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土堤加糙透水式預(yù)制塊護(hù)坡消浪效果模型試驗(yàn)

2017-03-27 00:55李火坤李怡靜徐旺敏劉伍根
關(guān)鍵詞:光面六邊形凹槽

李火坤,杜 磊,李怡靜,徐旺敏,劉伍根

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土堤加糙透水式預(yù)制塊護(hù)坡消浪效果模型試驗(yàn)

李火坤1,杜 磊1,李怡靜1※,徐旺敏2,劉伍根2

(1.南昌大學(xué)建筑工程學(xué)院,南昌 330031; 2.上饒市水利科學(xué)研究所,上饒 334000)

波浪爬高是確定土堤堤頂高程的重要參數(shù)之一,土堤坡面護(hù)坡的消浪效果將直接影響波浪的爬高,在土堤護(hù)坡工程中,光面混凝土預(yù)制塊護(hù)坡應(yīng)用最為廣泛,但其消浪效果較差,為了解決這一的問題,該文以鄱陽湖上饒片區(qū)堤防工程為例,通過增加護(hù)坡預(yù)制塊糙滲系數(shù)提出了凹槽嵌固式正六邊形預(yù)制塊、Z字型混凝土預(yù)制塊和嵌固式四邊形空心預(yù)制塊等3種護(hù)坡體型,通過建立護(hù)坡消浪室內(nèi)物理模型試驗(yàn)系統(tǒng),對比分析了3種預(yù)制塊相對于傳統(tǒng)光面混凝土預(yù)制塊護(hù)坡的消浪效果,提出了3種預(yù)制塊糙滲系數(shù)計(jì)算取值。試驗(yàn)結(jié)果表明:與光面混凝土預(yù)制塊護(hù)坡相比,該文設(shè)計(jì)的3種預(yù)制塊護(hù)坡對波浪的爬高都有較大幅度的抑制,坡面上波浪爬高試驗(yàn)結(jié)果從小到大依次為凹槽嵌固式正六邊形預(yù)制塊、Z字型混凝土預(yù)制塊、嵌固式四邊形空心預(yù)制塊、光面混凝土預(yù)制塊;3種預(yù)制塊護(hù)坡相對于光面混凝土預(yù)制塊的波浪爬高衰減率(波浪爬高減小比例)依次為35.0%、30.2%和26.23%,計(jì)算得到對應(yīng)的糙滲系數(shù)取值分別為0.76、0.77、0.79。綜合消浪效果及節(jié)約工程成本分析,采用凹槽嵌固式正六邊形預(yù)制塊護(hù)坡最佳,具有良好的推廣價(jià)值和發(fā)展前景。

堤防;預(yù)制結(jié)構(gòu); 護(hù)坡;消浪;模型試驗(yàn);糙滲系數(shù)

0 引 言

近十幾年來,江西省針對鄱陽湖區(qū)重點(diǎn)圩堤防洪標(biāo)準(zhǔn)低、險(xiǎn)工險(xiǎn)段多的問題,開展了湖區(qū)堤防的除險(xiǎn)加固建設(shè),其建設(shè)項(xiàng)目主要有圩堤加高培厚、護(hù)坡護(hù)岸、堤基堤身防滲處理、涵閘加固等[1]。為保護(hù)堤防免受洪水沖刷、風(fēng)浪沖擊,多數(shù)湖區(qū)或河段都需設(shè)置護(hù)坡;堤防工程建設(shè)中,通常采用混凝土、干砌石、漿砌石、模裝混凝土、草皮等不同材料的護(hù)坡,用以提高抗沖、消浪、抗?jié)B能力。當(dāng)波浪行近堤岸時(shí),水體沿堤坡斜面爬升的垂直高度稱為波浪爬高[2],湖泊與水庫的堤岸、以及海塘等水工建筑物均由設(shè)計(jì)水位和波浪爬高來確定堤頂高程,因此護(hù)坡的消浪效果將直接影響堤防的設(shè)計(jì)高度。傳統(tǒng)光面混凝土預(yù)制塊護(hù)坡在我國土堤護(hù)坡工程中應(yīng)用最為廣泛,但其也存在消浪效果差,無排水反濾和安全性差等一系列問題[3-4],為解決這些問題,新型防浪預(yù)制塊的提出顯得尤為重要,如農(nóng)業(yè)引水湖泊及水庫堤防防護(hù)工程中,護(hù)坡預(yù)制塊具有良好的消浪效果,可提高水庫堤防防洪能力,保障農(nóng)業(yè)生產(chǎn)安全,同時(shí)預(yù)制塊護(hù)坡可起到降低堤防工程水土流失的作用[5-6],因此新型防浪預(yù)制塊的提出對土堤護(hù)坡工程具有重要意義。

在預(yù)制塊護(hù)坡體型結(jié)構(gòu)及其消浪效果研究方面, Mutray等[7]根據(jù)法國格勒諾布爾水力研究和應(yīng)用公司研制的扭王字塊設(shè)計(jì)出X型塊體,并對該塊體進(jìn)行了安放和結(jié)構(gòu)強(qiáng)度的研究。Merrifield等[8]設(shè)計(jì)的扭工字塊體(杜洛斯方塊)在東倫敦港防波堤中應(yīng)用非常成功,扭工字塊體孔隙率大,能較好地降低波浪爬高。張玉清等[9]結(jié)合沈陽市鳥島公園河道護(hù)坡工程,設(shè)計(jì)了鉸接式混凝土砌塊,并從水土保持效益、生態(tài)景觀效應(yīng)和經(jīng)濟(jì)效應(yīng)3個(gè)方面進(jìn)行了分析,表明該護(hù)坡具有良好的推廣前景。鄧海忠等[10-11]對傳統(tǒng)正六邊棱柱體混凝土預(yù)制塊護(hù)坡的結(jié)構(gòu)和功能進(jìn)行了改進(jìn),設(shè)計(jì)出堤壩凹形反濾排水式混凝土護(hù)坡預(yù)制塊。王旭君等[12]針對傳統(tǒng)正六邊形混凝土預(yù)制塊所具有的特性,經(jīng)過大量研究和分析,提出了設(shè)置有連鎖反濾凹槽的混凝土預(yù)制塊,改進(jìn)后的混凝土預(yù)制塊可降低工程成本。余廣明等[13]設(shè)計(jì)了翼型和蛙式2種混凝土護(hù)坡預(yù)制塊,并對其進(jìn)行了抗浪性能試驗(yàn),試驗(yàn)表明塊體的抗浪性能優(yōu)越。當(dāng)前預(yù)制塊研究主要針對結(jié)構(gòu)設(shè)計(jì)及在實(shí)際工程中應(yīng)用等方面[9-13],對于預(yù)制塊糙滲系數(shù)研究較少,而糙滲系數(shù)直接影響土堤護(hù)坡波浪爬高,是土堤堤頂高程設(shè)計(jì)必不可少的參數(shù),因此糙滲系數(shù)的獲取為預(yù)制塊的應(yīng)用和推廣帶來極大便利。本文以鄱陽湖上饒片區(qū)堤防工程為例,在前人研究的基礎(chǔ)上,提出3種預(yù)制塊護(hù)坡體型,并基于重力相似準(zhǔn)則設(shè)計(jì)并建立了護(hù)坡消浪室內(nèi)物理模型試驗(yàn)系統(tǒng),開展了波浪爬高室內(nèi)模型試驗(yàn),對比分析3種預(yù)制塊相對于傳統(tǒng)光面混凝土預(yù)制塊的消浪效果,計(jì)算這3種預(yù)制塊糙滲系數(shù),擬基于消浪效果的試驗(yàn)結(jié)果和工程造價(jià)提出最佳護(hù)坡體型,以期在土堤護(hù)坡[14-18]工程中得以推廣和發(fā)展。

1 預(yù)制塊護(hù)坡體型設(shè)計(jì)

1.1 預(yù)制塊結(jié)構(gòu)體型設(shè)計(jì)

土堤波浪爬高的主要影響因素有斜坡坡度、堤前水深、坡面糙率和透水性、風(fēng)浪要素以及相對于建筑物的入射波向等[19-21]。為了改善傳統(tǒng)光面混凝土預(yù)制塊安全性和整體性差、無反濾排水、波浪爬高高等問題[12],本文以增加預(yù)制塊糙率和透水性為基本原則,提出了凹槽嵌固式正六邊形預(yù)制塊、Z字型混凝土預(yù)制塊和嵌固式四邊形空心預(yù)制塊3種護(hù)坡體型,該3種預(yù)制塊護(hù)坡相對于傳統(tǒng)光面混凝土預(yù)制塊護(hù)坡增加了凹槽、消浪坎、排水孔以及鎖卡等結(jié)構(gòu),其中凹槽和消浪坎可以很大程度上增加預(yù)制塊糙率,排水孔及鎖卡之間形成的空隙加大了預(yù)制塊透水能力,鎖卡的設(shè)計(jì)還可防止預(yù)制塊發(fā)生滑移,增加護(hù)坡的整體穩(wěn)定性。新型預(yù)制塊護(hù)坡結(jié)構(gòu)尺寸的設(shè)計(jì)主要依據(jù)為《堤防工程設(shè)計(jì)規(guī)范》(GB50286-2013)(以下簡稱“規(guī)范”)要求以及近年來學(xué)者對護(hù)坡預(yù)制塊的研究成果[7-13]。

1)凹槽嵌固式正六邊形預(yù)制塊護(hù)坡。該預(yù)制塊是基于傳統(tǒng)光面混凝土預(yù)制塊改良設(shè)計(jì)的,預(yù)制塊為邊長40 cm的正六邊形結(jié)構(gòu)。排水孔孔徑按規(guī)范要求取值為10 cm;鎖卡設(shè)計(jì)為梯形,頂面和底面寬分別為4和7 cm,厚度與預(yù)制塊相等;消浪坎高為5 cm;凹槽截面為直徑5 cm半圓,預(yù)制塊結(jié)構(gòu)如圖1所示。

2)Z字型混凝土預(yù)制塊護(hù)坡。參考“規(guī)范”所列工程案例:①美國的密西西比河采用的鉸鏈混凝土排,由尺寸為122 cm×36 cm×7.6 cm的加筋混凝土板組成;②長江武漢河段天興洲護(hù)岸采用的鉸鏈混凝土板,尺寸為100 cm×40 cm×8 cm。基于上述工程案例取Z字型混凝土預(yù)制塊尺寸為100 cm×55 cm。該護(hù)坡通過鎖卡之間形成的空隙來增加透水性,因此相對于凹槽嵌固式正六邊形預(yù)制塊鎖卡尺寸有所增加,短邊上鎖卡尺寸較大,頂面和底面寬分別為10和15 cm,高為20 cm,長邊鎖卡頂面和底面寬分別為10和20 cm,高為5 cm。消浪坎的高度為5 cm,預(yù)制塊結(jié)構(gòu)如圖2所示。

3)嵌固式四邊形空心預(yù)制塊護(hù)坡。該護(hù)坡與Z字型混凝土預(yù)制塊相似均為四邊形結(jié)構(gòu),基于上述規(guī)范所舉工程案例取嵌固式四邊形空心預(yù)制塊尺寸為80 cm× 60 cm。預(yù)制塊4條邊上均設(shè)置了梯形鎖卡,鎖卡頂面和底面寬分別為10和20 cm,高為5 cm,由于該預(yù)制塊單塊塊體面積較大,因此設(shè)計(jì)中加大了排水孔孔徑,為15 cm,消浪坎未單獨(dú)設(shè)計(jì),而是將預(yù)制塊長邊鎖卡抬高5 cm組成消浪坎,凹槽截面為寬5 cm,高5 cm矩形,結(jié)構(gòu)如圖3所示。

設(shè)計(jì)的3種預(yù)制塊中凹槽嵌固式正六邊形預(yù)制塊表面粗糙度較大,且整體鋪設(shè)效果美觀;Z字型混凝土預(yù)制塊結(jié)構(gòu)簡單,制作和鋪設(shè)方便,鎖卡和消浪坎尺寸較大,單個(gè)塊體抗沖刷能力強(qiáng),不易發(fā)生沖刷破壞;嵌固式四邊形空心預(yù)制塊結(jié)構(gòu)較為復(fù)雜,但鎖卡之間作用牢固,單個(gè)塊體穩(wěn)定性好,其中凹槽嵌固式正六邊形預(yù)制塊和嵌固式四邊形空心預(yù)制塊凹槽與排水孔之間相互連通,可加速預(yù)制塊護(hù)坡表面水流排出,防止凹槽中滯留水流形成水墊層影響消浪效果。

1.2 預(yù)制塊厚度計(jì)算

在波浪壓力和浮托力作用下,為滿足預(yù)制塊護(hù)坡整體穩(wěn)定要求,預(yù)制塊護(hù)坡厚度可按《水工設(shè)計(jì)手冊》中公式計(jì)算

式中為預(yù)制塊厚度,m;為安全系數(shù),可采用壩坡穩(wěn)定安全系數(shù);γ為鋼筋混凝土容重,t/m3;γ為水的容重,t/m3;為沿堤坡方向預(yù)制塊長度,m;為堤坡與水平線所成夾角,(°);2為設(shè)計(jì)波高,m。

本文根據(jù)鄱陽湖上饒片區(qū)風(fēng)浪特性按上式計(jì)算得凹槽嵌固式正六邊形預(yù)制塊厚度為12 cm,Z字型混凝土預(yù)制塊和嵌固式四邊形空心預(yù)制塊厚度為15 cm。

2 預(yù)制塊護(hù)坡消浪物理模型試驗(yàn)材料與方法

2.1 模型試驗(yàn)設(shè)計(jì)與試驗(yàn)裝置

本次模型試驗(yàn)基于重力相似準(zhǔn)則設(shè)計(jì),以鄱陽湖上饒片區(qū)饒北河防洪堤左岸為例進(jìn)行模型制作,堤防原型高度為5 m,堤防斜坡坡率=1∶2.5,模型幾何比尺為1∶10。本次模型試驗(yàn)在波浪水槽中進(jìn)行,水槽兩側(cè)為透明玻璃,總長8 m,寬0.4 m,高1 m,在水槽尾端填筑堤防模型,斜坡迎水面前側(cè)放置造波機(jī),如圖4所示。造波系統(tǒng)采用推板式造波機(jī),推板與槽底鉸接且轉(zhuǎn)動(dòng)角度可供調(diào)節(jié),以此產(chǎn)生不同波高的波浪,通過調(diào)節(jié)造波機(jī)控制器可產(chǎn)生不同周期的波浪,如圖5所示。

各預(yù)制塊按選定幾何比尺1∶10制作,為保證試驗(yàn)結(jié)果的準(zhǔn)確性,對光面混凝土預(yù)制塊進(jìn)行勾縫處理,反濾層采用2 cm厚細(xì)沙墊層和土工布組合進(jìn)行反濾[22-23]。各預(yù)制塊護(hù)坡鋪設(shè)效果如圖6所示。

1.預(yù)制塊護(hù)坡 2.反濾層 3.土體 4.造波機(jī)

1.Prefabricated block revetment 2.Inverted filter 3.Soil 4.Wave maker

注:為堤前水深;為波高。

Note:is water depth;is wave height.

圖4 試驗(yàn)布置示意圖

Fig.4 Schematic diagram of experimental arrangement

a. 光面混凝土預(yù)制塊護(hù)坡a. Smooth concrete prefabricated block revetmentb. 凹槽嵌固式正六邊形預(yù)制塊護(hù)坡b. Concave and embedded regular hexagon type prefabricated block revetment c. Z字型混凝土預(yù)制塊護(hù)坡c. Z type prefabricated concrete block revetmentd. 嵌固式四邊形空心預(yù)制塊護(hù)坡d. Embedded quadrangle type prefabricated hollow block revetment

模型試驗(yàn)分別在3種不同堤前水深和3種不同造波周期組合工況下進(jìn)行,即每組堤前水深分別進(jìn)行3種不同造波周期下的波浪爬高試驗(yàn)。每種預(yù)制塊模型在不同工況下共進(jìn)行了9組試驗(yàn),測量各組試驗(yàn)波浪爬高。波浪爬高測量采取攝影測量法[24-25],波浪在坡面爬高的確定采用坡面波浪痕跡及攝影捕捉相結(jié)合的方法確定,該攝影測量為二維目標(biāo)測量,在堤防模型兩側(cè)設(shè)置標(biāo)尺,攝像機(jī)鏡頭與堤防斜坡面保持平行,則坡面上圖像將按一定比尺縮小呈現(xiàn)在像平面上,找出視頻中波浪爬高最大時(shí)刻截取圖片,借助AutoCAD工程軟件讀取斜坡面上波浪爬高(水痕最高處)在標(biāo)尺上讀數(shù);該方法的測量精度在模型試驗(yàn)之前進(jìn)行了測試,每10 cm誤差在±1 mm左右。

2.2 模型試驗(yàn)工況

模型試驗(yàn)堤前水深分別為23.6,30.6和37.15 cm,波浪周期分別為1.5,1.875和2.5 s,即各預(yù)制塊都進(jìn)行9個(gè)工況的模型試驗(yàn),分別測量各工況坡面波浪爬高[26-29],試驗(yàn)工況如表1所示。

表1 試驗(yàn)工況

3 模型試驗(yàn)結(jié)果與分析

3.1 消浪效果對比

模型試驗(yàn)中發(fā)現(xiàn),各預(yù)制塊坡面的最大波浪爬高均出現(xiàn)在前幾個(gè)周期中,因此本文測量前20個(gè)周期各預(yù)制塊波浪爬高值并取出最大波浪爬高進(jìn)行消浪效果對比,統(tǒng)計(jì)9種工況下最大波浪爬高如表2所示。

表2 預(yù)制塊坡面最大波浪爬高

除工況3、工況4和工況6外,其余6種工況坡面最大波浪爬高從小至大的總體規(guī)律依次為凹槽嵌固式正六邊形預(yù)制塊、Z字型混凝土預(yù)制塊、嵌固式四邊形空心預(yù)制塊、光面混凝土預(yù)制塊。從試驗(yàn)數(shù)據(jù)來看,工況3、工況4和工況6與其余6種工況下的坡面最大波浪爬高規(guī)律出現(xiàn)差異,其主要原因是該3種工況下波浪水流在坡面上出現(xiàn)了擾動(dòng)現(xiàn)象,當(dāng)坡面回落水流正好與來波相遇時(shí),坡面波浪水流將發(fā)生擾動(dòng);由于波浪水流擾動(dòng)的發(fā)生受波浪周期、波浪爬高以及回落水流流速等多個(gè)因素影響,因此在試驗(yàn)中很難避免,且同一工況下各預(yù)制塊擾動(dòng)程度也會(huì)不同;從試驗(yàn)拍攝的視頻中可以看到,工況3和工況6下嵌固式四邊形空心預(yù)制塊擾動(dòng)明顯,工況4下光面混凝土預(yù)制塊擾動(dòng)明顯。由于波浪水流擾動(dòng)對預(yù)制塊的消浪效果分析會(huì)產(chǎn)生一定程度的誤判,因此在分析預(yù)制塊護(hù)坡消浪效果時(shí),該3個(gè)工況數(shù)據(jù)不計(jì)入最終的統(tǒng)計(jì)分析。

本文以光面混凝土預(yù)制塊波浪爬高為基準(zhǔn),計(jì)算新設(shè)計(jì)的3種預(yù)制塊相對于光面混凝土預(yù)制塊波浪爬高衰減率用以分析其消浪效果,計(jì)算公式如下

式中為本文設(shè)計(jì)的3種預(yù)制塊相對光面混凝土預(yù)制塊波浪爬高衰減率,%;R為本文設(shè)計(jì)的3種預(yù)制塊波浪爬高,m;R為光面混凝土預(yù)制塊波浪爬高,m。

計(jì)算結(jié)果如表3所示,以該衰減率評(píng)定設(shè)計(jì)的3種預(yù)制塊的消浪效果,由表3中數(shù)據(jù)可知,設(shè)計(jì)的3種預(yù)制塊護(hù)坡中,凹槽嵌固式正六邊形預(yù)制塊護(hù)坡相對于光面混凝土預(yù)制塊護(hù)坡消浪效果最好,波浪爬高衰減35.0%,其次是Z字型混凝土預(yù)制塊,波浪爬高衰減30.2%,最后是嵌固式四邊形空心預(yù)制塊,波浪爬高衰減26.23%。

表3 各工況下3種預(yù)制塊相對于光面混凝土預(yù)制塊消浪效果

3.2 預(yù)制塊糙滲系數(shù)計(jì)算

根據(jù)規(guī)范中波浪爬高計(jì)算公式

式中R為累計(jì)頻率為的波浪爬高,m;Δ為斜坡的糙滲系數(shù);為經(jīng)驗(yàn)系數(shù);為波浪爬高累計(jì)頻率換算系數(shù);為斜坡坡率,=cot;為堤前波浪平均爬高,m;為堤前波浪波長,m。

同一工況下,式(3)中除糙滲系數(shù)不同外其余各參數(shù)取值均相同,光面混凝土預(yù)制塊糙滲系數(shù)取值在規(guī)范中已給出為1.0,根據(jù)試驗(yàn)中測量的光面混凝土預(yù)制塊波浪爬高及新設(shè)計(jì)的3種預(yù)制塊波浪爬高,采用比值法計(jì)算3種預(yù)制塊糙滲系數(shù)[30],計(jì)算結(jié)果如表4所示。

表4 預(yù)制塊坡面最大波浪爬高及3種預(yù)制塊糙滲系數(shù)

在實(shí)際工程設(shè)計(jì)中出于偏安全考慮,因此取6種工況中各預(yù)制塊糙滲系數(shù)計(jì)算最大值作為最終取值,即凹槽嵌固式正六邊形預(yù)制塊糙滲系數(shù)為0.76,Z字型混凝土預(yù)制塊糙滲系數(shù)為0.77,嵌固式四邊形空心預(yù)制塊糙滲系數(shù)為0.79。

3.3 工程造價(jià)分析

預(yù)制塊護(hù)坡工程造價(jià)對比主要分為2個(gè)部分,一是相同厚度下各預(yù)制塊護(hù)坡混凝土用量,二是根據(jù)消浪效果降低堤頂高程情況,通過這兩部分對比分析綜合評(píng)定各預(yù)制塊護(hù)坡工程造價(jià)。

取相同厚度為15 cm的凹槽嵌固式正六邊形預(yù)制塊、Z字型混凝土預(yù)制塊、嵌固式四邊形空心預(yù)制塊和光面混凝土預(yù)制塊護(hù)坡計(jì)算其每100 m2護(hù)坡面積混凝土用量,計(jì)算公式如下

式中為每100 m2堤防所需混凝土用量,m3;V為各預(yù)制塊單個(gè)塊體混凝土用量,m3;S為各預(yù)制塊單個(gè)塊體所占面積(包括部分空隙面積),m2。

計(jì)算結(jié)果如表5所示,由表可知,同等厚度的情況下,凹槽嵌固式正六邊形預(yù)制塊相對于光面混凝土預(yù)制塊每100 m2護(hù)坡面積混凝土用量減少17.13%;Z字型混凝土預(yù)制塊增加14.67%;嵌固式四邊形空心預(yù)制塊減少11.40%。3種預(yù)制塊相對于光面混凝土預(yù)制塊波浪爬高均有所衰減,堤頂高程也可相應(yīng)減小。以光面混凝土預(yù)制塊護(hù)坡波浪爬高為1 m為例,凹槽嵌固式正六邊形預(yù)制塊護(hù)坡相對于光面混凝土預(yù)制塊護(hù)坡可降低堤頂高程0.35 m,Z字型混凝土預(yù)制塊護(hù)坡可降低堤頂高程0.30 m,嵌固式四邊形空心預(yù)制塊護(hù)坡可降低堤頂高程0.26 m。

表5 工程造價(jià)分析

綜上分析可知,3種預(yù)制塊相對于光面混凝土預(yù)制塊護(hù)坡工程造價(jià)都有所降低,從造價(jià)考慮其中凹槽嵌固式正六邊形預(yù)制塊最好,其次是嵌固式四邊形空心預(yù)制塊,最后是Z字型混凝土預(yù)制塊。其中凹槽嵌固式正六邊形預(yù)制塊相對于光面混凝土預(yù)制塊消浪效果最好,且混凝土用量最少,故選取凹槽嵌固式正六邊形預(yù)制塊為最佳護(hù)坡體型。

4 結(jié) 論

本文以鄱陽湖上饒片區(qū)堤防工程為例,設(shè)計(jì)了3種防浪預(yù)制塊,通過室內(nèi)模型試驗(yàn),研究了設(shè)計(jì)的凹槽嵌固式正六邊形預(yù)制塊、Z字型混凝土預(yù)制塊和嵌固式四邊形空心預(yù)制塊相對于傳統(tǒng)光面混凝土預(yù)制塊的消浪效果,采用比值法計(jì)算了該3種預(yù)制塊的糙滲系數(shù),并進(jìn)行了工程造價(jià)對比。得到主要結(jié)論如下:

1)波浪爬高受很多的因素影響,其中糙滲系數(shù)是非常重要的一個(gè)參數(shù),當(dāng)增大預(yù)制塊表面糙率和透水性時(shí),可以很大程度上降低波浪爬高。

2)凹槽嵌固式正六邊形、Z字型、嵌固式四邊形空心預(yù)制塊中凹槽嵌固式正六邊形預(yù)制塊護(hù)坡相對光面混凝土預(yù)制塊護(hù)坡波浪爬高衰減35.0%,糙滲系數(shù)為0.76;Z字型混凝土預(yù)制塊波浪爬高相對光面混凝土預(yù)制塊護(hù)衰減30.2%,糙滲系數(shù)為0.77;嵌固式四邊形空心預(yù)制塊波浪爬高相對光面混凝土預(yù)制塊護(hù)坡衰減26.23%,糙滲系數(shù)為0.79。凹槽嵌固式正六邊形預(yù)制塊消浪效果最好,同時(shí)該預(yù)制塊護(hù)坡體型具有最低的工程造價(jià),為最佳護(hù)坡體型。

本文結(jié)果對于改善鄱陽湖區(qū)堤防護(hù)坡具有實(shí)用價(jià)值,波浪爬高的減小意味著可以降低堤防的堤頂高程,減小堤防工程量,降低工程造價(jià)。本文研究結(jié)果同樣可以適用于其他地區(qū)的土堤護(hù)坡工程,但預(yù)制塊厚度需根據(jù)實(shí)際工程中的風(fēng)浪特性進(jìn)行計(jì)算確定。

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Model test on wave dissipation effect of roughened embankment with permeable prefabricated block for slope protection

Li Huokun1, Du Lei1, Li Yijing1※, Xu Wangmin2, Liu Wugen2

(1.,,330031,; 2.,334000,)

Wave run-up is a key parameter in determining the crest elevation of earth embankments, and it is considerably affected by the wave reduction effect of protection slope. Smooth concrete prefabricated block is widely used in the slope protection of embankments. However, its wave reduction effect is relatively poor. To solve this problem, 3 new kinds of prefabricated blocks were designed to improve the wave reduction effect by increasing the roughness coefficient of the prefabricated block, including concave and embedded regular hexagon type prefabricated block, Z type prefabricated concrete block and embedded quadrangle type prefabricated hollow block. According to the formula in Handbook of hydraulic structure design, the thickness of prefabricated block was calculated, and then a laboratorial physical model experiment was performed in a wave flume for the slope protection and wave dissipation. Nine tests were carried out under 3 water depths (23.6, 30.6 and 37.15 cm) and 3 wave periods (1.5, 1.875 and 2.5 s). In the experiment, waves were produced by a wave maker, and the wave run-up was measured by a photogrammetric method. The wave reduction effects of the 3 new kinds of prefabricated blocks were assessed by the reduction ratio of the wave run-up compared with the smooth concrete prefabricated block. Additionally, the values of the 3 new kinds of prefabricated blocks’ roughness coefficient were proposed. The experiment results showed that, compared with the smooth concrete prefabricated block, the 3 kinds of prefabricated blocks proposed in this paper had obvious inhibiting effects on wave run-up. The concave and embedded regular hexagon type prefabricated block had the most inhibiting effect, followed by the Z type prefabricated concrete block and embedded quadrangle type prefabricated hollow block. Their wave run-up decay rates (the reduction ratio of the new designs to the smooth concrete prefabricated block) were 35.0%, 30.2% and 26.23%, respectively, and corresponding roughness coefficients were 0.76, 0.77 and 0.79, respectively. Finally, the economic benefits of the 3 kinds of new designed prefabricated blocks were analyzed in this paper. It was mainly divided into 2 parts, the revetment concrete amount with the same thickness, and the extent of crest elevation reduction by the wave reduction effects. According to the comprehensive comparison and analysis, the concave and embedded regular hexagon type prefabricated block consumed less concrete amount, which decreased by 17.13% compared with the smooth concrete prefabricated block, and wave run-up was more reduced. For example, if the wave run-up of the smooth concrete prefabricated block was 1.0 m, the concave and embedded regular hexagon type prefabricated block would be 0.65 m, the Z type prefabricated concrete block would be 0.70 m, and the embedded quadrangle type prefabricated hollow block would be 0.74 m. Consequently, considering the effect of revetment wave and economic benefit, the concave and embedded regular hexagon type prefabricated block is the best choice in the slope protection and has popularization value and development prospects.

embankments; prefabricated construction ; slope protection; attenuate waves; model test; roughness infiltration coefficient

10.11975/j.issn.1002-6819.2017.04.021

S277; TV871

A

1002-6819(2017)-04-0146-07

2106-06-15

2017-02-13

國家自然科學(xué)基金項(xiàng)目(51269019,51469015,41501454);江西省水利廳科技項(xiàng)目(KT201439)。

李火坤,男,湖南長沙人,教授,博士,主要從事水工水力學(xué)與工程安全檢測方面研究。南昌南昌大學(xué)建筑工程學(xué)院,330031。 Eamil:lihuokun@ncu.edu.cn

李怡靜,女,江西南昌人,副教授,博士,主要從事水利工程安全監(jiān)測方向研究。南昌南昌大學(xué)建筑工程學(xué)院,330031。 Eamil:ejinn@ncu.edu.cn

李火坤,杜 磊,李怡靜,徐旺敏,劉伍根. 土堤加糙透水式預(yù)制塊護(hù)坡消浪效果模型試驗(yàn)[J]. 農(nóng)業(yè)工程學(xué)報(bào),2017,33(4):146-152. doi:10.11975/j.issn.1002-6819.2017.04.021 http://www.tcsae.org

Li Huokun, Du Lei, Li Yijing, Xu Wangmin, Liu Wugen. Model test on wave dissipation effect of roughened embankment with permeable prefabricated block for slope protection[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2017, 33(4): 146-152. (in Chinese with English abstract) doi:10.11975/j.issn.1002-6819.2017.04.021 http://www.tcsae.org

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