設備的選型

CFG樁可(ke)選(xuan)用振(zhen)動(dong)(dong)(dong)沉管鉆機或(huo)長(chang)螺旋鉆機施工(gong)(gong)(gong)(gong)。具體(ti)選(xuan)用哪一類(lei)成(cheng)(cheng)(cheng)(cheng)樁機械和什么型號，要視工(gong)(gong)(gong)(gong)程的(de)具體(ti)情況而定。對(dui)(dui)于(yu)粘性土(tu)、粉(fen)土(tu)、淤泥(ni)質土(tu)采用振(zhen)動(dong)(dong)(dong)沉管成(cheng)(cheng)(cheng)(cheng)樁工(gong)(gong)(gong)(gong)藝。對(dui)(dui)存在的(de)夾(jia)有硬土(tu)層地質條件的(de)地區(qu)，使(shi)用振(zhen)動(dong)(dong)(dong)沉管機施工(gong)(gong)(gong)(gong)，會對(dui)(dui)已成(cheng)(cheng)(cheng)(cheng)的(de)樁造成(cheng)(cheng)(cheng)(cheng)較大的(de)振(zhen)動(dong)(dong)(dong)，導致樁體(ti)被震(zhen)(zhen)裂或(huo)震(zhen)(zhen)斷。對(dui)(dui)于(yu)靈敏度(du)較高的(de)土(tu)，振(zhen)動(dong)(dong)(dong)會造成(cheng)(cheng)(cheng)(cheng)土(tu)的(de)結構強度(du)破壞、承載力下降，可(ke)采用螺旋鉆預引孔(kong)，武漢CFG樁，再用振(zhen)動(dong)(dong)(dong)沉管成(cheng)(cheng)(cheng)(cheng)樁工(gong)(gong)(gong)(gong)藝。對(dui)(dui)于(yu)成(cheng)(cheng)(cheng)(cheng)孔(kong)要求質量高的(de)地區(qu)，使(shi)用長(chang)螺旋鉆孔(kong)管內泵(beng)壓成(cheng)(cheng)(cheng)(cheng)樁工(gong)(gong)(gong)(gong)藝。本標段設計采用長(chang)螺旋鉆機施工(gong)(gong)(gong)(gong)。

灌注混凝土

長(chang)(chang)螺旋(xuan)鉆(zhan)(zhan)機鉆(zhan)(zhan)至設(she)計標高，停止(zhi)(zhi)鉆(zhan)(zhan)進，向鉆(zhan)(zhan)桿(gan)(gan)芯(xin)管(guan)(guan)泵送混(hun)(hun)(hun)(hun)凝(ning)(ning)土(tu)(tu)(tu)灌(guan)(guan)注，當(dang)鉆(zhan)(zhan)桿(gan)(gan)芯(xin)管(guan)(guan)中充(chong)滿(man)混(hun)(hun)(hun)(hun)合料，開始提(ti)升鉆(zhan)(zhan)桿(gan)(gan)，壓灌(guan)(guan)混(hun)(hun)(hun)(hun)合料，一(yi)邊拔(ba)(ba)管(guan)(guan)，一(yi)邊泵送，嚴禁先提(ti)管(guan)(guan)后泵料。混(hun)(hun)(hun)(hun)凝(ning)(ning)土(tu)(tu)(tu)坍落度、拌合時(shi)間應(ying)按(an)工(gong)藝性試驗確定(ding)的參數(shu)(shu)進行控制，攪拌時(shi)間不得(de)少于1min。泵送混(hun)(hun)(hun)(hun)凝(ning)(ning)土(tu)(tu)(tu)，CFG樁(zhuang)單(dan)價，嚴禁先拔(ba)(ba)管(guan)(guan)后泵送混(hun)(hun)(hun)(hun)凝(ning)(ning)土(tu)(tu)(tu)（特別是端承樁(zhuang)），拔(ba)(ba)管(guan)(guan)時(shi)鉆(zhan)(zhan)桿(gan)(gan)必(bi)須停止(zhi)(zhi)轉動，拔(ba)(ba)管(guan)(guan)速(su)(su)率應(ying)按(an)試樁(zhuang)確定(ding)參數(shu)(shu)進行控制，拔(ba)(ba)管(guan)(guan)速(su)(su)度均勻(yun)，穿透地質較硬地段(duan)，采(cai)用低檔(dang)慢速(su)(su)鉆(zhan)(zhan)進，CFG樁(zhuang)施工(gong)，軟弱(ruo)地層，快(kuai)速(su)(su)鉆(zhan)(zhan)進，以降低擴孔系數(shu)(shu)；混(hun)(hun)(hun)(hun)凝(ning)(ning)土(tu)(tu)(tu)泵送也必(bi)須連續。若(ruo)混(hun)(hun)(hun)(hun)凝(ning)(ning)土(tu)(tu)(tu)供(gong)應(ying)不及時(shi)，造(zao)成鉆(zhan)(zhan)機等料的情況，時(shi)間較長(chang)(chang)可能造(zao)成斷樁(zhuang)或抱鉆(zhan)(zhan)現象，尤(you)其是在飽和砂土(tu)(tu)(tu)、粉土(tu)(tu)(tu)層。混(hun)(hun)(hun)(hun)凝(ning)(ning)土(tu)(tu)(tu)應(ying)灌(guan)(guan)注至設(she)計CFG樁(zhuang)頂(ding)標高以上50cm，停止(zhi)(zhi)泵送混(hun)(hun)(hun)(hun)凝(ning)(ning)土(tu)(tu)(tu)。灌(guan)(guan)注混(hun)(hun)(hun)(hun)凝(ning)(ning)土(tu)(tu)(tu)方量不得(de)少于設(she)計樁(zhuang)長(chang)(chang)加超灌(guan)(guan)樁(zhuang)頭的體(ti)積(ji)。

截樁頭和開挖樁間土

樁(zhuang)(zhuang)間土開挖時，挖掘機易碰撞樁(zhuang)(zhuang)頭(tou)造(zao)成(cheng)淺層(ceng)斷(duan)樁(zhuang)(zhuang)，施工中采取樁(zhuang)(zhuang)頭(tou)兩(liang)次截樁(zhuang)(zhuang)方案，避免人(ren)為(wei)造(zao)成(cheng)樁(zhuang)(zhuang)頭(tou)破壞(huai)：一是在CFG樁(zhuang)(zhuang)灌注完成(cheng)后砼(tong)凝固之前，濕截樁(zhuang)(zhuang)即(ji)采用小挖掘機將樁(zhuang)(zhuang)頭(tou)砼(tong)和鉆泥一起清理(li)出去， 留30~50cm不截，CFG樁(zhuang)(zhuang)多少錢一米，強(qiang)度達到80%后，使用小挖掘機（斗寬0.6m）開挖樁(zhuang)(zhuang)間土，使用改裝后的(de)切(qie)(qie)割(ge)機進行(xing)切(qie)(qie)割(ge)，減少對樁(zhuang)(zhuang)體的(de)破壞(huai)，切(qie)(qie)割(ge)完成(cheng)后，斷(duan)面平整。