Date of Award

Fall 1995

Document Type

Thesis

Degree Name

Master of Science in Environmental Science - (M.S.)

Department

Chemical Engineering, Chemistry and Environmental Science

First Advisor

John R. Schuring

Second Advisor

Richard B. Trattner

Third Advisor

Paul C. Chan

Abstract

This study investigates volume changes in fine-grained soil formations and their effect on pneumatically induced fractures. Pneumatic fracturing is an enhancement technology for in situ remediation of hazardous waste sites, which increases the formation permeability by creating fractures. A number of formation properties and environmental conditions which affect fracture aperture were identified in this study.

Laboratory experiments were performed with control devices to investigate idealized fracture flow under linear and radial flow geometries. These tests exhibited cubic law behavior, and gas compressibility was seen as a measurable effect. A horizontal infiltrometer device was successfully developed to induce and control volume changes in natural soils with an artificial discrete fracture by moisture addition and removal. Tests performed with Woodbury clay showed that changes in fracture aperture were reversible, and that porous media flow was instrumental in aperture behavior.

A new concept of a "secondary active zone" is introduced which describes the zone of increased activity along the fracture boundary soils. A classification model is presented for assessing volume change potential of fine-grained formations based on their physical, chemical, and mineralogical properties. The model also recommends treatment alternatives for pneumatically fractured sites including hydraulic control. chemical stabilization, and fracture propping.

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