Italy is a country susceptible to various and numerous natural disasters; landslide hazard is certainly one of the most important topics here, so the research for innovative and cost-effective solutions for landslide stabilization has great scientific and socio-economic relevance. This PhD fits the context by studying and developing a new technique for the stabilization of landslides, called “floating anchor”, both in theoretical and applied aspects. The technique involves the installation of passive nails in the landslide body, cemented along the entire profile with a sufficient foundation in the deep stable soil. The anchors fit the slope according to a discontinuous geometry without a continuous facing. Each anchor head connects only to a small concrete plate (the “floating” element), which may be bored in the soil. The reinforcements absorb by frictional contact a portion of the shear stress induced by the moving landslide, slowing down its evolution process until it completely stops. It is a modular and flexible technique; the system fits the soil deformations without losing effectiveness.
The PhD work analyses all the components of the system in order to assess the geotechnical and structural behaviour. A comparison with the techniques commonly used for landslide stabilization highlights the main advantages of the floating anchors, both in efficiency and cost terms. An important part of the research focuses on the experimental analysis in a 1g scale physical model of the behaviour of floating plates as a function of their shape. An equation for the calculation of the bearing capacity of the floating plate with the introduction of specific shape and volume factors has been determined. A FEM analysis provides a numerical model calibration based on the experimental results and highlights the influence of the plate on the soil stress-strain state. Specific guidelines for the design of floating anchors are proposed according to two physical-mathematical configurations: one “static” short-term approach and one long-term approach, assuming a non-linear viscous behaviour of the soil. At last, some applications complete the research: the development of a particular enhanced anchor bar (the “composite anchor”), and the design and execution of some stabilization works with floating anchors in four real landslides activated in North-Eastern Italy in conjunction with the exceptional rainfall that affected the area in autumn 2010. The monitoring of the stabilized slopes proves the viability and technical efficiency of the method
