EnvironGeology v53n6 2008 QualityDurabilityArmourstone Ertas&Topal

ORIGINAL ARTICLE

Quality and durability assessments of the armourstonesfor two rubble mound breakwaters (Mersin, Turkey)

B. Ertas T. Topal

Received: 7 January 2007 / Accepted: 1 March 2007 / Published online: 24 March 2007

Springer-Verlag 2007

Abstract Due to economic reasons, natural stones

(armourstones) of various sizes and qualities are very fre-

quently used for the constructions of the breakwaters to

protect coastal engineering structures from wave actions.

Deterioration of the armourstones with time in the form of

abrasion and disintegration may end up with the damage of

the structures. Therefore, it is necessary to investigate the

long-term performance and quality of the armourstones,

which should be sound and durable. Mersin and Kumkuyu

harbours were constructed using four different limestones

obtained from two quarries. The limestones have different

characters and site performances. In this study, the material

and mass properties of the limestones taken from the

quarries with known site performances as armourstones are

investigated. The site performances and durability of the

limestones are compared with the field measurements and

laboratory works. Thus, the information obtained is used to

assess long-term durability of the armourstones. The long-

term performance of the Degirmencayi and Tirtar upper

level limestones are observed to be good whereas it is ra-

ther poor for the Tirtar middle and lower level limestones.

Comparison between the predicted and observed durabili-

ties of the armourstones indicated that CIRIA/CUR, RDId,

RERS, and wet to dry strength ratio give better results

based on their field performances. However, the prediction

of the durability of the limestones is poor in case RDIs,

average pore diameter, and saturation coefficient are used.

Keywords Armourstone Breakwater Durability Mersin Quality Turkey

Introduction

Rubble mound breakwaters are important coastal defence

structures for harbour and shore protection. Large quanti-

ties of natural rocks with different sizes and shapes are

commonly used as armourstone in the construction of the

breakwaters (Mather 1985; Latham 1991; Poole 1991;

Erickson 1993; Smith 1999; Topal and Acir 2004; Latham

et al. 2006a, b). They may have variable properties because

of their geological origins (Latham et al. 1990). Severe

marine environmental conditions, particularly during

storms, require suitable armourstone having certain phys-

ical and mechanical properties, and durability characteris-

tics (Fookes and Poole 1981; Lienhart and Stransky 1981;

Dibb et al. 1983; Clark 1988; Clark and Palmer 1991;

Magoon and Baird 1992; Lutton and Erickson 1992; Stank

and Knox 1992; Lienhart 1994, 2003; Latham 1998; Ertas

and Topal 2006). The deterioration of the armourstones

with time in the form of abrasion and disintegration may

cause damage to the coastal engineering structures.

Rubble mound breakwaters were constructed for Mersin

and Kumkuyu harbours in Turkey in the past (Figs. 1, 2).

The armourstones were obtained from Degirmencayi

quarry for Mersin harbour, and from Tirtar quarry for

Kumkuyu harbour (Fig. 3). The region is characterized by

a typical Mediterranean climate having hot-dry summers,

and mild-rainy winters with very high relative humidity.

However, some of the stones used in these breakwaters

show poor site performances.

The purpose of this study is to determine which

combinations of laboratory/field tests best predicted the

quality and durability of the armourstones used in Mersin

and Kumkuyu harbours through available durability

assessment methods. For this purpose, several laboratory

tests were conducted to determine the physical and

B. Ertas T. Topal (&)Department of Geological Engineering,

Middle East Technical University, 06531 Ankara, Turkey

e-mail: [email protected]

123

Environ Geol (2008) 53:12351247

DOI 10.1007/s00254-007-0712-z

mechanical properties of the armourstones, and to

understand their behaviours under different environmen-

tal conditions. The findings were then correlated with the

field performances of the armourstones in order to assess

their long-term durabilities.

Geological setting

In the Degirmencayi quarry (Fig. 3a), the rock is micritic

fossiliferous limestone (Ozbek et al. 2003). It is beige,

thick bedded to massive, moderately weathered near the

Fig. 1 Armourstones used in a Mersin and b Kumkuyu harbours

Fig. 2 Location map of thestudy area

Fig. 3 A view from a the Degirmencayi and b the Tirtar quarries

1236 Environ Geol (2008) 53:12351247

123

surface but slightly weathered below the surface. Under the

microscope, locally clayey lenses or veins exist within the

rock. Fossil fragments and intraclasts are embedded within

calcareous matrix. The limestone also contains solution

cavities near the surface (Ertas and Topal 2006). Based on

the fossil content, the age of the limestone is indicated to be

EarlyMiddle Miocene (Senol et al. 1998).

In Tirtar quarry, there exist three limestone levels hav-

ing different engineering properties (Ertas and Topal

2006). They are named Tirtar upper level, middle level and

lower level limestones in this study (Fig. 3b). Bilgin et al.

(1994) indicated that the age of the limestone exposed in

the quarry is Middle Miocene based on the fossil content.

Upper level of the quarry is light brown, fine-grained, thick

bedded, slightly weathered, microsparitic-sparitic fossilif-

erous limestone containing oolite, pisolite and other fossil

fragments. These fragments are embedded in sparitic cal-

careous matrix. The limestone contains local solution

cavities for the upper 12 m of the quarry. No dissolution

effect can be observed below this level. The total thickness

of the upper limestone level varies between 4 and 6 m. The

middle level limestone is weaker than the upper level

limestone. The middle level limestone is beige to light

brown. This limestone is classified as biosparitic limestone.

It contains nummulites within the calcareous matrix. In the

limestone, there are microscale solutions cavities filled

Table 1 Index properties of the Degirmencayi limestone

Properties Standard used

for testing

Number

of tests

Dry

mean SDaTest results Saturated

Mean SDa

Unit weight (kN/m3) ISRM (1981) 180 23.71 2.00 24.65 1.80

Effective porosity (%) ISRM (1981) 180 9.62 5.82

Water absorption under atmospheric

pressure-by weight (%)

TS699 (1987) 180 3.31 2.40

Water absorption under atmospheric

pressure-by volume (%)

TS699 (1987) 180 7.59 4.83

Water absorption under pressure-by weight (%) ISRM (1981) 180 4.13 2.85

Water absorption under pressure-by volume (%) ISRM (1981) 180 9.62 5.82

Saturation coefficient TS699 (1987) 180 0.81 0.39

Methylene blue adsorption value, MBA (g/100 g) AFNOR (1980) 2 0.30 0.05

Cation exchange capacity, CECb (meq./100 g) AFNOR (1980) 2 0.68 0.11

Wetdry loss (%) ASTM (1992) 6 0.57 0.16

Freezethaw loss (%) CIRIA/CUR (1991) 6 1.25 0.66

Magnesium sulphate soundness value (%) ASTM (1990) 6 4.56 1.61

Sodium sulphate soundness value (%) ASTM (1990) 6 2.25 0.87

Micro-deval value (%) TS EN1097-1 (2002) 2 19.60 0.25

Mill abrasion resistance indexc, ks (%) CIRIA/CUR (1991) 2 0.0039 0.001

Point load strength index, Is (50) (MPa) ISRM (1985) 8 1.86 0.92 1.43 0.57

Fracture toughnessd (MPa.m1/2) Bearman (1999) 8 0.39 0.19 0.30 0.12

Uniaxial compressive strength (MPa) ISRM (1981) 10 35.70 1.99 26.90 3.51

Sonic velocitye (m/s) ISRM (1981) 180 4806.48 645.70 5219.69 689.14

Schmidt rebound hardnessf ISRM (1981) 10 61.00 3.39 58.00 4.57

Los Angeles abrasiong (%) ASTM (1989) 2 13.51 0.01 14.82 0.01

Aggregate impact value (%) BSI (1990a) 2 16.79 1.75 18.25 0.10

Aggregate crushing value (%) BSI (1990b) 2 18.11 0.65 19.62 0.51

Modified aggregate impact value (%) BSI (1990a) 2 17.84 0.07

10% fines value (kN) BSI (1990c) 1 255.52 222.14

a Standard deviationb Determined from methylene blue adsorption testc Determined from micro-deval testd Determined from Is (50) using correlation factore Pundit-plus 500-kHz transducers are usedf L-Type Schmidt hammer is usedg Loss after 1,000 revolution

Environ Geol (2008) 53:12351247 1237

123

with secondary calcite. It also includes fewer amounts of

oolites. The cement in the limestone is formed by sparitic

calcite. Although the lower level of the quarry also consists

of limestone, it is the weakest level. It is light brown

to beige, fine-grained, slightly weathered, biomicritic

limestone with some fossil fragments. Oolite and pisolite

contents at the lower level decrease in the quarry. This unit

locally contains clayey matrix.

Engineering geological properties of the limestones

Evaluation of the engineering geological properties of the

four limestones (Degirmencayi, Tirtar upper, middle, and

lower levels) is based on the field observations and labora-

tory tests. For the laboratory tests, 50 block samples from the

Tirtar quarry and 30 block samples from the Degirmencayi

quarry were taken. A number of cubic samples with

5cm 5cm dimensions and crushed samples of suitable si-zes were prepared from those block samples. The laboratory

tests included the determination of dry and saturated unit

weights, effective porosity, water absorption, saturation

coefficient, methylene blue adsorption, wet-dry loss, freeze

thaw loss, magnesium sulphate soundness, micro-deval

abrasion, Los Angeles abrasion value, slake durability index,

point load strength index, fracture toughness, sonic velocity,

dry and saturated uniaxial compressive strengths, aggregate

impact value, aggregate crushing value and 10% fines value.

Table 2 Index properties of the Tirtar upper level limestone


for testing

Number

of tests

Dry


Mean SDa



Water absorption under atmospheric pressure-by

weight (%)

TS 699 (1987) 155 1.38 0.93


volume (%)

TS 699 (1987) 155 3.54 2.19



Saturation coefficient TS 699 (1987) 155 0.73 0.14



Wetdry loss (%) ASTM (1992) 6 1.48 0.58




Micro-deval index, MDE (%) TS EN1097-1 (2002) 2 22.20 4.46










Modified aggregate impact value (%) BSI (1990a) 2 21. 71 0.07

10 % fines value (kN) BSI (1990c) 2 236.44 171.86


1238 Environ Geol (2008) 53:12351247

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The strength related tests were performed in dry and satu-

rated conditions. They were performed according to ISRM

(1981), RILEM (1980), TS699 (1987) and TS EN1097-1

(2002). The test results for the four limestones are given in

Tables 1, 2, 3 and 4.

The field studies involved the assessment of the rock

mass properties. The scanline surveys were performed in

accordance with Priest (1993). The dominant discontinuity

sets are found using computer program called DIPS

5.0 (1999). The description of rock material and mass

characteristics is based on Anon (1977), BSI (1981) and

ISRM (1981). The survey results are presented in Tables 5,

6 and 7.

Quality and durability evaluations of the armourstones

Performance of armourstone in a breakwater is directly

related to the long-term structural durability of the ar-

mourstone used in coastal protection (Clark 1988). This

long-term durability can be assessed through field obser-

vations and experimental laboratory data (CIRIA/CUR

1991; Smith 1999). In this study, quality evaluation of the

limestones is done on the basis of CIRIA/CUR (1991)

criteria, Rock Engineering Rating System (RERS) of

Lienhart (1998), the rock durability index of Fookes et al.

(1988), average pore diameter, saturation coefficient of

Schaffer (1972), and wet-to-dry strength ratio of Winkler

Table 3 Index properties of the Tirtar middle level limestone


for testing

Number

of tests

Dry


mean SDa




weight (%)

TS 699 (1987) 40 4.77 1.72


volume (%)

TS 699 (1987) 40 10.44 3.52






Wetdry loss (%) ASTM (1992) 6 3.54 0.89















10 % fines value (kN) BSI (1990c) 1 169.20 123.09


Environ Geol (2008) 53:12351247 1239

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(1986). The results obtained are compared with the field

performances of the four armourstones.

CIRIA/CUR (1991) classification is based on the

laboratory and field tests of the armourstone. This system

represents the outlines of the marginal values of rocks

for different tests. The CIRIA/CUR (1991) classifications

for the limestones are given in Tables 8, 9, 10 and 11.

The strength-related parameters in the tables belong to

saturated conditions, only. The CIRIA/CUR (1991)

classification for the four limestones belonging to two

quarries indicates that both the Degirmencayi and Tirtar

upper level limestones are generally marginal to good in

quality, whereas the Tirtar middle level limestone is poor

to good and the Tirtar lower level limestone is poor to

marginal.

Lienhart (1998) suggests RERS consisting of various

complex processes for the evaluation of quality of an

armourstone. These processes consider inspection, pro-

duction methods and testing steps with their related sub-

factors. However, the entire process may be viewed as a

combination of rock engineering matrices, in which the

sum of all corresponded values is accepted as the overall

rating. These are three main matrix groups (processes) that

affect the quality of armourstones. They include geological

processes (lithology, regional in-situ stress, weathering

grade, discontinuity analysis and groundwater conditions),

Table 4 Index properties of the Tirtar lower level limestone


for testing

Number

of tests

Dry


mean SDa




weight (%)

TS 699 (1987) 110 5.58 2.75


volume (%)

TS 699 (1987) 110 12.38 5.30






Wetdry loss (%) ASTM (1992) 6 5.14 0.90















10% fines value (kN) BSI (1990c) 1 151.57 96.19


1240 Environ Geol (2008) 53:12351247

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production/construction processes (production method,

rock quality, set-aside time and block integrity), in-service

processes (petrography, sonic velocity, point load strength,

Schmidt impact resistance, Los Angeles abrasion, specific

gravity, water absorption, adsorption/absorption, magne-

sium sulphate soundness, freezethaw loss and wetdry

loss). A typical overall rating using RERS for the Degir-

mencayi limestone is presented in Table 12. Based on the

RERS of Lienhart (1998), the overall rating of the Degir-

mencayi limestone is 3.19 (good), the Tirtar upper level

limestone 3.20 (good), the Tirtar middle level limestone

2.71 (marginal) and the Tirtar lower level limestone 2.48

(marginal), respectively.

The factors affecting the rock durability in marine

environments are mainly originated by the physical struc-

ture of the armourstone (Dibb et al. 1983). The rock

durability index of Fookes et al. (1988) is one of the most

commonly used approaches for analysing the performance

of geomaterials to be used in a coastal structure. The index

can be applied for static and dynamic conditions that are

valid for breakwaters. The static rock durability index

(RDIs) is better suited to underlayer and core of the

breakwater, whereas the dynamic rock durability index

(RDId) is applied for armour layer of the breakwater

(Fookes et al. 1988). RDIs is expressed as follows:

RDIs = Is50 0.1(SST + 5 Wab)qssd

Table 5 Properties of the discontinuities in the Degirmencayi lime-stone

Discontinuity

properties

Bedding plane Joint 1

Orientation 005/5 130/68

Spacing 60 cm2 m

(wide)

210 m

(very wide to

extremely wide)

Persistence >20 m

(Very high)

1020 m (High)

Aperture 0.10.25 mm

(Tight)

0.10.25 mm

(Tight)

Roughness Rough planar

Wall Strength Strong

Weathering Slightly weathered

Infilling Clay

Seepage None

Number of sets 2

Block size (Max),

(Min), (V80)a

(6)(0.6)(4.8)

Volumetric joint

count (Jv) (joints/m3)

Not applicable due to two

discontinuity sets

Block shape Not applicable due to two

discontinuity sets

a Assessed

Table 6 Properties of the discontinuities in the Tirtar upper levellimestone

Discontinuity

properties

Bedding

plane

Joint 1 Joint 2

Orientation 225/10 190/36 085/80

Spacing 60 cm2 m

(wide)

26 m (very

wide)

20 cm2 m

(moderate

to wide)

Persistence >20 m (Very

high)

1020 m (High) 310 m

(Medium)

Aperture 0.13 mm

(Tight)

0.13 mm

(Tight)

0.13 mm

(Tight)

Roughness Rough

planar

Smooth

planar

Rough

planar

Wall strength Strong

Weathering Slightly to moderately to weathered

Infilling Clay

Seepage None

Number of sets 3

Block size (Max),

(Min), (V80)*

(5)(0.5)(4.6)

Volumetric joint

count

(Jv) (joints/m3)

0.7 (very large blocks)

Block shape Blocky

a Assessed

Table 7 Properties of the discontinuities in the Tirtar middle andlower level limestones

Discontinuity

properties

Bedding

plane

Joint 1

Orientation 228/8 083/85

Spacing 20 cm2 m

(Moderate

to wide)

60 cm2 m

(Wide)

Persistence 1020 m (High) 13 m (Low)

Aperture 1 m

(Extremely wide

to cavernous)

Roughness Rough planar

Wall strength Medium strong

Weathering Slightly to moderately weathered

Infilling Clay

Seepage None

Number of sets 2

Block size (Max),

(Min), (V80)a

(2.4)(0.07)(1.8)

Volumetric joint count

(Jv) (joints/m3)

Not applicable due to two

discontinuity sets

Block shape Not applicable due to two

discontinuity sets

a Assessed

Environ Geol (2008) 53:12351247 1241

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Table 8 Quality evaluation system of the Degirmencayi limestone by CIRIA/CUR (1991)

Properties CIRIA/CUR Criteria Degirmencayi

limestoneExcellent Good Marginal Poor

Dry density (t/m3) 2.9 2.62.9 2.32.6 2.3 2.42Water absorption (%) 0.5 0.52.0 2.06.0 6.0 3.31Magnesium sulphate soundness (%) 2 212 1230 30 4.56Freezethaw (%) 0.1 0.10.5 0.52.0 2.0 1.25Methylene blue absorption (g/100 g) 0.4 0.40.7 0.71.0 1.0 0.30Fracture toughnessa (MPa.m1/2) 2.2 1.42.2 0.81.4 0.8 0.33Point load strength index (MPa) 8.0 4.08.0 1.54.0 1.5 1.56Saturated dynamic crushing value (%) 12.0 1220 2030 30 19.62Mill abrasion resistanceb, ks (%) 0.002 0.0020.004 0.0040.015 0.015 0.0039Block integrity drop test, Id (%) 2 25 515 15 25a Assessed from point load strength index testb Assessed from micro-deval test

Table 9 Quality evaluation system of the Tirtar upper level limestone by CIRIA/CUR (1991)

Properties CIRIA/CUR criteria Tirtar upper level

limestoneExcellent Good Marginal Poor

Dry density (t/m3) 2.9 2.62.9 2.32.6 2.3 2.64Water absorption (%) 0.5 0.52.0 2.06.0 6.0 3.54Magnesium sulphate soundness (%) 2 212 1230 30 8.59Freezethaw (%) 0.1 0.10.5 0.52.0 2.0 1.50Methylene blue absorption (g/100 g) 0.4 0.40.7 0.71.0 1.0 0.30Fracture toughnessa (MPa.m1/2) 2.2 1.42.2 0.81.4 0.8 0.32Point load strength index (MPa) 8.0 4.08.0 1.54.0 1.5 1.52Saturated dynamic crushing value (%) 12.0 1220 2030 30 29.25Mill abrasion resistanceb, ks (%) 0.002 0.0020.004 0.0040.015 0.015 0.0045Block integrity drop test, Id (%) 2 25 515 15 25a Assessed from point load strength index testb Assessed from micro-deval test

Table 10 Quality evaluationsystem of the Tirtar middle level

limestone by CIRIA/CUR

(1991)

a Assessed from point load

strength index testb Assessed from micro-deval

test

Properties CIRIA/CUR criteria Tirtar middle

level limestoneExcellent Good Marginal Poor

Dry density (t/m3) 2.9 2.62.9 2.32.6 2.3 2.22Water absorption (%) 0.5 0.52.0 2.06.0 6.0 4.77Magnesium sulphate soundness (%) 2 212 1230 30 9.49Freezethaw (%) 0.1 0.10.5 0.52.0 2.0 1.95Methylene blue absorption (g/100 g) 0.4 0.40.7 0.71.0 1.0 0.43Fracture toughnessa (MPa.m1/2) 2.2 1.42.2 0.81.4 0.8 0.20Point load strength index (MPa) 8.0 4.08.0 1.54.0 1.5 0.95Saturated dynamic crushing value (%) 12.0 1220 2030 30 36.52Mill abrasion resistanceb, ks (%) 0.002 0.0020.004 0.0040.015 0.015 0.0079Block integrity drop test, Id (%) 2 25 515 15 515

1242 Environ Geol (2008) 53:12351247

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where, Is(50) = Average of dry and saturated point load

strength index (ISRM 1985) SST = Magnesium sulphate

soundness at 5th cycle (Hosking and Tubey 1969)

Wab = Water absorption at atmospheric pressure (BSI

1975; TS699 1987) qssd = Saturated surface dry relativedensity (BSI 1975; ISRM 1981).

A tentative estimation of the potential durabilities of

rocks based on the static rock quality index is given in

Table 13. The calculated RDIs values of the Degirmencayi,

Tirtar upper level, Tirtar middle level and Tirtar lower

level limestones are 3.63 (poor), 2.56 (Marginal), 6.69

(Poor), 11.69 (Poor), respectively.

RDId is expressed as follows:

RDId 0:1MAIV 5Wab=qssd

where, MAIV = Modified aggregate impact value (Hosking

and Tubey 1969), Wab = Water absorption at atmospheric

pressure (BSI 1975; TS699 1987), qssd = Saturated surfacedry relative density (BSI 1975; ISRM 1981).

A tentative estimation of the potential durability of

rocks based on the dynamic rock quality index is given

in Table 14. The calculated RDId values of the Degir-

mencayi, Tirtar upper level, Tirtar middle level and

Table 11 Quality evaluationsystem of the Tirtar lower level

limestone by CIRIA/CUR

(1991)

a Assessed from point load

strength index testb Assessed from micro-deval

test

Properties CIRIA/CUR criteria Tirtar lower

level limestoneExcellent Good Marginal Poor

Dry density (t/m3) 2.9 2.62.9 2.32.6 2.3 2.31Water absorption (%) 0.5 0.52.0 2.06.0 6.0 5.58Magnesium sulphate soundness (%) 2 212 1230 30 23.14Freezethaw (%) 0.1 0.10.5 0.52.0 2.0 11.51Methylene blue absorption (g/100 g) 0.4 0.40.7 0.71.0 1.0 0.71Fracture toughnessa (MPa.m1/2) 2.2 1.42.2 0.81.4 0.8 0.14Point load strength index (MPa) 8.0 4.08.0 1.54.0 1.5 0.65Saturated dynamic crushing value (%) 12.0 1220 2030 30 47.21Mill abrasion resistanceb, ks (%) 0.002 0.0020.004 0.0040.015 0.015 0.00152Block integrity drop test, Id (%) 2 25 515 15 515

Table 12 RERS assessment of the Degirmencayi limestone

Criteria Quality rating Rating value Cause-effect rating Index

(d/dmean)Weighted rating

(c x e)Excellen = 4 Good = 3 Marginal = 2 Poor = 1

Lithological classification 3 11.31 0.74 2.22Regional in situ stress 4 14.14 0.93 3.72Weathering grade 3 14.14 0.93 2.79Discontinuity analysis 4 18.38 1.20 4.8Groundwater conditions 4 14.14 0.93 3.72Production method 3 15.56 1.02 3.06Rock quality 3 15.56 1.02 3.06Set-aside 3 13.43 0.88 2.64Block integrity 3 15.56 1.02 3.06Petrographic evaluation 4 18.38 1.20 4.8Sonic velocity 3 16.97 1.11 3.60Point load strength 3Schmidt impact resistance 3LA abrasion 4Specific gravity 1 15.56 1.02 1.69Water Absorption 1Adsorption/absorption 3MgSO4 3 15.56 1.02 2.37Freezethaw loss 2 Mean = 15.28Wetdry loss 2 Overall rating = 3.19

Environ Geol (2008) 53:12351247 1243

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Tirtar lower level limestones are 1.37 (Good), 1.06

(Good), 2.28 (Marginal), 2.63 (Marginal), respectively.

Average pore diameter is also considered to be an

important parameter for the freezethaw durability of

stones (Larsen and Cady 1969). They stated that the critical

pore size is 5 lm below which pore water cannot bedrained out of the stone. Therefore, stones having average

pore size less than 5 lm are susceptile to frost damage. Theaverage pore diameters of the Degirmancayi and the Tirtar

limestones are obtained from the intrusion data of the

mercury porosimeter. They are 0.10 lm for the Degir-mencayi, 0.02 lm for the Tirtar upper level, 0.13 lm forthe Tirtar middle level and 0.12 lm for the Tirtar lowerlevel limestones. These results are showed that all samples

are susceptile to frost damage.

Saturation coefficient (S) of a stone is the ratio between

the natural capacity of a stone to absorb water after com-

plete immersion under atmospheric pressure for a definite

time, and its total volume of the pores that is accessible to

water. A stone with very high saturation coefficient may be

deteriorated by freezethaw activity (RILEM 1980).

Therefore, this value will be helpful to evaluate the dura-

bility of the stone in freezethaw situation. The value of

saturation coefficient can mostly vary between 0.4 and 0.95

(BRE 1983). A saturation coefficient greater than 0.8,

indicates low durability susceptible to frost activity

(Schaffer 1972 and TS2513 1977). However, many stones

have saturation coefficient in the range of 0.660.77. In this

range, the saturation coefficient gives an unreliable guide

(Anon 1975 and BRE 1983). The saturation coefficient of

the Degirmencayi limestone is 0.82. This value indicates

that the Degirmencayi limestone has a low durability

(susceptible to frost activity). The saturation coefficient of

the Tirtar upper level limestone is 0.73. This value indi-

cates that the Tirtar upper level limestone has a high

durability (resistant to frost activity). The saturation coef-

ficient of the Tirtar middle limestone is 0.78, which is al-

most in the unreliable range and also in or near to frost

susceptibility boundary. The saturation coefficient of the

Tirtar lower level limestone is 0.95 which indicates a low

durability (susceptible to frost activity). Therefore, by a

Table 13 Tentative static durability estimation of rocks (Fookeset al. 1988)

RDIs value Durability class

2.5 Excellent2.5 to (1) Good

(1) to (3) Marginal

conservative approach, except the Tirtar upper level lime-

stone, the other limestones may be considered to be frost

susceptible based on the saturation coefficient.

Swelling and non-swelling clay in stone tends to attract

water when exposed to moisture. The strength of the stone

can be reduced significantly due to the presence of mois-

ture. Winkler (1986, 1993) suggested that the wet-to-dry

strength ratio based on the modulus of rupture or the uni-

axial compressive strength or the tensile strength is a good

and rapid method of testing the durability of a stone in use

as a durability index. In this study, the durability indexes of

the Degirmancayi and the Tirtar limestones are evaluated

based on the saturated and dry uniaxial compressive

strength of the rocks (Fig. 4). The wet-to-dry strength ratio

of the Degirmancayi, Tirtar upper level, Tirtar middle level

and Tirtar lower level limestones are 75, 76, 67 and 62,

respectively. This reveals that the Degirmencayi and Tirtar

upper level limestones have very good to good durability,

but the Tirtar middle level limestone has good durability

and the Tirtar lower level limestone poor durability.

A summary table related to the durability assessments of

the armourstones is presented in Table 15. As can be seen

from the table, different durability assessment methods

give different results. However, the field observations by

checking the performances of the armourstones in both

harbours indicate that the Degirmancayi and Tirtar upper

level limestones showed rather good performances

(Figs. 5, 6). On the other hand, the Tirtar middle and lower

level limestones were readily disintegrated (Fig. 7) after a

few months. For this reason, they are not used anymore.

Therefore, they have poor performances.

The comparison between varies laboratory-based dura-

bility and field performances reveal that CIRIA/CUR,

RDId, RERS, and wet to dry strength ratio predict the

armourstone durability better than RDIs, average pore

diameter and saturation coefficient. No significant further

deterioration is expected for the Degirmancayi and Tirtar

upper level limestones in the breakwaters. However, the

Tirtar middle and lower level armourstones with poor field

and laboratory performances should not be used for the

protection of any marine structures.

Based on the outcomes of this study, it can be stated that

if a new quarry is to be opened containing a variety of

limestones, then the CIRIA/CUR, RDId, RERS, and wet to

dry strength ratio methods should be used to select which

rock type to use for armourstone, because these tests have

been shown to be the best predictors of durability. On the

other hand, the RDIs, average pore diameter and saturation

coefficient methods should not be used since they are not

good predictors.

Conclusions and recommendations

Systematic tests were performed in this study to assess the

quality and durability of the four limestones used as

armourstones in Mersin and Kumkuyu harbours, and the

Fig. 5 The Degirmencayi limestone blocks after 2 years of service inthe Mersin harbour

Fig. 6 A close-up view of the Tirtar upper level limestone used inKumkuyu harbour

Fig. 7 Tirtar middle and lower level limestones after a few months ofservice in Kumkuyu harbour

Environ Geol (2008) 53:12351247 1245

123

field and laboratory performances of the rocks were

compared. The Degirmancayi and Tirtar upper level

limestones showed good performances whereas the Tirtar

middle and lower level limestones presented rather poor

performances. Among the durability assessment methods,

CIRIA/CUR, RDId, RERS, and wet to dry strength ratio

give better results if compared with their field perfor-

mances. However, RDIs, average pore diameter, and sat-

uration coefficient yield poor performances. Further

systematic studies on other rock types with known site

performances are expected to provide valuable data which

may be used to test and improve the available quality and

durability assessment methods.

Acknowledgments This study is financially supported byTUB_ITAK Project (104Y178). The authors gratefully acknowledgeMuge Akin for her valuable support during field and laboratory

studies. The authors would also like to express their thanks to the

anonymous reviewers for their constructive comments and sugges-

tions on the manuscript.

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Quality and durability assessments of the armourstones for two rubble mound breakwaters (Mersin, Turkey)AbstractIntroductionGeological settingEngineering geological properties of the limestonesQuality and durability evaluations of the armourstonesConclusions and recommendationsAcknowledgmentsReferences

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