Pore pressure based method to quantify smear around a vertical drain

Abstract

Radial consolidation testing of Ballina clay (New South Wales, Australia) was carried out using a large-scale consolidometer 650 mm in diameter. In this study, the characteristics of the smear zone were evaluated on the basis of hydraulic gradient changes derived from the measured excess pore pressure data in the radial direction. The extent of the smear zone determined using this technique is compared with past approaches, where the variations in water content and lateral permeability were adopted to evaluate smear. The approach proposed herein based on the change of hydraulic gradient coincides with the previous two methods, and the smear zone could be established at almost 2·5 times the effective mandrel diameter. A good agreement is also found between the theoretical radial consolidation predictions, after incorporating the smear zone characteristics and the measured time-settlement curve. The proposed method for the determination of smear zone extent can be carried out during consolidation with minimum disturbance to soil, provided a sufficient number of pore pressure transducers are installed. It also eliminates the need for a number of soil samples and high-quality soil sampling technique after the installation of the drain. Radial consolidation testing of Ballina clay (New South Wales, Australia) was carried out using a large-scale consolidometer 650 mm in diameter. In this study, the characteristics of the smear zone were evaluated on the basis of hydraulic gradient changes derived from the measured excess pore pressure data in the radial direction. The extent of the smear zone determined using this technique is compared with past approaches, where the variations in water content and lateral permeability were adopted to evaluate smear. The approach proposed herein based on the change of hydraulic gradient coincides with the previous two methods, and the smear zone could be established at almost 2·5 times the effective mandrel diameter. A good agreement is also found between the theoretical radial consolidation predictions, after incorporating the smear zone characteristics and the measured time-settlement curve. The proposed method for the determination of smear zone extent can be carried out during consolidation with minimum disturbance to soil, provided a sufficient number of pore pressure transducers are installed. It also eliminates the need for a number of soil samples and high-quality soil sampling technique after the installation of the drain.

Simultaneous stabilization of Pb and improvement of soil strength using nZVI

“…The slurry and pre-consolidation method was employed to prepare the soil samples (Choudhary et al, 2016). Firstly, the soil was first cut into small chunks and immersed in distilled water for two days, after which the soil fractions were passed through a No.…”

Investigation of Smear Zone Around PVD Mandrel Using Image-Based Analysis

“…Bergado et al [11] and Sharma and Xio [23] conducted model tests in large diameter cell and reported that the radius of the smear zone is two times the mandrel radius and four times the radius of the drain, and average permeability in the smear zone is 1.3 times smaller than in the undisturbed zone, respectively. Choudhary et al [24] proposed smear zone extent as 2.5 times mandrel diameter, determined graphically using excess pore pressure data.…”