Deeper Foundation Treatment Increases Uneven Settlement in Coastal Soil Model

A finite-element study of a coastal soft-soil foundation found that increasing the depth of dynamic compaction replacement from 3.0 to 6.0 m changed settlement within the treated area only slightly, while settlement in adjacent untreated ground increased from 0.252 to 0.350 m. The modeled differential settlement rose from 0.052 to 0.132 m, and the differential settlement ratio increased from 20.8% to 37.8%. The results indicate that greater treatment depth can create a larger deformation mismatch between improved and untreated ground, although the authors caution that the findings have not been validated as a field design recommendation.

The investigation modeled the Huanhu Road section in Dongfang City using a two-dimensional axisymmetric finite-element approach. The dynamic compaction replacement region was represented as an equivalent linear-elastic improved zone within a total-stress framework. This numerical representation allowed the researchers to assess how different treatment depths influenced settlement in the treated and untreated areas, differential settlement between them, and the distribution of stress and strain through the soil profile. The study examined model-based behavior rather than measurements from a construction site.

As the treatment depth increased from 3.0 to 6.0 m, the strongest numerical change occurred outside the treated region. Settlement in the adjacent untreated area increased by 0.098 m, whereas settlement in the treated area changed only slightly. The widening difference between the two areas was associated in the stress- and strain-response analyses with vertical stress redistribution and an increasing mismatch in compressive deformation between treated and untreated ground. Thus, deeper replacement was associated in the model with greater unevenness at the boundary between the improved zone and the surrounding soil.

Among the modeled depths, cases of 3.5–4.0 m showed a relatively balanced response between settlement control and deformation compatibility within the investigated range. The researchers also examined two prescribed groundwater-depth situations as auxiliary sensitivity checks for the adopted density-based representation of improved ground. These checks did not turn the model into a field-verified design method; the authors explicitly described the 3.5–4.0 m range as a model-based reference. The study’s scope is therefore limited to a numerical assessment of treatment-depth effects for the modeled coastal soft-soil foundation, and its conclusions should not be read as a universally applicable construction specification.

Subject of Research: Finite-element analysis of treatment-depth effects on settlement compatibility in dynamic compaction replacement foundations

Article Title: Treatment depth effects on settlement and deformation compatibility of dynamic compaction replacement foundations in coastal soft soil

Article References: Hong, K., Hu, J., Zhao, S. J., Xiao, M., Yang, L., & Zhou, J. H. (2026). Treatment depth effects on settlement and deformation compatibility of dynamic compaction replacement foundations in coastal soft soil. Scientific Reports. https://doi.org/10.1038/s41598-026-76337-8

Image Credits: AI Generated

DOI: 10.1038/s41598-026-76337-8

Keywords: coastal soft soil, dynamic compaction replacement, foundation engineering, differential settlement, finite-element modeling, ground improvement, stress redistribution, deformation compatibility, geotechnical engineering, Treatment, depth, effects