Research on the Formation Mechanism of Seepage Channels in Broken Rock Mass under the effects of Particle Migration

Abstract

Seepage within broken rock mass widely exists in geotechnical engineerings, such as railways, slopes, dam foundations and mining. Seepage is often accompanied by particle migration, which usually cause structural instability and water inrush disasters. In order to study the formation mechanism of seepage channels in the brocken rock mass under the effects of particle migration, a series of seepage tests were designed on broken red sandstone. The effects of pore pressure and particle size distribution (PSD) on particle migration and porosity evolution were studied. The main conclusions are as follows: 1) By observing the particles collected during the seepage process, particles with size range of 0-2 mm, 2-5 mm and 5-8 mm appear in sequence, which means that with the formation of seepage channels, large size of rock particles can pass through the broken rock mass. 2) The cumulative mass of migrating particle increases with the increase of pore pressure and decrease of PSD; with the increasing duration of migration process, the pore pressure and PSD decrease. 3) The peak value of porosity increases with the increase of pore pressure and decrease of PSD. According to above results, the seepage channels of the samples with smaller PSD and larger pore pressure are wider. Besides, the formation speed of seepage channels is larger in sample under higher pore perssure. These can explain the higher risk of geological disasters (i.e., water inrush and structural instability) in broken rock mass within higher pore pressure and smaller PSD.