General solutions for consolidation of multilayered soil with a vertical drain system

Pradhan

et al. 2020

Purpose The consolidation behavior of prefabricated vertical drain (PVD)-installed soft deposits mainly depends on the PVD performance. The purpose of this study is to propose a numerical solution for the consolidation of PVD-installed soft soil using the large-strain theory, in which the reduction of discharge capacity of PVD according to depth and time is simultaneously considered. Design/methodology/approach The proposed solution also takes into account the general constitute relationship of soft soil. Subsequently, the proposed solution is applied to analyze and compare with the monitoring data of two cases, one is the experimental test and another is the test embankment in Saga airport. Findings The results show that the reduction of PVD discharge capacity according to depth and time increased the duration required to achieve a certain degree of consolidation. The consolidation rate is more sensitive to the reduction of PVD discharge capacity according to time than that according to the depth. The effects of the reduction of PVD discharge capacity according to depth are more evident when PVD discharge capacity decreases. The predicted results using the proposed numerical solution were validated well with the monitoring data for both cases in verification. Research limitations/implications In this study, the variation of PVD discharge capacity is only considered in one-dimensional consolidation. However, it is challenging to implement a general expression for discharge capacity variation according to time in the two-dimensional numerical solution (two-dimensional plane strain model). This is the motivation for further study. Practical implications A geotechnical engineer could use the proposed numerical solution to predict the consolidation behavior of the drainage-improved soft deposit considering the PVD discharge capacity variation. Originality/value The large-strain consolidation of PVD-installed soft deposits could be predicted well by using the proposed numerical solution considering the PVD discharge capacity variations according to depth and time.

Section: Introductionmentioning

confidence: 99%

Large-strain consolidation analysis of PVD-installed soft soil considering the discharge capacity variation according to depth and time

Pradhan

et al. 2020

“…Prefabricated vertical drains (PVDs) have been widely applied in ground improvement (Hansbo, 1981(Hansbo, , 1997Bergado et al, 1990Bergado et al, , 1991Bergado et al, , 1996Kim and Lee, 1997;Chai et al, 2001;Shen et al, 2005;Ahn et al, 2011;Yune et al, 2013;Hu et al, 2014;Liu et al, 2014;Wu et al, 2015;Zhang et al, 2015;Chen et al, 2016;Zhou et al, 2017;Kim et al, 2018a;Nguyen et al, 2018). PVDs are typically installed using a steel mandrel, which is pushed into the subsoil with static or vibration methods and then withdrawn, leaving the drain in the subsoil.…”

Section: Introductionmentioning

confidence: 99%

An analytical solution for consolidation of PVD-installed deposit considering nonlinear distribution of hydraulic conductivity and compressibility

Kim

2019

Purpose It is well known that the prefabricated vertical drain (PVD) installation process generates a significant soil disturbance around PVD. This disturbed zone significantly affects the rate of settlement and excess pore pressure dissipation. However, the characteristics of these zones were still uncertain and difficult to quantify; there remains large discrepancy among researchers. This study aims to develop a simple analytical solution for radial consolidation analysis of PVD-installed deposit considering mandrel-induced disturbance. Design/methodology/approach The proposed solution takes into account the nonlinear distributions of both horizontal hydraulic conductivity and compressibility toward the drain. The proposed solution was applied to analyze field behavior of test embankment in New South Wales, Australia. Findings Both effects significantly increased the time required to achieve a certain degree of consolidation. The effect of hydraulic conductivity on the consolidation rate was more significant than the effect of compressibility variation. And, the increased compressibility in the soil-disturbed zone due to mandrel installation significantly increased vertical strain of the PVD-improved soil deposit. The predicted results using the proposed analytical solution were in good agreement with the field measurements. Practical implications A geotechnical engineer could use the proposed analytical solution to predict consolidation behavior of drainage-installed ground. Originality/value Consolidation behavior of PVD-installed ground could be reasonably predicted by using the proposed solution with considering variations of both hydraulic conductivity and compressibility due to PVD installation.

Advances in Civil Engineering

“…e consolidation properties of soil can be revealed by this theory. Over the years, based on Barron's axial symmetry consolidation theory, the in-depth study of soil consolidation behavior was carried out from many aspects, such as well resistance and smearing [2][3][4][5], loading changes over time [6][7][8][9][10], nonlinear compression and penetration parameters [11,12,13], negative pressure loading [14,15,16,17], and multi-layer [18,19]. It provides theoretical support for design and calculation of the consolidation method with vertical drains in practical projects.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Large‐Strain Consolidation Behavior of Soil with High Water Content in Consideration of Self‐Weight

Cao

Yang

et al. 2018

Based on the axisymmetric large-strain consolidation (ALSC) model with the void ratio as the variable under equal strain condition, difference schemes of model's equation, initial condition, and boundary condition were given. Taking phosphatic clay in Florida as a research object, the consolidation behaviors of soil with high water content by axisymmetric large-strain theory and one-dimensional large-strain theory were analyzed. e effect of different kinds of consolidation theories and self-weight stress on an average degree of consolidation was evaluated. e development of the void ratio and excess pore water pressure along the soil layer was clarified. e results show that the theoretical value of Terzaghi's consolidation degree is always less than that of ALSC (U s , the average degree of consolidation defined by strain)-vertical drainage in the consolidation process. Terzaghi's solution overestimates the dissipation rate of excess pore water pressure during the earlier consolidation period but underestimates it during the later consolidation period. e degree of consolidation calculated by Hansbo develops faster than ALSC (U p , the average degree of consolidation defined by stress)-radial drainage, but slower than ALSC (U s )-radial drainage. In the ALSC model, U s is always been faster than U p . e effect of self-weight on the consolidation degree of axisymmetric large-strain consolidation theory is relatively small (maximum error is less than 16%), while it can accelerate the consolidation rate of soil in onedimensional large-strain consolidation theory largely. When only the vertical drainage occurs, the consolidation rate in the middle of the soil is obviously lagging the upper and lower parts, while the radial drainage can reduce the void ratio and the excess pore water pressure along the soil layer uniformly and more rapidly.