離心機(jī)模型試驗混凝土在砂土上的承載能力-畢業(yè)論文外文翻譯

1、附錄a外文文獻(xiàn)及其翻譯japanese geotechnical society special publicationthe 15th asian regionalconference onsoil mechanics and geotechnical engineeringbearing capacity of hybrid suction foundation on sand with loading direction via centrifuge model testjae hyun kim surin kim ", dong soo kim n jun ung youn

2、iii), dong joon kim iv) and sung hyun jcc v)i) ph.d student, department of civil engineering, kaist, 291 daehak-ro, yuseong-gu, daejeon, 305-701, republic of korea.ii) professor, department of civil engineering, kaist, 291 daehak-ro, yuseong-gu, daejeon, 305-701, republic of korea.iii) director, hyu

3、ndai engineering and construction co., ltd,446912, yongin-si, republic of korea.iv) chief research engineer, hyundai engineering and construction co., ltd,446912, yongin-si, republic of korea.v) general manager, hyundai engineering and construction co., ltd,446-912, yongin-si, republic of koreaabstr

4、actsuction caisson is widely used to support offshore structure. however, this type of foundation may not provide sufficient resisting capacity economically under external loads. recently, to give an increased capacity on the foundation, hybrid foundation concept was proposed to satisfy engineering

5、needs as well as cost reduction of structures. hybrid foundation concept is combination of skirted mat and suction caisson (s). suction caisson (s) is fitted on the mat foundation intended to increase load capacity. this paper investigates the behavior of a hybrid suction foundation installed in san

6、d layer for vertical and lateral loads, respectively. a series of centrifuge test have been conducted to assess the load capacity of the hybrid foundation and compared to those of the conventional single suction caisson. the primary goal of this study is to comprehend the effect of the mat compartme

7、nt on foundation behavior under loading directions, and corresponding bearing capacity. finally, feasibility of the hybrid foundation for offshore foundation was confirmedkeywords: suction caisson, hybrid foundation, bearing capacity, centrifuge modelling, sand1 introductionsuction foundation is use

8、d in offshore industry world-wide as it can be installed by suction using diflerential pressure inside and outside the caisson, enabling the pre-loading in a short time as well as minimizing the need for additional equipment for the installation. as the demands for offshore development, combined wit

9、h the continue depletion of natural resources has resulted in offshore development moving beyond the shallow waters into deeper waters and harsh environments. in perspective of these situations, suction induced foundation (or anchor) is being considered to be the most efficient and robust solution f

10、or supporting offshore structures.in offshore, the foundations are usually exposed by the various combinations of loadings. it may come from currents (waves), expansion / contraction of pipe lines linked to the structures due to the thermal changes before and after the operation or loads transferred

11、 from mooring lines. typically, they applied on the structure in the horizontal forces with relatively small vertical load due to a low selfweight of the structure.suction caisson are large diameter steel cylinders with open ended at the bottom. in the design perspective, large diameter suction cais

12、son is believed to provide higher holding capacity than small one toresist high external loads however, manufacturing and transporting costs as well as installation are increased inefficiently. therefore, new concept of suction caisson to increase the holding capacities while reducing the cost is ne

13、eded.recently, hybrid suction foundation that combination of suction caisson (s) with large mat foundation to increase holding capacity while reducing structural cost has been considered. in some case, mat foundation with multi small suction caissons, called hybrid group suction foundation, can be a

14、lternative (fig.1) hybrid foundation concept and its benefit are well summarized in gaudin et al. (2011) and bienen et al (2011). many studies related with holding capacity of hybrid foundation under various loading conditions in homogeneous clay have been investigated by using the numerical simulat

15、ion and to a lesser by the centrifuge model test gaudin et al. (2011); bienen et al. (2011; 2012); dimmock et al. (2013) and fu et al. (2014). however, the behaviour of the hybrid foundation with loading directions (or combined loadings) in the sand layer is not yet well understoodin this paper, the

16、 behaviour of hybrid suction foundation placed on sand layer under uniaxial vertical and horizontal loadings was investigated using the centrifuge model test. the hybrid suction foundation which is combination of one suction caisson and the hopper over the container, nozzle size and falling height.

17、total three soil models with relative density, dr = 60%, were prepared to a depth of450 mm and performed six model tests in the samples. the resulting soil model conditions are tabulated in table 2. the prepared soils were saturated at lg by dribbling the water from the soil surface up to about 30 m

18、m above the sample. the degree of saturation was enhanced by pre-spinning the model up to 70g in the centrifuge before the loading tests.2 centrifuge model test2.1 geo-centrifugea series of centrifuge model tests were performed using a beam-type geotechnical centrifuge installed at kaist in korea wi

19、th 5 m radius. the maximum capacity of the centrifuge is 240 g-ton and can be accelerated up to 130g. the detailed description of the facilities can be found in kim et al (2013).2.2 test apparatus and loading systemthe load tests were conducted in the cylindrical container with inner diameter of 700

20、 mm and 900 mm height at 70g-level. in order to apply the vertical and horizontal loads on the foundation, in a uniaxial form, respectively, loading systems were set up. to simulate the vertical load on the foundation, the model was connected to the driving part of linear actuato匚 model and actuator

21、 were connected in a pin joint type with a pair of male and female, so that t h emodeli sfreet omove vertically but restricted in horizontal direction. it makes possible to allow soil settlement while ramping up the centrifuge acceleration. horizontal load was simulated by adopting the pulleys and w

22、ire system. the drive unit was mounted on a container to be moved horizontally and linked to the model foundation using a chain through pulleys fixed at the container wall. thus, pure horizontal load was applied on the top of foundation by displacing an actuator position with constant rate, drawing

23、the foundation horizontally. the manufactured miniature loadccll was connected between the chain and the caisson with pin-joint type such that the horizontal load was directly measured at very close the model. two laser sensors were positioned at the different level. thus, displacement or rotation o

24、f the foundation was monitored of thin and light plate standing on the model. in addition, the images was captured at same interval in front of the model during the test to perform the image analysis. suction caisson actuator lvdt load-cell pin actuator pulley wire load cell laser sensors load cell

25、suction caisson2.3 model descriptiontwo types of model were prepared to perform a series of tests; conventional suction caisson and single suction caisson with circular mat. single suction foundation have caisson outer diameter (d c ) m of 71.4 mm with 3 mm thickness (t c ) m ? corresponding to prot

26、otype dimension (d c ) p = 5 m and (t c ) p = 210 mm. caisson length to diameter ratio (l/d c ) is 1 the thickness of the model was over-designed than the typical prototype caisson dimension by concern for structure failure during the tests (typically, t c /d c = 0.3 0.4% for sand, tran and randolph

27、 (2008). hybrid foundation have same dimensions with those of the single caisson model and the mat dimension of d m = 142.8 mm, representing a prototype of (d m ) p = 10 m. the dimension of foundation are summarized in table 1. table 1. dimensions of the model foundations.lvdtactuatorl.oadccll,load

28、cell pulley、actuator(a) suclioncaislaser sensors h wireload cell *|suction caisson (b)fig. 2. scheme of loading systems for vertical and horizontal loadings: (a) vertical loading system; (b) horizontal loading system.table 1. dimensions of the model foundations.modelitemdimensionsmodel (mm)prototype

29、 (in)conventional (single)caisson dia. (dc)71.45skirt length (l)71.45tip thickness (k)30.21( aisson dia. (dj71.45hybridmat dia. (dm)142.810(single 十 mat)skirt length (l)71.45tip thickness (l)30.212.4 soil samplethe clean silica sand material, which is mainly comprised with quartzite, was used in thi

30、s study. the soil properties of the sand used in this study are; specific gravity g s = 2.65, mean grain size (d 50 ) = 0.237, maximum dry density, y max = 1.64 and minimum dry density, y min = 1.24.diy sand were prepared by a pluviation method using an automated sand rainer. homogeneous sand layer

31、was achieved by controlling the travel speed of the hopper over the container, nozzle size and falling height. total three soil models with relative density, d r = 60%, were prepared to a depth of 450 mm and performed six model tests in the samples. the resulting soil model conditions are tabulated

32、in table 2. the prepared soils were saturated at lg by dribbling thewater from the soil surface up to about 30 mm above the sample. the degree of saturation was enhanced by pre-spinning the model up to 70g in the centrifuge before the loading tests.2.5 testing programtotal six tests were performed i

33、n the three soil samples. in the sample 1, two vertical loading tests were conducted on the single and hybrid foundations, respectively (denoted as test 1 and test 4). in the sample 3, two horizontal load test were conducted by using the two caissons (test 3 and test 6). here, the tests were carried

34、 out in the conditions that the base (or mat) of the caissons is completely contacted to the ground. in the sample 2, the same tests done in sample 3 were conduct except that the mat (or base) is not attached to the ground surface (test 2 and test 5). in each sample, the tests for each model foundat

35、ion in the sample were performed under same boundary condition and the spacing between the models.all of the model foundations were installed up to predetermined depth by jacking using the vertical actuator at a constant rate of 1 mm/sec at lg. after installation of the foundation, centrifuge was ra

36、mped up to 70g in steps. then, the model foundation was displaced in the load directions with 0.05 mm/sec, ensuring fully drain condition during the load tests as recommended by finnie and randolph (1994).the results are discussed following the sign and symbol adopted by butterfield et al. (1997). t

37、he reference point is located at the soil surface in this study.table 2. test conditionsfoundationtest id 卯。loadingdirectionloading ydremark4rate(kn/m3)test 1°v14.6detachedtest 22) conventionalh14.7detachedtest 33)h0.0514.7attachedtest 4°vmm/sec14.6detachedtest 52) hybridh14.7detachedtest

38、63)h14.7attachedpie 2;3) sample 3,4> whether the foundation base (or mat) fully attached to the soil surface or not.3 testing results and discussions3.1 ultimate vertical capacityvertical holding capacity of suction foundation was investigated. all the results are also discussed in a prototype sc

39、ale figure 3 presents two load -displacement curves observed in the displacement - controlled vertical loading tests. vertical loads are alsoplotted against normalized displacement, d/d c，as well as bearing capacity factor, 2v/ayd c, where a is area of suctions caisson, in a dimensionless fbnri.the

40、loaddisplacements observed in vertical loading tests were monotonically increased with penetration without mobilization of peak strength, which reflect the characteristics of punching behavior. in addition, it is evident that the vertical bearing capacity of the hybrid foundation is higher than the

41、conventional caisson due to mat foundation with enlarged area. for test 4, the load-displacement shape was changed in around d/dc =0.07 (denoted as symbol in fig. 3) where the mat is fully attached on the soil surface. thereafter, load was dramatically increased (denoted as symbol ).ultimate bearing

42、 capacity were determined where the tangential intersection of two linear lines parallel to the initial and later parts of the measurement and its corresponding point of the curves (see, red dots in fig. 3). the determined ultimate bearing capacities showvult = 81 mpa (2v/ay,dc =113) at d/dc = 0.21

43、for test 1 and vult = 155 mpa (2v/ay,dc = 216) at d/dc = 0.21 for test 4. the ultimate bearing capacity of hybridfoundation is about 1.91 times larger value than the value of conventional suction foundation.oddlogq.) n一 .§-«.2匕亠10.6ntcmi singlehybrid i.y0000.10.20.30.40.5normalized displac

44、ement* dpfig. 3 vertical load curves with penetration3.2 ultimate horizontal capacityfigure 4 presents the bearing capacity for the horizontal loading for conventional single caisson and hybrid fbundation. horizontal displacement of the caisson at the reference point is calculated from measurements

45、of two laser sensors positioned at different levels.all the curves reaches a plateau results show that the horizontal load capacities of hybrid foundation are much higher than those of the single suction caisson. it may come from the mat foundation which aids the resisting force from the external lo

46、ad by extending the resisting area. the determined ultimate horizontal capacities are summarized in table 3. it is noteworthy that the load-displacement trend of test 5 in a condition that the mat foundation is not fully contacted with the ground surface, shows double curvature shape this trend is c

47、ontrary to the behavior of test 6 in a condition of fully contact between the mat and ground it can be explained by the rotation behavior of the foundation. firstly, only the part of caisson resisted horizontal load because the mat was detached from the soil surface as denoted in fig. 4 (see, symbol

48、 ).as the load increases, the foundation began to rotate, and the protruded mat beyond the caisson initiated to intrudeinto the ground surface (fig 4, see ).finally, the mat was completely penetrated into the ground and full holding capacity of the hybrid foundation was reached. it can actually happ

49、en in the field because the soil heaving may occur during the suction installation process so that the caisson caif t penetrate up to the full penetration (houlsby and byrne, 2005).for test 6, unlike the test 5, horizontal load continuously increased and reached to the ultimate holding capacity. the

50、 different rotation behavior could be confirmed by the captured images with same interval during the tests as shown in the fig. 5.3.4 conclusionscentrifuge test have been conducted to explore the feasibility of hybrid suction foundation for the offshore structure in sand. the ultimate bearing capaci

51、ties for the vertical and horizontal loadings were assessed by using the model tests. from a series of test, hybrid foundation which is combination of the circular mat and suction caisson, shows the potential as an alternative subsea foundation by providing enhanced holding capacitiesthe results als

52、o showed different behavior with the attached condition between the mat and soil surface. however, additional analyses would be required to confirm the effect of interaction between the mat and soil on the capacities- further investigation for the hybrid foundation is currently on-going. with the ce

53、ntrifuge model tests, finite element analysis is conducting in parallel to investigate the bearing capacity with the loading directions and to validate the test results 4acknowledgementsthis study was supported by a grant from the future flagship r&d program (10042452) of korea minis-try of trad

54、e industry and energy "engineering technology development for the 3,000m deepwater subsea equipment and urf installation to advance to deepwater offshore plant market project. the authors also thanks to the collaborations of hyundai engineering and construction, co., ltd.references1) bienen, b.

55、 et. al. (2011): numerical study of the combined load capacity of a hybrid foundation, proc. int. symp. off. and pol. eng.f isope20u, maui, hawai, usa, 556-562.2) butterfield, r., houlsby, g. t., and gottardi, g. (1997): standardised sign conventions and notation for generally loaded foundations, ge

56、otechnique, 47(4), 1051-1052.3) dimmock, p. et al. (2013): hybrid subsea foundations for sub-sea equipment, journal of geotechnical and geoemnron-mental engineering, 139(12)，2182-21924) finnie,and randolph, m.e (1994): punch-through and liquefaction induced failureof shallow foundations on calcareou

57、s sediments, proc, of int. conf, on behaviour of off-shore structures, boston, usa, 217-230.5) fu, d. et al. (2014): undrained capacity of a hybrid subsea skirted mat with caissons under combined loading, canadian geotechnical journal. 51,934-9496) gaudin, c. et al. (2011): centrifuge experiments of

58、 a hybrid foundation under combined loading, proc. int. symp. off. and pol. eng, isope 2011, maui, hawai, usa. 386-392.7) houlsby, g t., and byrne, b. w. (2005): design procedures for installation of suction caissons in sand, proceedings of the ice- geotechnical engineering, 158(3), 135-144.8) kim, ds et al. (2013): a newly developed state-of-the-art geotechnical centrifuge in korea, ksce journal of civil engineering, 17(1), 77-84.9) tran, m. n., and randolph, m. f. (2008): variation of suction pressure during c