Biopolymer stabilization of clayey soil

This study investigates the efficacy of sodium alginate(SA),xanthan gum(XG),guar gum(GG)and chitosan(CS)d each applied at five different solid biopolymer-to-water mass ratios(or dosages)and cured for 7 d and 28 d d on the unconfined compressive strength(UCS)performance of a high plasticity clayey soil.Moreover,on identifying the optimum biopolymer-treatment scenarios,their performance was compared against conventional stabilization using hydrated lime.For a given curing time,the UCS for all biopolymers followed a riseefall trend with increasing biopolymer dosage,peaking at an optimum dosage and then subsequently decreasing,such that all biopolymer-stabilized samples mobilized higher UCS values compared to the unamended soil.The optimum dosage was found to be 1.5%for SA,XG and CS,while a notably lower dosage of 0.5%was deemed optimum for GG.Similarly,for a given biopolymer type and dosage,increasing the curing time from 7 d to 28 d further enhanced the UCS,with the achieved improvements being generally more pronounced for XG-and CS-treated cases.None of the investigated biopolymers was able to produce UCS improvements equivalent to those obtained by the 28-d soilelime samples;however,the optimum XG,GG and CS dosages,particularly after 28 d of curing,were easily able to replicate 7-d lime stabilization outcomes achieved with as high as twice the soil’s lime demand.Finally,the fundamental principles of clay chemistry,in conjunction with the soil mechanics framework,were employed to identify and discuss the clayebiopolymer stabilization mechanisms.

Effect of Friedel's salt on strength enhancement of stabilized chloride saline soil

In the field of soil stabilization, only calcium silicate hydrate(CSH) and ettringite(AFt) as hydration products have been reported to directly contribute to the strength enhancement of the soil. A chloride dredger fill, an artificial chloride saline soil, and a non-saline soil were stabilized by Portland cement(PC) and PC with Ca(OH)_2(CH) with different contents. A series of unconfined compressive strength(UCS) tests of stabilized soil specimen after curing for 7 d and 28 d were carried out, and the hydration products and microstructure of the specimens were observed by X-ray diffractometry(XRD), scanning electronic microscopy(SEM), and energy-dispersive X-ray analysis(EDXA). The results showed that the strengths of PC+CH-stabilized chloride saline soils were much higher than those of PC-stabilized soils. A new hydration product of calcium aluminate chloride hydrate, also known as Friedel's salt, appeared in the PC+CH-stabilized chloride saline soils. The solid-phase volume of Friedel's salt expanded during the formation of the hydrate; this volume filled the pores in the stabilized soil. This pore-filling effect was the most important contribution to the significantly enhanced strength of the PC+CH-stabilized chloride saline soils. On the basis of this understanding, a new optimized stabilizer was designed according to the concept that the chloride in saline soil could be utilized as a component of the stabilizer. The strength of the chloride saline soils stabilized by the optimized stabilizer was even further increased compared with that of the PC+CH-stabilized soils.

Development of Steel Slag-Based Solidification/Stabilization Materials for High Moisture Content Soil

To solve the problems of high moisture content,high viscosity,and poor engineering mechanical properties of soil,this paper using with steel slag(SS)and desulfurization ash(DS)as initial raw materials,realizing the coop-erative treatment of solid waste and solidification of silt soil.The synergistic utilization of SS and DS can reduce the production cost of curing agent and promote its own consumption.According to blended cement of various SS contents and inspected compressive strength performances,the most suitable raw materials ratio was selected.The best formula for this curing agent is cement:steel slag=3:7 with 5%DS,and its 28-day compressive strength can reach 30 MPa.The experiment shows that the effect of DS and Na_(2)SO_(4) reagent with the same quality on early compressive strength improvement of cement and SS system is not much different.In this study,the mineral composition and microstructure of different gel system blocks were characterized by XRD,SEM and EDX,and a large number of webbed structures were found in the SEM test,which was not seen in previous studies.Besides,unconfined compressive strength(UCS),water resistance,and toxic characteristic leaching procedure(TCLP)were used to evaluate silt solidified soil properties.The results demonstrated that the solidified silt could meet not only the standard of general subgrade;but also has a partial stabilization effect of heavy metal ions.

Study on influence factors of cement-stabilized soil compressive strength

The cement dry jet mixing method has been used to reinforce soft cohesive ground to increase the strength of soft cohesive ground and to decrease its deformation. The study briefly introduces the curing mechanism of cement-soil,presents the factors of influencing on compressive strength,mainly analyses the factors including cement mixing ratio,cement strength grade,curing age,moisture content and soil texture and puts forward some rational proposals at last.

Stabilization of saline silty sand using lime and micro silica

Many construction and post-construction problems have been reported in the literature when saline soils have been used without understanding of their abnormal behavior,especially their inferior bearing capacity in the natural condition.The strength of these soils further decreases on soaking.Saline soil deposits cover extensive areas in central Iran and are associated with geotechnical problems such as excessive differential settlement,susceptibility to strength loss and collapse upon wetting.Because of these characteristics,some of the roads constructed on saline soils in Taleghan area have exhibited deterioration in the form of raveling,cracking and landslides.The main objective of this work is to improve the load-bearing capacity of pavements constructed on Taleghan saline soils using lime and micro silica.Soil samples from Hashtgerd-Taleghan road were collected and tested for improving their properties using lime and micro silica at different dosages ranging from 0 to 6%.The load-bearing capacity of stabilized soil mixtures was evaluated using California Bearing Ratio(CBR) and unconfined compressive strength tests.The test results indicate that the lime improves the performance of soil significantly.The addition of 2% lime with 3% micro silica has satisfied the strength-deformation requirements.Therefore,improved soil can be used as a good subbase in flexible pavements.

Assessment of strength development in cement-admixed artificial organic soil with GX07

To explore the stabilization effect of stabilizing agent GX07 on treating organic soil and the influence of organic matter on the strength development of stabilized soil,artificial organic soil with various organic matter content was obtained by adding different amounts of fulvic acid into non-organic clay,and then liquid-plastic limit tests were carried out on the artificial organic soil.Meanwhile,unconfined compressive strength(UCS) tests were performed on cement-only soil and composite stabilized soil,respectively.The test results indicate that the plastic limit of soil samples increases linearly,and the liquid limit increases exponentially as the organic matter content increases.The strength of stabilized soil is well correlated with the organic matter content,cement content,stabilizing agent content and curing time.When the organic matter content is 6%,as the cement content varies in the range of 10%-20%,the strength of cement-only soil increases from 88.5 to 280.8 kPa.Once 12.6% GX07 is added into the mix,the strength of stabilized soil is 4.93 times compared with that of cement-only soil.GX07 can obviously improve the strength of cemented-soil and has a good economic applicability.A strength model is proposed to predict strength development.

偏高岭土基地聚合物对水泥固化红黏土的改善机制

为了研究偏高岭土对水泥固化红黏土的改善效果,开展了三种组合(纯水泥、水泥+偏高岭土以及水泥+偏高岭土+水玻璃)的红黏土固化试验。基于固化剂化学组分和固化土的干密度、pH值以及物相成分等,研究了新型复合碱激发体系作用下偏高岭土对水泥固化红黏土的作用机理。研究表明:当水泥、偏高岭土和水玻璃掺入比分别为12%、5%和3%时,红黏土固化效果最佳,相比于纯水泥固化土其强度提高了2.82倍。在n(SiO_(2))/n(Al_(2)O_(3))从2.53增加至4.05过程中,固化土强度发展较快,随后逐渐趋于稳定。由于水泥水化生成的Ca^(2+)能够平衡固化体系中的部分负电荷,在n(Na_(2)O)/n(Al_(2)O_(3))较小的情况下固化土强度得到了显著提升。最后通过固化土微观形貌及主要物相组成发现,新型复合碱激发体系的试样中含有无定形地聚物凝胶且主要物相特征峰峰值有所降低,说明产生了更多的地聚合凝胶产物。

HAS土壤固化剂固化土料的特性及工程应用

HAS土壤固化剂是一种灰渣胶凝材料,它由矿渣及矿渣组合物为主体原料(80%以上),配以适量的活化剂混合粉磨制成。在详细介绍HAS固化剂的基本性能及其在灰坝工程、水利水电工程、基础处理工程等领域应用的基础上,通过室内试验和对工程应用的分析探讨,进一步说明了HAS土壤固化剂的适用性,为土料固化技术的开发推广应用提供了依据和参考。

新型复合激发锂渣基固化剂加固软土试验研究

为提高固体废弃物锂渣的利用率,以锂渣作为原材料,选择生石灰作为外添加剂,同时添加碳酸钙和氢氧化钠作为复合激发剂,利用碱激发技术研制一种新型软土固化剂材料。采用正交试验研究该新型复合激发锂渣基固化剂的固化配合比,并探究试验中各因素对固化土抗压强度的影响,同时结合XRD及SEM揭示固化剂与软土之间的固化机理及微观结构的演化规律。结果表明,固化剂的最佳配合比为锂渣掺量73%(质量分数)、生石灰掺量18%(质量分数)、复合激发剂掺量9%(质量分数)、碳酸钙与氢氧化钠质量比1∶1。该配合比下固化土7和28 d无侧限抗压强度分别为1.32和2.35 MPa,水稳定性系数分别为0.80和0.87。在生石灰与复合激发剂的协同作用下,固化土中水化硅铝酸钙(C-A-S-H)和水化硅铝酸钠(N-A-S-H)等胶凝物质显著增多,土体结构致密度提高强度及水稳定性提高。

新型土体固化剂加固土的力学性能研究

新型土体固化剂由水泥、矿渣、钢渣、石膏和外加剂等为原材料生产而成,通过室内配合比强度试验和现场取浆强度试验研究新型土体固化剂加固土的无侧限抗压强度。以苏州市某在建地铁车站工程场地内典型土层为例,探讨了不同土质、新型土体固化剂掺量以及养护龄期对加固土强度的影响,对试验数据进行了线性分析,得到了加固土强度与新型土体固化剂掺量、养护龄期成正相关关系。为进一步验证新型土体固化剂加固土的实际效果,在工程现场进行搅拌桩试桩并对桩体浆液取样试验,通过分析表明现场取浆强度试验结果与室内配合比强度试验结果较为一致。相关结论可为新型土体固化剂的使用提供借鉴。

软土地基加固用新型土壤固化剂的制备及性能研究

为了提高软土资源的利用效率,以丙烯酸酯BA、丙烯酸AA和苯乙烯St作为单体,以脂肪醇聚氧乙烯AEO-9和山梨醇酐单油酸酯SP80作为乳化剂,通过乳液聚合法制备了一种适合软土地基加固用的新型土壤固化剂PPG-1,并对其综合性能进行了评价。结果表明:土壤固化剂PPG-1的掺量越大,无侧限抗压强度、水稳定系数、抗冻指数和质量损失率就越大。养护龄期越长,无侧限抗压强度和水稳定系数就越大,固化处理效果就越好。推荐土壤固化剂PPG-1的最佳掺量为0.5%,能使目标固化土试样在养护7 d时的无侧限抗压强度值达到2.81 MPa,水稳定系数达到85.7%,并且经过冻融循环5次后的抗冻指数达到83.6%,质量损失率为小于5%,各项性能参数均能满足标准《土壤固化剂应用技术标准》(CJJ/T 286-2018)中对固化土性能指标的要求。新型土壤固化剂PPG-1能够显著改善软土样品的力学性能、耐水性能和抗冻性能,能够满足软土地基加固的需求。

石灰粉煤灰固化硫酸盐渍土的水稳定性与微观结构特征

高含盐量硫酸盐渍土的抗压强度低、水稳定性非常差,不能直接用于道路工程建设,应采用石灰和粉煤灰对其固化。为解决超硫酸盐渍土的工程应用问题,选择石灰掺量6%、8%、10%、12%、14%与石灰︰粉煤灰1︰1、1︰1.5、1︰2、1︰2.5、1︰3的固化方案,开展未浸水与浸水固化土的抗压试验,评价石灰和粉煤灰掺量对固化土水稳定性的影响;通过扫描电镜观察与能谱测试,分析石灰和粉煤灰掺量对硫酸盐渍土微观形貌的影响;计算微观结构指标,辅助分析石灰和粉煤灰对硫酸盐渍土的固化机理。试验结果显示:(1)在硫酸盐渍土中掺入适量的石灰和粉煤灰,固化土的抗压强度与水稳定性明显提高。随石灰粉煤灰掺量的增加,固化土的强度呈先增长后降低趋势。(2)石灰和粉煤灰化学反应产生了凝胶物质与针棒状物质,填充土的孔隙,增强土颗粒间的胶结力,提高了硫酸盐渍土的抗压强度与水稳定性。(3)采用8%石灰+24%粉煤灰配合比,固化土的抗压强度最高且水稳定性最好。8%石灰+24%粉煤灰固化土的颗粒胶结更紧密,土团粒粒径较大,土团粒形状更趋向于扁圆状,土的结构更稳定。研究结果表明,8%石灰+24%粉煤灰配合比可为超硫酸盐渍土改性与固化的工程利用提供参考。

碱激发作用下水泥基海相软土固化剂研究

为改善水泥固化软土效果,考虑碱激发作用,选择电石渣、生石膏、氯化钙、原状灰和硅酸钠作为辅助固化剂,采用无侧限抗压强度试验、X射线衍射、电镜扫描试验研究固化剂与硅酸盐水泥间的协同固化作用。通过正交试验确定出固化剂材料与水泥的最优配比。7 d和14 d龄期结果表明,在固化早期,电石渣的掺入量对强度影响效果最为突出,随着龄期推进,影响效果逐渐减弱。28 d龄期结果表明,氯化钙掺入量是影响固化土试样28 d龄期无侧限抗压强度的主要因素。

路用碱渣复合土水稳定性试验研究

利用碱渣制备路用碱渣复合土,能够规模资源化利用固废碱渣,减低道路建材成本,但碱渣复合土的水稳定性对于材料的性能至关重要。论文设计试验测试了不同碱渣掺量条件下,碱渣复合土无侧限抗压强度与水稳定性,分析了碱渣掺量对碱渣复合土水稳定性的影响规律及作用机制。研究表明:碱渣含水率较高,偏碱性;强度较低,不适宜单独作为工程土直接使用。碱渣掺量在0~4%范围内,碱渣复合土试件7d浸水UCS和未浸水UCS均呈现出先增加后减小的变化规律,强度与水稳定性系数均在碱渣掺量2%时达到最高,因此,当碱渣掺量2%、水泥掺量2%、石灰掺量2%时,强度最高,水稳定性最好。适量碱渣,在碱渣复合土体系中,主要起微集料充填效应、水化反应生成胶凝物等作用,提高材料致密程度,改变材料渗透性,共同提高水稳定性。但过量碱渣,将导致碱渣复合土水强度降低,水稳定性变差。研究结果可为碱渣在道路领域再生利用与路用材料性能改良提供借鉴。

热-盐作用下水稳碎石强度变化规律及破坏特征研究

水泥稳定碎石材料在热-盐作用下发生物理和化学侵蚀反应,使得试件强度变化规律和破坏特征发生变化。文章采用无侧限抗压强度试验和数码相机图像采集技术,分析了硫酸钠含量、成型温度、水泥含量对水稳碎石材料强度变化规律和试件破坏特征的影响。结果表明:随着硫酸钠含量增加,无侧限抗压强度先增大后减小,峰值点在2.5%,试件破坏形式由龟裂破坏转变为主裂缝破坏,再转变为多裂缝破坏;无侧限抗压强度随着成型温度、水泥含量的升高逐渐增大,且试件由龟裂破坏转变为主裂缝破坏;当试件强度强化,其破坏形式以主裂缝破坏为主;基于强度变化规律,采用最小二乘法和归一化法,建立了热-盐作用下水稳碎石无侧限抗压强度变化预测模型。

HAS土壤固化剂在长江航道削坡土上的固化试验

通过开展HAS高强耐水土壤固化剂(HAS固化剂)室内固化长江航道削坡土的试验,以及将成型固化土泡水及放置于户外自然环境的试验,分析了不同的固化剂、石屑和土样的配比设计在不同时间和不同条件下对无侧限抗压强度的影响,试验得到了HAS固化土的无侧限抗压强度的主要影响因素和变化规律。研究成果为实现长江航道削坡土的资源化利用提供了一定的技术基础。

长庆油田区块井眼尺寸效应与井壁稳定性分析

为了研究长庆油田区块井眼尺寸与井壁稳定性的关系,对不同开孔直径的岩样进行单轴抗压强度试验,得到开孔直径与抗压强度的关系,并以此建立考虑井眼尺寸效应的井壁坍塌压力、破裂压力的数学模型,计算得到钻井液坍塌压力当量密度与破裂压力当量密度。结果表明:井眼尺寸减小,抗压强度随之增加,对应的坍塌压力减小且破裂压力增加,钻井液安全密度窗口范围随之扩大,井眼尺寸减小有利于井壁稳定。研究对小井眼现场安全钻井有一定的指导意义。

硫铝酸盐水泥基预拌流态固化土固化剂性能的研究

以硫铝酸盐水泥和二水石膏为原材料制备了预拌流态固化土固化剂,以强度、体积膨胀率和成本为指标进行同化剂配选。以胶土比1∶9制备固化土试样,进一步研究了硫铝酸盐水泥与二水石膏的比例对固化土抗压强度和体积稳定性的影响。结果表明,固化剂胶砂的抗压和抗折强度均随硫铝酸盐水泥掺量的增加先提高后降低再提高。硫铝酸盐水泥掺量的增加有利于固化土试样抗压强度和体积稳定性的改善。硫铝酸盐水泥与二水石膏最优配比为7∶3,采用该固化剂制备的固化土试样28 d体积收缩率为0.08%,抗压强度为1.3 MPa。

磷石膏处理方法对水泥磷石膏稳定土性能影响

为掌握磷石膏处理方法对水泥-磷石膏稳定土(C-PG稳定土)性能的影响,弥补其强度不足和水稳定性能差的缺陷。采用水洗法、煅烧法和水洗-煅烧混合法处理磷石膏,再对C-PG稳定土无侧限抗压强度和水稳定性能进行研究。结果表明,水洗法对C-PG稳定土水稳定性能提高较显著,且水洗2次对水稳定性能的改善效果最佳;煅烧法对C-PG稳定土无侧限抗压强度提高较显著,煅烧后抗压强度提高27.6%~41.1%;相比水洗法和煅烧法,水泥剂量为6%,磷石膏掺量为4%时,水洗-煅烧混合处理后,C-PG稳定土无侧限抗压强度和水稳定性能分别提高50.43%和10.6%。因此,推荐水洗-煅烧混合法作为C-PG稳定土中磷石膏处理方法。