Journal article Open Access

ENGINEERING PROPERTIES OF MECHANICALLY STABILIZED SUBBASE MATERIAL USING NATURAL GRAVEL AROUND JIMMA QUARRY SITES FOR UNPAVED ROAD CONSTRUCTION

Ejeta, Almaz; Prof. Emer Tucay Quezon; Getachew, Kabtamu

Unpaved roads are designed with a small input and are constructed from the nearest available materials as possible. It requires routine and periodic maintenance, and their condition can be significantly affected by a period of excessive traffic volumes or inclement weather conditions. The accurate estimation of maintenance costs is difficult. Many problems occur in the economic analysis of unpaved roads in comparison with paved roads. Defects that may affect unpaved roads are dusty, potholes, stoneness, corrugations, and rutting. Hence, it needs to apply a sufficient stabilization method to strengthen and increase the durability of the unpaved road. Mechanical stabilization is an important application in engineering for different types of construction to improve the performance of road construction materials. The objective of this research was to determine the Engineering properties of natural gravel materials by mechanical stabilization method to be used in subbase material for the unpaved road. The methodology carried out in this research study includes: (a) field visual inspection and sampling of natural gravel materials from three quarry sites around the Jimma area; and (b) laboratory tests to identify the physical and mechanical properties of natural gravel. Based on the laboratory test results, natural gravel materials from the Seka quarry site has an excellent Abrasion resistance of 35.26%, Plasticity Index of 13% a little bit above the upper limit, and good gradation (coarser and less subtle or binder materials), right CBR value. While the Jiren quarry site has a little Abrasion resistance of 52.09%, medium plasticity index, poor gradation (moderate fine material), CBR value of 28.90% which was below 30% minimum requirement, but had good MDD. On the other hand, the Merewa quarry site comprised of a very poor Abrasion resistance of 78.34%, Plasticity Index of 23.90%, which was beyond the upper limit plasticity index of 12%, and poor gradation (more fine materials), poor CBR value and poor MDD. Therefore, it is concluded that the natural gravel from the Seka quarry site is suitable for the subbase course. But since road construction around Jimma is booming, the natural gravel from this quarry site would be soon depleted. About this, mechanical stabilization is recommended by blending the natural gravel from Seka quarry site with 54% by weight with Jiren natural gravel of 46% by weight to meet the minimum requirements for subbase materials.

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