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Long term structural design of geosynthetic stormwater chambers and the use of nanocompsites to enhance their performance
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|Title: ||Long term structural design of geosynthetic stormwater chambers and the use of nanocompsites to enhance their performance|
|Authors: ||Filshill, Archibald Stewart|
|Keywords: ||Civil engineering;Geosynthetics;Nanocomposites (Materials)|
|Issue Date: ||23-Dec-2010|
|Abstract: ||Requirements for control of stormwater quantity and quality are often difficult to meet at high value commercial or institutional sites. The impetus to optimize the footprint of a site is illustrated by extensive use of retaining walls, reinforced soil slopes, porous pavement and other topographic “enhancers”. It is also desired to avoid diverting surface runoff to unsightly shallow basins during storm events. Regulations have required the use of Best Management Practices (BMP’s). These BMP’s have led to the development of subsurface stormwater detention systems. The efficiency of storing the required volume in subsurface chambers can be expressed in terms of porosity. That parameter and the structural “cover” required to distribute surface loads essentially dictate the storage volume and determines the depth and footprint of the excavation. Various systems such as precast concrete, metal or plastic arches or concrete vaults can be both shaped to fit and provide still more storage per unit volume. However, they tend to be costly and require a large footprint for installation. Newly introduced polymeric systems include High Density Polyethylene (HDPE) or Polypropylene (PP) modular chambers with 95 to 98% void space. The units are usually cubes with walls, floor and roof having an open truss-like structure to allow flow between chambers. The units can be stacked and are currently installed with total depth up to seven feet or more.
The modular plastic cubes give rise to concern about short-and long-term stability under overburden loads, due to differences in both familiarity and understanding of structural resistance of polymeric materials. Placing a stormwater detention system underground allows use of the surface above it for parking or creating a landscaped area. There are reasonable concerns about structural stability of pavement systems built above these types of chambers. Plastics are visco-elastic and can deform under heavy and repetitive loadings from vehicle traffic. While much is known about buried corrugated pipes, little is known about the effects of traffic (static or dynamic) whose entire load is carried by a buried plastic chamber underlying a pavement.
This thesis reviews the application, testing and design of these plastic cubes and reviews the few research papers that have been completed to date. It is focused on the structural design of these polymeric chambers, how they are tested, the flexible pavement design above such systems, the repetitive loading and the long term durability of the plastics used in manufacturing.|
|Appears in Collections:||Drexel Theses and Dissertations|
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