Weather-driven deterioration processes affecting the performance of embankment slopes

Ross A Stirling,David G Toll,Stephanie Glendinning,Jonathan D Asquith,Paul N Hughes,Peter R Helm,Anil Yildiz

doi:10.1680/jgeot.19.sip.038

Abstract

Deterioration of earthworks and the resultant implications for serviceability and increased occurrence of failures have a significant negative impact on transport networks both in the UK and internationally. There is evidence in the field that deterioration processes are occurring over the life of an asset, comprising cracking and loss of suction. These are weather-driven processes that occur in the absence of increased mechanical loads and can lead to failure many years after construction. To demonstrate the progressive loss in mechanical performance of clay fill due to a purely environmentally driven deterioration process, a programme of unsaturated triaxial testing was carried out. A new mechanism of soil deterioration driven by cyclic wetting and drying is proposed, based on an extensive laboratory and field experimental programme. The underlying cause for this is the micro-structural changes to the soil fabric leading to loss of suction generation capacity. In addition, cracking leads to changes in hydraulic conductivity and the movement of water into and out of the soil. The implications for slope stability assessment include the need for changeability of soil parameters and of the ground model, with changes occurring both seasonally and gradually over time.

Highlights

The deterioration and resultant failures of infrastructure slopes have a significant negative impact on transport networks both in the UK and internationally
This soil was used in the construction of the Bionics full-scale research embankment (Hughes et al, 2009; Glendinning et al, 2014), located at Nafferton in the north east of England, near
The second is that, when assessing the long-term stability of an engineered slope, the result should not be viewed as static: the soil properties are changing gradually due to seasonal cycling as a result of shrinking and swelling; superimposed on this is the response to discrete extreme events, which can cause sudden progression of deterioration, and which may act as failure triggers if a critical magnitude of deterioration is surpassed

Summary

INTRODUCTION

The deterioration and resultant failures of infrastructure slopes have a significant negative impact on transport networks both in the UK and internationally. Specimens were positioned on a low-friction surface during the test; combined with the slow rate of drying, this reduced the potential for the formation of large (.0·5 mm) cracks during water content cycling, micro-scale cracks as observed in Fig. 4 could still develop. This means that each time drying progresses beyond the prior maximum suction value that an asset has been subject to, due to a more extreme drying event than has occurred in its past history, an additional deterioration in performance due to the effect of suction loss can be expected (i.e. for a given water content, lower suction magnitudes are generated). The near-surface zone is affected by exposure to weather-driven deterioration and the resultant development of macro-scale, crack features

Findings

A PROPOSED WEATHER-DRIVEN

CONCLUSIONS