Helping to build better roads in the region

By: Ts. Dr. Herda Yati Katman

Many road projects in Malaysia and Indonesia have been constructed on soft clay. Geological studies have shown that soft clay covers a significant portion of both countries. Soft ground poses significant challenges due to the extreme softness, unconsolidated, and possesses low shear strength, stiffness, and high-water content. Consequently, these characteristics give rise to serious issues such as an excessive and long-term settlement during or after construction which results in time and cost overruns in construction projects. The soil’s compressibility coupled with the loading from vehicles, causes the road surface to settle. This pose risks to road users, as uneven road surfaces can disrupt driving and cause accidents.

To address these challenges, prefabricated vertical drains (PVDs) have emerged as an economical and effective solution for treating soft ground, particularly for mitigating long-term foundation settlements by accelerating soft clay consolidation. Previous studies have revealed that PVDs are effective in stabilizing the soft subgrade soils. It is critically essential to investigate the improvement of soil properties through PVDs installation under moving loads at different traffic levels to mitigate settlement issues and reduce the risk of accidents caused by uneven road conditions.

Study on the conventional constitutive models is very limited for the long-term behaviour of soft soils under high-cycle traffic loading. Current research for road embankment on soft clay stabilized with PVDs often prioritizes static traffic loading over dynamic loading due to practical consideration and simplification of the problem. Dynamic traffic loading involves a multitude of constantly changing variables, including varying vehicle speeds and fluctuating traffic volumes and patterns. These complexities can make it challenging to develop accurate models and conduct comprehensive studies, underscoring the need for our research to fill this critical knowledge gap.

In our pursuit to overcome these limitations, this research conducted in partnership with Pertamina University Indonesia and in collaboration with industry partners from Ceteau Malaysia Sdn Bhd and Minconsult Sdn Bhd., aims to investigate the settlement behaviours of soft ground in Malaysia and Indonesia, specifically focusing on the influence of road embankments, traffic loadings, and the performance of PVDs. An innovative approach will be adopted by simulating traffic scenarios based on different traffic categories as outlined in Arahan Teknik Jalan (ATJ) 5/85 and the design standard in Indonesia. By considering these traffic categories, the research can create traffic loading models that closely resemble real-world traffic conditions.

In addition to analysing the performance of PVDs, our work will also explore novel designs and optimisation methods for PVDs in soft ground improvement. The research will focus on developing a comprehensive understanding of factors that influence PVD performance, such as PVD type, layout, number and length, as well as the minimum space between insertions. This exploration will involve conducting laboratory testing, field measurements, and numerical modelling to evaluate the behaviour and effectiveness of different PVD configurations under dynamic loadings and embankment construction. The innovative approach involves considering the interaction between traffic loading and the performance of prefabricated vertical drains (PVDs). This way, the research can explore how the presence of PVDs influences the settlement behaviour of the soft ground under dynamic traffic loads and assess the effectiveness of PVDs in mitigating settlements in such conditions.

In conclusion, by investigating the settlement behaviours of soft ground under the influence of road embankments, traffic loadings, and the performance of PVDs, our work seeks to develop effective solutions that mitigate settlement issues and reduce the risk of accidents caused by uneven road conditions. Hopefully, we can provide valuable insights to engineers and other stakeholders for more effective road design in the future.

Together, these collaborations enable us to combine academic efforts with real-world perspectives, enhancing the relevance and impact of our work on the development of reliable and sustainable road infrastructure, not just in both countries but the region too.

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The author is a Senior Lecturer at the College of Engineering, Universiti Tenaga Nasional (UNITEN) and may be reached at herda@uniten.edu.my