Foundations on unstable ground

Houses – moving due to expanding clay

By Vasos Vassiliou

Hundreds of houses in Cyprus are built on ‘sensitive’ geological areas, resulting in the need for frequent repairs, valuing thousands of pounds, or else these houses would have been dangerous to live in. The owners of these houses, which were built on clay ground, pay cumulatively tens of thousands of pounds patching up cracks on the walls, repairing broken tiles and appliances etc and not ever achieving a permanent restoration. Pentonite or clay is a soil type, which is abundant in Cyprus.

In the past, as geologist and ex-director of the Geological Department Mr. George Petrides told us, there was ignorance on the impacts of pentonite (during the preparation of the structural design). However, even today the problem has not vanished because houses continue to be built on pentonite without proper design. It becomes apparent that some housing developers do not seem to care much about future damages due to the ground characteristics.

Lately, buyers of houses, mostly foreigners, who bought houses built on expanding soils, very soon after they bought the houses noticed the appearance of cracks. They complained strongly and asked for solutions from the developers, but their problem was not solved. Some of them decided to take their cases to court.

A typical case is that of a woman from Britain who bought a house in a village in Paphos and when she returned from England in September, where she went for her vacations, discovered that the swimming pool of the house …..has moved.

However there is a correct way of constructing houses on pentonite, using the method of piles and deep foundations. With regards to existing houses, as Mr. Petrides explained, it is possible to stabilize the pentonite by mixing it with lime. After the mixing of the two soils these should then be compacted. However for the introduction of lime under an existing houses, test boreholes must first be drilled.

Regions of dangerous soils
District of Paphos
In these areas there is pure pentonite covering in total a surface area of a few square kilometres.
• Kathikas
• Pentalia
• Galataria
• Kelokedara
• Kidasi

District of Limassol
Expanding soils, with areas of pure pentonite are located in the district between Moni and Pentakomo

District of Nicosia
• Pallouriotisssa
• Kaimakli
• Area of Paedagogical Academy
In the above areas there is scattered pentonite

District of Famagusta
Expanding solis have been located around the Paralimni Lake

Mamouth damages
Damages caused internationally due to expanding soils are greater than those caused by earthquakes.

Expanding soils is the issue of a seminar, which will take place tomorrow Saturday during which experts, including university professors will explain their views.

What is clay
It is a soil material, which normally develops from the deposits of fine materials in water. These materials are a product of erosion of different rocks. Clay is a very plastic material and in the presence of water it becomes pliable and may keep any shape given to it. When dry it contracts and becomes harder and expands and softens again when wet. This process may be repeated continuously.

The island of pentonite
Cyprus is included in the countries with the largest (based on its surface area) presence of pentonite and clay soils in general. In the case of Cyprus, the soils are igneous and have an age of tens of millions of years, ie since the times the island rose from the sea.

Landslides and sensitive soils
Damages are caused in constructions (er. cracks) due to landslides which have been observed in 11 communities in Paphos. The Department of Geological Surveys has in the past located problematic soils. The department prepared geological studies and maps for each village separately and identified these problematic areas. These geological studies were sent to the Director of the Town Planning Department as well as the District Officer of Paphos. The common characteristic of the four villages is the identification of clay of the type ‘kannaviou’ or ‘malange’ of Mamonia. These soils present phenomena of expansion and contraction when their water content changes. Also landslides occur when the ground is inclined. According to a member of the Geological Department these soils are very vulnerable to instabilities especially under earthquakes or after heavy rainfalls. He added however that there are techniques to face these problems and this is the reason why it is not correct to forbid building development in these areas by proclaiming them as ‘White zones’.


Phileleftheros Newspaper
3/11/07