Stabilization of Dune Sand with Poly(Methyl Methacrylate) and Polyvinyl Acetate Using Dry and Wet Processing

Dune sands were stabilized using poly(methyl methacrylate) and polyvinyl acetate and examined using physical and mechanical tests. The California Bearing Ratio test was used to measure the engineering properties of the stabilized materials under dry and the wet environmental conditions, revealing the bearing ratio of the improved dune sands. Our results indicate that both polymers have good potential for increasing the strength of dune sands in the dry state and that there is little decrease in the CBR strength in the saturated state in comparison with the dry state, indicating the stiffness and stability of the compounds against moisture. This is an important point to consider for longevity of roads and road repair and maintenance, because good strength of stabilized sand in saturated sand can prevent early destruction of the road caused by demolition or erosion of the road bed during saturation. The results also demonstrate that the optimum added quantity of polymer for maximum effect was 3% by weight and that the curing time for maximum effect was 28 days. The amount of polymer added was very more important factor for improved dune sand California Bearing Ratio strength in comparison with curing time of the stabilized specimens.     

Strength behavior and microstructural characteristics of tropical laterite soil treated with sodium silicate-based liquid stabilizer

Although the effects of nontraditional stabilizers on the geotechnical properties of tropical soils has been the issue of investigation in recent years, the micro-structural characteristics of nontraditional soil additives and in particular selected additive (TX-85) have not been fully studied. Nontraditional soil stabilization additives are widely used for stabilizing marginal materials. These additives are low-cost alternatives to traditional construction materials and have different compositions. They also differ from one another while interacting with soil. In line with that, it was the objective of this research to investigate the strength properties and physicochemical mechanisms related to tropical laterite soil mixed with the liquid stabilizer TX-85. Macro-structure study, i.e., compaction, and unconfined compression strength test were used to assess the engineering and shear properties of the stabilized laterite soil. In addition, the possible mechanisms that contributed to the stabilization process were discussed using various spectroscopic and microscopic techniques such as X-ray diffractometry (XRD), energy-dispersive X-ray spectrometry, scanning electron microscopy, and Fourier transform infrared spectroscopy. From engineering point of view, the results indicated that the strength of TX-85 stabilized laterite soil improved significantly. The degree of improvement was approximately four times stronger than natural soil after a 7-day curing period. The XRD showed no crystalline products (gel form). Moreover, weathering effects were obvious in TX-85 treated samples in most of clay minerals’ peak intensities. These effects were reduced especially for kaolinite mineral inside the soil with curing time.     

Effect of Natural Zeolite and Cement Additive on the Strength of Sand

It is widely known and well emphasized that the cemented sand is one of economic and environmental topics in soil stabilization. In some instances, a blend of sand, cement and other materials such as fiber, glass, nano particle and zeolite can commercially be available and effectively used in soil stabilization especially in road construction. In regard to zeolite, its influence and effectiveness on the properties of cemented sands systems has not been completely explored. Hence, in this study, based on an experimental program, it has been tried to investigate the potential of a zeolite stabilizer known as additive material to improve the properties of cemented sands. A total number of 216 unconfined compression tests were carried out on cured samples in 7, 28 and 90 days. Results show unconfined compression strength and failure properties improvements of cement sand specimens when cement replaced by zeolite at optimum proportions of 30 % after 28 days due to pozzolanic reaction. The rate of strength improvement is approximately 20–78 and 20–60 % for 28 and 90 days curing times respectively. The efficiency of using zeolite has been enhanced by increasing the cement content and porosity of the compacted mixture. The replacement of cement by natural zeolite led to an increase of the pH after 14 days. Chemical oxygen demand (COD) tests demonstrate that the materials with the zeolite mixture reveal stronger adsorptive capacity of COD in compare to cemented mixture. Scanning electron microscope images show that adding zeolite in cemented sand changes the microstructure (filling large porosity and pozzolanic reaction) that results in increasing strength.     

Sustainable Improvement of Tropical Residual Soil Using an Environmentally Friendly Additive

Many tropical residual laterites have relatively poor engineering properties due to the significant percentage of fine-grained soil particles that they contain, which are formed by the soil weathering process. The widespread presence of laterite soils in tropical regions often requires that some form of soil improvement be performed to allow for their use in various civil engineering applications, such as for road base or subbase construction. One of the most commonly utilized stabilization techniques for laterite soils is the application of additives that chemically react with the minerals that are present in soil to enhance its overall strength; effective soil stabilization can allow for the use of site-specific soils, and can consequently result in significant cost savings for a given project. With an increasing focus on the use of more environmentally friendly and sustainable materials in the built and natural environments, there is an emerging interest in eco-friendly additives that are an alternative to traditional chemical stabilizers. The current study examines the viability of xanthan gum as an environmentally friendly stabilizer that can improve the engineering properties of tropical residual laterite soil. Unconfined compressive strength (UCS) tests, standard direct shear tests, Brunauer, Emmett, and Teller (N₂-BET) surface area analysis tests and field emission scanning electron microscopy (FESEM) tests were used to investigate the effectiveness of xanthan gum for stabilization of a tropical laterite soil. The UCS test results showed that addition of 1.5% xanthan gum by weight yielded optimum stabilization, increasing the unconfined compressive strength of the laterite soil noticeably. Similarly, direct shear testing of 1.5% xanthan gum stabilized laterite specimens showed increasing Mohr–Coulomb shear strength parameters with increases in curing time. From the FESEM results, it was observed that the stabilization process modified the pore-network morphology of the laterite soil, while also forming new white layers on the surface of the clay particles. Analysis of the test results indicated that xanthan gum stabilization was effective for use on a tropical residual laterite soil, providing an eco-friendly and sustainable alternative to traditional soil stabilization additives such as cement or lime.     

Soil erosion on a sub-tropical coastal dune complex,Transkei, Southern Africa

A fossil dune complex on the east coast of southern Africa is presently undergoing extensive accelerated erosion, with concomitant dune reactivation and degradation, unconfined erosion (sheetwash and wind deflation) and extensive development of V-shaped, ravine-type gully forms on hillslopes composed of thick sequences of Quaternary (Berea Formation?) dune sands. The sands comprise a thick, reddened, ferralitic sand carapace overlying white, poorly cemented quartzitic sands. Soil erosion has resulted from degradation of the red dune sand cover. Despite the cohesionless nature of the host materials, gully forms developed on dune sands are typologically similar to those developed in regolith or soft bedrock. This demonstrates that gully forms are influenced by the degree of homogeneity, rather than the absolute strength, of the host material subject to erosion. Factors which have contributed to erosion are discussed.     

一种复合加固剂改良砂土的强度试验研究

本研究采用聚丙烯纤维和聚氨酯型固化剂复合加固材料（简称复合加固剂）对砂土进行改良,对不同配比的复合加固剂改良砂土的强度,进行了无侧限抗压和直剪试验研究,并对其改良机理进行较为深入的分析。试验结果表明,复合加固剂改良砂土的无侧限抗压强度和剪切强度均得到了一定程度的提高。当复合加固剂中固化剂的浓度一定时,砂土的无侧限抗压强度和黏聚力均随着纤维含量的增加先增加后减少,分别在纤维含量0.3%和0.2%左右达到峰值;当复合加固剂中纤维含量一定时,砂土的无侧限抗压强度和黏聚力均随着固化剂浓度增加而增加,而内摩擦角变化不大。综合试验结果和施工可行性,建议复合固化剂在改良砂土应用中的最佳配比为聚氨酯固化剂浓度30%,聚丙烯纤维含量0.2%。复合加固剂是结合物理和化学加固方式,能够有效地提高砂土强度。本研究结果为复合加固材料的进一步研究和应用提供一定的参考依据。     

Physicochemical behavior of tropical laterite soil stabilized with non-traditional additive

Non-traditional soil stabilizers are widely used for treating weak materials. These additives are cost- and time-effective alternatives to more traditional materials such as lime and cement. It has been well established that the treatment of natural soil with chemical additives will gradually affect the size, shape, and arrangement of soil particles. Furthermore, the degree of improvement is dependent on the quantity and the pattern of new products formed on and around the soil particles. In this paper, unconfined compressive strength (UCS) test was performed as an index of soil improvement on mix designs treated with calcium-based powder stabilizer (SH-85). The time-dependent changes in shear strength parameter and compressibility behavior of treated soil were also studied using standard direct shear and one-dimensional consolidation tests. In order to better understand the shape and surface area of treated particles, FESEM, N₂-BET, and particle size distribution analysis were performed on soil-stabilizer matrix. From engineering standpoint, the UCS results showed that the degree of improvement for SH-85-stabilized laterite soil was roughly five times stronger than the untreated soil at the early stages of curing (7-day period). Also, a significant increase in the compressibility resistance of treated samples with curing time was observed. Based on the results, less porous and denser soil fabric was seen on the surface of clay particles. FESEM images of the treated mix designs showed the formation of white lumps in the soil fabric with the cementitious gel filling the pores in the soil structure.     

Experimental investigation of cephapirin adsorption to quartz filter sands and dune sands

Batch experiments were performed to investigate cephapirin (a widely used veterinary antibiotic) adsorption on various size sands of low total organic carbon content (0.08–0.36 wt%). In the aqueous concentration range investigated (11–112 μmol/L cephapirin), adsorption to nearly pure quartz filter sands (0.50–3.35 mm diameter) is low. Isotherms are S-shaped and most display a region of minimum adsorption, where decreased adsorption occurs with increasing solution concentration, followed by increased adsorption at higher concentrations. Cephapirin adsorption to quartz-rich, feldspar-bearing dune sands (0.06–0.35 mm diameter), and the smallest quartz filter sand investigated (0.43–0.50 mm), can be described by linear sorption isotherms over the range of concentrations investigated. Distribution coefficients (K _d) range from 0.94 to 3.45 L/kg. No systematic relationship exists between grain size and amount of adsorption for any of the sands investigated. Cephapirin adsorption is positively correlated to the feldspar ratio (K-feldspar/(albite + Ca-plagioclase). Feldspar-ratio normalization of distribution coefficients was more effective than organic carbon normalization at reducing variability of K _d values in the dune sands investigated.     

碱激发材料固化低液限粉黏土路用性能及抗冻融特性研究

以伊犁地区S315线蜂场至尼勒克段低液限粉黏土为研究对象,以碱激发材料为固化剂,对粉质黏土和其固化土开展了路用性能指标试验与冻融循环试验,并利用电镜扫描试验(SEM)与X射线衍射试验(XRD)研究了固化土的微观特征,探讨了碱激发材料对粉质黏土路用性能指标与抗冻融特性的影响.试验结果表明,固化土的无侧限抗压强度与抗剪强度...     

Potential of marble dust to stabilise red tropical soils for road construction

The potential of marble dust as a stabilizing additive to red tropical soils was evaluated. The evaluation involved the determination of the geotechnical properties of three different red tropical soils in their natural state as well as when mixed with varying proportions of marble dust. The parameters tested included the particle size distribution, specific gravity, Atterberg limits, the standard compaction characteristics, the compressive strength and the California bearing ratio (CBR). The strength tests were repeated after normal 28 day curing of the treated samples and also after accelerated 24 h curing at temperatures of 40°C, 60°C and 80°C.

Results showed that the geotechnical parameters of red tropical soils are improved substantially by the addition of marble dust; plasticity was reduced by 20 to 33% and strength and CBR increased by 30 to 46% and 27 to 55% respectively. The highest strength and CBR values were achieved at 8% marble dust. Results also showed that normal 28 day curing improved the strength of the marble dust-treated soil with over 80% strength gain achieved after 7 to 10 days of normal curing. Higher strength development was realised following accelerated 24 h curing at 60°C.

Although these results imply marked improvement in the geotechnical parameters of red tropical soils, the higher strength developed is not enough for the improved soil to be used as a base material in the construction of heavily trafficked flexible pavements. The improved material may, however, be successfully used as base material for lightly trafficked roads and as a sub-base material for heavily trafficked roads.     

Coastal dunes and strandplains in southeast Queensland: Sequence and chronology

Parabolic dunes invade coastal strandplains and overlie prior blown dunes in southeast Queensland. These coastal dune landscapes were produced primarily by real changes in wind strength and frequency. Sand movement began in past glacial ages and in the most recent instance persisted into Holocene time. Four interglacial shores are identified with marine isotope stages 5, 7, 9 and 11, and allow estimation of the ages of the dune and beach sands, by correlation with the EPICA Dome C ice core, as follows: Triangle dune sand, n.d.; Garawongera dune sand, 65 ka; Woorim beach sand, 125 ka; Bribie beach sand, 245 ka; Bowarrady dune sand, 270 ka; Poyungan beach sand, 335 ka; Yankee Jack dune sand, 360 ka; Ungowa beach sand, 410 ka; Awinya dune sand, 430 – 486 ka; Cooloola dune sand, >486 ka.     

Lime stabilization of clay minerals and soils

Clay soil can be stabilized by the addition of small percentages, by weight, of lime, thereby enhancing many of the engineering properties of the soil and producing an improved construction material. In order to illustrate such improvements, three of the most frequently occurring minerals in clay deposits, namely, kaolinite, montmorillonite and quartz were subjected to a series of tests. As lime stabilization is most often used in relation to road construction, the tests were chosen with this in mind. Till and laminated clay were treated in similar fashion. With the addition of lime, the plasticity of montmorillonite was reduced whilst that of kaolinite and quartz was increased somewhat. However, the addition of lime to the till had little influence on its plasticity but a significant reduction occurred in that of the laminated clay. All materials experienced an increase in their optimum moisture content and a decrease in their maximum dry density, as well as enhanced California bearing ratio, on addition of lime. Some notable increases in strength and Young's Modulus occurred in these materials when they were treated with lime. Length of time curing and temperature at which curing took place had an important influence on the amount of strength developed.     

用固化剂GX08加固杭州海湖相软土的强度特性研究

为了验证固化剂GX08加固杭州海湖相软土的效果及考察有机质对水泥固化的不利影响,对固化土的强度特性进行了试验研究。结果表明,有机质的添加会显著阻碍固化土强度的增长,而固化剂GX08能有效增强固化土的强度;固化土强度与有机质含量存在二次函数关系,与水泥掺量呈线性关系,与固化剂GX08掺量和龄期都以对数函数的形式相关;将总灰水比C/W用于固化土强度模型的建立,通过对试验数据的分析与整理,建立了同时考虑固化土中有机质含量、水泥掺量、固化剂掺量和龄期影响的固化土综合强度预测模型。最后对模型进行了推广使用,验证了模型的适用性。     

The Use of Municipal Solid Waste Incinerator Ash to Stabilize Dune Sands

Dune sands are problematic soils because they have low shear strength and are susceptible to collapse upon wetting. Dosages of municipal solid waste incinerator ash between 10 and 80?% were used to improve the engineering properties of dune sands. The soil-ash mixtures were allowed to cure for periods from 7 to 90?days. Laboratory tests such as compaction, unconfined compression, shear box and hydraulic conductivity tests were performed to measure the engineering characteristics of the stabilized material. The results showed that the maximum dry density remains approximately constant up to ash content of 30?% and then it decreases with the increase in ash content. The optimum water content increases with the increase in ash content. The unconfined compressive strength substantially increases with ash content up to 30?% and then decreases with the increase in ash content. The angle of friction follows similar trend to the unconfined compressive strength. However, the cohesion shows a steady increase with the ash content. The hydraulic conductivity of the stabilized material consistently decreases with the increase in the ash content. The effect of curing time on the hydraulic conductivity is minimal after 7?days of curing time. However, the unconfined compressive strength and the cohesion slightly increased with curing time up to 90?days.     

昌黎海岸风成沙丘砂组构特征及其与海滩砂的比较

对昌黎海岸沙丘砂进行薄片统计,重砂矿物分析,电镜扫描,粒度分析及与海滩砂的对比研究发现,沙丘砂在物质组成、颗粒形态、石英砂表面结构特征和粒度特征方面均继承了海滩砂特征,不过,海滩砂中也有沙丘砂的某些特征,反映了两者沉积的混合。这是由于向岸风和离岸风共同作用的结果。     

Stabilization of Tropical Peat Soil from Sarawak with Different Stabilizing Agents

This paper describes a study on tropical peat soil stabilization to improve its physical properties by using different stabilizing agents. The samples were collected from six different locations of Sarawak, Malaysia, to evaluate their physical or index properties. Out of them, sample having the highest percentage of organic content has been selected for stabilization purposes. In this study, ordinary portland cement (OPC), quick lime (QL), and class F fly ash (FA) were used as stabilizer. The amount of OPC, QL, and FA added to the peat soil sample, as percentage of dry soil mass, were in the range of 5–20%; 5–20% and 2–8%, respectively for the curing periods of 7, 14, and 28 days. The Unconfined Compressive Strength (UCS) test was carried out on treated/stabilized samples with the above mentioned percentages of the stabilizer and the result shows that the UCS value increases significantly with the increase of all stabilizing agent used and also with curing periods. However, in case of FA and QL, the UCS value increases up to 15 and 6%, respectively with a curing period of 28 days but decreases rather steady beyond this percentage. Some UCS tests have been conducted with a mixture of FA and QL to study the combined effect of the stabilizer. In addition, Scanning Electron Microscope (SEM) study was carried out on original peat soil and FA, as well as some treated samples in order to study their microstructures.     

新型土体固化剂加固海底淤泥力学特性研究

海底淤泥具有特殊的土性特点,其固化研究尚处于起步阶段。GS固化剂是一种以工业固废为主要原料的适用于软土加固的绿色固化材料。本文开展了GS固化剂加固海底淤泥的应用研究。以香港某工程海底淤泥为加固对象,对比分析了GS固化剂和水泥的掺量、龄期对固化土无侧限抗压强度的影响。研究结果表明,相比于普通水泥,GS固化土的早期强度更高...     

The Quality Control of Engineering Properties for Stabilizing Silty Nile Delta Clay Soil,Egypt

Clay soil with low-bearing capacities can present great problems underlying pavement and light structures due to uncertainty associated with their performance. This paper describes a sonic based testing methodology for quality control of a surface stabilized soil. From an engineering aspect, an increase in water content has a number of disadvantageous consequences: cohesion decreases, the soil swells, the alternating dry-out/shrinkage and wetting/swelling effects destroy the rock or a soil structure. Cement is mixed into the soil to increase both the strength and the usability of local soils in constructions purposes. This is to overcome the problems by strengthening the soil underlying the structure or diminishing the leads transmitted from the foundation to the soil. The compressive strength of the stabilized soil is highly dependent on the type of soil, moisture content, cement content, and compaction work, and can therefore vary significantly in the field. The authors performed the quality control by measuring the sonic and tensile strength velocity in the stabilized soil that has been correlated to compressive strength in native materials. The improvement of the soil materials by the addition of cement could make the material suitable as filling materials, foundation and/or a road base construction. The quality control for the stabilized soils was investigated using sonic measurements and strength gain. The test methods were performed to evaluate the degree of improvement achieved through the measurement of compression and shear-wave velocities of the soil under study. Scanning electron microscopy and electron dispersive X-ray analyses were performed on raw and laboratory treated for qualitative understanding the strength minerals formed during stabilization. The sonic test showed a considerable improvement with curing time and percentages of stabilizer. Mineralogical studies indicated the formation of silica and alumina hydrates along with interwoven structure of cement treated clay particles suggesting adequate mixing of the soil and binder owing to the strength of the soil materials.     

The onset of dune formation in the Strzelecki Desert,South Australia

This study is concerned with the Late Quaternary climatic chronology of the Strzelecki Desert dunefields in central Australia. The sand ridges comprise layers of quartz sand, some of which include palaeosol horizons with carbonated rootlets providing excellent opportunity for dating of alternations of dune building and stability by using optically stimulated luminescence (OSL). Deduced from the OSL age of the oldest aeolian layer dated, we conclude that the onset of aridity dates back to at least ∼65 ka. Older phases of aeolian activity though, following a fluvial depositional phase 160 ka ago, cannot be excluded, although no aeolian layers giving evidence for this have been found in the two dunes dated here. Unconsolidated dune sands in the upper part of one section with Late Holocene (4 ka to modern) depositional ages indicate a reactivation of the dunefield in recent times.From the crosscheck of ¹⁴C ages of the carbonated rootlets with OSL results it is concluded that under the given environmental conditions radiocarbon dating of the calcareous rootlets is not able to provide reliable ages for the phase of soil development.     

煤系固废协同固化盐渍土的力学特征与机理研究

以干旱半干旱地区固体废弃物资源化利用为研究背景,利用煤系固废煤矸石(CG)、煤系偏高岭土(CMK)联合干旱区易获取的固废材料电石渣(CS)协同普通硅酸盐水泥(OPC)开发一种新型固化材料,探讨其固化干旱半干旱区盐渍土的力学性能与微观变化机理。基于室内实验,对比100%OPC固化盐渍土,研究不同矿区产出的CG以及煤矸石-煤系偏高岭土-电石渣协同固化剂(CGCMK-CS)替代52%、60%、68%、72%、84%OPC后各龄期的无侧限抗压强度(UCS)特征,并取特征组进行有害阴离子(Cl-、SO42-)浸出试验与微观测试,从微观角度对其强度变化机理进行探讨。结果表明,煤矸石–电石渣–煤系偏高岭土–普通硅酸盐水泥协同固化(CG-CMK-CS-OPC)体系具有良好的Cl-与SO42-结合能力,固化盐渍土后Cl-与SO42-浸出量是100%OPC的一半,其水化产物铝酸三钙能与盐渍土中的Cl-与SO42-生成AFm相产物,并使体系中的团粒内孔隙与团粒间孔隙向颗粒内与颗粒间孔隙转化,由此降低了盐渍土中盐分带来的危害。根据7 d UCS试验结果,使用山西运城CG固化体系的效果最佳,这与其活性钙质和铁铝...