水库输水洞选用土工膜防渗处理的特点
土(tu)工(gong)膜由两层(ceng)土(tu)工(gong)膜和(he)中间土(tu)工(gong)膜组(zu)成(cheng)，具有(you)良好(hao)的(de)防(fang)(fang)渗(shen)性(xing)能(neng)，具有(you)良好(hao)的(de)防(fang)(fang)渗(shen)性(xing)能(neng)，并(bing)且具有(you)良好(hao)的(de)延展性(xing)，施(shi)工(gong)简单，施(shi)工(gong)成(cheng)本低(di)，施(shi)工(gong)周期短。
土(tu)(tu)工(gong)(gong)(gong)(gong)膜(mo)施(shi)工(gong)(gong)(gong)(gong)常用聚乙(yi)烯(PE)和PVC(PVC)两种。聚乙(yi)烯膜(mo)施(shi)工(gong)(gong)(gong)(gong)质量较稳定，且焊缝质量检(jian)验方便，工(gong)(gong)(gong)(gong)程费用低，施(shi)工(gong)(gong)(gong)(gong)速度快，具有相(xiang)当(dang)的防渗性能。本工(gong)(gong)(gong)(gong)程采用聚乙(yi)烯复(fu)合土(tu)(tu)工(gong)(gong)(gong)(gong)膜(mo)(SN2/PE-16-300-0.3)：土(tu)(tu)工(gong)(gong)(gong)(gong)布150g/m2，标称断(duan)裂强度16kN/m，幅宽(kuan)6m，膜(mo)材厚(hou)度0.3mm。
复(fu)合(he)型土(tu)(tu)工(gong)膜(mo)(mo)(mo)防(fang)渗体(ti)(ti)的施工(gong)包括防(fang)护层(ceng)(ceng)(ceng)、复(fu)合(he)土(tu)(tu)工(gong)膜(mo)(mo)(mo)防(fang)渗层(ceng)(ceng)(ceng)、铺膜(mo)(mo)(mo)基面三层(ceng)(ceng)(ceng)。在(zai)施工(gong)时(shi)，需先(xian)将坝前土(tu)(tu)层(ceng)(ceng)(ceng)清(qing)除淤泥防(fang)渗处理(li)及(ji)杂(za)物打紧、平整，然后直接铺在(zai)坝体(ti)(ti)砂土(tu)(tu)上(shang)。在(zai)施工(gong)过程中，为(wei)防(fang)止(zhi)人畜践踏和动植物的破坏，在(zai)坝坡面上(shang)设(she)置细砂、砂砾石(shi)垫层(ceng)(ceng)(ceng)、干砌三层(ceng)(ceng)(ceng)，厚度分别为(wei)0.2m、0.4m、0.3m。坝前土(tu)(tu)工(gong)膜(mo)(mo)(mo)铺筑细沙和砂土(tu)(tu)分别回填于下层(ceng)(ceng)(ceng)和上(shang)层(ceng)(ceng)(ceng)，膜(mo)(mo)(mo)料厚度分别为(wei)0.1m、0.4m，膜(mo)(mo)(mo)料与(yu)保护层(ceng)(ceng)(ceng)及(ji)膜(mo)(mo)(mo)料与(yu)坝体(ti)(ti)之(zhi)间的摩(mo)擦：水位线以(yi)上(shang)0.5m处设(she)置抗滑槽(cao)，以(yi)增大(da)摩(mo)擦力，其尺寸(cun)为(wei)深1.0m，底宽(kuan)0.6m，边坡为(wei)1:0.5。
库区输水洞建筑物与复(fu)(fu)合土(tu)工(gong)膜防渗斜墙(qiang)的(de)连接(jie)(jie)应(ying)具有伸(shen)缩性(xing)，牢固、严密。导流(liu)墙(qiang)为直(zhi)立(li)墙(qiang)，先在砼表面(mian)隔20cm处安装膨胀螺栓(shuan)(shuan)连接(jie)(jie)，沿接(jie)(jie)缝长度装一条5mm宽10cm的(de)橡皮(pi)，再将复(fu)(fu)合土(tu)工(gong)膜折叠3层(ceng)(ceng)打眼(yan)，再用膨胀螺栓(shuan)(shuan)将复(fu)(fu)合土(tu)工(gong)膜固定在钢压条上。为了防止压条和(he)螺栓(shuan)(shuan)锈(xiu)蚀，必须在钢板压条和(he)螺栓(shuan)(shuan)上刷3层(ceng)(ceng)锈(xiu)蚀。
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