EROSION CONTROL OF THE ROAD EMBANKMENT IN EGYPT

Abstract

In the past few years, considerable research efforts have been made in the field of pavement engineering in order to develop performing asphalt concrete mixes and design adequate pavement structures. These researches were done in order to increase pavement performance and save on construction, maintenance and rehabilitation costs. In spite of this, there are only few researches that deal with the effect of the hydrological properties (precipitation, infiltration, runoff and storage) on the road elements although the erosion is one of the major problems faces roads construction. Erosion control in roads construction may begin prior to material placement during construction phase. This is by choosing the best fit alignment to the natural terrain and appropriate design for the road elements. There is a lack of information in the relation between the hydrological properties and the appropriate erosion control method to be used in Egyptian roads.

It is noticed that there are many problems such as ruts, bumps, potholes or even failure often encountered on road elements (Granular shoulders, unprotected side slope and lower toe). This is due to the loss of particles, usually finer particles, due to environmental factors (rain, surface runoff and wind). This loss tends to cause a weakening of granular skeleton by reducing contacts between particles.

From these points and to overcome this problem this research aims to study the effect of varying the granular materials gradations and the water content on the erosion of the materials used in roads construction. This is done by studying the hydrological elements related to roads engineering and their effect on road elements design.

To achieve the research objectives, four phases were conducted. • The first phase: deals with the hydrological cycle especially the elements related to the roads engineering which are precipitation, infiltration, and runoff. Also the erosion of the road embankment and the different measures that used to control the erosion for road elements: (road bed, shoulders and side slope). • The second phase: deals with the effect of varying the granular materials gradations in erosion resistance. To achieve this aim a laboratory technique for measuring the effect of water flow within embankment material was developed. The effect of granular material gradations were examined in laboratory providing that the Egyptian specifications limits are applied. Ten curves were examined in order to study the effect of varying the gradations in erosion resistance. • The third phase: focuses on the relation between the granular materials gradations parameters (Fine/sand ratio, uniformity coefficient and porosity) on the erosion resistance. • The fourth phase: In addition to modeling the roads embankment side slopes to study the factors that affect on the erosion of the unprotected side slopes.

The findings of this research were that a modification in the gradation of granular material is likely to improve the erosion resistance of the embankment material. Also it was found that granular materials erosion resistance improves with the increase of the uniformity coefficient, increase of fine/sand ratio (increase of fines) and decrease of porosity. The gradations that improve the erosion resistance were found not affecting the required engineering properties of road embankments. The erosion control by using gradation modification is an economical erosion control measure.

Key words: Road embankment; Hydrological cycle; Erosion control;