ABSTRACT

VERTICAL BARRIERS IN SOILS FOR POLLUTIONS CONTAINMENT
ASCE –1987

Christopher Ryan

Editors Comments:
This is one of the most frequently referenced and widely read technical papers dealing with groundwater barriers. The paper concentrates on applications for soil-bentonite and cement-bentonite slurry walls including discussions on construction techniques, design guidance, and performance. Other techniques discussed include deep soil mixing, composite slurry walls, and grouting. Combinations of liners, vertical barriers and drains are discussed as elements of landfill containments. A highlight is a case study of leachate incompatibility with bentonite. Paper includes extensive list of references.

Original Abstract:
“Vertical barriers have evolved over the past fifteen years into a technique that is widely applied to restrict the underground movement of liquid wastes and polluted groundwater. Most applications are slurry cut-off walls, although there are several other techniques such as composite slurry walls and soil-mixing walls which show promise. Vertical barriers are used in applications both for new sites and for remediation of polluted sites. In both cases, the vertical barriers may be only one part of containment systems such as liners, or with remedial techniques such as leachate collection and treatment to provide a complete system.

Experience on a number of projects has provided data that act as a guide for the design of slurry cut-off walls. A key parameter is the quantity of additional dry bentonite added to the backfill blend. Once the blend has been designed to have an acceptable permeability to water, its compatibility with the expected leachate must be checked. For most leachates, a suitable soil-bentonite backfill blend can be designed.

A case study is presented that describes a project where bentonite was determined to be unsuitable as an additive. Attapulgite was substituted for the bentonite and the project successfully constructed.”