Vol.:(0123456789) Arabian Journal of Geosciences (2025) 18:134 https://doi.org/10.1007/s12517-025-12278-2 ORIGINAL PAPER Improving soft soil using high vacuum densification method in the laboratory Ripon Chandra Malo 1  · Mehedi Ahmed Ansary 1 Received: 11 November 2024 / Accepted: 23 May 2025 © Saudi Society for Geosciences and Springer Nature Switzerland AG 2025 Abstract This study presents a controlled laboratory evaluation of the high vacuum densification method (HVDM) for improving extremely soft soil using a 1 g physical model. Following several trials on the physical model, the experiment was carried out using samples obtained from the field site, where HVDM was applied to improve the soil properties. The successful application of HVDM within the physical model resulted in achieving 94% relative compaction, accompanied by significant enhancements in soil strength: specifically, a 37% increase in unconfined compressive strength and a 38% rise in triaxial deviator strength, as well as a significant improvement in cohesion and angle of internal friction relative to untreated condi- tions. Also, the experimental observations, including the pore pressure response, settlement behavior, and visual evidence, all indicate a significant enhancement in soil stiffness following HVDM treatment, accompanied by rapid consolidation and increased density. The application of HVDM enables the achievement of the desired soil stiffness within the shortest possible timeframe. Keywords HVDM · Ground improvement · Soft soil · Physical model · Stiffness Introduction The fast urbanization, population increase, many infrastruc- tural expansions, and the always rising economic activity in industrialized nations like Bangladesh have all contributed to a decline in the amount of usable land available (Hasan et al. 2017). Many times, the best option for finding usable ground for construction has been to reclaim land from the coast- line. Bangladesh has a large population and a coastline that makes up 32% of the country. In numerous coastal areas of Bangladesh (Hore et al. 2019; Alam et al. 2020), the soil is extremely soft to soft and possesses inadequate geotechnical characteristics, including high compressibility, inadequate bearing capacity, and a lengthy consolidation period (Nguy- enn et al. 2021). In the field of geotechnical engineering, working with soft soils has long been a source of frustration. It is required to remediate soft soils before using them for engineering purposes. It is possible to construct on challeng- ing soils by using the right ground improvement techniques. The most creative subfield in geotechnical engineering is ground improvement. To make it possible to use areas with poor subsurface conditions, ground enhancement involves altering the soil in the foundation by changing its properties (such as density, swelling, shear strength, bearing capacity) (Puppala and Pedarla 2017). Because of this, construction costs are reduced, and implementation times are shortened (Munfakh 1997). It is possible to enhance the engineering and mechanical characteristics of soft soils using a variety of methods. Nowadays, many different methods are employed to improve soil quality (Evans et al. 2021). These include sand drains, granular piles, PVD, deep mixing, reinforced soil foundations, dynamic compaction, rammed aggregate piers, HVDM, and many more. Among these strategies, high vacuum densification method (HVDM) stands out as a highly beneficial approach to improving soft soil. It is a novel ground enhancement method that is cost-effective and time-efficient in treating saturated soft soil (Yin et al. 2013). In order to enhance saturated, cohesive soil, HVDM com- bines the dynamic compaction and vacuum consolidation Responsible Editor: Zeynal Abiddin Erguler * Mehedi Ahmed Ansary ansary@ce.buet.ac.bd Ripon Chandra Malo riponce.buet@gmail.com 1 Department of Civil Engineering, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh