Showing papers on "Soil stabilization published in 1996"

Soft Ground Improvement in Lowland and Other Environments

Abstract: The presence of thick deposits of soft clay combined with the effects of ground subsidence cause problems for engineering constructions for lowland areas such as the Central Plain (Chao Phraya) of Thailand The ground subsidence is caused by the excessive extraction of ground water To mitigate such natural geological hazards, different soil/ground improvement methods have been studied, namely: mechanically stabilized earth (MSE) embankments, granular or sand compaction piles, vertical drains, and the lime/cement deep mixing method In view of their proven performance, durability, constructibility, short time schedule, and low costs, mechanically stabilized earth (MSE) or earth reinforcement techniques seem to be very suitable and favorable aboveground soil improvement methods of embankment fills on subsiding ground This method can be most appropriately combined with the various belowground improvement techniques such as vertical drains, sand compaction piles, and the lime/cement deep mixing method Thus, the combined aboveground soil improvement with belowground subsoil improvement schemes can be a viable alternative to the existing method of supporting earth embankments and landfills with precast concrete piles, which may prove detrimental and more expensive in a subsiding environment

Engineering Behavior of Lime-Treated Louisiana Subgrade Soil

Abstract: Lime stabilization is often used to treat subgrade soils when they are soft and cohesive in nature. A study was conducted to investigate the engineering behavior, including the resilient and strength behaviors, of a lime-treated subgrade soil. The lime treatment procedure was adapted from the specifications of the Louisiana Department of Transportation and Development. Silty clay, a soil often found in Louisiana subgrades, is used as a base soil. A summary of various engineering properties of a lime-treated soil from resilient modulus, unconfined compression strength, and California bearing ratio (CBR) tests conducted at five moisture content and dry density levels is provided. Tests were also performed on the raw soil without lime treatment, and these results were compared with those of tests with the lime-treated soil. The comparisons indicate that the present lime treatment method results in an increase in strength and resilient modulus properties and a decrease in plasticity characteristics and plastic strains. A regression model with three constants was used to analyze the resilient modulus test results. The model constants are presented as functions of soil properties. Resilient modulus correlations that use either CBR or unconfined compression strength, moisture content, dry density, degree of compaction, and stresses as dependent attributes are developed.

Modification of clay soils using lime

Abstract: The paper examines the changes brought about in different clay soils by the addition of relatively small quantities of lime which can produce considerable benefits both in the long term and during construction. The different effects that occur with different clay types are highlighted and the quantities of lime required to achieve these effects in each case are discussed. These include the hydration of quicklime causing drying of clay soils on site and the modification of a clay soil to a material that is more workable and stronger. Details are given of changes in plasticity of British and Canadian clays, London Clay and three Jurassic Clays. Methods of construction are considered in the light of the recommendations made from laboratory test data. For the covering abstract see IRRD 887532.

Utilization of lime, slag and fly ash for improvement of a colluvial soil in New South Wales, Australia

Abstract: In Australia, colluvial soils form large terrains which are often subjected to considerable erosion and mass movement. This study presents a laboratory evaluation of the improvement effected by hydrated lime, milled blast furnace slag and fly ash on a fine grained (erosive) colluvial soil in New South Wales, Australia. Geotechnical tests were conducted to determine the compaction and consolidation characteristics and the compressive and shear strength properties of the blended and natural soil specimens. The effect of these additives on the Atterberg limits and pH levels is also investigated. As large amounts of fly ash and steel slag are produced in New South Wales, it is economically attractive to utilize these industrial by-products for ground improvement rather than employing conventional methods such as lime treatment. This study demonstrates that for the colluvial soil tested, milled slag is the most effective in terms of improving the internal friction angle of the treated soil, while lime is the most suitable for achieving the optimum compressive strength. Non-pozzolanic fly ash is found to be inappropriate as a soil improving agent. The cost of ground treatment using the various additives is also estimated and compared.

Pile response due to unsupported excavation-induced lateral soil movement

Abstract: In this paper, a two-stage analysis involving the finite element method and the boundary element method is used to study pile response due to excavtion-induced lateral soil movements, focusing on u...

Analysis of Deep Excavation with Column Type of Ground Improvement in Soft Clay

Abstract: To minimize the ground settlement induced by the excavation, the column type of ground improvement has been used in many parts of the world, possibly due to the fact that this type of soil improvement is relatively easily produced and conceptually understood. However, an analysis method and design concept has not yet been established at this time. In this paper, a method for evaluating composite material properties of the treated soil mass is proposed, in which the treated soil area is replaced by a single material during analysis. This allows a three-dimensional analysis to be performed with less computer storage and computation time. Furthermore, a slight modification was made on the method, which makes plane strain analysis also applicable to the column type of soil improvement. The analysis method was supported through a model test and a case history.

Use of cement kiln dust in stabilizing clay soils

Abstract: This report contains current information on the use of cement kiln dust (CKD), both exclusively, and in combination with other stabilizing materials such as lime, portland cement, and fly ash in stabilizing clay soils. The data on the type and level of CKD additions and the resulting engineering properties of the modified clay soils such as unconfined compressive strengths, Proctor moisture-density relationships, California bearing ratios (CBR), liquid- and plastic-limits, swelling, shrinkage, and permeability characteristics are documented. The informational gaps are identified and needed additional work is recommended.

Solidification/Stabilization of Phenolic Waste Using Organic-Clay Complex

Abstract: The solidification/stabilization (S/S) process is applicable to soil contaminated by metals and other inorganics. However, this process is not currently viewed by the U.S. Environmental Protection Agency (EPA) as applicable for remediation of soils contaminated solely with volatile organic compounds, because these organic compounds have been shown to have a detrimental effect on the macrostructural properties of ordinary portland cement (OPC) and could be released during the mixing and curing process. The aim of the present study is mainly to investigate the feasibility of using quaternary ammonium-modified clays (organophilic clays) to stabilize organics (phenol, 2-chlorophenol, and 2,4-dichlorophenol) in contaminated soils prior to conventional cement-based solidification. The effectiveness of the S/S process, using organophilic clays, was evaluated, based on experimental findings from batch sorption, leachability of hazardous constituents, unconfined compressive strength, and permeability tests. Results from these experimental tests indicate that the use of organophilic clay as a presolidification adsorbent gives a successful S/S process in the treatment of phenol-contaminated soils.

AASHTO layer coefficients for cement-stabilized soil bases

Abstract: Layer coefficients of cement-stabilized soil were determined for use in the American Association of State Highway and Transportation Officials (AASHTO) pavement design method. The soils were an A-3 fine sand and an A-6 silty clay. The silty clay was blended with three different amounts of concrete sand. Cylindrical specimens of three differing cement contents were molded and tested for static compressive chord modulus and unconfined compressive strength. Layer coefficients were determined by using the modulus values with the AASHTO pavement design guide's layer coefficient nomograph; the coefficients ranged from 0.09 to 0.27, depending on soil type, sand content, and cement content. Regression equations based on strength, dry unit weight, and cement content were developed to allow estimation of layer coefficients. Layer coefficients were shown to increase with increasing cement content, dry unit weight, and, for the sand-clay mixtures, sand content.

Landslides: investigation and mitigation. chapter 17 - stabilization of soil slopes

Abstract: The subject of this chapter is the stabilization of soil slopes. Emphasis is on recent case histories and innovations in slope stabilization techniques since 1978. The discussion is organized around the following three approaches to the design of stable slopes: (1) Avoid the problem; (2) Reduce the forces tending to cause movement; and (3) Increase the forces resisting movement.

Measuring and Modeling Time Dependent Soil Behavior

Abstract: This proceedings presents a series of papers on both laboratory and field investigations, as well as constitutive modeling efforts, that all deal with the time dependence of soils and its influence on their response to loading. Two state of the art summaries, one on laboratory and field investigations, and one on modeling, are presented to provide overviews of the current state of knowledge. Papers are included dealing with a variety of areas in which time effects play a role. These include soil reinforcement applications and cyclic behavior, as well as the range of identified time dependent behavior, i.e., creep, relaxation, constant strain rate and consolidation. A wide range of soil types are described, including sands, marine clays, weathered tropical clays, glacial till, high plasticity clays, and structured soils. The influence of other factors such as temperature, degree of soil structure and loading conditions (e.g., cyclic, plane strain and triaxial) are taken into account. The papers in the volume are intended to provide an update on the state of knowledge and new application areas in which time dependent behavior plays a critical role.

Evaluation of the use of coal combustion by-products in highway and airfield pavement construction

Abstract: The objective of this study was to exploit the beneficiation and utilization of coal combustion by-products (CCBPs) as low-cost alternate aggregates and stabilizers in roadway and airfield construction A literature review and laboratory investigation were performed to investigate the use of CCBPs in three highway construction applications: (1) fly ash for subgrade stabilization; (2) flue gas desulfurized (FGD) gypsum and Gypsite for base and subbase construction materials; and (3) bottom ash (with sulfur modification) in asphaltic concrete mixtures Results from field trials utilizing CCBPs in roadbases indicate good to excellent performance characteristics and negligible environmental impact Class C and lime-enhanced Class F fly ashes were shown to be effective stabilizers for both clayey and sandy soils The field trials showed that sulfate-resistant cements and Class C fly ashes provide a wide range of strengths in stabilized sulfate and sulfite roadbases The use of sulfur improved the crushing strength and reduced the asphalt demand associated with bottom ash in asphaltic concrete mixtures Sulfur modification required asphalt contents equal to and often less than for mixtures using conventional aggregates Based on its availability, lower cost, safe use, and demonstrated performance, CCBP materials should find increasing use especially in those regions of Texas experiencing dwindling or non-existent aggregate sources

Soil stabilization chemical and ground stabilization technique using the same

Abstract: PURPOSE: To improve the compressive strength by mixing a solution A contg. a hydraulic cement and a liquid B contg. an alumina cement and II type anhydrous gypsum in a predetermined mixing ratio, the liquids A and B each having a particular Blaine value, and grouping the mixture into the ground. CONSTITUTION: Suitable amts. of a water reducing agent, dispersant and the like are incorporated into about 40 to 300kg of a hydraulic cement such as a portland cement having a Blaine value of 5000 to 18000cm /g. Water is added thereto, and the mixture is kneaded to prepare an about 200 liters of a liquid A. Separately, water is added to about 15 to 150kg in total of a mixture of 1 pt.wt. alumina cement having a Blaine value of not less than 4000cm /g with 0.5 to 1.5 pts.wt. II type anhydrous gypsum having a Blaine value of not less than 5000cm /g, and the mixture is kneaded to prepare about 200 liters of a liquid B. A soil stabilization chemical of 100 pts.wt. hydraulic cement with 13 to 50 pts.wt. total of the alumina cement and the II type anhydrous gypsum being incorporated thereinto is grouted into the ground, followed by hardening for 5 to 30min to stabilize the ground.

Construction of lime or lime plus cement stabilised cohesive soils

Abstract: Construction methods and equipment adopted for lime treated soils are discussed, including measures necessary for the health and safety of personnel. Specification requirements are given for the soil stabilisation of untreated and treated soils. Details are given of the construction procedure, including formation to level and preparation of formation. A summary is given of the use of a number of purpose built rotovators designed to undertake soil treatment with lime, cement or other suitable binders. Water addition and light compaction are covered. Details are given of the maturing period, re-mixing and final moisture adjustment, final compaction, curing and protection. The risks associated with the use of quicklime are identified and advice given on protective equipment, precautions to guard against dust and first aid procedures. For the covering abstract see IRRD 887532.

Use of Hydrated Fly Ash as a Flexible Base Material

Abstract: Common uses for fly ash, such as soil stabilization and cement replacement, account for less than 20 percent of the fly ash produced in the United States. Therefore, finding other bulk uses for fly ash is important. One such potential application is hydrated fly ash as a base material. The Texas Department of Transportation (TxDOT) is working to produce specifications to incorporate hydrated fly ash as a flexible base material. High-calcium Class C fly ash has a self-hydrating capability in the presence of moisture. Class C fly ash produced from coal power plants using lignite and subbituminous coal is mixed with water, dumped in large pits, and left to hydrate for a period of 3 to 6 weeks. The result is a hard, homogeneous mass of hydrated fly ash that can be mined to produce a construction aggregate much like limestone. TxDOT has used this material on several test projects. It has a desirable compressive strength, but in some instances its adhesion to seal coats has been a problem. Laboratory studies in...

Properties of stabilised soils in recycled pavements

Abstract: The paper describes research being undertaken at the University of South Australia into the properties and performance of recycled pavement materials stabilised by the addition of a cementitious binder. A total of nineteen soils and twenty binders have been chosen by the Australian State Road Authorities with the combinations of soils and binders for the study being selected on the basis of their availability in various geographic locations. The binders comprise Portland cement with or without the addition of fly ash or granulated blast furnace slag and hydrated lime with either the addition of granulated blast furnace slag or fly ash. A wide range of stabilised materials has been studied. The properties of three stabilised materials, representative of the results obtained in the program, reported in the paper include modulus of elasticity, erodibility and soil classification of the parent material; the elastic properties being essential for the mechanistic design of pavements. The results of field studies to examine the degree of compaction through the depth of the stabilised layer and pavement performance as measured by deflection have been included in the paper. (a) For the covering entry of this conference, please see IRRD abstract no. 878228.

Soil Stabilization by Ambient Pore Pressure and Geomembrane Containment

Abstract: Substantial atmospheric and pore water pressures exist in soil deposits. These pressures may be used to exert additional confining stresses with the aid of relatively impervious barriers. Any reduction in pore pressure within the impervious boundaries of an isolated soil domain will result in an equal increase in confinement. Confinement that directly increases effective stress will in turn increase shear stiffness and strength of the soil. In situ applications are becoming increasingly feasible in view of the recent advances in construction and installation of geomembrane systems. In this study, the concept of increasing confinement by action of ambient pore pressure is discussed. The effectiveness of this approach when applied to dry and saturated cohesionless soil is evaluated using a series of centrifuge model tests. In these experiments, a major increase of soil resistance to deformations is observed. In the saturated soil models, the potential for liquefaction induced deformations is eliminated. Pra...

Chapter 6 Methods of construction

Abstract: Publisher Summary This chapter discusses the methods of construction. Construction on soft organic soil gives rise to special problems. Most obvious are the large deformations that may occur during and after the construction period, both vertically and horizontally. The settlements often appear very quickly but may also continue for very long time periods due to creep. The low strength often causes stability problems, and consequently the load sometimes has to be placed in stages or, alternatively, the soil must be improved through prior treatment. It is important to realize that organic soil is not a single type of soil but a number of soils with very different behavior. In one case, it may be appropriate to choose preloading, as for fibrous peat, while in another case this solution turns out to be impracticable due to low permeability, as with organic clay. In the latter case, soil stabilization may be the most economical solution. Even for a special soil type, such as peat, the properties may vary immensely, as between fibrous and decomposed states.

Stirring device for deep mixing soil stabilization

Abstract: PROBLEM TO BE SOLVED: To improve the execution property by arranging a high pressure water injection port which is directed downward and obliquely on a stirring shaft provided with a soil improving material discharge port at a lower end thereof and a digging blade. SOLUTION: A stirring device for deep mixing soil stabilization consists of a stirring shaft 3 provided with a soil improving material discharge hole 1 and a digging blade 2 at a lower end thereof, a stirring blade 4 consisting of a plurality of steps, and a high pressure water injection port 5. Next, at the time of construction, the shaft 3 is rotated to stir the soil, and a soil improving material is jetted through the discharge hole 1 to penetrate to the required depth while high pressure water is being jetted obliquely and downward from the injection port 5 between upper and lower stirring blades 4. Then, the injection of high pressure water is stopped, and the shaft 3 is raised while stirring the soil. Stirring effect is increased due to the injection of high pressure water, and the soil is turned into mud earth to increase the mixture effect with the soil improving material. Furthermore, cohesion of viscous earth is reduced to eliminate its adhesion on the shaft 3 and the blade 4 and their simultaneous turn. Consequently, it is possible to achieve high quality soil improvement from sandy earth to viscous earth and prevent a slide, a flow to a side, and liquefaction of the soil.

The Use of Stabilised Fly Ash in Pavements

Abstract: The disposal of industrial by-products is a problem that is increasing in Australia. Over 7 million tonnes of fly ash are generated every year. Small amounts of the material are utilised and the rest is stockpiled. The increasing number of stockpiles is becoming a financial burden to electric generating authorities. The aim of this paper is to discuss the application of fly ash in pavements, particularly as a full depth base material. Although fly ash has been used in Australian roads for many years, it has had virtually no application as a full depth base material, which has the potential for the utilisation of large volume of this material. Laboratory prepared fly ash samples were stabilised with cement and lime before being subjected to mechanical and strength tests. Also, the samples were investigated by x-ray diffractometry and x-ray fluorescence spectrometry in order to identify the chemical composition. According to the results obtained, stabilised fly ash may be used successfully in lightly trafficked roads.