ENGINEERING STRUCTURES DESIGNED WITHIN THE SCOPE OF NORTHERN MARMARA MOTORWAY PROJECT

Transcription

1 ENGINEERING STRUCTURES DESIGNED WITHIN THE SCOPE OF NORTHERN MARMARA MOTORWAY PROJECT Esra Namlı (1), Necdet Çilingir (2), Mehmet Erinçer (3), S. Şehnaz Aktaş (4), Demir H. Yıldız (5), M. Cem Dönmez (6) (1) Civil Engineer (B.S, M.S), Emay International Engineering and Consultancy Inc., Istanbul, (2) Civil Engineer (B.S), Emay International Engineering and Consultancy Inc., Istanbul, (3) Civil Engineer (B.S, M.S), Emay International Engineering and Consultancy Inc., Istanbul, (4) Civil Engineer (B.S, M.S), Emay International Engineering and Consultancy Inc., Istanbul, (5) Civil Engineer (B.S, M.S), Emay International Engineering and Consultancy Inc., Istanbul, (6) Civil Engineer (B.S, M.S), Emay International Engineering and Consultancy Inc., Istanbul, Abstract Istanbul, being the most important city of Turkiye with respect to economical and social-cultural considerations, lies among the most heavily populated urban areas throughout the world. The need for the implementation of new transportation solutions arising from the increasing population and the economical potential of the city as well as the strengthening of the existing transportation network, is of paramount importance. Accordingly, this paper is concerned with the design of engineering structures and tunnels under construction within the scope of Northern Marmara Motorway which has been tendered by General Directorate of Highways. In this paper due information is given on the designed engineering structures and tunnels and the design phase starting from the field activities. Different solutions which had to be adopted during the design stage and construction period has been described in this paper. In particular, viaducts V26 and V27 has been treated in detail with respect to soilstructure interaction.

2 2 1 Introduction The aim of the Northern Route, being within the scope of the 3 th Bosphorus Crossing Project, which begins at Bagcılar and ends at Sultanbeyli district, is to reduce the traffic volume on the existing highway network and thereby minimize the fuel consumption and detrimental effect on the environment as well as ensuring a more comfortable crossing of the Istanbul Bosphorus in a shorter time. Furthermore, the Ankara - Sincan Cayırhan Adapazarı Istanbul high speed railway line transportation system will use the 3 th Bosphorus Bridge which is under construction at present. The highway route which is under construction within the scope of the Northern Marmara Motorway (NMM) Project, consist of 4 different section of motorways and connecting roads both on the Asian and European side ( Figure 1). The route includes 20 interchanges 2 tunnels (Camlık and Riva tunnels), 35 viaducts, 53 overbridges, 44 underbridges, 8 river bridges as well as close to about 300 small engineering structures. The regional map of the route constiting of 4 section is depicted at Figure 1. Figure 1 Regional Map of the Route The chainage relating to the sections pertaining to the route is given in Table 1 as follows:

3 Table 1 The sections of the route with the corresponding chainages 3 Side Section Range of Chainage Purpose Europe 0+018,618 İstoç Connecting ,093 Odayeri Road ,462 Odayeri 2 Main Highway ,639 Garipçe Asia ,639- Poyraz 3 Main Highway ,794 Paşaköy 0+000,000 Çamlık - Connecting ,391 Reşadiye Road Soil investigations have been conducted on the route consisting of the 4 sections constructed within the scope of the Northern Marmara Motorway Project by carrying out field observations, soil boring tests and trial pits. The results of such investigation work, together with that of the soil laboratory tests conducted on soil samples have been jointly evaluated on soil samples have been determined; thus it was then possible to carry out critical cut and fill analyses and determine the incline of slope. It was then possible to determine the particular geological layer on which the foundations on the engineering structures located on the route (under bridges, over bridges, viaducts and retaining walls) rest. The Çamlık and Riva Tunnels being under constructed within the scope of Northern Marmara Motorway (Bosphorus Crossing) Project is unique in Turkiye with respect to cross sectional area. Both tunnels being the largest in Europe and the third largest in the World, was designed as double tubes, each tube containing 4 lanes (Figure 2). The tunnels of which the design and construction work continue, are located at medium depths. The maximum excavation depth and maximum excavation width of Riva Tunnel with 196 m 2 excavation area is 11m and 21m respectively. As for Çamlık Tunnel with 225 m 2 excavation area, the maximum excavation depth and maximum excavation width is 13m and 21m respectively. For both tunnels the expected traffic speed of 80 km per hour; the length of the right tube and the left tube is 564m and 624m respectively for Riva Tunnel, and 651m and 552m respectively for Çamlık Tunnel. These tunnels are excavated by using the NATM excavation method, encountering different rock conditions. The two tunnels have different load capacity and different excavation stages and bracing types.

4 4 Figure 2 Tunnel Cross- Section There are 35 viaducts within the Route, of which 3 viaducts (V06, V14,V17) have been constructed by the incremental launching method. Other viaduct were designed as consisting of precast- pretensioned prestressed concrete girder type of superstructure. Due to the dimensions and to the geological layers at foundation levels, V26 and V27 viaducts have been dealt with in detail in this paper. 2 V26 and V27 Viaducts Viaducts V26 and V27 located within the scope of Northern Marmara Motorway Project have 25 spans with a total length of 1005, 10 m and 19 spans with a total length of 782,25m respectively. For each viaduct, the individual span length is 43m and deck width is 22mx2. The pier heights vary with a maximum of 50m. Each viaduct consist of North and South bridges each accommodating 4 traffic lanes. (Figure 3). As a result of the geological and geophysical investigation work conducted at such viaducts which cross over the Riva river valleys, it was observed that the viaduct foundation would rest on the 40m thick sedimented Riva rock. It was further observed that the region lies within the 2. Seismic Zone and thus liquefaction risk would be high. Consequently, special geotechnical solutions have been proposed for the viaduct foundation system.

5 5 Figure 3 Locations of V26 and V27 Viaducts Upper cretaceous old Sarıyer formation layers and alluvium layers exist on the investigation area concerned. In the Sarıyer investigation area, generally speaking, siltstone-mudstone layers exist with dark grey sandstone layers in between for the V26 Viaduct (Figure 4). Figure 4 V26 Viaduct Geological Map

6 6 In the work area, 11 soil boring tests with various depths and geophysical investigations at 6 locations have been carried out on the planned road alignment. Table 2 shows information concerned with certain soil boring tests for the viaducts performed at alluvium formation at valley bottom. Table 2 Standard Penetration Test (SPT) values corresponding to alluvium stratum Soil Boring Test No Alluvium Thickness SPT N30 Values Soil Type AS m Clay with small amount of sand AS-75 37, Sand with silt and Clay with small amount of sand AS m Sand with silt and Clay with small amount of sand During the work, SARA Cable Seismograph with 24 channels and 4.5 Hz central frequency geophones have been used as engineering seismograph. Seismic energy has been provided by a mechanism allowing simultaneous blows by 6 hunting cartridges into the earth. Data has been collected by 2 perpendicular lines on the ground. The line lengths vary between 40 to 190m. The geophone spacing was 2m, 3 shots were made at each line, one at the center and others at each end. The shooting distance at each end of the line is 1m. The lines which are parallel to the longitudinal axis of viaduct are numbered as KS1, KS2, KS2a, KS3, KS4 and KS4a. A comparison of the geophysical investigation reveal that they are compatible (Figure 5). Figure 5 Geophysical Investigation Conducted for Viaducts

7 An evaluation of the geological and geophysical investigations described earlier revealed that the Riva alluvium is weak soil with high risk of liquefaction. By considering the results of liquid limit, water content and ratio of line-grained soil ratio as obtained from the experiments, the liquefaction potential has been evaluated accordance with the approaches proposed by Marcuson Vd. (1980), Seed and Inriss (1982) with Andrews and Martin (2000). According to such approaches the results pertaining to soil samples taken from alluvium correspond to risky regions with liquefaction potential, requiring special investigation. In order to form a basics for the geotechnical and statical calculation for viaducts V26 and V27 a non-linear time history analysis was carried out by using Plaxis 2D software and 3 sets of land movement which are scaled in accordance with the design spectrum corresponding to earthquake with average 475 years return period (earthquake with an occurrence probability of 10% in 50 years). Special land movement investigation has been carried out by Bosphorus University, Kandilli Observatory and Earthquake Research Institute for the Northern Marmara Motorway V26 and V27 viaducts. As a result of analyses, it has been decided to apply jet-grout columns so as to limit the horizontal and vertical deformations resulting from seismic forces by providing extra support to counteract the soil shear stresses and also to increase the safety factor against liquefaction risk for viaducts V26 and V27 piers situated at alluvium soil. Considering the viaducts in question without jet-grout columns in particular, non-linear calculation was carried out by modelling the bridge deck as without mass by using the Plaxis 2D software, as a result of which displacement-time values were obtained at foundation level for each pier. However, it was observed from the analyses made without jet-grout columns that the moment values reach a maximum at the rock-alluvium interface. Consequently, additional analyses were made with jet-grout columns in order to limit the horizontal and vertical deformation resulting from seismic forces by providing extra support to counteract the soil shear stresses and also to increase the safety factor against liquefaction risk for piers where ground water level correspond to alluvium layers. In the solutions including jet-grout columns the cohesion and unconfined compressive strength of the upper alluvium layer has been increased and accordingly soil became stiffer (as compared to earlier case without jet-grout column), load bearing capacity increased and probable settlements reduced. By virtue of jet-grout columns horizontal loads acting on piled foundations and the relevant deformations were decreased where liquefaction risk exists. The repetitive shear stress ratio which soften and in fact liquefy the soil has dropped as the seismic shear stresses were partly counteracted by jet-grout columns, as indicated by liquefaction analyses including jet-grouting. For these viaducts, displacement-time values deduced from Plaxis 2D were used horizontal movement entry data by using non-linear calculation models in Sap2000. A maximum of maximum values of plastic deformation obtained has been taken for each seismic record as a result of analysis. Total curvatures were obtained by converting plastic curve values into plastic curvatures and 7

8 8 subsequently adding them to the yield curvatures. The total curvatures were then compared with the concrete compression and steel tension values at locations where moment-curvature relationships were obtained at piers. Finally, all piers in this viaduct which had been designed by carrying out linear analysis were found to satisfy limited damage (LD) performance level corresponding to an earthquake with 475 years average return period. The analysis model, total horizontal displacement distribution and displacement-time graph deduced from Düzce seismic record obtained by using Plaxis 2D software is given below for viaduct V26 at Figure 6, Figure 7, Figure 8 respectively. Figure 6 V26 Viaduct Plaxis Model Figure 7 V26 Viaduct Total Horizantal Displacement Graph

9 Figure 8 Displacement Time Graph for Düzce Seismic Record 9 3 Conclusions The design work had to be completed in a short time, as the Northern Marmara Motorway Project had been tendered by Build Operate Transfer (BOT) method. This time shortage had no negative effect on construction quality, time schedule and design work. All necessary measures had to be taken to maintain the necessary project quality and the Northern Marmara Motorway Project has been implemented meticulously, as this is a prestige Project for our country. References 1. General Directorate of Highways (1973) Technical Specification for Road Bridges. 2. Turkish Republic Ministry of Public Works and Settlement (2007) Specification for Buildings Built in Seismic Areas. 3. General Directorate of Highways, Department of Business (2012) Criteria Reports. 4. American Association of State Highway and Transportation Officials (2002) Standart Specifications. 5. Erdik M (2014) Views on Seismic Design of Northern Marmara Motorway V26 and V27 Viaducts and Determination of Design Based Seismic Ground Motion. 6. Durgunoglu H T (2004) The Use of High Modelled Columns in Foundation Engineering, Bosphorus University, Kandilli Observatory. 7. Istanbul Technical University Soil Mechanics and Foundation Engineering Istanbul 10. National Congress