Volume 28, Issue 4 (July 2005)
Liquid Extraction Using Prefabricated Vertical Wells (PVWs) Under Vacuum in Clay
A large-scale clay specimen was prepared in the laboratory using select soil to simulate WIDE technology using a geosynthetic wick drain. While a full-scale field test is necessary to quantify system flow and contaminant removal rates using WIDE technology, laboratory work is necessary to investigate flow phenomenon local to each PVW. Two methods were developed to measure the consistency of the water content and unit weight distribution for quality control purposes. Specimen preparation techniques, flow rates, settlement, piezometer, and tracer test concentration data were measured. The radius of influence, maximum extraction depth, and potential effects of long term PVW performance were discussed. The radius of influence ranged from 0.3 to 0.4 m. Due to the band shape of the PVW, the radius of influence and extraction depth were maximized near the center of the 100-mm-wide dimension, and flow efficiency was reduced near the corners of the PVW due to the decrease in PVW surface area near the 4-mm dimension. Subsequent to laboratory testing, portions of the geotextile filter jacket were utilized to determine the decrease, if any, in permeability. While there appeared to be a 14 % reduction in geotextile permeability during the test interval, soil particles also existed within the flow channels of the PVW core, indicating that long-term PVW efficiency may be a concern and needs further consideration.