外文翻譯--被動樁群樁-土相互作用的三維有限元分析（節(jié)選）

1、<p>　　1600單詞，8300英文字符，2650漢字</p><p><b>　　附錄一：英文原文</b></p><p>　　3D finite element analysis</p><p>　　on pile-soil interaction of passive pile group</p><p&g

2、t;　　1 Introduction</p><p>　　The majority of piles are designed to support “active” loads, that is, loads from superstructure are directly transferred to the pile foundation by the cap. However, in many cases

3、, piles are not designed to withstand “passive” loads, which are created by the deformation and movement of soil surrounding the piles due to the weight of soil and the surcharge. These passive loads may lead to structur

4、al distress or failure. Examples of these cases include piles supporting bridge abutments adjacent to</p><p>　　Several empirical and numerical methods have been proposed for analyzing the response of single

5、pile and pile group subjected to lateral loading from horizontal soil movements. A comprehensive review on these methods has been made by STEWART et al. Most of the numerical methods that have been proposed utilize the f

6、inite element method or the finite differential method. For pile groups, the plane strain finite element method was adopted by STEWART et al. In the study by STEWART et al, the piles w</p><p>　　In this work,

7、 the distribution of soil contact stress around piles and the lateral pressure were obtained, the pile groups deformations in different rows were investigated, and the lateral pressures on the (2×1) pile group and o

8、n the (2×2) pile group were compared.</p><p>　　2 Analytical model</p><p>　　The basic problem of a passive pile group subjected to soil movement is shown in Fig.1, where h1 is the depth of t

9、he soft soil layer, h2 is the depth of stiffer stratum, and L is the total pile embedded length.</p><p>　　Fig.1 Schematic diagram of pile group subjected to soil movement</p><p>　　In reality, bo

10、th vertical and lateral soil movements always concurrently occur. In order to simplify the problem, only the lateral soil movement was analyzed in this paper. In the analysis, pile was modeled as elastic material, wherea

11、s soil was assumed to be elastic-plastic complying with the Drucker-Prager yield criterion. The surface-surface contact elements were used to evaluate the interaction between pile and soil. The pile surface was establish

12、ed as “target” surface (Targe 170), and the so</p><p>　　Fig.2 Schematic diagram of normal contact stresses on pile</p><p>　　By projecting the normal contact stresses on the x-axis, the resultant

13、 force per unit length, F, in that direction was calculated. The average lateral pressure on pile was then p=F/d, as illustrated in Fig.3.</p><p>　　Fig.3 Schematic diagram of average lateral pressure</p&g

14、t;<p>　　Two types of pile groups were investigated in this paper, and the arrangement of piles is shown in Fig.4.</p><p>　　Fig.4 Arrangement of piles: (a) (2×1) Pile group; (b) (2×2) Pile gr

15、oup</p><p>　　3 (2×1) Pile group</p><p>　　The finite element mesh of (2×1) pile group is shown in Fig.5. In order to investigate the response of the pile group in soft soil layer, the s

16、maller elements were used in the mesh. The geometry and material parameters were employed in the study by BRANSBY and SPRINGMAN, d=1.27 m, L=19 m, h1=6 m, h2= 13 m, q=200 kPa. The material parameters can be seen in Table

17、 1.</p><p>　　Fig.5 3D finite element model for analysis of (2×1) pile group</p><p>　　Table 1 Material parameters for pile and soil</p><p>　　Fig.6(a) shows that the bending defo

18、rmations of the piles are very serious, especially in the soft soil layer. In addition, the surrounding soil reaches its plastic state, as shown in Fig.6(b).</p><p>　　Average lateral pressures on the piles a

19、re shown in Fig.7 for a surcharge of 200 kPa. The pressure distributions of this study agree well with the deduced values from the double differentiation of centrifuge bending moment data. The results are also in accor-d

20、ance with the those of BRANSBY and SPRINGMAN in the soft soil layer. The pile behavior in the stiffer stratum is not very well replicated due to both the coarse mesh and the simplistic constitutive model used in the stud

21、y by BRANSBY and SPR</p><p>　　Fig.6 Schematic diagrams of deformed piles(a) and plastic zone of soil(b)</p><p>　　Three different horizontal cross-sections of the piles were investigated. In the

22、first case, the cross-section is 2 m below the cap (in the soft soil layer); in the second case, the cross-section is 8 m below the cap (in the stiffer stratum); and in the third case, the cross-section is 16 m below the

23、 cap (near the pile bottom). The distributions of normal contact stresses are shown in Fig.8. Separation appears between soil and pile, where the contact stresses come to zero. This phenomenon exists</p><p>

24、　　Fig.7 Average lateral pressure on (2×1) pile group: (a) Rear pile; (b) Front pile</p><p>　　Fig.8 Distributions of normal contact stresses on (2×1) pile group (in kPa): (a) 2 m Below pile cap of r

25、ear pile; (b) 2 m Below pile cap of front pile; (c) 8 m Below pile cap of rear pile; (d) 8 m Below pile cap of front pile; (e) 16 m Below pile cap of rear pile; (f)16 m Below pile cap of front pile</p><p>　　

26、Fig.9 shows the pressures acting mainly on the rear pile due to the “barrier” effect from the rear pile near the surcharge in the stiffer ground. For the soft ground, soil will move laterally past the piles under the act

27、ion of surcharge, causing passive lateral pressures both on rear pile and front pile. The “barrier” effect is weakened, as shown in Figs.10 and 11. It is also been found that the pressures on the piles are rightward in t

28、he soft soil layer. In contrast, the pressures are leftward </p><p>　　Fig.9 Average lateral pressures on piles for stiffer ground</p><p>　　Fig.10 Average lateral pressures on piles for 10 m- thi

29、ckness soft ground</p><p>　　Fig.11 Average lateral pressures on piles for soft ground</p><p>　　4 (2×2) Pile group</p><p>　　The finite element mesh of (2×2) pile group is s

30、hown in Fig.12. The geometry and material parameters are the same as those of the (2×1) pile group. The deformation of the (2×2) pile group is shown in Fig.13.</p><p>　　Fig.12 3D finite element mod

31、el for analysis of (2×2) pile group</p><p>　　Compared with the (2×1) pile group, the resistance to soil movements of the (2×2) pile group is more noticeable. The reasons cover two important as

32、pects. On the one hand, the (2×2) pile group stiffness is greater than that of the (2×1) pile group as a whole, on the other hand, for the (2×2) pile group, the soil arching effect is formed between the pi

33、le and pile in the same row, except </p><p>　　Fig.13 Schematic diagram of deformed (2×2) pile group</p><p>　　for the “barrier” effect from the rear piles. However, the soil arching effect w

34、ill not come into being for the (2×1) pile group.For the same pile rows, the pressures distributions of the (2×2) pile group are very similar to those of the (2×1) pile group, but the values are less than

35、those on the (2×1) pile group, as shown in Figs.14 and 15.</p><p>　　Fig.14 Comparison of average lateral pressures on rear piles for different pile groups</p><p>　　Fig.15 Comparison of aver

36、age lateral pressures on front pilesfor different pile groups</p><p>　　5 Conclusions</p><p>　　1) Three-dimensional finite element modeling of method (2×1) and (2×2) passive pile groups

37、 loaded by lateral soil movements due to adjacent surcharge is presented, in which the nonlinearities of the plasticity of soil, large displacement and pile-soil contact are considered. The normal pile-soil contact stres

38、s and the average lateral pressure along the pile are obtained.</p><p>　　2) The lateral soft soil movement and the pile-soil interaction are revealed using three-dimensional finite element method. The separa

39、tion between pile and soil is reasonably modeled and the lateral pressure acting on the pile is properly estimated.</p><p>　　3) The adjacent surcharge may result in significant lateral movement of the soft s

40、oil and considerable pressure on the pile is high due to adjacent surcharge, which should be taken into account in the design of passive piles.</p><p>　　4) The pressures on varying rows of pile groups are di

41、fferent. The pressure acting on the row near the surcharge is higher than that on the other row due to the "barrier" and arching effects in pile groups.</p><p><b>　　附錄二：中文譯文</b></p&g

42、t;<p>　　被動樁群樁-土相互作用的三維有限元分析</p><p><b>　　1 引言</b></p><p>　　從樁土相互作用角度看，大多數樁的設計屬于主動樁，直接承受上部結構傳來的荷載并主動向土體傳遞應力。但是，在許多時候，樁身設計并未充分考慮承受被動荷載的情況，即作用在樁身上的側向壓力是由樁周圍土體在自重或堆載作用下發(fā)生變形和運動而引起的。

43、在一定情況下，這種被動荷載可能會導致結構失效，引發(fā)工程事故。例如在高架橋樁基附近進行打樁、開挖或者隧道掘進作業(yè)，或者在滑坡上的樁基礎都會導致相應樁身承受較大被動荷載。</p><p>　　目前，已經有許多專家學者采用經驗方法或者數值模擬的方法對這種土體水平運動作用下樁的響應特性進行了分析。Stewart等人對這些理論進行了總結概括，多數數值計算采用有限單元法或有限差分法。對于群樁, Stewart等采用平面應變有

44、限元模型進行了分析，在分析過程中，樁用等效板樁墻代替，這種系統行為的反應特性依賴于事先確定的樁上側向壓力和土位移(土體相對于樁的位移)的關系，沒有很好地模擬樁-土的相互作用。后來 Bransby和Springman 等使用三維有限元進行分析，但受制于當時計算機性能，網格劃分較粗，也沒有深入分析樁周土接觸應力的分布特點。實際上，這種類型的樁土相互作用需要綜合考慮土體材料的非線性，大應變和樁土間的接觸行為。非線性的影響因素包括軟土層厚度，土

45、體性質，粒徑大小，基樁數量與間距以及來自上部結構的約束等。目前為止，許多專家學者已就部分影響因素的影響機制進行了研究。</p><p>　　本文中筆者將在前人的研究基礎上建立三維有限元模型對被動樁身側向壓力分布以及沿樁周的土壓力分布進行了研究，同時對不同排群樁（2×1群樁實驗組與2×2群樁實驗組）在變形上的差異進行對比分析。</p><p><b>　　2 分

46、析模型</b></p><p>　　圖1為附加荷載作用下被動群樁受土體移動影響的示意圖，軟土層厚為h1，硬土層厚度為h2，樁長為L。</p><p>　　圖1樁土相互作用原理圖</p><p>　　實際中，土體的豎向位移與側向位移總是同時存在。為了簡化問題，本實驗中只考慮土體的側向位移對群樁的影響。分析時，樁采用彈性材料，土用彈塑性DP材料來模擬，樁-土

47、間設置接觸單元模擬土與樁交界面的相互作用，采用面-面接觸形式，在2個接觸面上，取樁表面為目標面(Targe170)，與樁表面接觸的土體面作為接觸面(Contac174)， 2個面合起來形成接觸對。整個過程利用高性能計算機工作站上的ANSYS軟件進行三維分析，采用接觸單元后,可以方便地得到樁的法向接觸壓應力，如圖2所示。</p><p>　　圖2作用在樁身的法向接觸壓應力</p><p>　

48、　將法向壓應力向x軸投影，可求得x方向上作用在單位長度樁上的土的側向合力F，則樁的平均側向壓力p=F/d，如圖3所示。</p><p>　　圖3樁上的平均側向壓力示意圖</p><p>　　現在研究二維平面上兩種類型的群樁，樁的具體布置如圖4所示。</p><p>　　圖4樁的布置：(a):(2×1)群樁；(b):(2×2)群樁</p>

49、;<p>　　3 (2×1) Pile group</p><p>　　圖5為(2×1)群樁的有限元模型，為了更好地研究群樁在軟土層中物理力學響應，此次研究對軟土層的網格劃分較細。整體模型與材料參數取自Bransby與Springman在文獻9中的相關研究。其中，d=1.27 m，L=19 m， h1=6 m，h2= 13 m，軟土層表面作用 200 kPa 的均布荷載。各材料參

50、數列于表1。</p><p>　　圖5 (2×1)群樁的三維有限元模型</p><p><b>　　表1樁、土材料參數</b></p><p>　　計算所得樁的彎曲變形如圖6(a)所示，由圖6(a)可知：位于軟土部分的樁發(fā)生了嚴重的變形，同時樁周土體也發(fā)生了嚴重的塑性屈服，如圖6(b)所示。</p><p>　

51、　在200kPa附加荷載作用下，土體作用在樁上的平均側向壓力如圖7所示。從圖7可以看出，本次試驗所得壓力分布與文獻9中的離心模型試驗壓力分布非常吻合，同時結果也與Bransby和Springman在軟土層中的測試結果一致。但樁在硬土層中的試驗結果偏差較大，一方面是因為為適應計算機的計算能力，對硬土層的網格劃分較粗糙，另一方面是使用了Bransby和Springman提出的一種簡單的本構模型。在實際工程中，位于硬土層中的樁，隨著埋深的增大

52、，土對樁的側向壓力將明顯減小。采用更細的網格劃分與更復雜的硬地層土體本構模型將會更好地解決這一問題。</p><p>　　圖6 群樁變形(a)及樁周土塑性區(qū)域(b)</p><p>　　分析不同深度處土對樁的徑向壓力，取3個橫斷面，第一個橫斷面位于地面以下2m（位于軟土層中），第二個橫斷面距地面8m（位于硬土層中），第三個橫斷面位于地面以下16m（接近樁底端），各斷面上的徑向壓力分布如圖8

53、所示。從圖8中可以看出，樁土分離處徑向壓力為0，這種現象只存在于土壤和樁之間的接觸單元中。由于后排樁對土體運動的明顯阻擋，對前排樁起到一個“遮擋”的作用，因此，前排樁上的接觸應力和側向壓力要比后排樁小得多。</p><p>　　圖7 (2×1)群樁的平均側向壓力：(a)后排樁，(b)前排樁</p><p>　　圖9展示了在硬土地層中，由于靠附加荷載近的后排樁的“遮擋作用”，側向壓

54、力主要作用在后排樁上。而在軟土地層中，在附加荷載作用下，土體則會繞過后排樁作用在前排樁上，使前排樁和后排樁同時作用有被動側向壓力，后排樁的“遮擋”作用明顯降低，如圖10和圖11所示。同時也可以發(fā)現，在軟土層中，作用在樁上的側向壓力在右側，相反，在軟土層與硬土層交界面的下方，側向壓力則是在左側。</p><p>　　4 (2×2) 群樁</p><p>　　(2×2)群樁

55、的有限元模型如圖12所示，其幾何形狀與各材料參數與(2</p><p>　　圖8 (2×1)群樁不同樁深處土對樁的徑向壓力(單位：kPa)：(a)z=2m后排樁；(b) z=2m前排樁；(c) z=8m后排樁；(d) z=8m前排樁；(e) z=16m后排樁；(f) z=16m前排樁</p><p>　　圖9地基全為硬土時樁的平均側向壓力</p><p>

56、　　圖10軟土層厚度為10 m時樁的平均側向壓力</p><p>　　圖11地基全為軟土時樁的平均側向壓力</p><p>　　×1)群樁相同。(2×2)群樁的變形如圖13所示。</p><p>　　圖12（2×2）群樁的三維有限元模型</p><p>　　圖13 (2×2)群樁變形</p>

57、<p>　　與(2×1)群樁相比，(2×2)群樁對控制土體位移的效果更明顯，原因有兩個：一是(2×2)群樁的整體剛度比(2×1)群樁更大，其次對于(2×2)群樁，不僅有后排樁對土的“遮擋”作用，還有樁間土的土拱效應的影響，這在(2×1)群樁中是不存在的。對于同排樁而言，(2×2)群樁中的側向壓力分布規(guī)律與(2×1)群樁上的非常相似，但是側向壓力

58、值要比(2×1)群樁上的小，如圖14和15所示。</p><p>　　圖14不同群樁的后排樁的平均側向壓力比較</p><p>　　圖15不同群樁的前排樁的平均側向壓力比較</p><p><b>　　5 結論</b></p><p>　　1) 通過三維有限元模型模擬了由附加荷載導致的土體水平移動在被動樁群(2

59、×1)和被動樁群(2×2)上產生的樁土相互作用。在模擬過程中，考慮了土體變形的非線性特性與大變形特性，在樁土接觸面上引入了接觸對。最后獲得了樁土法向接觸應力和沿樁身的平均側向壓力。</p><p>　　2) 利用三維有限元法，揭示了軟土側向移動與樁土相互作用的機理，恰當地模擬了樁土分離以及合理估算了樁側壓力。</p><p>　　3) 樁周附加荷載可能會引起軟土出現顯著