Discussion: Observational techniques by curve fitting for predicting radial consolidation settlement

Use of vertical drains forms an important and effective feature of ground improvement projects in general. In their paper, the authors have introduced two techniques for analysing the radial consolidation process, namely, (a) use of computer programs with iterative optimisation algorithms (proposed method 1) and (b) numerical integration technique (proposed method 2). In this context, the discusser wishes to elaborate on three issues to gain more clarity.

The Asaoka’s method is generally accepted worldwide as an ‘observational procedure’ due to its inherent features so that it can be called so. The rectangular hyperbola method (RH method), to some extent, could be considered as ‘semi-observational procedure’. The authors call their proposed methods as observational techniques, which is misleading. These two methods are computer based, not easy to be adapted by everyone in the absence of knowledge of modern software, iterative and not user friendly unlike the Asaoka’s method or RH method. Then, what is the rationale behind calling them as observational techniques?

The documented geotechnical engineering literature indicates some more methods of analysing the radial consolidation test data, namely, square root of time-fitting method, log₁₀ (d_e²/t) Vs. U_r curves method, one-point method (Sridharan et al., 1996), and log t fitting method (Prakash et al., 2011), which the authors have not cited in the text. Being very simple, one-point method is often considered as user friendly approach. All these methods have been validated through extensive laboratory test data. Both log₁₀ (d_e²/t) Vs. U_r curves method (which can even be computerised) and one-point method have been observed to yield the coefficients of radial consolidation (c_r) very close to their ‘true values’ for the soils under study under the applied effective stress. However, the discusser wishes to submit that the four approaches mentioned above have not been validated with field data.

Table 1 of the paper under discussion presents the values of c_r at six depths. This table presents same values of c_r at all depths obtained by the three methods – proposed method 1 (c_r = 0.82 + 0.07 m²/yr), proposed method 2 (c_r = 0.76 + 0.05 m²/yr) and Asaoka method (c_r = 0.83 + 0.11 m²/yr). Are these the values actually obtained or is there any typographical error?

A response to this discussion can be found at Koslanant S, Sakulsaksri C, Boonyong C and Tanseng P (2025) Response to discussion: Observational techniques by curve fitting for predicting radial consolidation settlement. Proceedings of the Institution of Civil Engineers – Ground Improvement, Link to Response to discussion: observational techniques by curve fitting for predicting radial consolidation settlementLink to the cited article.