Experimental study on effects of soil pipe on hillslope water dynamics and slope failure

Soil pipes (porous pipes inside a hillslope) are often detected in collapsed slopes indicating their influence on slope failure. Flume tests were conducted to see the impact of soil pipes on a slope failure. Three different soil pipe configurations: a) no pipe, b) closed pipe and c) open pipe that are common in the field were conducted. Two types of tests were conducted for each of the pipe configurations: a) rainfall induced failure test and b) seepage induced failure tests. Experimental results show that a closed pipe accumulates water around its lower end and continuously increasespore-water pressure till a failure. Open pipes if are blocked, raises pore-water pressure more rapidly than other cases leading to immediate soil mass movement. This indicates the blockage of open soilpipes makes a slope more susceptible to a failure. The result also showed sudden increase in discharge before the slope failure. Such an increase in hillslope discharge can be taken as an indication of increment in potentiality of slope failure in real hillslopes. Before a large failure small fluctuations in pore water pressure were also seen in the experiments. This can also be used as an indicator of impending failure in an instrumented hillslopes.