单层土工膜防渗层的缺陷渗漏量的影响相当明显

土工膜通常被认为是非(fei)(fei)渗(shen)(shen)透(tou)(tou)型防渗(shen)(shen)材料(liao)，因此(ci)，土(tu)(tu)工(gong)(gong)(gong)膜(mo)(mo)(mo)(mo)也(ye)可作为非(fei)(fei)渗(shen)(shen)透(tou)(tou)性防渗(shen)(shen)材料(liao)，但事实(shi)上，工(gong)(gong)(gong)程(cheng)中常用的(de)防渗(shen)(shen)土(tu)(tu)工(gong)(gong)(gong)膜(mo)(mo)(mo)(mo)厚(hou)度(du)却远(yuan)小于粘土(tu)(tu)防渗(shen)(shen)体(ti)，因此(ci)，同一水头差时(shi)，土(tu)(tu)工(gong)(gong)(gong)膜(mo)(mo)(mo)(mo)的(de)水力梯度(du)比(bi)粘土(tu)(tu)防渗(shen)(shen)体(ti)大(da)得多，土(tu)(tu)工(gong)(gong)(gong)膜(mo)(mo)(mo)(mo)的(de)非(fei)(fei)渗(shen)(shen)透(tou)(tou)性实(shi)际上是相对(dui)的(de)。与此(ci)同时(shi)，土(tu)(tu)工(gong)(gong)(gong)膜(mo)(mo)(mo)(mo)施工(gong)(gong)(gong)过(guo)程(cheng)中或多或少都会出现各种(zhong)土(tu)(tu)工(gong)(gong)(gong)膜(mo)(mo)(mo)(mo)缺陷，如(ru)(ru)土(tu)(tu)工(gong)(gong)(gong)膜(mo)(mo)(mo)(mo)接缝焊接时(shi)产生的(de)具有(you)一定长度(du)的(de)窄缝缺陷，如(ru)(ru)土(tu)(tu)工(gong)(gong)(gong)膜(mo)(mo)(mo)(mo)接缝处出现局(ju)部粘结不实(shi)等(deng)，也(ye)有(you)施工(gong)(gong)(gong)机械及(ji)工(gong)(gong)(gong)具等(deng)。

对全(quan)库土(tu)(tu)工(gong)(gong)膜(mo)(mo)防(fang)(fang)渗(shen)(shen)(shen)水库进行(xing)防(fang)(fang)渗(shen)(shen)(shen)层(ceng)(ceng)选(xuan)型，应重点考虑不同类型土(tu)(tu)工(gong)(gong)膜(mo)(mo)防(fang)(fang)渗(shen)(shen)(shen)层(ceng)(ceng)所产生(sheng)的(de)渗(shen)(shen)(shen)漏量(liang)及(ji)施工(gong)(gong)过程中(zhong)所产生(sheng)的(de)缺(que)陷(xian)，常用全(quan)库式全(quan)库防(fang)(fang)渗(shen)(shen)(shen)水库土(tu)(tu)工(gong)(gong)膜(mo)(mo)防(fang)(fang)渗(shen)(shen)(shen)层(ceng)(ceng)，一般为单层(ceng)(ceng)土(tu)(tu)工(gong)(gong)膜(mo)(mo)防(fang)(fang)渗(shen)(shen)(shen)层(ceng)(ceng)，土(tu)(tu)工(gong)(gong)膜(mo)(mo)下(xia)铺(pu)一层(ceng)(ceng)低(di)渗(shen)(shen)(shen)透土(tu)(tu)，土(tu)(tu)工(gong)(gong)膜(mo)(mo)下(xia)铺(pu)一层(ceng)(ceng)低(di)渗(shen)(shen)(shen)透层(ceng)(ceng)，本土(tu)(tu)工(gong)(gong)膜(mo)(mo)防(fang)(fang)渗(shen)(shen)(shen)层(ceng)(ceng)方案是(shi)在工(gong)(gong)程中(zhong)采用的(de)技术经济比较，确(que)定土(tu)(tu)工(gong)(gong)膜(mo)(mo)防(fang)(fang)渗(shen)(shen)(shen)层(ceng)(ceng)的(de)合理(li)方案。

库区(qu)土(tu)(tu)工膜单(dan)层(ceng)防(fang)渗(shen)层(ceng)的缺陷(xian)渗(shen)出量受(shou)缺陷(xian)尺寸的影(ying)响比较(jiao)明显，对土(tu)(tu)工膜复(fu)合防(fang)渗(shen)层(ceng)影(ying)响不(bu)大(da)，从降低渗(shen)透率(lv)角度考(kao)虑，土(tu)(tu)工膜复(fu)合防(fang)渗(shen)层(ceng)的防(fang)渗(shen)效果明显好于单(dan)一(yi)土(tu)(tu)工膜防(fang)渗(shen)层(ceng)。

当土(tu)工膜(mo)(mo)(mo)膜(mo)(mo)(mo)上(shang)水头(tou)增加时(shi)，其渗(shen)(shen)(shen)流量也随(sui)之增大，两者基本呈线性关系，但对(dui)土(tu)工膜(mo)(mo)(mo)复合防渗(shen)(shen)(shen)层(ceng)而言(yan)，低(di)渗(shen)(shen)(shen)透(tou)(tou)性土(tu)层(ceng)厚(hou)(hou)度对(dui)缺陷(xian)渗(shen)(shen)(shen)透(tou)(tou)量影(ying)响不(bu)大，说明(ming)不(bu)应过厚(hou)(hou)，但低(di)渗(shen)(shen)(shen)透(tou)(tou)性土(tu)不(bu)应过厚(hou)(hou)，而低(di)渗(shen)(shen)(shen)透(tou)(tou)率则受低(di)渗(shen)(shen)(shen)透(tou)(tou)率影(ying)响较大。所(suo)以在选择膜(mo)(mo)(mo)下低(di)渗(shen)(shen)(shen)透(tou)(tou)性土(tu)层(ceng)时(shi)，可选用厚(hou)(hou)度较薄、渗(shen)(shen)(shen)透(tou)(tou)系数小的(de)防渗(shen)(shen)(shen)土(tu)料(liao)。

施工水平、施工质量(liang)、土工膜(mo)与下土层接触(chu)状况(kuang)、土工膜(mo)缺陷的大(da)小、数(shu)量(liang)受施工水平、施工质量(liang)等(deng)因素(su)的影响，因此，精心施工是保证土工膜(mo)防(fang)渗性能发挥的重要(yao)基础和保障。