As Jamaica continues to experience the ravages of road infrastructure failure, resulting from sustained rainfall in the latter part of last year, many may contemplate whether or not we have done enough, as a country, to alleviate this issue.
This article will explore why roads fail and what can be done about it.
Road design is a separate issue from proper drainage mechanisms
Project and procurement management in construction and engineering are central considerations for improving our road infrastructure
Economic impracticalities associated with infrastructural upgrades hinder the country’s roadwork improvement
High-level leadership is paramount in improving the country’s road infrastructure.
Who governs the roads of Jamaica?
The National Works Agency (NWA) is directly responsible for Jamaica’s main road networkwhich spans5000 kmand is classified into class A, B, and C roads. Parochial (14,895 km) and community roads (4,200 km) fall under the purview of the local authorities, i.e., the parish councils, while farm roads (1,500 km) are the responsibility of the Ministry of
The Geology of Jamaica
Approximately two-thirds of the country consists of limestone formation and bauxite. Notably, these areas tend to experience fewer road failures because stormwater flows through the limestone and bauxite into the underground aquifers, more often than not.
The other third of Jamaica consists of a multitude of rocks and soil conditions, including sedimentary types. These areas tend to have water bodies flowing atop them which increases the likelihood of flooding.
Examining the Issue
There are several layers that make up a road structure, i.e., the sub-grade, sub-base, base course, and surface. The sub-grade is made up of native soil that has been compacted to withstand the loads above it. The sub-base is the layer of soil or aggregate on top of the
subgrade. The base course is the layer of soil installed above the sub-base and it is designed to help transition surface loads from the pavement to the sub-grade, evenly support the pavement surface, and protect the overall pavement system from water intrusion and deformation. The road surface, or pavement, is the material laid above the sub-base on an area intended to sustain vehicular or foot traffic, such as a road or walkway.
Why do roads Fail?
Common causes of road failures are:
insufficient strength properties of asphaltic mixes;
the movement of heavily-loaded vehicles;
poor drainage conditions, and natural disasters.
Pavement failure issues may include cracking, potholes, depressions, rutting, shoving, upheavals, and ravelling. Rutting is when permanent deformation accumulates in an asphalt
pavement surface over time and is evidenced by the wheel path being engraved in the road. Shoving is the deflection and bulging of the road surface due to traffic loads. Ravellingis the separation of the asphalt from the road surface as a result of deterioration, over time.
A Penchant for Quick Fixes
Applying a topcoat or second layer can be tempting when faced with pavement damage, but when there is an underlying structural problem these solutions will be short-lived. Instead of wasting time and money on a quick fix, it makes sense to assess the cause and invest in an appropriate solution.
When premature pavement failure occurs, it is usually a result of general soil issues, localized soil issues, or poor fabrication and engineering. These issues include:
1. Poor Soil
Even the best-designed and properly installed pavement will fail if the subsoil has structural issues. For example, in the Arcadia area of Kingston, where much of the soil profile consists of clay, it may be common to see a concrete wall leaning forward or backward because of the specific properties of clay which may not transfer load as well as other soil types.
The most common threat to soil integrity is a high water table which is a measure of the amount of saturation in the soil. If not accounted for at the time of construction, a high water table will erode the soil and eventually lead to pavement failure. A sign of an area with a high water table is if your neighbours experience similar flooding issues. It is also likely to be the case if your home is near a water source such as a stream or river.
If poor soil is the primary issue, resurfacing the pavement will not last long enough to be worth the expense. Once the soil issue results in pavement deterioration, it is highly likely that the subsurface (sub-base and base course) is already in such poor condition that the new surface will deteriorate, quicker than anticipated.
2. Poor Design and Fabrication
Although the subsurface is critical to a successful pavement, pavement design and fabrication are also important. Inappropriate cost-cutting during the initial design and installation is usually linked to poor design and fabrication—either because the project owner demanded cheap options, the engineer did not know enough to put in the right materials, or the construction company cut corners where it should not have.
An inappropriate base course is a common example of poor design and fabrication. Problems can also occur in the choice and design of the wearing course (the layer which keeps water from permeating), or the asphalt itself. For example, when marl is used as the base course in road construction and it is not sufficiently protected from moisture and water, the result is a reduced California Bearing Ratio (CBR). The CBR is a test used to evaluate the subgrade strength of roads and pavements.
Understanding and addressing the issues associated with the complex matter of road infrastructure development in Jamaica will help us to make better decisions about our road development and remediation.
By Shaquille Johnson
University of Technology, Jamaica student pursuing a Bachelor of Engineering in Civil Engineering