Performance of very deep temporary soil nailed walls in Istanbul

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1 Performance of very deep temporary soil nailed walls in Istanbul H. Turan Durgunoğlu & H. Bora Keskin H. Fatih Kulaç,, Selim İkiz, Turhan Karadayılar ZETAS Zemin Teknolojisi A.S., Turkey ISSMGE, TC 17 Ground Improvement Workshop WG G Earth Reinforcement in Cut September 24, 2007

2 Recent growth in economy caused a great attraction for the construction of high-rise residential and office buildings in Istanbul, Turkey. In order to obtain parking space, deep excavations are employed to allow great number of basements below these tower structures. The depths of the excavations commonly reach to meters below the ground surface.

Istanbul is potentially under the influence area of the Marmara Fault System, which is the western end of the North Anatolian Fault NAF of Turkey. Recent studies conducted after 1999 Kocaeli (M w =7.

3 Istanbul is potentially under the influence area of the Marmara Fault System, which is the western end of the North Anatolian Fault NAF of Turkey. Recent studies conducted after 1999 Kocaeli (M w =7.4) and Düzce (M w =7.2) earthquakes indicated about 65% probability for the occurrence of a M w >7.0 effecting Istanbul within the next 30 years due to the existence of potential seismic gaps (Parsons et al., 2000).

$The T extend of weathering and fracturing controls the mechanical properties and in fact$ $The geotechnical modeling of formation, weathered zones, extend of fracturing and$

4 The subsoil is mainly greywacke formation of claystone siltstone sandstone alterations known as Trace formation. The T extend of weathering and fracturing controls the mechanical properties and in fact geological observations do well agree with the results of measurements reflecting mechanical properties of the formation. The geotechnical modeling of formation, weathered zones, extend of fracturing and compressibility modulus of formation are obtained by integrated seismic survey and Menard pressuremeter testings performed within the boreholes at various locations and depths.

5 Structural interpretation of the P-wave P velocity-depth model for a seismic line from Ciftciler Tower site (Durgunoglu ve Yilmaz, 2007)

6 Definition of soil formation based on V s values (Durgunoglu ve Yilmaz, 2007)

7 Analysis of surface waves on a shot record from Soyak Tower site (Durgunoglu ve Yilmaz, 2007)

V s = 400 800 m/sec The S-wave S velocity-depth profiles from the Ciftciler Tower site along

8 V s = m/sec The S-wave S velocity-depth profiles from the Ciftciler Tower site along the seismic line associated with the P-wave P velocity-depth model (Durgunoglu ve Yilmaz, 2007)

9 G 0 = ρv s 2 Effect of Strain Level on Modulus (FHWA Circular no 5, 2002)

10 Effect of Factor of Safety on Modulus (FHWA Circular no 5, 2002) Modulus Degradation Curve

11 SOIL TYPE G 0 (MPa) Soft Clays 3-14 Hard Clays 7-35 Silty Sands Dense Sand and Gravel Soft Rocks Range of G 0 for Various Formations (Durgunoglu ve Yilmaz, 2007), (FHWA Circular no 5, 2002)

12 The variation of shear modulus with depth Greywacke (Durgunoglu ve Yilmaz, 2007)

13 Recommended Shear Modulus Degradation Ratios (Durgunoglu ve Yilmaz, 2007)

14 Material Characterization Consequences The range of modulus values, G 0 ( MPa) determined based on V s ( m/sec) values are great. The range of degradation ratios (30-200) to obtain G for certain Factor of safety values are large as well. Therefore the modulus value of greywackes of Istanbul to be utilized ized in numerical models such as PLAXIS to predict the displacements do vary in a very big range. Consequently, the displacements of soil nailed walls based on selected modulus values are only indicative. Direct measurement of lateral displacements of deep soil nailed walls in Istanbul is compulsory in order to follow performance of such structures during and after construction.

15 Soil Nailing Practice in Turkey Based on the previous positive records of flexible earth retaining ng structures during earthquakes in Turkey by Mitchell et al. (2000) ) and Durgunoglu et al. (2003a), soil nailed walls in such excavations performed within the city offer great advantage especially for the t encountered subsoil and seismic conditions. During the last ten years soil nailed walls have been extensively constructed within the city of Istanbul as flexible temporary retaining walls to support the basement excavations of various structures. According to recent compilation by ZETASZ (2006) about 160,000 m 2 of wall had been constructed in 60 different projects

16 Presented Six Major Case Studies 1. BJK Fulya Complex 2. Istinye Park Complex 3. Kanyon Complex 4. Mashattan Residence 5. Tepe Shopping Mall 6. Besler Warehouse 6,500 m 2 20,000 m 2 16,000 m 2 6,500 m 2 6,000 m 2 8,000 m 2 TOTAL 63,000 m 2

17 Geometrical data and soil conditions of case studies H max : Maximum soil nailed wall height : Slope angle : Nail orientation Nail hole diameter β ( )( ω ( )( D (mm) : Nail hole diameter

18 A Photograph From BJK Fulya Complex

19 BJK Fulya Complex, Detailed Cross-section section at Inclinometer No.1

20 BJK Fulya Complex, Inclinometer No.1 Readings

21 A Photograph From Istinye Park Complex

22 Istinye Park Complex, Detailed Cross-section section at Inclinometer No.4

23 Istinye Park Complex, Inclinometer No.4 Readings

24 A photograph from Kanyon Complex

25 Kanyon Complex, Detailed Cross-section section at Inclinometer No.7

26 Kanyon Complex, Inclinometer No.7 Readings

27 A Photograph From Mashattan Residence

28 Mashattan Residence, Detailed Cross-section section at Inclinometer No.1

29 Mashattan Residence, Inclinometer No.1 Readings

30 A Photograph From Tepe Shopping Mall

31 Tepe Shopping Mall, Detailed Cross-section section at Inclinometer No.4

32 Tepe Shopping Mall, Inclinometer No.4 Readings

33 A Photograph From Besler Warehouse

34 Besler Warehouse, Detailed Cross-section section at Inclinometer No.1

35 Besler Warehouse, Inclinometer No.1 Readings

36 Case Study No. 3 - Typical Lateral Displacement Data Kanyon Complex, Inclinometer No. 7; Excavation Steps

37 Case Study No. 3 - Typical Lateral Displacement Data Kanyon Complex, Inclinometer No. 7; Lateral Displacements vs. Time

38 Case Study No. 3 - Typical Lateral Displacement Data Kanyon Complex, Inclinometer No. 7; Lateral Displacements vs. Depth

39 Case Study No. 3 - Evaluation of Typical Lateral Displacement Data The major height of the soil nailed wall was completed within six months, the excavation was kept open for almost another two years due to delay in final design of the upper structures to be constructed and obtaining related r building permit from the municipality. It is interesting to note e the followings: The lateral displacement has increased linearly with depth up to an excavation depth of 18.0 m. For greater depths the rate of increase in the lateral displacement was increased considerably. Athough the temporary excavation with soil nailed retaining structure ture left open for more than two years, almost no additional lateral displacement was observed in spite of heavy rain and snow within that period indicating that the drainage system designed and implemented were performed satisfactorily. Subhorizontal drains, in length of l d =3 m, were implemented at S h = 8 to 9 m horizontal spacings with an inclination of 3 3 to the horizontal. The typical vertical spacings were S h = 4 to 6 m.

40 Design and Performance Parameters H, excavation height,, m S = S h x S v, area per nail,, m 2 S h, horizontal spacing between nails,, m S v, vertical spacing between nails,, m L, average nail length,, m η = L/S, nail density,, m/m 2 L r = L/H, length ratio B r = DxL/S, bond ratio S r = D 2 /S, strength ratio DESIGN δ h, lateral displacement at the top,, mm P r = δ h /H, performance ratio PERFORMANCE

41 Case No.1 - BJK Fulya Complex Design and Performance Parameters

42 Case No.2 Istinye Park Complex Design and Performance Parameters

43 Case No.3 - Kanyon Complex Design and Performance Parameters

44 Case No.4 Mashattan Residence Design and Performance Parameters

45 Case No.5 Tepe Shopping Mall Design and Performance Parameters

46 Case No.6 Besler Warehouse Design and Performance Parameters

47 Lateral Displacements vs. Height of Soil Nailed Walls GREYWACKE FORMATION Siltstone - Claystone Sandstone - Siltstone - Claystone Sandstone

48 Performance Ratios vs. Height of Soil Nailed Walls GREYWACKE FORMATION Siltstone - Claystone Sandstone - Siltstone - Claystone Sandstone

49 Average Nail Lengths vs. Height of Soil Nailed Walls GREYWACKE FORMATION

50 Nail Density vs. Height of Soil Nailed Walls GREYWACKE FORMATION

51 Performance of Soil Nailed Walls Concluding Remarks It is seen that the linear increase in lateral displacement with the height of the wall is valid up to a certain height. Therefore using u conventional methods of design, Federal Highway Administration (2003) and previously developed charts for estimating lateral displacements or performance ratio may be misleading in deep soil nailing applications tions. The performance ratio, P r, for the greywacke formation is within the range of 1x10-3 to 3x10-3, depending on the nature of the lithological unit of the formation. For the strongest silicified sandstone with E =250 m MPa, P r ~ 1x10-3, on the other hand for the weakest claystone P r ~ 3x10-3 with E m =50 MPa. It is seen that these values tend to increase after 25 m for the case of sandstone and 15 m for the case of claystone.

52 Performance of Soil Nailed Walls Concluding Remarks Average nail length, L, increases linearly with the height of soil nailed wall. The average nail length that could be utilized is about L=5 5 to 8 m for H=10 m and L=8 to 11 m for H=20 m. Nail density, L/S (m/m 2 ) also increases linearly with the height of the soil nailed wall. It is about 1.6 to 3.2 m/m 2 for H=10 m and 2.8 to 4.4 m/m 2 for H=20 m. It is seen that two sections from Case No. 5 are overdesigned since they have noticeably long average nail lengths and nail densities considering relatively small wall heights. However, excessive nail lengths implemented on these sections have no or little effect on the lateral displacements or performance ratios. Performance of soil nailed walls are recommended to be monitored and to be compared with provided range of performance parameters based on the lithological description of the greywacke formation.

53 CONCLUSIONS Soil nailing is a very versatile excavation retaining system for deep excavations in urban areas surrounded by major structures and infrastructures provided that limiting lateral displacements are not exceeded. Based on the previous positive records of flexible earth retaining ng structures during earthquakes in Turkey soil nailed walls in such excavations performed within the city offer great advantage especially for the encountered subsoil and seismic conditions. As a result the values of performance ratio for soil nailed walls s together with nail density in typical greywacke formation of the city of Istanbul are developed based on these extensive case studies as a guideline for future applications.

PERFORMANCE OF VERY DEEP TEMPORARY SOIL NAILED WALLS IN ISTANBUL

PERFORMANCE OF VERY DEEP TEMPORARY SOIL NAILED WALLS IN ISTANBUL TC 17 Ground Improvement Workshop WG G Earth Reinforcement in Cut XIV ISSMGE, Madrid, September 24 th, 2007 H. Turan Durgunoğlu & H. Bora