Soil mix technology for land remediation: Recent innovations

The past 15 years have seen increasing applications of soil mix technology in land remediation, mainly in stabilisation/solidification treatments and the construction of low-permeability cut-off walls and permeable reactive barriers; clear evidence of the versatility of the technology and its wide-ranging applications. This paper provides an overview of some of the recent innovations of soil mix technology in land remediation covering equipment developments and applications, including systems for rectangular panels and trenching systems, treatments, such as chemical oxidation, and additives, such as modified clays, zeolites and reactive magnesia. The paper also provides case studies for such innovations. The paper concludes with an overview of an on-going research and development project SMiRT (Soil Mix Remediation Technology) which will involve field trials on a contaminated site and will employ some of the innovations discussed in the paper. The range of significant advantages that soil mix technology now offers compared to other remediation techniques is likely to place this remediation method at the forefront of remedial options for future brownfield projects.

Pipeline uplift response in thawed sandy backfills: Preliminary findings

Offshore and onshore buried pipelines under high operating temperature and pressures may lead to upheaval buckling (UHB) if sufficient soil cover is not present to prevent the upward movement of the pipeline. In regions where seasonal changes involve ground soil undergoing freezing-thawing cycles, the uplift resistance from soil cover may be minimum when the soil is undergoing thawing. This paper presents the results from 2 directly-comparable minidrum centrifuge tests conducted at the Schofield Centre, University of Cambridge, to investigate the difference in uplift resistance responses between fully-saturated and thawed sandy backfill conditions. Both tests were conducted drained at 30g using an 8.6 mm diameter aluminium model pipe, corresponding to a prototype pipe diameter of 258 mm. The soil cover/pipe diameter ratio, H/D, was kept at 1. Fraction E fine silica sand was used as the backfill. Preliminary experimental results indicated that the ultimate uplift resistance of a thawing sand backfill to be lower than that of a fully saturated sand backfill. This suggests that in regions where backfill soil undergoes freeze-thaw cycles, the thawing backfill may be more critical than fully saturated backfill for uplift resistance. The 2-dimensional displacement field during the experiment was accurately measured and analysed using the Particle Image Velocimetry technique. Copyright © 2011 by the International Society of Offshore and Polar Engineers (ISOPE).