2nd International Conference on New Developments in Soil Mechanics and Geotechnical Engineering,

28-30 May 2009, Near East University, Nicosia, North Cyprus

Geotechnical properties of Nicosia soils, Cyprus

C. Atalar Department of Civil Engineering, Near East University, Nicosia, North Cyprus, catalar@neu.edu.tr B.M. Das Dean Emeritus, California State University, Sacramento,U.S.A. brajamdas@gmail.com

KEYWORDS: Alluvium soils, swelling clays, Montmorillonite, water fluctuation, liquid limit. ABSTRACT: Swelling clays, Alluvial soils, collapsible soils and evaporitic bedrocks constitute the major problematic soils of Cyprus. The walled city of Nicosia and its closed surroundings are covered by fill. Alluviums of low bearing capacity and collapsible soils are present around the Pedios river in the southeast, southwest, and at the old bed of Pedios stream in the northeast. Swelling clays are extensively exposed around the city. Extensive outcrops of uncemented gravel covers part of the southeast and southwest. Calcarenite, sandstone and limestone of high bearing capacity are exposed in the south and southeast. Evaporitic bedrocks mainly gypsum are generally present on the surface or just below the surface and at the banks of the streams. Field studies, geotechnical investigations, geotechnical properties, X-ray diffraction, and scanning electron microscopy results are presented. These studies were conducted around Nicosia during the last eight years. Swelling clays of Nicosia are Nicosia Formation Clays and Kythrea Group Clays. Swelling potential of Nicosia Formation Clays are high to extremely high and Kythrea Group Clays are intermediate to high . The clay minerals contained large amounts of montmorillonite, lesser amounts of illite and kaolinite. The alluviums also contain high amount of montmorillonite. These alluviums show relatively high apparent strength in their dry state. However, with saturation their strength decreases. These clayey soils have low to medium swelling potential. 1 INTRODUCTION Cyprus with an area of 9,251 km² is the third biggest island in the Mediterranean sea, and the biggest island in Eastern Mediterranean region. North Cyprus covers an area of 3,299 km². The ancient settlements and the early building sites of Cyprus were located at the top or the slopes plateau of the rocky hills. The first Cypriot capital Enkomi (Alasya) (1700 BC) was established at a rocky plateau on the north bank of the Pedieos river near present day Famagusta (Gazimagusa). Soli (1193 BC) one of the ten city-kingdoms of Cyprus was build on pillow lavas at the northern slopes of Trodos mountains, Vuni Palace (498 BC) was build on top of a limestone cap of pillow lavas and the Limniti (Yeşilırmak) islet (7,000 BC) is on top of limestone hill all near day Lefka (Lefke). Nicosia, the present capital is one of the few island capitals that do not lie on the coast. Nicosia was a city-state known as Ledra or Ledrae in ancient times. Ledra in Hellenic and Roman times was a small, unimportant town. The city became the island's capital around the 10th century. It had grown in importance because of threats of pirates to the coastal capitals Paphos and Salamis, which made many people flee to the centrally located Nicosia. It has risen to its present importance as the

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2nd International Conference on New Developments in Soil Mechanics and Geotechnical Engineering,

28-30 May 2009, Near East University, Nicosia, North Cyprus

administrative capital only since Lusignan times (1192). The seat of the Lusignan kings of Cyprus since 1192, it became a Venetian possession in 1489, and Ottoman Empire possession in 1570. The British Empire leased the island in 1878, with Nicosia serving as the capital of the new British possession.

Nicosia was built on a thick alluvium avoiding the nearby clay hills to avoid damages from the swelling clays. However, soft alluviums also sometimes may cause major geotechnical problems. Bedestan is the oldest building suffered damages due to soft alluviums (Figure 1a). Nicosia is covered by extensive surficial deposits of soft soils. The walled city and its closed surroundings are covered by artificial fill (Figure 1b). Alluviums of low bearing capacity are present around the Pedios river in the southeast, southwest, and at the old bed of Pedios river in the northeast. Marl is extensively exposed in the eastern and western parts of the city. Extensive outcrops of uncemented gravel covers part of the southeast and southwest. Calcarenite, sandstone and limestone of high bearing capacity are exposed in the south and southeast (GSD 1982; De Coster et al. 2004).

a b

Figure 1. Bedesten (a) and walled city of Nicosia (b).

2 GEOLOGICAL BACKGROUND Cyprus is situated at the triple junction of Eurasia, Arabian, and African plates, and has played a very important role for the geological understanding of the Eastern Mediterranean region. The geology of Cyprus governs the topography. Cyprus may be divided into six geological zones according to geological evolution and emplacement of its geological units (Atalar 2005): (1) Troodos Zone or the Troodos Ophiolite, (2) North Cyprus (Kyrenia) Zone, (3) Mamonia Zone or Mamonia Complex, (4) South Cyprus Zone, (5) Mesaoria Zone, and (6) Alluviums. Cyprus has had an active and complex neotectonic history that includes numerous devastating historical earthquakes. There is a major rhomb-shaped graben that underlies most of northern metropolitan Nicosia. The graben preserves a section of the Late Miocene (Messinian) Kalavasos (Mermertepe) Formation, which was eroded from areas outside of the graben (Harrison et al. 2004). During periods of heavy rain, ephemeral streams will flow into some of the sinkholes, on the outskirts of the Pergamos (Pergama) village often resulting in additional collapse. Lately newly formed sinkholes have threatened recent housing developments from the expanding village. Field investigations have determined that the collapses are controlled by a fault system, which cuts through a carbonate/evaporite stratigraphic sequence (Harrison et al. 2002). 3 SEISMICITY OF CYPRUS Cyprus has been subject to earthquakes all through her history. The Bronze Age city of Alasia (Enkomi), first century Paphos, fourth and seventh century Salamis were among the areas badly damaged or virtually destroyed by earthquakes. However, despite lying in the second most earthquake stricken zone on earth, Cyprus sector of this zone at the time being is less active and it experiences earthquakes less frequently and of a lower magnitude than that of Greece and Turkey.

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Geotechnical properties of Nicosia soils, Cyprus Atalar C. & Das B.M..

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Seismicity of Cyprus between 1890 and 1990 are presented at Figure 2. In recent years there are two fortunately non-destructive events have occurred with signifant magnitudes of 5.8-5.9 (February 23, 2005) and 6.8-6.9 (October 9, 1996).

Figure 2 Seismicity of Cyprus 1890-1990 Ms≥4.5 (Ambraseys & Adams 1992)

4 SOILS OF CYPRUS Alluvial soils and overconsolidated clays constitute the most soils of Cyprus (Figure 2). Most of them especially the alluvial soils are located at a topographically low, rather flat area which occupies the central part of the island between the Troodos range to the south and the Girne range to the north. Most of the problems encountered in North Cyprus, in construction involves silty – clayey soft soils due to their low strength, durability and high compressibility, and the swell shrink nature of the overconsolidated swelling soils. Landslides occur at the steep slopes of the clayey formations (Atalar & Das 2004). There is widespread damage to the buildings, major roads and highways all over the country which were founded on swelling clays (Atalar 2002; Atalar et al. 2003; Atalar 2004b).

Figure 3. Cyprus soils (Revised from GSD 1995).

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2nd International Conference on New Developments in Soil Mechanics and Geotechnical Engineering,

28-30 May 2009, Near East University, Nicosia, North Cyprus

Alluvial soils Holocene to recent in age containing gravel, sand, silt and clay are widespread in the Mesaoria plain, especially at Nicosia and Famagusta and at the east and west coast. They comprise loose - medium dense gravel and sand, and soft - firm silt and clays. The alluviums mostly contain low amounts of clay size material. The alluviums also contain high amount of montmorillonite. These alluviums show relatively high apparent strength in their dry state. However, with saturation their strength decreases. These alluvial soils have low to intermediate and high to extremely high swelling potential. The silting of the ancient harbours created very soft soils especially at the east and west coastline of the Mesaoria plain. Old stream beds filled with alluviums are found at the coastline and at the interior. Overconsolidated swelling clays of Cyprus occurred as a result of the alteration of the Troodos ophiolite and the pelagic sedimentary cycles that followed in the post Createceous period. The calcium corbonate content of the marls originated from the limestones and dolomites of the Kyrenia zone. Cyprus clays can be divided into 5 groups. 1.Clays of Mamonia Complex, 2.Bentonitic Clays, 3.Clays of Kythrea (Değirmenlik) Group, 4.Mesaoria clay zone and 5.Alluvial clays (Table 1).

Table 1. Swelling potential of Cyprus clays Clays Liquid Limit (LL) Swelling Potential

Alluvium (North Nicosia) 32 - 48 Low - Intermediate

Alluvium (South Nicosia) 60 - 115 High – Extremely High

Nicosia Formation 53 - 119 High – Extremely High Kythrea Group 47 - 73 Intermediate – High

Mamonia Complex 33 - 167 Intermediate – Extremely High Bentonitic Clays 55 - 210 High – Extremely High

Compiled from Atalar (2002), Atalar (2004a), Atalar (2005), Atalar et al. (2006a), Atalar et al. (2006b), Atalar (2007), Constantinou et al. (2002) & Petrides et al. (2004)

5 SOILS OF NICOSIA Nicosia is almost flat lying at about 110 - 160m above the mean sea level and is located between the Kyrenia and Troodos ranges. Kanlı dere (Pedieos stream) is the main stream of Cyprus originates in the Troodos mountains in the south initially flowing to the north, north-east and until 1567 divided Nicosia north and south. In 1567 The Pedios was diverted outside the lessening of the circuit of the Nicosia walls. The Mesarya (Mesaoria) basin is drained by Kanlı dere (Pedieos stream) to the east and Dar dere (Ovgos stream) to the west. The walled city and its closed surroundings are covered by fill. Pedieos is the main stream of Nicosia, originates in the Troodos mountains in the south initially flowing to the north, north-east and until 1567 divided Nicosia north and south. In 1567 The Pedios was diverted outside the lessening of the circuit of the Nicosia walls. The soils of Nicosia are; Man made fill Alluviums Apalos Formation Nicosia Formation Gravel-Sand

Sand- Calcarenite (Athalassa Member) (Lefkoşa) Gravel-sand (Kephales Member) Clay (Nicosia Marl Member) (Çamlıbel) Gravel-sand (Basal Conglomerate Member)

Kalavasos (Mermertepe) Lapatza (Yazılıtepe) Kythrea Group (Değirmenlik)

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Kythrea Group ; The Kythrea group mostly contains turbiditic rocks. The group, consists from bottom to top, gravel, conglomerates, greywacke, marl, and mostly abyssal turbidites with a shallow environmental chalk, marl, limestone, and gypsum finishing. alternation of sandstone-siltstone-marl-claystone are widespread within the group. The group is only observed in North Cyprus and has a complete coverage of the northern and southern slopes of Kyrenia range from east to west. The Kythrea group consists Lapatza (Yazılıtepe) (Pre-evaporitic) and Kalavasos (Mermertepe) Formations (Atalar 2002 & Acar et al. 2003). Nicosia Formation ; Overconsolidated clays with high to very high swelling potential occur in geologic units of Nicosia Formation of Pliocene age and are extensively exposed in big settlements like Nicosia, Famagusta, Larnaka and Polis. The southern parts of Nicosia and Famagusta is completely covered by this formation. The Nicosia formation mainly contains marls. Gravels, limestones and conglomerates are also present in this formation, The clay minerals contained are large amounts of montmorillonite, lesser amounts of illite and kaolinite. Some researchers describe the Myrtou formation seperate while others describe it together with the Nicosia Formation. Alluvium ; The alluviums, Holocene to recent in age containing gravel, sand, silt, and clay are widespread in the Mesaoria plain, especially at Nicosia and Famagusta and at the east and west coasts, (Figure 7). They comprise loose - medium dense gravel and sand, and soft - firm silt and clays. The alluviums mostly contain low amounts of clay size material. The alluviums also contain high amount of montmorillonite. The alluviums show relatively high strength in their dry state. However, with saturation their strength decreases. (Atalar 2008a; 2008b & Atalar & Das 2008).

Figure 4. Recent alluviums at the bank of Pedios

6 LABORATORY TEST RESULTS Laboratory test results of several works are given in Tables 2 and 3.

Table 2. Triaxial Test Results SPT N values of Nicosia soils Soil Type cu (KN/m²) φu (°) SPT N

Man made fill 13 - R Alluvial yellowish brown and brown silty clay: 60-130 12.2-31.0 2 - R Apalos reddish hard silty clay: 260 80 68 - R Apalos yellowish silty sand with some clay: 125 66.2 68 - R Athalassa oxidized hard marl: 1320 44 55 - R Nicosia yellowish brownish khaki and light Khaki marl: 140-960 2.0-20.1 21 - 60 Nicosia grey marl: 340 - 420 20 21 - 60 Lapatza 69 - R Kythrea marl R Reworked marl (light khaki, brown khaki silty clay): 52-130 6.5-18.9

Refusal (R)

Compiled from Atalar (2002), Atalar (2004a), Atalar (2005), Atalar et al. (2006a), Atalar et al. (2006b), Atalar (2007) & Petrides et al. (2004)

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2nd International Conference on New Developments in Soil Mechanics and Geotechnical Engineering,

28-30 May 2009, Near East University, Nicosia, North Cyprus

Table 3. Atterberg Limits, Montmorillonite and CaCO3 contents of Nicosia soils

Soil Type Atterberg Limits

LL PI Montmorill

onite % CaCO3

% Alluvial soil bright 47 19 27 - 40 Alluvial soil dark grey 32 - 45 13 - 24 15 - 22 Alluvial yellowish brown or white reddish silty clay 60 – 62 35 - 36 11 - Alluvial brown and dark brown silty clay 72 – 115 34 - 62 20 - 32 - Apalos brown-red or brown-khaki silty clay 52 – 113 24 - 72 13 - 20 23 - 24 Nicosia and Athalassa yellowish, khaki and brown oxidized marl

66 - 119 38 - 79 9 - 26 21 - 48

Nicosia and Athalassa grey, dark grey marl 55 - 95 30 - 55 4 - 25 25 – 36* Kythrea grey marl 55 – 70 30 - 42 14 - 16 28 - 46 Reworked marl (light khaki, brown khaki silty clay) 60 – 84 35 - 45 10 - 22 23 - 24

* two results 63 - 64.

Compiled from Atalar (2002), Atalar (2004a), Atalar (2005), Atalar et al. (2006a), Atalar et al. (2006b), Atalar (2007) & Petrides et al. (2004)

The semi quantitative X-ray diffraction and Scanning microprobe analyses indicated that the predominant clay mineral is smectite, illite and chlorite or kaolinite are the other abundant clay minerals. Calcite is the major mineral of the marls, quartz and feldspar are also present at high amounts (Figure 5).

illite calcite kaolinite smectite

Figure 5. The scanning microprobe analyses showing smectite, illite, calcite, and kaolinite (left), and general

texture (right) (Atalar 2002)

Figure 6. The semi quantitative X-ray diffraction of clay (left) and bright alluvial soil (right) (Atalar 2004a)

B.1. - 430 Bright Alluvial soil % 15 smectite, % 5 illite, % 5 chlorite or kaolinite, % 62 calcite , % 2 dolomite, % 2 quartz, % 9 feldspar. B.4. – 15.50 Bright Nicosia marl % 30 smectite , % 10 illite, % 10 chlorite or kaolinite, % 30 calcite, % 9 dolomite, % 5 quartz, % 4 feldspar.

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Montmorillonite (smectite) with an amount ranging between 10 and 30%. Illite and chlorite or kaolinite with an amount ranging between 5 and 10% are the other clay minerals. Calcite with an amount ranging between 30 and 65% is the major mineral of the alluviums and marls. The other minerals are Quartz ranging between 2 and 6%, Feldspar ranging between 4 and 15 %, and Dolomite ranging between 2 and 9%.

Table 4. Laboratory analysis of Alluvial soil and Nicosia marl (Atalar 2004a)

Borehole No.

Depth m

% CaCO3

Sieve Analysis Above Below

Atterberg Limits

2.00 mm 600μ 75μ 75μ LL PL PI BD-1 4.30 22-40 0.00 0.16 3.83 96.17 47 28 19 BD-4 15.50 39 0.00 0.28 1.27 98.73 60 25 35

The dark grey alluviums contain between 15% and 21.5%, the brighter coloured alluviums contain between 27% and 40%, and the marls contain between 32% and 46% CaCO3. (Atalar 2004a). 7 DAMAGES Buildings were damaged to some extent because of the swell/shrink mechanism of the swelling clays. Most frequently observed damages were on the walls (both internal and external), above and below the windows, above the doors, and corners (Figure 7) (Acar et al. 2003; Atalar 2002; Atalar 2004b). Four boreholes were monitored for the water fluctuation for a year. The fluctuation was found to range from one to two meters (Atalar 2002).

Figure 7. Severe cracks near the ceiling (left) and extensively damaged house being repaired

7 CONCLUSIONS Nicosia the capital city is in the middle of the Mesaoria plain which is located between the Kyrenia and Troodos ranges. The alluvium soils and Nicosia Formation clays are widespread around the city. Nicosia is covered by extensive surficial deposits of alluvial soils of up to a thickness of 22 m. The walled city and its closed surroundings are covered by fill. Alluviums of low bearing capacity are present around the Pedios river in the southeast, southwest, and at the old bed of Pedios river in the northeast. Extensive outcrops of uncemented gravel covers part of the southeast and southwest.

The alluviums generally are represented with sand-silt on top and sandy-gravel at the bottom, The alluviums show relatively higher apparent strength in their dry state. However, with saturation their strength decreases very sharply. The alluvial soils of the present stream beds and the diverted Pedios bed of 1567 represent the soils of least SPT N values.

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