Reviewed by Frances BriggsNov 18 2025
Japan’s latest borehole mixing innovation helps reduce settlement risks and strengthens the stability of new structures in dense city centers. 
Study: Sustainable approach to urban pile removal through evaluation of innovative circulating mixing for urban infrastructure renewal. Image Credit: JJFarq/Shutterstock.com
Researchers at Shibaura Institute of Technology have introduced a new circulating mixing technique. This method involves pumping backfill material from the base of boreholes, achieving consistent uniformity across the entire depth.
This advancement has the potential to transform urban construction and renovation initiatives, as well as strategies for disaster prevention and reduction. The findings were published in the journal Cleaner Engineering and Technology.
Previous methods of borehole backfilling have been limited by several technical challenges, which complicate infrastructure demolition and renovation projects.
Many countries are now grappling with the simultaneous aging of infrastructure built during periods of swift economic growth.
Japan, in particular, is facing a critical situation, as numerous buildings and constructions built during the post-war economic boom now require dismantling and reconstruction.
The Great East Japan Earthquake of 2011 significantly accelerated this by exposing flaws in constructions that did not comply with current disaster prevention regulations, resulting in a notable increase in demolition operations in metropolitan areas.
When structures are dismantled, the foundation piles must be extracted and categorized as industrial waste. However, traditional backfilling techniques frequently result in an inconsistent allocation of material across the borehole depth.
This technical constraint poses substantial hazards, such as ground settlement, structural inclination of nearby buildings, and displacement of newly constructed foundations.
The essential backfilling procedure used lacks scientific precision and quality assurance procedures.
Now, scientists at Shibaura Institute of Technology in Japan have pioneered a new technique. Their mixing method guarantees consistent backfilling across the entire depth of a borehole. It addresses immediate safety concerns and promotes the long-term sustainability of infrastructure.
The circulating mixing method they developed has undergone verification through a series of tests.
These included model tests, on-site experiments, and sophisticated numerical simulations. The moving particle semi-implicit (MPS) method was employed within a computer-aided engineering (CAE) system. The tests revealed outstanding consistency, indicated by a coefficient of variation of just 0.036.
This is roughly 10x superior to standard soil enhancement methods, which typically have a range of 0.3 to 0.5.
Furthermore, field tests conducted on boreholes with a depth of 15 meters verified that all samples surpassed the intended strength of 1,500 kN/m2. No structurally deficient weak areas were found.
Most significantly, our approach allows engineers to optimize process parameters and improve quality control by employing advanced MPS-CAE computer simulations to predict mixing behavior before construction. Moreover, it addresses Japan's urgent infrastructure renewal needs while promoting sustainability by preventing soil degradation, reducing construction waste, and minimizing the carbon footprint of urban projects.
Shinya Inazumi, Professor, Shibaura Institute of Technology
This method demonstrates considerable utility in the construction of tall buildings on land with pre-existing pile foundations. In these scenarios, inadequately filled boreholes can jeopardize the integrity of new, expensive structures.
The method effectively mitigates ground settlement and structural tilting, which are potential causes of severe failures during earthquakes, thereby resolving significant safety issues in areas susceptible to seismic activity.
Our study establishes a new standard for geotechnical engineering in urban redevelopment with potential worldwide applications, particularly in cities facing aging infrastructure challenges. In densely populated metropolitan areas like Tokyo, New York, or London, where numerous buildings constructed during post-war economic boom periods now require demolition and reconstruction, this technology ensures safe and efficient site preparation.
Shinya Inazumi, Professor, Shibaura Institute of Technology
The integration of engineering methods with numerical simulation in this approach allows the construction sector to move from reactive quality control to forward-thinking process improvement.
This step will improve the efficiency, safety, longevity, and environmental friendliness of urban renewal projects, particularly in areas at high risk of disasters.
Changing geotechnical engineering practices could also help engineering firms and construction businesses ensure clients of construction quality through pre-construction numerical analysis. This, in turn, fosters greater openness and accountability in urban infrastructure projects.
Our innovative method supports sustainable urban development by minimizing construction waste and reducing the carbon footprint associated with material transportation and disposal. It further offers a pathway to improved geotechnical performance in urban infrastructure development, contributing to disaster resilience, protecting lives and property investments.
Shinya Inazumi, Professor, Shibaura Institute of Technology
Journal Reference
Inazumi, S., et al. (2025) Sustainable approach to urban pile removal through evaluation of innovative circulating mixing for urban infrastructure renewal. Cleaner Engineering and Technology. DOI:10.1016/j.clet.2025.101103.