Strength Characterization of Sand-Bentonite Mixtures and the Effect of Cement Additives

This article studies the strength properties of compacted sand-bentonite landfill barrier material with and without cement addition at different periods of aging. Test results indicated that strength values, both in compression and tension, increased up to threefold in cement added samples, as well as enhancing the ductile behavior. Cubic modulus, described as the slope of the elastic portion of the cubic compressive stress versus strain curves, is determined along with initial and flexural moduli, and all the strength and moduli values were correlated with each other. Finally, it is concluded that there is a marked improvement in strength properties and moduli with cement inclusion and that the effect of aging has been very effective.     

A pan-sharpening method based on NSCT and formulated as compressive sensing problem

In this paper, a pan-sharpening method, using non-subsampled contourlet transform (NSCT) and the theory of compressive sensing (CS), is proposed. The NSCT is used for sparse image representation to perform a multiscale and directional decomposition of source images in order to express their detail and express the sparsity of their high frequency. The CS is used to merge the multispectral (MS) and panchromatic (pan) images from partial random measurements. Two different fusion rules are then applied. The final pan-sharpened image is obtained by inverse NSCT. Experimental results show the efficiency of the proposed method, compared with pan sharpening based on standard NSCT, in terms of visual quality and objective assessment. Moreover, the proposed technique is very effective when the storage and transmission bandwidth are limited.     

Influence of groundnut shell ash on strength and durability properties of clay

Groundnut shell ash, cement and their combinations are used as soil stabilizers in various percentages to improve the strength of locally available highly compressible clay soil. The effect of stabilizer in improving the strength of the soil is evaluated through change in consistency limits, compaction characteristics, undrained cohesion and modulus of elasticity. The durability characteristics of stabilised soil were studied based on the improvement of undrained shear strength for various days of curing by increasing the percentage of cement. Stabilised soil showed satisfactory improvement in strength and consistent durability characters. Groundnut shell ash and cement increased the optimum moisture content. There was a slight decrease in the dry density and modulus of elasticity of soil. These can be used as a viable economic alternative in construction of roads and for stabilising soil acting as bearing medium. The use of groundnut shell ash, an agricultural waste, helps in waste management and promotes sustainable development of local construction industry.     

饱和土变形过程模拟的统计损伤方法研究

针对传统损伤理论的不足与局限性,从研究岩土材料损伤的合理定义入手,并通过深入探讨饱和土损伤的微观力学机制,建立了适合于饱和土的新型损伤模型。在此基础上,引进统计损伤理论,建立了模拟特定围压下饱和土变形全过程的统计损伤本构模型及其参数确定方法。通过探讨饱和土损伤统计本构模型参数与围压的关系,建立了该模型的合理修正方法,从而建立了反映不同围压条件的统一饱和土损伤统计本构模型。理论与试验结果分析表明了该模型的合理性,该模型不仅能反映饱和土的变形全过程,而且能反映孔隙水压力对饱和土变形的影响。     

淤泥质酸性土水泥土强度试验研究

水泥搅拌桩加固有机质含量较高和呈酸性的土层时,我国规范建议采用现场试验的方法。通过深层搅拌法加固太湖应天河工程富含有机质的淤泥质酸性土地基的多组现场水泥土强度试验,分析了淤泥质酸性土中影响水泥土强度的各种因素。试验和工程实践表明,使用高标号水泥(525#)并掺入适量的外加剂可大幅提高酸性淤泥水泥土的强度, 复合地基承载力可达120 kPa以上,水泥搅拌桩可以加固淤泥质酸性土地基。     

有机质固化土的强度及微观结构试验研究

通过无侧限抗压强度试验对比分析了有机质含量、水泥和石膏掺量对水泥固化土和XGL2005固化土强度形成规律的影响。分析结果表明,XGL2005固化土的强度均不同程度地高于水泥固化土的强度,而且强度增长也快于水泥固化土。结合抗压强度试验和扫描电镜试验分析了固化土微观结构变化和强度发展之间的对应关系。     

基于承压板试验的岩体蠕变参数反演统一解析公式法

由于岩体性状的复杂性和多样性,现场试验是进行岩石力学研究的重要手段。以往的现场承压板试验,由于试验条件的限制,试验荷载的设定将使岩体蠕变呈衰减蠕变形态,却难以反映岩体的等速蠕变和加速蠕变。坝基软弱岩体的力学特性是影响大坝及地下结构长期稳定性的重要因素。通过对坝基软弱岩体现场承压板试验曲线中表现出的衰减蠕变和等速蠕变两阶段特性,辨识了蠕变模型。并推导了刚、柔性承压板深部岩体的黏弹性一般解,给出了Maxwell模型、广义Kelvin模型、Burgers模型的黏弹性位移的统一表达式。结合试验数据,以理论解析反演法得到相关的蠕变参数,为以后的坝基长期稳定性计算奠定基础。     

有机硅材料改性砂岩强度与ζ电位变化规律

针对干湿循环作用下岩石强度劣化引发工程岩体稳定性控制问题,以山西忻州保德煤矿8煤顶板中粒长石石英砂岩为例,对砂岩进行有机硅材料改性试验。通过单轴压缩试验研究改性前、后砂岩经历不同干湿循环作用后的强度损伤劣化规律,采用电泳法对比分析改性前、后砂岩表面ζ电位变化规律,并探讨了有机硅材料改性砂岩的改性机制。结果表明,(1)改性后砂岩的单轴抗压强度、弹性模量和变形模量明显提高,单轴抗压强度提高21.7%,弹性模量提高22.2%,变形模量提高23%;(2)受干湿循环作用砂岩强度劣化效应明显,随干湿循环次数增多,砂岩单轴抗压强度、弹性模量和变形模量均呈负指数关系降低;(3)有机硅材料对砂岩表面的电性有较大影响,随着岩样悬浮液p H值的降低,砂岩表面的负电性逐渐减弱至不带电,最后变为正电。     

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人造多晶冰三轴压缩强度特性试验研究

为研究冰的三轴强度特性,对人造宏观各向同性冰进行了不同温度和不同围压下的恒定加载速率三轴压缩试验,得到多晶冰三轴压缩的应力-应变曲线、抗压强度与温度之间的关系,利用莫尔-库仑强度准则分析了温度和围压对强度参数的影响.结果表明：轴向应变加载速率为1.67×10-4 s-1时,不同温度、不同围压下冰的应力-应变曲线均为应变...