大壩設(shè)計(jì)外文翻譯---從非飽和土力學(xué)的角度，土石壩材料的特性

1、<p><b>　　附錄2</b></p><p>　　ESEARCH ARTICLE</p><p>　　Eduardo E. ALONSO, Rafaela CARDOSO</p><p>　　Behavior of materials for earth and rockfill dams:</p><p&g

2、t;　　Perspective from unsaturated soil mechanics</p><p>　　© Higher Education Press and Springer-Verlag Berlin Heidelberg 2010</p><p>　　Abstract ：The basis of the design of earth and rockfil

3、l dams is focused on ensuring the stability of the structure under a set of conditions expected to occur during its life. Combined mechanical and hydraulic conditions must be considered since pore pressures develop durin

4、g construction, after impoundment and in drawdown. Other instability phenomena caused by transient flow and internal erosion must be considered. The prediction of the hydromechanical behavior of traditional and non-trad

5、ition</p><p>　　Keywords ： ams, unsaturated soil mechanics, suction, rockfill, clayey soil, mixture</p><p>　　1 Introduction</p><p>　　The basis of the design of earth and rockfill dam

6、s is focused on ensuring the stability of the structure under a set of conditions expected to occur during its life. The stability of the upstream and downstream slopes must be guaranteed at the end of the construction b

7、ut also during reservoir impoundment and the operational phase, including drawdown and long-term steady state conditions as a limiting case. A fundamental aspect of the analysis is the generation of pore pressures during

8、 the constr</p><p>　　Failures associated with hydraulic fracture and internal erosion is largely reported in the literature. Two recent cases of failure caused by collapse and internal erosion are presented

9、in the first part of the paper. The hydromechanical behavior of the materials used in the construction of the earth structures are used to explain their failure. </p><p>　　An additional source of complexity

10、is the fact that different types of materials are used. For traditional dams, impervious clayey materials are used for the core, rockfill materials (any type of rock) are used for shells and granular materials are used f

11、or filters. However, for sustainability constraints and environmental reasons, the use of marginal materials, i.e., materials that traditionally would not be used in the construction of dams, is becoming frequent. Such i

12、s the case of soft rocks </p><p>　　Figure 1 is a photograph of Lechago Dam in Teruel, Spain. A very traditional design was adopted. Three distinct zones can be distinguished: the core, built with regular com

13、pacted soils (low to medium plasticity sandy clays, clayey sands and clays), the shoulders built with indurated shale rockfill and the filter built with fine granular materials. Other solutions are also adopted in the de

14、sign as a consequence of the available material for the construction. For example, rockfill materials can be</p><p>　　Compacted soft rocks are also used in the construction of dams and Albagés Dam, Llei

15、da (Spain) is an example (Figure 3 shows an experimental embankment being built during the design of this dam). Compacted soft rocks (fragments of evolving rocks such as schist, marls and other clayey rocks) are differen

16、t from rockfill (fragments of hard rock) because of the geological nature of the rocks used. After compaction and hydration, the large fragments of soft rock degrade and result in a material inter</p><p>　　M

17、ixtures of rock and fine materials are other alternative materials. The characterization of their hydraulic and mechanical properties is usually complex because it depends on the nature of the materials, the proportions

18、used and many other factors. Figure 4 is a photograph of the material used to build Villaveta Dam in Navarra, Spain (a natural mixture of gravels with clayey soil).</p><p>　　Each type of material has a uniqu

19、e behavior and its own particularities should be considered in dam design.Experience earned in the past decades is being used in design when traditional materials are adopted. Because it is no longer feasible to select “

20、the best” emplacement or to import “good” materials, virtually any kind of soil or rock is expected to be used in the design of dams. Moreover, as new projects are being commissioned in Africa, South America and Asia, lo

21、cal soils and rocks outcrop</p><p>　　2 Two failures</p><p>　　Two cases are presented where collapse deformations were followed by internal erosion. The first case concerns an uncontrolled and d

22、angerous leak and the second the rupture of a dam caused by localized collapse during impoundment. </p><p>　　2.1 Differential collapse of foundation during the first filling</p><p>　　The La Mol

23、ina pond was built for water storage in the Catalonian Pyrenees. As shown in the plan view in Fig. 5, a 15m high rockfill dam covered by an impervious membrane was built taking advantage of the topographic conditions. A

24、pipe system (see Fig. 5) was included for drainage under the membrane. It was buried in a gravel and sand fill layer. No special attention was taken in the compaction of this fill layer, which was done probably dry of op

25、timum. </p><p>　　A few sinkholes were observed after full impoundment. Water whirlpools marked their position directly above drainage pipes (see sketch in Fig. 5). There were attempts to plug the holes by me

26、ans of cement bags thrown from helicopters. The desperate procedure was partly successful but it was eventually decided to empty the pond. </p><p>　　Tunnel-shaped depressions were discovered at the whirlpool

27、 positions. The membrane was ruptured in those points. The granular base was excavated and the pipe drains were uncovered (see Fig. 6). They were found broken and filled, in relatively long distances, with a granular mat

28、erial. High speed water was capable of dragging the gravels inside the filter pipes. </p><p>　　A possible explanation for the failure is described as follows (see Fig. 7): Hydrostatic loading after impoundme

29、nt caused probably some initial differential settlements of the gravel and sand fill, poorly compacted. However, it is believed that the progressive saturation of this granular layer, under the total stresses transmitted

30、 by the water level in the pond, led to a soil collapse, which was nonhomogeneous. Then the differential collapse led to the breakage of the pipes at some points. Sand </p><p>　　This case was not developed f

31、urther but it illustrates the need to ensure good compaction conditions of all the materials. They must be adequate to minimize the penalizing effects of their expected behavior in case of being fully</p><p>

32、;　　saturated either in service conditions or by accident.</p><p>　　2.2 Fill collapse during impoundment</p><p>　　An artificial pond was created in an arid environment by building a homogeneous d

33、am covered upstream by an impervious HDPE membrane. The construction took advantage of the ground topography so that the dam was necessary only in part of the pond perimeter, as shown in Fig. 8. The dam was built having

34、a maximum height of 20 m at the location of the creek, but progressively decreased in height in the rest of the dyke perimeter. Figure 8 shows a sketch of the small watershed area drained by a small</p><p>

35、　　Low plasticity sandy clays and high plasticity clays were compacted within short distances within the embankment. There are also indications that the achieved field densities were lower than the optimum Normal Proctor

36、values. Wetting under load tests performed on some specimens indicated a high collapse potential. In two tests performed, collapse deformations reached values of 3.8% (for a vertical load of 85 kPa) and 8.3% (for a verti

37、cal load of 245 kPa). These two vertical loads are well within</p><p>　　On first impoundment, when the water level reached 15m over the foundation, a section of the dam, located directly above the position o

38、f the creek, failed, causing a violent flood. Figures 10 and 11 show the failed section. The development of the failure was not observed. When the photographs in Figs. 10 and 11 were taken, the reservoir was practically

39、empty. </p><p>　　Field observations (see Fig. 12) indicated that the fill could have a significant collapse potential and, probably, a susceptibility to internal erosion. Troughs and sinkholes were observed

40、in the downstream slope of the dam a few years after the collapse. The compacted soils (they are observed in the background of Fig. 12, where the almost vertical slope of the failed section remained stable a few years af

41、ter the dam failure) were rather heterogeneous.</p><p>　　It is acceptable to assume that any rain water falling into the pond area during construction was eventually drained out through the creek bed. This s

42、ituation could only change in the final stage of the works, when the HDPE membrane covered the pond and the upstream slopes of the dam. </p><p>　　A possible explanation for the failure is described as follow

43、s:</p><p>　　Insufficient compaction of the fill, probably dry of optimum, builds a collapse potential into the fill. This collapse potential develops when a given point within the fill experiences an increas

44、e in confining stress over the initial yield stress induced by compaction. The collapse strains will develop if the water content increases. </p><p>　　The fill located immediately above the creek holds the m

45、ost critical situation:</p><p>　　here, the dam reaches the maximum height and the seeping waters through the creek bed could easily lead to a capillary rise affecting a certain thickness above the original g

46、round level. Therefore, the fill volume having the highest collapse potential is viewed as an elongated mass of compacted soil lying directly above the creek. A collapse of this volume will tend to create voids and crack

47、s, which could lead to a preferential path connecting the upstream and downstream slopes of the dam.</p><p><b>　　譯文</b></p><p>　　愛(ài)德華五，阿隆索拉斐拉卡多佐</p><p>　　從非飽和土力學(xué)的角度，土石壩材料

48、的特性</p><p>　　©高等教育出版社與施普林格出版社2010年柏林海德堡</p><p>　　摘要 土石壩設(shè)計(jì)依據(jù)的重點(diǎn)是，在其生命中可能出現(xiàn)各種條件下的確保結(jié)構(gòu)穩(wěn)定。結(jié)合機(jī)械和水力條件，必須考慮孔隙壓力的發(fā)展，因?yàn)榭障秹毫υ谑┕て陂g發(fā)展，蓄水后下跌。另外，瞬變流和內(nèi)部侵蝕造成的不穩(wěn)定現(xiàn)象也必須加以考慮。因此作者在大壩建設(shè)中使用的傳統(tǒng)和非傳統(tǒng)材料的流體力學(xué)特性的預(yù)測(cè)成為

49、根本。大壩的建設(shè)中使用的材料涵蓋了從多種粘土材料到堆石。 從廣義上講，它們是碾壓材料，所以是不飽和材料。作者在文件中，依據(jù)大壩建設(shè)采用傳統(tǒng)的材料特性，對(duì)現(xiàn)有的知識(shí)水平進(jìn)行總結(jié)。常規(guī)碾壓材料（具有重大粘土含量），堆石和壓實(shí)軟巖研究更多細(xì)節(jié)。后者是非傳統(tǒng)材料。他們分析，因?yàn)樗鼈兊氖褂?，以及土壤和巖石混合使用，是可持續(xù)發(fā)展的所必須的。</p><p>　　關(guān)鍵詞 壩，非飽和土力學(xué)，吸力，堆石，粘質(zhì)土，混合物</

50、p><p><b>　　1簡(jiǎn)介</b></p><p>　　土石壩設(shè)計(jì)的基礎(chǔ)，重點(diǎn)確保發(fā)生在其預(yù)期生命中各種條件下的結(jié)構(gòu)穩(wěn)定性。不但在施工結(jié)束階段而且在水庫(kù)蓄水和運(yùn)行階段，上游和下游邊坡的穩(wěn)定性必須保證，包括下跌和長(zhǎng)期穩(wěn)定的狀態(tài)作為一個(gè)限制條件?；痉矫娴姆治鍪强紫秹毫υ谑┕?，并在初次蓄水，水庫(kù)蓄水及水位驟降的情況下產(chǎn)生。其他方面也是令人關(guān)注的，如在施工和運(yùn)行階段的結(jié)構(gòu)變

51、形，并通過(guò)水力壓裂，內(nèi)部侵蝕，長(zhǎng)期影響和其他作用聯(lián)合引起的事故。</p><p>　　與水力侵蝕和內(nèi)部侵蝕的相關(guān)的失事主要是文獻(xiàn)報(bào)道。最近兩次倒塌和內(nèi)部侵蝕造成的失事，在該文件的第一部分提出。土石壩結(jié)構(gòu)的建筑材料流體力學(xué)特性來(lái)解釋它們的失事。</p><p>　　另外一個(gè)復(fù)雜的原因是不同材料的使用。對(duì)于傳統(tǒng)的壩，粘土防滲材料的用作心墻，堆石材料（任何巖型）用于殼狀物和粒狀物料的過(guò)濾層使用。

52、然而，由于可持續(xù)發(fā)展制約因素和環(huán)境的原因，邊際使用材料，即傳統(tǒng)上不會(huì)在大壩建設(shè)使用的材料，已經(jīng)變得越來(lái)越頻繁使用。這就是一部分軟巖或演變的巖石和土壤或巖石蒸發(fā)的比例情況。</p><p>　　圖1是Lechago大壩在特魯埃爾，西班牙的照片。一個(gè)非常傳統(tǒng)的設(shè)計(jì)獲得通過(guò)。三個(gè)不同的區(qū)域可以有所區(qū)別：心墻，常規(guī)（低到中等塑性粘土砂，粘土砂和黏土）夯實(shí)土壤建成，建成與壩肩硬化頁(yè)巖面板和細(xì)顆粒材料建成的過(guò)濾層。其它解決方

53、案還通過(guò)了作為建筑用材料的設(shè)計(jì)結(jié)果。例如，堆材料可用于不透水材料解決方案，以及于壓軟巖相結(jié)合。圖2顯示了卡拉科萊斯大壩在圣胡安，阿根廷，聯(lián)合解決方案，采用堆，沖積礫石，礫石和砂作出的，和上游混凝土防滲墻.</p><p>　　夯實(shí)軟巖也用于壩和阿爾瓦赫斯大壩，萊里達(dá)建設(shè)（西班牙）就是一個(gè)例子（圖3顯示了一個(gè)正在建造的試驗(yàn)堤在此壩設(shè)計(jì)）。夯實(shí)軟巖（如不斷發(fā)展的巖石碎片片巖，如泥灰?guī)r和，其他粘土巖）與堆石（堅(jiān)硬的巖石

54、碎片）不同，因?yàn)閹r石地質(zhì)性質(zhì)。經(jīng)過(guò)壓實(shí)和水化，軟巖大片段降解的材料造成土壤和巖石之間的中間，相對(duì)不透水，但比傳統(tǒng)堆石，有更可壓縮和更敏感干濕周期。</p><p>　　巖石混合物和細(xì)顆粒材料是其他替代材料。其液壓和機(jī)械性能表征通常是復(fù)雜的，因?yàn)樗蓪?duì)材料的性質(zhì)，使用的比例和許多其他因素而定的。圖4是一個(gè)建立納瓦拉，西班牙Villaveta大壩材料照片（一粘性土和礫石自然的混合物）。</p><

55、p>　　每類材料具有獨(dú)特的特性和自己的特殊性，應(yīng)在大壩設(shè)計(jì)中考慮。當(dāng)使用傳統(tǒng)材料時(shí)，用過(guò)去數(shù)十年獲得的經(jīng)驗(yàn)設(shè)計(jì)。因?yàn)樗辉偈强尚械倪x擇“最好的”安置或?qū)搿傲己谩钡牟牧?，幾乎任何類型的土壤或巖石，預(yù)計(jì)將在大壩設(shè)計(jì)中的應(yīng)用。此外，由于新項(xiàng)目正委托在非洲，南美和亞洲，當(dāng)?shù)責(zé)釒Ш突鹕降貐^(qū)出露的土壤和巖石必須使用。這些是在北半球溫帶氣候地層發(fā)現(xiàn)沖積和沉積土壤和常規(guī)的土壤的理解是不同的。對(duì)土壤工程師來(lái)說(shuō)，非傳統(tǒng)材料的使用是一個(gè)重要的挑戰(zhàn)。非

56、飽和土力學(xué)理論的發(fā)展在很大程度上程度，提供理論和壓實(shí)土的特性，專門(mén)的測(cè)試和計(jì)算工具，它可以改善土石壩工程藝術(shù)的現(xiàn)況模型。</p><p><b>　　2 兩次失事</b></p><p>　　兩起案件的塌陷變形情況發(fā)生在內(nèi)部侵蝕之后。第一個(gè)案件涉及失控和危險(xiǎn)的泄漏，第二個(gè)是由局部坍塌造成大壩蓄水期間破裂。</p><p>　　2.1 發(fā)生在初

57、次蓄水不同基礎(chǔ)的坍塌 </p><p>　　在莫利納建池的水儲(chǔ)存在加泰羅尼亞比利牛斯山脈。正如圖5中所示的計(jì)劃的看法。一個(gè)15米高的墻堆石壩防滲膜覆蓋利用地形條件的優(yōu)勢(shì)建造。管道系統(tǒng)（見(jiàn)圖5）包括在膜下排水。這是埋在碎石和沙子填充層。不用特別注意在這個(gè)填充層的壓縮，這樣做是可能的最佳壓實(shí)度。</p><p>　　少數(shù)灰?guī)r坑進(jìn)行全面蓄水后被發(fā)現(xiàn)。水漩渦標(biāo)志著其正上方排水管位置（參見(jiàn)圖草圖5）

58、。有人試圖從直升飛機(jī)投擲水泥袋堵塞這些孔。這是一個(gè)絕望的過(guò)程，只有部分是成功的，但最終決定清空水池。</p><p>　　在漩渦點(diǎn)發(fā)現(xiàn)了隧道狀凹陷。在這些漩渦點(diǎn)，該膜破裂。粒狀地基開(kāi)挖和管道顯露出來(lái)（見(jiàn)圖6）。在相當(dāng)長(zhǎng)的距離內(nèi)發(fā)現(xiàn)顆粒材料填補(bǔ)和破碎。高速水有拖過(guò)濾管道內(nèi)的礫石的能力。</p><p>　　對(duì)失事的描述一種可能的解釋如下（見(jiàn)圖7）：蓄水后靜負(fù)荷可能引起的一些碎石和沙子填充，壓

59、實(shí)初步產(chǎn)生不均勻沉降差。然而，人們認(rèn)為這個(gè)顆粒層逐漸飽和下，總應(yīng)力轉(zhuǎn)到池塘的水下，導(dǎo)致了土壤崩潰，這是非齊次。不同倒塌導(dǎo)致水管在一定程度的破裂。砂和礫石進(jìn)入管道產(chǎn)生局部下陷，并最終導(dǎo)致在池塘的頭部下水中的膜破損。一旦膜破裂，該顆粒層局部侵蝕可能擴(kuò)大初始破裂。水已經(jīng)在這些點(diǎn)自由逃脫。</p><p>　　這個(gè)事件沒(méi)有進(jìn)一步發(fā)展的需要，但它說(shuō)明，需要確保所有材料具有壓實(shí)良好條件。他們必須盡量減少他們?cè)诒活A(yù)期的特性的懲

60、罰，以防在不是在服務(wù)條件或意外條件下被完全飽和的影響。</p><p>　　2.2 蓄水期間填充物坍塌</p><p>　　在一個(gè)人造池塘干旱環(huán)境，建設(shè)一個(gè)覆蓋均質(zhì)壩上游防高密度聚乙烯膜防滲。利用地面地形的優(yōu)勢(shì)，使大壩必要在池塘周圍部分，如圖8所示. 大壩建成后在小溪位置，最大高度20米，但在堤壩周圍其他部份高度逐漸下降。圖8顯示了小流域的一個(gè)小溪流排水區(qū)示意圖。圖9顯示了大壩斷面在原有

61、的排水河的位置后來(lái)由池塘面積占用。</p><p>　　低塑性粘土和可塑性高砂質(zhì)粘土在河堤的短距離內(nèi)被壓縮。也有跡象表明，所取得的實(shí)地密度均低于正常普羅克托最佳值。根據(jù)一些濕潤(rùn)標(biāo)本進(jìn)行負(fù)載測(cè)試圖顯示出高潛在倒塌。兩個(gè)測(cè)試，測(cè)試坍塌變形達(dá)到了3.8％（垂直負(fù)載85千帕）和8.3％（245千帕一垂直荷載）.圖9 這兩個(gè)載荷在期望最大垂直應(yīng)力范圍內(nèi)。</p><p>　　在首次蓄水，當(dāng)水位達(dá)到了

62、超過(guò)基礎(chǔ)15米，一個(gè)大壩位于河正上方的位置，易發(fā)生失事，導(dǎo)致洪水泛濫。圖10和11顯示失事的部分。失事的發(fā)展并沒(méi)有觀察到。圖10和圖11的照片被采用，水庫(kù)幾乎空的。</p><p>　　野外觀察（見(jiàn)圖12）表示，填補(bǔ)可能有明顯崩潰的可能，而且很可能是一個(gè)內(nèi)部侵蝕。觀察到在大壩下游槽和灰?guī)r坑坡，數(shù)年后倒塌。土壤的壓實(shí)（他們正在后臺(tái)觀察 圖12，大壩失事幾年后，垂直邊坡的破壞部分仍然保持穩(wěn)定）都相當(dāng)混雜。</p

63、><p>　　這是可以接受的假設(shè)，任何施工期間落進(jìn)池塘的任何雨水最終都通過(guò)河床排出來(lái)。改變這種局面只能在工程最后階段，當(dāng)高密度聚乙烯膜覆蓋的池塘和水庫(kù)上游山坡的最后階段。</p><p>　　對(duì)失事一種可能的解釋的描述如下：</p><p>　　填充材料壓實(shí)不足，可能的最佳的壓實(shí)度，構(gòu)建成一個(gè)潛在倒塌的危險(xiǎn)。這潛在倒塌的開(kāi)始發(fā)展時(shí)，在給定的點(diǎn)在圍填經(jīng)歷過(guò)的限制壓力增加初