Advanced Geotechnical Solutions for Soft Soils: FEM Analysis and Hybrid Reinforcement in the Semarang-Demak Toll Road Project

bamboo embankment finite element geotextile laboratory test prefabricated vertical drain (PVD) soft soil

Authors

  • Andi Kurnia Setiadi Kartawiria
    andikartawiria@yahoo.com
    Universiti Teknologi Malaysia, Indonesia https://orcid.org/0009-0001-3865-9586
  • Samira Albati Binti Kamaruddin Department of Engineering and Technology, Razak Faculty of Technology and Informatics, Universiti Teknologi Malaysia, Sultan Yahya Petra Road (Semarak Road), 54100, Kuala Lumpur, Malaysia
  • Ramli Bin Nazir Centre of Tropical Geoengineering, Universiti Teknologi Malaysia, 81300, Johor Bahru, , Malaysia
  • Idrus Muhamad Alatas Board of Research and Community Service, Institut Sains dan Teknologi Nasional, Moh. Kahfi II, Jagakarsa – Jakarta Selatan Road, 12640, Indonesia
  • Agus Himawan PT. LAPI ITB, B Building – Institut Teknologi Bandung, Jalan Ganesa 10 Bandung 40132, , Indonesia
  • Pasca Hartasurya PT. LAPI ITB, B Building – Institut Teknologi Bandung, Jalan Ganesa 10 Bandung 40132, , Indonesia
  • Iswandi Imran Structural Engineering Research Group, Faculty of Civil and Environmental Engineering, Institut Teknologi Bandung, Jalan Ganesa 10 Bandung 40132, Indonesia
  • Reguel Mikhail School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Ave, Singapore 639798,, Singapore
  • Yusrizal Kurniawan BBPJN Jawa Tengah – D.I. Yogyakarta, Direktorat Jenderal Bina Marga Kementerian PU, Soekarno - Hatta KM. 26 Karangjati Road, Kabupaten Semarang 50552, Jawa Tengah, Indonesia
  • Prasetyo Arief Wibowo BBPJN Jawa Tengah – D.I. Yogyakarta, Direktorat Jenderal Bina Marga Kementerian PU, Soekarno - Hatta KM. 26 Karangjati Road, Kabupaten Semarang 50552, Jawa Tengah, , Indonesia
  • Ardita Elias Manurung BBPJN Jawa Tengah – D.I. Yogyakarta, Direktorat Jenderal Bina Marga Kementerian PU, Soekarno - Hatta KM. 26 Karangjati Road, Kabupaten Semarang 50552, Jawa Tengah, , Indonesia
  • Yusuf Maharani Divisi Perencanaan Strategis, Engineering dan Teknologi, PT. Pembangunan Perumahan (Persero), TB Simatupang No. 57 Road, Pasar Rebo, Jakarta 13760 , Indonesia
  • Yusmar Anggadinata PT. LAPI ITB, B Building – Institut Teknologi Bandung, Jalan Ganesa 10 Bandung 40132, , Indonesia
  • Muhammad Hariyadi Setiawan PT. LAPI ITB, B Building – Institut Teknologi Bandung, Jalan Ganesa 10 Bandung 40132, Indonesia
  • Siswantono Siswantono PT. Pembangunan Perumahan Semarang Demak, Jalan Raya Semarang Demak KM 10, Demak 59563, Jawa Tengah , Indonesia
  • Sholeh Hendra Wibawa Divisi Infrastruktur 1, PT. Pembangunan Perumahan (Persero), TB Simatupang No. 57 Road, Pasar Rebo, Jakarta 13760 , Indonesia
  • Rakhma Nur Editia Divisi Infrastruktur 1, PT. Pembangunan Perumahan (Persero), TB Simatupang No. 57 Road, Pasar Rebo, Jakarta 13760 , Indonesia
August 1, 2025
September 23, 2025

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This paper presents an analysis of the data collected from the full-scale trial embankment implemented in the Semarang-Demak Toll Road project, part of a national strategic project in Central Java, Indonesia. The project integrates a sea dike with a road embankment. The main challenge of the project lies in constructing the embankment on soft soil layers up to 40 meters thick. The road embankment is designed to reach a height of 6 meters above Mean Sea Level (MSL) or 8 meters above the average seabed level. In the absence of ground improvement techniques—such as bamboo mattress, prefabricated vertical drains (PVD), or high-strength geotextiles—very soft soil with an undrained shear strength of approximately 6.5 kPa can support only a critical embankment height of about 3 meters. A hybrid reinforcement that combines bamboo mattresses, high-strength woven geotextile, PVD and staged embankment construction is selected to solve the shear strength and settlement problem. Mattress acts as platform and designed to deform as much as the soft-soil to spread initial embankment load uniformly and increase bearing capacity, PVD accelerates consolidation, and high-strength woven geotextile provides tension capacity. To achieve a load ratio of 1.3 in accordance with SNI 8460-2017, a 13.5-meter soil preloading needs to be constructed. Several monitoring systems were installed to monitor the behavior of the entire embankment system. Complementary investigations, including CPT, CPTu, and Deep Boring, were conducted. Finite element analysis (FEA) was then performed, revealing improved performance, achieving safety factors of 1.25 during construction and 1.55 long-term.