Effect of external hydraulic head on swelling of unsaturated clay

Shay Nachum,Sam Frydman,Mark Talesnick,R Cardoso,C Jommi,E Romero

doi:10.1051/e3sconf/202019503035

Shay Nachum, Sam Frydman + Show 4 more

Open Access

https://doi.org/10.1051/e3sconf/202019503035

Copy DOI

Abstract

Laboratory testing of the one-dimensional swell of soil (usually unsaturated clay) is generally performed according to ASTM standard D4546. The standard procedure requires that “the specimen is inundated with test water and the one-dimensional wetting-induced swell or collapse strain is measured”. This procedure undoubtedly provides an upper limit to the swell which may be expected under field conditions, and may be relevant to cases in which low lying areas are expected to be inundated as a result of a wetting episode. However, in other cases, wetting of the soil may result from less extreme conditions - for example absorption of water from underlying, wetted layers, or soaking of the lower portion of a swelling layer and resultant upward wetting due to suction forces. The present paper describes a laboratory investigation of the effect of external hydraulic head on swell. The results demonstrate the importance of applying test conditions consistent with those expected in the field situation.

Highlights

Swelling or shrinking of unsaturated clay is a major cause of damage to structures and infrastructures worldwide
Wang [2] referred to data indicating a more updated estimate of $9 billion in yearly damage due to expansive soils, with about 50% related to highways and streets
The influence of external hydraulic head may be of significance when estimating expected damage to roads, structures and infrastructure as a result of different wetting conditions

Summary

Introduction

Swelling or shrinking of unsaturated clay is a major cause of damage to structures and infrastructures worldwide. The tests are commonly performed according to ASTM standard D4546 [5] which requires that "the specimen is inundated with test water and the onedimensional wetting-induced swell or collapse strain is measured" This procedure undoubtedly provides an upper limit to the swell which may be expected under field conditions, and may be relevant to cases in which low lying areas are expected to be inundated as a result of a wetting episode. Swelling tests have been performed in a standard consolidometer, by wetting from the base of the specimen while applying different heads as well as by inundating the specimen in accordance with the ASTM standard These tests indicate the significance of external hydraulic head on the resulting swell, and provide clues as to the interaction between soil structure and the flow of water through unsaturated, swelling soil

The soil tested and testing procedure

Results

Conclusions