Showing papers on "Soil stabilization published in 1978"

Design and construction of airport pavements on expansive soils

Abstract: This investigation reviewed the current engineering literature and synthesized from it a design procedure for stabilizing expansive soils beneath airport pavements. To do this, the study was divided into specific areas: Methods of identifying and classifying the types of soil that are considered expansive and cause early pavement distress; Laboratory and field test methods to determine the level of expansion and shrinkage, i.e., prediction of heave; and the design of stabilized soil layers including (a) selection of the type and amount of stabilizing agent (such as lime, cement, or asphalt), (b) test methods to determine the physical properties of stabilized soil, (c) test methods to determine the durability of stabilized soil, and (d) field construction criteria and procedures. The conclusions and recommendations are based on the current literature, without laboratory verification. Soil-volume changes caused by factors such as frost heave and salt heave were not studied. It was found that while procedures for soil stabilization have improved significantly, the test methods that were developed do not provide a marked improvement over those currently used.

Soil Improvement : History, Capabilities, and Outlook

Abstract: This report is intended to help engineers meet the need for practical, efficient, economical, and environmentally acceptable means for improving unsuitable soils and sites, for expanded utilization of soil as a construction material, and for management and use of waste materials. It covers a wide range of topics including soil moisture in engineering works, current practices in the treatment of soft foundations, admixture stabilization, massive compaction of granular soil, tension and compression elements of reinforcement, collapsible soils and their stabilization, and soil placement and improvement.

Studies on engineering characteristics of cement-base stabilized soil

Abstract: This report clarifies the engineering characteristics of cement-base stabilized soil which is the basis of the deep chemical mixing method, through various tests using laboratory soil and in situ soil. For physical characteristics of stabilized soils, such factors are described as water contents, unit weights, and coefficients of permeability, while for its mechanical characteristics, description is given to unconfined compression, tension, shear and consolidation characteristics. The characteristics of stabilized soils are clarified centering around the influences exercised by hardener addition rates and the initial water contents of samples upon the individual characteristics. Also discussed are relations of coefficients of permeability before and after stabilization, factors influencing unconfined compressive strength of stabilized soil, correlation between simple tension test results and splitting test results of stabilized soil, and other factors.

Unsheathed Excavation in Cohesive Soils

Abstract: This technical note is intended for studying the stability of soils between unsheathed piles. Because sands require sheathing regardless of the type of support, cohesionless soils are excluded from this study.

Evaluation of experimental flexible pavements

Abstract: A program of construction and performance evaluation of seven Virginia flexible pavements containing at least some experimental features is reported. The objective of the program is to evaluate the performance of the pavements incorporating new or timely design concepts and to assess the flexibility of these concepts for further use. Among the major findings of the study to this point are the following. 1. Pavements having equivalent design thickness indices are not necessarily equivalent in construction cost or in early structural strength. 2. Very early deflection tests do not give good indications of the ultimate strength characteristics of pavements having cement stabilized layers. 3. Full-depth asphaltic concrete pavements can give excellent performance in very poor soil areas, especially when the design is modified through the provision of a cement stabilized subgrade. 4. An unstabilized sandwich layer placed between a cement stabilized layer and asphaltic concrete layers is effective in significantly delaying the reflection of transverse cracking from the cement stabilized layer through the asphaltic concrete layers. There is some evidence that reflective cracks may develop after many years under heavy truck traffic. 5. Such a sandwich layer is weaker than either of the two layers it contacts and can cause a net reduction in pavement strength as compared with the situation where the weaker layer is on the bottom. 6. Transverse shrinkage cracks reflect from a cement treated stone subbase through 3 inches (75 mm) of bituminous concrete in as little as 18 months and through 7 inches (175 mm) of bituminous concrete in less than 5 years. 7. Cement treatment of stone subbases can be omitted in passing lanes with no detriment to performance. (This may not be true with traffic volumes near capacity because of the change in distribution of truck usage as that point is approached.) The two following recommendations for consideration by administrators of the Highway and Transportation Department seem appropriate at this time. 1. The Department is encouraged to consider the full depth asphalt concept as a desirable alternative in flexible pavement design. In poor soil areas the designs should be modified to provide cement (or lime) stabilization of the native subgrade soil. Although full depth design may be considerably more expensive than many alternatives, there is strong evidence reported herein that the full-depth pavements can provide performance somewhat better than most of these alternatives. 2. In cases where it is deemed appropriate to stabilize aggregate base materials on divided highways with four or more lanes where truck traffic is normally channeled into the outer lanes, it is structurally feasible to omit such stabilization from the inner or passing lanes. While in many cases there may be no economic advantage in such a practice because of construction difficulties, the concept is recommended for cases where it may be practically feasible.

Reinforced earth walls on stone columns in soil

Abstract: THIS PAPER WAS PRESENTED AT THE INTERNATIONAL SYMPOSIUM ON SOFT CLAY, BANGKOK, THAILAND, 5-6 JULY 1977 THEME: METHODS OF IMPROVING THE GEOTECHNICAL PROPERTIES OF SOFT CLAY IN ORDER TO BUILD A 8,50 M-HIGH REINFORCED EARTH WALL ON 10 TO 12 M OF SOFT, COMPRESSIBLE SOIL IN A VERY SHORT TIME, STONE COLUMNS WERE CONSTRUCTED IN THE GROUND THIS CONSISTED IN INCORPORATING WITH THE SOIL A COLUMN OF GRANULAR MATERIAL WHICH ENABLES THE STABILITY TO BE IMPROVED AND THE SETTLEMENT REDUCED THIS PAPER PRESENTS THE OBSERVATIONS MADE ON SITE ON THE BEHAVIOUR OF THE COLUMNS AND SHOWS THAT THE SIMILARITY BETWEEN THE TRIAXIAL TEST AND THE STONE COLUMN IS ADEQUATE TO ENABLE DESIGN PROBLEMS TO BE TREATED WITH THIS APPROACH HOWEVER, THE CROSS-SECTION OF THE COLUMN AND THE HORIZONTAL STRESS MUST BE CHOSEN A PRIORI AS REGARDS THE LATTER IT IS PROPOSED TO TAKE INTO ACCOUNT THE CREEP PRESSURE MEASURED WITH THE PRESSIOMETER CONTROL TESTS HAVE ALSO SHOWN THAT THE COLUMNS MAY FAIL WITHOUT CAUSING THE FAILURE OF THE WHOLE STRUCTURE, ALTHOUGH LEADING TO IMPORTANT SETTLEMENTS WHICH ARE HOWEVER SMALLER THAN THOSE THAT WOULD HAVE HAPPENED WITHOUT TREATMENT AND WHICH CAN BE QUICKLY STABILIZED FOR THE COVERING ABSTRACT SEE IRRD ABSTRACT NO 107555; SEE ALSO IRRD ABSTRACT NO 243851

Increasing the effectiveness of soil compaction at below-freezing temperatures

Abstract: : This report presents data from an experimental program undertaken to determine the effect of low temperatures on the compaction characteristics of a silty sand The effects of compactive effort and chemical additives were also investigated to determine possible methods of improving the densities of soils placed and compacted at low temperatures A single soil type was used throughout the test program and test results were obtained using Standard and Modified AASHO compactive efforts on an untreated soil prepared and tested at temperatures of 20C and -7C Additional test series, using the same compactive efforts and temperatures, were performed on the soil after it had been treated with an additive The amounts of additive used, based on the dry weight of soil, were 3, 2, 1, 05, and 025% of calcium chloride and 05% of sodium chloride From the results of the experimental program, several important conclusions concerning the effect of low temperature compaction were drawn: (a) For similar test conditions, the dry unit weight of a frozen compacted soil is less than for an unfrozen compacted soil (b) The dry unit weight of a frozen soil is inversely proportional to the amount of ice in the soil pore space (c) Chemical additives can be effectively used to offset the adverse effect of low temperature on the compaction characteristics of a soil (d) The effect of chemical addivites on the compaction characteristics of a soil compacted at temperatures below 0C can be predicted using phase equilibrium concepts from physical chemistry