Critical Review and Finite Element Analysis of Smear Zone in Soft Clay Improved by Prefabricated Vertical Drains

Abstract

Structures built on soft soils are often affected by settlement problems. Over the past decades, one of the best methods to accelerate the consolidation process is preloading technique with pre-fabricated vertical drains. However, while installing these drains the soil around the drain gets disturbed, which in turn reduces the permeability of soil in radial direction. This disturbance is known to be smear effect and the region of this disturbed soil is the smear zone. This paper presents a state-art-of-the review on analytical, laboratory, field and numerical studies on the smear zone behaviour. Pore pressure variation, water content and permeability in the smear and undisturbed zone are compared. Finite element modeling carried out for better understanding of consolidation behaviour of soft clay improved with PVD is also presented in this paper. The effect of smear is considered in the finite element model and the results from the finite element model are compared with laboratory test results. The soil behaviour is modelled using the modified cam-clay model and the ABAQUS finite element application is used for numerical modelling. Based on the results, the time-settlement data and pore pressure dissipation predicted by the numerical model were comparable with the laboratory results reported in the literature with a variation of upto 10%. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.