井(jing)底下沉(chen)至設(she)計(ji)(ji)標高2．om以上時，應放慢下沉(chen)速度，控制井(jing)內(nei)(nei)除(chu)(chu)土量(liang)和(he)除(chu)(chu)土位置，以求沉(chen)井(jing)平穩下沉(chen)、正確就(jiu)位。沉(chen)井(jing)施工(gong)(gong)前(qian)，應詳細調查施工(gong)(gong)期間內(nei)(nei)的洪汛、凌汛、河床沖(chong)涮、通航及(ji)漂流物(wu)等情(qing)況，并根據調查情(qing)況制定具體(ti)措施，確保(bao)安全(quan)。沉(chen)井(jing)下沉(chen)前(qian)，應根據設(she)計(ji)(ji)單位提供(gong)的地質資料(liao)決(jue)定是否需要(yao)增(zeng)補施工(gong)(gong)勘探，沉(chen)井(jing)基礎(chu)施工(gong)(gong)，為(wei)編制施工(gong)(gong)技術方案提供(gong)準確依據。

應隨(sui)時保持沉(chen)(chen)井(jing)(jing)正位(wei)(wei)豎直下(xia)(xia)沉(chen)(chen)，每下(xia)(xia)沉(chen)(chen)1m至少(shao)檢查一次。沉(chen)(chen)井(jing)(jing)人土(tu)(tu)(tu)深度(du)小于沉(chen)(chen)井(jing)(jing)平面尺寸(cun)的(de)1．5～2．0倍時，出(chu)現傾斜，沉(chen)(chen)井(jing)(jing)下(xia)(xia)沉(chen)(chen)施工，應密切注意校正糾偏。井(jing)(jing)底(di)下(xia)(xia)沉(chen)(chen)至設計標(biao)高2．om以上時，應放慢下(xia)(xia)沉(chen)(chen)速度(du)，控制井(jing)(jing)內除土(tu)(tu)(tu)量(liang)和除土(tu)(tu)(tu)位(wei)(wei)置，以求(qiu)沉(chen)(chen)井(jing)(jing)平穩下(xia)(xia)沉(chen)(chen)、正確(que)就位(wei)(wei)。將(jiang)事先(xian)在地面上用鋼筋混凝土(tu)(tu)(tu)制成的(de)井(jing)(jing)筒形狀的(de)結構作(zuo)為基(ji)坑(keng)坑(keng)壁(bi)的(de)支撐，在井(jing)(jing)壁(bi)的(de)保護下(xia)(xia)，用機械和人工在井(jing)(jing)內挖土(tu)(tu)(tu)，并在其自重作(zuo)用下(xia)(xia)沉(chen)(chen)入土(tu)(tu)(tu)中的(de)結構物稱為沉(chen)(chen)井(jing)(jing)。

沉(chen)(chen)(chen)井(jing)(jing)(jing)基(ji)礎施(shi)(shi)(shi)(shi)工(gong)一(yi)般可(ke)分為(wei)早地(di)(di)施(shi)(shi)(shi)(shi)工(gong)、水中筑島及浮運(yun)沉(chen)(chen)(chen)井(jing)(jing)(jing)三種。施(shi)(shi)(shi)(shi)工(gong)前(qian)應(ying)(ying)詳細了解場地(di)(di)的(de)(de)(de)地(di)(di)質和水文條件。水中施(shi)(shi)(shi)(shi)工(gong)應(ying)(ying)做好河流汛(xun)期、河床沖(chong)刷、通(tong)(tong)航(hang)及漂(piao)流物(wu)等調(diao)查(cha)研究，充分利(li)用(yong)枯水季節，制訂詳細的(de)(de)(de)施(shi)(shi)(shi)(shi)工(gong)計劃及必要的(de)(de)(de)措施(shi)(shi)(shi)(shi)，確保(bao)施(shi)(shi)(shi)(shi)工(gong)安(an)(an)全。 沉(chen)(chen)(chen)井(jing)(jing)(jing)應(ying)(ying)用(yong)范圍：沉(chen)(chen)(chen)井(jing)(jing)(jing)可(ke)用(yong)作(zuo)礦(kuang)區的(de)(de)(de)豎井(jing)(jing)(jing)，面積(ji)比較小(xiao)，一(yi)般為(wei)圓形(xing)，直(zhi)徑(jing)在(zai)15m以內(nei)。但下沉(chen)(chen)(chen)深(shen)度卻很深(shen)，沉(chen)(chen)(chen)井(jing)(jing)(jing)施(shi)(shi)(shi)(shi)工(gong)，一(yi)般要在(zai)100m以上，可(ke)用(yong)作(zuo)上下人員、材料、產品(煤和礦(kuang)石)的(de)(de)(de)豎向(xiang)通(tong)(tong)道，同(tong)時還可(ke)作(zuo)為(wei)豎向(xiang)風(feng)道之(zhi)用(yong)。沉(chen)(chen)(chen)井(jing)(jing)(jing)施(shi)(shi)(shi)(shi)工(gong)前(qian)，污水沉(chen)(chen)(chen)井(jing)(jing)(jing)施(shi)(shi)(shi)(shi)工(gong)，應(ying)(ying)詳細調(diao)查(cha)施(shi)(shi)(shi)(shi)工(gong)期間內(nei)的(de)(de)(de)洪汛(xun)、凌汛(xun)、河床沖(chong)涮、通(tong)(tong)航(hang)及漂(piao)流物(wu)等情況(kuang)，并根據調(diao)查(cha)情況(kuang)制定具體措施(shi)(shi)(shi)(shi)，確保(bao)安(an)(an)全。