ORIGINAL ARTICLE

A geological and geotechnical investigation of the settlementarea of Zumrut Building (Konya, Turkey) which caused 92fatalities due to its collapse

Adnan Ozdemir

Received: 24 November 2006 / Accepted: 23 April 2007 / Published online: 19 June 2007

� Springer-Verlag 2007

Abstract This study examines the local geological con-

ditions and soil structure as possible causes of the collapse

of the Zumrut Building 2 February 2004. This catastrophe

resulted in 92 fatalities and 35 injuries. This study also

examines other views which claim weak soil structure,

elastic and consolidation settlement of soil and excessive

groundwater extraction as well as subsidence resulting

from the underground silt erosion as possible factors.

Zumrut Building was constructed on normally consoli-

dated, low plasticity clay. The underground water table was

30 m in depth. The internal friction angle of soil was 8�–

30�, its cohesion was between 34 and 127 kN/m2 and

standard penetration test numbers varied between 11 and

50. The underground water level beneath Zumrut Building

had risen 4.5 m since its construction. Therefore the claim

that subsidence resulting from the decrease of underground

water level contributed to the collapse is incorrect. Sec-

ondly the settlement, resulting from the filling up of the

pores created by the silt receding with the underground

water, was 4.4 mm in total, and attributing this as the

primary cause of the collapse is also incorrect. Soil prop-

erties, in situ and laboratory test results showed that the

existing and/or expected settlement and the differential

ground settlement in the Zumrut building vicinity had the

potential to cause structural damage. The tensile stresses

caused by differential settlements recorded here are

thought to be an indicator, but not the main cause con-

tributing to the collapse of the building. The Zumrut

Building collapse was due to several compounding mis-

takes during the construction phase. These were geotech-

nical and other project faults and the use of low quality

construction materials. The resulting catastrophe caused 92

fatalities, 35 injuries and a material loss of approximately

US$7 million.

Keywords Building collapse � Soil settlement �Soil � Zumrut Building � Konya � Turkey

Introduction

Zumrut Building was a 11 storey building located in

Kerkuk Avenue in Selcuklu Town of Konya, Turkey

(Fig. 1). On 2 February 2004 at 20:15 p.m the building

collapsed (Figs. 1, 2). The collapse was of very short

duration, approximately 30–45 s, resulting in the death of

92 people, 35 injuries and substantial property loss.

There have been various suggestions attributing the

cause of the collapse to such things as structural weakness,

project faults, structural modifications which were carried

out to the building, an explosion in the heating boiler, the

presence of weak soil structure, differential ground settle-

ment, excessive water being pumped from the ground, and

the settlement created when the silt material was also

extracted together with the underground water.

In this study, various suggestions as to the cause of the

collapse relative to local geological and ground conditions

were researched. Excessive underground water recession

and the effect of erosion of silt were also considered. The

soil study which was carried out previously on profiles of

soil in the vicinity of Zumrut Building was examined and a

more thorough study on these soil profiles was performed.

This study highlights the importance of geological and

soil conditions of the area (Fig. 1) which may have been

contributing factors to the collapse. By understanding the

A. Ozdemir (&)

Geological Engineering Department,

Selcuk University, Konya, Turkey

e-mail: aozdemirkonya@hotmial.com

123

Environ Geol (2008) 53:1695–1710

DOI 10.1007/s00254-007-0776-9

causes of this disaster we hope that better standards for

robust and secure construction will be set up in the future.

Investigation methods

In this investigation, first in situ and later laboratory,

studies were done. This study was based on in situ and

laboratory tests and the structural project evaluation and

interpretation. The detailed information on this subject is

presented below.

Geology of the Zumrut Building settlement

area vicinity

The Konya urban settlement area lies on Pleistocene aged

Konya and Karahuyuk formations as well as Miocene–

Pliocene aged Ulumuhsine and Kucuk Muhsine formations

(Fig. 3). Ulumuhsine formation consists of white, grey and

yellow limestone, clayey limestone, marl, conglomerate,

sandstone and mud. The thickness of the unit that is on the

surface of the western and northern part of Konya varies

and in several parts and reaches up to 1,000 m. There is a

continuous, lateral and vertical, transition between these

formations. The Kucuk Muhsine formation was formed of

tuff, tuffite, agglomerate and volcanic sandstone. The

formation had been formed by lateral and vertical transi-

tions from lacustrine, fluvial and terrestrial deposits. The

exposed region on the northwest of Konya was cut by an

andesite volcanism. This formation was established by the

accumulation of volcanic material from lake and/or land.

Konya and Karahuyuk formation are composed of loose

clay, silt, sand and gravel (Fig. 5). Karahuyuk formation is

composed of very young alluvial deposits.

Zumrut Building was constructed on the Pleistocene

aged Konya formation. Konya formation is composed of

uncemented, loose structured soil and, from place to place,

contains caliche formations, formed of clay, silt, sand and

gravel mixture. Loose deposits were formed by materials

carried by the streams feeding the lake which once existed

in the urbanised area of Konya. These deposits were

accumulated in the upper, middle or lower locations of the

stream, or in its sides or flood plains. Some also were

deposited on the lake sides and inside the lake. It is pos-

sible to see evaporitic deposits and caliche cemented levels

within these deposits as a result of continuous change in the

underground water table and the hot environment. As the

base topography is mountainous, the thickness of the loose

deposits varies greatly. Its value on the western and

northern parts of the urban areas of Konya is 0 m, whereas

around Zumrut Building reaches up to 140 m.

Because of the different dynamic environments stated

above and the changing stream flow regimes feeding the

lake, the ground around Konya’s populated region is

diverse. The soil in this area varies greatly in very short

intervals. The complex structure is a result of loose

deposits and environmental changes.

Most of the Konya’s settlement area is established on

sand, sandy silt, silt, clay and sometimes gravel in which

there is continuous lateral and vertical transition between

granulometries of sediments. These loose deposits with

different mechanical characteristics may behave differently

under pressure and may result in local failure, collapse,

swelling, as well as ground settlements.

Decrease in the underground water level

and silt erosion by piping

In the urbanised area of Konya, the numerous wells opened

under the buildings, or in the gardens by locals or in several

locations by the municipality, led to an uncontrolled

extraction of underground water. When pumping up water,

silt is also extracted inadvertently and this resulted in an

increase in the soil settlement potential. It is claimed that

settlement in the ground resulting from holes created by the

removal of silt resulted in the collapse of the building.

The underground water table map of the Zumrut

Building region, for the year 1994 (when the building was

constructed) and the year 2004 (when the collapse

Fig. 1 Location of Zumrut Building

1696 Environ Geol (2008) 53:1695–1710

123

occurred) is also presented. Data supplied by the munici-

palities’ wells with names P1/21, Musalla, P122, P123, and

Numune Hospital were used for preparing the underground

water table (Fig. 4). The 1994 underground water level

measurement values used in the water table map were

obtained from the Municipality of Konya, and underground

water level measurements were done by the author on 12

February 2004. An underground water table map is given

in Fig. 4.

As it can be seen from the underground water table map,

the groundwater flow direction of southwest in 1994,

turned approximately to the south by 2004. In the locality

of Zumrut Building, the underground water table measured

984 m in 1994 and 988.5 m in 2004. The water table had in

effect risen by 4.5 m when compared with the previous

levels. The underground water level increase around

Zumrut Building proves the invalidity of the claims stating

that underground water level decrease was effective in the

collapse of the building.

Furthermore, it was found that there is around 14 ppm

silt erosion or recession through water pumping from the

wells of that locality (Nalbantcılar et al. 2005). There were

approximately 200 inhabitants living in the building and an

average of 60 m3/person of water was extracted in a year

from the underground to meet this demand. In total,

12,000 m3 of water was pumped out from the underground

wells annually. If it is assumed that there is 4 ppm silt

erosion with water by weight, yearly 0.048 tons and in

30 years 1.44 tons of silt is pulled out. When silt specific

gravity is accepted as 2.6, the volume of silt pulled out with

underground water in 30 years is around 0.55 m3. Zumrut

Building settlement area is 500 m2. If 0.55 m3 of silt is

Fig. 2 The view of Zumrut

Building before and after

collapse

Environ Geol (2008) 53:1695–1710 1697

123

extracted from underground in 30 years and is evenly

distributed over this area, it is determined that the settle-

ment height becomes 1.1 mm relative to silt erosion. If the

silt erosion is assumed to occur on ¼ of the building’s area

in one corner, 4.4 mm of settlement is expected. Even if

this entire small amount of settlement were under the

foundation, it would not effectively damage the building.

On the other hand, from the foundation level, the depth of

underground water table is approximately 24.5 m. There-

fore, the silt must erode below the underground water level.

Fig. 4 Map of groundwater level

Fig. 3 Simplified geological

map of Konya residential area

Fig. 5 Pressure bulb for the foundation of Zumrut Building

1698 Environ Geol (2008) 53:1695–1710

123

It is obvious that the effect of the pores caused by silt

erosion, at a depth of 25 m or more under the foundation

will be reduced by the thick ground layer above the

underground water table and the settlement here will be

ineffective under the foundation. Even if all the silt were

extracted from a region, an underground void of 0.55 m3

would be filled by loose particles falling from the 25 m

thick soil layer. This would not by itself pose a danger to

the foundation. By doing conservative calculations, it can

be concluded that there is no significant influence of soil

settlement caused by silt erosion, which can lead to the

collapse of the building.

Geotechnical investigation

One hour after the collapse of Zumrut Building, a visual

observation of the site was done. No perceivable ground

settlement, swelling or sliding were observed. It was decided

that further studies were needed to investigate the ground

under the building. Five geotechnical bore holes were drilled

in order to ascertain if there were any adverse ground con-

ditions that may have been responsible for the collapse.

Determination of borehole locations and their depths

Zumrut Building collapsed 5 years after its completion and

10 years after the commencement of construction. Four

boreholes were planned around the building’s base area;

hoping to collect data about the effect of the building’s

weight on the surroundings. There was a possibility that

boreholes drilled further away from the building’s base

would not provide the correct data since ground character-

istics could be different there. Boreholes were drilled close to

the structure at appropriate points subjected to the least

weight effect of the building. Pressure bulb calculations were

used to find suitable borehole locations and their depths.

Zumrut Building’s foundation depth was 4.5 m; the total

location area was 25 · 20 = 500 m2, and the total weight

was computed to be 65,572 kN from the building project.

To transfer this load to the ground, a strip foundation

system with a width of 1.4 m was used. In the strip foun-

dation, the largest contact pressure was calculated to be

200 kN/m2. At a distance of 6 m from the centre of the

strip foundation towards the exterior of the building, it

decreased to 10 kN/m2 which is 5% of the loading pressure

(200 kN/m2) (Fig. 5). Again, 23 m below the surface;

vertical effective stress became 414 kN/m2 (soil unit

weight is accepted as 18 kN/m3). The ratio of stress in-

crease resulting from the building’s weight (10 kN/m2) to

the effective stress (414 kN/m2) at this point, is 2.4% (10/

414 kN/m2 = 0.024). Das (2000) states that the depth

where the effective stress ratio of stress increase falls to

5%, and Chen (1999) claims that the depth where loading

effect falls to 20%, can be taken as the analysing depth in

ground investigations. In order to take a conservative po-

sition, we determined the research boreholes’ depth to be

20 m, and the borehole locations 7 m away diagonally

from the building (5 m away perpendicular to the build-

ing’s corner edges).

Four boreholes (BH1, BH2, BH3, BH4) on the exterior

of the building’s base area on its diagonals, and one

borehole (BH5) inside the building’s base area, were dril-

led. During boring, progress was achieved without using

water and full core samples were taken from the ground.

Standard penetration tests were done on the boreholes at

1.5–2 m intervals. In BH5, in order to define the under-

ground water level, drilling was done up to a depth of

24.5 m (which is 29 m from the surface). The underground

water level was measured as 24.5 m from the surface under

the foundation (from the surface 29 m) 10 days following

the collapse of the building. Drilling locations are given in

Fig. 6, and its logs in Fig. 7.

On the disturbed samples taken from the five geotech-

nical boreholes; particle size analysis, Atterberg limits,

specific gravity, water content, and natural unit weight tests

and in addition to those applied on disturbed samples, on

undisturbed samples; triaxial unconsolidated undrained,

consolidation and unconfined compression tests were done.

Tests were carried out by General Directorate of State

Water Affairs Laboratories, Ankara. The levels of the

samples taken, the tests done and the results achieved

are given in Table 1, and from the consolidation test,

pressure versus coefficient of volume compressibility

changes are given in Fig. 8.

Geo-mechanical characteristics of Zumrut

Building settling soil

The evaluation of the cores achieved from the boreholes of

the Zumrut Building, together with logs prepared and

Fig. 6 Location of geotechnical boreholes

Environ Geol (2008) 53:1695–1710 1699

123

laboratory results shows that the ground has clay formation

in general. It can be determined that there are several levels

of clay and mixed clay sand and gravel, and as a result of

this, the soil is sandy, silty clay and low sandy clay, and

sometimes gravelly sandy clay. In certain levels with the

existence of carbonated cement; stiff, even hard levels

(caliche levels) were found. These levels with caliche were

cut especially in BH2 and BH5 boreholes. In certain sec-

tions (as at 8.5–9 m levels in BH5) undisturbed samples

couldnot be taken due to the high amount of gravel.

In general, the soil has low and medium plasticity, but in

BH5, between 8 and 8.5 m layers; clay with high plasticity

was also cut. The content of fines in the soil is generally

more than 70% whereas gravel ratio is less than 5%.

However, gravel ratio is 8% in BH2 at 12–12.5 m depth,

and at 19.5–20 m it increases up to 14%. The liquid limit is

around 38–40% in general, and it reaches up to 52% as

value in BH5. Plastic limit in the soil is around natural

water content. Soil liquidity index is less than one in

general, so the soil is in plastic state in consistency. The

plasticity index in the ground being between 15–18%

shows that the ground is composed of medium plasticity

clay and silt. Water saturation in the soil is more than 80%

in general, and mostly around 90%.

The soil at some levels (as in BH3) is saturated with

water, but at some (as in BH1) water saturation decreases

to around 60%. The soil liquid limit being less than 50%

and plasticity index being less than 25% indicate that the

swelling potential of the ground is low (less than 0.5%)

(O’Neill and Poormoayed 1980). The soil is normally

consolidated. The internal friction angle is between 8� and

30�, and undrained cohesion changes between 34 and

127 kN/m2. Swelling in the soil is between 0.2 and 0.6%

(0.3% on the average). The swelling percentages given in

Table 1 are in agreement with the ones defined by

consistency indexes.

Fig. 7 Geotechnical borehole

logs of Zumrut Building ground

1700 Environ Geol (2008) 53:1695–1710

123

Ta

ble

1R

esu

lts

of

lab

ora

tory

test

s

12

34

56

78

91

01

11

21

31

41

61

71

81

92

02

1

Item

no

Bo

reh

ole

no

Dep

th

(m)

Sam

ple

typ

e

<0

.07

5

mm

(%)

>4

.76

mm

(%)

Liq

uid

lim

it

LL

(%)

Pla

stic

lim

it

(PL

,

%)

Pla

stic

ity

ind

ex

(PI,

%)

Cla

ss

of

soil

(US

CS

)

Sp

ecifi

c

gra

vit

y

(Gs)

Nat

ura

l

un

it

wei

gh

t

(kN

/

m3)

Wat

er

con

ten

t

(%)

Vo

id

rati

o

(eo,

%)

Deg

ree

of

satu

rati

on

(S,

%)

Co

hes

ion

(cu,

kN

/

m2)

_ Inte

rcep

t

of

fric

tio

nal

ang

le

(/u

deg

rees

)

Un

con

fin

ed

com

pre

ssio

n

resi

stan

ce

(qu,

kN

/m2)

Pre

con

so-

lid

atio

n

pre

ssu

re

(Po,

kN

/

m2)

Sw

el-

lin

g

(%)

1B

H1

4.5

–5

D6

09

63

81

91

9C

I2

.68

19

.61

6.1

55

.67

8

2B

H1

6.5

–7

D7

59

94

52

22

3C

I2

.69

19

.52

1.2

63

.88

9

3B

H1

7–

7.5

UD

73

10

04

32

32

0C

I2

.69

19

.52

1.1

77

.07

42

08

.71

12

.70

.21

4B

H1

8.5

–9

D7

39

94

12

31

8C

I2

.71

18

.61

8.2

66

.07

5

5B

H1

11

.5–

12

D7

99

94

62

32

3C

I2

.74

18

.62

2.2

79

.17

7

6B

H1

15

.5–

16

UD

82

10

04

02

51

6C

I2

.73

18

.61

8.8

69

.87

49

91

5.9

13

2.3

0.5

8

7B

H1

17

.5–

18

D7

19

93

11

91

2C

L2

.73

18

.61

6.5

71

.96

3

8B

H1

19

.5–

20

D6

58

73

22

01

2C

L2

.71

17

.61

5.4

70

.95

9

9B

H1

21

.5–

22

D9

29

94

52

52

0C

I2

.72

18

.62

5.6

80

.88

6

10

BH

25

–5

.5D

58

99

38

18

19

CI

2.5

91

9.6

18

.05

1.3

91

11

BH

26

–6

.5U

D6

61

00

41

23

17

CI

2.6

51

9.6

17

.45

8.7

79

11

7.6

12

2.5

0.4

9

12

BH

27

–7

.5D

72

10

03

72

01

7C

I2

.67

19

.62

1.5

63

.09

1

13

BH

28

–8

.5U

D5

99

93

52

11

3C

L2

.69

19

.62

1.3

64

.88

89

7.0

20

5.8

0.2

14

BH

21

0–

10

.5D

86

10

04

52

52

0C

I2

.66

18

.62

7.5

80

.49

1

15

BH

21

2–

12

.5D

56

92

28

16

12

CL

2.7

02

1.6

12

.14

0.1

81

16

BH

21

4–

14

.5D

53

96

25

17

8C

L2

.69

20

.61

6.8

51

.88

7

17

BH

21

8–

18

.5D

69

98

34

22

12

CL

2.7

41

9.6

22

.97

0.1

90

18

BH

22

2–

22

.5D

89

10

04

22

51

7C

I2

.73

19

.62

6.1

73

.09

8

19

BH

37

–7

.5U

D6

49

63

42

01

4C

L2

.67

17

.61

4.3

72

.45

31

33

7.5

14

7.0

0.2

2

20

BH

37

.5–

8D

82

10

03

82

11

6C

I2

.65

19

.62

3.8

67

.49

4

21

BH

31

0–

10

.5D

79

98

48

25

23

CI

2.7

19

.62

2.3

66

.89

0

22

BH

31

2–

12

.5D

65

96

31

19

12

CI

2.7

21

.61

6.7

46

.09

8

23

BH

31

5–

15

.5U

D6

41

00

34

20

14

Cl

2.7

20

.62

2.6

60

.71

00

67

18

.91

8.6

0.6

0

24

BH

44

.5–

5D

76

98

42

23

19

CI

2.7

19

.62

1.3

63

.09

0

25

BH

47

–7

.5U

D8

11

00

36

24

13

CI

2.6

18

.61

5.6

63

.26

53

42

9.4

11

8.9

0.1

2

26

BH

49

–9

.5D

82

10

04

62

42

2C

I2

.71

9.6

21

.36

5.8

88

27

BH

41

1–

11

.5D

67

94

36

23

13

CI

2.7

18

.62

1.4

73

.27

9

28

BH

41

5–

15

.5D

64

95

33

18

27

CL

2.7

19

.61

9.5

62

.58

5

29

BH

41

7.5

–1

8D

68

99

36

21

15

CI

2.7

19

.62

0.0

59

.89

0

30

BH

41

9–

19

.5U

D8

31

00

41

23

18

CI

2.7

18

.62

0.9

72

.57

92

54

.81

17

.60

.29

31

BH

51

.5–

2D

73

96

41

22

19

CI

2.7

18

.62

5.4

80

.88

6

32

BH

52

–2

.5U

D6

29

83

52

01

4C

L2

.71

9.6

23

.16

7.7

91

68

10

.21

02

.90

.18

33

BH

54

–4

.5D

69

10

03

61

91

7C

I2

.71

9.6

22

.06

3.9

92

34

BH

56

–6

.5D

80

10

04

02

21

9C

I2

.71

9.6

22

.36

7.8

90

35

BH

58

–8

.5D

89

10

05

32

72

7C

H2

.71

9.6

23

.86

9.3

92

36

BH

58

.5–

9U

D6

29

93

02

01

0C

l2

.71

5.7

23

.91

1.4

56

74

20

.81

56

.80

.21

Environ Geol (2008) 53:1695–1710 1701

123

On the other hand, when overburden pressure correction

(Liao and Whitman 1985) is done, the change of the

standard penetration number (SPT) (Ncor) by depth is

analysed (Fig. 9). As a result of this analysis, in BH5 and

BH2, SPT numbers are found to be very high (>50), and in

BH3 (between 10 and 19 m depth) become very low. The

SPT number declines to 15 in BH1 between 8 and 12 m, in

BH3 between 10 and 19 m, and to 10 in BH4 between 12

and 16 m depth. After calculations, the SPT number

decreases to 12 in BH4 at 13 m depth. It can be concluded

that the soil in the research area varies considerably con-

sidering the high SPT numbers observed in BH5 and BH2

and the above mentioned low SPT numbers.

In order to make the comparison in an easier way,

correction of overburden pressure on SPT numbers and

energy correction (=0.75) as well as correction of rod

length and underground water level have been done. In this

study, overburden pressure correction was done according

to Liao and Whitman (1985), and the energy correction

coefficient accepted as 0.75 according to Skempton (1986).

Rod length and underground water level correction coef-

ficients were taken as 1, again according to Skempton

(1986). From these corrected SPT numbers, the weighted

average of corrected SPT numbers (N¢) for each well was

determined (Table 2). The changes in N¢ numbers on hor-

izontal plain of Zumrut Building settlement area and its

close surrounding are given in Fig. 10.

The soil allowable bearing capacity

The soil allowable bearing capacity according to corrected

SPT numbers (Ncor and N¢) was determined by the equa-

tions given below:

qa ¼ 0:14NcorqaSettlement qað Þ ¼ 25 mm½ � ð1Þ

(Budhu 2000)

qa ¼ 10:5N 0 ð2Þ

(Barnes 2000)

where

qa allowable bearing pressure (kN/m2)

Ncor corrected SPT numbers (Ncor = NCN),

N¢ corrected SPT numbers (N¢ = NCECNCRCW),

N field SPT numbers,

CE correction for energy (CE = 0.75) (Skempton 1986),

CN correction for overburden pressure (Liao and Whit-

man (1985),

CR correction for rod length (Skempton 1986),

CW correction for groundwater depth (CW = 1).

Soil allowable bearing pressures determined according

to the relations given above are given in Table 3.Ta

ble

1co

nti

nu

ed

12

34

56

78

91

01

11

21

31

41

61

71

81

92

02

1

Item

no

Bo

reh

ole

no

Dep

th

(m)

Sam

ple

typ

e

<0

.07

5

mm

(%)

>4

.76

mm

(%)

Liq

uid

lim

it

LL

(%)

Pla

stic

lim

it

(PL

,

%)

Pla

stic

ity

ind

ex

(PI,

%)

Cla

ss

of

soil

(US

CS

)

Sp

ecifi

c

gra

vit

y

(Gs)

Nat

ura

l

un

it

wei

gh

t

(kN

/

m3)

Wat

er

con

ten

t

(%)

Vo

id

rati

o

(eo,

%)

Deg

ree

of

satu

rati

on

(S,

%)

Co

hes

ion

(cu,

kN

/

m2)

_ Inte

rcep

t

of

fric

tio

nal

ang

le

(/u

deg

rees

)

Un

con

fin

ed

com

pre

ssio

n

resi

stan

ce

(qu,

kN

/m2)

Pre

con

s-

oli

dat

ion

pre

ssu

re

(Po,

kN

/

m2)

Sw

el-

lin

g

(%)

37

BH

51

0–

10

.5D

68

99

27

19

10

Cl

2.7

20

.61

7.0

54

.38

6

38

BH

51

2–

12

.5D

63

99

27

18

10

Cl

2.7

19

.61

6.7

56

.78

1

39

BH

51

4–

14

.5D

73

98

35

21

14

Cı

2.8

19

.62

0.6

69

.28

2

40

BH

51

6–

16

.5D

77

96

35

19

16

CI

2.7

19

.62

1.3

64

.89

0

41

BH

52

0–

20

.5D

82

10

03

82

11

7C

I2

.71

8.6

21

.07

3.6

78

1702 Environ Geol (2008) 53:1695–1710

123

Soil bearing capacity according to laboratory test results

is computed both relative to general shear failure of Terzaghi

bearing capacity equation (Budhu 2000) and by general

bearing capacity equation of Meyerhof (Meyerhof 1965).

The foundation’s width, length and depth were 1.4, 20 (strip

foundation) and 4.5 m, respectively. The factor of safety was

taken 3 for the calculations. Calculations were done

according to the data from each bore and, additionally, using

the internal friction angles obtained from triaxial unconsol-

idated undrained laboratory tests and in addition, using an

assumed 0� internal friction angle. Data used for calculations

and the computed results are given in Table 4.

As it can be seen from these results, when the internal

friction angle is accepted as 0�, soil allowable bearing

pressure changes between 253 and 65 kN/m2 according to

Terzaghi equation, and 384 and 98 kN/m2 according to

general bearing capacity equation. As it is shown in the Table

above, soil allowable bearing capacity values show quite a

lot of variance relative to ground characteristics and the

internal friction angle values. According to data achieved

from BH4 the borehole on the northern corner of the build-

ing, soil allowable bearing pressure is lower when compared

to the other sections. Soil allowable bearing pressure is

around 129 kN/m2. In BH2, low allowable bearing pressure

was achieved from laboratory tests. It is thought that this may

be the result of the level of sample taking and/or disturbance

occurring during sample taking or the preparation for the test

as the ground was very hard and caliche cemented.

Settlement of soil

Elastic settlement of soil under project loads

Average elastic settlement occurring in the Zumrut

Building foundation was computed by the Janbu et al.

(1956), Craig (1990) method. In the calculations, founda-

tion length (L) was 20 m, and the width (B) was 1.4 m.

Settlement layer thickness (H) was taken as building short

edge, which is 20 m. Soil undrained elasticity modulus (Es)

was determined relative to Es = 500cu relation depending

on cohesion (cu) (Das 2000). For the ground settlement

calculated in the building’s corners, cohesion (cu, kN/m2)

values of the samples taken from the boreholes closer to the

related corner are used. Foundation pressures applied in the

building’s corners (qs) were taken from building’s static

project. Other data and elastic settlements determined un-

der the foundation’s centre are given in Table 5. Distri-

bution of elastic settlements calculated on the building

foundation corners is again given in Fig. 11.

Consolidation settlement potential of soil under applied

foundation loads

The soil under the Zumrut Building’s foundations is

formed of clay with low plasticity, and is saturated with

water or close to saturation. Under current conditions, the

occurrence of consolidation settlement under the founda-

tion seems out of question. The ground consolidation

Fig. 8 Graphics of pressure vs. coefficient of volumetric compress-

ibility (mv)

Environ Geol (2008) 53:1695–1710 1703

123

settlement potential was calculated considering the

groundwater level change interval (groundwater table has

increased more than 4 m relative to the 1993 measure-

ments), and the water seepage into the ground in rainy

seasons and through artificial ways.

The loads used in calculating settlement and the stresses

that occurred because of these, were taken from the static

project (Fig. 12). The foundation area was divided into 43

divisions (Fig. 12). Over the 43 sub-areas, stresses oc-

curred under the foundation at 0.7 m (0.5B, where B is

width of foundation), 2.1 m (1.5B), 3.5 m (2.5B), 4.9 m

(3.5 B), 8.4 m (6B), and 16.8 m (12B) from the foundation

level were calculated at 16 points (points in circles) se-

lected on the whole foundation (Fig. 12). Stresses created

by the building load under the foundation within the

ground for different depths and different points are given in

Table 6 and Fig. 13.

Consolidation settlement was calculated at 16 points

selected on the foundation. In consolidation calculations,

laboratory test data of the samples taken from the borehole

closest to the calculation point was used. In other words,

laboratory test results of the samples taken from BH1 for

the points 3, 4, 7, 8, from BH2 for the points 1, 2, 5, 6, from

BH3 for the points 9, 10, 13, 14, and from BH4 for the

points 11, 12, 15, 16 were used. The consolidation calcu-Fig. 10 Distribution of the corrected SPT numbers (N¢) on the

Zumrut Building ground

Fig. 9 Variation of corrected

SPT numbers by depth

Table 2 Weighted averages of corrected SPT numbers on the

Zumrut building ground

Borehole Weighted average of

overburden pressure

correction done SPT

Numbers-Ncor

Weighted average of

overburden, energy and rod

length corrections done SPT

numbers-N¢

BH1 26 22.1

BH2 50 50

BH3 20.6 15.7

BH4 15.6 11.4

BH5 50 50

Table 3 Computed allowable bearing pressures (qa ) from field test

results

Borehole qa = 0,41Ncor(qa) (kN/m2)

(Budhu 2000)

qa = 10,5N¢ (kN/m2)

(Barnes 2000)

BH1 267 232

BH2 513 525

BH3 211 165

BH4 160 120

BH5 513 525

1704 Environ Geol (2008) 53:1695–1710

123

lations at a point, for sections closer to the surface from

levels closer to the surface, for deeper sections sample data

taken from deeper sections are used. For example, at point

1 from the section closer to the surface (up to 7.5 m depth),

ground sample was taken from the 6–6.5 m interval, and

for deeper sections (>7.5 m), from 9–9.5 m level ground

sample laboratory results were used. Compressible layer

thickness is taken as the building’s width. Consolidation

settlement calculations for point 1 are given in Table 7.

Calculated consolidation settlements were multiplied by

0.7 coefficient of correction (Tomlinson 1986) and cor-

rected consolidation settlements were determined. Calcu-

lated consolidation settlements are given altogether in

Table 8. Distribution of corrected consolidation settle-

ments under the foundation is given in Fig. 14.

Consolidation settlements under applied foundation

contact pressures and project soil allowable bearing

pressure (=171 kN/m2)

Soil settlement potential was calculated under applied

project foundation contact pressures and allowable soil

bearing pressure of Zumrut Building static project. The

ground under the foundation was divided vertically into 4

layers as 0–2 m, 2–4 m, 4–12 m, and 12–24 m for the

calculations. For the first two layers, consolidation test

data achieved from the sample closer to the surface is

used. For the following layers, data samples taken from

deeper parts were used. Ground settlements were calcu-

lated on the building corner points 1, 4, 13 and 16. In the

calculations, land and laboratory data of the samples ta-

ken from boreholes closer to these points were used. In

other words, at point 1 data taken from BH2, at point 4

from BH1, at point 13 from BH3 and at point 16 data

from BH4 were used. Calculations were done both under

project soil allowable bearing pressure (PAP) which is

171 kN/m2 pressure, and applied foundation contact

pressures in the project (APP) which are 201, 187, 197

and 197 kN/m2 for the points 1, 4, 13 and 16, respec-

tively. Calculated settlements were also corrected by

multiplying with 0.7. Elastic settlements (Se APP) under

APP at these points have already been defined (Table 5).

Again, elastic settlements (SeSAP) and consolidation set-

tlements (ScSAP) under suggested SAP which was defined

earlier as Zumrut Building soil allowable bearing pressure

(=120 kN/m2), and total settlements (STSAP) were calcu-

lated and given in Table 9.

Table 4 Computed allowable net bearing pressures (qa–net ) from

laboratory test results

Method-parameter Data

from

BH1

Data

from

BH2

Data

from

BH3

Data

from

BH4

Data

from

BH5

Unconsolidated

undrained

cohesion (cu)

(kN/m2)

99 54 133 34 68

Unit weight

(kN/m3)

19.5 19.6 18.6 19.1 19.1

Unconsolidated

undrained

internal friction

angle (/u) (o)

16 0 0 8 0 29 0 10 0

qa–net (from

Terzaghi’s

bearing capacity

equation)

(kN/m2)

574 188 103 417 253 1004 65 269 129

qa–net (from

Meyerhof’s

bearing capacity

equation)-kN/m2

740 286 156 553 384 1179 98 354 196

Table 5 Computed elastic settlements

Borehole Point Applied

pressure

(qs)

kN/m2

Cohesion

(kN/m2)

Elasticity

modulus

Eu = 500cu

kN/m2

Elastic

settlement

at center of

foundation (Si)

(mm) (Christian

and Carrier

1978)

BH1 4 187 104 26000 13

BH2 1 201 59 14750 24

BH3 13 197 133 33250 10

BH4 16 197 34 8500 40

BH5 � 6 197 68 17000 20

Fig. 11 Distribution of elastic settlements (mm) under Zumrut

Building corners

Environ Geol (2008) 53:1695–1710 1705

123

Discussion and conclusion

The results obtained from the analysis and research done in

Zumrut Building’s ground and the details related to their

discussion and conclusion are presented below.

The underground water table level of the region, where

the Zumrut Building is located, is determined as 984 m in

1994 and 988.5 m at the time the building collapsed. The

underground water flow direction had changed due to

underground water level increase of 4.5 m, and uncon-

trolled and unbalanced underground water use.

It is clear the idea that a decrease in the underground

water level had effected the collapse is proved to be invalid

because the underground water level actually increased.

According to conservative calculations, maximum

ground settlement is 4.4 mm, if the pores left by the silt

eroded with the underground water pumping under Zumrut

Building are filled with soil particles. Silt has been ex-

tracted from deeper than 25 m. By considering that the

pores occurred at 25 m and deeper would be filled by soil

particles at this level, it is clear that the settlement beneath

the foundation is less than 4.4 mm. Such data proves the

Fig. 12 The sketch of Zumrut Building foundation project, subdivi-

sion of the area, applied foundation pressure and certain points

selected on the foundation

Table 6 Pressures resulting from applied loads at 16 points on the

foundation and at different depths

Depth fi 0 0.5B 1.5B 2.5B 3.5B 6B 12B

Depth fi 0 0.7 m 2.1 m 3.5 m 4.9 m 8.4 m 16.8 m

Point number

1 201 49.3 44.7 39.7 34.6 29.4 23.2

2 182 79.1 61.4 55.5 52.8 52.2 39.5

3 174 83.1 71.3 60.9 55.3 45.7 37.2

4 187 47.9 43.2 37.9 33.7 29.3 25.2

5 198 96.1 72.5 59.9 53.5 46.2 31.4

6 161 120.8 105.0 92.8 81.2 68.1 49.9

7 156 116.4 95.5 84.7 74.4 68.0 44.9

8 200 94.9 73.2 60.3 54.1 47.0 32.7

9 197 95.6 77.6 63.9 56.0 45.2 31.0

10 169 124.1 103.4 89.4 81.5 69.5 43.7

11 169 124.7 104.5 92.3 81.4 69.1 43.5

12 198 96.5 78.9 65.1 56.5 41.1 30.5

13 197 47.8 43.7 37.8 33.9 29.1 23.1

14 190 82.5 72.0 63.8 55.7 49.7 36.4

15 183 87.5 76.4 65.6 58.0 47.2 32.4

16 197 48.0 44.5 38.0 34.3 29.2 23.0

B Foundation width which equals to 1.4 m)

Fig. 13 Pressures under different points on foundation and at various

depths (B is the foundation width which equals to 1.4 m)

Fig. 14 Corrected consolidation settlements (mm)

1706 Environ Geol (2008) 53:1695–1710

123

incorrectness of the thought claiming that erosion of silt

was effective in Zumrut Building collapse.

Konya city is built on Konya and Karahuyuk formation

composed of silty sand and gravel mixture presenting

lateral and vertical transitions in short distances. The

location of the Zumrut Building consists of low and med-

ium plasticity clay. From place to place high plasticity

levels can also be determined. The liquid limit is around

38–40% in general, where the plastic limit is 21%, and

natural water content is around the plastic limit. Water

saturation of the soil is more than 85%. The soil is hard in

general, but there are loose zones in between the layers. In

the soil, there are hard sections composed by inter linking

soil particles through carbonated cement. It is possible to

see these hard sections in the south–eastern corner of the

Zumrut Building. Swelling potential of the soil is low.

Internal friction angle of the soil is between 8� and 30�, and

cohesion changes between 34 and 127 kN/m2.

Soil weighted average SPT change between 11 and 50.

Low bearing capacity soil zone was determined between 9

and 12 m depth on especially the western corner of the

Zumrut Building. This depth range is between 10 and 18 m

in BH3, and between 10 and 20 m in BH4. On the northern

corner of the building, this soil zone starts from a deeper

section and continues sloping to the north. As it can be seen

by analysing Table 2, SPT decline in the Zumrut Building

foundation soil from south to north (Figs. 5, 9). High soil

SPT numbers on the south side of Zumrut Building show

that bearing capacity of the soil is high, settlement potential

is low, but on the northern side soil bearing capacity is

comparatively lower and settlement potential is higher.

It was found that net allowable bearing capacity of soil is

between 120 and 525 kN/m2 according to in situ tests, and

between 65 and 384 kN/m2 according to laboratory tests

results where the internal friction angle is accepted as 0�.

When the distribution of elastic settlement of the

Zumrut Building foundation base was analysed (Fig. 11); it

was determined that elastic settlement of the building was

40 mm at point 16 and 10 mm at point 13. The high dif-

ference in elastic settlements at points 16 and 13 may have

created tensile stresses between the related parts of the

building.

Fifty-six millimeters consolidation settlement potential

at point 1, and 221 mm at point 11 were determined by the

analysis of the Zumrut Building settlement potential map

determined under applied foundation contact pressures.

Besides, although it is not exactly known in what level

elastic and consolidation settlements are realised, the

existence of different settlement areas beneath the building

with approximately a fourfold difference were determined

Table 7 Consolidation settlement calculation for point 1 on the foundation

Do (m) D1 (m) c(kN/m3)

r’o

(kN/m2)

Dr(kN/m2)

r = Dr + ro

(kN/m2)

mv1 · 1.02 · 10–4

(m2/kN)

mv2 · 1.02 · 10–4

(m2/kN)

mv = (mv1 + mv2)/2

· 1.02 · 10–4

(m2/kN)

Sc = mv

(DD1)(Dr)

(mm)

4.5 0

5.50 1 19.60 107.80 48 156 1.6 1.29 1.445 14.14944

7.50 3 19.60 147.00 42 189 1.3 1.32 1.31 11.22408

9.50 5 19.60 186.20 34 220 1.03 1.15 1.09 7.56024

11.5 7 18.6 213.90 31 245 1.12 1.2 1.16 7.33584

13.5 9 21.6 291.60 29 321 1.27 1.27 1.27 7.51332

15.5 11 20.6 319.30 27 346 1.28 1.28 1.28 7.05024

17.5 13 19.6 343.00 26 369 1.28 1.28 1.28 6.78912

19.5 15 19.6 382.20 25 407 1.28 1.28 1.28 6.528

21.5 17 19.6 421.40 24 445 1.28 1.28 1.28 6.26688

23.5 19 19.6 460.60 23 484 1.27 1.18 1.225 5.7477

Total Sc = 80.16

Explanations: Do depth from surface, D1 depth from foundation base, c unit weight, r¢o initial effective stress, Dr stress increase, r total stress,

mv1 coefficient of volume compressibility for initial effective stress, mv2 coefficient of volume compressibility for total effective stress, mv mean

coefficient of volume compressibility for initial and total effective stresses, Sc Consolidation settlement

Table 8 Consolidation

settlement potential at 16 points

determined on the foundation

Point 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Settlement (mm) 80 126 188 120 127 184 252 188 209 297 316 220 135 220 229 143

Corrected settlement

(mm)

56 88 132 84 89 129 176 132 146 208 221 154 95 154 160 100

Environ Geol (2008) 53:1695–1710 1707

123

in terms of both elastic settlement values and consolidation

settlement values.

In buildings used for residential purposes, the suggested

allowable maximum settlement limits for the foundation

settlement on clay are 100 mm by Wahls (1981), 50–

100 mm by Sowers (1979) and Spigolon (2001), 63.5 mm

by Mac Donald and Skempton (1955), Bowles 1982) and

75 mm by Budhu (2000). In this work for foundations

settling in clay, the maximum settlement limit is accepted

to be 75 mm as suggested by Budhu (2000). When

potential consolidation settlements are added to the elastic

settlement, the building had settlement values that exceeded

acceptable tolerable settlement limits (Figs. 11, 14).

In terms of consolidation and elastic settlement values,

the settlements around the right rear of the building with

reference to the entrance are higher. SPT numbers are

relatively small in this area when compared to other parts

of the building.

On the other hand, different settlements beneath the

building exceeded the allowable limits. Between points 1

and 11, which were 25 m away from each other, the differ-

ence in corrected consolidation settlement values was

165 mm (Table 8). Between these two points angular dis-

tortion ratio was around 1/150. This ratio is the limit at which

the structural damage may occur in buildings (Wahls 1981).

On top of the consolidation settlements, when elastic set-

tlements in these two points were taken into consideration;

the total settlement at point 1 was determined as (24 + 56)

80 mm, and at point 11 became (28 + 221) 249 mm

(Fig. 11; Table 8). In this case, angular distortion ratio rose

up to (@249/25,000) 1/100. Under this angular distortion,

considerable structural deformation was expected to occur.

Corrected total settlements (ST PAP) determined con-

sidering 171 kN/m2 pressure which was assumed as the

PAP and used in the structural project reach at 59 mm at

point 4, and 84 mm at point 16. Again, under APP and at

the same points; settlements rose up to 65 and 92 mm.

Ninety-two and 84 mm settlement values were above the

allowable settlement limits in buildings.

Pressure measuring 171 kN/m2, was accepted as soil

allowable bearing pressure in the static project, but, this

does not satisfy the settlement limits. Because of this,

171 kN/m2 pressure defined as soil allowable bearing

pressure is incorrect.

It was determined that the ground settlement amount

towards the right rear direction with reference to the

Zumrut Building entrance and the different settlements

between the right rear area and the rest of the foundation

area exceed the allowable distortion limits. After the

application of building loads, 90% of the settlements of the

ground occurred within 5 years, and 98% within 10 years

period, and then, the collapse of the building occurred.

In this study, the settlements were calculated separately

for 171 kN/m2 which is the accepted soil allowable bearing

pressures in the project, 187–201 kN/m2 which are the

calculated foundation contact pressures from the project,

and 120 kN/m2 which is the allowable soil bearing pressure

determined through laboratory and in-situ tests. If the set-

tlements were calculated using 120 kN/m2, consolidation

settlements would be 18 mm at point 1, and 37 mm at

point 13 (Table 9). Under the same pressure, elastic set-

tlements would be 6 mm at point 13, and 24 mm at point

16. In addition, total settlements (ST SAP) would be 32 mm

at point 1, and 56 mm at point 16. As can be seen, the

Table 9 Corrected total

settlements (STPAP, STAPP,

STSAP) occurred under project

soil allowable pressure (PAP),

applied project foundation

contact pressure (APP) and

suggested soil allowable

pressure (SAP)

Symbol Taken points on foundation Settlement

(mm)

1 4 13 16

Sc PAP Consolidation settlements (Sc PAP) occurred under project soil allowable pressure

(PAP), PAP = 171 kN/m225 46 52 44

Sc APP Consolidation settlements (Sc APP) occurred under applied contact foundation

pressure (APP) in the project; APP = 197 kN/m229 52 60 52

Sc SAP Consolidation settlements (Sc SAP) under suggested soil allowable pressure

(SAP), SAP = 120 kN/m218 33 37 32

Se APP Elastic settlement (Se APP) occurred under applied foundation contact pressure

(APP) in the project

24 13 10 40

Se SAP Elastic settlement (Se SAP) under suggested soil allowable pressure (SAP),

SAP = 120 kN/m214 8 6 24

STPAP Corrected total settlement occurred under project soil allowable pressure (PAP)

and applied foundation contact pressure (APP); STPAP = Sc PAP + Se APP

49 59 62 84

STAPP Corrected total settlement occurred under applied foundation contact pressure in

the project (STAPP), STAPP = Sc APP + Se APP

53 65 70 92

STSAP Corrected total settlement occurred under suggested soil allowable pressure

(STSAP), ST SAP = Sc SAP + Se SAP

32 41 43 56

1708 Environ Geol (2008) 53:1695–1710

123

settlements and different settlements are less than the

allowable settlement and different settlement limits under

120 kN/m2 soil allowable bearing pressure. If this soil

allowable bearing pressure had been considered during the

design of Zumrut Building, there would have been no

problem with the settlements.

Based on the given information in the project, on the

Zumrut Building foundation, the soil ultimate bearing

capacity was not exceeded. However, the factor of safety

considered in the design was not satisfied. In other words, a

building with a lower safety level was constructed. Ground

settlement was at a level that could produce structural and

architectural damage to the building. Settlements are den-

ser under point 11 at Zumrut Building settlement area.

There exist low strength soil zones at 8–12 m depth on

the western part of the Zumrut Building, and at 10–20 m

depth on the northern and northwestern part when compared

to other parts. This situation shows that the building was

constructed on ground where one side has a higher bearing

capacity, lower settlement capacity and the other has a

relatively lower bearing capacity, higher settlement capac-

ity. It is a known fact that when a building is constructed on

ground with different strengths, different settlements and

thus, structural deformations may occur in the building.

It can be seen that Zumrut Building soil bearing capacity

and settlement characteristics show great variation and as a

result of this, there are different settlements in the building.

The settlements increase towards the right rear of the

building’s entrance. This is the direction that the building

collapsed_Ibrahim Pocanoglu, who actively participated in the

construction phase and resided in the building untill its

collapse, in his statement to the police said ‘‘wall plaster

had been falling down since the completion of construc-

tion’’. The other residents said that tiles had been falling

off since the date they moved in and there had been cracks

in the building. These statements prove that there had been

a continuous deformation in the building. This deformation

in the building shows a strong resemblance to the defor-

mation caused by ground settlements. Furthermore, the

collapse occurred towards the right rear of the building so,

it can be concluded that the weak soil structure and

excessive settlements in this section contributed to the

collapse. Due to different settlements on the ground, a

significant amount of bending takes place in structures with

high strength, and structures with low strength usually

collapse. Thus, total collapse of Zumrut Building can also

be attributed to its weakness.

On either sides of Zumrut Building, Safir and Yakut

buildings have the same number of stories and similar

dimensions. After the collapse of Zumrut Building, suspi-

cions arose about the leaning of the Safir and Yakut

buildings. The situation of Safir and Yakut buildings was

analysed by a commission comprising architects, a civil

engineer, a geology engineer and a geodesy-photogram-

metry engineer. The measurements done in the buildings

through geodesic methods, showed that the corners of the

buildings were not vertical. According to the geology and

civil engineers analysis, for a safe use of these buildings;

rehabilitation and strengthening studies were suggested.

Currently, these buildings are being strengthened by

engineers.

In the appendix of the Zumrut Building static project, a

loading-settlement chart related to allowable soil bearing

pressure existed and was used in the analysis. Issues like;

‘‘Was the plate-loading test done, to what depth was it

done, at how many locations, and how was the underlying

soil structure?’’ were insufficiently analysed. It was found

out that the ground investigation for the building was not

done, the documents on soil allowable pressure in the

project do not represent reality, and were prepared hypo-

thetically without any on-site research or analysis. These

facts were known to the project engineers and managers of

the related chambers of profession who approved the

projects, and administrators and technical personnel of the

local authority.

Previous warnings on this issue; ‘‘Ground characteristics

of the settled area of Konya represent a large variance in

horizontal and vertical distances. It must not be forgotten that

without making local ground investigations and determining

soil characteristics, those undertaking construction projects

and making general assumptions, construction engineers,

local authorities inspecting these, and any other technical

personnel taking part in this chain will all be responsible for

life and property losses (Ozdemir and Akbulut 1999)’’; were

not taken into consideration.

The Zumrut Building collapsed as a result of a chain of

mistakes made at different phases from the geotechnical,

structural and reinforced concrete project design phases to

the final construction phase with different contribution ra-

tios. Therefore, the collapse of the Zumrut Building was

due to a failure to apply engineering principles and this

mistake resulted in 92 fatalities and 35 injuries and

approximately US$7 million of material loss.

References

Barnes G (2000) Soil mechanics principles and practice. Macmillan,

New York, p 492

Bowles JE (1982) Foundation analysis and design. McGraw-Hill,

New York, p 816

Budhu M (2000) Soil mechanics and foundations. Wiley New York,

p 568

Chen FH (1999) Soil engineering testing and remedation. CRC Press,

London, p 288

Christian JT, Carrier WD (1978) Janbu, Bjerrum and Kjaernsli’s chart

reinterpreted. Can Geotech J 15:123–128

Environ Geol (2008) 53:1695–1710 1709

123

Craig RF (1990) Soil mechanics. Chapman & Hall, London, p 410

Das BM (2000) Fundamentals of geotechnical engineering. Brooks-

Cole, Belmont p 593

Liao SSC, Whitman RV (1985) Overburden correction factors for

SPT in sand. J Geotech Eng Div ASCE 112(3):373–377

Meyerhof GG (1965) Shallow foundations. J Soil Mech Found, Div.

ASCE 91(SM2):21–31

Nalbantcılar MT, Nalvuran MK, Aslan AF (2005) Apartman altı

kuyulardan saglanan suların zeminden katı tane cekmesi

(Solid particle erosion by groundwater pumping from wells

beneath buildings). Yer Bilimi ve Teknigi Dergisi, 2 28–29s,

Konya

O’Neil MW, Poormoayed N (1980) Methodology for foundations on

expansive clays. J Geotech Eng Div ASCE 106:1345–1367

Ozdemir A, Akbulut _I (1999) Konya formasyonunun jeoteknik

ozellikleri (Geotechnical properties of Konya formation),

Yerbilimleri/Geosound 34:89–105s, Adana

Skempton AW (1986) Standard penetration test procedures and the

effects in sands of overburden pressure, relative density, particle

size, ageing and over consolidation. Geotechnique 36(3):425–447

Sowers GF (1979) Introductory soil mechanics and foundations.

Geotechnical engineering, 4th edn. Mac Millan, New York

Spigolon SJ (2001) Geotechnical engineering, civil engineering PE

exam depth guide. McGraw-Hill, New York

Tomlinson MJ (1986) Foundation design and construction, 5th edn.

Longman, London, p 270

Whals HE (1981) Tolerable settlement of buildings. J Geotech Eng

Div ASCE 107(No GT11):1489–1504

1710 Environ Geol (2008) 53:1695–1710

123