Viscoelastic Parameter Prediction of Multi-Layered Coarse-Grained Soil with Consideration of Interface-Layer Effect

Round 1

Reviewer 1 Report

A new mathmatical method for the prediction of viscoelastic behaviour of multi-layered coarse-grained soil including pebbles is proposed. It is plausible that the topic is of big interest for the engineering of foundations.The state of the art is well presented.

Multi-layer structures are composed of different one-layer heights, boundaries between different layers are described by interface-layers. The deduction of the method is done step by step, the approach seems to be well structured. It is based on elastic parameters of the included solid particles and gas phase, each of the of the one-layers and of the interface-layers. Herein, mechanical properties of the pebbels are governed by their surfaces. This effect is considered via a shape factor applied to the idealised shperic pebbles in the model.

Viscoelastic parameters are derived using the "ealstic-viscoelastic corresponding principle". Unfortunately, it becomes not fully clear what the "ealstic-viscoelastic corresponding principle" is and how viscoelastic parameters are determined from the elastic parameters. A further description or references would be helpful. The parameters are used in a Burgers model.

In line 256 it is not clear what heights the layers have.

However, the method is succesfully experimentally verified in triaxial compression creep tests for a a constant load period of two hours. It shopuld be asessed in how far this time period is relevant for practical applications. Different sand-clay matrices are considered. Fitting shape factors are quantified.

It is recommended to check the manuscript for typing errors and english language.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper proposes a procedure to predict viscoelastic parameters of multi-layered coarse-grained soil mixtures. The paper is well-written but needs the following revisions:

The following references can be added to the literature to indicate the applications of CGS and mixed soils in improving shallow and piled foundations:

- Effect of Gravel Layer on the Behavior of Piled Raft Foundations, Geo-Shanghai 2014, Advances in Soil Dynamics and Foundation Engineering, ASCE GSP 240, 373-382.

- Large-Scale Experimental Investigation of Strength Properties of Composite Clay. Geotech Geol Eng 37, 5061–5075, 2019.

- Behavior of eccentrically loaded shallow foundations resting on composite soils, Journal of Building Engineering, 23, 220-230, 2019.

Section 2: please add relevant references in appropriate places to support the logic and practicality of methodology.

Figure 9: please describe what each picture indicates.

Figure 12: In some cases, the “%” sign is missing on the graph.

The results that were obtained in section 3 and summarized in conclusions are reasonable; however, a better description of the usefulness and application of these results must be presented. For example, in the design of a pavement or embankment, what are the benefits and limitations of using two-layer system compared to those of a three-layer system?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf