Structures on and within Man-made Deposits - Kansai International Airport -

Transcription

1 Structures on and within Man-made Deposits - Kansai International Airport - Osaka University Kazuhiro ODA Structures on and within Man-made Deposits - Kansai Airport - Outline of Kansai International Airport Geotechnical Problems Residual large-scale settlement Differential settlement Residual lateral displacement Recent topics Numerical model on upper Pleistocene clays of Osaka Bay Spatial estimation of soil properties Structures on and within Man-made Deposits - Kansai Airport - Outline of Kansai International Airport Geotechnical Problems Residual large-scale settlement Differential settlement Residual lateral displacement Recent topics Numerical model on upper Pleistocene clays of Osaka Bay Spatial estimation of soil properties Location of Osaka JAPAN Tokyo Osaka Kansai International Airport is the only international airport in Osaka. Osaka is second largest city in Japan. It is a center of the western side of Japan in the economical and social activity

2 Osaka Bay Kyoto Osaka Univ. Osaka Kobe Nara Osaka Bay The city of Osaka faces the Osaka Bay The Osaka Bay is an inland bay formed in the Osaka Basin surrounded by mountainous regions with rock bed The present shape of the Osaka Bay is like an ellipse having the long axis in the direction of north-east to south-west. The size is about 6km of the long axis and about 3km of the short one, and about 15km 2 of the area. Transition of Land Reclamation (Before Edo era) Reclaimed lands in Osaka Bay Kansai International Airport LEGEND Before modern ages Under construction or planning The history of developing the Osaka Bay can go back to the ancient time, and in the Edo era ( ) New land development in the estuary of big rivers had been carried out for rice fields. Transition of Land Reclamation (Meiji Era) Reclaimed lands in Osaka Bay Kansai International Airport Since the Meiji era ( ), land development due to reclamation along coastal area was rapidly extended for the harbor facilities and industrial site. Transition of Land Reclamation (After World War II) Reclaimed lands in Osaka Bay Kansai International Airport After the World War Ⅱ, a trend of land development has been turned from the reclamations along costal area into the construction of off-shore man-made islands. LEGEND Before modern ages Under construction or planning LEGEND Before modern ages Under construction or planning

3 Transition of Land Reclamation Reclaimed lands in Osaka Bay Kansai International Airport LEGEND Before modern ages Under construction or planning These islands had been constructed on very soft seabed deposits with water depth of over 1m at offshore. Therefore, the occurrence of various kinds of geotechnical problems concerned with the soft clay deposits was forecasted, and their countermeasures were examined. Kansai International Airport Area of the airport island of the 1 st Phase is 51ha. That of the 2 nd Phase is 545ha. The Kansai international airport has two runways. The one is Runway A in 3,5m long, the other is Runway B in 4m in long. Kansai international airport is the only airport operating for 24 hours. History of Kansai International Airport 1987: Start of construction of the airport island of the 1 st Phase 1991: Completion of construction of the airport island of the 1 st Phase 1994: Opening of the Kansai International Airport History of Kansai International Airport 1999: Start of construction of the airport island of the 2 nd Phase 25: Completion of construction of the airport island of the 2 nd Phase 27: Start of operation of Runway B

4 Geological profile of seabed at airport site Geological profile of seabed at airport site The geological formation is inclined toward offshore, while comparatively homogeneous along the shoreline. The uppermost Holocene clay layer is almost normally consolidated. thickness is from 18m to 24m. The underlain Pleistocene deposits are the overconsolidated clay layers (Ma: marine clay, Dtc and Doc: non-marine clays) with about 1.3 of OCR and the sand and gravel thin layers. These layers alternately deposit in the total thickness of several hundreds meters. Overburden pressure due to construction Reclaimed land in Osaka Bay The conventional reclaimed land load 2-3 tf/m2 The KIA island load 1st phase 45-5 tf/m2 2nd phase 55-6 tf/m2 The pressure is affected more deeper position in case of Kansai International Airpot Structures on and within Man-made Deposits - Kansai Airport Outline of Kansai International Airport Geotechnical Problems Water Depth Residual large-scale settlement Differential settlement Residual lateral displacement LEGEND Before modern ages Under construction or planning Recent topics Numerical model on upper Pleistocene clays of Osaka Bay Spatial estimation of soil properties

5 The Holocene clay layer is improved by sand drains, before reclamation. However, the Pleisticene layers could not be improved. Depth Below Sea Level (m) Kansai Ma-13 Ds-1 Ma-12 Ma-11a Ma-1 Ma-9 Ma-8 Ma-7 Ds-1 Ma-3 Ma-2 Ma-1 Ma- Holocene Deposit Pleistocene Deposits Thickness is about 2 m Improved by Sand Drain Sand Drain Method Dia. = 4 cm Overburden Pressure (kpa) Settlement of the 1 st phase island Settlement (m) Elapsed Time (Day) Open the Airport Sep Holocene Layer (Improved by Sand Drain) Pleistocene Layers Total Settlement The settlement of Holocene clay layer had already finished. The residual large-scale settlement occurs mainly in the thick Pleistocene clay layers Variation of Measured Settlement at Ground Level of the KIAI (Phase I) Settlement (m) Time (Day) Off shore 1-4-A 1-5-A 1-6-A 1-7-A 1-4-A 1-5-A 1-6-A 1-7-A Residual settlement behaviors are different in the airport island. Settlements in 1-4-A is greater than those in 1-7-A. Holocene and Pleistocene clay layers in 1-4-A are those in 1-7-A. Settlement rate(cm/year) Settlement Rate of Ground Surface Yearly reduction of settlement rate 3cm/year 4cm/year Average of 17 positions Year The settlement rate will decrease gradually. The rate becomes about 7cm/year in 213. The consolidation settlement will continue after 214. It is very important to predict the settlement in the future, because of maintenance of KIA. Distinguishing consolidation characteristics of Pleistocene clay make difficult to predict of settlement.

6 Countermeasure against Residual large-scale settlement Prediction of long-term consolidation behavior of Pleistocene clay layers To elucidate the distinguishing consolidation characteristics of Pleistocene clays Numerical modeling of these consolidation behavior Configuration of sand or sandy gravel layers Estimation of sand or sandy gravel layers as drainage paths Etc. Relative Settlement(m) Differential Settlement of the Runway Structures on and within Man-made Deposits - Kansai Airport Outline of Kansai International Airport Geotechnical Problems Residual large-scale settlement Differential settlement Residual lateral displacement Recent topics Numerical model on upper Pleistocene clays of Osaka Bay Spatial estimation of soil properties Differential Settlements of the Passenger Terminal Building 6cm Distance (m) Fuel tanks Supply and disposal zone Passenger terminal Control tower International Railway station Runway buildings (PTB) Aero plaza cargo terminal A Domestic cargo terminal Ferry terminal Mentenance zone Oil tanker berth A Runway (3,5m 6m) To access bridge Maximum differential settlement of Runway is about 6 cm. The differential settlement is not so much without any troubles of landing and taking off, because of the ground improvement due to vibro-tamping. The passenger terminal building was designed by a italian designer. It is not so strong for differential settlement.

7 Plane View of the Terminal Building Accumulated Relative Settlement about 1,6 m Length (m) about 1,6 m The passenger terminal building was rested directly on the fill material without piles. Settlement(mm) % % -2 The differential settlement occurred with the maximum gradient of about.4%, mainly due to the uneven surcharge load. The maximum gradient was more than the critical value of.2%. Countermeasures against Differential Settlement of the Building Manual Jack-up under Operation Hydraulic jack Pillar Cross-section of PTB Filler plates Outline of Jacking up system The jacking up system was applied to the bottom of ground floor of the terminal building to adjust the differential settlement Number of pillars is about 1,.

8 Settlement(mm) Differential settlement curves before and after the jacking-up Terminal Building As of Dec. Length (m) Jack Up.18% The gradient is reduced to.18% It is less than the critical value. After Juck up Before Juck Up Structures on and within Man-made Deposits - Kansai Airport - Outline of Kansai International Airport Geotechnical Problems Residual large-scale settlement Differential settlement Residual lateral displacement Recent topics Numerical model on upper Pleistocene clays of Osaka Bay Spatial estimation of soil properties Mechanism of lateral residual settlement The distributions of lateral displacement and gradient of settlement are very similar. The residual lateral displacement of the reclaimed deposits is caused by the residual differential settlement of seabed soft layer. Ground Surface Settlement Seabed Surface Settlement Lateral Displacement Caisson Gradient of Settlement Lateral Displacemen t Settlement Gradient of Settlement Lateral Deformation around Seawalls in Kansai International Airport Depth (m) Reclaimed soil A C Lateral displacement (cm) toward sea toward inland 152days 336days 738days 93days The lateral displacement occurs as the rotational deformation around a position on the uppermost surface of Pleistocene layers.

9 Lateral Displacement of Seawalls in KIAI (phase I) Example of Countermeasure against Lateral Displacement 1993/ / / / / / /12 2/12 21/12 22/12 23/12. ② ② ① ① Bent pipe ③ lateral displacement ｍ ③.5 ④ ④ 1. ⑤ ⑤ ⑥ ⑥ ④ ⑥ ⑤ ① ④ ② ⑤ ③ ⑥ ③ ① ② 2.5 All data show the time-dependent lateral displacement of 1 2m at maximum toward inland. Bent pipelines on bridge to oil tanker berth The best countermeasure against the lateral displacement is not to construct any important facilities within the affected zone, which is within about 7m from the seawall. The pipelines connecting with tanker berth were bent to avoid the affect of lateral displacement of seawall. Countermeasure against differential settlement and lateral displacement Structures on and within Man-made Deposits - Kansai Airport - Prediction of residual settlement at arbitrary position in inland. Outline of Kansai International Airport Geotechnical Problems Residual large-scale settlement Differential settlement Residual lateral displacement Accurate estimation of the history of reclamation Spatial estimation of soil properties. Etc. Recent topics Numerical modeling on upper Pleistocene clays of Osaka Bay Spatial estimation of soil properties

10 Consolidation characteristics of Pleistocene clays of Osaka Bay The Pleistocene clays of Osaka Bay have the consolidation yield stresses, p c, higher than the current overburden pressure, p, although the clays have never been applied higher pressure than the current overburden pressure, p, judging from the geological findings. In that sense, Pleistocene clays of Osaka Bay have been called as quasi-overconsolidated clays. The mechanical characteristics of the quasi-overconsolidated clays are quite distinctive from those of mechanically overconsolidated clays due to loading/unloading history. Long-term consolidation characteristics of Quasi-overconsolidated clay Vertical strain (%) p : 87kPa p c : 1294kPa Ma1 at Kansai international airport 1x1-2 1x1-1 1x1 1x1 1 1x1 2 1x1 3 1x1 4 1x1 5 Elapsed time (min) A significant delayed compression occurs after end of primary consolidation even in the range of stress lower than p c. The slope of curve between the creep strain and the logarithmic time becomes gentle with the elapsed time. } Applied pressure is lower than p c Applied pressure is around p c Applied pressure is higher than p c Estimated compression curve of Ma7 clay Initial overburden pressure Compression strain ε(%) Δp=4kN/m 2 P Data points : The calculated results based on 実測値 field measurements 標準圧密試験 Solid lines 定ひずみ試験 : Oedometer test P+Δp OCR=1.~ Effective stress p (kn/m 2 ) Currently applied pressure Applied pressure in oedometer The relationship between compression strain and effective stress at the in-situ was obtained through calculation based on the field measurements of both pore pressure and compression of Ma7 clay layer. A significant compression strain would occur at the in-situ, although the yielding does not occur in the conventional consolidation tests at the currently applied pressure, P+ p,. CRS test Compression curve at the in-situ Solid lines denote the results of conventional consolidation tests Difference between in conventional consolidation tests and at the in-situ Drainage path length is 1mm in the conventional consolidation tests. Strain rate is very rapid Drainage path length is more than 1m at the in situ. Strain rate is very slow Difference of strain rate is one of very important factors. Time-dependent mechanical characteristics will affect consolidation behavior.

11 Outlines of proposed model for quasioverconsolidated clays Objects of the research A series of numerical simulation is carried out in order to investigate the effect of drainage path length on the long-term consolidation behavior of quasi-overconsolidated clays in the range of stress lower than pc. The effect of drainage path length on compression behavior of the Pleistocene clays is discussed from the viewpoint of time-dependency. surface theory is applied to express smooth transition of time-independent compression behavior in the range of stress from around p to over pc. dv p dt max 1 y v 1 max v v 1 exp ln v 1 dy y B v y B 1 exp v B max vp 1 e p dv 1 e Strain rate *) Solid lines denote 1 7 the isochronal compression curves Consolidation pressure (logarithmic scale) Strain due to secondary consolidation surface theory is applied to express timedependent compression behavior, such as secondary consolidation. dr R 1 e p' Secondary consolidation Flow v v v v ln v dp ' Schematic diagram of proposed model Compressive strain Outlines of proposed model for quasioverconsolidated clays Subloading Elapsed time (logarithmic scale) Compression curves are do not follow the conventional e-log p relationship. Non-linear relationship between void ratio and logarithmic consolidation pressure is applied. Isochronal compression curves are parallel to each other, however, the interval between each curve decreases with decrease of vertical strain rate, so that the slope of curve between the creep strain and the logarithmic time becomes gentle with the elapsed time

12 Numerical simulations One-dimensional consolidation elastoviscoplastic consolidation finite element method is applied. Mechanical parameters used in the analysis are determined from a series of long-term consolidation tests of Ma1 clay, middle Pleistocene clay of Osaka Bay. The drainage path length is chosen as a variable parameter in the numerical simulation. Physical properties of Ma1 depth -12m~-135m wl (%) 111 wp (%) 52 Ip 59 s (g/cm3) 2.66 w (%) 72 e 1.91 p (kn/m2) 12 pc [CRS](kN/m2) 153 The clay was taken from deep layer. Over consolidation ratio is almost 1.5. Applied pressures in long-term consolidation tests of Ma1 clay Analytical parameters λ κ In experimental cases from Case-1-1 to Case-1-3, a series of long-term consolidation tests were carried out in the range of stress lower than the consolidation yield stress. In Case-1-4, the test was carried out in the stress almost equal to consolidation yield stress. In Case-1-5 and Case-1-6, the tests were carried out in the range of stress higher than the consolidation yield stress. max v (1/min) ν R k(cm/min) Ck α β /4 -.5 deep

13 Applicability of proposed model Analytical cases Vertical strain (%) x1-1 Solid curves : Anaytical results Data points : Experimental results Applied pressure B :117kPa (lower than pc) F :126kPa (lower than pc) H :131kPa (lower than pc) E :146kPa (equal to pc) G :161kPa (Higher than pc) A :175kPa (Higher than pc) 1x1 1x1 1 1x1 2 1x1 3 Elapsed time (min) 1x1 4 Ma1 clay 1x1 5 Vertical strains vs. Elapsed time 1x1 6 Vertical strain (%) x1-3 Solid curves: Analytical results Data points: Experimental results Applied pressure B :117kPa (lower than pc) F :126kPa (lower than pc) H :131kPa (lower than pc) E :146kPa (equal to pc) G :161kPa (Higher than pc) A :175kPa (Higher than pc) 1x1-4 1x1-5 1x1-6 1x1-7 Strain rate (1/sec) 1x1-8 Ma1 clay 1x1-9 Vertical strains vs. Strain rate The numerical simulation can reproduce very well a series of longterm consolidation test of Ma1 as shown in above Figures. 1x1-1 Cases Applied pressure (kpa) Drainage path length (cm) Case (Oedometer tests) Case Case Case Case Case Case Case Case Drainage path length is varied from.1m to 4.m in the parametric study. Drainage path length of.1m corresponds to that of specimen in conventional consolidation tests such as oedometer, meanwhile the drainage path length of over 1.m is almost equivalent to field size of Pleistocene clay layers in Osaka Bay. The yielding did not occur in the test at the stress of the applied pressure of 131kPa. Therefore, it can be generally considered that a significant settlement will not occur. Analytical results Vertical strain (%) Average excess pore pressure (kpa) x1-4 H=.1m 1x1-3 H=.5m 1x1-2 H=.1m 1x1-1 H =.1m H =.5m H =.1m H =.5m H = 1.m H = 5.m 1x1-4 1x1-3 1x1-2 1x1-1 H=.5m 1x1 1x1 H=1.m 1x1 1 H=5.m 1x1 2 1x1 3 1x1 4 1x1 5 Elasped time (min) 1x1 1 1x1 2 1x1 3 1x1 4 1x1 5 Elasped time (min) 1x1 6 1x1 6 H=1.m 1x1 7 1x1 7 H=2.m H=4.m Vertical strain vs. Elapsed time 1x1 8 H = 1.m 1x1 8 1x1 9 H =.1m H=4.m Average excess pore pressure vs. Elapsed time 1x1 9 1x1 1 1x1 1 In the case of drainage path length shorter than.5m, the vertical strain becomes temporarily stable at about 1.5%, and the required time to become about 1.5% is longer with increase of drainage path length. The significant vertical strain occurs again after the elapsed time of about 1 4 minutes, regardless of drainage path length. The increase of vertical strain stops once, as the excess pore pressure dissipates completely. The vertical strain of about 1.5% should be caused by the primary consolidation. The significant increase of vertical strain after the elapsed time of about 1 4 minutes will occur due to the time-dependent mechanical characteristics such as secondary consolidation. Analytical results Vertical strain (%) Average excess pore pressure (kpa) x1-4 1x1-4 H=.1m 1x1-3 1x1-3 H=.5m 1x1-2 1x1-2 H=.1m 1x1-1 1x1-1 H=.5m 1x1 1x1 H=1.m 1x1 1 H=5.m 1x1 2 1x1 3 1x1 4 1x1 5 Elasped time (min) 1x1 1 1x1 2 1x1 3 1x1 4 1x1 5 Elasped time (min) 1x1 6 1x1 6 H=1.m 1x1 7 1x1 7 H=2.m H=4.m Vertical strain vs. Elapsed time H =.1m H =.5m H =.1m H =.5m H = 1.m H = 5.m 1x1 8 H = 1.m 1x1 8 1x1 9 H =.1m H=4.m Average excess pore pressure vs. Elapsed time 1x1 9 1x1 1 1x1 1 In the case of drainage path length longer than 5.m, the vertical strain monotonically increases. Also, the average excess pore pressure still remains at the elapsed time of about 1 4 minutes. That is, the primary consolidation is not yet over. The time-dependent mechanical characteristics can not be ignored before the end of primary consolidation, because they become remarkable after the elapsed time of about 1 4 minutes. Therefore, the primary consolidation behavior in these cases is affected significantly by time-dependent mechanical characteristics.

14 Verticval strain (%) Effect of drainage path length on compression curve H =.5m,.1m,.5m,.1m H=4.m H=2.m H = 1.m H = 5.m End of primary consolidation H=1.m Secondary consolidation Vertical effective stress (kpa) The compression curves between vertical effective stresses of 12kPa and 131kPa are almost straight lines in the cases of drainage path length less than.5m, because the secondary consolidation does not occur before the end of primary consolidation. The direction of compression curves sharply turn downward at the vertical effective stress of 131kPa. The vertical strains significantly increase due to the secondary consolidation without any change of vertical effective stress. Verticval strain (%) Effect of drainage path length on compression curve In conventional consolidation tests H =.5m,.1m,.5m,.1m H=4.m H=2.m H = 1.m H = 5.m H=1.m Secondary consolidation Vertical effective stress (kpa) Compression curves in the case where drainage path length less than.5m are coincident with each other. As drainage path length of.1m corresponds to that of specimen in conventional consolidation tests, the compression curve before the occurrence of secondary consolidation coincides with that obtained through conventional consolidation tests. Verticval strain (%) Effect of drainage path length on compression curve H =.5m,.1m,.5m,.1m H=4.m H=2.m H = 1.m H = 5.m H=1.m In conventional consolidation tests Vertical effective stress (kpa) Compression curves in the cases of drainage path length greater than 5.m, are affected by timedependent mechanical characteristics. The longer the drainage path length, the earlier the compression curves is separated from that in the cases of drainage path length less than.5m. Especially, the compression curve in the case of drainage path length of over 2.m is separated at around the beginning. After the compression curve being separated, the slope of compression curve becomes steeper. Comparison between filed measurements and Numerical simulation Initial overburde n pressure Compression strain ε(%) Compressio n curve at the in-situ Data points : The calculated results based on 実測値 field measurements 標準圧密試験 Solid lines 定ひずみ試験 : Oedometer test Δp=4kN/m 2 P P+Δp Conventional consolidation tests Currently applied pressure OCR=1.~1.7 CRS test Effective stress p (kn/m 2 ) Applied pressure in oedometer In conventional consolidation tests Vertical effective stress (kpa) The numerical simulation can qualitatively reproduce the occurrence of the significant residual settlement. The difference of compression behavior between in conventional consolidation tests and the in-situ will be caused by strain rate in the consolidation process. Verticval strain (%) H =.5m,.1m,.5m,.1m H=4.m H=2.m H=1.m H = 5.m H = 1.m At the in-situ

15 Structures on and within Man-made Deposits - Kansai Airport - Outline of Kansai International Airport Geotechnical Problems Residual large-scale settlement Differential settlement Residual lateral displacement Recent topics Numerical model on upper Pleistocene clays of Osaka Bay Spatial estimation of soil properties with ANN The purpose of this study is to estimate properties of Holocene Clays at arbitrary position in Kansai International Airport from limited number of soil investigations with ANN Information from GIbase PURPOSE Estimation by NN Interpolation 58 ARTIFICIAL NEURAL NETWORK (ANN) 59 CONSTRUCTION OF ANN MODEL 6 Neurons in the human brain are reproduced mathematically a large number of neurons in human brain INPUT THINK modelization x1 : xn INPUT w1 : wn weight θ out THINK OUTPUT example datasets for construction of NN model coordinates INPUT soil properties target values OUTPUT weight coordinates North East Depth Input layer Hidden layer soil properties Natural Water Content Output layer back propagation neural network etc estimated values OUTPUT NN model The clay properties at an arbitrary position were estimated.

16 Subject area 15 Natural ANALYSIS Water Content RESULT(WN) 62 Holocene clays : Kansai International Airport Three dimensional distribution Number of boring 184 Number of data 947 Input data Longitude Latitude Depth Consolidation pressure Output data Natural water content, Liquid limit e log p curve Locations of soil investigations Liquid limit (Wl) 63 e-logp relationship 18 Three dimensional distribution One dimensioinal consolidation curves Void ratio estimated Sample A estimated Sample B estimated Sample C Sample A Sample B Sample C The agreement between the target value and estimated value is excellent Consolidation pressure(kpa)

17 Summary Construction of Kansai International Airport started in We have faced various geotechnical problems. Some of these problems had already worked out. However, the unsolved problems still remains now. Also, the new problems will arise. We need to efforts to work out these problem more and more. The results of our research works about Kansai International Airport will contribute for development of the geotechnical engineering. Thank You for your attention Structure of Seawall

18 Settlement of the Kansai Airport Overburden stress (tf/m2) 1987/9 1988/9 1989/9 199/9 1991/9 1992/9 1993/9 1994/ Settlement (m) Time 1987/9 1988/9 1989/9 199/9 1991/9 1992/9 1993/ Measured(Total) Measured(Alluvial layer) Measured(Pleistocen e layer) Analytical(Total) Analytical(Alluvial ) Variation of measured settlement at ground level of the Kansai Airport island (phase I) with time Observed Settlement (m) Year Final Reclamation Opened Airport A 12 B 1st Phase Island 13 C ECSMGE,PRAHA,23 13ECSMGE,PRAHA,23 Spread foundation with improvement of SCP around PTB and railway station Geological profile at A-A section of Kansai Airport site 13ECSMGE,PRAHA,23 13ECSMGE,PRAHA,23

19 My research topics Application of numerical simulation Load & displacement behavior of bored pile Deformation behavior of soil structures on soft clay ground Improvement of clay ground with Sand compaction pile method Mechanical behavior of undisturbed clay and its numerical modeling Application of artificial intelligence to geotenical engineering. Etc.