Abstract
Abstract. Slope stabilization through drainage trenches is a classic approach in geotechnical engineering. Considering the low hydraulic conductivity of the soils in which this measure is usually adopted, a major constraint to the use of trenches is the time required to obtain a significant pore pressure decrease, here called “time lag”. In fact, especially when the slope safety factor is small, the use of drainage trenches may be a risky approach due to the probability that slope deformations will damage the system well before it will become fully operative. However, this paper shows that the presence of persistent permeable natural soil layers can provide a significant benefit by increasing drainage efficiency and reducing time lag. As a matter of fact, any permeable layer that is intercepted by trenches may operate as part of the global hydraulic system, reducing the drainage paths. A simplified approach to designing a drainage system that accounts for the presence of a persistent permeable layer is proposed. This approach, which can exploit solutions available in the literature for parallel drainage trenches, has been validated by numerical analyses.
Highlights
The stabilization of deep landslides in clay is one of the greatest challenges to engineers due to the high cost and the unreliability of many structural solutions
When the slope is characterized by a small safety factor or is subjected to slow movements (Urciuoli, 1998), the use of draining trenches is problematic due to the probability that slope deformations will damage the system well before it will become fully operative, cancelling out its potential effectiveness
The aim of this paper is to demonstrate that the presence of soil layers of higher permeability, a not unlikely condition in some deep landslides in clay, may be exploited to improve the efficiency of systems of drainage trenches for slope stabilization
Summary
The stabilization of deep landslides in clay is one of the greatest challenges to engineers due to the high cost and the unreliability of many structural solutions. The higher the depth of the trenches (or of drainage panels), the higher the probability that these intercept even thin soil layers of higher hydraulic conductivity at an intermediate depth between the ground surface and the slip surface. This would be a favourable condition since the incorporation of such layers in the drainage system may play a highly beneficial role in both the time to attain the final steady-state condition and the system efficiency. Urciuoli et al.: Technical note: The beneficial role of a natural permeable layer
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