碱侵蚀红土的工程指标与受损物质的关系探析

 常用加固材料中的碱性物质与红土中的酸性或两性氧化物发生互损侵蚀。基于材料的化学分析和加速寿命试验原理,设计红土的碱侵蚀试验。检测红土被侵蚀前后渗透液中有效离子含量的变化,以代表红土中相关物质的受损情况;对比试验红土被侵蚀前后主要的工程指标,以代表红土的工程品质劣化情况;分析并建立两者之间的关系。采用多元逐步回归分析法,量化研究碱侵蚀红土中,各项工程指标与受损化学物质之间的相关性;并依据建立的关系式,进一步探讨有效离子对红土工程性质的影响。结果表明：在碱侵蚀红土中,主要工程指标的变化均与化学物质的受损存在着显著的量化关系。分晰碱性物质对红土的侵蚀劣化机制,并可据此分析红土工程的劣化速度与趋势。     

碱性固化材料对红土地基的化学侵蚀

碱性材料的固化措施对红土地基产生了不可忽视的长期侵蚀.在岩土工程现场进行了取样和原型试验,分析了导致材料损伤的化学反应,有针对性地设计了红土的碱液加速侵蚀试验,对比讨论了化学损伤前后红土的工程支撑指标变化、红土的工程支撑离子衰减,研究了碱性固化材料在酸性红土的接触带造成损伤的机制,认为化学反应是导致红土地基寿命降低、远期效益低下,乃至诱发灾难性事故的重要原因.     

土遗址加固材料探讨

目前用于土遗址加固保护的材料众多,但对加固剂的实地选用仍无科学的依据。本文结合实践研究结果,从加固材料的物质结构、加固机理和物性特征三方面,对目前常用的水玻璃、环氧树脂、聚氨酯、有机硅树脂和硅丙乳液等加固材料进行分析。结果表明,这些材料的加固效果与物性特征在很大程度上是吻合的,结合土遗址加固保护原则,提出加固材料简单实用的选择方法。     

浅谈小型水库除险加固处理技术的应用

阐述了渗漏严重的均质土坝除险加固工程中采取的防渗、防浪、既防渗又防浪的处理措施,对复合土工膜的应用进行了初步了解,指出对渗漏严重的均质土坝宜通过坝体和坝基防渗来保证大坝的渗流安全稳定,采用土工合成材料处理小型水库有推广价值。     

劣化古建砖石砌体的微生物注浆加固试验研究

微生物灌浆加固劣化砌体结构是在不适合使用石灰、水泥和环氧树脂等传统灌浆材料情况下,在被加固空腔内原位填充颗粒,使其作为加固材料的骨架,并通过注入微生物和胶凝溶液的方法,在填充颗粒孔隙内诱导生成碳酸钙、胶凝颗粒,形成具有一定强度的微生物砂浆体。通过微生物加固实验室简化模型与现场灌浆试验等方法相结合,对高强度微生物砂浆加固各类劣化砌体的方法进行优化研究,为微生物灌浆技术应用于高质量砖石砌体文物建筑加固提供了有益的经验。     

浅谈碳纤维布加固混凝土结构的技术原理

介绍了碳纤维加固技术的特点以及所涉及的两种材料，阐述了碳纤维的补强、加固机理，分析了碳纤维布在各类混凝土结构构件加固中的机理，以使碳纤维结构加固技术得到更广泛地应用：     

CFRP及钢板复合加固震损方钢管混凝土框架结构抗整体性倒塌能力分析

为了研究CFRP及钢板复合加固震损方钢管混凝土框架结构的抗整体性倒塌能力，基于OpenSees开放平台，通过折减材料的刚度和强度模拟地震损伤，建立3榀分别为未加固、中度损伤加固和重度损伤加固的两跨三层方钢管混凝土框架结构数值模型，对其进行低周往复分析，并通过与试验结果对比验证了模型的可行性。对震损加固前后的结构数值模型进行增量动力分析，绘制出结构倒塌破坏阶段的易损性曲线，通过计算结构抗倒塌安全储备系数来评估其抗整体性倒塌能力。结果表明，未加固构件、中度损伤加固构件和重度损伤加固构件的抗倒塌安全储备系数分别为1.8、2.18、2.07,中度损伤加固构件和重度损伤加固构件的抗整体性倒塌能力较未加固构件分别恢复并得到提升21.1%和15.0%,且满足“大震不倒”要求。因此，CFRP及钢板复合加固可以有效恢复并提高震损方钢管混凝土框架结构的抗整体性倒塌能力。     

重视结构加固施工中的安全问题

根据结构加固施工的特点以及加固材料的特性，分析了结构加固施工的不安全因素，并提出了预防措施。     

无机胶凝材料粘贴碳纤维布加固混凝土结构研究进展

总结了近年来用无机胶凝材料粘贴碳纤维布加固混凝土结构的研究进展，包括各种无机胶凝材料（碱激发胶凝材料、氯氧镁水泥和水泥基复合材料）的分类与起源，碳纤维布常温与高温力学性能，以及无机胶凝材料加固混凝土结构常温与抗火性能等，指出了无机胶凝材料在加固技术中尚存在的一些问题，如各种无机胶凝材料的极限变形能力尚显不足等。分析结果表明：碱激发胶凝材料可耐600℃高温，氯氧镁水泥可耐300℃高温，且二者黏结加固效果均优于水泥基复合材料；常温下无机胶凝材料的粘贴加固效果与环氧类有机胶大体相当，高温下其加固效果明显优于环氧类有机胶，因此，用无机胶凝材料粘贴碳纤维布加固混凝土结构并以此提高结构的承载力是可行的；用无机胶凝材料粘贴碳纤维布加固混凝土结构的耐久性及其抗火设计方法等，应是今后一段时间建筑结构加固领域值得关注的课题。     

多因素耦合作用下水泥胶凝材料劣化试验方法和评价指标的探讨

为研究水泥胶凝材料在多因素耦合作用下的劣化情况,首先要拟定多因素耦合作用的试验方法和提出有效的评价指标,试验引用物理场对水泥基建筑物所处的复杂环境进行了系统分析,结合实际工程和试验设备的可操作性,从理论上探讨了切实可行的多因素耦合作用顺序;在对多因素耦合作用下水泥胶凝材料的劣化程度进行试验验证后,给出了适合多因素耦合作用下水泥胶凝材料劣化试验的必备控制条件;基于水泥胶凝材料的劣化机理,从宏观和微观两个角度对多因素耦合作用下水泥胶凝材料劣化效果的评价指标进行了探讨;最终给出了适用于多因素耦合作用下水泥胶凝材料劣化的试验流程。     

Some properties of A sedimentary laterite soil as engineering construction material

A sedimentary laterite soil is examined for its suitability as a construction material by the consideration of its mineralogy and basic geotechnical properties as well as its consolidation and permeability in the compacted state. Three compaction energy levels are utilised. Mineralogically, the soil contains virtually nothing undesirable while its basic geotechnical properties are those generally ascribed to non-problematic soils. The compressibility of the soil varies from moderate to low depending on the energy of compaction. It is however impervious for all the compaction energy levels. The sedimentary laterite soil constitute a good engineering construction material as it has already been successfully used as base and sub-base material in road construction. Results obtained in this study show that this laterite soil is also suitable for use as fill materials in embankment and dam construction.     

Stress-strain behaviour of some compacted laterite soils from north-east Brazil

Laterite soils in compacted from are widely used as fills and road construction materials in countries within the tropics. Certain unusual engineering characteristics have been established for some of them and these have been the subject of previous investigations. The present work concerns the examination of one such unusual engineering characteristic. The stress-strain behaviour of three compacted laterite soils from North-East Brazil have been examined using the shear-box machine. The investigation reveals the existence of a “collapse behaviour” previously identified only in undisturbed laterite soils. The “collapse behaviour” has been interpreted in terms of degradable soil particles which comminute under load. The comminution occurs before the ultimate failure of the soil body is reached.     

Properties of concretionary laterite gravel concrete

The compressive strength and the expansion of conrete made with both highly and slightly/moderately indurated concretionary laterite gravels were studied. The compressive strength (19–42 MPa) of most of the laterite concrete is comparable with the average strength (45 MPa) of concrete made with the usual granite crushed rock aggregates from the region. The strength of the laterite concrete is mainly dependent on the aggregate-cement bond whereas the physical properties of the aggregates are only of secondary importance. The laterite concrete showed a net contraction when immersed inhot 1N NaOH solution (i.e. rapid alkali reactivity test). This behaviour is attributed to the low/very low contents of silica, clay and lime in the aggregates. The results of the study reveal that concretionary laterite gravels are potential alternative cheap sources of aggregates for structural concrete.     

The compressibility characteristics of a compacted laterite soil

Laterite soils occupy large parts of the tropical regions of the world. They are used, in the compacted state, as bases for roads and air-field pavements, as fills for foundations, embankments and earth dams. Although the response to load with decreasing void ratio (compressibility) is important under the conditions of use, it has not been the subject of considerable study. Engineering studies in laterite soils have been limited to classification, compaction characteristics and sometimes, shear strength. The compressibility characteristics of a compacted laterite soil from Paraiba State, North-East Brazil has been examined in the oedometer. The results indicate the presence of collapsible soil grains which comminute under load. The behaviour of soil with collapsible soil grains is described.     

Basic geotechnical properties,chemistry and mineralogy of some laterite soils from S.W. Nigeria

Laterite soils derived from four basement complex rocks and a sedimentary formation from Southwestern Nigeria are analysed for their basic geotechnical properties, chemistry and mineralogy. Results obtained show that the granite gneiss derived and the sedimentary laterite soils are good engineering materials. The amphibolite derived laterite soil has a linear shrinkage of 10% and contains SO ₄ ^2? ions. The quartz schist derived and the micaschist derived laterite soils contain rather high amounts of muscovite ?30% and 25% respectively. The usability of the laterite soils and the implications of the presence of SO ₄ ^2? ions and mica and the high linear shrinkage are discussed.     

混凝土碳化模型和试验方法综述及建议

对混凝土典型的碳化模型及碳化试验方法进行了调研,比较了各种模型、试验方法或测试技术的原理和适用范围,并分析了各自的优缺点。传统混凝土碳化研究的思路和方法存在诸多局限性,不能将实验室研究较好地与现场检测结果关联起来。以耐久性劣化指标为主导的方法,为耐久性研究树立了一新概念。与碳化过程密切相关的表层混凝土的气体扩散系数、pH值与可碳化物质含量,能够反应表层混凝土被碳化的程度以及可能的劣化趋势;此外,新的测试方法摒弃了传统的破损方式,从而架起了实验室与现场研究之间的桥梁。通过将表层混凝土的渗透性与碱储备状态结合起来考虑,采用适当的碳化模型,可建立渗透性、碱含量等参数与劣化性能之间的关系,从而可较全面客观地评估混凝土的耐久性。     

Microstructural investigation on laterite soils

Considerable researches have been carried out to demonstrate the importante of microstructure in the interpretation of engineering behaviour of soils. Instances where the investigations are on laterite soils are however scanty in literature. The microstructure of laterite soils obtained from Eastern Nigeria and North-East Brazil, have been examined with the aid of optical and scanning electron microscopes. Investigations reveal the development of the well-known concretionary structure in laterite as a stage by stage process involving the accumulation of sesquioxides. The sesquioxides are accumulated initially as amorphous implantations in the pore spaces, the crystallisation of which leads to bonding of soil elements and formation of concretionary structure. The nature of cementation in the concretionary structure determines the resistance to degradation of the soils grains. The resistance to degradation would in turn influence the engineering behaviour.     

一种新型土壤强固剂加固红土试验研究

土壤强固剂是一种新型的加固土体复合材料。文中通过室内击实、直剪以及无侧限抗压强度对比试验 ,分析了一种新型土壤强固剂对云南红土的加固效果。试验结果表明 :这种新型土壤强固剂对红土样的最大干密度基本无影响 ,但可提高红土样的最优含水量 ,特别是抗剪强度和无侧限抗压强度都有显著提高 ,强度加固效果系数都大于 1,变形加固效果系数都小于 1,其加固效果优于粉煤灰。证明这种新型土壤强固剂能够显著改善土体性能 ,减小变形 ,提高土体的承载能力。