From the GMA Techline
Subject: Geotextile for base stability— I am a landscape architect and value your Geosynthetics publication in my practice. While reading the June/July issue [and the article on] roads and housing on wet soils, a current project challenge of mine came to light: How to best provide base stability to a proposed bituminous asphalt tennis court through the use of geotextiles?
Further, can a geotextile be used to provide base stability, longevity, and possibly reduce costs, such as gravel fill? (Steven, Rhode Island)
Reply: Geotextiles are regularly used to provide separation, stabilization, and/or reinforcement to paved surfaces such as asphalt on a stone base course, as in a tennis court. The differences in the three functions that I just cited depend on the quality of the soil subgrade beneath the stone base course.
Separation (using a lightweight geotextile) is used for firm subgrades. Stabilization (using intermediate-weight geotextiles) is used for moderate subgrades. Reinforcement (using heavy geotextiles) is used for weak subgrades.
Fortunately, AASHTO (the organization of state highway departments) has specifications for separation and stabilization. Reinforcement requires a site-specific design.
As for your last question, geotextiles can be used to reduce base coarse thicknesses. There are many design charts available, but the ones I know are for roads … use these charts and be conservative.