EPS颗粒混合轻量土无侧限抗压强度特性试验研究

为研究EPS颗粒混合轻量土的密度、强度和变形特性,对不同水泥掺量、EPS颗粒掺量、含水率和龄期的轻量土进行密度无侧限抗压强度试验。试验配置轻量土无侧限抗压强度范围为103.2~1359.0 kPa,且随水泥掺量的增大呈指数关系增大的趋势,随EPS颗粒体积比的增大而呈线性关系减小的趋势。在大于最优含水率情况下,含水率越高,无侧限抗压强度越低,两者为指数关系,而龄期的增长能够使得轻量土的无侧限抗压强度呈双曲线增大的趋势。EPS颗粒混合轻量土的应力-应变关系曲线主要表现为应变软化型,含水率和EPS颗粒体积比的增大会使得轻量土的应力-应变关系曲线逐渐向硬化型转化。水泥掺量和龄期的增大能够增强轻量土的脆性特征,增大刚度。而含水率和EPS颗粒体积比的增大则使得轻量土的延性特征增强,刚度减小。研究成果对实际工程应用具有参考价值。     

淤泥EPS颗粒混合轻质土黏聚力的一种计算方法

在疏浚淤泥中添加固化材料和EPS颗粒制作成淤泥EPS颗粒混合轻质土,既可以资源化利用疏浚淤泥,又生产一种轻质高强的土工材料。强度是EPS颗粒混合轻质土最重要的工程特性之一,建立抗剪强度参数与原材料的性质和配比之间的关系式对于配方初步设计非常重要。EPS颗粒混合轻质土强度的形成是固化材料的固化作用和EPS颗粒的置换效应的综合表现,固化作用已经较为明确,置换效应的研究是确定强度的核心。在已知固化土(水泥土)的弹性模量和泊松比的前提下,针对EPS颗粒的置换效应,根据其剪切面上力的等效关系和变形协调关系以及EPS颗粒的物理关系建立了其黏聚力与EPS颗粒密度和添加量之间的关系式,利用原材料的性质对计算方法进行了简化;利用直接剪切试验获取了淤泥EPS颗粒混合轻质土的黏聚力,验证了上述关系式。     

含盐量对石灰固化滨海盐渍土力学强度影响试验研究

随含盐量的增加,滨海盐渍土中的盐分结晶形成了许多晶体颗粒,改变了土的颗粒级配和微结构形式,使土的力学强度发生变化。无侧限抗压试验和三轴压缩试验结果表明,随含盐量的增加,石灰固化土的无侧限抗压强度和抗剪强度降低;随养护龄期的增加,石灰固化土的无侧限抗压强度和抗剪强度增加;随含盐量的增加,固化土试样浸水和不浸水无侧限抗压强度之间的差值越来越小。工程应用滨海盐渍土时需控制土的含盐量。     

初始含水率对风化砂改良膨胀土无侧限抗压强度的影响

利用风化砂对膨胀土进行了物理改良处理,在验证这一改良方法对提高膨胀土力学指标的可行性的同时,通过改变试验时的初始含水率,深入探讨了膨胀土的无侧限抗压强度随初始含水率和风化砂掺量的变化规律。试验研究表明:1掺入适量的风化砂对膨胀土力学指标的提高效果较为显著,综合考虑风化砂掺量对各项力学指标的影响,当风化砂掺量为10%时效果最好;2当风化砂掺量相同时,无侧限抗压强度随着初始含水率的增大先增大后减小,当初始含水率略大于最佳含水率1%~2%时所对应的无侧限抗压强度最大;3风化砂掺量对膨胀土无侧限抗压强度的影响较大,当初始含水率相同时,无侧限抗压强度随着风化砂掺量先增大后减小,当风化砂掺量为10%时,各初始含水率下的无侧限抗压强度均达到最大,且无侧限抗压强度与风化砂掺量满足四次函数的关系;4综合考虑风化砂掺量和初始含水率对膨胀土无侧限抗压强度的影响,得出当风化砂掺量为10%、初始含水率为14%时,风化砂改良膨胀土的无侧限抗压强度达到最大值。     

活性氧化镁−微生物固化黄土试验研究

以活性氧化镁和微生物共同作用固化的黄土试样为研究对象,通过含水率、无侧限抗压强度、X射线衍射（XRD）和扫描电镜（SEM）等试验,研究了活性氧化镁掺量、养护龄期和初始含水率对固化试样含水率、无侧限抗压强度、固化产物和微观结构等的影响。结果表明：固化试样含水率随氧化镁掺量增加和养护龄期增长而降低;无侧限抗压强度随活性氧化镁掺量（5%～20%）增加而增大,随龄期发展总体上不断增大,但当氧化镁掺量为10%和15%时,后期强度稍有降低;当氧化镁掺量为5%和10%时,无侧限抗压强度随初始含水率增加而减小,而当氧化镁掺量为15%和20%时,无侧限抗压强度随初始含水率增加先增大后减小。XRD和SEM结果显示,随着氧化镁掺量增加,水化后未进一步反应的氢氧化镁越多;反应生成的水合碳酸镁具有膨胀性和胶结性,对土颗粒间缝隙进行填充,并将土颗粒胶结在一起。     

砂土EPS颗粒混合轻质土的物理力学特性

对以砂土为原料土、以水泥为固化材料的EPS颗粒混合轻质土进行了一系列室内试验。结果表明：压实条件和含水率对其密度和强度有很大的影响,存在适宜压实次数和最优含水率;对施工含水率对其应力-应变关系的影响进行了分析,得到在水灰比一定的情况下强度与水泥的添加量的线性关系。     

植物纤维加筋固化土抗压强度和渗透试验研究

为了研究椰丝纤维和双聚高分子材料加固粉砂土的效果和机制,本文采用正交试验方法,通过掺加双聚高分子材料和椰丝纤维,针对影响加筋固化土的力学性能和渗透性的因素（椰丝纤维掺量、椰丝纤维长度和双聚材料掺量）,进行无侧限抗压强度试验和渗透试验等分析研究。研究结果表明:在粉砂土中添加双聚材料固化剂和椰丝纤维,提高了土体的无侧限抗压强度和降低了土体的渗透性。椰丝纤维含量和双聚材料掺量对试样的无侧限抗压强度影响非常显著,椰丝纤维长度对试样无侧限抗压强度的影响显著。椰丝纤维含量和双聚材料掺量对试样渗透系数的影响显著,椰丝纤维长度对渗透系数的影响不显著。当纤维掺量为0.9%,双聚材料掺量为0.375%时,试样的无侧限抗压强度最大。纤维掺量为0.9%,双聚材料掺量为0.325%时,试样的渗透系数最小。     

冻融循环对固化铅污染土强度与孔隙特征影响的试验研究

水泥基固化剂封闭是近年来重金属污染修复治理的主要技术手段之一。冻融循环作用是影响水泥固化重金属污染土力学特性的重要外营力。本文以人工制备的铅污染土为研究对象,结合冻融实验和室内土工试验,研究冻融循环作用对铅污染土无侧限抗压强度的影响。结果表明:随着水泥掺量的增大,水泥固化铅污染土的无侧限抗压强度增大,破坏应变减小;随着铅离子掺量的增大（污染程度升高）,水泥固化铅污染土的无侧限抗压强度q_u降低,应力-应变曲线变化趋势更加相似;水泥固化铅污染土的无侧限抗压强度q_u随冻融频次的增大而降低;相同冻融频次条件下,随着水泥掺量的增加,水泥固化铅污染土的无侧限抗压强度q_u损失率降低。基于SEM图像对固化铅污染土进行微观结构定量分析,表明随着冻融次数的增加,试样中细颗粒（< 1 μm）和细孔隙（< 2 μm）所占比例均提高。冻融作用对土体结构的破坏可能是导致土样无侧限抗压强度q_u降低的主要原因。     

泥岩含量对昔格达土填料路用性质的影响研究

为研究泥岩含量对昔格达土混合填料路用性质的影响,对不同泥岩含量的混合料进行重型击实、无侧限抗压强度、CBR及回弹模量试验。试验结果表明:随机混合料的最优含水率与最大干密度除受泥岩颗粒粒径、含水量及泥岩含量的影响外,主要取决于混合料中泥质粉砂岩的含量;昔格达土人工混合料室内击实结果与实际的天然随机混合料的击实结果存在显著差异,应根据实际工程混合填料中泥岩含量、含水量、板结程度及团块状泥岩量等对混合料最大干密度和最优含水量进行动态取值。当泥岩含量（质量分数) 低于65%时,混合料无侧限抗压强度随泥岩含量增加而线性增大,当泥岩含量大于65%后混合料无侧限抗压强度随泥岩含量增加而减小;混合料回弹模量值随泥岩含量的增加而增大;通过对泥岩含量与CBR值间的多项式回归分析,建立了混合料CBR值与泥岩含量的多项式回归方程,两者间相关性良好。     

固化淤泥重塑土力学性质及其强度来源

对不同水泥掺加量的固化淤泥及其重塑土进行了无侧限抗压强度试验和直接剪切试验,并对固化土和重塑土的应力-应变关系曲线、无侧限抗压强度、黏聚力和内摩擦角进行了比较分析。结果表明：随着水泥量和龄期的增加,固化淤泥的脆性增强,塑性减弱;重塑土的应力-应变关系受水泥量和龄期的影响不大,随着应变的增加,应力增长缓慢,塑性变形非常大。固化土的无侧限抗压强度、黏聚力均随着水泥量和龄期的增加而增大,而内摩擦角则有减小的趋势。重塑土相对于原状土无侧限抗压强度和黏聚力都有较大程度的折减,并且水泥量和龄期越大,折减越多;内摩擦角随着水泥量和龄期的增加有小幅度提高。重塑土强度主要来源于破碎固化土团间的摩擦和咬合作用,因此,在固化淤泥重塑土的实际工程应用中,初始固化土的处理强度不应太高。     

气泡混合轻质土干湿循环和硫酸钠耐久性试验研究

采用水泥和地聚合物作为固化剂制备气泡混合轻质土,测试水泥轻质土（LCSC）和地聚合物轻质土（LGSC）在干湿循环和硫酸钠长期浸泡环境下的无侧限抗压强度和质量变化率,并相互进行对比,分析干湿循环级数和硫酸钠浸泡环境对其强度特性的影响规律。结果表明,标准养护地聚合物轻质土强度约为水泥轻质土的2倍;干湿循环后地聚合物轻质土强度随干湿循环级数衰减较快且破坏程度逐渐增大,水泥轻质土强度未出现明显衰减,与水泥轻质土相比,地聚合物轻质土抗干湿能力较差;硫酸钠溶液浸泡120 d后,地聚合物轻质土强度出现小幅下降,约为标准养护28 d试样的80%;水泥轻质土出现开裂破坏,与水泥轻质土相比,地聚合物轻质土抗硫酸钠侵蚀能力较强。     

Evaluation of the effectiveness of olive cake residue as an expansive soil stabilizer

The quantity of the by-product olive cake residue generated in most parts of the Mediterranean countries continues to increase and expected to double in amount within 10–15 years. This increase intensifies the problems associated with the disposal of this by-product. Olive cake residue has a potential for use as a soil stabilizer and large volumes can be beneficially used. This study is directed toward determining if olive cake residue can be utilized to increase the strength and stability of expansive soils which constitute a costly natural hazard to lightweight structures on shallow foundations. A series of laboratory tests using engineering properties, such as Atterberg limits, moisture-density relationship (compaction), swell, unconfined compressive strength were undertaken to evaluate the effectiveness and performance of the olive cake residue as a soil stabilizer. Test results indicate that an addition of only 3% burned olive waste into the soil causes a reduction in plasticity, volume change and an increase in the unconfined compressive strength. However, it was observed that the presence of burned olive waste in the soil greater than 3% caused an increase in the compressibility and a decrease in the unconfined compressive strength. Test results indicate that the use of olive waste in soil stabilization gives greater benefits to the environment than simply disposing of the by-product, olive cake residue.     

The uniaxial compressive and tensile tests of frozen saturated clay in Shanghai area

The compressive and tensile strengths of frozen clay are important parameters for frozen wall design in artificial freezing excavation of tunnels and foundation pits. Up to now, nobody has conducted the compressive and tensile test of frozen clays in Shanghai area. In this paper, the unconfined compressive and tensile tests of frozen clay specimens drilled from the soil horizons 3–5 in Shanghai area were conducted in Zwick-Z020kN High-low Temperature Materials Testing Machine and Frozen Soil Triaxial Testing Machine, the corresponding constitutive equations were suggested; the temperature-unconfined uniaxial compressive strength relation was discussed; the strain rate–unconfined uniaxial compressive strength and strain rate–uniaxial tensile strength relations were studied. The relation between moisture content, dry density and unconfined uniaxial compressive strength was analyzed, too. In addition, the uniaxial compressive elastic modulus of Shanghai frozen clays and its influence factors were discussed. The research work of the current paper is very helpful for the design and theoretical studies of artificial freezing excavation in soft soil areas.     

Use of Sewage Sludge Ash and Hydrated Lime to Improve the Engineering Properties of Clayey Soils

Using various additives has been considered as one of the most common stabilization methods for improvement of engineering properties of fine-grained soils. In this research the effect of sewage sludge ash (SSA) and hydrated lime (HL) on compressive strength of clayey soil was investigated. For this purpose, 16 kinds of mixtures or treatments were made by adding different amounts of SSA; 0, 5, 10 and 15% by weight and HL; 0, 1, 3 and 5% by weight of a clayey soil. First, compaction characteristics of the treatments were determined using Harvard compaction test apparatus. So that, 12 unconfined compressive strength test specimens were made using Harvard compaction mold from each treatments taking into account four different curing ages, including 7, 14, 28 and 90 days in three replications. Therefore, a total of 192 specimens were prepared and subjected to unconfined compressive strength tests. The results of this study showed that the maximum dry density of the treated soil samples decreases and their optimum water content increases by increasing the amount of SSA and hydrated lime in the mixtures. It is also found that the adding of HL and SSA individually would increase the compressive strength up to 3.8 and 1.5 times respectively. The application of HL and SSA with together could increases the compressive strength of a clayey soil more efficiently even up to 5 times.     

石灰改良红层无侧限抗压强度试验研究

红层是一种特殊岩土,作为路基材料时,常会导致不均匀沉陷、翻浆冒泥等病害。为改善其力学性质,工程上通常掺入一定剂量的石灰（Ca（OH）₂）进行改良。由于降水-蒸发的周期性变化,运营期间反复干湿循环作用对路基土的工程性质造成较大影响。基于此,结合室内无侧限抗压强度试验,研究了干湿循环作用对不同掺量的石灰改良红层无侧限抗压强度的影响。结果表明：在最佳含水率下,石灰改良红层的无侧限抗压强度随石灰掺量的增加而增大;干湿循环作用对改良红层无侧限抗压强度的影响与石灰掺量有关,石灰掺量较低时,改良红层的抗压强度随干湿循环次数的增加而减小,石灰掺量较高时,改良红层的无侧限抗压强度随干湿循环次数的增加而显著增大;未改良红层塑性较大,试样均为塑性鼓胀破坏,掺入石灰后,红层强度增大,脆性增强,呈脆性剪切破坏,经历干湿循环作用后,石灰改良红层试样呈多缝锥形破坏。     

Development and mechanical strength properties of a new lightweight soil

The time-dependent settlement of soft soil poses serious maintenance problems to developments along coastal and riverside areas that encounter thick, soft soil deposits. To overcome this problem, therefore, a lightweight material called Air-Trapped Soil (ATS) was developed. ATS was prepared using sand produced at a factory, so its quality is highly stable. To determine the characteristics of the developed ATSs, a series of unconfined compressive and split tensile tests were conducted, and the compressive and tensile strength characteristics of the lightweight ATSs of various combinations of cement-air bubble-sand were determined. In addition, the relationship between the compressive and tensile strengths was determined. This result shows that the mechanical strength characteristics of the ATS significantly depend on the quantity of air bubbles in the ATSs.     

A geoenvironmental application of burned wastewater sludge ash in soil stabilization

This paper studied the use of burned sludge ash as a soil stabilizing agent. The sludge ash was obtained from a public wastewater treatment plant, and it was burned at 550 °C. Different percentages of burned sludge ash were mixed with three different types of clayey soil. A laboratory study consisting of Atterberg’s limits test, unconfined compressive strength test, standard proctor density test, and swelling pressure test were carried out on samples treated with burned sludge at different percentages by dry weight of the clayey soils. The results show that the addition of 7.5 % of the burned sludge ash by the dry weight of the soil will increase the unconfined compressive strength and maximum dry density and also decrease the swelling pressure and the swell potential of the soil. The addition of percentage higher than 7.5 % by dry weight of the soil decreases both the maximum dry density and the unconfined compressive strength; as a result it showed less effectiveness in stabilizing the soil. The conclusion of this research revealed that the burned sludge ash can be used as a promising material for soil stabilization.     

石灰-水泥复合土增强机制研究

利用比强度方法分析水泥土及石灰水泥土无侧限抗压强度,对石灰水泥土的增强机制进行了研究。采用内蒙古河套粉质黏土拌制水泥土及石灰水泥土试件,水泥土和石灰水泥土掺入不同量的氢氧化钙、碳酸钙和水泥,并按标准养护28 d,进行单轴抗压试验,测得水泥土及石灰水泥土的无侧限抗压强度值。研究结果表明：石灰水泥土和水泥土中存在化学胶凝和物理填充两大类作用。其中石灰水泥土中存在水化作用、硬凝作用、离子交换及团粒化作用和复合作用等4类化学增强作用;水化作用是水泥土和石灰水泥土强度增长的最主要来源;熟石灰能够抑制水化作用。