簡介
銀盤(pan)水(shui)(shui)(shui)(shui)電(dian)(dian)站(zhan)(zhan)正常(chang)蓄(xu)水(shui)(shui)(shui)(shui)位(wei)215m,死水(shui)(shui)(shui)(shui)位(wei)211.5m,保(bao)證(zheng)出力161.7MW,裝機(ji)容量(liang)600MW,多年平(ping)均發(fa)電(dian)(dian)量(liang)27.08億kW/h,庫水(shui)(shui)(shui)(shui)位(wei)每天在正常(chang)蓄(xu)水(shui)(shui)(shui)(shui)位(wei)215m和死水(shui)(shui)(shui)(shui)位(wei)211.5m之間變(bian)化。銀盤(pan)水(shui)(shui)(shui)(shui)電(dian)(dian)站(zhan)(zhan)水(shui)(shui)(shui)(shui)輪機(ji)正常(chang)運行(xing)水(shui)(shui)(shui)(shui)頭范圍(wei)為13~35.12m,加權平(ping)均水(shui)(shui)(shui)(shui)頭為29.66m,額定(ding)水(shui)(shui)(shui)(shui)頭26.5m。其運行(xing)水(shui)(shui)(shui)(shui)頭屬低(di)水(shui)(shui)(shui)(shui)頭且水(shui)(shui)(shui)(shui)頭變(bian)幅較大,該水(shui)(shui)(shui)(shui)頭是軸(zhou)流(liu)轉槳式機(ji)型較理想的運行(xing)范圍(wei)。軸(zhou)流(liu)轉槳式水(shui)(shui)(shui)(shui)輪機(ji)具有(you)效率曲線平(ping)坦、單(dan)位(wei)轉速高(gao)、穩(wen)定(ding)運行(xing)區域較寬(kuan)廣等(deng)優點,適(shi)用于(yu)低(di)水(shui)(shui)(shui)(shui)頭段且水(shui)(shui)(shui)(shui)頭變(bian)幅大的電(dian)(dian)站(zhan)(zhan)。經綜合分析比(bi)較,本(ben)電(dian)(dian)站(zhan)(zhan)選(xuan)用軸(zhou)流(liu)轉槳式水(shui)(shui)(shui)(shui)輪發(fa)電(dian)(dian)機(ji)組方案。
烏江銀盤水(shui)電(dian)(dian)站由重慶(qing)大唐國際武(wu)隆(long)水(shui)電(dian)(dian)開(kai)發有(you)限(xian)公(gong)司負責建設和運(yun)營管理(li),目前,前3臺機組(zu)已投產(chan)發電(dian)(dian),第4臺機組(zu)也將于2011年(nian)底前投產(chan)發電(dian)(dian)。4臺機組(zu)全(quan)部投產(chan)運(yun)行后(hou),每(mei)年(nian)將有(you)30億千瓦時電(dian)(dian)量(liang)并(bing)入重慶(qing)電(dian)(dian)網,可緩解重慶(qing)市電(dian)(dian)力緊張(zhang)局面(mian),并(bing)增加武(wu)隆(long)、彭水(shui)兩縣(xian)的財(cai)政(zheng)收入,帶動地(di)區經濟發展。
工程技術
按照工(gong)(gong)程(cheng)總體施工(gong)(gong)計劃安排,導流明渠混(hun)(hun)凝(ning)土(tu)(tu)縱向圍(wei)堰(yan)在2007年(nian)8月底完工(gong)(gong),該圍(wei)堰(yan)需從高程(cheng)172m澆至(zhi)堰(yan)頂(ding)217m,共上升45m,其(qi)中高程(cheng)184m以下為常態混(hun)(hun)凝(ning)土(tu)(tu),高程(cheng)184m以上為碾壓(ya)混(hun)(hun)凝(ning)土(tu)(tu),本工(gong)(gong)程(cheng)各類混(hun)(hun)凝(ning)土(tu)(tu)38.08萬立方米,混(hun)(hun)凝(ning)土(tu)(tu)月高峰(feng)期強度9.2萬立方米/月,混(hun)(hun)凝(ning)土(tu)(tu)小時高峰(feng)期強度280立方米/h,由于各種客(ke)觀原(yuan)因,工(gong)(gong)期滯后,為了(le)(le)確(que)保該工(gong)(gong)程(cheng)按期完成,黃河勘測規劃設計有(you)限公(gong)司(si)項(xiang)目監理(li)部(bu)、重(zhong)慶國(guo)際水電(dian)開發公(gong)司(si)項(xiang)目工(gong)(gong)程(cheng)部(bu)、以及(ji)中國(guo)水電(dian)十四局(ju)項(xiang)目部(bu)針對(dui)碾壓(ya)混(hun)(hun)凝(ning)土(tu)(tu)縱向圍(wei)堰(yan)快速施工(gong)(gong)方案作了(le)(le)深入(ru)細(xi)致(zhi)的(de)(de)研究,并組(zu)織技術人員(yuan)到(dao)外(wai)地考(kao)察學習,提出(chu)了(le)(le)采用大倉面(mian)斜(xie)層鋪(pu)筑法并取得了(le)(le)良好的(de)(de)效果。
該技術(shu)將碾壓層(ceng)由平(ping)層(ceng)改為1∶10~1∶20的斜層(ceng),斜層(ceng)鋪筑(zhu)法(fa)的具體做法(fa)是:開(kai)倉段先平(ping)層(ceng)鋪筑(zhu),且鋪筑(zhu)層(ceng)自(zi)下(xia)而上依(yi)次(ci)遞加,使新(xin)澆筑(zhu)的混凝土表面(mian)(mian)形成(cheng)一個(ge)斜面(mian)(mian),至收倉端大部分(fen)混凝土按此斜面(mian)(mian)鋪筑(zhu),收倉段通(tong)過幾個(ge)依(yi)次(ci)加長(chang)的平(ping)層(ceng)收倉,即平(ping)層(ceng)段、斜層(ceng)段、平(ping)層(ceng)段三部分(fen)組成(cheng)(見圖1)。
避(bi)免在坡腳(jiao)部位(wei)(wei)形成薄(bo)層尖(jian)(jian)腳(jiao)和嚴格處理(li)二次污(wu)染是保證斜(xie)層鋪筑法施工(gong)(gong)質量的兩個(ge)主要問題(ti),因薄(bo)層尖(jian)(jian)腳(jiao)部位(wei)(wei)骨料易(yi)被壓碎(sui),在坡腳(jiao)部位(wei)(wei)應(ying)由人工(gong)(gong)清(qing)(qing)理(li)骨料,清(qing)(qing)除坡腳(jiao)處厚度(du)小于10~20cm尖(jian)(jian)腳(jiao)部位(wei)(wei)。其施工(gong)(gong)工(gong)(gong)藝(yi)流程同平層鋪筑法一致,在此不(bu)再贅述。
特殊氣象條件下施工
高溫(wen)條件(jian)下的碾壓混凝土施工(gong)
高溫天(tian)氣(qi)施(shi)工,保證施(shi)工質量(liang)最根本的途徑(jing)是大幅度削減層(ceng)間(jian)(jian)(jian)間(jian)(jian)(jian)隔時間(jian)(jian)(jian),同時采用控(kong)制(zhi)和補(bu)償表面(mian)水(shui)分蒸發散失的措(cuo)施(shi)。斜(xie)層(ceng)鋪筑(zhu)法,人為縮小澆(jiao)筑(zhu)面(mian)積,大幅度削減層(ceng)間(jian)(jian)(jian)間(jian)(jian)(jian)隔時間(jian)(jian)(jian),對(dui)混(hun)凝土的層(ceng)面(mian)結合質量(liang)和抗(kang)剪能力都有可靠(kao)保證。
(1)施(shi)工倉面覆蓋(gai)
高溫(wen)條件下(xia),采用保溫(wen)被對倉(cang)面及(ji)時進行覆蓋,不(bu)僅可(ke)以起到保溫(wen)保濕的(de)作(zuo)用,還可(ke)以延緩碾壓混凝(ning)土(tu)的(de)初凝(ning)時間(jian),減小VC值的(de)增加,同時對運(yun)輸(shu)車輛設置(zhi)遮陽(yang)遮雨(yu)棚,以降低暴雨(yu)對混凝(ning)土(tu)拌(ban)和物含水量(liang)的(de)影響。
(2)施工倉面噴霧
噴(pen)(pen)霧(wu)(wu)降(jiang)溫(wen)(wen)是夏季高溫(wen)(wen)施(shi)工的重要(yao)質(zhi)量保證措(cuo)施(shi)之一。本工程倉(cang)(cang)面(mian)安設(she)4臺(tai)噴(pen)(pen)霧(wu)(wu)機(ji),同(tong)時配有沖毛槍(qiang),對攤鋪的混凝(ning)土表(biao)面(mian)不斷噴(pen)(pen)霧(wu)(wu),效果較好,未發現失(shi)水變白,結(jie)硬現象(xiang)。若噴(pen)(pen)霧(wu)(wu)效果良(liang)好,可降(jiang)低(di)倉(cang)(cang)面(mian)溫(wen)(wen)度3℃左右,減(jian)小(xiao)了溫(wen)(wen)度倒灌,營(ying)造了適(shi)宜澆筑(zhu)的倉(cang)(cang)面(mian)小(xiao)氣(qi)候。國內外(wai)資料(liao)證明:VC值的大小(xiao)與壓實度及強度有密切關系。VC值損(sun)失(shi)在1~2h內影響(xiang)不大,大于2h后VC值損(sun)失(shi)成(cheng)倍增長。通過氣(qi)溫(wen)(wen)在29℃時,對倉(cang)(cang)面(mian)噴(pen)(pen)霧(wu)(wu)和未噴(pen)(pen)霧(wu)(wu)兩種工況下VC值觀(guan)測結(jie)果(見(jian)表(biao)1)可知,做好倉(cang)(cang)面(mian)噴(pen)(pen)霧(wu)(wu)降(jiang)溫(wen)(wen)工作,減(jian)小(xiao)VC值損(sun)失(shi),必須(xu)引起高度重視(shi)。
雨天施工
在降(jiang)雨(yu)(yu)強度小(xiao)于3mm/h的(de)條(tiao)件下,可覆蓋防(fang)雨(yu)(yu)布繼續施(shi)工,當降(jiang)雨(yu)(yu)強度達到或超過3mm/h時,應停(ting)止(zhi)拌和,迅速完成尚未進行的(de)卸料、平倉和碾壓(ya)作業,并采取防(fang)雨(yu)(yu)和排水措施(shi)。當雨(yu)(yu)停(ting)時,適當調大(da)VC值(zhi),這(zhe)樣(yang)有利于提高(gao)碾壓(ya)層面結合(he)質(zhi)量。