由于水下作業比陸上工作條件復(fu)雜(za)，操作技術要求高(gao)，因而只有在特殊(shu)情況下才采用。

  水(shui)(shui)下堵(du)漏(lou)清(qing)基 ①建筑物基面的清(qing)理(li)：當(dang)水(shui)(shui)生物或(huo)水(shui)(shui)垢、水(shui)(shui)銹較輕時(shi)，用竹刷、鋼(gang)絲刷、刮(gua)刀、砍斧(fu)、鑿子(zi)或(huo)風動砂輪(lun)等清(qing)理(li);較重時(shi)則用高(gao)速(su)射流水(shui)(shui)清(qing)洗(xi)。②基坑清(qing)理(li)：一(yi)般由潛水(shui)(shui)員輔以工(gong)(gong)具進行;當(dang)工(gong)(gong)作(zuo)面或(huo)工(gong)(gong)作(zuo)量大(da)時(shi)，則先(xian)用挖(wa)掘機、挖(wa)泥船或(huo)氣(qi)泵進行初步清(qing)理(li)。

  水(shui)下鉆(zhan)(zhan)(zhan)孔(kong)(kong)(kong) 當孔(kong)(kong)(kong)深(shen)及孔(kong)(kong)(kong)徑較小或在豎直面上(shang)鉆(zhan)(zhan)(zhan)孔(kong)(kong)(kong)時(shi)，可用風動鑿巖機鉆(zhan)(zhan)(zhan)孔(kong)(kong)(kong)，由(you)潛水(shui)員在水(shui)下直接操作。當在閘(zha)壩上(shang)游進(jin)行(xing)帷幕補強灌漿(jiang)或鉆(zhan)(zhan)(zhan)大孔(kong)(kong)(kong)徑 孔(kong)(kong)(kong)時(shi)，一般采用設在船臺(tai)或浮排(pai)組(zu)成的工作臺(tai)上(shang)的回轉鉆(zhan)(zhan)(zhan)機鉆(zhan)(zhan)(zhan)孔(kong)(kong)(kong)。20世紀60年代以(yi)來(lai)，歐洲、美洲一些(xie) 和(he)日本廣泛采用了雙套管(guan)(其(qi)外套管(guan)用以(yi)固定鉆(zhan)(zhan)(zhan)孔(kong)(kong)(kong)位置，保護鉆(zhan)(zhan)(zhan)具免受流(liu)水(shui)沖擊;內套管(guan)頭(tou)(tou)部鑲(xiang)有環(huan)形鉆(zhan)(zhan)(zhan)頭(tou)(tou)，可以(yi)鉆(zhan)(zhan)(zhan)透(tou)覆蓋層達到基巖中)在深(shen)水(shui)域鉆(zhan)(zhan)(zhan)孔(kong)(kong)(kong)。