水泥固化体淋滤液对GCL防渗性能的影响

水泥固化/稳定化是危险废弃物处理的经济、高效方法,然而,水泥固化体的淋滤液中含有大量Ca~(2+),其长期渗透有可能导致填埋场底部土工合成黏土衬垫(geosyntheticclayliner,GCL)的防渗性能下降,从而引发二次污染。使用柔性壁渗透仪,测定有效应力和水泥固化体淋滤液共同作用下GCL的渗透系数,探讨了淋滤液浓度以及不同有效应力对GCL渗透系数的影响。试验结果表明:当有效应力为24kPa时,水泥固化体淋滤液的持续渗透会使GCL的渗透系数增大179～721倍,淋滤液中Ca~(2+)浓度越高,GCL渗透系数增大的幅度越大。通过增加有效应力,可以降低固化体淋滤液对GCL防渗性能所造成的负面影响,当有效应力增大至438 kPa时,固化体淋滤液对GCL防渗性能所造成的负面影响全部被抵消。     

改性拜耳法赤泥对钢渣活性激发的研究

选用改性赤泥和水泥熟料作为激发剂,重点研究改性赤泥掺量对钢渣活性的影响。利用XRD和SEM对水化产物和微观形貌进行分析。研究表明,改性赤泥中的可溶性碱能够促进钢渣中的硅铝质活性矿物溶解,有效的提高了钢渣胶凝材料后期强度。后期强度的提高主要是由于水化产物中生成了絮状的C-S-H凝胶,以及片状的物质,但片状物质之间孔隙较多,导致强度提高不明显。综合考虑力学性能、流动性能,改性赤泥的掺量不宜超过8%。     

碱赤泥矿渣胶凝材料性能的研究

本文用水玻璃激发赤泥和矿渣而得到了高强的无机胶凝材料———碱赤泥矿渣胶凝材料。研究了赤泥掺量、水玻璃品种和掺量以及磷酸钠的掺量对这种胶凝材料强度的影响。通过正交试验确定了其最佳的质量配比。使用XRD分析了碱赤泥矿渣胶凝材料水化过程中的水化产物     

利用膨润土的膨胀和稠度特性对GCL渗透系数进行预测的试验研究

以土工合成粘土衬垫(Geosynthetic Clay Liner,GCL)在尾矿库防渗层中的应用为背景,研究不同浓度重金属离子(Cu和Zn)作用下,膨润土的自由膨胀量、液限及GCL渗透系数的变化规律,并分析它们之间的对应关系。试验结果显示,当重金属离子浓度在0.01mol/L到0.1mol/L之间递增时,膨润土的自由膨胀量和液限会随着重金属离子浓度的增大而大幅度减小,但当重金属离子浓度从0.1mol/L增加到0.5mol/L时,膨润土的自由膨胀量和液限则只有微小变化。在渗透试验中,当渗透溶液中重金属离子浓度小于0.01mol/L时,GCL的渗透系数能够保持稳定;但当重金属离子浓度大于0.02mol/L后,GCL的渗透系数会随着渗透溶液中重金属离子的浓度增加而不断升高。研究结果表明,当尾矿库渗滤液中重金属离子浓度大于0.02mol/L时,GCL的渗透系数与膨润土的自由膨胀量和液限之间具有良好的数学对应关系,可以利用自由膨胀量和液限对渗透系数进行预测。     

物理改性赤泥替代矿粉对沥青胶浆性能的影响

将赤泥作为填料制成沥青胶浆评价其替代矿粉的可行性,并使用消石灰、造纸白泥等材料对赤泥进行物理改性。通过软化点、直接拉伸试验、布洛克菲尔德黏度试验,对沥青胶浆的高温性能、低温性能、粘滞性能进行评价。     

改性膨润土作为垃圾填埋场防渗材料的研究

对膨润土与改性膨润土作为垃圾填埋场防渗层材料研究进展进行简要介绍;重点阐述聚丙烯酰胺改性膨润土的研究现状,分析聚丙烯酰胺改性膨润土作为垃圾填埋场土工合成材料的可行性.     

赤泥活性改进及其对水泥熟料性能的影响研究

将赤泥焙烧活化应用到水泥基材料中是高效消纳赤泥的有效途径,对赤泥活性改进及其对水泥熟料性能的影响进行了研究.结果表明:赤泥在500℃焙烧处理60 min后的活性激发效果最明显,可以有效提高活性;在水泥熟料中掺加经活化后的赤泥,体系的早期强度降幅较小,但随其掺量增加,胶砂的抗压强度下降明显;掺外加剂A可以提高赤泥-水泥熟...     

赤泥-硫铝酸盐水泥高水充填材料性能及对环境的影响

利用赤泥和硫铝酸盐水泥制备高水充填材料,实现赤泥的有效资源化利用。研究了赤泥掺量对高水充填材料性能的影响。结果表明,随着赤泥掺量的增加,高水充填材料的初凝时间延长,抗压强度有所降低,赤泥掺量达到50%时,浆体初凝时间延长至61 min,28 d抗压强度降至5.0 MPa,但仍满足高水充填材料的需求;随着赤泥掺量的增加,硬化浆体析水率和孔隙率略微增加,渗透性显著提高。赤泥中的碱金属可以促进硫铝酸钙的水化,K和Na参与硫铝酸钙的水化形成U相,水化龄期到7 d时得以有效固化。硬化浆体的放射性符合GB 6656—2010的要求。     

土工格室填料类型对其加固性能的影响研究

以室内承载板试验为依据建立数值分析模型,研究黏性土为土工格室填料的适用性。通过计算砂土换填这一工况,揭示了土工格室加固路基中(砂土是格室填料)土工格室和砂土的贡献占比。结果表明,采用与路基填料一致的黏性土作为土工格室填料时,从路基承载力和竖向变形的角度分析,土工格室的加固效果微弱,而采用砂性土作为土工格室填料,加固性能提升明显。此外,土工格室对路基的加固效果和变形有着很大的关系,只有发生足够大的侧向变形时,土工格室的侧限效应才能够得到充分的发挥。     

改性纳米二氧化硅对水泥砂浆性能影响的研究

纳米二氧化硅在水泥基复合材料中具有极大的潜力,但纳米颗粒在水泥基材料中的团聚问题限制了其发展。通过采用硅烷偶联剂对纳米二氧化硅进行改性,进而在其表面接枝异丁烯醇聚氧乙烯醚(TPEG),合成一系列改性纳米二氧化硅。试验结果表明,经TPEG改性后的纳米二氧化硅在碱性环境中有着更高、更稳定的分散性。相比于纳米二氧化硅,改性纳米二氧化硅可以更好地调控水泥水化进程并提高砂浆的物理力学性能。     

粘土掺量对赤泥烧结砖性能的影响

利用赤泥制备了抗压强度达到国家烧结砖标准中MU30级要求的烧结砖,并研究了粘土掺量对赤泥烧结砖性能的影响。研究表明粘土的掺入能改善坯料的可塑性,增大烧结砖的收缩,扩大烧结砖的烧结温度范围,提高烧结砖的抗压强度。     

Effect of gravel subgrade on hydraulic performance of geosynthetic clay liner

The effect of a gravel subgrade on the hydraulic performance of GCLs is investigated. Laboratory test results show that the GCL specimens exhibit significant variation in thickness when compressed against gravel. The maximum and minimum thicknesses of the specimen were about 20 and 3 mm, respectively, after consolidation by an effective stress up to 138 kPa. However, the permittivity of GCLs remained very low. The permittivity of both needle-punched and adhesive-bonded geotextile-supported GCLs decreased with increasing confining stress, regardless of the type of subgrade materials. In general, larger particles led to more significant migration of bentonite. Nevertheless, there was no significant difference in the degree of bentonite migration between the two GCLs investigated.     

Barrier properties of a geosynthetic clay liner using polymerized sodium bentonite

The hydraulic and swelling properties of a polymerized bentonite (PB), and the self-healing capacity of a geosynthetic clay liner (GCL) using the PB as the core material (PB-GCL) were investigated experimentally. Five different test liquids included of deionized water, NaCl solutions (0.1 M and 0.6 M) and CaCl₂ solutions (0.1 M and 0.6 M) were used in this study. The PB exhibited a higher free swelling index (FSI) than that of the untreated bentonite (UB) for all test liquids. For permeability test, under a given void ratio (e), the value of k of the PB is much lower than that of the UB in NaCl and CaCl₂ solutions. The PB-GCL specimens demonstrated a higher self-healing capacity than that of the corresponding GCL specimens using the UB (UB-GCL). Specifically, when using a 0.6 M CaCl₂ solution for a 20-mm-diameter damage hole, the UB-GCL specimen provided a zero healing ratio (healed damage area/total damage area), but the PB-GCL specimen demonstrated an approximately 76% healing ratio. The results from this study indicate that the PB-GCL provided better barrier performance against cationic liquids with higher cation valence and concentrations compared to that of the UB-GCL.     

Chemical interaction and hydraulic performance of geosynthetic clay liners isothermally hydrated from silty sand subgrade

The effects of the silt aggregation, compaction density, and water content of the subgrade on the hydration of five different geosynthetic clay liner (GCL) products is reported based on a series of laboratory column experiments conducted over a six-year period. GCLs meeting typical specifications in terms of minimum hydraulic conductivity and swell index are hydrated to equilibrium from the same subgrade soil with sufficient cations to cause cation exchange during hydration. It is then shown that the GCL bentonite granularity and GCL structure can have a significant (~four orders of magnitude) effect on hydraulic conductivity under the same test conditions (from 8 × 10⁻¹² m/s for one GCL to 6 × 10⁻⁸ m/s for another GCL product). The effect of subgrade water content on the hydraulic performance of GCLs are not self-evident and quite dependent on the bentonite granularity, GCL structure, and permeant. Varying the subgrade water content from 5 to 16% and allowing the GCL to hydrate to equilibrium before permeation led to up to 5-fold difference in hydraulic conductivity when permeated with tap water and up to 60-fold difference when the same product is permeated with synthetic municipal solid waste leachate. When permeated with synthetic leachate, increasing stress from 70 kPa to 150 kPa led to a slight (average 37%; maximum 2.7-fold) decrease in hydraulic conductivity due to a decrease in bulk void ratio. It is shown that hydraulic conductivity is lower for GCLs with a scrim-reinforced geotextile, and/or with finer bentonite. It is shown that selecting a GCL based on the initial hydraulic conductivity and swell index in a manufacturers product sheet provides no assurance of good performance in field applications and it is recommended that designers pay more attention to selection of a GCL and preparation of the subgrade for important projects.     

赤泥作水泥掺合料的试验研究

运用X衍射分析方法,分析了赤泥的矿物组成,表明赤泥含有潜在活性的物质;采用SEM分析了赤泥的形态,表明赤泥有较好的填充形态;通过水泥胶砂强度试验,表明掺未煅烧赤泥的最佳掺量为5%左右,最大掺量为10%～15%;而600℃煅烧的赤泥具有较好的活性,在20%掺量以下具有较高的强度,最大掺量可达30%左右。     

改性灰缝含水率对土坯砌块抗压强度影响的试验研究

为改进新疆传统民居中常用的素土坯砌块的粘结性能,制作素土泥浆和素土中分别掺和麦秸秆、粗砂、生石灰的改性泥浆.参照砌体抗压强度试验标准,制作了使用4种泥浆作为灰缝的素土坯试块.通过试块的抗压强度试验,研究其抗压强度,得出了改性灰缝不同含水率对试块强度的影响.试验结果表明,通过对灰缝改性并控制含水率,可提高试块抗压强度.     

氨氮在土工合成黏土衬垫中的扩散行为研究

氨氮是垃圾渗滤液中最具代表性的污染物之一,但其在土工合成黏土衬垫(GCL)中的扩散行为至今尚未得到重视。开展批式吸附试验和扩散试样浸提试验测定氨氮在GCL中的吸附分配系数;进行扩散试验测定氨氮在GCL中的扩散系数;基于试验得到的吸附分配系数和扩散系数,使用数值软件POLLUTE v7.0对氨氮在GCL中的运移行为进行模拟。试验结果表明,氨氮在膨润土上的吸附分配系数为0.017L/g,在GCL中的扩散系数约为9.0×10^-11m²/s。POLLUTE v7.0的模拟结果显示,当考虑扩散存在时,氨氮将提前30 a击穿GCL。     

Failure mechanisms of geosynthetic clay liner and textured geomembrane composite systems

The objective of this study was to evaluate shear behavior and failure mechanisms of composite systems comprised of a geosynthetic clay liner (GCL) and textured geomembrane (GMX). Internal and interface direct shear tests were performed at normal stresses ranging from 100 kPa to 2000 kPa on eight different GCL/GMX composite systems. These composite systems were selected to assess the effects of (i) GCL peel strength, (ii) geotextile type, (iii) geotextile mass per area, and (iv) GMX spike density. Three failure modes were observed for the composite systems: complete interface failure, partial interface/internal failure, and complete internal failure. Increasing normal stress transitioned the failure mode from complete interface to partial interface/internal to complete internal failure. The peak critical shear strength of GCL/GMX composite systems increased with an increase in GMX spike density. However, the effect of geotextile type and mass per area more profoundly influenced peak critical shear strength at normal stress > 500 kPa, whereby an increase in geotextile mass per area enhanced interlocking between a non-woven geotextile and GMX. Peel strength of a GCL only influenced the GCL/GMX critical shear strength when the failure mode was complete internal failure.