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Base course

About: Base course is a research topic. Over the lifetime, 1511 publications have been published within this topic receiving 12486 citations.


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01 Sep 1972
TL;DR: In this article, the authors used the repeated load triaxial test to evaluate the relative performance of unstabilized base course materials with respect to rutting and then used in the evaluation of a number of materials.
Abstract: A method is presented for evaluating the relative performance of unstabilized base course materials with respect to rutting and is then used in the evaluation of a number of materials. A general method is also proposed for calcualting rut depth occurring in flexible pavements. The proposed methods make use of the plastic axial strains obtained from the repeated load triaxial test. Cylindrical specimens 6 in. in diameter and 12 in. in height of crushed stone and soil-aggregate mixtures were placed in a conventional triaxial cell and subjected to 100,000 load repetitions using a constant confining pressure and a triangular stress pulse. Stress-strain curves giving the relationship between deviator stress, confining pressure and plastic axial strain were constructed for each material studied using the repeated load test results. The concept of a rut index was proposed which can be calculated making use of the plastic stress-strain relationship, and is approximately proportional to the rut depth that will occur in the base after a desired number of load repetitions. The rut index appears to offer a practical laboratory method for evaluating the relative performance of base materials used in pavements having similar structural configurations. An evaluation of the test results using the rut index approach indicates that under good conditions of drainage and proper maintenance of the pavement surface, carefully selected blends of 20 percent soil and 80 percent stone should perform satisfactorily. Soil aggregate blends having properties similar to the materials tested should probably not be used at all under poor drainage conditions, and 40-60 blends should not be used even under good conditions of drainage. The results further indicate that only a sufficient amount of fines should be used in a crushed stone base to permit proper compaction if the amount of rutting in the base is to be minimized. Furthermore, even though the specified gradation and density may be the same, bases constructed from aggregates obtained from different sources may exhibit different rutting characteristics. A general engineering method for estimating the rut depth in a flexible pavement after a desired number of load repetitions was proposed which utilizes nonlinear layered theory, the plastic stress-strain response of the component materials, and a hyperbolic, plastic stress-strain law. Field verification is now needed of both the proposed rut index and the general method for predicting rut depth. /Author/

292 citations

Journal ArticleDOI
TL;DR: In this article, a theoretically based design method for the thickness of the base course of unpaved roads is developed, which considers distribution of stress, strength of base course material, interlock between geosynthetic and base course materials, and geoSynthetic stiffness in addition to the conditions considered in earlier methods.
Abstract: A theoretically based design method for the thickness of the base course of unpaved roads is developed in this paper, which considers distribution of stress, strength of base course material, interlock between geosynthetic and base course material, and geosynthetic stiffness in addition to the conditions considered in earlier methods: traffic volume, wheel loads, tire pressure, subgrade strength, rut depth, and influence of the presence of a reinforcing geosynthetic (geotextile or geogrid) on the failure mode of the unpaved road or area. In this method, the required base course thickness for a reinforced unpaved road is calculated using a unique equation, whereas more than one equation was needed with earlier methods. This design method was developed for geogrid-reinforced unpaved roads. However, it can be used for geotextile-reinforced unpaved roads and for unreinforced roads with appropriate values of relevant parameters. The calibration of this design method using data from field wheel load tests and laboratory cyclic plate loading tests on unreinforced and reinforced base courses is presented in the companion paper by the authors.

267 citations

Journal ArticleDOI
TL;DR: In this paper, the results of a laboratory evaluation of a cement-stabilized RAP and RAP-virgin aggregate blends as base materials were presented, which indicated that the optimum moisture content, maximum dry density, and strength of RAP will generally increase with the addition of virgin aggregate and cement.
Abstract: Pavement rehabilitation and reconstruction generates large quantities of reclaimed asphalt pavement (RAP) aggregate, and recycling into new asphalt paving mixtures is the predominant application. RAP acceptance in road bases and subbases has been limited because of the lack of laboratory and field performance data. In the Sultanate of Oman, recycling of pavement materials is not practiced. A previous study conducted at Sultan Qaboos Univ. indicated that RAP-virgin aggregate mixtures could be utilized in the subbase layer rather than in the base course. This paper presents the results of a laboratory evaluation of cement-stabilized RAP and RAP-virgin aggregate blends as base materials. Compaction and unconfined compressive strength tests were conducted on the following RAP/virgin aggregate mixtures: 100/0, 90/10, 80/20, 70/30, and 0/100%. Samples were prepared using 0, 3, 5, and 7% Type I portland cement and were cured for 3, 7, and 28 days in plastic bags at room temperature. A pavement design analysis of using various cement stabilized RAP-virgin aggregate mixtures as base materials was also undertaken. Results indicate that the optimum moisture content, maximum dry density, and strength of RAP will generally increase with the addition of virgin aggregate and cement. Longer curing periods will yield higher strength results. The ability of RAP aggregate to function as a structural component of the pavement is more pronounced when it is stabilized with cement rather than when blending with only virgin aggregate. A 100% RAP aggregate should not be recommended for use as a base material unless stabilized with cement. Cement stabilized RAP-virgin aggregate mixtures seem to be a viable alternative to dense-graded aggregate used in road base construction.

247 citations

01 Jan 1944
TL;DR: In this paper, the theory of stress in a two-layered system was developed in accordance with the MATHEMATICAL Theory of ELASTICITY and is presented in order to reveal some of the fundamental relations existing between the PHYSICAL FACTORS, which control the LOAD-SETTLEMENT RELATIONS.
Abstract: THEORIES OF LAYERED SOIL DEPOSITS ARE REVIEWED. THE THEORY OF STRESSES ARE DISPLACEMENTS IN A TWO-LAYERED SYSTEM WAS DEVELOPED IN ACCORDANCE WITH THE METHODS OF THE MATHEMATICAL THEORY OF ELASTICITY AND IS PRESENTED IN ORDER TO REVEAL SOME OF THE FUNDAMENTAL RELATIONS EXISTING BETWEEN THE PHYSICAL FACTORS, WHICH CONTROL THE LOAD-SETTLEMENT RELATIONS, AND IN ORDER TO PROVIDE A PRACTICAL METHOD OF ANALYSIS FOR THE DESIGN OF AIRPORT RUNWAYS. THE THEORY REVEALS THE CONTROLLING INFLUENCE OF TWO IMPORTANT RATIOS ON THE LOAD-SETTLEMENT CHARACTERISTICS OF THE TWO-LAYER SYSTEM: (1) THE RATIO OF THE RADIUS OF THE BEARING AREA TO THE THICKNESS OF THE REINFORCING OR PAVEMENT LAYER, AND (2) THE RATIO OF THE MODULUS OF THE SUBGRADE TO THAT OF THE PAVEMENT, FOR PRACTICAL DESIGN PURPOSES, THE THEORETICAL RESULTS WERE EVALUATED NUMERICALLY AND EXPRESSED IN BASIC INFLUENCE CURVES, GIVING VALUES OF THE SETTLEMENT COEFFICIENT IN TERMS OF THESE BASIC RATIOS. THE SETTLEMENT COEFFICIENT IS APPLIED AS A SIMPLE MULTIPLYING OR CORRECTION FACTOR TO THE BOUSSINESQ EQUATION FOR SURFACE SETTLEMENT AT THE CENTER OF A CIRCULAR FLEXIBLE BEARING AREA. THE DESIGN FOR AIRPORT RUNWAYS INVOLVES THE SELECTION OF SUITABLE TYPES OF PAVEMENT CONSTRUCTION AND THE DETERMINATION BY THE INFLUENCE CURVES FOR THE TWO-LAYER SYSTEM OF THE THICKNESS REQUIRED TO GIVE ADEQUATE SUPPORT TO AIRPLANE WHEEL LOADS AND REASONABLE LENGTH OF SERVICE. FIELD LOAD TEST CHECKS OF QUALITY AND STRENGTH CAN BE MADE DURING CONSTRUCTION ON: (1) THE NATURAL SUBGRADE TO DETERMINE TENTATIVELY THE THICKNESS OF BASE COURSE AND PAVEMENT REQUIRED, (2) TOP OF THE BASE COURSE TO CHECK THE QUALITY AND STRENGTH AT THIS STAGE OF CONSTRUCTION, AND (3) TOP OF THE FINISHED PAVEMENT TO CHECK THE EFFECTIVE SUPPORTING CAPACITY OF THE WHOLE PAVEMENT CONSTRUCTION.

231 citations

Journal ArticleDOI
TL;DR: In this article, the results of a comprehensive laboratory study on the thermal conductivity of dense and broadly graded coarse base-course materials used in pavements were presented, and the results showed that the materials were selected based on their thermal properties.
Abstract: This paper presents the results of a comprehensive laboratory study on the thermal conductivity of dense and broadly graded coarse base-course materials used in pavements. Materials were selected f...

188 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202325
202269
202148
202063
201945
201871