Investigation of swelling pressure of weak rocks in vicinity of support systems

Abstract

The support systems of excavations (such as underground mining openings and water tunnels) experience the time dependent induced pressure of the ground in vicinity of swellable rock. This research examines the interaction of swellable rock under different initial pressure to simulate the behavior of such rocks behind the support systems. A device was designed and constructed to model the condition in laboratory. Marlstone samples from Marash project in North West of Iran were chosen to perform the tests. The swelling pressure under different initial support pressure (ISP) was measured over time. The lowest swelling pressure was recorded under the minimum initial pressure. The swelling pressure of samples do not expose under high ISP (about 5 times of the steady swelling pressure). The differential swelling pressure (swelling pressure minus the ISP) generally increases from a minimum, at the lowest initial pressure, to a maximum, at the initial pressure equal to the steady swelling pressure. After reaching this maximum value, the differential pressure reduces back to zero where the ISP hampers the swelling phenomenon.