Design procedure for vertical drains considering a linear variation of lateral permeability within the smear zone

Abstract

PLEASE NOTE: This is the FINAL COPY after all revisions are incorporated. 2 A DESIGN PROCEDURE FOR VERTICAL DRAINS CONSIDERING A LINEAR VARIATION OF LATERAL PERMEABILITY WITHIN THE SMEAR ZONECholachat Rujikiatkamjorn and Buddhima Indraratna AbstractA system of vertical drains with surcharge preloading is an effective method for promoting radial drainage and accelerated soil consolidation. This study presents a procedure for the design of vertical drains significantly extending the previous technique proposed by the Authors to include; (i) a linear reduction of lateral permeability in the smear zone, (ii) the effect of overlapping smear zones in a closely spaced drain network, and (iii) the gain in undrained shear strength due to consolidation. Design examples are provided for both single stage and multi-stage embankment construction demonstrating the convenient use of the proposed solutions in practical situations.

An analytical solution for consolidation with vertical drains under multi-ramp loading

“…On the other hand, the loading rate that can be applied in practice is controlled by the stability of surcharge fills (Ladd, 1991;Indraratna et al, 2005c;Rujikiatkamjorn & Indraratna, 2009). Specifically, it depends on an increase in shear strength due to consolidation.…”

“…The effect of consolidation on shear strength should not be ignored in the determination of a safe and cost-effective loading rate. To account for this effect in preliminary design of vertical drains and surcharge fills, the assessment of the stability of surcharge fills is usually carried out based on the gain in undrained strength of soil by Δs u = αΔσ′ v = ασ M U S (Li & Rowe, 2001;Bergado et al, 2002;Rujikiatkamjorn & Indraratna, 2009;Sinha et al, 2009;Chai & Duy, 2013), where α is the undrained strength gain ratio, which is almost constant for a given normally consolidated soil (Ladd & Foott, 1974;Mesri, 1989;Wang et al, 2008); Δσ′ v is the increase in effective vertical stress; and σ M is the maximum increase in total stress due to surcharge loading. Since the value of U S at a given point in time increases with an increase in loading rate (as is shown by Fig.…”

Analyzing consolidation data to predict smear zone characteristics induced by vertical drain installation for soft soil improvement

“…Thus, according to the existing literature, wide ranges are proposed for the smear zone extent and permeability ratio and there is no definite method to predict the extent of smear zone and its permeability precisely to be used by practising engineers. In geotechnical practice, the Hansbo (1981), Chai and Miura (1999) Two zones Constant - Walker and Indraratna (2006) Two zones Parabolic - Rujikiatkamjorn and Indraratna (2009) Two zones Linear - Madhav et al (1993) extent and characteristics of smear zone are estimated from the available parameter ranges which are very diverse (Fig. 2).…”

Vertical-drain consolidation using stone columns: An analytical solution with an impeded drainage boundary under multi-ramp loading

“…Vertical prefabricated drains or sand/stone columns are commonly utilised to accelerate the consolidation of soft soils under preloading (Almeida et al, 2015;Artidteang et al, 2011;Cascone and Biondi, 2013;Chai et al, 2010;Indraratna et al, 2010;Jang and Chung, 2014;Karunaratne, 2011;Li and Rowe, 2001;Lo et al, 2008Lo et al, , 2010Rowe and Li, 2005;Rowe and Taechakumthorn, 2008;Saowapakpiboon et al, 2009Saowapakpiboon et al, , 2010Shen et al, 2005;Suleiman et al, 2014;Van Helden et al, 2008;Voottipruex et al, 2014;Xue et al, 2014). Analytical solutions predicting the extent of consolidation in preloading play an important role in the preliminary design of vertical drains (AbuelNaga et al, 2012;Bari and Shahin, 2014;Basu and Prezzi, 2009;Chung et al, 2014;Rujikiatkamjorn and Indraratna, 2009;Sinha et al, 2009). Since the pioneering work of Barron (1948), the challenge of deriving an analytical solution for cylindrical unit-cell consolidation with a vertical drain has captured the attention of the ground improvement community.…”