Use of Vacuum for the Stabilization of Dry Sand Slopes

Abstract

Vacuum is proposed as a means for rescuing soil slopes showing signs of impending failure. Two aspects associated with the proposed method were studied; namely, the theory of airflow through dry soils and the effectiveness of vacuum for enhancing the stability of soil slopes. A model test device was developed, and two series of tests were carried out using this device. One was a series of tests on pore-air pressure distributions in dry sand slopes, and the second series involved dry sand slope stability tests. The results revealed that a vacuum (negative pore-air pressure) even as small as −0.4 kPa significantly increased the stability of the model slopes with dimensions of 0.9×0.5×0.28 m (length×width×height). The pore-air pressure distributions in the model slopes were simulated using a finite-element partial differential equation solver, FlexPDE. Fick’s law and mass conservation were used to formulate the airflow through dry soils. Good agreement was achieved between the experiment results and the numerical simulations. A computer routine, called Slope-Air, was developed for slope stability analysis using Bishop’s simplified method and considering the pore-air pressure distributions in the slope. The calculated factors of safety of the model slopes at failure were consistent with the results of the model slope stability tests.