水泥固化镍污染土的压缩特性试验研究

通过压缩试验,探讨了不同镍离子浓度、不同水泥掺量的水泥固化镍污染土的压缩特性,分析了水泥固化镍污染土的压缩指数Cc、压缩模量E_(s1-2)与镍离子浓度和水泥掺量的关系,结果表明,污染土中镍离子浓度越高,固化土的结构性越差,压缩指数C_c、压缩模量E_(s1-2)越低;随水泥掺量增大,镍离子含量较高的水泥固化污染土的压缩指数C_c和压缩模量E_(s1-2)增长幅度明显。     

水泥固化锌离子污染土力学特性试验研究

水泥固化重金属污染场地在工程实践中取得了较好的处治效果,然而不同类型的重金属离子,由于其化学性质的差异,其相应的固化体物理力学性质也不同。本文基于锌离子污染土样,通过室内试验研究了不同浓度的污染物掺量下土样的强度及压缩特性,同时采用不同掺量的水泥对污染土样进行固化处理,并进行了相关强度及压缩试验。试验结果表明:锌离子会引起土样强度及压缩特性的劣化,但劣化程度较小,且离子浓度对其劣化程度影响较小;采用水泥对重金属污染土样进行固化,土的强度及压缩特性会显著增大,并随着水泥掺量的增加而提高;锌离子会显著抑制水泥的固化过程,当锌离子浓度达到1.25%时,7.5%的水泥掺量不能有效增强固化体强度及压缩特性。     

水泥固化重金属污染土的淋滤特性试验研究

固化稳定法是目前处理重金属污染土场地的常用方法之一。经过处理后的污染土,不仅在强度上有所提高,而且重金属污染离子亦能被有效固化稳定下来。目前,这方面的研究成果主要集中在固化污染土的工程性质变化方面,而对固化土中的重金属离子的滤出特性研究较少。通过系统的室内试验,以经水泥固化后的铅和锌污染土为研究对象,着重研究固化污染土中重金属离子的淋滤特性。试验结果表明:水泥固化重金属污染土后,随着固化剂掺量和养护龄期的增加,重金属的滤出率显著降低,并最终趋于稳定。在污染物掺量较低时,水泥对Pb2+的固化效果好于对Zn2+的固化效果;随着污染物掺量的增加,滤出液中Pb2+浓度的增幅要大于Zn2+浓度增幅。在污染物掺量较高时,水泥对Zn2+的固化效果好于对Pb2+的固化效果。     

水泥固化重金属污染土的淋滤特性试验研究

固化稳定法是目前处理重金属污染土场地的常用方法之一。经过处理后的污染土,不仅在强度上有所提高,而且重金属污染离子亦能被有效固化稳定下来。目前,这方面的研究成果主要集中在固化污染土的工程性质变化方面,而对固化土中的重金属离子的滤出特性研究较少。通过系统的室内试验,以经水泥固化后的铅和锌污染土为研究对象,着重研究固化污染土中重金属离子的淋滤特性。试验结果表明:水泥固化重金属污染土后,随着固化剂掺量和养护龄期的增加,重金属的滤出率显著降低,并最终趋于稳定。在污染物掺量较低时,水泥对Pb2+的固化效果好于对Zn2+的固化效果;随着污染物掺量的增加,滤出液中Pb2+浓度的增幅要大于Zn2+浓度增幅。在污染物掺量较高时,水泥对Zn2+的固化效果好于对Pb2+的固化效果。     

上海软黏土压缩特性的试验研究

为研究结构性对上海软黏土压缩特性的影响,利用单向高压固结仪,对取自上海不同地点的3种软黏土的原状样及相应的重塑样进行了大量的一维主固结和次固结试验。主固结试验结果表明:结构性的存在使原状样的压缩曲线位于重塑样的上方,具有明显的结构屈服应力;结构屈服应力的大小与取样方式密切相关,现场直接切取试样的压缩曲线的结构屈服应力点最明显,应力值最大,厚壁样的压缩曲线则几乎没有屈服应力点。次固结试验结果表明:结构性的存在使原状样的次固结系数与固结压力密切相关,且次固结系数最大处的固结压力为结构屈服应力的1.5~2.5倍,而正常固结状态的重塑样的次固结系数与固结压力几乎无关。最后,正常固结状态下上海软黏土的次固结系数分布范围表明,其次压缩性为中等至高等,次固结系数与压缩指数的比值Ca/Cc表明,上海软黏土为无机质黏土及粉土。     

结构性软土力学特性的试验研究

对扰动程度不同的原状样和重塑样分别进行单向固结试验和固结排水及不排水三轴剪切试验,研究结构性对上海软土的变形、强度特性的影响。压缩试验结果表明:结构性强的原状样具有明显的结构屈服应力,结构性一般的原状样,结构屈服应力不明显;原状样比重塑样具有更大的压缩指数Cc和膨胀指数Cs。剪切试验结果表明:相同固结压力下,结构性强的土样强度不仅低于结构性弱的土样强度,而且低于重塑样的强度。这是由剪切时土样的孔隙比差异造成的。若消除孔隙比的影响,则结构性将使原状样具有更高的强度,且结构性越强,土体强度越高。     

水泥固化法处理重金属污染土的强度特性研究

通过室内无侧限抗压强度试验,对水泥固化稳定后的重金属镍污染土的强度特性进行了研究,并对不同镍离子浓度、水泥掺入量和龄期对水泥固化土强度特性的影响进行了分析,对比分析了不同重金属离子对水泥固化土强度特性的影响,最终得到了水泥固化土强度预测公式。     

水泥加固酸污染土无侧限强度特征

污染土是利用水泥固化处理后,土体的强度得到提高。针对该项技术,采用水泥固化法处理酸污染土,通过两种试验方案,对水泥加固酸污染土的无侧限抗压强度特性进行研究。试验所用酸污染土用浓硫酸配置人工制备而成,并考虑了不同水泥掺量、不同硫酸浓度和不同龄期对水泥加固酸污染土强度的影响。试验表明:水泥固化酸污染土的强度与水泥掺量和硫酸含量有密切关系,二者共同作用决定其强度的变化。在一定硫酸浓度(2~16g/kg)条件下,伴随硫酸含量的升高,水泥掺量较低时,无侧限抗压强度整体呈明显下降的趋势;水泥掺量较高时,无侧限抗压强度呈缓慢上升的趋势。随着水泥掺量提高,土样的无侧限抗压强度达到峰值时所对应的硫酸含量也逐渐变大。     

水泥固化重金属铅污染土的强度特性研究

污染场地中开挖出来的污染土利用水泥固化处理（S/S法）后,其污染物质的淋滤特性和土体的强度得到改善,可用于场地的回填和堤坝的填筑等。针对该项技术,对水泥固化稳定后的重金属铅污染土的强度特性进行了研究。试验所用的铅污染土通过将硝酸铅溶液加入干土中人工制备而成,并考虑了不同铅离子含量和水泥掺量对水泥固化污染土强度特性的影响。试验结果表明：水泥固化污染土的无侧限抗压强度随着水泥掺量以及龄期的增长而提高;与常规水泥土（不含重金属污染物）强度相比,污染土中铅离子含量较低时,强度略有提高,铅离子含量较高时,强度显著降低;不同铅含量水泥土试样的应力应变关系均表现为强度越高,破坏应变越小;试样28 d龄期的变形模量与强度呈较好的线性对应关系。     

水泥固化铜污染土的强度特性及机理研究

随着中国城市化进程的不断加快,城市工业场地的重金属污染程度也在加剧。地基土受到重金属污染后,其工程性质会发生改变。固化稳定法是处理重金属污染土地基的常用方法之一。针对该项技术,本文试验研究了铜离子掺量、水泥掺量以及养护龄期对固化污染土的强度特性的影响,并对固化机理进行了分析。试验结果表明:当铜离子掺量低于0.3%时,随着铜离子掺量的增加固化污染土强度变化不大;当铜离子掺量达到0.5%时,土体强度显著下降;但随着水泥掺量及养护龄期的增加,土体强度会有一定程度的提高。     

水泥加固软土的室内试验研究

以某工程的软土为原料，进行了一系列水泥土的物理、强度试验，分析了含水量、水泥用量和龄期对水泥土强度的影响，提出了水泥加固该种软土的最小水泥用量值，该结论对我国其他地区软土的加固具有重要的借鉴意义。     

粉煤灰炉渣加固土的室内无侧限抗压强度试验研究(英文)

给出了用粉煤灰、炉渣等工业废料加固土的室内无侧限抗压强度试验结果,分析了加固土无侧限抗压强度与外加剂掺量、养护龄期之间的影响规律,得出了针对不同工业废料加固土所用外加剂的最佳掺量。     

Basic parameters governing the behaviour of cement-treated clays

Although extensive research has been conducted on the mechanical behaviour of Portland cement-treated soft clays, there has been less emphasis on the correlation of the observed behaviour with clay mineralogy. In this study, experimental results from the authors have been combined with the data found in the literature to investigate the effect of parameters such as curing time, cement content, moisture content, liquidity index, and mineralogy on the mechanical properties of cement-treated clays. The findings show that undrained shear strength and sensitivity of cemented clays still continue to increase after relatively long curing times; expressions are proposed to predict the strength and sensitivity with time. This parametric study also indicates the relative importance of the activity of the soil, as well as the water–cement ratio, to the mechanical properties of cementitious admixtures. Two new empirical parameters are introduced herein. Based on the results of unconfined compression, undrained triaxial, and oedometer tests on cement-enhanced clays, expressions that use these parameters to predict undrained shear strength, yield stress, and the slope of the compression line are proposed. The observed variations in the mechanical behaviour with respect to mineralogy and the important effect of curing time are explained in terms of the pozzolanic reactions. The possible limitations of applying Abrams׳ law to cement–admixed clays are also discussed.     

Incorporation of a nanotechnology-based additive in cementitious products for clay stabilisation

The mechanical performances and water retention characteristics of clays, stabilised by partial substitution of cement with by-products and inclusion of a nanotechnology-based additive called RoadCem (RC), are studied in this research. The unconfined compression tests and one-dimensional oedometer swelling were performed after 7 d of curing to understand the influence of addition of 1% of RC material in the stabilised soils with the cement partially replaced by 49%, 59% and 69% of ground granulated blast furnace slag (GBBS) or pulverised fuel ash (PFA). The moisture retention capacity of the stabilised clays was also explored using the soil-water retention curve (SWRC) from the measured suctions. Results confirmed an obvious effect of the use of RC with the obtained strength and swell properties of the stabilised clays suitable for road application at 50% replacement of cement. This outcome is associated with the in-depth and penetrating hydration of the cementitious materials by the RC and water which results in the production of needle-like matrix with interlocking filaments – a phenomenon referred to as the ‘wrapping’ effect. On the other hand, the SWRC used to describe the water holding capacity and corresponding swell mechanism of clays stabilised by a proportion of RC showed a satisfactory response. The moisture retention of the RC-modified clays was initially higher but reduced subsequently as the saturation level increased with decreasing suction. This phenomenon confirmed that clays stabilised by including the RC are water-proof in nature, thus ensuring reduced porosity and suction even at reduced water content. Overall, the stabilised clays with the combination of cement, GGBS and RC showed a better performance compared to those with the PFA included.     

Geotechnical characterization of a clay–cement mix

Soft clay deposits are highly plastic, normally consolidated fine grained soils characterized by their low inherent shear strength. The mixing of soft clays with cement as a chemical stabilizer has become a well-known stabilization technique. The resulting strength of the clay–cement mix is controlled by different factors, but mainly the water to cement ratio, the cement content, and the curing conditions. It is crucial to develop a clear understanding of the changes in engineering behavior of the clay–cement mix that result from changes in controlling factors. A phase diagram was established to define the initial conditions of the mass–volume relationships of air, cement, clay, and water of a typical clay–cement mix. This phase diagram was then used to determine the total dry density, void ratio, and specific gravity of the clay–cement mix as a function of the cement content and water to cement ratio. The main objective of this work was to develop generalized trends for the geotechnical properties of clay–cement mixes. These trends were evaluated based on unconfined compressive strength as well as consistency tests carried out on soft clay samples before and after mixing with cement and at different curing times. A reduction in the plasticity index (PI) of 16 % and an increase in the unconfined shear strength of more than 200 kPa were obtained from the addition of 15 % cement. The reduction in the PI of the clay–cement mix was found to be an efficient tool to represent the improvement in the strength of the clay after mixing with cement.     

水泥固化锌污染高岭土强度及微观特性研究

采用水泥作为固化剂对锌污染高岭土进行固化稳定处理,对固化后养护7 d和28 d的人工锌污染土的液塑限特性,无侧限抗压强度和变形模量特性,土样pH特性,以及微观机理进行了研究.结果表明,液塑限随锌离子浓度增加而降低.随锌离子浓度增加,固化污染土的无侧限抗压强度值总体均呈下降趋势;随试样pH值升高,无侧限抗压强度值增大;变形模量E₅₀均随锌离子浓度增大而减小;水泥的主要水化产物的数量均随锌离子浓度的增加而减少,且由成熟形态向早期形态退化,并最终消失.随着锌离子浓度的增加,试样中的直径1～10 μm的孔隙数量明显增加,并且伴随着直径0.01～1 μm的孔隙数量的减小.     

Modeling compression behavior of cement-treated zinc-contaminated clayey soils

In this paper, the compression behavior of cement-treated soil with various cement contents and zinc concentrations is presented and modeled by the destructuring framework and the concept of the Intrinsic Compression Line (ICL). The void ratio of a cement-treated sample with Zn contamination is the sum of the void ratio sustained by the intrinsic soil fabric (destructured void ratio) and the additional void ratio due to cementation. The compression index at the pre-yield state, C_s, increases as the Zn concentration increases or as the cement content decreases. At the post-yield state, the additional void ratio is inversely proportional to the effective vertical stress. The rate of reduction in the additional void ratio is controlled by the destructuring index, b. The values for b and yield stress are mainly dependent upon the degree of cementation, which is controlled by the cement content and the Zn concentration. Based on a critical analysis of the test data, a practical (simple and rational) method for assessing the compressibility of cement-treated soil with various Zn concentrations is suggested. The proposed predictive method is useful not only for quickly determining compression curves, with acceptable errors, but also for examining the results of tests on cement-treated zinc-contaminated soil.     

有机质含量对水泥土强度的影响及对策

采用有机质含量比较高的盐城泻湖相软土进行了大量的水泥土加固室内试验，并对试验结果进行了分析，得到了强度随龄期增长的公式，并探讨了有机质对强度的不利影响，提出了抵抗有机质含量对水泥土强度影响的对策。     

低浓度疏浚淤泥透气真空泥水分离模型试验研究

基于高含水率疏浚淤泥堆场透气真空快速泥水分离方法的专利,设计研制了大型透气真空模型装置。对含水量高达液限3倍以上的疏浚淤泥进行了泥水分离试验研究。结果表明:透气真空技术能够使高含水量淤泥实现快速泥水分离,只需10d时间,淤泥的体积可以减少三成以上,连续抽水一个月左右时的淤泥泥面沉降的应变速率仍达3%/d。基于模型试验结果,还分析了淤泥平均含水量、淤泥泥面沉降速率、尾水悬浮物浓度的变化规律,发现沉降速率与淤泥平均含水量密切相关,尾水悬浮物浓度远低于规范规定的一级排放标准值。     

腐殖酸与盐分浓度对石灰加固土有明黏土的影响以及微观结构研究

首先从力学性质方面考察了有机质之一的腐殖酸和盐分浓度对于石灰加固土的影响。分析的结果显示对于腐殖酸含量较高的黏土由于凝硬反应被阻碍使得加固土的强度与屈服应力较小,并且由于盐分浓度较高时腐殖酸活性降低,因此随着盐分浓度的增加腐殖酸对于石灰加固土的影响减小。然后通过分析加固土的微观结构,我们讨论了石灰加固土的力学性质与微观结构之间的关联性。