The Effect of Mineral Composition and Quantity of Fines on the Atterberg Limits and Compaction Characteristics of Soils

Because of the various elements that come into play in natural soil formation, the impact of varied proportions of mineral composition and fines amount on Atterberg limits and compaction characteristics of soils is not well known. Three distinct soil samples were used in this investigation. The findings indicated the effect of varied mineral composition proportions and fines amount on the liquid limit, plastic limit, and plasticity index as assessed by the Casagrande test and hand-rolling method. The fluctuation of maximum dry density and optimal moisture content with these three soils has also been studied. Furthermore, correlations were established to indicate the compaction parameters and the amount of minerals and particles in the soil. The data show that the mineral content of the soil has a direct impact on the Atterberg limits and compaction characteristics. Soils containing larger percentages of expansive minerals, such as montmorillonite, have more flexibility and volume change capability. Mineral composition influences compaction parameters such as maximum dry density, ideal water content, axial strain, and axial stress. Soils with a larger proportion of fines, such as Soil 2 and Soil 3, have stronger flexibility and lower compaction qualities, with higher ideal water content and lower maximum dry density. Soil 1 has moderate flexibility and intermediate compaction qualities due to its low fines percentage. The effect of different mineral compositions and fines on the Atterberg limits and compaction characteristics of soils can be used to predict the behavior of compacted soils encountered in engineering practices, reducing the time and effort required to assess soil suitability for engineering use.

Geotechnical Identification and Classification of Soils as Flexible Pavement Subgrade of the Section Fongo Tongo-Melong

The present study is inscribed within the framework of the geotechnical characterization of the soils of the Santchou plain, their classification for employment as pavement subgrade, various identification tests were carried out on the samples. The results obtained showed that with a wide range of different grain sizes, the studied soils showed low content in clay grains and dominance of either sand grains or silt grains, this can be explaining how most of these soil are poorly graded. According to the USDA textural classification, the grain size distribution of these soils makes them to be classified as Silty Loam types to Sandy Loam types. Despite of their organic matter content which is less than 10%, according to their respective methylene blue values, the soils studied along the section should be mainly loamy soil of medium plasticity to clayed soil, therefore showing a sensibility of its behavior to variation of water content. That last one is confirmed by the consistency parameters of these soils which show intermediate plasticity to highly plastic. Also, the bearing capacity proposed by these soils at their respective optimum dry densities is relatively small, although most of these experimental CBR values of the studied soils are more important than the ones prescribed by the AASHTO Classification system for A5, A6, and A7 types, and the French Highway Earthworks Manual Classifications system (GTR) for the corresponding A2 and A3 types.

Effects of Soil-Cement Stabilization on the Index Properties of Subgrades of Three Selected Roads in the Niger Delta Region of Nigeria

In this study, the impact of soil-cement stabilization on the index properties of the subgrade of roads was investigated. Efforts were on the means of improving the bearing capacity of the subgrade of a flexible pavement structure. Three selected roads (Ogbia-Nembe, section of the East-West Road and section of Port Harcourt-Aba Road) in the Niger Delta Region of Nigeria were examined to determine the effect of sand-cement stabilization on the compaction index property of their undisturbed subgrade and the optimal ratio of soil-cement on the expansive soils at which the California Bearing Ratio (CBR) is optimized. Disturbed soil samples were collected from twenty trial pits on each of the three study roads using a hand ulger and tested for their respective compaction index properties. It was discovered that their California Bearing Ratio (CBR) was very low. Some of the collected specimen materials were stabilized with varying percentages of soil-cement contents ranging from 6% - 14% in order to ascertain its effects on the compaction index properties of the sample soils. Results of the various stabilization test procedures show that: Stabilization of the soil using Soil-Cement Stabilization affected the Compaction Index properties of the soil and further improved the California Bearing Ratio (CBR). On the Ogbia-Nembe Road;Soil-Cement stabilization improved the CBR and is optimized at a 10% sand-cement ratio with optimum moisture content ranging from 6.2% - 14%, maximum dry density ranges from 1700 - 1780 kg/m3, yielding an average CBR of 42.7% for soaked samples. On the section of East-West Road from Eleme Junction to Etteh Junction;Soil-Cement stabilization improved the CBR and is optimized at a 14% sand-cement ratio with optimum moisture content ranging from 6.2% - 14.2%, maximum dry density ranges from 1660 - 1800 kg/m3, yielding an average CBR of 43.9% for soaked samples. On the section of Port Harcourt-Aba Express Road from Eleme Junction to Osisioma Junction;Soil-Cement stabilization improved the CBR and is optimized at a 12% sand-cement ratio having an optimum moisture content ranging from 5.4% - 17.3%, maximum dry density ranges from 1610 - 1740 kg/m3, and an average California Bearing Ratio for soaked samples at 40%.

Corrosion resistance of waterborne epoxy coating pigmented by nano-sized aluminium powder on steel

A novel kind of waterborne epoxy coating pigmented by nano-sized aluminium powders on high strength steel was formulated. Several coatings with different pigment volume content (PVC) were prepared. The coating morphology was observed using scanning electron microscopy (SEM), and the electrochemical properties were investigated by electrochemical impedance spectroscopy (EIS). Immersion test and neutral salt spray test were also conducted to investigate the corrosion resistance of the coating. It is demonstrated that the critical pigment volume content (CPVC) value is between 30% and 40%. The coating with PVC of 30% exhibits good corrosion resistance in 3.5% (mass fraction) NaCl solution.

掺Duroflex抗车辙剂沥青混合料性能研究

简要分析了Duroflex抗车辙剂对沥青混合料的作用机理,采用AC-16沥青混合料进行了不同Duroflex抗车辙剂掺量下的路用性能试验,分析研究了Duroflex抗车辙剂的最佳掺量,以达到提高沥青路面使用性能的目的。

Mechanism and control of water seepage of vertical feeding borehole for solid materials in backflling coal mining

To solve the problem of water seepage of vertical feeding borehole for solid materials,we established the fluid-solid coupling dynamic model of groundwater flowing in rock mass adjacent to the vertical feeding borehole.Combining with the engineering geological conditions,we built a numeral model to study the influence rule of the aquifer hydraulic pressure and seepage location of feeding borehole on the amount of seepage with fnite element numerical method.The results show that the nonlinear relationship is presented among the amount of seepage,the seepage location and aquifer hydraulic pressure.The higher the aquifer hydraulic pressure is,the closer the distance between seepage location and aquifer is,and the faster the harmful levels of aquifer will grow.In practice,we calculated the allowable seepage of feeding borehole by the optimum moisture content and natural moisture content of backflling materials,and then determined the protection zone of feeding borehole,so the moisture content of backflling materials can be controlled within the scope of optimum moisture content.

Experimental study on mechanical properties of basalt fiber-reinforced silty clay

Fiber reinforcement technology can significantly improve the mechanical properties of soil and has been increasingly applied in geotechnical engineering.Basalt fiber is a new kind of environment-friendly and highperformance soil reinforcement material,and the mechanical properties of basalt fiber-reinforced soil have become a hot research topic.In this paper,we conducted monotonic triaxial and cyclic triaxial tests,and analyzed the influence of the fiber content,moisture content,and confining pressure on the shear characteristics,dynamic modulus,and damping ratio of basalt fiber-reinforced silty clay.The results illustrate that basalt fiber can enhance the shear strength of silty clay by increasing its cohesion.We find that the shear strength of reinforced silty clay reaches its maximum when the fiber content is approximately 0.2%and the moisture content is 18.5%(optimum moisture content).Similarly,we also find that the dynamic modulus that corresponds to the same strain first increases then decreases with increasing fiber content and moisture content and reaches its maximum when the fiber content is approximately 0.2%and the moisture content is 18.5%.The dynamic modulus is positively correlated with the confining pressure.However,the change in the damping ratio with fiber content,moisture content,and confining pressure is opposite to that of the dynamic modulus.It can be concluded that the optimum content of basalt fiber for use in silty clay is 0.2%.After our experiments,we used scanning electron microscope(SEM)to observe the microstructure of specimens with different fiber contents,and our results show that the gripping effect and binding effect are the main mechanisms of fiber reinforcement.

Performance evaluation of cement-stabilized pond ash-rice husk ashclay mixture as a highway construction material

This paper reports the results of an investigation carried out on clay soil stabilized with pond ash(PA),rice husk ash(RHA) and cement. Modified Proctor compaction tests were performed in order to investigate the compaction behavior of clay, and California bearing ratio(CBR) tests were performed to determine the strength characteristics of clay. For evaluation purpose, the specimens containing different amounts of admixtures were prepared. Clay was replaced with PA and RHA at a dosage of 30%e45% and5%e20%, respectively. The influence of stabilizer types and dosages on mechanical properties of clay was evaluated. In order to study the surface morphology and crystallization characteristics of the soil samples, scanning electron microscopy(SEM) and X-ray diffraction(XRD) analyses were carried out,respectively. The results obtained indicated a decrease in the maximum dry density(MDD) and a simultaneous increase in the optimum moisture content(OMC) with the addition of PA and RHA.Multiple linear regression analysis(MLRA) showed that the predicted values of CBR tests are in good agreement with the experimental values. Developed stabilized soil mixtures showed satisfactory strength and can be used for construction of embankments and stabilization of sub-grade soil. The use of locally available soils, PA, RHA, and cement in the production of stabilized soils for such applications can provide sustainability for the local construction industry.

Evolution of Lateritic Soils Geotechnical Parameters during a Multi-Cyclic OPM Compaction and Correlation with Road Traffic

Gravel lateritic soils are intensively used in road geotechnical engineering. This material is largely representative of engineering soil all around the tropical African Countries [1,2]. Gravel lateritic soils from parts of Burkina Faso and Senegal (West Africa) are used to determine the evolution of the geotechnical parameters from one to ten cycles of modified Proctor compaction. This test procedure is non-common for geotechnical purposes and it was found suitable and finally adopted to describe how these problematic soils behave when submitted to a multi-cyclic set of Modified Proctor compactions (OPM) [3,4]. On another hand, we propose a correlation between the traffic and the cycles of compaction considered as the repeated load. From that, this work shows the generation of active fine particles, the decrease of the CBR index and also the mechanical characteristics (mainly the Young Modulus, E) that contribute at least to the main deformation of the road structure.

Use of Waste Plastic in Flexible Pavements-Green Roads

Wrappers of betel nuts, chocolates, chips, hand bags, cold drink bottles and all other forms of plastic create significant environmental and economic problem. They consume massive energy and other natural resources, depleting the environment in various ways. In manufacturing firms, construction industries and products delivery services, use of plastic is a priority to handle and pack things comfortably due to its light weight, cost effectiveness and strength. Plastics cannot be banned as it will result in usage of natural resources like paper, wood at a great extent. It is made up of various chemical elements and is regarded as a highly pestilent material which does not easily degrade in the natural environment after its usage. Waste plastics are made up of Polyethylene, Polystyrene and Polypropylene. Temperature varying between 120℃ - 160℃ gives the softening point of these plastics [5]. They do not produce any toxic gases during heating but the softened plastics have tendency to form a lamination or coating over the aggregate, when it is sprayed over the hot aggregate at 160℃. The main objective of this paper is to discuss the significance of plastic in terms of cost reduction, increase in strength and durability when these plastics are heated and coated upon the aggregates (160℃) to compensate the air voids with plastic and binds with aggregate to provide stability.

Comparison of Acidity Parameters for Soils under Perennial and Annual Pastures in Victoria

There are about 5 million ha of strongly acid soils (pH < 4.8 in 0.01 mol·L -1 CaCl 2 ) in Victoria and about 11 million ha of mildly acid soils (pH 4.8～5.5) that are considered susceptible to further acidification under current agricultural use. However, there appear to be differences in the rate of acidification, as measured by soil pH change, between soils under perennial pastures in the higher rainfall areas of southern Victoria and soils under annual pastures in the sheep-wheat areas of the north-east. Measurements made on representative soils from both regions showed that the southern soils generally had a higher pH buffer capacity, which was primarily determined by the organic carbon content. There was a consistent relationship between the short-term buffer capacity (measured by titration) and the long-term buffer capacity (measured by incubation), irrespective of the origin of the soils. Exchangeable Al, measured in 0.01 mol·L -1 CaCl 2 , was strongly negatively correlated with pH and the relationship for all soils suggested that Al was adsorbed as a cation with an average charge of 1.2

福建省水稻镁肥效应及推荐用量

【目的】明确福建省水稻主产区镁肥肥效,确定区域镁肥适宜用量,为水稻生产中镁肥科学施用提供参考。【方法】2019年10至11月份,于福建水稻主产区开展土壤调研,共采集水稻收获后土壤样品596份,测定了土壤交换性镁含量。量化了不同镁肥用量对水稻产量、经济效益的影响,采用最大经济效益法(maximum return to magnesium,MRTMg)确定福建稻区镁肥推荐用量。于2020、2021年开展了19个田间镁肥梯度试验和10个镁肥示范对比试验,镁肥梯度试验设置4个镁肥用量(以MgO计)处理,分别为:0 (CK)、15 (Mg1)、30(Mg2)和45 kg/hm^(2)(Mg3);镁肥示范对比试验设置两个处理,镁肥(以MgO计)施用量分别为0 (CK)和30kg/hm^(2)(+Mg)。调查了水稻产量。【结果】福建稻区土壤交换性镁平均含量为72.1 mg/kg,含量小于80 mg/kg的土壤样点占74%。水稻产量和经济效益随着镁肥施用量的增加而增加,与CK处理相比,Mg1、Mg2和Mg3处理下水稻产量分别增加4.9%、7.0%和7.2%,水稻纯利润分别增加4.3%、5.5%和4.6%(P<0.05)。土壤交换性镁临界阈值为80 mg/kg,当土壤交换性镁含量<80、80~120、>120 mg/kg时,镁肥最佳经济用量分别为MgO 33.2、27.3、15.8 kg/hm^(2),平均镁肥最佳经济用量为MgO 31.6 kg/hm^(2)。【结论】福建稻区土壤镁缺乏较为普遍,施用镁肥可以显著提高水稻产量及经济效益,水稻生产上需要根据土壤交换性镁供应状况确定镁肥的合理用量。

土石混合填料工程力学性能试验研究

土石混合填料力学性能是影响路堤设计和施工的重要参数,相关研究一直是热点问题。为分析不同含水率、土石混合比例、击实功、土料厚度条件下土石混合体工程力学性能,开展了不同组合下土石混合体击实试验和大型直剪试验,揭示了上述因素对混合料最优含水率和力学指标的影响,并建立了土石混合填料力学指标计算方法。研究表明:总击实功、含水率和含石量对试样干密度影响较大,且随着含石量的增大,土石混合料最大干密度逐渐增大但最优含水率逐渐降低;干密度随着每层击实次数的增加而增加;随着法向应力的增大,土石混合料应力-应变曲线由应变硬化型逐渐变为应变软化型;随着含石量的增大,其内摩擦角随之减小但黏聚力随之增大,但增大幅度较小。成果可为土石混合填料路堤施工和设计提供理论参考。

氧化铝纤维掺量及长度对混凝土力学性能和微观结构的影响

氧化铝纤维(AOF)是一种新型多晶陶瓷纤维材料,具有较好的亲水性。以AOF为改性材料,制备了氧化铝纤维改性混凝土(AOFMC),通过测试AOFMC的抗压强度、抗折强度和劈拉强度,分析了AOF掺量和长度对混凝土力学性能的影响,确定了AOF的最佳掺量和长度。在此基础上,研究了AOF对不同强度等级混凝土(C40、C50、C60)力学性能的增强作用。此外,结合扫描电子显微镜和压汞试验,分析了AOF对混凝土微观结构的影响。结果表明:AOF掺量和长度对混凝土力学性能的提高效果相互制约,当AOF长度为12 mm、体积掺量为0.2%时,AOFMC的力学性能最佳;随着强度等级的增大,AOF对混凝土力学性能的提高效果不断增大;AOF与混凝土基体结合良好,从而提高了混凝土的力学性能;在C50混凝土中,AOF主要被拔出,而在C60混凝土中,AOF部分被拉断;当AOF长度较小时,AOF可以填充混凝土内部孔隙。

荧光法测定铝溶胶中铝含量、氯含量分析方法探讨

对能量色散荧光光谱法测定铝溶胶中铝含量、氯含量进行研究。正确选择测试条件,考察温度对测定铝溶胶中元素的影响,并对准确性、重复性进行了验证。结果表明,该分析方法样品制备简单、分析速度快、操作简便、准确性较高、重复性较好,能满足铝溶胶中铝含量、氯含量的测定。

磷尾矿砂-土的击实性质及机理

利用磷尾矿砂改性黏土制备磷尾矿砂-土填料,通过击实试验对11种不同配合比的磷尾矿砂-土的击实性质进行分析,判断磷尾矿砂最佳掺量,并从级配角度分析其击实机理。结果表明,三次函数的拟合结果总体优于二次函数;随着磷尾矿砂掺量的增加,混合料的最大干密度先增加后减小,最优含水率持续减小。磷尾矿砂和黏土具有颗粒互补性质,采用40%磷尾矿砂和60%黏土形成的磷尾矿砂-土混合料,可以形成骨架密实结构。

沙漠腹地风积沙压实特性试验分析

塔克拉玛干沙漠腹地修建石油钻井平台地基,地基材料运距远且会破坏沙漠地区生态环境,考虑到因地制宜,采用沙漠地区丰富的风积沙资源作为地基填料,其压实特性是影响地基施工工艺及质量的关键因素。为了研究其压实特性,进行了标准重型击实实验、超重型击实试验。研究结果表明:该地区风积沙粒径主要分布在0.075~0.25mm之间,属于级配不良的细砂;风积沙的重型、超重型击实曲线均呈“双峰”型,在干燥状态及最佳含水率时均能达到最大干密度,室内风积沙击实试验推荐使用大击实筒;不同的击实方式会产生不同的试验结果,最大干密度应结合现场确定。

粉丝、粉条中铝含量测定时水分含量测定分析方法的选择

在测量粉丝、粉条中铝含量时,如果被检测样品含量在限量值附近,选择不同的水分测定方法就会得出“合格”与“不合格”两种判定结果。本研究通过对比分析不同水分检测方法,最后得出GB 5009.3—2016中规定的方法最适合粉丝、粉条类样品测试铝的计算结果的制备烘干。

对沥青混合料配合比设计规范的解读与实践

为更好地掌握与运用《公路沥青路面施工技术规范》(JTG F40—2004)附录B“热拌沥青混合料配合比设计方法”,对规范相关条款进行了研究解读,阐述了沥青混合料体积设计方法的原理,分析了各体积参数的意义以及各参数之间的内在逻辑关系,着重探讨了最小矿料间隙率与空隙率的变化规律,并通过举例验证了计算法确定最佳沥青用量的可行性。结果表明:1)最小矿料间隙率的作用是保证沥青混合料具有最小的沥青膜厚度;2)当矿料组成和沥青含量已定时,采用不同压实功,试件的矿料间隙率随其空隙率的增减而增减;3)采用理论计算方法,有利于更准确快捷地确定最佳沥青用量,缩短目标配合比设计的周期。

温度对玉米种子贮藏最适含水量的影响

将不同含水量的玉米种子分别置于50、35、20℃贮藏,研究温度对种子贮藏寿命的影响。结果表明,不同温度下玉米种子贮藏的最适含水量不同,呈现出随贮藏温度的降低而升高的趋势。50℃时的最适含水量为4.3%～5.0%,35℃时的最适含水量为5.4%～6.2%,而20℃贮藏的最适含水量变化范围较大。经过老化处理后,最适含水量种子比高含水量种子的电导率低30%,抗氧化酶活性保持较好,种子内脂质过氧化产物丙二醛的积累量减少。在种子可溶性糖积累的测定中发现,玉米种子不含有对耐干性起重要作用的水苏糖,这可能是玉米种子贮藏的最适含水量偏高及不耐超干的原因之一。