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Measurements and Assessment of desiccation Cracks Integrity in Soils with the Application of Remedial Solutions

Final Report Summary - RISMAC (Measurements and Assessment of desiccation Cracks Integrity in Soils with the Application of Remedial Solutions)

Objective: The aim of the project is to advance and improve existing non-destructive scanning techniques for detection of desiccation cracks in the soil mass and to develop new remedial measures for cracked soils. The proposal contemplates the validation of geophysical resistance measurements to detect the presence of desiccation cracks networks in the global soil mass. To date, no experimental technique is capable of performing such studies. Considering that this will be a very valuable tool for industry and other end-users to asses the global integrity of earth-works (such as embankments), it is evident that there is an urgent need to fill this gap. It is also important to bear in mind that the situation will worsen in the near future as the underlying assumption of intact soils (when evaluating their hydraulic conductivity and global stability) becomes even less accurate as a consequence of climate change. Therefore, an experimental technique that is able to quantify the degree of heterogeneities in the soil mass (induce by the presence of desiccation cracks) will be unquestionably necessary. The aim of this project does not stop in detecting the problem but also in proposing novel solutions (based on polymers and grouts) that will contribute to overcome the problems of the current remedial techniques ainly based on the use of lime and cement. In the last few years it has been a considerable advance in the development of new polymers and grouts, which can be very suitable for its application as remedial solutions (and tracers) for cracked soils.

Description of the work performed since the beginning of the project

Phase one:
- Investigation of the electrical and physical properties of remedial materials based on the mixture of nano-composites soils,
- Investigation of the cracking behaviour of drying soils using 2-D laser scanner,
- Digital and numerical investigation of soil cracking,
- Investigation of the soil deformation using 2-D laser scanner and digital photography,
- Investigation of the effect of cracking on earthen embankment subjected to flooding,
- Investigation of the electrical and physical properties of drying “Galston” clay,
- Investigation of the potential use of structured light scanner for crack pattern observation,
- Investigation of the cracking potential of different soil mixtures,
- Investigation of other soil phenomena associated with drying such as: shrinkage and curling.

Phase two:
- Implementation of remedial engineered materials on cracked soil,
- Investigation of the response of remedial materials to wetting-drying cycles,
- Investigation of the influence of microstructure on the electrical properties of soils,
- Investigation of the use of ERT for desiccation cracking detection on the full scale flood embankment,
- Numerical modelling of the response of ERT to complex cracking geometries in soils,
- Investigation of the use of 2-D laser scanner for precise observation of soil curling,
- Investigation of the use of 2-D laser scanner for precise measurement of volume change in drying soils,
- Investigation of different image analysis techniques for soil cracking development during drying.

Main results achieved
Various mixtures of the nano-composite soils to be used as remedial material for cracked soils were tested through extensive experimental campaign. One sample was identified as the most promising and was used on the cracked soil model subjected to wetting and drying cycles. A new miniature 4-electrode device was successfully used to observe the microstructure influence on electrical properties during soil. A 2-D laser scanner was successfully used to precisely monitor soil surface curling. Additionally, the use of 2-D laser scanner for precise touchless volume measurements has been successfully explored. A comparison of different image analysis methods for desiccation cracking analysis was carried out showing the advantages of the 2-D laser scanner. The behavior of a scaled earth embankment subjected to controlled environmental actions has been investigated using numerical analysis showing a good agreement between the laboratory measurements and the model.

Expected final results and their potential impact and use (including the socio-economic impact and the wider societal implications of the project so far)

It is expected that the new remedial material will be used in the future for repairs of earth structures. As it is stated in the project description it could be used as remedial solution for cracked soils, but not limited to this application. The composites used in the project are believed to strengthen the mechanical properties which can be a benefit in other applications where the soil is used.
In addition to that, better understanding of the relationship between electrical conductivity of the soil and moisture content/suction, will help monitor earthen structures using non-invasive geophysical techniques.
Future project outcomes should be ready to transfer it to industry; local authorities and environment agencies, benefiting the society as a whole and populations.

The project logo has been designed and is attached as file logo1