Showing papers on "Soil stabilization published in 1987"

An evaluation of lime and cement stabilization

Abstract: Stabilization of clay materials is of interest to any engineer who must deal with this type of soil. Stabilization techniques can be mechanical or chemical, or both, but the addition of a stabilizing agent is generally the favored approach. Lime in one form or another has been the most widely used stabilization agent for clay. However, portland cement to stabilize clay has been promoted and used in some applications. It was the purpose of this research to define the effectiveness of hydrated lime and portland cement on three Texas clays. Variables evaluated included two levels of treatment, two levels of pulverization, two compaction efforts, two moisture conditions, and a range of curing times. On the basis of the results and conditions of this test program, lime treatment of expansive, high-plasticity soils was more favorable for compressive strength attainment than was cement treatment of these soils. In general, lime treatment produced higher dry-conditioned strengths, but the major advantage was in the wet-conditioned strengths. Lime treatment provided significantly better resistance to moisture damage when these soils were compacted by the modified compactive effort. Cement treatment of low-plasticity sandy clay produced significantly higher compressive strengths than did lime treatment of this soil.

Fly Ash as a Potential Waste Liner

Abstract: Earthen liners have been widely used to contain toxic and hazardous materials in ponds and landfills. There is close scrutiny over the durability of liners in contact with various wastes and a need for cost-effective alternatives with superior qualities. Fly ash and fly-ash stabilized soils present a significant potential as a resistant and cost-effective waste liner material. A series of tests was performed on fly ash and fly ash/sand mixtures to evaluate both the physical characteristics pertinent to containment of waste liquids and the chemical interactions with such liquids. Permeability, volume change, and mechanical properties were studied as a function of environmental exposure factors such as freeze/thaw cycles and wet/dry cycles. The influence of construction factors such as water content, compactive effort, and time between mixing water and compacting on density and permeability was considered. Permeability tests using inorganic salt solutions of various composition and pH also were made. A summary of the findings of this investigation is presented. The laboratory experiments indicate that pozzolanic fly ash has many properties that are attractive in a liner construction material.

Soil Improvement : A Ten Year Update

Abstract: Since the publication of Soil Improvement—History, Capabilities and Outlook after the Annual ASCE convention in Philadelphia in 1976, a dramatic growth in certain soil improvement techniques has occurred. The proceedings of the Symposium sponsored by the Placement and Improvement of Soils Committee, Geotechnical Engineering Division, ASCE at the 1987 spring convention is a ten year update that reports on major developments in the following areas of soil improvement: in situ reinforcement, densification, reinforcement of constructed earth, and chemical admixtures. The book includes four committee reports which are complimented by ten case history papers in the area of soil improvement that have occurred in the past decade. The case histories include the ground modification and construction test program at Steel Creek Dam to prevent liquefaction; the wick drain experiences of Caltran; the soil densification program at the Trident site in Georgia; the West Pinopolis compaction grout test program; slope effects when densifying sands; case histories of root piles, soil nailing, welded wire wall performance, and a reinforced polymer sea wall.

Durability and long-term performance of Tensar* polymer grids for soil reinforcement

Abstract: Tensar polymer grids (geogrids) are oriented integral polyolefin structures, specifically developed to reinforce and stabilize soil in civil engineering works for which there is a design life of 100 years or more for buried materials. It is confirmed, from the results of work by others, that their composition and structure give these geogrids good resistance to biological attack and detrimental aging in such applications. Environmental stress cracking and outdoor weathering are discussed in detail, and results of specially commissioned tests in both areas are presented. Methods used to establish a 120-year load-bearing capacity are explained. It is seen that currently the performance of a structure reinforced by Tensar geogrids is determined by soil strain, not reinforcement strength. Any damage that may be caused to the geogrids must be taken into account at the design stage. Large-scale tests carried out to determine the magnitude of such damage are described, and the results presented.MST/591

Soil mechanics. 4th edition

Abstract: This book, which is intended to serve the needs of the undergraduate civil engineering student, studies the following aspects of soil mechanics: basic characteristics of soils; seepage; effective stress; shear strength; stresses and displacements; lateral earth pressure, including the design of earth-retaining structures; consolidation theory; bearing capacity; stability of slopes; ground investigation.

Stabilization of Very Soft Soils Using Geosynthetics.

Abstract: : Introduction of high-strength geosynthetic materials has allowed for construction on heretofore impossible sites. Saturated, fine-grained soils with in-situ unconsolidates-undrained strengths as low as 1.0 kPa (20.8 lb/sq ft) have been successfully used for embankment foundations using geotextiles or geogrids for direct ground support. When rapid consolidation of the subsoil is desirable, the procedure sometimes calls for insertion of strip (wick) drains and, for lateral flow, drainage geocomposites as well. This paper reviews and summarized a number of soft-soil stabilization projects. Drawing from these experiences, a five-part design method is presented to select and size the various goesynthetic material properties involved. Keywords: Dikes; Dredged material disposal areas or containment; Soft foundations; Slope stability analysis; Geosynthetics; Geotextile.

Soil stabilization for roadways and airfields

Abstract: : This report provides fundamental concepts of chemical soil stabilization so that a user might evaluate soil stabilization as a pavement construction alternative, determine the type and quantity of stabilizer required and direct the construction of stabilized pavement layers. The methods covered include stabilization of roadway and airfield systems with time, cement, asphalt, fly ash and combination stabilizers.

Nailed-soil retaining structures: design and practice

Abstract: Soil nailing is an in situ soil reinforcement technique that has been used during the last two decades, mainly in France and Germany, to retain excavations or stabilize slopes. The fundamental concept of soil nailing is the reinforcement of the ground by passive inclusions, closely spaced, to increase the overall shear strength of the in situ soil, to restrain its displacements, and to limit its decompression during and after excavation. The technology, construction process, design methods, and fundamental aspects of behavior and soil-nail interaction in nailed-soil retaining structures are discussed.

Resilient Modulus of Freeze-Thaw Affected Granular Soils for Pavement Design and Evaluation. Part 3. Laboratory Tests on Soils from Albany County Airport,

Abstract: : This is the third in a series of four reports on the laboratory and field testing of a number of road and airfield subgrades, covering the laboratory repeated-load triaxial testing of five soils in the frozen and thawed states and analysis of the resulting resilient modulus measurements. The laboratory testing procedures allow simulation of the gradual increase in stiffness found in frost-susceptible soils after thawing. The resilient modulus is expressed in a nonlinear model in terms of the applied stresses, the soil moisture tension level (for unfrozen soil), the unfrozen water content (for frozen soil) and the dry density. The resilient modulus is about 10 GPa for the frozen material at temperatures in the range of -5 to -8 C. The decrease in modulus with increasing temperatures was well-modeled in terms of the unfrozen water content. Upon thaw, the modulus dropped to about 100 MPa and generally increased with increasing confining stress and decreased with increasing principal stress ratio. The modulus also increased with the soil moisture tension level. The resilient Poisson's ratio did not appear to be a systematic function of any of the test variables. Keywords: Soil dynamics; Soil stabilization.

Carbonation of stabilised soil-cement and soil-lime mixtures --developing countries: highway construction. proc. of seminar h held at the ptrc transport & planning summer annual meeting, bath univ. england 7-11 september 1987, volume p295

Abstract: Carbonation can affect the strength of cement and lime-stabilised soils. Correct curing is therefore important especially in hot, dry climates. Soil stabilisation with cement or lime is used in many countries in the construction of road bases and sub-bases and for the treatment of subgrade soils. Recent studies have shown that the performance of stabilised layers can be affected by carbonation which inhibits the formation of cementitious products in soil-cement and soil-lime reactions. This paper examines the evidence for carbonation in road trials constructed in a hot, arid area in botswana and describes the laboratory study that followed using a clayey sand (a poor quality calcrete) from botswana to investigate the effect of different curing conditions on soil-cement and soil-lime mixtures. Humidity, temperature and carbon dioxide in the environment were varied and the affect on strength and properties of the stabilised soils were assessed by the unconfined compressive strength and plasticity tests. Different curing periods were examined and the extent of carbonation was identified by the use of phenolphthalein indicator. The results showed that carbonation to varying degrees and loss of strength occurred in all the strength-age relations except those that were cured under sealed conditions. Samples that were first allowed to harden also subsequently lost strength when exposed to carbon dioxide. It was also shown that changes in plasticity which occur in soil stabilisation and are an essential requirement in specifications for modified soils could also be reversed by carbonation. There remains a need to obtain more field evidence of carbonation and its relation to pavement performance, curing conditions and climatic environment. In addition a better understanding of the mechanism of carbonation is required especially of those reactions which involve cemented products.(a) for the covering abstract of the seminar see IRRD 816292.

Leachability of lignite fly ash enhanced road base

Abstract: Enormous amounts of coal fly ash produced by the utilities industry create a significant disposal problem The abundance of fly ash along with its self‐hardening properties led the Louisiana Department of Transportation and Development (LA DOTD) to use fly ash as a soil stabilizer for road bases However, the LA DOTD is primarily concerned with the strength of the material and has not studied its leaching characteristics During this study, a total of three samples, a 30 percent lignite fly ash/soil mixture, lignite fly ash, and soil, were leached following the EPA multiple extraction procedure and analyzed by Inductively Coupled Argon Plasma Spectrometry (ICAP) Results indicate that little change in leachate quality of lignite fly ash was caused by the soil stabilization process The insignificant change is attributed to the low cation exchange capacity of the soil ICAP analysis revealed that heavy metal concentrations were within RCRA and Public Drinking Water standards road bases [3,10] Ho

Roadway performance in an expansive clay

Abstract: The performance of three pavement designs with expansive clay subgrade is presented. The pavements have been subjected to extensive warping attributed to differential swelling of the underlying soil. The purpose of this paper is to evaluate the effectiveness of the three designs in reducing warping, and to provide suggested alternative designs. The study focuses on pavements west of Dallas, Texas, situated over weathered shale of the Eagle Ford geologic formation. The weathered shale is highly expansive with heaving in excess of 12 in. being recorded. Postconstruction heave is attributed to increase in the soil moisture regime over time. Pavement warp occurs primarily in deep cut areas where the finished grade lies near or below the original zone at which soil moisture was stable and was not influenced by seasonal fluctuations. Data indicate that the overall movement of the pavements studied was upward. Differential vertical movements caused warping. The differential movement is attributed to the influence of: (a) underground utilities; (b) micro and macro soil structure features; (c) drainage; (d) patterns of water migration; and (e) stress release. The study evaluates the performance of three specific pavements. Subgrade treatments used to minimize potential movements included removal and replacement with lime stabilized soils and inert fills, and maintaining positive drainage. Alternative subgrade treatment by preswelling is discussed. Modification of pavement shoulders and base to account for shrinkage and loss of bearing support is a necessary component of preswelling design. Preswelling and suggested base and shoulder modifications are compared to current design techniques used in the area on an economical basis.

Grouting in Difficult Soil and Weather Conditions

Abstract: Several methods of soil grouting and conventional underpinning are used to stabilize subsoils and repair the foundations of three apartment buildings. Innovative cold weather compaction grouting techniques were used in difficult soil conditions to densify poorly compacted man-placed fill and soft organic silts beneath building foundations. Penetration grouting using a Portland cement slurry and Pozzolan (flyash) is performed to reduce permeability of the upper subsoils and to fill ineffective and detrimental building perimeter drains. A gravel intrusion jacking method is used to further densify upper soils in conjunction with conventional underpinning methods. The project is unique because: (1) Techniques were used that allowed the contractor to drill and densify loose fills and soft natural soils containing cobbles and boulders; (2) the contractor was able to perform grouting and underpinning under extremely adverse weather conditions by using special equipment; and (3) occupants were able to remain in buildings during remedial construction.