Cracking in desiccating soils

Alberto Ledesma,P Delage,S Ghabezloo,J.-M Pereira,Y.-J Cui,A.-M Tang

doi:10.1051/e3sconf/20160903005

Abstract

Soil shrinkage is produced typically under desiccating conditions. Eventually shrinkage may generate cracks in the soil mass, a phenomenon that is being studied by several researchers, because its prediction is far from being a routine in Soil Mechanics. Within this context, Unsaturated Soil Mechanics provides a promising framework to understand the mechanisms involved. In addition to that, physical modelling of desiccating soils constitutes a good tool to explore the nature of this problem. In this paper, a description of the processes involved in desiccating soils is presented first. There is a debate in the Soil Mechanics community about the conditions leading to the initiation of a crack and some of those issues are addressed in the paper. Then, two physical modelling strategies to study desiccating soils are briefly described: a laboratory environmental chamber and a field controlled test. The chamber was able to reproduce drying and wetting cycles by controlling the relative humidity of the environment that affected the moisture conditions of a soil tray. Temperature was a controlled variable as well. The second experiment refers to a field test, exposing a large soil tray to standard environmental actions in the field, that is, cycles of temperature, solar radiation, relative humidity, rain, wind, etc. In this case, actions cannot be controlled, but they can be measured. An effort was devoted to measure internal variables in the soil mass, mainly temperature, suction and water content. Additionally changes of weight were recorded as well. In essence the paper gives a general overview of the mechanisms involved in soil cracking and the physical modelling procedures employed to analyse this phenomenon in practice.

Highlights

Shrinkage of soils due to desiccation is a common process in natural dry environments
This paper presents first an analysis of the problem by using an Unsaturated Soil Mechanics approach
The second part of the paper includes the description of two physical models that have been used in this case: an environmental chamber, controlling relative humidity and temperature over a monitored soil tray, and a field experiment where a large soil container is subjected to atmospheric actions, i.e., solar radiation, temperature, wind, relative humidity changes, rain, etc

Summary

Introduction

Shrinkage of soils due to desiccation is a common process in natural dry environments. The second part of the paper includes the description of two physical models that have been used in this case: an environmental chamber, controlling relative humidity and temperature over a monitored soil tray, and a field experiment where a large soil container is subjected to atmospheric actions, i.e., solar radiation, temperature, wind, relative humidity changes, rain, etc. Both tests are important to understand the mechanisms involved in the initiation and propagation of the cracks. Both experiments are compared and the advantages and disadvantages of each test are briefly discussed

Soil drying

Crack initiation

Crack propagation

Physical modelling

Findings

Conclusions