Evaluation of drainage tunnel effectiveness in landslide control

Abstract

Infiltration of rainfall into hillslopes is often an important factor in triggering landslides. Using underground water drainage works together with anti-slide piles has been an effective method of landslide control, yet their effectiveness is inadequately discussed in the literature. This paper studies the influence of rainfall on the change in the underground water level beneath a slope by real-time and synchronic monitoring of the rainfall, the underground water level in the boreholes, and the flow rate of the underground drainage tunnel. The effectiveness of the underground drainage tunnel in preventing the rise of the underground water level of the slope is discussed. The researchers also study the deformation behavior of the anti-slide piles by monitoring the lateral displacement of the piles and analyzing the thrust that the anti-slide piles bear by numerical inversion techniques. The results indicate that there is an apparent relationship between the lag in the rising of the underground water level caused by a rainfall and that caused by the immediately previous rainfall. When there is a rainfall accumulation before the occurrence of a heavy rain, this particular heavy rainfall will cause a rapid rise of the underground water level beneath the slope. The monitoring data analysis shows that the flow rate of the underground drainage tunnel increases first, and then the underground water level of the slope rises after a rainfall. In other words, the flow rate of the underground drainage tunnel increases at a rate faster than that of the rise of the underground water level. Hence, the underground drainage tunnel can effectively lower the rise of the underground water level induced by a rainfall. Besides, based on the monitoring data of the lateral displacement of the anti-slide piles and subsequent analysis, the working state of the anti-slide piles is justified. It thus indirectly validates the benefits of using underground drainage tunnel in landslide control. © Springer-Verlag 2010.