當出現因沉(chen)(chen)(chen)井(jing)(jing)自身重力(li)偏輕下(xia)(xia)(xia)沉(chen)(chen)(chen)困難時，沉(chen)(chen)(chen)井(jing)(jing)排(pai)(pai)水(shui)(shui)(shui)施工(gong)方(fang)案，可采用井(jing)(jing)外高壓射水(shui)(shui)(shui)、降低井(jing)(jing)內水(shui)(shui)(shui)位等(deng)方(fang)法下(xia)(xia)(xia)沉(chen)(chen)(chen)。在(zai)結構受力(li)允許的條件(jian)下(xia)(xia)(xia)，也可以(yi)采用壓重或(huo)接高沉(chen)(chen)(chen)井(jing)(jing)下(xia)(xia)(xia)沉(chen)(chen)(chen)。沉(chen)(chen)(chen)井(jing)(jing)下(xia)(xia)(xia)沉(chen)(chen)(chen)施工(gong)有排(pai)(pai)水(shui)(shui)(shui)除(chu)土(tu)和(he)不排(pai)(pai)水(shui)(shui)(shui)除(chu)土(tu)兩種方(fang)法。通常(chang)采用不排(pai)(pai)水(shui)(shui)(shui)除(chu)土(tu)的方(fang)法。采用排(pai)(pai)水(shui)(shui)(shui)除(chu)土(tu)下(xia)(xia)(xia)沉(chen)(chen)(chen)的方(fang)法要有安(an)全措施，下(xia)(xia)(xia)沉(chen)(chen)(chen)井(jing)(jing)施工(gong)，防止(zhi)發生人身安(an)全事(shi)故。沉(chen)(chen)(chen)井(jing)(jing)應(ying)用范圍：如因場地狹窄，同(tong)時受附(fu)近建筑物(wu)或(huo)其他因素條件(jian)的限制(zhi)，而不適宜(yi)采用大開挖的地點，合肥沉(chen)(chen)(chen)井(jing)(jing)施工(gong)，可采用沉(chen)(chen)(chen)井(jing)(jing)法施工(gong)。

沉(chen)井(jing)(jing)優點：占地面積小(xiao)，不需要(yao)板(ban)樁圍(wei)護。挖土(tu)量小(xiao)，對(dui)鄰(lin)近建筑的影響(xiang)比較小(xiao)，沉(chen)井(jing)(jing)施工工藝，操(cao)作簡便，無須特(te)殊的設備。沉(chen)井(jing)(jing)下沉(chen)時(shi)(shi)，不宜(yi)使用(yong)(yong)方法。遇到石塊(kuai)、巖層等特(te)殊情況(kuang)，經有關方面批準(zhun)采用(yong)(yong)除(chu)(chu)土(tu)和炮震助(zhu)沉(chen)方法時(shi)(shi)，應嚴(yan)格控(kong)制藥量。井(jing)(jing)底(di)下沉(chen)至(zhi)設計標高2．om以(yi)上時(shi)(shi)，應放慢下沉(chen)速度(du)，控(kong)制井(jing)(jing)內除(chu)(chu)土(tu)量和除(chu)(chu)土(tu)位(wei)置(zhi)，以(yi)求沉(chen)井(jing)(jing)平穩(wen)下沉(chen)、正確就(jiu)位(wei)。

沉(chen)(chen)(chen)井(jing)(jing)下(xia)沉(chen)(chen)(chen)施(shi)工(gong)有(you)排(pai)水(shui)(shui)(shui)除(chu)土(tu)和不(bu)排(pai)水(shui)(shui)(shui)除(chu)土(tu)兩(liang)種方(fang)(fang)法。通(tong)常采用(yong)不(bu)排(pai)水(shui)(shui)(shui)除(chu)土(tu)的(de)方(fang)(fang)法。采用(yong)排(pai)水(shui)(shui)(shui)除(chu)土(tu)下(xia)沉(chen)(chen)(chen)的(de)方(fang)(fang)法要有(you)安全(quan)措(cuo)施(shi)，防(fang)止(zhi)發生人身安全(quan)事故。沉(chen)(chen)(chen)井(jing)(jing)下(xia)沉(chen)(chen)(chen)前，應對(dui)沉(chen)(chen)(chen)井(jing)(jing)附近(jin)的(de)堤壩(ba)、建筑物和施(shi)工(gong)設備采取有(you)效的(de)防(fang)護措(cuo)施(shi)，并(bing)在下(xia)沉(chen)(chen)(chen)過程(cheng)中，經常進行沉(chen)(chen)(chen)降觀(guan)測，觀(guan)察基線、基點的(de)設置情況。沉(chen)(chen)(chen)井(jing)(jing)如發生偏斜(xie)必要時可以在沉(chen)(chen)(chen)井(jing)(jing)頂面(mian)施(shi)加水(shui)(shui)(shui)平力扶正。糾正沉(chen)(chen)(chen)井(jing)(jing)中位(wei)位(wei)置發生偏移的(de)方(fang)(fang)法是先使(shi)沉(chen)(chen)(chen)井(jing)(jing)傾斜(xie)，然后(hou)均勻除(chu)土(tu)，使(shi)沉(chen)(chen)(chen)井(jing)(jing)底中心(xin)線下(xia)沉(chen)(chen)(chen)至設計中心(xin)線后(hou)，再進行糾偏。