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Wrap-faced dykes can minimise costs: Study

Published : 28 Jun 2021 09:42 PM

The land acquisition cost for building roads and highways can be widely minimized using wrap-faced embankments as it allows using two times less space which will also be more capable of responding to any severe quake compared to traditional embankments.

The embankments, proved in a study applicable to country’s soft soil, can be made 70 percent less costing than the traditional embankments as it allows constructing embankments using 60-70 percent less land space, according to the findings of the Ph.D. thesis of Dr Ripon Hore, Civil Engineering Department, Bangladesh University of Engineering and Technology (BUET).

The physical model of the embankments has been prepared with two soil layers—clayey soil as the lower layer and sandy soil as the upper layer, according to the study.

The outputs will be useful to predict the dynamic behavior of wrap-faced embankment on soft clay, the researchers found after investigating the seismic effect due to different input motion on the wrap-faced soil walls by performing shaking table tests and numerical analysis using PLAXIS 3D.

Application of the wrap-faced method in constructing roads and railways could be a blessing for any agro-centric economy like Bangladesh for both minimizing land acquisition and being earthquake responsive, said Dr. Mehedi Ahmed Ansary, superviser of the thesis also Professor of the Civil Engineering Department of BUET.

A project applying the method, which is popular in many countries including Japan, can be implemented with 30 crore taka while it will take at least 100 crore in the traditional method, added the professor.

Preventing measures are being taken in our country while building houses, flyovers and other projects but none of the implemented projects of roads and railways considers dynamic loading in the design phases what makes the country’s roads and highways vulnerable to any severe quake like kobe earthquake-1995 or Loma-Prieta 1989, said Dr Ripon Hore.

“No study has been conducted yet on our country’s soft soil, which is different from any other countries, to build wrap-faced embankments that can carry a higher dynamic/seismic load than the traditional embankments,” Ripon said.

Four successive mild earthquakes have shaken Sylhet recently which could be a warning sign of a major earthquake in the country, say experts.

Three consecutive studies have been conducted titled ‘Dynamic Response of Reinforced Soil Retaining Wall Resting on Soft Clay’, ‘Dynamic Responses of Reinforced Soil Model Wall on Soft Clay Foundation’ and ‘Seismic Response of Embankment on Soft Clay Based on Shaking Table Test’ in the last six years. All the researches have been published in the world’s top-class journals.

The findings from the analysis of the seismic behaviour of embankment will play a vital role in developing a standard design specification for such walls for the roads and railways department of Bangladesh.