河道淤泥气泡混合轻质土的性质稳定性试验

对以河道淤泥为原料土的气泡混合轻质土的工程性质稳定性进行研究,通过试验考察研究了轻质土在不同条件下的主要物理力学性质的稳定性,研究结果表明在考虑包括静荷载、循环荷载、使用环境等因素的情况下,轻质土的强度与变形等工程性质具有良好稳定性,为促进轻质土的工程应用提供了必要的理论依据.     

河道淤泥气泡混合轻质土剪切流变特性及模型

利用剪切流变试验对以水泥为固化剂的河道淤泥气泡混合轻质土的流变特性进行了试验研究。试验结果表明,经固化处理的河道淤泥气泡混合轻质土在荷载作用下具有类似于硬粘性土的流变特征。剪切流变可以分为3个阶段：在剪应力水平较低时,剪切流变曲线呈衰减稳定型;随着剪应力水平的提高,剪切流变曲线呈非稳定的等速型;当剪应力水平增大到一定程度时,剪切流变曲线呈加速型。河道淤泥气泡混合轻质土的流变性随着混合轻质土强度的提高而降低。根据试验所呈现的剪切流变规律,可以发现河道淤泥气泡混合轻质土的剪切流变符合七元件黏弹塑性剪切流变模型,模型能够比较好地描述河道淤泥混合轻质土在各种剪应力水平下的衰减、等速以及加速流变过程。     

混合炉渣河道淤泥气泡轻质土力学特性试验研究

为了有效利用炉渣,通过三轴压缩试验研究了混合炉渣河道淤泥气泡轻质土的力学性质。混合土的密度、强度和变形特性受炉渣掺量、气泡掺量影响显著。试验结果显示:混合土具有良好的轻质性,其强度参数c、φ值随炉渣掺量增加而增大,随气泡掺量增加而减小。基于邓肯-张双曲线模型研究发现,掺入炉渣后,混合土的初始变形模量增大,极限偏应力也增大。研究结果表明混合土具有广泛的应用前景。     

重金属污染土物理性质-强度定量关系试验研究

通过室内试验研究土体孔隙液中重金属离子影响土体物理-力学性状的机理,采用不同浓度的重金属Cu²⁺、Zn²⁺、Pb²⁺掺入高岭土、伊利石类黏土和钠基膨润土,研究土体界限含液率、不排水抗剪强度随重金属离子浓度的变化规律。试验结果表明：以高岭石、伊利石为主要黏土矿物的低活性土的液限、塑性指数随离子浓度的增加而增大,钠基膨润土则表现出相反的变化规律;低活性黏土的不排水抗剪强度随离子浓度增加而增大,高活性黏土强度则随之减小;基于已有的无污染土体物理-力学性状定量联系,分析重金属污染土的不排水抗剪强度与液性指数的定量关系,发现重金属离子引起的不排水抗剪强度的变化可以归结于重金属离子引起的液塑限变化,表明重金属Cu²⁺、Zn²⁺、Pb²⁺污染过程基本没有产生化学反应,其物理-力学定量关系与已有的无污染土经验关系式一致。     

Ca2+对SiO2-BSA混合体系膜污染行为的影响

为研究Ca²⁺对SiO₂-BSA混合污染物膜污染行为的影响,针对SiO₂与牛血清蛋白(BSA)共存体系,在不同Ca²⁺浓度下,使用原子力显微镜测定各污染物与聚偏氟乙烯(PVDF)超滤膜及各污染物之间的作用力,结合膜污染实验,探讨Ca²⁺对SiO₂-BSA混合污染物膜污染行为的影响.结果表明:随着Ca²⁺浓度的增大,SiO₂-BSA引起的膜污染逐渐减小,主要是因为Ca²⁺改变了SiO₂-BSA混合体系中各污染物与膜及污染物之间的相互作用力.针对污染物与膜之间的相互作用力,Ca²⁺的加入触发了PVDF膜与BSA及SiO₂之间的水合排斥力,从而削弱BSA在膜表面的吸附累计速率,有效减缓了运行初期的膜污染速率;针对污染物之间的作用力,Ca²⁺浓度的增加使得SiO₂-SiO₂及SiO₂-BSA之间作用力增大,从而导致污染物团聚形成大尺寸聚集体,在膜面形成松散多孔的污染层,进而伴随着膜污染速率以及污染幅度的减小.     

硝酸侵蚀衬砌喷射混凝土中性化过程及机理

以一般大气环境喷射混凝土永久衬砌长大公路隧道为工程背景,开展汽车尾气中氮氧化物对喷射混凝土衬砌结构中性化过程及机理研究。以pH值为2的硝酸溶液为侵蚀介质,对喷射混凝土开展浸泡试验。以侵蚀喷射混凝土的物理力学性能及离子含量为表征指标,分析喷射混凝土中性化过程。采用X射线衍射、热分析及扫描电镜,分析及表征喷射混凝土中性化区的物相组成及微观形貌,研究喷射混凝土中性化发展过程及机理。结果表明,硝酸侵蚀喷射混凝土中性化演化过程可分为中和反应阶段、水化产物分解阶段、混凝土表面剥蚀等3个阶段。期间,喷射混凝土pH值逐渐下降,NO₃^-含量升高。随着侵蚀的进行,水化硅酸钙及氢氧化钙的含量降低,硝酸钙、硝酸型水化氮铝酸钙及高岭石的相对含量增大,微观结构被破坏,中性化速度加快,物理力学性能降低。     

河道淤泥气泡混合土微观构造及力学性质相关性

基于河道淤泥气泡混合土(FMLSS)的微观构造特征,通过微观构造观察和分析,评价了FMLSS的强度特性和破坏机理。试验结果表明,保持FMLSS含水量一定,随着气泡掺入量的增加,FMLSS的内部平均等效孔径和气孔面积百分比含量呈线性增大趋势、而随着水泥掺入量的增加呈减小趋势;随着气泡掺入量的增加,FMLSS的气孔大小分布的均匀性降低,气孔平均等效孔径增大。试验结果还表明,FMLSS的强度发挥及破坏机理与FMLSS的气孔分布的均匀性以及等效孔径等微观构造参数存在明显的相关性。     

石灰铝盐法沉淀废水中高浓度氯离子的研究

工业废水中高氯离子使其具有腐蚀性并妨碍水生动植物生长, 破坏生态环境, 在排放之前必须进行氯离子 去除, 达到排放要求。探究了单因素对氯离子去除率的影响, 并讨论了投料比、搅拌时间、静置时间以及体系初始 pH 对去除率影响及交互作用。研究表明: 搅拌速度为400 r/min, n(Al³⁺) : n(Ca^{2+) 为1 : 3.3, 搅拌时间为30 min, 静 置时间为30 min, 废水初始pH 为10 时, 去除效果最佳。应用所得最佳条件对实际水样进行二次去除实验并探讨了 相关影响因素。对实际水样二次氯离子去除实验的最佳工艺条件: 当n(Cl-):n(Al3+) : n(Ca2+) 为1 : 3.6 : 12, 初始溶 液浓度为4 g/L 时, 并且需要在二阶段投加药品前调节体系pH 值至弱碱性, 氯离子去除效率可达95%, 浓度可降到 400 mg/L 以下。通过X 射线洐射分析可知, 沉淀产物为层状结构的弗氏盐[Ca₂Al(OH)₆Cl·2H₂O]。此方法成本低、 无污染, 对高氯废水去除有很好的应用价值。}     

城市河道淤泥资源化利用的烧结制砖试验研究

城市疏浚河道清出的淤泥,含水量大、有机质含量高、气味臭、有时还含有有毒有害物质,如何进行无害化、资源化处理成为当前城市可持续发展的重要研究课题。以南京秦淮河中段清淤工程为例,以其清出的淤泥为原料,添加一定比例粘性土,淤泥与粘性土比例分别为1∶1、3∶2和7∶3的3组砖坯试样,在1 000、1 050和1 100℃3个不同温度下进行烧结制砖试验。分别测试了烧成品试样的烧失率、线收缩率、吸水率、抗压强度等物理力学参数,并利用XRD和SEM研究了烧成品的微观结构特征,综合分析了粘性土含量和烧结温度对淤泥进行资源化处理效果的影响。研究结果表明:烧结温度对试样烧结效果影响显著,当烧结温度为1 100℃时,3组试样均出现过烧现象,1 050℃比较接近试样的适宜烧结温度;粘土含量逐渐增加,烧成品物理力学性质逐渐改善,当粘土含量增加到50%,烧结温度为1 050℃时,砖块体积密度为1.4g/cm3、吸水率为17.28%、线收缩率为-0.5%、抗压强度为12.56Mpa,具有轻质保温特性,各项性能均能够满足工程建设有关规范对普通砖的要求。研究结果对城市景观河道疏浚淤泥的资源化处理具有参考价值。     

干湿循环作用下固化淤泥的抗剪强度变化规律

河、湖等的疏浚淤泥多采用固化方式进行处理。针对固化淤泥材料的干湿稳定性问题,系统开展了干湿循环作用下水泥固化疏浚淤泥的抗剪强度特性试验研究,揭示了固化淤泥在干湿循环作用下抗剪强度的变化机理,并对各影响因素进行了定量分析。结果表明：随着干湿循环次数的增加,固化淤泥的抗剪强度逐渐变化,且先快后慢,最后趋于稳定;干湿循环后,水泥掺量100 kg/m³固化淤泥试样的抗剪强度降低,而水泥掺量150、200 kg/m³试样干湿循环后的抗剪强度不降反增,说明干湿循环对固化淤泥的影响与水泥的掺量有关。较高的干燥温度促进了水泥水化,从而导致水化产物增加,固化淤泥的抗剪强度增大;同时,干湿循环过程中,微裂缝的发育导致固化淤泥的抗剪强度降低,干湿循环对固化淤泥抗剪强度的影响取决于二者的综合作用。     

钝化土壤酸化过程机理及关键影响因子研究

施加钝化材料固定有毒重金属的方法在污染土壤修复领域有着广泛应用。但钝化土壤的酸化作用会使已固定的重金属重新活化,钝化剂应用在长效性方面存在局限。因此,研究钝化土壤酸化对土壤修复工作有重要应用参考价值。本研究选取西南地区3种代表性土壤,分别测定其酸化程度与交换性酸浓度,通过相关性分析判断土壤酸化的内在机理;同时应用SPSS软件,通过多元统计分析方法探究土壤理化性质对土壤酸化的影响,进一步采用主成分分析和线性回归方程建立定量函数表达以研究影响钝化土壤酸化的关键因子。结果表明：1）钝化土壤酸化的实质主要是致酸交换性离子H⁺和Al³⁺置换盐基离子Ca²⁺和Mg²⁺的过程。反应前期主要是Al³⁺积累,其与酸化程度相关性达0.567;2）影响土壤酸化关键的因子是Ca元素和土壤粒度,其中Ca的影响最大, 主成分分析结果显示其贡献率达到79%;在土壤粒度组成中,黏粒百分比对酸化影响最大;3）本研究尝试提出钝化材料的选择应遵循“补偿机制”,即在选择钝化成分时针对性地补充土壤较匮乏的因子,同时避免添加较丰足因子。本文的定量分析结果为今后深入研究钝化土壤酸化提供理论依据。     

模拟酸雨对三峡库区灰棕紫泥酸化的影响

采用模拟酸雨淋溶实验,研究了不同pH值条件下模拟酸雨对三峡库区灰棕紫泥酸化的影响。结果表明,酸雨pH值越低对土壤酸化影响越严重;不同酸雨淋溶经不同层次土体的收集淋出液的电导都呈现先升后降的趋势,而淋出液的pH值却显示出先降后升的变化趋势;土壤pH值和CEC含量越高,淋滤液的电导率越大;土壤盐基离子的淋失量随模拟酸雨pH值的降低而增加,而土壤铝的淋溶量随酸雨pH值下降而上升。经不同的酸雨淋洗后,对不同层次土体进行理化性质分析,均出现了不同程度的变化。     

Effect of Acid Rain Erosion on Steel Fiber Reinforced Concrete

Acid rain can deteriorate the performance of reinforced concrete structure.Combined with the characteristics of acid rain in China,the properties of steel fiber reinforced concrete subjected to acid rain were studied.The effects of steel fiber content and pH value of acid rain on the mass loss,erosion depth,neutralization depth,and splitting tensile strength of tested concrete were investigated.The mercury intrusion pore(MIP) test was used to analyze the influence of steel fiber on the acid rain resistance of concrete matrix.The results show that the corrosion of steel fiber reinforced concrete subjected to acid rain results from the combined effect of H~+ and SO_4~(2-) in the acid rain,and steel fiber can improve the acid rain resistance of the tested concrete by improving the pore structure and enhancing the tie effect of the concrete matrix.The experiment further indicates that the optimum content of steel fiber is 1.5%compared to the various mixing proportion in this tests.The tested concrete mass loss and splitting tensile strength decrease followed by increasing as a function of corrosion time when the pH value of the simulation solution is 3 or 4,while they decrease continuously in the simulation solution at pH 2.Thanks to the tie effect of steel fiber,the spalling of concrete matrix is significantly improved,and the erosion depth and neutralization depth are less than those of conventional concrete.     

Effects of clay and calcium ions on coal flotation

The microflotation of three single minerals, mixed coal–kaolinite and mixed coal–montmorillonite were examined to study the effects of clay and calcium ions on coal flotation. The results show that the ash content of flotation concentrate increases by 3% in the presence of clay minerals, and the ash content would further increase by 3% in co-presence of clay minerals and high concentration of Ca²⁺. Scanning electron microscope (SEM) images and elemental spectrum analysis indicate that fine clay particles that coat on the coal surface, which is called slime coating, can affect the coal flotation. The slime coating would be induced much more easily in the presence of Ca²⁺.     

Influence of Polyepoxysuccinic Acid on Solid Phase Products in Portland Cement Pastes

The influence of polyepoxysuccinic acid(PESA) on the solid phase products in hydrated Portland cement pastes was investigated by isothermal calorimetry, X-ray diffraction(XRD), ²⁹Si and ²⁷Al nuclear magnetic resonance(NMR). The results indicated that PESA bonds Ca²⁺ ions in pore solution to prevent portlandite formation, and also combines with Ca²⁺ ions on the surface of silicate minerals to prolong the control time of phase boundary reaction process, leading to the retardation of silicate mineral hydration. Meanwhile, the interlayer Ca²⁺ ions in Jennite-like structure bridging PESA and C-S-H gels prevent silicate tetrahedron and aluminum tetrahedron from occupying the sites of bridging silicate tetrahedron, which causes the main existence of dimer in C-S-H structure, deceases the degree of Al³⁺ substituting for Si⁴⁺ and promotes the transformation from 4-coordination aluminum to 6-coordination aluminum. Furthermore, the -Ca⁺ chelating group from reacting PESA with Ca²⁺ ions combines easily with SO₄^2- ions, resulting in transformation from ettringite, AFm to TAH(Third aluminum hydrate). However, with the higher addition of PESA, it will bridge the excess PESA by Ca²⁺ ions to form a new chelate with ladder-shaped double chains structure, which not only reduces the amount of PESA bonding Ca²⁺ ions, but also decreases its solidifying capability for SO₄^2- ions, leading to the transformation from TAH to AFm or ettringite. Meanwhile, at later hydration, the inhibition effect of PESA on cement hydration is weakened, and the transformation degree from TAH to AFm is higher than that to AFt with the addition of PESA.     

模拟酸雨对三峡库区黄壤理化性质的影响

利用pH2.50、3.50、4.50、5.60的模拟酸雨对三峡库区黄壤进行了室内土柱淋溶实验,研究表明:长时间受酸雨淋洗,黄壤对酸雨的缓冲性能降低,且酸雨pH值越低,对土壤酸化影响越大;不同酸雨淋溶不同层次土体的收集淋出液的电导都呈现先升后降的趋势,而且都有一个峰值,但峰形有明显差异;铝的淋失量随酸雨pH值下降而上升。     

Effects of Excess Barium on the Structure and Electrical Properties of (Ba,Ca)TiO<Subscript>3</Subscript> Piezoelectric Ceramics with High Mechanical Quality Factors

Manganese-doped Ba_0.925Ca_0.075TiO₃ lead-free piezoelectric ceramics (abbreviated as BCT) with high mechanical quality factor were synthesized by conventional solid-state reaction method. The effects of excess Ba on the crystal structure, microstructure, and electrical properties of the ceramics were systematically investigated. X-ray diffraction and Raman spectra revealed that Ca²⁺ ions were pushed from Ba sites to Ti sites of BCT when 1.5 mol% extra Ba²⁺ ions were added after sintering. The grain size of the ceramics was decreased by adding extra Ba²⁺ ions. The mechanical quality factor and resistivity of the ceramics decreased dramatically when the excess Ba was more than 1.5 mol%. High piezoelectric coefficients ( d₃₃ = 150–190 pC/N ) and high mechanical quality factors ( Q_m = 1 000–1 200 ) were obtained in the ceramics when the excess of Ba was between 0.5 mol% and 1 mol%. These results indicated that the properties of BCT ceramics could be tailored by adjusting the content of Ba.     

有机物对聚酰胺复合纳滤膜硫酸钙结垢的影响

为揭示不同有机物形成的污染层对硫酸钙在纳滤膜面结垢行为的影响,选用牛血清蛋白(BSA)、腐殖酸(HA)、海藻酸(SA)作为典型有机污染物对聚酰胺复合纳滤膜进行污染,之后进行硫酸钙结垢实验.利用扫描电镜(SEM)观察不同污染条件下的硫酸钙形态,采用原子力显微镜(AFM)结合自制的硫酸钙探针测定不同污染条件下膜-硫酸钙及硫酸钙-硫酸钙之间的作用力.结果表明:与新膜结垢相比,有机物吸附在纳滤膜上改变了膜面性质,影响硫酸钙晶体成核机理.3种有机污染条件下硫酸钙结垢污染程度为SAHABSA.这是因为SA与Ca~(2+)的相互作用可缩短硫酸钙晶体成核时间,增大晶体尺寸,导致纳滤膜通量迅速下降;HA与Ca~(2+)络合增大了结垢层的厚度和密实度,导致纳滤膜通量衰减较大;而BSA与Ca~(2+)的结合能力较弱,加上其特殊的心形分子结构,导致该情况下硫酸钙结垢程度弱于其他两种有机物条件.     

Leaching potential and changes in components of metals in two acidic ferrisols

Two acidic ferrisols, i.e., red soil （RS） and yellow red soil （YRS）, from the vicinity regions of non-ferrous ores in Hunan province of China, were leached with simulated acid rain through artificial column experiments. The results show that the total leaching mass of metals are m（Zn）〉m（Cu）〉m（Cd） from the original soils and m（Cd）〉m（Zn）〉〉 m（Cu） from the contaminated soils with external metals after leaching for 60 d continuously, leaching quantities of Cd and Zn from the contaminated red soil （CRS） are more than that from the contaminated yellow red soil （CYRS）, but for Cu, it is almost the same. The preferential fractions for leaching are mainly in exchangeable forms, and content of exchangeable forms decreases significantly in the contaminated soil profiles. The unstable fractions of Cd, Cu and Zn in the RS and YRS increase significantly with the decrease of pH value of simulated acid rain. Changes of fi, actions of external Cd, Cu, and Zn in the residual CRS and CYRS profiles are significantly affected by the acidity of acid rain, too. After leaching for 60 d continuously, Cd exists mostly in exchangeable form, Cu exists mainly in exchangeable, manganese oxide-occluded and organically bounding forms, and Zn exists in residual in CRS and CYRS profiles. Most of exchangeable Cd and Zn exist only small in surface layer （0-20 cm） and are transferred to the sub-layers, contrarily, Cu accumulates mostly in the topsoil （0-20 cm） with low translocation.