲基壳聚糖（CMCTS）为主链模板、丙烯酰胺（AM）和甲基丙烯酰氧乙基三甲基氯化铵（DMC）为共聚单体,通过紫外光引发聚合法制备新型阳离子絮凝剂CMCTS-g-CPAM。采用响应曲面法（RSM）得到CMCTS-g-CPAM的最佳制备条件：光照时间为2 h、光引发剂质量分数为0.04%、pH值为8。接枝共聚物CMCTS-g-CPAM的红外光谱（FT-IR）和核磁共振（¹H-NMR）表征表明AM、DMC和CMCTS已成功聚合。污泥脱水实验验证其具有良好的污泥脱水性能：在絮凝剂投加量和pH值分别为30 mg/L和10时,污泥比阻（SRF）由9.10×10¹³ m/kg降至1.96×10¹³ m/kg,滤饼含水率（FCMC）从90.15%降至79.28%,其污泥脱水效果和经济效益均优于市售CPAM。同时,此研究在污泥脱水中的应用为污泥脱水领域的絮凝处理和改性壳聚糖提供了一定参考。     

电渗作用下软土细观孔隙结构

软土细观孔隙结构变化是其宏观变形的根本原因。为了探索电渗中软土细观孔隙结构变化以及与宏观变形之间的关联机制,采用杭州软土开展电渗试验,监测了电渗中土体孔隙结构分布特征和含水量,从定性和定量两个方面对试验结果进行分析。研究发现,电渗过程中,粘土颗粒重新排列形成面面接触的片堆结构,土体孔隙比降低,孔隙空间形态变光滑,结构复杂性减弱。通过含水量计算所得孔隙比较实测孔隙比小,说明电渗排水量大于土体收缩量,这是因为,电渗本质为离子带动水分子的迁移,不能直接引起土骨架压缩。实际工程中,电渗法应与堆载、真空预压等联合使用。     

Impact of preflocculation on scroll decanter centrifuge separation performance

Industrial scroll decanter centrifuge (SDC) separation of the solids in fluid fine tailings (FFT) which have particles 10 μm and smaller in size require flocculant addition. Accordingly, the mechanism in the centrifuge is flocculation of the fine solid particles followed by sedimentation. Thus, feeding preflocculated material obviates the flocculation step inside the SDC resulting in improved process efficiency by reducing the power consumption and increasing the throughput capacity of each SDC. This work evaluated the separation performance of the SDC using inline static mixers to preflocculate oil sands FFT containing solids, 90 mass% of which are < 9 μm in size. The minimum G‐forces required to achieve the industry benchmarks of < 1 mass% solids in the centrate water and > 97 % fines capture rate were 750 G without preflocculation and 400 G with preflocculation. Since power consumption by the SDC, as expected, was directly proportional to the G‐force, the savings in power due to preflocculation amounted to 47 %. Preflocculation increased SDC throughput capacity by up to 50 %. Operating at lower G‐force has the additional benefits of protecting the high‐capital‐cost SDC machine and reducing ambient noise levels.     

三江平原典型区河水与地下水水量交换的时空变化规律分析

地下水与河水之间的水量交换具有复杂的过程,受地形地貌、水文及水文地质条件等的影响。以松花江、黑龙江、挠力河及乌苏里江4条河流作为边界的三江平原典型区为例,通过补充水文地质勘察,结合2000—2018年河水位及地下水位动态的空间分布,对该地区河流代表性河段河水与地下水水量交换的时空变化规律进行深入分析。结果表明：三江平原典型区四周河流代表段的河水与地下水的水力联系较强,研究期内50%以上的年份两者的水位变化呈显著或高度相关,其中松花江富锦段地下水位与河水位相关性最强,挠力河菜咀子段和乌苏里江海青段次之,黑龙江勤得利段最弱;多年平均背景下,挠力河菜咀子段为地表水补给地下水,松花江富锦段、乌苏里江海青段及黑龙江勤得利段皆为地下水补给地表水;松花江富锦段多年平均地表水地下水单宽交换量为10^-2m³/（d·m）量级,黑龙江勤得利段为10^-5m³/（d·m）量级,挠力河菜咀子段为10^-3m³/（d·m）量级,乌苏里江海青段为10^-3m³/（d·m）量级;相关系数与地表水地下水单宽交换量大小存在正相关,相关系数越大,单宽交换量越大,MK趋势检验结果表明,各河流代表性河段单宽交换量均存在减小趋势,其中乌苏里江海青段趋势显著,松花江富锦段趋势最小;松花江富锦段单宽交换量年际和年内波动强烈且均占主导地位,年内尺度下仅6月份为显著减小趋势,未构成年际尺度下显著减小的整体趋势,水量交换变化频繁、规律性较弱;黑龙江勤得利段年际及年内尺度波动均占主导地位,与松花江情况类似但波动程度较弱,年内尺度下不存在显著变化趋势,因此未构成显著减小的整体趋势;挠力河菜咀子段主要以年际尺度波动,1—5月存在显著减小趋势,但未增大年内尺度波动,且未构成显著减小的整体趋势;乌苏里江海青段主要为年内尺度波动,6—9月及12月的显著减小趋势增大了年内波动,且构成了显著减小的整体趋势。研究结果可为三江平原典型区水资源评价提供科学依据,为该地区水资源的科学开发利用提供理论参考。     

高含水率疏浚淤泥透气真空防淤堵模型

透气真空技术解决了传统真空处理高含水率疏浚淤泥存在的淤堵问题,但其防淤堵控制尚缺乏有效分析方法。利用Ruth滤水理论建立了高含水率疏浚淤泥径向排水模型,采用透气真空抽水模型的试验结果验证了模型的有效性。同时,明确了反映淤泥排水层滤水性能的径向平均比阻arav在抽水过程中的变化规律:传统真空抽水形成的淤泥排水层有一个被压密的过程,孔隙结构不稳定,排水管道易发生淤堵;而采用透气真空抽水可以使淤泥排水层形成相对稳定的孔隙结构,有效地防止淤堵现象的发生。     

某过江隧道南线工程降水方案研究

以纬三路过江通道南岸工程为背景,结合场区工程地质及水文地质条件,借鉴该地区类似工程经验,确定基坑降水的影响半径及场区综合渗透系数参考值,在此基础上进行深基坑的降水计算与设计,详细介绍了疏干井和降压井在基坑降水中的应用。最后,建立地下水渗流数值模型,采用三维有限差分法对基坑内承压含水层降水效果进行模拟验证。模拟结果表明:该降水方案合理可行,达到了设计要求,能够取得明显的效果。实践表明降水方案合理可行,可为该地区其他类似基坑降水工程提供指导。     

引江济汉工程干渠地基降水设计

引江济汉工程干渠地基涌水涌沙问题是施工的关键技术问题之一。为保证工程施工期的安全,根据其地层特点选择了合适的降排水方案。本文主要介绍干渠及交叉建筑物施工期深井降水与盲沟排水处理方案。该方案已成功地在15.124 km长的干渠及15座交叉建筑物等工程施工中应用,可供同类工程借鉴。     

大面积基坑开挖前预降水对支护墙变形的影响研究

首先基于工程实测,研究了大面积宽基坑土方开挖前群井预降水对支护墙变形的影响,实测到基坑开挖前降水引起的最大支护墙侧移达到15 mm,约为该基坑变形报警值的47.6%;并发现对于排桩支护墙,在支护侧布置降水井,可以起到减小坑内降水引起支护墙侧移的作用;然后开展了35个常见工况的三维流固耦合有限元数值计算,研究了基坑宽度对支护墙变形的影响规律及其机理。结果表明,宽度较大基坑在同一预降水时间和深度条件下将发生更大幅度支护墙侧移,而在通常的预降水深度(0~20 m)条件下,对于宽度为20~40 m的地铁基坑,降水引起的支护墙最大变形及其增量均对基坑宽度的变化十分敏感,而对于宽度大于40 m的基坑,在同一降水深度条件下,支护墙最大侧移仅有较小的差别。而引起上述规律的机理可用降水过程中基坑中轴两侧土体侧移的叠加效应强弱来解释,基坑宽度越小,降水过程中坑内土体侧移叠加效应越明显,最大支护墙侧移就越小。     

Effect of hydrothermal dewatering on physicochemical properties and moisture re-adsorption capacity of a lignite

The effects of hydrothermal dewatering (HTD) on physicochemical properties and moisture re-adsorption capacity of Zhaotong lignite were analyzed. The results showed that HTD could improve the quality of lignite. During the process of HTD, oxygen-containing functional groups decomposed. Both high temperature and pressure favor the formation of large pore volume and small pore diameter. Treated temperature was the key factor governing the moisture re-adsorption capacity of lignite. The moisture re-adsorption degree decreased from 12.47% to 6.13% when the temperature varied from 200 to 300°C. While, the pressure had weaker effect on the degree of moisture re-adsorption.     

Testing microwave dewatering as a solution for reducing clay disposal pond areas

Phosphate processing plants produce an excessive amount of phosphatic clay. This clay represents a serious environmental problem due to their disposal in huge ponds. Finding a feasible method to reduce the clay disposal area is needed. Although the flocculation process, in the presence of fibrous material, seems to be a good dewatering process for phosphatic clay wastes, the maximum solid percentage of flocculated clay does not exceed 18% (starting from 3 to 4%). Recently, the microwave proved a better performance in several research areas as compared to the conventional drying. In this study, clay dewatering by microwave was investigated. Several factors affecting the dewatering process were studied such as heating time, microwave power efficiency, and fiber percentage. Using the microwave, the solid content significantly increases in a reasonably short time. The time and power are the most significant among the studied factors. In addition, sand–clay mix was tested to improve the solid percentage to be used as a filling material. The results showed that the presence of sand enhances the clay drying due to the transparency of sand to the microwave irradiation as well as increasing the clay bed porosity, which facilitates migration of liquid water and/or water vapor toward the surface of dried material.