如何确定合理的土工膜防渗层方案
许多土工(gong)(gong)膜(mo)试验和工(gong)(gong)程经验表明(ming)，采(cai)用达西定律时，一般(ban)要(yao)求土工(gong)(gong)膜(mo)的渗透系数满(man)足抗渗要(yao)求。高达10﹣~10﹣15m/s。在(zai)工(gong)(gong)程实(shi)践中(zhong)，渗透系数k<10-10m/s的粘土常被认(ren)为是(shi)防(fang)渗材料，也可以(yi)推(tui)断土工(gong)(gong)膜(mo)也是(shi)防(fang)渗材料。但(dan)实(shi)际上，工(gong)(gong)程上常用的防(fang)渗土工(gong)(gong)膜(mo)厚度远小于粘度。
土壤防渗体(ti)，因此在相同水(shui)头差的作用下，土工(gong)(gong)膜的水(shui)力(li)梯(ti)度远大于粘土防渗体(ti)。相对。同时，土工(gong)(gong)膜施工(gong)(gong)过程中或多(duo)或少(shao)会出现(xian)各种类型的土工(gong)(gong)膜缺陷，如土工(gong)(gong)膜接缝焊接的现(xian)状。
假粘接造成的(de)(de)(de)一定长度的(de)(de)(de)窄间隙缺陷，施(shi)工(gong)(gong)(gong)机械工(gong)(gong)(gong)具造成的(de)(de)(de)土(tu)(tu)工(gong)(gong)(gong)膜(mo)(mo)穿刺现象(xiang)。因此(ci)，在整(zheng)个(ge)水库中(zhong)选择(ze)土(tu)(tu)工(gong)(gong)(gong)膜(mo)(mo)防(fang)渗(shen)(shen)水库的(de)(de)(de)防(fang)渗(shen)(shen)层(ceng)(ceng)(ceng)时，应根据不同类型土(tu)(tu)工(gong)(gong)(gong)膜(mo)(mo)防(fang)渗(shen)(shen)层(ceng)(ceng)(ceng)的(de)(de)(de)渗(shen)(shen)透性(xing)引起(qi)的(de)(de)(de)渗(shen)(shen)漏量和施(shi)工(gong)(gong)(gong)引起(qi)的(de)(de)(de)缺陷渗(shen)(shen)漏量来确定土(tu)(tu)工(gong)(gong)(gong)膜(mo)(mo)防(fang)渗(shen)(shen)层(ceng)(ceng)(ceng)的(de)(de)(de)方(fang)(fang)案(an)。整(zheng)个(ge)水库常(chang)用(yong)的(de)(de)(de)土(tu)(tu)工(gong)(gong)(gong)膜(mo)(mo)防(fang)渗(shen)(shen)层(ceng)(ceng)(ceng)一般包括单层(ceng)(ceng)(ceng)土(tu)(tu)工(gong)(gong)(gong)膜(mo)(mo)防(fang)渗(shen)(shen)层(ceng)(ceng)(ceng)和土(tu)(tu)工(gong)(gong)(gong)膜(mo)(mo)复合防(fang)渗(shen)(shen)层(ceng)(ceng)(ceng)，土(tu)(tu)工(gong)(gong)(gong)膜(mo)(mo)下铺(pu)设低渗(shen)(shen)透土(tu)(tu)层(ceng)(ceng)(ceng)。本工(gong)(gong)(gong)程采用(yong)本土(tu)(tu)工(gong)(gong)(gong)膜(mo)(mo)防(fang)渗(shen)(shen)层(ceng)(ceng)(ceng)方(fang)(fang)案(an)进行技术(shu)经(jing)济比较，确定合理(li)的(de)(de)(de)土(tu)(tu)工(gong)(gong)(gong)膜(mo)(mo)防(fang)渗(shen)(shen)层(ceng)(ceng)(ceng)方(fang)(fang)案(an)。
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