Almost none of the site investigations works undertaken in the capital satisfy minimum code provision, a study finds. Excavation support system failures are also becoming more rampant

Almost none of the site investigations works undertaken in the capital satisfy minimum code provision, a study finds. Excavation support system failures are also becoming more rampant

A recent study on contemporary practices of geotechnical engineering in Ethiopia with a focus on site investigation reveals that almost all of the site investigation works undertaken for building construction purposes fail to fulfill the minimum requirements set forth by the Ethiopian Building Code of Standards. The study has been commissioned by Addis Ababa University Research Office and undertaken by collaborating researchers from Addis Ababa Institute of Technology (AAiT) and Aalto University of Finland. The findings of the two yearlong research were presented at the very first Geotechnical Engineering workshop organized by the Ethiopian Geotechnical Society (EGS).

EGS Geotech Workshop 2023 featured a key note speech by the well renowned geotechnical engineering specialist and educator Emeritus Professor Alemayehu Teferra. The professor who is commonly known as “the Father of Geotechnical Engineering Practice in Ethiopia” presented his take on the evolution of geotechnical engineering practice in the world and in Ethiopia intertwined with his own personal and professional journey. It was later-on announced that the Society has officially launched an annual distinguished lecture series in honor of Prof. Alemayehu and his presentation on the workshop was dubbed as the inaugural lecture of the series. Speaking on the matter, Dr. Tezera Firew Azmatch, president of Ethiopian Geotechnical Society, highlighted that Prof. Alemayehu’s contribution to civil engineering in general and geotechnical engineering in particular is stellar both in practice and academia. The lecture series, labeled as “Prof. Alemayehu Teferra Lecture Series”, will be featuring distinguished giants of the field both from Ethiopia and abroad, Dr. Tezera added.

In addition to the honorable professor, five more professionals from academia and industry practice presented their research findings on site investigation and excavation support system practice.

The aforementioned research on contemporary site investigation practice in Ethiopia conducted by Dr. Tensay GebreMedhin, Tewodros Gemechu and Abdi Bichaka (and presented by the former) revealed a number of shocking findings. Soil investigation by the way of boreholes is a prescribed mandatory requirement in Ethiopia for construction of buildings above G+1 levels. The code has set standards regarding the depth of investigation, number of boreholes and their distribution on the site in question. With regard to depth of boreholes 95 % of the site investigation works carried out to date fail to satisfy the minimum requirement set forth by the Code. The borehole number requirement is relatively on good level of practice with a whopping 90 % of the sites fulfilling it. As for the distribution of boreholes on the site, the study shows mixed outputs. For proper characterization of site, the code recommends a well thought out spatial distribution of boreholes which includes extremes (boundaries) of the site and the geometric center. It has been pointed out that almost half of the site investigation works fail to illustrate this since they do not incorporate accurate borehole location data in their reports. In addition to missing information, several instances indicate wrong borehole coordinates some of which are even outside the scope of Addis Ababa city. Moreover, a number of duplicated site investigation reports have been discovered.

As a way forward, the researchers recommended several interventions. These include capacity building schemes for geotechnical engineers and regulatory bodies, digitization of geotechnical data, greater involvement of geotechnical engineers from the early days of a project, implementation and integration of BIM in geotechnical practice, and development of relevant manuals, guidelines, and standards.

A case study presented by Tewodros Gemechu under the title “Site Investigation as an Evolving and Dynamic Task: Evidences from Selected Projects” shows that greater involvement of geotechnical engineering professionals in projects, leading to dynamic updating of subsurface information, ultimately results in significant saving on the total project cost. The pilot studies for the research involved production of full-fledged site investigation plan prior to mobilization, active supervision of field and laboratory works, discussion and updating of methodology in real-time, presentation and discussion on submitted reports and continuous updating of subsurface information during shoring works and excavation. These interventions resulted in a 25 % increase in the professional fee of the involved geotechnical engineers which merely amounts to 0.005 % of the project cost. Concurrently, they resulted in 12.5 % and 23 % decrease in expense to the Client due to dynamic updating of shoring and foundation design respectively. These numbers correspond to a 2.2 % and 1.3 % of the total project cost respectively, which ultimately resulted in a net saving of saving of 3.45 % of the project cost.

Excavation support theory, design and construction was the other theme of the workshop. Under the title “Frontiers of Earth Retaining Systems”, Dr. Henok Fikre presented a number of alternative excavation support systems being practiced abroad and cutting edge technologies under development. He added that there is a tendency among the industry in Ethiopia to focus on pile shoring works as the sole option of temporary support system. Next, glaring gaps in the design practice of shoring works has been presented by Leamlak Minwuyelet. The confusion created by the direct adoption of European Norms in the current building code ranges from determining on favorable and unfavorable loading conditions upto selection of design combination, as per Leamlak. He highlighted the need for the development of a national annex to the building code and called for practitioners to exercise strain and make conscious decisions and assumptions in shoring design. Construction stage negligence, poor workmanship, inappropriate materials usage has been raised by Ayalneh Wondimu as major sources of shoring failures. Ayalneh, a seasoned geotechnical engineer with vast experiences in North America and Ethiopia, presented his take on the current state of the practice using examples from a number of high-stake projects he has been involved in. Cases of failed shoring works presented at the workshop showcased that design assumptions and low quality site investigation reports are among the major culprits in addition to the obvious construction errors and quality compromisation.

A panel discussion ensued after the presentation where a number of stakeholders aired their take on the matter and called for continuous professional development by a way of a series of trainings. It has been pointed out that site investigation and excavation support construction are the only two unsupervised construction activities in the current Ethiopian civil engineering practice.

On his closing remark, the president of the Society Dr. Tezera acknowledged the need and announced that the Society is finalizing its preparations to provide a series of training on shoring design. In addition, he remarked that the proceeding of the workshop will be presented to a number of stakeholder and regulatory bodies in the government to start the discussion for strategic intervention before a major calamity occurs due to compromised quality of geotechnical works.