一、砂石墊層的施工要求有哪些
1、砂石墊層的材料必須具有良好的振實加密性能,宜選用碎石、卵石、角礫、圓礫、礫砂、粗砂、中砂(sha)或石(shi)(shi)屑(粒徑(jing)小于(yu)(yu)2mm的(de)部分(fen)不(bu)應超過總(zong)重(zhong)的(de)45%),且應級配良好,不(bu)含植物殘(can)體、垃圾等雜物。若只用粉(fen)細(xi)砂(sha)或石(shi)(shi)粉(fen)(粒徑(jing)小于(yu)(yu)0.075 mm的(de)部分(fen)不(bu)超過總(zong)重(zhong)的(de)90%)時,應均勻摻入(ru)不(bu)少(shao)于(yu)(yu)總(zong)重(zhong)30%的(de)碎石(shi)(shi)或卵石(shi)(shi)。砂(sha)石(shi)(shi)的(de)最大粒徑(jing)不(bu)宜大于(yu)(yu)50mm。
2、基坑(keng)開挖時(shi)應(ying)避(bi)免坑(keng)底(di)(di)土層(ceng)(ceng)(ceng)受擾動,可保(bao)留(liu)約200mm厚的(de)(de)土層(ceng)(ceng)(ceng)暫不挖去,待鋪填墊(dian)(dian)層(ceng)(ceng)(ceng)前再挖至設計標(biao)高(gao)。嚴禁(jin)擾動墊(dian)(dian)層(ceng)(ceng)(ceng)下(xia)(xia)(xia)的(de)(de)軟(ruan)弱(ruo)土層(ceng)(ceng)(ceng),防(fang)止(zhi)(zhi)其被踐(jian)踏、受凍(dong)或受水(shui)浸泡。在碎石墊(dian)(dian)層(ceng)(ceng)(ceng)底(di)(di)部(bu)宜(yi)設置150~300mm厚的(de)(de)砂墊(dian)(dian)層(ceng)(ceng)(ceng)或鋪一層(ceng)(ceng)(ceng)土工(gong)(gong)織物,以防(fang)止(zhi)(zhi)軟(ruan)弱(ruo)土層(ceng)(ceng)(ceng)表面的(de)(de)局部(bu)破壞,同時(shi)必須(xu)防(fang)止(zhi)(zhi)基坑(keng)邊坡坍土混(hun)入墊(dian)(dian)層(ceng)(ceng)(ceng)。在地(di)下(xia)(xia)(xia)水(shui)位(wei)以下(xia)(xia)(xia)施(shi)(shi)工(gong)(gong)時(shi),應(ying)采(cai)取降低地(di)下(xia)(xia)(xia)水(shui)位(wei)的(de)(de)措施(shi)(shi)(水(shui)撼法施(shi)(shi)工(gong)(gong)除(chu)外),使基坑(keng)保(bao)持無積水(shui)狀態。如因墊(dian)(dian)層(ceng)(ceng)(ceng)下(xia)(xia)(xia)方土質差異而使墊(dian)(dian)層(ceng)(ceng)(ceng)底(di)(di)面標(biao)高(gao)不一時(shi),基坑(keng)(槽)底(di)(di)宜(yi)挖成階梯形,施(shi)(shi)工(gong)(gong)時(shi)按先深后(hou)淺的(de)(de)順序進行,并應(ying)注意搭(da)接處(chu)的(de)(de)質量。
3、砂(sha)石墊層(ceng)施(shi)工(gong)(gong)的(de)關鍵(jian)是將(jiang)砂(sha)石材料振(zhen)實(shi)(shi)加密(mi)到設計(ji)要求的(de)密(mi)實(shi)(shi)度(壓實(shi)(shi)系(xi)數0.94~0.97)。如要求進(jin)一步提高(gao)砂(sha)石墊層(ceng)的(de)質量(liang),則宜加大機械的(de)功率。砂(sha)石墊層(ceng)的(de)施(shi)工(gong)(gong)方法有振(zhen)實(shi)(shi)法、水撼法、夯實(shi)(shi)法、碾壓法等(deng)多種,可(ke)根據砂(sha)石材料、地(di)質條件、施(shi)工(gong)(gong)設備等(deng)條件選用。施(shi)工(gong)(gong)時應(ying)分層(ceng)鋪筑,在(zai)下層(ceng)的(de)密(mi)實(shi)(shi)度經檢驗達(da)到合格要求后,方可(ke)進(jin)行(xing)上(shang)層(ceng)施(shi)工(gong)(gong)。砂(sha)墊層(ceng)施(shi)工(gong)(gong)時的(de)含水量(liang)對壓實(shi)(shi)效果(guo)影響很大,一般(ban)以潤濕到接近(jin)飽和狀(zhuang)態時效果(guo)最好。
二、砂石墊層成品有哪些保護措施
1、施工時(shi)應妥(tuo)善保護標(biao)高(gao)控制樁,防止碰撞位移,并(bing)應經常(chang)復測。
2、對伸出墻(qiang)的(de)設備管線、埋(mai)入墊層中的(de)各種管線均應妥善保護,防止施工時(shi)碰撞或(huo)損(sun)壞(huai)。
3、施工中(zhong)遇(yu)雨、雪天要做臨時覆蓋,以防墊層被浸泡或受(shou)凍。
4、墊層施工(gong)完(wan)后,應及時進行下道工(gong)序施工(gong),否則,應進行圍(wei)擋和臨時遮蓋.并經常灑水(shui)濕潤。
5、施工完的墊(dian)層不(bu)得在上堆放重(zhong)物和行駛車輛。