Use of Side Drains in Triaxial Testing at Moderate to High Pressures

Abstract

Abstract Side drains are used in triaxial tests to increase the rate of consolidation and equalize pore water pressures within the specimen. However, the efficiency of the side drains has been shown to be a function of time and effective confining pressure. This paper presents the results of (1) a mail survey on side drain practice, which indicates that many laboratories use side drains not recommended by standard references, and (2) an experimental program to assess the effects of time and moderate-to-high effective confining pressure on the flow properties of four side drain materials. The four side drain materials used in the testing program were: (1) a single layer of Whatman No. 1 filter paper; (2) a single layer of Whatman No. 54 filter paper; (3) a double layer of Whatman No. 54 filter paper; and (4) a single layer of geotextile. The lengthwise flow of these materials was examined as a function of effective confining pressure up to 6000 kPa and also of time at a fixed effective confining pressure of 750 kPa. Tests were also conducted on specimens of natural clay to compare consolidation rates using different drain materials.