Mdina

Mdina, Malta’s medieval capital and later Baroque fortress, one of Europe’s finest examples of an ancient walled city, lies on a geologically sensitive area. In fact, many of its bastion walls and adjoining buildings, lying on the outer perimeter of the town, have serious structural problems. The main scope of this project was to consolidate the fragile terrain on which the bastion walls and historic palaces such as the Vilhena Palace at the entrance to Malta’s medieval capital city are built in order to diminish and possibly stop further settlement and damage of these historic legacies.

In 1966, UNESCO was commissioned to prepare a technical report on the interventions necessary to arrest the movements and its conclusions highlighted the importance of controlling the hydrology of the area and the underpinning of the bastion walls with bored piles. Later studies proposed underpinning of the bastion walls with the tip of propped cantilevers supported on micro-piles. A study commissioned by the Maltese Government in 2002 for a geotechnical investigation of the bastions perimeter around the Vilhena Palace, after significant movements in the area were recorded, involved a site monitoring program linked with climatic observations that was carried out for a period of 18 months. The geotechnical investigations indicated that there was significant ground movement in certain areas, particularly in the area of Council Square.

A two dimensional computer model using a dedicated finite element program was made using the material and geometric data gathered. The results of the computer model formed the basis of a design proposal which had the main scope of arresting the rotation and movement of the bastion walls by:

 · Limiting the plasticization of the clay due to excessive bearing pressures;

· Confine the clay under the structures;

· Tie together the fractured upper coralline limestone;

· Reduce the erosion of substrata composed of orange sand, yellow and blue clay;

· Ground improvement by geotechnical processes to increase the allowable bearing pressures and to reduce settlement.

The historic fortifications of Mdina constitute one of the main pillars of Malta’s built-up physical heritage assets. As an architectural monument, its fortifications document both important stages in the Island’s history and also the development of military architecture throughout the Middle Ages and early modern period. The city’s fortifications also form an integral and visual part of the island’s cultural landscape. The larger part of Mdina’s fortifications also play an important role in tourism.