APPLICATION OF THE GUIDE (GTR) TO PLATFORM FLOORS FROM THE TRARZA AND INCHIRI-MAURITANIA REGION MBLAL-LAHOUVICH AXIS AND AKJOUJT-TASIASIT AXIS

In the search for an adequate technical document in the field of road earthworks, and in view of the unavailability of national standards in Mauritania which may be the origin of these documents, this article essentially aims to propose methods of execution of the upper platform. Earthworks and subgrade. As a result, a study was made on platform soils in two regions in Mauritania, one is located in the south-west of the country (Trarza) and the other is in the west (Inchiri). Two roads were chosen, one 3.7km long (M'blal-Lahouvich), and the other 5km (Akjoujt-Tasaisit).

In the search for an adequate technical document in the field of road earthworks, and in view of the unavailability of national standards in Mauritania which may be the origin of these documents, this article essentially aims to propose methods of execution of the upper platform. Earthworks and subgrade. As a result, a study was made on platform soils in two regions in Mauritania, one is located in the south-west of the country (Trarza) and the other is in the west (Inchiri). Two roads were chosen, one 3.7km long (M'blal-Lahouvich), and the other 5km (Akjoujt-Tasaisit).

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The road network is of particular importance due to the size of the country. Road transport is the main mode of transport. The strategy pursued by the Government consists of ensuring the maintenance and rapid development of the network and the sector therefore benefits from significant investments. The network has 10,282 kilometers, including 2,100 of paved roads, 982 km of dirt roads and 7,200 km of tracks [2].
In view of the geographical characteristics of Mauritania, its vastness and the hostility of the environment, the development of transport represents a major challenge to be taken up in order to strengthen national compet itiveness through the promotion of trade and the reduction of production costs. [3], and to open up rural areas, it is in this sense that we have deemed it interesting to: Carry out a geotechnical study on the existing platform soils in Mauritania which will make it possible to know the zones in which the materials can be used in sub-layers or in backfill, which will reduce time and investment. It is also an opportunity to make a contribution to strengthen technical studies of this kind.
On the other hand, to establish selection criteria and implementation conditions for the backfill and subgrade that adapt to our environmental and water specifications.

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Indeed, in the absence of a technical reference, the dimensioning of pavements in Mauritania is usually based on specialized works capitalizing on the experiences lived in the countries of the tropical zones. Beyond the summary of the geotechnical conditions and the use of materials represented by these feedbacks, the fact remains that they only very partially take into account the specificities of the Mauritanian road context. The pavement structures to which they end do not always reflect the local conditions of execution work and even less an optimal use of locally available materials.
However, this document reflects studies carried out on platform soils in regions in Mauritania, but cannot give an answer to all the questions raised by road construction.
In addition, in any road construction project, it is essential to know the behavior of the soil during and after the construction of the road, hence the importance of earthworks.
We call earthwork, the different movements of the earth whose purpose is to dig excavations or to modify the configuration of the ground. This modification of the ground levels is carried out by the execution of cuttings and embankments [4].
On the other hand, the application of the road earthmoving guide to platform soils will be done by implementation processes and these to give our roads the geometric characteristics (longitudinal profile, cross profile, layout, etc.) which will allow it to play their role, but also with regard to the materials to be used in earthworks, to make the most appropriate choice according to the type of project, the geographic and environmental sites encountered.

Materials and Methods:-
This geotechnical study was carried out in two regions. Indeed, we have chosen two axes namely: M'Blal-Lahouvich (Laiwij) and Akjoujt-Tasiasit axis. M'Blal is a town located 169 km from Nouakchott, Mauritania and Akjoujt is a town located 260 km from Nouakchott, Mauritania [5][6]. Then, we carried out three manual surveys on each axis and we present below the strategy adopted throughout our samples: 1. A depth of 1m for each manual sounding; 2. 50 m separate the boring and the route of the road 3. 500m between two soundings relative to each other.
This operation made it possible to make a visual description of the soils on site and to take samples in order to be able to identify them from a physical and mechanical point of view in the laboratory. During the operation, we did not notice the presence of a tablecloth.

Axis M'Blal-Lahouvich (Laiwij)
The fig 1 represents the cross-sections of the soundings, N1, N2, N3; we notice the presence respectively of 60cm, 70cm, and 75cm of all coming shell TVC. The samples taken, consisting of loose soil, were analyzed according to the following laboratory test program: The natural water content, the Atterberg limits or the sand equivalent depending on the nature of the soil, the grain size by sieving, the blue value, the Proctor compaction test and the CBR punching test.

Mechanical Characterization Results Water Content
The sands taken from the M'balal-Lahouvich (laawij) axis contain a lower quantity of natural water than those from the Akjoujt-Tasiasit axis (Table 1), because the sandstone calo contains more fine than the shell sand. 664

Atterberg results
According to the GTR, the results obtained by the two axes (Fig 3, Table 2) showed that the soils are weakly clayey [3]. Fig 3:-Liquidity test curves.  [9] According to the GTR, the results obtained for the soils of the two axes (Table 3), we have a weakly loamy soil (soil not very plastic and sensitive to water) because their values of VBS are between 0.2 and 1.5 [3]. 665

Results of particle size distribution [10-11]
The Fig 4 and the Fig 5 respectively show all the curves obtained during the particle size tests of the sands of the M'balal-Lahouvich axis and of calcogreusous soils of the Akjoujt-Tasiasit axis.   The optimum Proctor test results are listed in the following table 4: Table 4:-Proctor Results.

CBR Results
The CBR values shown in this table 6 are greater than 5, which justifies that it does not require an earthwork level for our two study areas, which leads us to confirm that the soil in situ will play the role pavement support sub-layer. [14][15].