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1.
Many innovative ameliorating techniques including chemical stabilization have been in practice for improving the behaviour of problematic, highly expansive clays. This paper presents a comparative study on the effect of fly ash (FA) and rice husk ash (RHA) on index and engineering properties of an expansive clay. Liquid limit (LL), plastic limit, plasticity index (PI) and free swell index (FSI), and coefficient of permeability (k), unconfined compressive strength and swelling pressure were determined at varying quantities of FA and RHA. Coefficient of permeability, swelling pressure and unconfined compressive strength of the FA-clay and the RHA-clay blends were determined at their respective OMC and MDD obtained from Proctor compaction tests. LL, PI and FSI decreased significantly with increasing FA and RHA contents. Coefficient of permeability, however, increased with additive content. Further, swelling pressure of the blends decreased with increasing additive content. 相似文献
2.
B. R. Phanikumar Jagapathi Raju m Ramanjaneya Raju e 《Geomechanics and Geoengineering》2020,15(1):64-77
ABSTRACTExpansive soil subgrades, which are subjected to dual swell-shrink problem consequent upon absorption and evaporation of water, need to be improved by chemical stabilization or compacted cushion or geosynthetic reinforcement in order that pavements constructed over them are even, stable and safe. This paper presents extensive experimental data on plasticity, free swell index (FSI) and compaction characteristics of a highly swelling expansive clay stabilized with varying silica fume contents. In another series of tests on a laterite soil to be used as a cushion over the expansive clay subgrade, plasticity properties, compaction characteristics and strength characteristics were determined at varied silica fume contents. Further, CBR of the expansive clay subgrade was determined in the laboratory stabilizing it with varied silica fume contents and providing a cushion of 50 mm thickness of silica fume-stabilized lateritic soil. Liquid limit (LL), plasticity index (PI) and free swell index (FSI) of the expansive clay decreased with increasing silica fume contents. The compaction and strength characteristics of both the soils improved with silica fume stabilization. The CBR of the expansive clay provided with silica fume-stabilized cushion improved significantly. 相似文献
3.
Numerous studies demonstrated the possibility of utilizing fly ash in the construction of embankments, road subgrades and
stabilization of a wide range of soils. The present investigation aims at determining the optimum fly ash (OFA) for mechanical
stabilization of expansive soils. Four different soils were tested for compaction characteristics and unconfined compressive
strength with and without the addition of fly ash to determine the OFA. The liquid limit (LL) and the fraction coarser than
425 μ (CF) of these soils range from 50 to 120 and 25 to 70%, respectively. An experimental strategy called two-factor factorial
design was adopted in the conducting experiments. LL and CF present in the soil are the two factors considered to influence
the OFA content. Factorial experimentation enables relative quantification of the effect of each factor as well as their interaction
with the OFA. The OFA was found to range from 5 to 40% depending upon the two factors. The LL and the CF were found to have
dominating influence on OFA content in that order, whereas the interaction effect of these two factors was marginal to fair.
A statistical regression model was developed for determination of the OFA in terms of the influencing factors. The validity
of the model developed was verified by conducting laboratory tests on two more soils that were not used in the development
of the model. Swell potential and swelling pressure of expansive soils were reduced to non-critical levels when treated with
OFA. 相似文献
4.
压实度是道路、房建、水利等工程领域评价土体压实质量的重要参数,与土体含水率和电导率密切相关。而频域反射技术(frequency domain reflectometry,FDR)可用于快速测定土体含水率和电导率。首先利用频域反射技术分别对多种压实状态下红黏土、膨胀土和黄土的含水率、电导率进行测量;然后对含水率测值进行室内标定,得到3种土的含水率标定曲线;通过偏最小二乘回归分析方法(partial least squares regression,PLSR)建立了3种土体的压实度-含水率-电导率之间的经验关系,并与实测值进行了对比分析;再根据扫描电子显微镜(scanning electron microscopy,SEM)和压汞法(mercury intrusion porosimetry,MIP)试验结果分析了其微观机制;最后对拟合公式得到的压实度预测值进行随机试样验证,建立与实测值的误差评估体系,结果表明基于压实度-含水率-电导率之间的关系而提出的拟合公式预测压实度的精度较高。相关研究可为道路、房建、水利等工程中土体压实度的快速检测提供参考。 相似文献
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以南水北调中线工程原状强、中膨胀土/岩为研究对象,开展压力板试验与双环注水试验,结合试验结果与土-水特征曲线(SWCC),对比研究不同性质膨胀土和膨胀岩的持水性能及影响因素,计算并分析水体积变化系数的变化规律,在该基础上重点探讨渗透系数的变化特征及其与基质吸力的非线性关系,总结出膨胀土/岩的渗透特性及其规律。结果表明,膨胀土/岩的持水特性受岩土的物理性质、矿物成分与结构特征的影响,膨胀潜势强、细颗粒含量大、孔隙结构小的试样有着较低的脱水速率;渗透系数和水体积变化系数均随含水率的减小而减小,变化特征受到膨胀潜势与干密度的共同影响,并与基质吸力呈幂函数关系。研究成果可为工程建设提供计算参数及理论依据。 相似文献
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Hassan Mujtaba Tahir Aziz Khalid Farooq Nagaratnam Sivakugan Braja M. Das 《Journal of the Geological Society of India》2018,92(3):357-362
Improvement in engineering properties of expansive soils by mixing ground granulated blast furnace slag (GGBFS) is the main focus of this research. For this purpose two expansive soil samples were collected from DG Khan and Sialkot areas (Pakistan). Classification tests revealed that DG Khan sample belonged to fat clay (CH) while Sialkot soil was lean clay (CL) as classified by Unified Soil Classification System. GGBFS has been added in varying proportions between 0 and 55% in these soil samples to study its role in stabilizing these expansive soils. Based on the laboratory test performed on composite soil samples, it was observed that maximum dry unit weight increased up to 10 % by adding 50% GGBFS in both samples. California bearing ratio (CBR) value showed an increase from 3.2 % to 11.5% for DG Khan soil while CBR values varied from 2.4% to 10.7% for Sialkot soil by mixing 50% GGBFS. Addition of 30 % GGBFS to DG Khan soil reduced swell potential from 8 % to 2 % while in Sialkot soil, 20 % addition of GGBFS reduced swell potential from 5 % to 2 %. Unconfined compressive strength of remoulded sample cured for 28 days increased by about 35% with the addition of 30%GGBFS. The results indicated that mixing of GGBFS in the expansive soil samples have a marked increase in their engineering properties. Also, it is an affective and environmental friendly means to dispose waste of steel industry. 相似文献
9.
膨胀土工程地质特性研究进展 总被引：1，自引：0，他引：1
根据近年来国内外学者围绕膨胀土工程地质特性取得的研究成果,着重从胀缩性、裂隙性、超固结性、强度、渗透性、微观结构及工程处治技术等几个方面总结了该课题的研究现状及进展,得到如下认识:（1）胀缩性主要取决于强亲水性黏土矿物含量、水/力边界条件及初始状态,在干湿循环条件下具有不可逆性,关于胀缩机理学界存在不同的观点;（2）裂隙性是膨胀土区别于一般土体的显著特征之一,裂隙的存在会极大破坏土体的整体性,弱化力学性质,是许多工程地质问题的直接或间接原因,裂隙形成过程与膨胀土矿物成分、微观结构和干燥过程中的内应力发育状态有关;（3）超固结性使膨胀土具有较大结构强度和水平应力,易在开挖过程中引起较强的卸荷效应,是促进边坡失稳的重要因素;（4）膨胀土的强度随干湿循环次数增加而逐渐降低,并最终趋于稳定,其中裂隙发育和土结构调整在此过程中起关键作用;（5）渗透性在很大程度上受裂隙的控制,但目前关于两者之间的定量关系还缺少系统研究;（6）微观结构反应了膨胀土的形成条件和应力历史,是决定其宏观物理力学性质的主要因素,开展微观结构研究是掌握膨胀土宏观性质本质规律的重要途径。在工程处治技术上,本文重点介绍了近些年发展起来的膨胀土路堤物理处治技术和路堑边坡柔性支护技术。最后,针对该课题的研究现状,笔者提出了今后的研究重点和方向,主要包括胀缩性和力学性质的各向异性、裂隙形成的力学机理、裂隙形态特征与工程地质特性之间的定量关系、宏-微观力学模型耦合问题及多场耦合作用下膨胀土工程性质响应特征等。 相似文献
10.
Compressibility and swelling characteristics of Al-Khobar Palygorskite, eastern Saudi Arabia 总被引：1，自引：0，他引：1
Expansive soils are found in different locations in eastern Saudi Arabia. The area is arid with high temperatures, highly variable humidity and an excessive rate of evaporation compared to the low precipitation. This resulted in the formation of water sensitive soils. In the present investigation, line valve buildings for a sweet water feeder (1118 mm in diameter) were constructed on a highly expansive material consisting mainly of brown palygorskite and gray palygorskite with thin sheets of gypsum and limestone. Block samples from both palygorskites were brought to the laboratory and cores as well as remolded samples were obtained from the blocks. The two palygorskites were found to be highly plastic and have a very high swelling potential. The liquid limit (LL) and plastic limit (PL) values for the brown palygorskite are 261% and 140%, respectively. The gray palygorskite has a LL of a 285% and a PL of 123%. The oedometer free swell tests for the two palygorskites produced an expansion ranging between 31.8% and 42.5% for the remolded samples. However, the expansion for cores ranges between 8.3% and 19.3%. The constant volume pressure tests produced a stress in excess of 4240 kPa. The swell potential reached a steady state after four days while the swelling pressure reached a steady state in about 3 h. The paper addresses the geology of the area, the characterization of the geomaterial including mineralogical composition using X-ray diffraction and SEM techniques and the swelling characteristics of the material. 相似文献
11.
弱膨胀土工程特性及其路基处治对策 总被引：3，自引：1，他引：2
针对湖北襄-荆高速公路膨胀土,在室内开展了弱膨胀土的压实特性、胀缩性状、力学特性试验研究,发现压实膨胀土的工程性状受含水率与压实度的影响,胀缩特性是膨胀土的固有特性,其大小取决于起始湿度和密度;击实膨胀土的最佳含水量和最大干密度随击实功变化而变化,压实功愈大,土的最大干密度也愈大,而对应的最佳含水量愈小;膨胀土的CBR值随其含水率的变化规律类似于击实曲线,但CBR峰值含水率大于最佳含水率,为深入认识膨胀土的工程特性提供了帮助。因此,利用弱膨胀土填筑路堤时,不仅要考虑经过击实后的土的性质,而且还要考虑在填方建成、条件改变后土的性能;膨胀土路堤填筑除考虑压实度与CBR值要求外,尚需考虑胀缩总率的影响。最后,推荐了弱膨胀土路堤结构型式,并提出了弱膨胀土用于路堤填筑的控制标准。 相似文献
12.
A GIS model for preliminary hazard assessment of swelling clays,a case study in Harran plain (SE Turkey) 总被引：2，自引：1，他引：1
Swelling behavior of clayey soils regarded as a hidden disaster, causes a great deal of damage in light hydraulic structures
such as drinking water network, irrigation pipes or open canal linings through which water can easily leak and penetrate into
soil during loading and unloading stages. Early identification during site investigation and laboratory testing is extremely
important to ensure that the appropriate design strategy is adopted. The clay soils having swelling potential are generally
found in arid and semi-arid regions, such as in the Şanlıurfa-Harran plain located in the southeast of Turkey. The problems
associated with swelling clays occurred for the lightweight hydraulic structures constructed in Turkey have been met during
the construction of irrigation structures in the scope of Southeast Anatolian Project as the Turkey’s greatest water resources
project. Therefore, the identification of such soils and the assessment of their swelling potential parameters are necessary
for hazard mitigation planning and land-use management. In this scope, extensive geotechnical study is executed for an investigation
area. The samples were obtained from the Harran plain where many irrigation canal structures are constructed, and geotechnical
study was performed on these samples. Atterberg limit tests often provide the basic field information to substantiate the
soil’s swelling nature. The plasticity index (PI) and liquid limit (LL) values are also used extensively for classifying swelling
soil and should always be determined during preliminary investigations. Because of this, LL and PI are assessed by using geographical
information system (GIS)-based computer software, and LL and PI contour maps are created. Swelling percentages of the soil
samples were carried out on both undisturbed and compacted soil samples by using direct methods. As a result of this extensive
study, the values of swelling percentages determined for each location are used to obtain the swelling potential hazard map
of the area by means of a GIS program. The results of GIS analyses for this area indicate that the analyses based on a lot
of data introduce meaningful results for this study. It is expected that these maps will be a useful tool for planners and
engineers in their efforts to achieve better land-use planning and to decide necessary remedial measures. 相似文献
13.
膨胀土的胀缩等级判定对膨胀土地区工程建设具有重要的意义。为此,本文提出了一种基于支持向量回归机（SVR）模型的膨胀土胀缩等级预测方法。基于肯尼亚“蒙内铁路”沿线膨胀土的土工试验数据,以土体自由膨胀率作为预测目标,构建了包含两种不同预测指标体系的膨胀土胀缩等级预测模型。模型I以液限、塑限、塑性指数、3种不同粒径的颗粒含量（< 0.075、0.075～0.25、0.25～0.5）、土的类型为输入参数,模型II以液限、塑限、塑性指数、粒径< 0.075的颗粒含量、土的类型为预测参数。两个模型在预测时采用Linear、Polynomial、RBF和Sigmoid核函数进行训练。结果表明:（1）当预测采样次数达到1000次时,训练模型均趋于稳定;（2）整体而言,模型I的预测精度要优于模型II,模型I中采用RBF核函数建立的模型给出了最高准确率86.6%,其次为Linear核函数（准确率82.9%）和Sigmoid和函数（准确率75.1%）。模型II中采用RBF核函数建立的模型给出了最高准确率77.4%,其次为Linear核函数（准确率74.3%）和Sigmoid和函数（准确率72.9%）;（3）采用Linear函数、Sigmoid函数和RBF函数作为核函数模型对44组未知胀缩等级的土样预测时,模型I中三者预测结果相同的数量占比为73%,其余组土样的预测胀缩等级相同或相邻,不存在“越级”现象,模型II中三者预测结果相同的数量占比为68%,不存在“越级”现象。最后,通过与模糊层次分析法评价结果对比,进一步证明了本文研究结果可为肯尼亚等类似地区工程建设中膨胀土的胀缩等级预测和处理提供依据。 相似文献
14.
Nanyang expansive soil is investigated in its unsaturated state in this paper. The wetting–drying cycle tests of soil–water characteristics of Nanyang expansive soil have been performed in the laboratory. The test results show that the soil–water characteristic curve of the pre-load specimen can well reflect the soil property function of expansive soil. The strength features of the different suction states of the unsaturated expansive soil are also investigated. The hyperbolic model of the suction strength is presented and the parameters of this model are easily determined by tri-axial tests of unsaturated soils. The hyperbolic model is conveniently applied to predict suction strength of an unsaturated soil. 相似文献
15.
基于膨胀土可以直接用作路堤填料的分类指标体系,在室内开展了3种不同膨胀土的物理性质、击实性状、强度特性试验研究,验证广西百隆高速公路膨胀土路段的膨胀土也可以直接用作路堤填料,并结合现场实体工程的效果验证用改进CBR值、改进CBR膨胀量和稠度3指标作为膨胀土路堤填料的分类指标体系的合理性。通过对标准CBR试验和改进CBR试验的对比,进一步验证了用改进CBR试验法评定膨胀土承载强度的合理性。由百色膨胀土的不浸水CBR试验,说明可以用封闭包盖对百隆路膨胀土路堤进行物理处治。实体工程中采用土性最差的1号膨胀土做填芯和用红黏土包边,得到的工程效果令人满意。由室内外试验结果,可以得出这3种百色膨胀土都可以直接用作路堤填料。 相似文献
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土壤可见光和近红外波段(400~2 500 nm)反射光谱信息包含了大量土壤物理化学参数,土壤反射光谱测量简单、快速,无需破坏样品,而且还可以通过高光谱遥感方法制图。文中使用江苏国土生态地球化学调查中获取的大量土壤样品,研究了土壤阳离子交换量(CEC)、有机质含量、pH值、铁氧化物类型、铁铝硅等常量元素含量等重要土壤生态地球化学参数的光谱反应。结果显示,土壤CEC是进行光谱预测非常成功的参数,1 400、1 900和2 200 nm附近一阶导数光谱(FD)值或短波方向反射率值均可以很好地反映土壤CEC的大小;土壤有机质含量、铁氧化物类型、铁铝硅含量均可以在反射率光谱或其一阶导数(FD)值找到相关波段;土壤导数光谱存在的A、B、C和D峰使反射光谱方法不仅能够定量铁氧化物总量,还能鉴别铁氧化物矿物类型(针铁矿和赤铁矿)及其相对含量;江都土壤光谱的656 nm附近FD值与pH有很大相关性,但是江苏样品显示pH值光谱经验预测具有区域依赖性,可能与土壤类型有关,说明pH与光谱参数之间的关系并非一般的线性关系,而有更复杂的机制。 相似文献
18.
膨胀土路堤的化学改性试验研究 总被引：1，自引：0，他引：1
膨胀土是一种具有特殊工程性质的土,它对土木工程有着巨大的影响和危害。本文针对公路膨胀土路堤填料改良提出的PAS化学改性剂包边处理新方法,对其改性原理及其特殊的施工工艺做了详细介绍,并通过多项试验研究了改良前后膨胀土胀缩性、强度特性等方面的变化。研究表明,PAS生态改性处理膨胀土是一种有效的方法,经处理后的膨胀土胀缩性显著降低,强度和水稳定性得到大幅提高。且PAS不会改变原土壤植被育培能力,改性边坡可以结合植物固坡的方法进行生态防护。PAS改性处理与远距离运土路基填料置换相比,具有很大经济优势,特别是在高塑性膨胀土大量分布的地区,PAS改性剂处理膨胀土路基具有很好的推广价值。 相似文献
19.
Vahid Khosravi Faramarz Doulati Ardejani Saeed Yousefi 《Environmental Earth Sciences》2017,76(13):459
Soil pollution by arsenic is a serious environmental problem in many mining areas. Quick identification of the amount and extent of the pollution is an important basis for developing appropriate remediation strategies. In a case study, 55 soil samples were collected from a highly heterogeneous waste dump around the Sarcheshmeh copper mine, south east Iran. Samples’ visible and near-infrared (VNIR) reflectance spectra were measured, transformed to absorbance and then pre-processed using Savitzky–Golay first-derivative (FD) and Savitzky–Golay second-derivative (SD) transformation methods. The obtained spectra were then subjected to three regression models including principal component regression (PCR), partial least squares regression (PLSR) and support vector regression (SVR) for predicting arsenic concentration. The best prediction accuracies were obtained by SVR and PLSR methods applied on first-derivative pre-processed spectra with R 2 values of 0.81 and 0.69, respectively. It was found that VNIR spectroscopy is a successful method for predicting As concentration in contaminated soils of the dumpsites. Study of the prediction mechanism showed that the intercorrelation between arsenic and spectral features of soil including iron oxy/hydroxides and clay minerals was the major mechanism enabling the prediction of arsenic concentration. However, higher values of correlation coefficients at ~460, ~560 and ~590 nm suggested the internal association between arsenic and iron minerals as the more important mechanism for prediction. This conclusion supported previous speciation studies conducted in the same waste dump using improved correlation analysis and chemical sequential extraction method. 相似文献
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基于工程包边法的膨胀土抗剪强度干湿循环效应试验研究 总被引：4，自引：0，他引：4
根据包边法施工中填芯重塑膨胀土和包边石灰改性膨胀土的实际工程状态,设计了反映其运营状态的干湿循环过程,对6次干湿循环前、后膨胀土的强度特性进行了较为系统地试验研究。结果表明,在压实度为90%~96%时,干湿循环前重塑膨胀土和石灰改性膨胀土慢剪强度及强度参数均随干密度单调增加,而干湿循环后其黏聚力c随干密度单调增加,干密度对内摩擦角φ的影响则明显变小;重塑膨胀土和石灰改性膨胀土干湿循环后的残余强度受干密度制约性不大,但干湿循环前、后重塑膨胀土和石灰改性膨胀土的残余强度参数存在差异,且干湿循环幅度对膨胀土强度参数也有一定的影响;在分析干湿循环前、后反复剪切试验结果及膨胀土边坡长期破坏机制的基础上,认为对于膨胀土路堤,在进行强度参数选取时宜适当考虑干湿循环及其幅度对于残余强度参数的影响;利用石灰改性膨胀土包边处理填筑膨胀土路基较为适宜。 相似文献