外文翻譯---軟土路基沉降計算問題探討

1、<p><b>　　XX學院</b></p><p>　　本科畢業(yè)論文外文資料翻譯</p><p>　　系 別： 工程技術系 </p><p>　　專 業(yè)： 土木工程 </p><p>　　姓 名： XX </p><p>　　學

2、 號： XX </p><p>　　2011年 4 月 10 日</p><p><b>　　外文資料翻譯譯文</b></p><p>　　軟土路基沉降計算問題探討</p><p>　　摘要:在軟土地區(qū)修筑高速公路，最重要的是控制路基沉降。探討軟土路基沉降的計算方法，分析了影響沉降的一些主要因素，并

3、指出軟土路基沉降計算存在的困難與問題，最后提出了自己的建議。</p><p>　　關鍵詞 軟土路基 沉降計算</p><p><b>　　1引言</b></p><p>　　隨著社會經濟的發(fā)展，為滿足交通現(xiàn)代化的要求，我國迫切需要建設高速公路網。路基的不均勻沉降會破壞或降低高速公路的質量，影響行車的舒適性和安全性。在軟土地區(qū)修筑高速公路，最關鍵

4、的問題就是控制路基的沉降。因此，高速公路路基沉降的分析與計算已經引起廣泛的關注。本文就軟土路基的沉降計算問題做一些探討。</p><p>　　2軟土路基的沉降計算</p><p><b>　　2.1沉降的組成</b></p><p>　　在軟土地區(qū)修筑高速公路，必然導致路基的下沉。通常認為沉降是由瞬時沉降、主固結沉降與次固結沉降三部分組成。即&

5、lt;/p><p>　　S=Sa+Sd+Se</p><p>　　式中:Sd—瞬時沉降，由于土體的側向變形引起的附加沉降;</p><p>　　Se—主固結沉降，是加荷后土體的體積壓縮變形引起的沉降;</p><p>　　Sa—次固結沉降，由于土體蠕變而發(fā)生的沉降;</p><p>　　由于土體側向變形引起的那部分沉降，其

6、實并不是瞬時發(fā)生的，它在沉降的整個過程顯示出其影響，對此作了詳細的論證。因此將瞬時沉降分量稱為不排水沉降更為合適。</p><p>　　2.2路基沉降計算方法</p><p>　　目前計算沉降及沉降速率的方法可歸納為以下幾類。</p><p>　　2.2.1常規(guī)計算方法</p><p>　　這是工程中最為常用的計算方法，按分層總和法計算最終沉

7、降，采用一維固結理論計算沉降速率。計算分層沉降時考慮不排水沉降Sa、主固結沉降S,和次固結沉降S，三部分沉降。不排水沉降Sa用彈性理論或一些經驗公式計算，較好經驗公式的有:主固結沉降S,的計算可用一維的e-p曲線法或考慮土體應力歷史的e - lgp曲線法，或Skempton和Bjerrum法(1957年);次固結沉降S。采用次固結系數(shù)計算。工程實際中經常采用主固結沉降乘以一個修正系數(shù)m.，的辦法來計算總沉降量。沉降速率則根據(jù)Terzag

8、hi (1923年)一維固結理論或Gibson (1967年)一維有限非線性應變固結理論，有限非線性應變固結理論考慮了土體壓縮性和滲透性與孔隙比的非線性變化，以及土體自重應力等方面的因素，較Terzaghi一維固結理論合理。</p><p>　　2.2.2應力路徑法</p><p>　　Lambe (1967年)提出用應力路徑法來計算沉降川。軟豁土受荷載作用后，往往有兩個過程:首先是形變，

9、然后是體變。加荷初始，孔隙水一時來不及排出，孔隙水壓力上升，這就相當于固結不排水過程，體積不變。隨著孔隙水壓力的消散，體積</p><p>　　壓縮，有效法向應力增加，而偏應力不變，這相當于固結排水過程。因此，沉降就可分成兩部分計算，通過模擬現(xiàn)場實際加荷條件，進行室內固結不排水和固結排水試驗，分別量測不排水應變和排水應變，由此求得不排水沉降與固結排水沉降。應力路徑法對于認識沉降機理，分析常規(guī)計算中可能產生的誤差趨

10、勢，都是很有益的。但該法使用較為麻煩，試驗技術要求過高，目前尚未被工程界采用。</p><p>　　2.2.3有限單元法</p><p>　　有限單元法可以考慮復雜的邊界條件、土體應力應變關系的非線性特性、土體的應力歷史、水與骨架上應力的禍合效應，可以模擬現(xiàn)場逐級加荷和處理超填土問題，能考慮側向變形、三維滲流對沉降的影響，并能求得任一時刻的沉降、水平位移、孔隙應力和有效應力的變化，使得計算

11、所得總沉降量及沉降速率等結果越來越接近實測結果川。有限元分析時，將路堤和地基作為整體劃分網格，取孔隙應力、豎向位移和水平向位移為基本未知量，采用理論上較嚴密的比奧固結理論，在路堤荷載作用下，根據(jù)土體的勁度和滲透性建立方程組，從而解得孔壓與位移。有限元確實是一種較為完善的方法，但是由于其計算參數(shù)多，且需通過三軸試驗確定，程序復雜難以為一般工程設計人員接受，在實際工程中沒有得到普遍應用，只能用于重要工程、重要地段的路基沉降的計算。此外，有限

12、元目前很難考慮大變形固結問題即幾何非線性，往往使計算結果偏離較大。</p><p>　　2.2.4曲線擬合法</p><p>　　根據(jù)現(xiàn)場前期實測沉降資料，用曲線擬合法，可以預測沉降發(fā)展規(guī)律，推算最終沉降量，由此確定路面鋪筑時間。曲線擬合法有指數(shù)曲線法、雙曲線法、高木俊介法或曾國熙1975年提出的高木俊介改進法等。高速公路軟土路基沉降隨時間的關系一般較符合雙曲線形式圖。但也有人認為雙曲線方

13、程本身沒有反映出地基土的固結速度，與沉降速率缺乏內在的聯(lián)系，用指數(shù)曲線法擬合更恰當。宰金氓認為這些方法均難以反映全過程的沉降與時間的關系，建議用泊松曲線預測沉降，但也只適用一級線性加載情況。</p><p>　　2.2.5反演分析法</p><p>　　反演分析法是近十幾年發(fā)展起來的一項新技術，它通過已有的沉降觀測資料，反演得到正分析中的某些輸人參數(shù)，使正分析得到的結果與實測沉降充分接近。

14、如可以通過反演分析確定原位固結系數(shù)，再根據(jù)'Terzaghi的一維固結理論推算最終沉降量及沉降發(fā)展過程;s7。黃少杰等(2000年)i9J用Merchant一維赫彈性固結模型進行了一維反演分析，在不考慮側向變形的條件下，建立了沉降與沉降速率的計算式，該式包含四個計算參數(shù)，分別反映主固結與次固結的沉降大小和發(fā)展快慢，用實測沉降進行反演分析，求得這些參數(shù)，即可計算總沉</p><p>　　降量和沉降速率。由于

15、采用豁彈性模型，次固結的影響可以得到考慮。</p><p>　　2.2.6人工神經網絡法</p><p>　　人工神經網絡法自20世紀80年代中后期以來，迅速發(fā)展為一個前沿研究領域，并廣泛應用于各個學科。目前，已有人將人工神經網絡運用于路基沉降計算。神經網絡具有集體運算和自適應能力，善于聯(lián)想、綜合與推斷，能夠對路基前期沉降資料進行分析，記憶存儲路基填土的基本性質，通過模擬填土性質、加載與變

16、形之間的復雜的函數(shù)關系，就可以進行路基沉降的預測。在用神經網絡分析路基沉降問題時，只要取三層網絡(輸人層、中間層、輸出層)?？紤]到土的非線性，輸出層取為荷載增量下的沉降增量;輸入層則為反映路基沉</p><p>　　降的主要因素(如施工加載方式、施工加載速率、施工間歇期、前期沉降值等);中間層為反映土的力學性質和變形特征(如土的重度、強度指標、壓縮系數(shù)、滲透系數(shù)、固結系數(shù)等)。建立起反映路基沉降影響因素與路基沉量

17、之間的映射關系的神經網絡后，就可以用已有的沉降觀測資料對網絡進行學習訓練，待到網絡誤差小于預先設定值時，網絡就能夠抽取并記憶填土的力學性質和變形特性，再輸人要進行預測的加載情況，就可以通過網絡預測出將要發(fā)生的沉降變形情況。神經網絡法預測沉降尤其適合于只有一些沉降觀測資料而無土性參數(shù)的J清況，與實測沉降誤差較小，有一定的發(fā)展前景。</p><p>　　2.3沉降計算方法的討論</p><p>

18、;　　以上介紹的六類方法中，前三類為沉降及沉降速率的預估，用于施工前的設計，而后三類根據(jù)前期沉降實測資料進行后期沉降的推算，‘指導后續(xù)施工，確定路面的最佳鋪筑時間，減少工后沉降量。目前，工程中最為常用的沉降預估還是采用常規(guī)討-算方法，沉降推算采用曲線擬合法，這是由于這兩類方法較其它方法來得簡單，工程技術人員便于應用。雖然其它方法可能精度更高，但由于過于復雜，對試驗技術和參數(shù)選取的要求過高或需要高深的數(shù)學理論，因此即使在將來，也不會在工程

19、中完全替代常規(guī)分析法。</p><p>　　3影響軟土路基沉降計算的一些主要因素</p><p>　　影響軟土路基沉降計算的因素很多，本文著重鄭澄鋒，等:軟土路基沉降計算問題探討討論以下幾個方面:</p><p>　　3.1土體自重應力的計算</p><p>　　軟土地基中的地下水位通常很高，對于地下水位以下的土體，當其液性指數(shù)為0<I

20、L<1時，土顆粒是否受到水的浮力作用，浮力多大，尚無法確定，從而影響到此種情況下的土中應力計算。目前只能按對工程不利情況考慮，在沉降計算中是采用浮容重計算自重應力。</p><p>　　3.2土中壓力隨沉降變化</p><p>　　當軟土地基上的荷載是填土時，一方面，在施工期間的地基沉降由后繼填土補填起來，從而使實際填土荷載大于原設計荷載;另一方面，當?shù)叵滤缓芨邥r，沉至地下水位以下

21、的填土會受到浮力作用，導致基底附加壓力減少。常規(guī)計算很難考慮這兩方面的影響。事實上，由于路基沉降導致的超填荷載與填土浸水后受到的浮力作用，對沉降量的影響具有互補性，故在沉降分析中應對這兩方面的影響綜合考慮，否則將會導致更大的誤差。</p><p><b>　　3.3側向變形</b></p><p>　　軟土變形中不僅包含彈性變形，也包含塑性變形。路堤荷載作用下，軟土的

22、固結過程中，側向變形也逐漸增大，土體的沉降不僅由于主應力引起的排水固結，還由于土體中不斷發(fā)展的側向變形。側向變形的大小與土的性質、軟土層的位置、路堤的高度等因素有關。如果在沉降計算中不考慮側向變形的影響，會使計算沉降一與實測沉降出現(xiàn)較大偏差。</p><p>　　3.4加載方式和加載速率</p><p>　　實際施工中的加載方式變化很大，采用不同的加載方式和加載速率，路基的沉降一時間曲線顯

23、著地不同。加載速率對初期沉降有明顯影響，而對后期沉降影響不大。填筑速率過快，土體沒有充分固結，會造成較大的工后沉降。</p><p><b>　　4小結與建議</b></p><p>　　(1)目前工程中常用的軟土路基沉降計算方法含有許多簡化假定，與實際情況不完全符合。進一步研究新的計算理論和計算方法，盡可能考慮多種因素的影響，又做到簡單直觀，方便工程設計人員使用。&

24、lt;/p><p>　　(2)土力學問題的分析與計算，目前仍處在半理論半經驗階段，計算參數(shù)的選用可能比計算方法更為重要。建議進行廣泛的試驗研究，深入了解各地區(qū)軟土的基本特性。</p><p>　　(3)由于高速公路路堤的設計一般以變形控制為主，對工后沉降量的要求很高。因此有必要建立高速公路專家設計系統(tǒng)，指導信息化施工，有效地控制工后沉降量。</p><p><b&

25、gt;　　外文原文</b></p><p>　　Soft soil subgrade settlement calculation problem is discussed</p><p>　　Abstract: in the soft soil area build highway, the most important is to control the embankmen

26、t settlement. Explore soft soil subgrade settlement calculation method, analyzes the influence on settlement, and points out some main factors existing in soft soil subgrade settlement calculation of the difficulties and

27、 problems, and finally puts forward some Suggestions.</p><p>　　Keywords: soft soil subgrade settlement calculation</p><p>　　1 introduction</p><p>　　With the development of social

28、economy, in order to satisfy the requirements, our traffic modernization construction of high-speed road urgently needed. The roadbed uneven settlement will destroy or reduce the quality of highway, affecting driving com

29、fort and safety. Built in the soft soil area highway, the most critical issue is control of subgrade settlement. Therefore, highway roadbed subsidence analysis and computation has attracted widespread attention. This pap

30、er of soft clay subgrade sett</p><p>　　2 soft soil subgrade settlement calculation</p><p>　　The composition of 210 settlement</p><p>　　Built in the soft soil area highway roadbed su

31、bsidence, must cause. Usually think settlement by the instantaneous settlement, the Lord is with consolidation settlement secondary consolidation settlement of three parts. namely</p><p>　　S = Sa + Sd + Se&l

32、t;/p><p>　　Type: Sd - instantaneous settlement, because the lateral deformation of soil caused additional settlement;</p><p>　　Sd - primary consolidation settlement with jose, is the volume of soi

33、l caused by compression deformation of settlement;</p><p>　　Ss - soil secondary consolidation settlement, due to the settlement of creep and happen;</p><p>　　Because the lateral deformation of s

34、oil caused that part settlement, actually not instantaneous happens, it in the whole process of settlement, which shows its impact has made the detailed demonstration. So will the instantaneous settlement component calle

35、d undrained settlement more appropriate.</p><p>　　2.2 embankment settlement calculation method</p><p>　　Current calculation method of the settlement and subsidence rate could be divided into the

36、 following categories.</p><p>　　2.2.1 conventional calculation method</p><p>　　This is the most commonly used in engineering calculation method of delamination summation-method calculation, acco

37、rding to final settlement, the 1-d consolidation theory calculation sedimentation rate. When calculating lamination settlement consideration not drainage settlement Sa and consolidation settlement S, and secondary consol

38、idation settlement S, three parts settlement. Undrained settlement with elastic theory or some Sa experience formula, better empirical formulas have: primary consoli</p><p>　　2.2.2 stress path method</p&g

39、t;<p>　　Lambe (1967) proposed with stress path method to calculate settlement sichuan. Soft soil after by load variable, often have two process: first is the deformation, then is the volume change. Add lotus initi

40、al, pore water temporary too late eduction, pore water pressure rise, this is equivalent to the consolidated undrained process, its volume. Along with the pore water pressure lifts, and volume</p><p>　　Compr

41、ession, the effective method to stress increases, and partial stress is changeless, the equivalent of consolidation drainage process. Therefore, settlement can be divided into two parts by simulation calculation, the act

42、ual add lotus conditions, indoor consolidated undrained and consolidation drainage experiment measured respectively undrained strain and drainage strain, thus seek undrained settlement and consolidation drainage settleme

43、nt. The stress path method to understanding subsidence </p><p>　　2.2.3 finite element method</p><p>　　Finite element method can consider complex boundary conditions, soil stress-strain relations

44、hip nonlinear characteristics of stress, soil water and the skeleton history, the disaster of the stress field gather the effect, can simulate uploaded and lotus and processing super filling problem, can consider the lat

45、eral deformation, the influence of 3d seepage settlement of any time, and can seek settlement, the pore stress and horizontal displacement, effective stress changes, made computation incom</p><p>　　2.2.4 cur

46、ve-fitting method</p><p>　　Based on the scene early measured settlement material, use curve-fitting method which can predict the development regularity, settlement of calculates final subsidence and then def

47、ine paving roadways time. Curve-fitting method, a index curve GaoMuJun hyperbola method, the method of interface or have countries GaoMuJun corvee 1975 proposed dielectric improvement method, etc. Highway soft soil subgr

48、ade settlement over time with the relationship is generally hyperbola form diagram. But also somebod</p><p>　　2.2.5 inversion analysis</p><p>　　Inversion analysis is developed nearly ten years,

49、a new technology, it through the existing settlement observation data, the analysis of the inversion get are losing people parameters, make some positive results and the measured settlement fully close. If can pass throu

50、gh inversion analysis to identify in situ consolidation coefficient, again according to the 1-d consolidation theory 'Terzaghi calculates final settlement quantity and settlement development process; S7. HuangShaoJie

51、 etc (2000) i9</p><p>　　Drop quantity and sedimentation rate. Since using variable elasticity model, the influence of the secondary consolidation can be considered.</p><p>　　2.2.6 artificial neu

52、ral network</p><p>　　Artificial neural network since the 1980s, rapid development since the middle for a frontier research fields, and widely used in various subjects. At present, already someone using the a

53、rtificial neural network to embankment settlement calculation. The neural network has collective operation and adaptive ability, is good at lenovo, comprehensive and assumptions of subgrade settlement, can analyze the da

54、ta and memory storage subgrade filling the basic nature of the filled soil properties, by simu</p><p>　　The main factors (such as down construction loading method, construction of loading rate, construction

55、intermittent period, the sedimentation value etc.); Layer of soil mechanics to reflect nature and deformation characteristics (such as soil severely, intensity index and the compression coefficient, permeability, consoli

56、dation coefficient, etc.). Establish reflect embankment settlement factors and the amount of roadbed sink the mapping relationship between after the neural network, we can use t</p><p>　　2.3 settlement calcu

57、lation method is discussed</p><p>　　Introduced above six types of method, the former three kinds of subsidence rate for settlement and estimate for construction design before, and then three categories accor

58、ding to the settlement of subsidence data calculation, 'the later determined pavement construction, guiding the follow-up time and reduce the best roadways quantity of post-construction settlement. At present, most c

59、ommonly used in engineering estimation to the subsidence is still USES conventional method, the settlement for - </p><p>　　3 influence soft soil subgrade settlement calculation of some of the major factor<

60、;/p><p>　　Influence of soft soil subgrade settlement calculation, this paper ZhengChengFeng many factors, such as: soft soil subgrade settlement calculation problem study discuss the following several aspects:&

61、lt;/p><p>　　3.1 gravity stress calculation soil</p><p>　　The soft soil foundation of underground water in underground water level, usually high, when the soil under sexual index 0 liquid < 1, &q

62、uot;IL soil particle if affected by the buoyancy of water effect, buoyancy, are not sure how much, thus affecting such a situation in the soil stress calculation. Currently only for engineering unfavorable conditions acc

63、ording to consider, in settlement calculation is calculated using float density gravity stress.</p><p>　　3.2 soil pressure with settlement changes</p><p>　　When on soft soil ground when the load

64、 is filling in construction period, on the one hand, the filled soil foundation settlement by subsequent fill up for, thus make the actual filling load is greater than the original design load; On the other hand, the loc

65、al water high under the sink to underground water level below the filled soil caused by buoyancy effect, basal additional pressure decrease. The conventional calculation is difficult to consider the influence of these tw

66、o aspects. In fact, th</p><p>　　3.3 The lateral deformation of </p><p>　　Soft soil deformation of elastic deformation includes not only, also contains plastic deformation. Embankment loads, soft

67、 soil consolidation process, the lateral deformation also increase gradually, the settlement of soil caused not only the main stress, but also because the soil drainage consolidation in the lateral deformation of the con

68、tinuous development of. With the size of the lateral deformation of soil properties, soft soil subgrade height, the position of related to such factors. If the</p><p>　　3.4 loading method and the loading rat

69、e</p><p>　　Actual construction big changes the loading method, using different loading method and the loading rate, roadbed subsidence time curve strikingly different. Loading rate on the initial settlement,

70、 and have an obvious effect on little influence on later settlement. The filling velocity too fast, the soil is not fully consolidation, can cause larger post-construction settlement.</p><p>　　4 summary and

71、Suggestions</p><p>　　(1) used in the engineering project of soft soil subgrade settlement calculation method contains many simplified assumption, and the actual condition is not fully comply with. Further re

72、search new computational theory and calculation method, as considering the influence of many factors, and do it is simple, intuitive, and convenient engineering design researchers used.</p><p>　　(2) soil mec

73、hanics problem analysis and calculation, remains a half experience stage, half theory parameters calculation method for the selection of more important than possible. Suggestions for extensive testing research, in-depth

74、understanding of regional soft soil basic characteristics.</p><p>　　(3) due to the design of highway subgrade with deformation control is given priority to, general thanked the amount of settlement after dem