Managing water in road embankment and pavement design, construction, and maintenance (part 1)

One thing that I have learnt in civil engineering, and in particular earthworks and pavement design, construction, and maintenance is that uncontrolled water is our greatest enemy.

To qualify this, whilst the right amount of moisture in our embankments and pavements is needed to achieve compaction, so many of the causes of failed pavements/embankments can be tied to when flowing water or soil moisture is incorrectly managed.

Engineering works, especially geotechnical works, require specific care in relation to soil moisture content and flowing water due to their influence on structural integrity. In regards to trafficked roadways, water can influence not only the structural integrity but also road safety.

Thorough soil analysis to determine its physical properties is extremely important to define the soil bearing capacity. Soil bearing capacity is typically measured through California Bearing Ratio test (CBR), and it is related to the degree of compaction or maximum dry density (MDD).

Water that comes into contact with the pavement or embankment layers influences the behaviour and the structural performance, due to a change in the degree of compaction. When soil comes in contact with water it increases its volume, which causes the separation of grains and destructuring of layer, reducing its bearing capacity and resilient modulus. Over time, excess moisture in the structure affects the pavement life cycle by reducing its resilience, thereby becoming susceptible to distresses such as cracks, potholes or shear rupture.

Excessive moisture in pavements can be due to superficial infiltrations through cracks or joints, or through the groundwater itself. When constructing roads in the presence of a high water table, careful consideration is also required and strategies including preloading, wick drains in the preconstruction phase may be required. Drainage layers utilising interlocking rock layers to effectively bridge these areas and protect the embankment and ultimately the pavement may also be considered.

Following construction, in the maintenance phase of a pavement’s life, it is essential to maintain the integrity of the sealed surface. Where cracks have developed due to settlement or shrinkage, intervention measures such as crack sealing/filling are often used.

Water is one of the main causes of pavement distresses, therefore if keeping these structures in good condition and properly sealed, it results in a durable pavement, safe and saving over the years. However, even in public infrastructure, the amount of unsealed roads far outweighs the number of sealed roadways. In industries, such as mining, this statistic is even higher due to the cost of maintaining a sealed surface under such heavy loadings.

In these situations what can be done? Please read the next article in this series for an examination of GRT’s innovative unsealed road maintenance technologies.

For more information please contact GRT