Behaviour of a building foundation on unsaturated expansive soil

The paper presents a case study of the behaviour of a building foundation on expansive unsaturated clay. The load-bearing masonry building started exhibiting severe cracking in its superstructure, immediately after its completion around 1950. Despite the interventions, the problems continued to exist sixty years later. In the context of identifying the causes of these problems, the paper presents the results of the laboratory tests conducted on the expansive clay in order to estimate its swelling pressure and also understand its behaviour. It is shown that the seasonal variation of the water content of the foundation soil, combined with the intrusion of the root system of the nearby trees at the level of the foundation, subjected the soil to wetting-drying cycles, resulting in its corresponding swelling-shrinking and consequently the settlement of the building. Finally, the proposed countermeasures for the solution of problems are presented, which aimed mainly in minimizing the variation of the moisture of the soil around and at the foundation of the building

Behaviour of a building foundation on unsaturated expansive soil

The paper presents a case study of the behaviour of a building foundation on expansive unsaturated clay. The load-bearing masonry building started exhibiting severe cracking in its superstructure, immediately after its completion around 1950. Despite the interventions, the problems continued to exist sixty years later. In the context of identifying the causes of these problems, the paper presents the results of the laboratory tests conducted on the expansive clay in order to estimate its swelling pressure and also understand its behaviour. It is shown that the seasonal variation of the water content of the foundation soil, combined with the intrusion of the root system of the nearby trees at the level of the foundation, subjected the soil to wetting-drying cycles, resulting in its corresponding swelling-shrinking and consequently the settlement of the building. Finally, the proposed countermeasures for the solution of problems are presented, which aimed mainly in minimizing the variation of the moisture of the soil around and at the foundation of the building

Virtualising testbeds to support large-scale reconfigurable experimental facilities

Experimentally driven research for wireless sensor networks is invaluable to provide benchmarking and comparison of new ideas. An increasingly common tool in support of this is a testbed composed of real hardware devices which increases the realism of evaluation. However, due to hardware costs the size and heterogeneity of these testbeds is usually limited. In addition, a testbed typically has a relatively static configuration in terms of its network topology and its software support infrastructure, which limits the utility of that testbed to specific case-studies. We propose a novel approach that can be used to (i) interconnect a large number of small testbeds to provide a federated testbed of very large size, (ii) support the interconnection of heterogeneous hardware into a single testbed, and (iii) virtualise the physical testbed topology and thus minimise the need to relocate devices. We present the most important design issues of our approach and evaluate its performance. Our results indicate that testbed virtualisation can be achieved with high efficiency and without hindering the realism of experiments