Field test study on expansive soil canal of middle route of South to North Water Diversion Project

Abstract

The south to North Water Diversion Project is the most magnificent Chinese water diversion project, the project includes eastern, central and west routes, of which the total length of mid-route canal is about 1200 km. majority of the channel is the open canal, partly with the culvert, crossing river by the aqueduct or tunnel. The channel goes across China's Yangtze River, the Yellow River, Huaihe, Haihe River. There are expansive rock and soil, loess, easy-liquefied sand and other special soil (rock) area along the channel with complicated engineering geological condition. The accumulative total length involved the expansive soil (rock) area is about 340km. Due to the special engineering properties of the expansive soil (rock), it is very vulnerable to slope instability with a great impact on the safe operation of the project. Therefore, the treatment of the expansive soil (rock) is one of the main technical problems in the South to North Water Diversion project. To study the failure mode and stability mechanism of the expansive soil channel slope, typical channel slopes with the respective length of 2.05km and 1.5km were selected to conduct the field test studies for 3 years. The selected slope were preinstalled inclinometer, slope displacement meter, water content and suction probe, et al. To reveal the mechanism of instability of slope of expansive soil channel. Field experiment shows that: the expansive soil slope instability has two patterns of failure modes, one is the instability induced by the expansive deformation, and another is the instability controlled by fissure strength. In order to guarantee the stability of expansive soil slope, it is essential to identify the different failure modes in the design analysis.