Prefabricated geosynthetic drains: Characterization and implementation in MSE structures.

摘要

Failures of MSE structures are often a result of poor drainage which lead to the development of pore water pressure thus decreasing the soil strength while increasing the driving forces that act on such structures. As the demand for economical designs of earth retaining structures becomes more prevalent, particularly in the private sector, there is an ever-increasing need to implement low quality (low permeability) backfill into the reinforced zone. Hence, the frequency of failures of MSE structures is likely to increase unless the poor drainage properties of the fill material are mitigated by integrating filters such as prefabricated drains to intercept and transmit the water from behind the structure to a location where it can be properly handled.; Current performance properties and criteria of prefabricated drains are not readily available. This study reports the test results of several types of prefabricated drain products. The results show the transmissivity of such materials under varying normal pressures, representing soil overburden pressures, and hydraulic gradients. The experimental data shows that when transmissivity data is plotted on a semi-log scale against normal stress, a bi-linear behavior is exhibited. At a certain stress level, regardless of hydraulic gradient, there is a sharp reduction in transmissivity. At this critical stress, the drain's structure collapses and, from a practical viewpoint; it ceases to function. Consequently, this work reports the transmissivity of typical drains as well as the limit overburden pressure (or embedment depth) signifying the useful limit of such drains.; This work also shows numerically how the prefabricated drains can be integrated into MSE structures. The drainage capacity, embedment depth and a steady state flow are combined to produce a tool for the proper selection of a drain for a particular application. Parametric studies show the effectiveness of properly selected drains in increasing the stability of MSE structures.