Presently, the authors have collected information and data on 301 failed MSE walls using geosynthetic reinforcement. Of the total, 64% were caused by internal or external hydraulic situations. The most common specific causes of the failures are as follows: Internal Water (37%) – drainage pipe leakage, catch basin leakage, pressure pipe breakage, perched water and saturated backfill. External Water (27%) – retained soil seepage, tension crack water pressure, surface infiltration, high phreatic surface and soil erosion at the toe of the wall. It should be added that 73% of the wall failures used relatively impermeable silt and clay backfill soils in the reinforced soil zone. In the authors’ opinion, such fine-grained backfill soils must have front drainage gravel (which is generally provided) and back drainage using a geocomposite drain (which is rarely provided). Obviously, both drainage systems must have suitable outlets thus the need for a base (or blanket) drain. These are all obvious locations where geotextile filters are essential. The paper will provide statistics of the worldwide situation, along with proper preventative actions, and conclude with suggestions/recommendations for future practice. Hopefully, this paper will set up the remaining papers and presentations to follow in this session on drainage and filtration associated with MSE walls.
Menu