This paper presents the geotechnical characterization in peat ground using the electric cone penetration test (CPTu). Peat is well known to be a problematic and very soft soil with peculiar engineering properties. As peat ground is accumulated heterogeneously, it is not valid to determine the mean mechanical parameter of the entire peat layer from laboratory soil test on a small number of samples. On the other hand, CPTu can provide continuous soil information. Therefore, it is more reasonable and appropriate to first determine the relationship between the CPTu result and each mechanical parameter and then estimate the mean mechanical parameter of the entire peat layer from the correlation. In this study, therefore, CPTu, PS velocity logging, in-situ hydraulic conductivity test using borehole and peat soil sampling were conducted at several sites in Hokkaido, Japan. Furthermore, a series of mechanical soil tests (K0 consolidated-undrained triaxial compression test, cyclic torsional shear test) were conducted on the collected peat soils. Based on these geotechnical investigation results, first the characteristics of the CPTu profile of the peat ground were described. Then the correlation between the CPTu results and the mechanical parameters (undrained shear strength, shear modulus at small strain and hydraulic conductivity) of peat and a method for determining these mechanical parameters of peat from the CPTu results were presented.

Dr. Hirochika Hayashi is a Technical Manager at the Sapporo Branch of Nittoc Construction Co., Ltd.. He previously worked at the Civil Engineering Research Institute for Cold Region. Dr. Hayashi received his PhD in Civil Engineering from Hokkaido University in 2006 and his Bachelor of Engineering from Nihon University in 1986. His expertise focuses on peat and soft soil engineering, including soil improvement techniques such as deep mixing, vacuum consolidation, and prefabricated vertical drains (PVD). His research also involves field observation, laboratory testing, centrifuge model testing, and numerical analysis related to ground behavior. Dr. Hayashi is a registered APEC Engineer (Civil) and Professional Engineer of Japan (Soil & Foundation / Management). He has authored more than 150 technical papers in journals and conferences and contributed to seven books in the field of geotechnical engineering.

Accurate in-situ characterization of groundwater flow in rock–soil media plays a critical role in civil engineering, transportation, water conservancy, geology, and related fields. Addressing the limitations of conventional in-situ testing methods, such as low accuracy, inefficiency, and high cost, we propose a novel active distributed temperature sensing (A-DTS) based approach enabling precise and fine-scale in-situ assessment of both thermal conductivity and seepage within rock–soil media. This report will first introduce the fundamental principles for A-DTS based thermal conductivity measurement, then utilize combined numerical simulations and laboratory experiments to investigate the potential influence of various key factors on test outcomes, leading to the establishment of a standardized in-situ testing methodology for thermal conductivity. Furthermore, based on moving line heat source theory, a novel quantitative method for the precise characterization of seepage velocity is presented, representing a technological breakthrough that significantly enhances the spatial resolution and efficiency of groundwater flow detection while resolving the cost and complexity challenges inherent in traditional multi-borehole monitoring techniques. The presenter will introduce applications of this novel technology across geotechnical site investigation, geothermal resource exploration, embankment/dam seepage hazard prevention, and tunnel engineering, aiming to provide new insights and promote the wider application of DTS technology for the efficient in-situ measurement of multiple physical parameters in rock–soil media.

Dr. Kai Gu is a full professor in Engineering Geology at the School of Earth Sciences and Engineering, Nanjing University, China. He serves as Vice-Secretary General of the International Society of Environmental Geotechnology (ISEG), Associate of the UNESCO Land Subsidence International Initiative (LaSII), and Council Member of the Division of Intelligent Monitoring in Geology and Geotechnical Engineering of the Chinese Society for Rock Mechanics and Engineering (CSRME). He received his BSc and PhD from Nanjing University in 2009 and 2014, respectively, and was a visiting scholar at the University of Cambridge from 2012 to 2013. His expertise includes multi-physics field monitoring with fiber-optic technology, shallow geothermal energy, and geoenvironmental engineering with sustainable materials. He has led 16 projects and published over 90 peer-reviewed papers. He received the First Prize of the National Science and Technology Progress Award (2018) as a team member, Silver Award at the Geneva International Invention Exhibition (2023), ICGdR Outstanding Young Scientist Award (2020), Second Prize of Science and Technology Progress Award of Jiangsu Higher Education Institutions (2023), and Jiangsu Patent Silver Award (2023), among others.

For geotechnical construction projects above and below ground, major issues or even failures can occur as the ground conditions can be highly variable such as those in Singapore. Mediation, arbitration or even court cases may take place if the disputes can be resolved between various stakeholders of the project. Investigation on causes of geotechnical issues and failures are often not straightforward and thorough investigations are often necessary with engineers and lawyers from various parties often hold vastly different opinions. In addition, post incident investigations often pose a good number of missing vital information. In this lecture, through a number of case studies in Singapore and overseas, the methods and techniques of forensic geotechnics are highlighted. Viable approaches to solving the causes of geotechnical incidents are highlighted, as demonstrated by actual case studies. This lecture further examines the roles of engineering experts and lawyers particularly on the details of the contract documents. At times, the view of engineers and lawyers can be different, and reconciliation is needed for the case to go forward logically for the plaintiff or the defendant. It is important to note that the legal viewpoints can differ from that of engineering viewpoints. Lessons learned from these case studies on forensic geotechnics will be presented to enable engineers and lawyers to tackle future geotechnical incidents effectively and efficiently.

Professor C F Leung is a prestigious Yangtze Professor at Shandong University in China. He is also conferred the title of Emeritus Professor upon his retirement from the National University of Singapore. Prof Leung is a Fellow of the Academy of Engineers of Singapore and a professional engineer geotechnical specialist. He has served as a geotechnical consultant for over 100 projects in Singapore and overseas. Prof Leung has wide research interests in marine and offshore geotechnics having published over 120 articles in top tier geotechnical and offshore engineering journals. He is the Executive Editor-in-Charge of the Journal on Deep Underground Science and Engineering published by Wiley. Prof Leung is also on the editorial board of a good number of geotechnical and offshore engineering journals. He has delivered over 20 keynote/invited lectures at International and Regional Geotechnical and Offshore Engineering Conference.

The expansion of infrastructure in Malaysia increasingly necessitates construction on marginal ground, particularly tropical peatlands. These soils, characterised by high moisture content, large void ratios, and extreme compressibility, present significant geotechnical challenges. This study, conducted by the Research Centre for Soft Soil (RECESS), investigates the engineering behaviour of Malaysian peat through an integrated framework combining laboratory index testing and in-situ characterisation using the Piezocone Penetration Test (CPTu). Laboratory tests, including moisture content, loss on ignition, and specific gravity, are utilised to classify peat and determine its degree of decomposition. However, the disturbance of the fibrous structure during sampling limits the reliability of laboratory-derived strength and compressibility parameters. To address this limitation, CPTu testing is employed to obtain continuous, high-resolution profiles of cone resistance, sleeve friction, and pore water pressure under in-situ conditions. The integration of laboratory and CPTu data enables improved interpretation of peat stratigraphy, identification of anomalies such as buried wood, and more reliable estimation of undrained shear strength. This approach provides a robust basis for contributing to safer and more sustainable infrastructure development on tropical peatlands

Adnan Zainorabidin is a distinguished Professor in Geotechnical Engineering, specialising in peat soil technology and soft ground engineering. He obtained his Certificate in Civil Engineering from Polytechnic Port Dickson in 1994, followed by a Bachelor of Civil Engineering (Hons) in 1997. He later completed a Master’s Degree in Research (Geotechnics) in 2003, focusing on the geotechnical properties of peat soils in Johor, and earned his PhD from the University of East London, United Kingdom in 2011. He joined Universiti Tun Hussein Onn Malaysia (UTHM) in 2000 and has accumulated over 26 years of experience in teaching, research, and consultancy. He is the founding head of the Research Centre for Soft Soil (RECESS), established in 2004, which has since developed into a nationally and internationally recognised centre of excellence in soft soil research. Professor Adnan has supervised more than 40 postgraduate students and authored over 150 publications in journals, conferences, and symposiums. He is a frequent keynote speaker at both local and international platforms and actively contributes as a consultant, particularly in forensic investigations of construction failures on peat soils. His research interests include innovative ground improvement techniques, advanced in-situ testing methods for peat characterisation, and sustainable construction practices in peatland environments. His expertise has contributed to the development of the Malaysian Guidelines for Construction on Peat Soil (CREAM, 2015 & 2020). He has been recognised as a Top 10 Outstanding Researcher (2020–2021) and was ranked 3rd among UTHM researchers for international research grants in 2021.

This paper presents a forensic geotechnical investigation of the catastrophic structural failure of a concrete sheet-pile retaining wall following a shallow 3-meter canal excavation on reclaimed coastal land in Semarang, Indonesia. The area contains deep deposits of ultra-soft, highly compressible marine clay undergoing severe subsidence. After excavation, the retaining structures exhibited massive lateral translation, outward tilting, and rupture of the cap beam. To determine the failure mechanism, a geotechnical instrumentation program integrating deep boreholes with continuous Piezocone Penetration Testing (CPTu) was deployed. Advanced hydro-mechanical profiling captured extreme dynamic pore-water pressure anomalies, confirming a critical state of severe underconsolidation driven by rapid deposition of embankment fill. The analysis shows that undissipated excess pore pressures induced a visco-plastic mudwave effect, completely eliminating passive toe resistance. Remediation strategies incorporating surcharge preloading, prefabricated vertical drains, and anchored secant walls are evaluated to ensure long-term infrastructural resilience against similar geohazards.

Ir. Dr. Hj. Ramli bin Hj. Nazir served as a lecturer in the Geotechnical and Transportation Department at Universiti Teknologi Malaysia from 1989 until his retirement as a Professor of Geotechnical Engineering in 2021. He earned a BEng in Civil Engineering from UTM in 1983 and a PhD from the University of Liverpool in 1994, specialising in Geotechnical Engineering. With over 30 years of experience in this field, he focuses particularly on Foundations, Ground Improvement, and Geotechnical Forensics Engineering. He has published more than 200 technical papers and articles related to his area of expertise and has been invited to deliver keynote speeches at over 70 conferences and seminars worldwide. As a Professor of Geotechnical Engineering and a Fellow of the Malaysian Academic Profession (FAPM), he is a Registered Professional Engineer with a Practising Certificate from the Board of Engineers Malaysia. He possesses extensive experience as a Design Engineer, Design Checker, and Geotechnical Technical Advisor for various government and private agencies involved in numerous Civil Forensic projects, including Structural and Infrastructure works in Malaysia. Additionally, he was a Member of the Technical Committee on Eurocode 7 Malaysian Annex, responsible for adapting Eurocode 7 to local requirements from 2010 to 2018 and served as a Research Committee Member for the Construction and Industrial Development Board of Malaysia as well as the Public Works Department of Malaysia. On an international level, he is an invited fellow member of the Indonesian Society of Geotechnical Engineering (HATTI) and serves on the international expert panel for the National Earthquake Study Centre Indonesia (PUSGEN). He also provides expert support for the Standards and Industrial Research Institute of Malaysia (SIRIM) and the Public Works Department (JKR) in designing specifications for specialised projects such as Soil Anchors and Load Testing. Furthermore, he was appointed by the TYT of Penang to serve as a member of the National Slope Failure Enquiry Commission for the Tg Bungah slope failure case from 2017 to 2019. He also acts as an invited Geotechnical speaker for training and workshops for governmental and private technical agencies, including JKR, PETRONAS, SHELL, the Malaysia Productivity Corporation, and various private consultancy firms. Prof. Ramli was appointed as a visiting Professor at Universiti Islam Sultan Agong, Indonesia, and L. N. Gumilyov Eurasian National University in 2003 and 2019, respectively. Currently, he holds the position of Adjunct Professor at Universitas Parahyangan Bandung, Indonesia, and is a Distinguished Fellow at the Centre of Tropical Geoengineering at Universiti Teknologi Malaysia.

TBA

Dr. Liu Yu is currently the Director of the Indonesia Branch of Shanghai Geoharbour Construction (Group) Co., Ltd., a position he has held since July 2012. He holds a Ph.D. in Geotechnical Engineering from Zhejiang University (2004–2010) with research and professional expertise focused on soil improvement methods such as vacuum consolidation, dynamic compaction, vibroflotation, stone column, and deep cement mixing, as well as pile foundation and reclamation projects.

The Pressuremeter test is commonly employed to determine the soil deformation modulus of both cohesive and cohesionless soils, as well as the undrained shear strength of clayey soils. At present, it remains the only in-situ soil testing technique capable of producing a complete stress–strain curve for the soil under investigation. Although the stress–strain curve obtained reflects lateral loading conditions, it bears notable similarity to the curve derived from conventional laboratory triaxial testing. Building on this observation, a method is proposed to calculate the effective shear strength of soil. The procedure involves establishing the relationship between Pressuremeter-induced cylindrical cavity expansion stresses and the corresponding radial strain, followed by matching the experimental Pressuremeter curve with the theoretical cavity expansion stress–strain response. Through this approach, the effective shear strength parameters—namely, effective cohesion and effective friction angle—can be derived. Actual Pressuremeter data are then utilized to validate the theory, and the resulting parameters are compared with triaxial test results. The comparison indicates that the parameters obtained from the Pressuremeter test are closely aligned with those derived from triaxial testing.

Dr. Ir. (IPU) Gouw Tjie Liong, M.Eng., ChFC is a Senior Professional Geotechnical Consultant and Geotechnical Engineering Trainer/Lecturer based in Indonesia. He has over four decades of experience in geotechnical engineering, specializing in site investigation, soil instrumentation, deep foundation, and ground improvement techniques. He obtained his undergraduate and doctoral degrees in Civil Engineering from Parahyangan Catholic University, Indonesia, and his Master’s degree in Geotechnical Engineering from Asian Institute of Technology, Thailand. Since 1984, Dr. Gouw has been actively involved in the design and execution of geotechnical investigations, including in-situ testing (SPT, CPT, PDA, PIT), slope stability, tunneling, and soil improvement methods such as dynamic compaction, vertical drains, and grouting. He has contributed to more than 325 geotechnical projects across Indonesia, Singapore, and Sri Lanka. In addition to his professional work, he has extensive academic experience as a lecturer and trainer in geotechnical engineering and software applications. He has also contributed to the development of the Indonesian National Standard for Geotechnics. Dr. Gouw is an active member of several professional organizations, including the Indonesian Society of Geotechnical Engineering and the International Geosynthetics Society. He has published numerous technical papers in geotechnical engineering.