土木工程外文翻譯--軟土地基上分期施工的路堤沉降預(yù)測方法

1、<p>　　Settlement prediction of embankment s with stage</p><p>　　LIU Song-yu（Institute of Geotechnical Engineering, Southeast University,Nanjing 210096,China）JING Fei（Institute of Geotechnical Engineerin

2、g, Southeast University,Nanjing 210096,China）</p><p>　　Abstract: The magnitude and rate of the settlement are the key elements subjected to design analysis of embankments on soft ground. The observational &l

3、t;/p><p>　　Institute of Geotechnical Engineering,Southeast University,Nanjing210096,China</p><p>　　methods based onfield measurement have indicated the promising results and become effective method

4、s to predict the final settlement, while the uncertainties of parameters and theories limit significantly the accuracy of settlement estimation. This paper presents an observational method to predict the settlement perfo

5、rmance of embankments with stage construction on soft ground based on Asaoka method. The case studies show the accordance of the predicting results with the field measured data. It i</p><p>　　Key words: sett

6、lement, embankment, observational method, stage construction</p><p>　　1. Introduction </p><p>　　Settlement and stability are two primary considerations systematically related to the design of a

7、n embankment on soft ground. The tools available for the stability evaluation seem to be satisfactory. The key element of long term behavior of the embankment routinely subjected to design analysis is the settlement. In

8、other words , the settlement analysis is the most appropriate approach to the embankment analysis .</p><p>　　The settlements of embankments on soft clays result from the consolidation and the lateral flow un

9、der the embankments. Many researches have been made on performance of embankments on soft ground.</p><p>　　Although many experiences have shown the practical value of the theory for estimating settlements an

10、d settlements rates , they also illustrated some of the problems in volved in making accurate prediction of the settlement .Duncan (1993) and Olson (1998) analyzed the uncertainties causing the shortcomings in the curren

11、t state of the art for settlement prediction respectively. These uncertainties sometimes make it difficulty or impossible to estimate the magnitude and rate of settlement for emban</p><p>　　It is desirable t

12、herefore to develop observational methods based upon which the settlement can be estimated once sufficient data has been recorded. Many researchers developed the settlement prediction methods on field measurement observa

13、tion , which have indicated promising results and become an accepted method to estimate final settlements and rates of settlements.</p><p>　　Stage construction is a typical procedure for embankments on the s

14、oft ground. With a certain period of consolidation at every stage construction ,the safety factor of the embankment can be generally raised and the post construction settlement may be reduced. The settlement - time curve

15、 during stage construction may be more complicated than it is with instantaneous loading. The period for primary consolidation at a definite final load with stage construction may be increased significantly , in sp</p

16、><p>　　Problems related to the settlement analysis of stage construction for embankments on soft clays are of the following types:</p><p>　　(1) Prediction of the deformation behavior of stage const

17、ruction from the results of borings and tests .</p><p>　　(2) Prediction of the final settlement at permanent load from the behavior of the first stage construction.</p><p>　　(3) Prediction of th

18、e post construction settlement at the permanent load and corresponding time of surcharge removed from the behavior of the surcharge.</p><p>　　The first of these problems is heavily dependent on the theory ,

19、which is necessary in design. The other two predictions require empirical rather than theoretical methods because they are based on observational data. In any case , the fact that the second and third predictions are der

20、ived from field observations makes them more reliable than the theoretical predictions .</p><p>　　Leroueil et al revealed the effective stress path and analyzed the relationship between vertical settlement a

21、nd lateral displacement during stage construction. Stamatopoulos and Kotzias developed a method to determine the final settlement at permanent load from the behavior of surcharge, but it is based on the elastic theory an

22、d difficult to calculate the rate of the settlement . The hyperbolic method is based on the total load - settlement relationship to predict the final settlement , which is</p><p>　　This paper presented a met

23、hod for the prediction of the final settlement at permanent load from the behavior of the first stage construction based on the Asaoka method.</p><p>　　2. Stage observational method</p><p>　　As

24、aoka proposed an‘observational procedure’to estimate the final settlement and in2situ coefficient of consolidation from the field observational data. This method is becoming increasing popular because of its simplicity a

25、nd effectivity.</p><p>　　The method is based on the fact that one dimensional consolidation settlements S0 , S1 , S2 , … ，Sj at times 0 ，t ，2t ，… ，jt can be expressed as a first order approximation by </p

26、><p>　　which represents a straight line in a Sj vs Sj-1 plot , where is the intercept and is the slope of the line. When the ultimate settlement has been reached : Sj= Sj-1=Sf , therefore ,the ultimate settle

27、ment Sf can be given by</p><p><b>　　and</b></p><p>　　ln= - (both top and bottom drainage) </p><p>　　ln= - (top drainage)

28、 </p><p>　　The constant has been suggested by Magnan and Deroy to be related to the coefficient of consolidation Cv as follows: for horizontal radial drainage only</p><p>　　for vertical dr

29、ainage only</p><p>　　where De , H are the drainage path length respectively.</p><p>　　Asaoka method also stated that the straight line in Sj- Sj-1 space would moved up in the case of multi-stage

30、d loading , moreover , the shifted lines become almost parallel to the initial when the settlement is relatively small compared to the thickness of clay layer. However , it is not discussed and provided how to determine

31、the shift distance from the line of first stage to the line of the next stage.</p><p>　　In the expression (1) ,when j = 0 that is : t = 0 and S(t=0) = S0 ,where t can be taken as 0 from any time after loadin

32、g works . If t is set as 0 at the exact time once the load is exerted , then , Sj-1 becomes 0。 </p><p>　　This means that Asaoka method can be extended to obtain the c

33、onstruction settlement , which equals to the intercept of the liner line in the space Sj- Sj-1, where t = 0 is set just after loading. Moreover , this immediate settlement contributes the shift distance of the parallel

34、lines during stage construction.</p><p>　　In fact , from the derivation of the Asaoka method , the settlement of soil layers can be expressed as</p><p><b>　　and</b></p><p&

35、gt;　　where T and F are two unknown function of time.</p><p>　　With the vertical drainage boundary conditions and at the ground surface , =T=(t , z=0) . If t = 0 , =(t=0 , z=0) == initial elastic strain. The

36、refore , S(t=0)=S0 gives the immediate settlement Se , which can also be estimated from the elastic method by the equation :</p><p>　　It is clearly shown that the Asaoka method has been extended to predict t

37、he settlement of embankments with stage construction. In other words , the behavior of next stage construction can be predicted with the , from the last stage construction. The more the previous stages with settlement me

38、asurement , the higher the accuracy of next stage prediction. The stage observational method includes following steps :</p><p>　　(1) Sketch observed time settlement curve .</p><p>　　(2) Choose a

39、 time intervalt , which usually ranges from 10 to 100 days , read the settlements Sj from the curve at times t j ( = t j , j = 1 ,2 ,3, …).</p><p>　　(3) Plot the settlements Sj , Sj-1 in a coordinate system

40、with axis Sj , Sj-1 originated from 0.</p><p>　　(4) Fit the plotted points by a straight line , of which corresponding slope is read as . The intercept at the Sj axis gives , while the point of intersection

41、with the 45o line , gives the final consolidation settlement of the first stage.</p><p>　　(5) From the of the first stage construction to determine the undrained modulus Eu by inverse analysis (10) .</p&g

42、t;<p>　　(6) Determine the next stage construction settlement with the above known Eu (10) , thus resulting in the shift distance of line.</p><p>　　(7) Assume the CV remains constant during stage const

43、ruction and settlement is small compared with the thickness of soft soils , this makes the line of next stage construction parallel to the first stage with the slope.</p><p>　　(8) Predicting the final settle

44、ment of next stage construction from the intersection of the shifted line with the 45o line.</p><p>　　(9) Estimate the Ch and CV from the value of with the equation (5) or (6) .</p><p>　　3. Cas

45、e study</p><p>　　3. 1 　Site and project description</p><p>　　Section A of Lianxu highway is a 31 km long high standard expressway connecting the port city Lianyugang to the national highway syst

46、em of China. It was began to construction from Dec. 1999. There are 104 bridges or culverts or passways in this 31 km long section designed to connect embankments . The bottom width of the embankment is 40 m , while the

47、height of embankment changes from 3 to 7 m.</p><p>　　Based on the design code , the differential settlements between embankments and structures have to be controlled less than 10 cm. Post construction settle

48、ments of embankments have to be less than 30 cm during the post construction period of 15 years . It is clear that the magnitude and rates of the embankment settlements are the extremely important problem to make the pro

49、ject reliable and economical .</p><p>　　3. 2 　Subsurface conditions</p><p>　　The section A of Lianxu highway passes over the marine deposit plain. The typical subsoil profile consists of 0 to 3m

50、 think upper crust of stiff clay underlain by a 5.6 to 13m thick soft clay ,which is named Jiangsu Marine clay. Blow this soft clay , lies alternating layers of stiff clay and dense sand extending to badrock with the var

51、ied thickness of 10 to 20m. </p><p>　　3. 3 　Soil improvement and embankment construction</p><p>　　Dry Jet Mixing and stage construction with sand blanket have been designed to reduce the total s

52、ettlement and post construction settlement . The embankment filled with residual clay from Dec. 1999. After the first stage construction of 2.5～3.5 m high , about 6 months were left along for soil consolidation. The sett

53、lements are observed regularly by settlement plates . During the period of the first stage consolidation , some observational settlements are found to be larger than the corresponding </p><p>　　3. 4 　Predict

54、ion of the final settlement</p><p>　　The typical fill heights with time and measured ground surface settlements at the center of embankments with sand blankets are shown. It can be seen that the settlement c

55、urve drops significantly between the first stage and second stage construction. The final settlements of the second stage construction are predicted from the first stage observational data by the stage observational meth

56、od. It indicates that the predicted settlements are basically consistent with the measured settlement . Table </p><p>　　4. Conclusions</p><p>　　On the basis of theoretical derivation of Asaoka

57、method and case study of Jiangsu Marine clay , this paper presented a Stage Observational Method for settlement prediction of embankments on soft ground with stage construction. The following conclusions can be given:<

58、;/p><p>　　(1) Considering the available observational methods for ultimate settlement prediction , the Asaoka method may be successfully extended to make the settlement prediction for stage construction embankm

59、ents .</p><p>　　(2) The immediate settlement Se is verified to be equal to the intercept in the Sj and Sj-1 space of the Asaoka method , therefore , the undrained modulus of soft ground can be obtained from

60、the first stage construction measurements , this contributing to the more accurate estimation of immediate settlement of the next stage construction.</p><p>　　(3) Assuming the actual coefficient of consolida

61、tion and the thickness of the soft ground remain constant during stage construction , the shifting distances of the parallel lines with the slope of is equaled to the immediate settlements , which can be calculated with

62、the inverse modulus from the first (last) stage construction.</p><p>　　(4) The distinct advantage of the recommended method is that the values of undrained modulus and coefficient of consolidation for next s

63、tage construction are inversely analyzed from the first (last) stage construction.</p><p>　　(5) From the case study , the value of Eu / cu ratio ranges from 50 to 100 for Jiangsu Marine clay , while the actu

64、al coefficient of consolidation is almost one order of magnitude larger than the laboratory data.</p><p>　　Acknowledgement</p><p>　　The research is sponsored by Doctoral Program Funds of Educati

65、on Ministry of China. The support is grateful acknowledged.</p><p>　　軟土地基上分期施工的路堤沉降預(yù)測方法</p><p>　　摘要：沉降量和沉降速率控制是軟土地基上路堤工程設(shè)計(jì)的關(guān)鍵問題，由于固結(jié)理論的局限性和參數(shù)的不確定性，理論預(yù)測的精度較低，而基于現(xiàn)場實(shí)測數(shù)據(jù)的觀測法則顯示出了較高的精度。本文在Asaoka觀測法的

66、基礎(chǔ)上,形成了一種軟土路基上分期施工時(shí)路堤沉降預(yù)測的方法，結(jié)合江蘇海相軟土上的高速公路工程進(jìn)行了沉降預(yù)測分析。</p><p>　　關(guān)鍵詞：沉降, 路堤, 觀測法, 分期施工</p><p><b>　　1. 簡介</b></p><p>　　對(duì)于軟土地基上的路堤設(shè)計(jì)來說，沉降和穩(wěn)定性是需要考慮的兩個(gè)關(guān)鍵性因素?，F(xiàn)有的評(píng)估路堤穩(wěn)定性的方法基本

67、上能滿足設(shè)計(jì)要求。因此，沉降便成了設(shè)計(jì)分析路堤長久性的關(guān)鍵參數(shù)。換句話說，對(duì)沉降的分析是路堤分析的最合適的方法。</p><p>　　軟土地基上路堤的沉降主要是由于路堤的固結(jié)和側(cè)向流動(dòng)所引起的。對(duì)于軟土地基上的路堤，人們做了很多這方面的研究。</p><p>　　很多實(shí)驗(yàn)已經(jīng)得出了對(duì)于預(yù)估沉降量和沉降率的實(shí)際值的理論，同時(shí)，實(shí)驗(yàn)也解釋了一些涉及精確預(yù)估沉降量的問題。Duncan于1993年

68、、Olson于1998年分別對(duì)預(yù)估沉降量在現(xiàn)有條件下所引起缺陷的不確定性因素進(jìn)行了分析。這些不確定性因素使得估算路堤沉降量和沉降速率有時(shí)特別困難甚至是無法進(jìn)行估算。盡管數(shù)值分析法能提高計(jì)算的精確性，但是土的本構(gòu)模型涉及到很多不能被確定的參數(shù)。然而，隨著數(shù)值分析法的計(jì)算化，這使得我們可以獲得更多的土的本構(gòu)模型和相應(yīng)的程序代碼，從而使計(jì)算得以簡化得以更精確。</p><p>　　因此，人們非?？释l(fā)展這樣一種觀測方法

69、——只要記錄足夠的沉降參數(shù)，通過計(jì)算機(jī)就能得到精確的沉降值。很多研究人員在現(xiàn)場觀測的基礎(chǔ)上發(fā)展了沉降預(yù)估法。該方法不僅能夠得到精確解，還被認(rèn)可為估算最終沉降量和沉降速率的方法。</p><p>　　分期施工對(duì)于軟土地基上的路堤來說是一個(gè)特殊的程序。隨著每一個(gè)施工期路堤的固結(jié)，路堤的安全性會(huì)逐漸提高，竣工后的沉降量也會(huì)減少。施工時(shí)期的沉降—時(shí)間（s-t）曲線可能會(huì)比瞬時(shí)荷載的曲線更為復(fù)雜。盡管竣工后的沉降量會(huì)減少，

70、但是施工時(shí)期路堤在穩(wěn)定的最終荷載作用下的初始的固結(jié)期會(huì)明顯增加。為了加快沉降速率，減小軟土層的竣工后的二次沉降，實(shí)際中我們經(jīng)常采用超載，也就是在竣工時(shí)期加臨時(shí)荷載，然后卸載。</p><p>　　對(duì)于軟土層上路堤的施工期的沉降分析的問題有如下幾種：</p><p>　　(1)預(yù)估施工時(shí)期由于鉆孔測試而引起的變形。</p><p>　　(2)預(yù)估在永久荷載作用下由于第

71、一施工期所引起的最終沉降。</p><p>　　(3)預(yù)估在永久荷載和相應(yīng)的超載下由于超載所引起的竣工后的沉降。</p><p>　　第一個(gè)問題主要依賴于設(shè)計(jì)時(shí)的理論。其余兩個(gè)問題需要以經(jīng)驗(yàn)為根據(jù)而不是靠理論方法。因?yàn)樗鼈兪强坑^測的數(shù)據(jù)而得來的。在任何情況下，第二個(gè)和第三個(gè)從現(xiàn)場觀測到的預(yù)估沉降量比理論算得的沉降量都可靠。</p><p>　　Leroueil et

72、 al提出了有效應(yīng)力路徑，分析了施工時(shí)期豎向沉降和橫向沉降之間的關(guān)系。Stamatopoulos和Kotzias發(fā)展了在永久荷載下確定最終沉降的方法，但這種方法是基于彈性理論的，而且它很難用來計(jì)算沉降率。而雙曲線模型的方法又是依據(jù)總的荷載—沉降關(guān)系來預(yù)估最終沉降量，這種方法對(duì)于在初始天然荷載下的沉降很不靈敏。</p><p>　　本文在Asaoka觀測法的基礎(chǔ)上，提出了一種軟土地基上分期施工時(shí)在永久荷載作用下的預(yù)

73、估最終沉降的方法。</p><p><b>　　2. 分期觀測法</b></p><p>　　Asaoka建議采取一個(gè)“觀測過程”，利用現(xiàn)場觀測的數(shù)據(jù)來估算最終沉降量和原位固結(jié)系數(shù)。這種方法因?yàn)槠浜唵涡院陀行远兊迷絹碓绞軞g迎。</p><p>　　該方法是基于單向固結(jié)沉降量S0 , S1 , S2 , …… ，Sj在時(shí)間0 ，t ，2t

74、，…… ，jt時(shí)能被作為第一近似值，公式如下：</p><p>　　Sj =+Sj-1 (2-1)</p><p>　　在時(shí)間Sj- Sj-1圖里它代表了一條直線。這里是直線的截距，是直線的傾角。當(dāng)達(dá)到最終沉降時(shí)：Sj= Sj-1=Sf ，因此，最終沉降Sf可以由如下公式求得：</p>&l

75、t;p>　　Sf = (2-2)</p><p>　　ln= - （兩面排水時(shí)） (2-3)</p><p>　　ln= - （頂部排水時(shí)） (2-4)</p><p&g

76、t;　　常數(shù)和固結(jié)系數(shù)CV有關(guān)：Magnan和Deroy認(rèn)為</p><p><b>　　對(duì)于橫向排水： </b></p><p>　　Ch = (2-5)</p><p><b>　　對(duì)于豎向排水： </b></p><

77、p>　　Cv = (2-6)</p><p>　　這里De ，H分別是排水路徑的長度。</p><p>　　Asaoka觀測法也表明，Sj- Sj-1圖中的直線在多級(jí)荷載作用下會(huì)改變位置，而且，當(dāng)沉降相對(duì)較小而粘土層相對(duì)較厚時(shí)，移動(dòng)的直線基本上和初始直線是平行的。但是，該方法并沒有討論給出如何確定從一個(gè)

78、直線段到下一個(gè)直線段的移動(dòng)距離。</p><p>　　在表達(dá)式(1)中，當(dāng)j = 0時(shí)，t = 0，S(t=0) = S0 ,這里t是荷載的工作時(shí)間。如果在荷載卸載的瞬間將t設(shè)置為0，那么Sj-1就變?yōu)?。因此</p><p>　　S0 = =瞬時(shí)沉降Se (2-7)</p><p>　　這就意味著As

79、aoka觀測法能被擴(kuò)展為求固結(jié)沉降，其值等于Sj- Sj-1圖里的 直線的截距，這里t = 0是在荷載加上之后。此外，這種瞬時(shí)沉降也是分期施工期平行線的移動(dòng)距離。</p><p>　　事實(shí)上，根據(jù)Asaoka觀測法的最初土層的沉降值能由下式求得：</p><p>　　St = (2-8)</p>&l

80、t;p><b>　　(2-9)</b></p><p>　　這里T和F是兩個(gè)未知的時(shí)間系數(shù)。</p><p>　　在豎向排水的底部和土層的頂部，=T=(t , z=0) 。如果t = 0，那么=(t=0 , z=0) ==初始彈性應(yīng)變。因此，S(t=0)=S0就能得到瞬時(shí)沉降Se 。Se也能由如下彈性原理的公式求解：</p><p>　　

81、S0=Se= (2-10)</p><p>　　上式清楚地表明Asaoka觀測法能夠被擴(kuò)展到估算施工期路堤的沉降。也就是說，下一個(gè)施工期的路堤的狀況可由上一個(gè)施工期的，進(jìn)行估算。上一個(gè)施工期的路堤的沉降測量值越多，下一個(gè)施工期的估算值就越精確。分期觀測法包括以下幾個(gè)步驟： </p><p>　　(1)觀察時(shí)間—沉降曲線的

82、草圖</p><p>　　(2)選擇時(shí)間間隔t，通常是10到100天之間。在tj 時(shí)刻讀取曲線上的沉降Sj 。</p><p>　　(3)在相應(yīng)的坐標(biāo)系里以Sj- Sj-1為軸，從0開始標(biāo)出沉降Sj- Sj-1的點(diǎn)。</p><p>　　(4)用直線將標(biāo)出的點(diǎn)連起來，直線相應(yīng)的傾角是，在Sj軸上的截距為，與45o直線的交點(diǎn)是第一工期的最后固結(jié)沉降量。</p&g

83、t;<p>　　(5)利用第一工期的通過(2-10)式反求不排水壓縮模量。</p><p>　　(6)通過已知的Eu來確定下一工期的路堤沉降，從而確定直線段的移動(dòng)距離。</p><p>　　(7)假設(shè)CV在分期施工時(shí)是連續(xù)的，并且假設(shè)相對(duì)于軟土的厚度來說路堤沉降非常小，這可以保證下一工期的直線段平行于第一施工期的直線段。</p><p>　　(8)從與

84、45o斜線的交點(diǎn)預(yù)估下一施工期的最后沉降量。</p><p>　　(9)利用的值通過式(2-5)、(2-6)分別估算Ch和CV 。</p><p><b>　　3. 實(shí)例研究</b></p><p>　　3.1 工程地址和工程概述</p><p>　　連云港—徐州高速公路的A段是一段長31km的高速公路，它把港口城市

85、連云港和國家高速公路網(wǎng)連在一起。該工程于1999年12月開始動(dòng)工。這其中包括104座橋和涵洞。該高速公路路堤的底部寬40m，高從3m到7m不等。</p><p>　　根據(jù)設(shè)計(jì)標(biāo)準(zhǔn)，路堤和結(jié)構(gòu)的沉降值必須控制在10cm以內(nèi)?？⒐ず蟮穆返坛两翟诮ǔ珊蟮?5年里必須小于30cm。很明顯，路堤的沉降量和沉降速率對(duì)工程的可靠性和經(jīng)濟(jì)性是至關(guān)重要的。</p><p>　　3.2 地面下的土質(zhì)條件&l

86、t;/p><p>　　連徐高速公路的A段要經(jīng)過海相沉積平原。該平原的地基土剖面圖包括0到3m厚的上層硬表層的硬粘土，其下是5.6m到13m厚的軟粘土，別名江蘇海相軟土。軟粘土下是交替間隔的硬粘土和稠粘土，厚度從10m到20m，它們一直延伸到基巖。</p><p>　　3.3 土層的改良和路堤的施工</p><p>　　我們設(shè)計(jì)采用干射攪拌法和砂墊層分期施工法來減少總的

87、沉降和竣工后的沉降。從1999年12月開始，路堤用殘積粘土填充，在第一期施工到2.5—3.5m高后，讓土自然固結(jié)6個(gè)月。固結(jié)沉降期間通過沉降板定期觀測路堤的沉降，這一期間，一些觀測到的沉降比相應(yīng)的設(shè)計(jì)總沉降還大。為了修改原先的設(shè)計(jì)，使得下一施工期的方案更可靠，我們有必要再次預(yù)估基于第一施工期沉降觀測結(jié)果的路堤的性狀。</p><p>　　3.4 預(yù)估最終沉降</p><p>　　從路堤填

88、充高度和對(duì)路堤中心處砂墊層的地表沉降測試結(jié)果中，我們發(fā)現(xiàn)第一期和第二期的沉降曲線下降非常陡。第二施工期后的最后沉降可以由分期觀測法通過第一期的觀測數(shù)據(jù)來預(yù)測。這表明預(yù)估沉降量和測試沉降量基本上是相符的。曲線同時(shí)也表明基于第一期觀測數(shù)據(jù)的不排水彈性模量Eu和CV的有效性。Eu/cu的比率為50—100，而CV（現(xiàn)場）/CV（室內(nèi)）的比率為6—12。這也似乎表明江蘇海相粘土Eu/cu在低范圍內(nèi)的比率符合。Bangkok粘土和其它已經(jīng)存在的粘

89、土的比率為70—253（也就是計(jì)算數(shù)據(jù)是有效的），而實(shí)際的固結(jié)系數(shù)值大于試驗(yàn)測得的值，這會(huì)導(dǎo)致更快速率的沉降。</p><p><b>　　4. 結(jié)論</b></p><p>　　基于Asaoka觀測法的理論來源，結(jié)合對(duì)江蘇海相粘土的研究，本文發(fā)展了一種軟土路基上分期施工時(shí)路堤沉降預(yù)測的方法。結(jié)論如下：</p><p>　　(1)對(duì)比所有的最

90、終沉降預(yù)測的觀測方法，Asaoka觀測法能夠成功地?cái)U(kuò)展到預(yù)測分期施工路堤的沉降。</p><p>　　(2)在根據(jù)Asaoka觀測法繪制的Sj-和Sj-1圖中，瞬時(shí)沉降Se被證明是等于截距的。因此，在第一期觀測中，我們能夠得到軟土層的不排水壓縮模量。它有助于我們更精確地估算下一期的瞬時(shí)沉降。</p><p>　　(3)假定實(shí)際的固結(jié)系數(shù)和土層厚度在分期施工期仍然保持連續(xù)，傾角的平行線段的移