Experimental and Theoretical Study of Pavements in the Base and Sub-Base Course in Single-Layer and Multi-Layer

Today, the road transport industry is one of the most important industries in which public and private vehicles use it. Usually, most of the development budgets belong to the roads, or in every construction work of the roads is of great importance. Huge traffic load Extreme changes in temperature and accidents create cracks and defects in road pavement structures and reduce safety and increase fuel consumption. Therefore, the Experimental and theoretical study of pavements in the base and sub-base course in single-layer and multi-layer is necessary. How much they make these ways and how much they cost is much to be discussed. In this study, some studies and road pavement stages are presented, and the theoretical methods of optimizing the effective parameters in the base and sub-base course are presented. Keyword Asphalt ConcreteTransportation Industry, Optimization, Pavement


Type of pavement bed Idioms
Dirt cut A) What kind of soil in a thickness of 30 cm under the floor trench with AASHTO soils (A1 -A7) and or the type of soil designated in the private technical specifications for the project in question, the modification or replacement of additives or additives such as lime should be strengthened.
B) The modified materials described in paragraph (A) should be drilled in a double layer and each layer at a thickness of 15 cm to achieve a specified percentage density and provide the desired level.

Stone cut
The floor is cut to a maximum of 15 cm below the pavement amount and then replaced with good quality and acceptable and give the percentage of density to be characterized. In stone trenches, the type of marl or gypsum should be replaced at least 30 cm from the cutting floor with two layers of high-quality materials and each individual layer to be condensed to a certain degree.
Embankment 30 cm of pavement in the embankment should be of suitable soil type in two separate layers each with a thickness of 15 cm and to be compressed to obtain a relative density of the characteristic. If the above thickness is not suitable for proper soils and the required specifications are not provided, then the operation must be modified outside the specification.

Existing road surface
Materials are up to 30 cm deep. If this bed is on par with the asphalt pavement, then how to prepare the pavement should be mentioned in private technical specifications.

II. RELATIONSHIPS GOVERNING PAVEMENT ANALYSIS
The study of stress -strain behaviour under various loads is one of the important issues in the design and analysis of pavement layers. In strain -stress behaviour analysis, various parameters such as the Yang modulus (E) obtained from the single-axis test are used. One of the important issues for engineers is the failure of the pavement layers, and, on the other hand, estimating the amount of the sum of the stresses is important. In most cases, the use of the concepts and relationships of the theory of elasticity can partly reflect the behaviour of the soil [5]. In this case, real nonlinear curves should be modelled linearly, so studies with the Young modulus and the interval coefficients also take place.
Important research work has been done in this area since the Second World War in the field of road and rail engineering. Advanced mathematical models based on basic analysis and application of the finite element method in the framework of road construction design. There is also a lot of research in laboratories to determine the mechanics of fatigue structures in materials used on days. The results of the research are standardized in order to be used by road engineers and contractors, as well as for the maintenance and management of roads and roads. Pavement design methods are expressed in three basic structures: rigid structure flexibility structure and semi-rigid structure. For rigid and flexible pavements on a substructure basis and under the rigid base, the twolayer structure and three-layer structures are used respectively. Flexible layers are calculated with the assumption of elastic bedding.

A. ULIDTZ method
Many attempts were made to correct coefficients by a person named ULIDTZ in 1987 [6], which introduced a relationship that is a function of the thickness of the layers and the Young modulus [7-8]. In the ULIDTZ's method, an issue is analysed by a computer method, and then the same problem is solved by the equivalent thickness method and using the Boussinesq equations. By comparing these answers and the slight difference between them, a correction coefficient (f) should be multiplied by the equivalent thickness. This means, for example, that if we have a two-layer pavement and want to transform it into a modular-layer pavement equal to the substrate modulus, we need to change the thickness of the first layer and convert it to the equivalent thickness (he). Now, if this equivalent thickness is multiplied by the correction coefficient (f), a new thickness is obtained that, if this new pavement is analysed by the Boussinesq method, there are answers that are very close to the actual answers or the answers obtained from the computer programs. We define the correction coefficient (f) for the equivalent thickness value as an equation 1. The amount of this correction factor (f), depends on the thickness of the layers and the ratio of the modulus and the Poisson coefficient as well as the number of layers.
The correction coefficient (f) is a coefficient multiplied by the equivalent thickness, but it can be multiplied by the coefficient directly in the result obtained from the option relations.

B. Lotfi method
In 1984, Mr. Lotfi et al. [9]presented an empirical relationship that predicts the amount of Mr using finegrained soils. This statistical survey of Mr uses laboratory tests obtained by Barkard in 1982 at the University of Maryland. A total of 13 compounds of different soils were tested in terms of concentration and humidity in different locations. Which results in gaining 64 overall Mr of d for all different materials Lotfi's model is as follows: Where Mr is Resilient Modulus of Soil Substrates and O is Tension ofLotfi's. For integrating of linear response of Soil substrate Mr, It needs to be solved and at that angle is the angle that depends on the work of the applied wheel on the pavement section.
Considering the common layered pavement in computer solving of program of LCCP-flex-MDOT And taking into account such factors as simplifying resolution time and so on, Matthew and Witczak 1995 had to use an alternative method to simplify it. In this way, user flexibility plays an important role in increasing the design and serviceability scheduling and all kinds of layered materials.
Thus, dams have been proposed by LCCP-flex for pavement analysis. Which later became important due to the low cost of the pavement? The converted cross-section for the pavement system is widely known as a research method for presenting different methods for calculating strain and deformation stress. Boussinesq point-load equations can be easily obtained for use in the substrate of adaptive solutions for the surface charge of any form by numerical integration.

C. Westergaard model
In the Westergaard model [10-11-12]which was introduced in 1984 and used for double-layer pavements with substrate, the flexural stress is fixed below the layer and is calculated along the line to load the load at the edge of the layer as follows:

III. THE PROPOSED FRAMEWORK
In general, asphalt pavement can be designed in two single-layer, granite-based modes. Asphalt concrete is a single layer of pavement, which is used in sensitive parts of asphalt concrete. This type of pavement is more in line with the construction process and is less than basic operation. Single-layer asphalt concrete works in all traffic-intensive ways. Ground-based pavement uses more than locally available materials and they are used in places where traffic is less. The aggregate base is used in the upper part of the microscope to be compressed.

A. Single layer asphalt concrete
The main text of this paper is about designing the thickness of single-layer asphalt concrete for pavement that is used as a typical pavement. The following is about the comparison of ordinary asphalt and asphalt. The studies are under the supervision of the Asphalt Institute and other Asphalt Institutes to investigate and compare single-layer asphalt with other asphaltic species. The available studies are both for the laboratory and for the theory. The Asphalt Institute recommends the use of single-layer asphalt concrete. As explained in the previous section, the underlying soil cannot tolerate tensile stresses, so in this case it exhibits weakness in relation to single layer asphalt concrete. In the following, the problem was that the foundation of the earth, while keeping the moisture inside it, would cause damage to the pavement and its substructure. This will reduce the strength of the materials in the road construction, which will further reduce the load bearing capacity of the pavement. Characteristic factors in the design of asphalt concrete tactics are: 1) The traffic conditions in the design basis and other materials in the place 2) Environmental conditions that change the behaviour and service. The different conditions for designing each of these will be described further. One of the advantages of single-layer asphalt concrete, as already mentioned, is the need for sub surface drainage. Drainage will only be required when underground water levels are high. Or when the water is placed at the bottom of the horizontal arc, the scouring below the surface of the pavement will cause water to accumulate. In these situations, the design of drainage sub-surfaces, which is detailed in the design of drainage drafts, has to be done.

B. Stage construction
There are several ways to do these days under the way, but the steps should be considered. One way is to find ways to build new settlements. In this case, the asphalt base can be built beforehand so that traffic can be done in the area. The asphalt pavement can be constructed in the next step. In front of those roads, which are greatly increased just after the construction of traffic routes. The greatest advantage of the stage construction is that any construction is done until a stage that has not been poured onto the asphalt can be corrected. This will guarantee a smooth pavement for a long time.
The aggregate used as a base requires an inch of the asphalt layer. That is, the value of the substitution ratio is two. of an inch of unpolluted aggregate that is used as a basis requires an inch of layer of asphaltic. It means that the value of the substitution ratio is [13].
All materials that are to be used in road pavement should be fully tested and the results of the tests show that this issue is both economically and in terms of proper resistance. These experiments yield many results, including the right amount of density and other information.

Suffic of the soi guide fro avoid pot Finally
The nu finite elem research however, In the of the fo informati mechanic (Fig. 3)