Document Type
Thesis
Date of Award
5-31-1989
Degree Name
Master of Science in Civil Engineering - (M.S.)
Department
Civil and Environmental Engineering
First Advisor
John R. Schuring
Second Advisor
John W. Liskowitz
Third Advisor
Paul C. Chan
Fourth Advisor
Dorairaja Raghu
Abstract
Bench-scale laboratory studies were conducted from January 1988 to October 1988 to demonstrate the feasibility of using Pneumatic Fracturing* to enhance the removal of Volatile Organic Compounds from the vadose soil zone. Experiments were conducted to investigate: 1) The effect of pneumatic fracturing on the rate of contaminant removal; and 2) the injection pressures required to initiate soil fracturing.
Contaminated soil was placed and compacted in three identical 15 inch square by 30 inch high plexiglass tanks. The first tank was equipped with a vapor extraction system consisting of vacuum and/or positive air injection. The second tank was equipped with the same vapor extraction system, except the soil was pneumatically fractured at the beginning of the experiment. Pneumatic fracturing of the soil tanks was accomplished by inserting a 1/2 inch (I.D.) probe connected to an air reservoir tank and compressor. The third tank served as a control and was neither fractured nor equipped with a vapor extraction system.
Five series of experiments were conducted using a silty sand as the soil medium and a surrogate contaminant consisting of either water or a water/ethyl alcohol solution. The extraction processes and initial contaminant concentrations were varied for each experimental series. Contaminant losses were measured as a function of time using a total mass balance.
The experiments showed that pneumatic fracturing can significantly enhance the amount and rate of contaminant removed. Observed increases in contaminant removal efficiency ranged from 50% to 190% for fractured soil compared with non-fractured soil.
The fractures were observed to be distinct and mappable and resulted in a decrease in soil density on average of 11%. Records of soil color changes upon drying provided an indication of contaminant flow patterns.
Six additional series of experiments were conducted to estimate the injection pressure required to initiate soil fracture. The relationship between fracture pressure and overburden depth was found to be generally linear, except the magnitude of the fracture pressures was 10% to 400% greater than theoretically predicted depending on depth. Further experimentation showed this discrepancy was the result of tank wall friction.
The study includes an extensive review of existing and emerging in situ treatment technologies for the vadose soil zone. Recommendations are made for future research.
Recommended Citation
Papanicolaou, Panayiotis, "Laboratory model studies of pneumatic fracturing of soils to remove volatile organic compounds" (1989). Theses. 2858.
https://digitalcommons.njit.edu/theses/2858
