Abstract
Flexible systems anchored to the ground constitute a technique for slope surface stabilisation. They are formed by membranes (cable nets, wire mesh, ring net), reinforcement cables and bolts tightly anchored to the ground forming regular patterns. Most manufacturers and independent researchers assume active behaviour of these systems when they propose their design models, which means that the system avoids occurrence of instability. To consider active behaviour, two conditions have to be fulfilled: the membrane has to be initially prestressed and the slope must present a convex shape. Neither of these two conditions has been verified so far, therefore, there are no guarantees that current design methods are adequate. Review of the technical brochures of manufacturers shows that applied prestress force on membranes and reinforcement cables is nonexistent or very low.
In this paper, three field systems in north Spain with cable nets anchored to the ground have been instrumented. Net cables, reinforcement cables and bolt heads have been instrumented by using sensors based on electrical extensometry. Tensile forces on cables and compression forces on bolt heads have been monitored for more than a year from the beginning of installation. Initial tensile forces in net and reinforcement cables induced an average value of 0.7% and 2.1%, respectively, of the ultimate strength of each component. In relation to bolts, average compression force on bolt heads was 5.3% of their ultimate strength.
These measurements demonstrate that prestress force on flexible systems is very low, and nearly negligible. Therefore, flexible systems anchored to the ground cannot be considered as active, but passive, which means that most current design methods are not adequate.
In this paper, three field systems in north Spain with cable nets anchored to the ground have been instrumented. Net cables, reinforcement cables and bolt heads have been instrumented by using sensors based on electrical extensometry. Tensile forces on cables and compression forces on bolt heads have been monitored for more than a year from the beginning of installation. Initial tensile forces in net and reinforcement cables induced an average value of 0.7% and 2.1%, respectively, of the ultimate strength of each component. In relation to bolts, average compression force on bolt heads was 5.3% of their ultimate strength.
These measurements demonstrate that prestress force on flexible systems is very low, and nearly negligible. Therefore, flexible systems anchored to the ground cannot be considered as active, but passive, which means that most current design methods are not adequate.
| Original language | English |
|---|---|
| Pages (from-to) | 95-104 |
| Number of pages | 10 |
| Journal | Engineering Geology |
| Volume | 153 |
| Early online date | 19 Dec 2012 |
| DOIs | |
| Publication status | Published - 8 Feb 2013 |
| Externally published | Yes |
Bibliographical note
NOTICE: this is the author’s version of a work that was accepted for publication in Engineering Geology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Engineering Geology [[153] (2013)] DOI: 10.1016/j.enggeo.2012.11.015© 2013, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/
Keywords
- Slope stabilisation
- Cable nets
- Wire meshes
- Passive systems
- Active systems
- Instrumentation