Abstract: In soil improvement with vacuum preloading projects, plastic prefabricated vertical drains (PVD or wick drains) are inserted into the foundation soils to provide vertical drainage channels. After construction, a large number of plastic wick drains are left in the soils, resulting in not just white pollution but also potential groundwater contamination. In this paper, three different types of biodegradable wick drains made of straws are laboratory tested. The feasibility of the straw wick drains to be applied in the practical engineering projects is verified. The results showed that the straw wick drains are degraded by bacteria in soils, the water discharge capacity and tensile strength decreases with the increase of time. The degradation rate is 40% after 240 days. The water flux and tensile strength of degradable wick drains are lower than those of the plastic wick drains, but they all meet the project requirements. It can be used instead of the plastic wick drains in the vacuum preloading soil improvement projects, which can not only solve the environmental pollution problem, but also expand a new way of comprehensive utilization of straw resources.

Key words: Vacuum Preloading, Degradable Prefabricated Vertical Drains, Straw Utilization, Consolidation