Showing papers on "Soil stabilization published in 2002"

Influence of the nature of organic compounds on fine soil stabilization with cement

Abstract: It is well known that organic matter may affect the cementing process in soils, but what happens when cement is added to an organic soil? Both the organic matter content and the nature of this orga...

Discrete framework for limit equilibrium analysis of fibre-reinforced soil

Abstract: A methodology is proposed for the design of fibre-reinforced soil slopes using a discrete framework. The analysis of fibre-reinforced soil using traditional composite approaches requires the implem...

Stabilization of Silty Sand with Nontraditional Additives

Abstract: A laboratory experiment was conducted to evaluate the stabilization of a silty- sand (SM) material with nontraditional chemical or liquid stabilizers. SM soil specimens were mixed with various stabilization products and compacted using a gyratory compaction machine to approximate ASTM D1557 moisture—density compaction. Each specimen was subjected to wet and dry testing following the designated cure period. Twelve nontraditional stabilizers were evaluated in this experiment, including acids, enzymes, lignosulfonates, petroleum emulsions, polymers, and tree resins. Additional specimens were stabilized with an asphalt emulsion, cement, and lime to provide a comparison with traditional stabilizers under the same mixing, compaction, and curing conditions. The analysis of the test data consisted of determining the average strength, in terms of sustained load, of three replicate specimens of each mixture. The average strength of the three replicates of each additive was compared with the average strength results...

Measured Effects of Liquid Soil Stabilizers on Engineering Properties of Clay

Abstract: Stabilization of pavement subgrade soils and base materials has traditionally relied on treatment with lime, cement, and sometimes fly ash. Marketed as alternatives to these conventional bulk soil stabilizers, a variety of concentrated liquid chemical products are sold by several companies. Most transportation agencies, however, are hesitant to specify these nontraditional liquid stabilizers without reliable data to support vendor claims of product effectiveness. Standard laboratory soil tests were conducted to measure changes in the engineering properties of five clay soils when treated with three liquid chemical products. The tests involved three reference clays (kaolinite, illite, montmorillonite), two high-plasticity natural clays, and three representative liquid stabilizers (ionic, polymer, enzyme types). Tests were conducted on untreated control soil samples and on samples treated with each product at the suppliers' recommended application rates. All of the test specimens were prepared in accordance with a specified 10-step protocol that allowed objective comparisons of the test results. Each treated and untreated soil was characterized in terms of the Atterberg limits, compacted unit weight, one-dimensional free swell potential, and undrained triaxial shear strength. Given some variation in the test samples, the test results did not show consistent, significant changes in the properties of these soils as a result of treatment with these three products. Higher application rates might yield more favorable results. Clearly, independent laboratory evaluations with project-specific soils are warranted before the use of these proprietary liquid stabilizers in the field.

A Comparative Evaluation of Various Additives Used in the Stabilization of Expansive Soils

Abstract: This paper investigates the effectiveness of using cement by-pass dust, copper slag, granulated blast furnace slag, and slag-cement in reducing the swelling potential and plasticity of expansive soils. The soil used in this study was brought from Al-Khod (a town located in Northern Oman) where structural damage was observed. The first stage of the experimental program dealt with the determination of the chemical, mineralogical, and geotechnical characteristics of the untreated soil. The soil was then mixed with the stabilizers at 3, 6, and 9% of the dry weight of the soil. The treated samples were subjected to liquid limit, plastic limit, swell percent, and swell pressure tests. Furthermore, the cation exchange capacity, exchangeable cations (Na+, Ca++, Mg++, and K+), and pH of the treated samples were also measured. The study showed that copper slag caused a significant increase in the swelling potential of the treated samples. Other stabilizers reduced the swelling potential and plasticity at varying degrees. The study further indicated that cation exchange capacity and the amount of sodium and calcium cations are good indicators of the effectiveness of chemical stabilizers used in soil stabilization.

Field Evaluation of Construction Alternatives for Roadways over Soft Subgrade

Abstract: Alternative methods for providing a stable platform over soft subgrades were evaluated using a 1.4-km section along a Wisconsin State highway that incorporated 12 test sections to evaluate 9 different stabilization alternatives. A variety of industrial by-products and geosynthetics were evaluated for stabilization. The industrial by-products included foundry slag, foundry sand, bottom ash, and fly ash as subbase layer materials. The geosynthetics included geocells, a nonwoven geotextile, a woven geotextile, a drainage geocomposite, and a geogrid. The same pavement structure was used for all test sections except for the subbase layer, which varied depending on the properties of the alternative material being used. All test sections were designed to have approximately the same structural number as the conventional pavement structure used for the highway, which included a subbase of granular excavated rock. Observations made during and after construction indicated that all sections provided adequate support for the construction equipment and no distress was evident in any part of the highway. Each of the alternative stabilization methods, except a subbase prepared with foundry sand, appear to provide equivalent or greater stiffness than that provided by control sections constructed with excavated rock. However, the foundry sand subbase is providing adequate support. Analysis of leachate collected from the base of the test sections shows that the by-products discharge contaminants of concern at very low concentrations.

Properties of Singapore marine clays improved by cement mixing

Abstract: Stabilization of soft ground by the deep cement mixing (DCM) method has become an increasingly popular method to improve stability in an excavation in soft clay and to limit movement in adjacent sub-structures. The desired increase in strength and stiffness to fulfil the intended functions can be achieved provided that the right mix proportion is adopted. To proceed with this kind of soil improvement, prediction of the strength and stiffness of the improved soil is necessary. Due to a short history of the DCM method in Singapore, there is limited data on the improved properties of local clays. This study is conducted to bridge that gap and also extends its usefulness to clays elsewhere. In the paper, the influences of three main constituents of the mixture, namely clay, water, and cement on the strength development of Singapore marine clays improved by cement mixing are investigated. Based on the experimental results, it is shown that a convenient normalization can produce a consistent pattern for evaluation of improved strength of clays from different parts of Singapore. This normalization is also shown to work for one Japanese clay. Correlations between strength and stiffness of the improved clay are also obtained. Lastly, it is shown that for a cement mixed clay there is a continual increase in strength and stiffness with time. This will help to reduce ground movement, and it will also increase the bending moment in the retaining wall. Both aspects must be considered in a design.

Cementitious stabilization of soils in the presence of sulfate

Abstract: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v CHAPTER

Selecting optimum cement contents for stabilizing aggregate base materials

Abstract: Researchers designed a laboratory test sequence to identify the optimum amount of portland type I cement for stabilizing two aggregates, limestone and recycled concrete, typically used in the Houston District. Smectitic compositions identified through mineralogical investigations corresponded with the poor performance of the untreated aggregates in preliminary testing and substantiated the need for stabilization. Samples were subsequently treated with 1.5%, 3.0%, and 4.5% cement and tested for strength, shrinkage, durability, and moisture susceptibility in the laboratory. Strength was determined with the Soil Cement Compressive Strength Test (TxDOT Test Method Tex-120-E), and a linear shrinkage test was developed to assess shrinkage characteristics. Durability was evaluated with the South African Wheel Tracker Erosion Test (SAWTET), and moisture susceptibility was assessed with the Tube Suction Test (TST). The limestone aggregate was also subjected to modulus testing. Based on these parameters, stabilized samples exhibited markedly improved performance with minimum additions of cement. Based on the results of the laboratory testing, the recommendation of this report is 3.0% cement for the limestone and 1.5% cement for the recycled concrete. For future testing of aggregate base materials to determine optimum cement contents, the joint utilization of the strength test and the TST is recommended. Sufficient quantities of cement should be added to tested samples to obtain minimum unconfined compressive strengths of 300 psi in the former and maximum average surface dielectric values of 10 in the latter. The minimum amount of cement necessary to satisfy both criteria should be recommended for pavement construction. In addition to these tentative specifications, a provisional pre-cracking procedure is also suggested in this report for further evaluation.

Utilization of an industrial waste in calcareous expansive clay stabilization

Abstract: The calcareous expansive soil in Cyprus has caused serious damage to structures. High-quality Soma fly ash admixture has shown tremendous potential as an economical method for the stabilization of the soil. Fly ash and lime-fly ash admixtures reduce the water absorption capacity and compressibility of the treated soils. Unlike some of the previously published research, an increase in hydraulic conductivity of the treated soils was obtained with an increase in percent fly ash and curing time. X-ray diffractograms indicate that pozzolanic reactions cause an alteration in the mineralogy of the treated soils, and new mineral formations with more stable silt-sand-like structures are produced. In the present study, an attempt has been made to use cation exchange capacity (CEC) values to substantiate the findings that, with increasing percentage of fly ash and curing time, soils become more granular in nature and show higher hydraulic conductivity values.

Stabilization of Dune Sand Using Foamed Asphalt

Abstract: Foamed asphalt technology has increasingly gained acceptance as an effective and economical soil improvement and stabilization technique, mainly because of its improved aggregate penetration, coating capabilities, and handling and compaction characteristics. This laboratory research program was carried out to investigate the feasible use of foamed asphalt technology in Saudi Arabia to improve the prevalent dune sands for possible use as a base or subbase material. Several variables were investigated to evaluate the relative improvement of dune sand as well as to permit the development of design procedures for the future use of foamed asphalt technology in the harsh climatic conditions of eastern Saudi Arabia. Statistical analysis of the results was employed to verify the effects of emulsified asphalt and foamed asphalt treatment, with and without the addition of Portland cement, on the strength characteristics of the treated mixes. The results displayed significant improvement in the performance of dune sand foamed asphalt mixes, as compared to that of the emulsified asphalt mixes.

Feasibility of geosynthetic inclusion for reducing swelling of expansive soils

Abstract: The feasibility of geosynthetic inclusion for reducing swelling of expansive soils was studied by performing laboratory soil-geosynthetic swell tests on an expansive soil. The test specimen measures 12 x 12 x 12 in., with a sheet of geosynthetic embedded horizontally at the midheight of the soil. To prepare the test specimen, the soil was first compacted, in 1-in. lifts, inside a wooden mold to the prescribed density and moisture content. The soil was then allowed to swell subject to wetting by soil suction. The vertical and lateral deformations of the specimen were monitored throughout the test. To assess the effect of geosynthetic inclusion, a test without geosynthetic inclusion was performed in otherwise identical conditions for comparison purposes. The test method and test results are described. On the basis of the test results, the feasibility of geosynthetic inclusion for reducing swelling of expansive soils in practical applications is addressed.

Cold in-place recycling and full-depth strengthening of clay-till subgrade soils: results with cementitious waste products in northern climates

Abstract: Saskatchewan is experiencing significant increases in commercial truck traffic due to grain transportation rationalization, consolidation of the rural grain elevator system, rural economic diversification, and expansion of resource industries. Although increasing truck traffic has long-term implications for the primary pavement system, significant increases hold immediate implications for thin paved roads; many were not originally designed to accommodate heavily loaded commercial trucks. There is a clear need to strengthen many Saskatchewan thin pavements. However, conventional structural strengthening typically involves regrading and granular subbase-base overlay systems, often too expensive because of the cost associated with aggregate hauls and regrading. As a result, the Saskatchewan Department of Highways and Transportation is investigating the use of cold in-place recycling and full-depth cementitious stabilization to strengthen Saskatchewan thin pavements. To this end, industrial waste coproducts such as coal fly ash, bottom ash, and kiln dusts are being investigated as structural cementitious soil stabilizers. The results are presented from preconstruction site investigation methods, laboratory materials characterization, and in situ quality assurance test results. Field performance after 2 years shows cold in-place recycling and cementitious stabilization to be a technically and economically feasible solution for strengthening Saskatchewan thin paved roads built on clay-till subgrades.

Improving the Response of Soil-Metal Structures during Construction

Abstract: For economic reasons, manufacturers of soil-metal bridges have strived to build these structures under the shallowest possible depth of soil cover, below the one allowed by codes of practice. For such structures, special analysis is needed to circumvent or prevent the formation of failure mechanisms that may be triggered during construction or when subjected to traffic loads. Therefore, special features, such as transverse stiffeners attached to the metal shell and the use of thrust concrete beams, may be required to assist the corrugated metal shell in carrying the loads. In this paper, a novel design is proposed for such structures in which the surrounding soil is reinforced and the metal shell is tied into the soil. A finite-element analysis of long span soil-metal structures with shallow soil cover is carried out using these two designs. The analysis is verified and substantiated using field data obtained during the construction of an 18 m soil-metal bridge. Comparing the structural response from the two designs shows that the latter design can lead to a superior structure.

Strength-deformational characteristics of eps beads-mixed lightweight geomaterial subjected to cyclic loadings

Abstract: A laboratory experimental study was carried out to investigate fundamental engineering properties of lightweight soil mixed with EPS (expanded polystyrene) beads and treated with portland cement. The soil used is a cohesive soil with a high natural moisture content and is often disposed as a surplus soil at a construction site. Both static and cyclic loading triaxial compression tests under the unconsolidated unconfined conditions were conducted for the mixture specimens compacted in laboratory. Effects of mixing rate, stress conditions, and numbers of replicates on the deformational behaviors were discussed. It was found from the results that these artificial soil mixtures with the compressive air-entrained beads showed different mechanical behavior from natural soils, the aggregates of which are composed of incompressible solid particles.

Subgrade Stabilization Using Recycled Asphalt Pavement and Fly Ash Mixtures

Abstract: This paper describes field and laboratory testing conducted to evaluate the performance of soft subgrade stabilized with combinations of fly ash as a chemical stabilizer and Recycled Asphalt Product (RAP) as a mechanical stabilizer. Field-testing consisted of Dynamic Cone Penetrometer (DCP) tests. Laboratory testing consisted of unconfined compression strength tests, and gradation analysis. The controlled laboratory testing provided the opportunity to compare results with field tests. DCP tests revealed a time dependent gain in stability due to the cementing action of the fly ash. Grain size distribution data also shows that the addition of RAP shifts the distribution curve left and increases the quantity of aggregate in the mixture. Laboratory results show that the unconfined compressive strength of fly ash treated soil/RAP mixture is about five times that of non-fly ash treated samples. Soaking the sample prior to testing then showed that the unconfined compression strength is reduced by a factor two for samples compacted dry of optimum moisture content. Samples wet of the optimum moisture content show no strength loss.

Method of reducing eluting quantity of heavy metal in cement-based solidified soil using artificial zeolite

Abstract: PROBLEM TO BE SOLVED: To prevent the elution of heavy metals from the ground treated with a cement-based solidifying material or a regenerated aggregate, which is a problem of the soil improvement, that is, the phenomenon of the elution of heavy metals occurs probably depending on the physical property of the soil to exceed the environmental standard in the case that cement and the cement- based solidifying material is used. SOLUTION: The method of reducing the elution of the heavy metals is achieved by adding artificial zeolite when executing a deep mixing method of soil stabilization, a cement-based chemical injecting method, a surface mixing method, a subgrade stabilization method, cement stabilization method, a soil cement column wall method or the like with the cement and the cement-based solidifying material.

Engineering properties of soil-fly ash subgrade mixtures

Abstract: The effects of adding fly ash to soil were evaluated in some common soil tests. When fly ash and soil are mixed and compacted immediately, the fly ash causes the mixture to have a higher dry unit weight, by filling in voids with ash particles. As a soil-fly ash mixture sits uncompacted, flocculation and agglomeration of the soil particles occurs as the fly ash sets up. This compaction delay time causes the compacted unit weight and strength gain to decrease, especially after the ash sets. Fly ash addition can also increase the freeze/thaw durability of a soil. Strength gain of soil-fly ash mixtures is also affected by curing temperature. Below freezing, 32 degrees F (0 degrees C), the mixtures gain no strength, while the strength gain increases as curing temperature increases. Fly ashes with high sulfur content react with the clay minerals and water in soil to form expansive materials, which break the mixture up, resulting in no long term strength gain, but low sulfur ashes have shown large strength gain in just over two years of curing. Fly ash can also be added to extremely wet soil to dry it out, while, at the same time, increasing the strength of the soil. The engineering properties of fly ash stabilized soil prove fly ash can be useful as a soil stabilizer.

Study on lignosulfonate and its grafted polymers as sandy soil stabilizers

Abstract: Polymer stabilizers can improve the structure of sandy soil,and may be used in controlling the soil desertification.The effects of non woody lignosulfonate and its grafted polymers on stabilizing sandy soil were studied.It is suggested that the lignosulfonate itself is not an applicable stabilizer,but after grafted with acrylic monomers its efficiency on sandy soil stabilization is improved.The grafted polymers are sprayed on the surface of sandy soil,with application dosage of 10?g/m 2 ,the sandy soil can withstand wind erosion with speed of 76?km/h.By polymers grafted with non ionic monomers,the sandy soil has higher resistance on water erosion.The polymer stabilizers applicable for improving sandy soil should have higher molecular weight,certain hydrophilicity and degradability,and be economical and environment friendly.

Compaction and permeability study of a soil stabilised with flyash, lime and Na2CO3

Abstract: The disposal problems offlyash can be reduced by utilising it in large quantities in various engineering works. In the present study, the possibility of use offlyash to improve the compaction and permeability properties ofa locally available soil has been investigated experimentally. Apart from this, the effect of lime as stabilising agent and Na 2 CO 3 as an additive, when added to the soil-flyash combination has also been investigated. A combination of 70% soil, 28% flyash, 1% lime and 1% Na 2 Co 3 has been found to give best results against the optimum use offlyash in soil.

Construction method of soil cement composite precast pile

Abstract: PROBLEM TO BE SOLVED: To provide a construction method of a soil cement composite precast pile with little discharge of earth and sand from an excavated hole during excavation and when sinking the pile. SOLUTION: In this construction method of the soil cement composite precast pile, the precast pile with spiral blades is screwed to penetrate into a soil cement column body constructed by a mechanical deep mixing method of soil stabilization. The precast pile with the spiral blades has the spiral blades near a pile head and near a lower end part and further at least one spiral blade in the middle, and a non-constructed layer not less than the depth equivalent to the half of the diameter of the soil cement column part is provided between the upper end part of the soil cement column body and the ground surface.

Application of soil stabilization method by freezing to shield tunnelling

Abstract: AbstrcatTo overcome the difliculty of comtruction by shield?driven machine in flexible soil layers,the soil stabilization method by artificial freezing is used.The scheme of locally freezing in vertical direction is selected and perfect results have been gained.The reinforced soil had a high strength and uniformity and the underwater is well resisted.

The french technical guide on soil stabilisation with lime and hydraulic binders

Abstract: The technical guide, published in January 200, comprises three sections. The first part presents general notions relative to full treatment with fine and/or hydraulic binders. It covers presentations of: the mode of action of the different products on the various types of soils; the methodology to be followed for the field and laboratory investigations at project level; general aspects of quality assurance. The second part elaborates aspects which are specific application of soil treatment to road embarkments. It considers two types of main objectives: the re-use of soils with too high water content at the time of the works in order to be used as it is; and, the construction of some particular zones of embankments for which durable mechanical characteristics are looked for. The third part considers successively the project investigations, the techniques and equipment for soil treatment and quality assurances for these applications.

Stabilizing landslides using rammed aggregate piers

Abstract: Very dense and stiff rammed aggregate pier elements have been used as a soil reinforcement method since 1989 beginning in the United States and propagating to Europe and Asia. Reliable performance coupled with cost and construction time saving, have made this ground improvement method an attractive alternative to gravity walls and to reinforced earth systems for landslide stabilization. This ground improvement system is unique with modulus of stiffness of the piers measured to be 10 to 45 times greater than unimproved soils. Its unusually high internal shearing resistance is highly effective as a means of stabilizing failing slopes, and providing increased factor of safety against global failures within displaced soils. This paper presents the construction processes, technical concepts as well as the feasibility of using the rammed aggregate pier system as a “dowel pile” system within the residual soil slopes.

Case study of soft soil stabilization with phosphorous gypsum

Abstract: Engineering practice proved that:the strength of stabilized soil stabilized by cement with phosphorous gypsum is much higher than by cement only.It broadens the scope of soil suitable to be stabilized and brings remarkable technical,economic and environmental benefits.The strengthening effect to different soil by phosphorous gypsum is different,so the ratio of stabilizers should be adjusted when applied to multi-layer soil.Correct evaluation to strengthening effect could be obtained if,and only if,proper test method is used.