Sustainable Road Shoulders and Pavement Protection for Expansive Soil Zones

Abstract

The design of sustainable infrastructure roads in semi-arid highly expansive soil is of concern to the geotechnical and pavement design engineers. The damage and distress caused to highways and roads in areas with high swell potential occur as a result of ingress and infiltration of water to the underside of light pavements. These pavements exert very low stresses on the ground. Protection of subgrade and shoulders against variation in moisture content as a result of seasonal weather fluctuation and floods can help in establishing a sustainable pavement for an extended lifetime. Predicting the response of a subgrade soil subjected to different rainfall intensity and frequencies is very challenging. The approach proposed in this study is to target a reduction of moisture exposure to prevent water from entering the systems. However, efficient protection is required when severe floods occur so as to remove water from the shoulders in a short time. The sloping shoulders are intended to guide floodwater away from the pavement. Clay-sand liners can be constructed as a dressing layer along the shoulders or within the body of the shoulder extending up to the toe of the slope or beyond. Assessment of a typical sand–clay liner was conducted. Suggested designs were based on characterization, compressibility, and hydraulic conductivity tests. It was found that stresses exerted on the liners do not pose a significant settlement hazard.

Identifying Problematic Soils Using Compressibility and Suction Characteristics

“…The Saudi Building Code SBC 303 also states that footings or foundations for buildings and structures founded on collapsible soil areas shall be designed based on the collapse potential determined using the collapse index method, the standard plate load test method, or BREA Building Regulations in Eastern Arriyadh Sensitive Soils Procedures (BPLT). Dafalla et al [19] called for the use of protective measures for pavements using clay-sand liners and suggested a drainage system. Pre-wetting approaches are not recommended for expansive soil under pavement, as wetting requires a long time to inundate the clay particles.…”

“…Studies conducted by Erol and Dhowian [17], Aiban [18], Dafalla et al [19], Shaker and Elkady [20], Al-Mahbashi [21], Al-Mahbashi and Elkady [22], and Elkady et al [23] all addressed the geotechnical parameters and behavior of different types of highly plastic soils encountered in Saudi Arabia. The term "collapsible soil" has been used since 1970, but the existence of this type of soil has been recognized since World War II [24].…”

Modeling of road performance assessment based on pavement, shoulder, and drainage

“…Road shoulder and drainage are units that influence each other. Poor drainage and shoulder conditions affect other components (Dafalla, Shaker, & Al-Shamrano, 2022 [7]). [11] carried out a study on the impact of each type of damage on the performance of road shoulders and drainage.…”