HDPE土工膜的工程特性
这种特性(xing)(xing)(xing)相(xiang)关(guan)的(de)指标(biao)主要包括材(cai)料的(de)防渗(shen)特性(xing)(xing)(xing)、摩擦(ca)特性(xing)(xing)(xing)、和耐久性(xing)(xing)(xing)等,其中最关(guan)键(jian)的(de)为防渗(shen)特性(xing)(xing)(xing)。
1)防渗特性
在(zai)工(gong)(gong)(gong)程(cheng)(cheng)施工(gong)(gong)(gong)过程(cheng)(cheng)中,土(tu)(tu)工(gong)(gong)(gong)膜(mo)的(de)主要(yao)(yao)目的(de)就(jiu)是为(wei)了防渗(shen)(shen)(shen)(shen)(shen)(shen)(shen),从其分子结构等理(li)论上分析可知,此种(zhong)材(cai)料是不(bu)透气(qi)的(de),但是进(jin)一(yi)步(bu)研究和(he)实践中发(fa)现,受施工(gong)(gong)(gong)工(gong)(gong)(gong)艺(yi)上种(zhong)种(zhong)原因的(de)影响,这(zhei)种(zhong)材(cai)料相(xiang)对不(bu)透水(shui)(shui)(shui)(shui)(shui),表(biao)现出一(yi)定(ding)的(de)透水(shui)(shui)(shui)(shui)(shui)性。如果沿(yan)用达西渗(shen)(shen)(shen)(shen)(shen)(shen)(shen)透定(ding)律进(jin)行(xing)检测,水(shui)(shui)(shui)(shui)(shui)利工(gong)(gong)(gong)程(cheng)(cheng)中不(bu)透水(shui)(shui)(shui)(shui)(shui)的(de)粘(zhan)土(tu)(tu)渗(shen)(shen)(shen)(shen)(shen)(shen)(shen)透系(xi)数为(wei)K<10ˉ¹ºCm/S,则不(bu)透水(shui)(shui)(shui)(shui)(shui)的(de)土(tu)(tu)工(gong)(gong)(gong)织布的(de)渗(shen)(shen)(shen)(shen)(shen)(shen)(shen)透系(xi)数应为(wei)K<10ˉ14cm/s,其原因是土(tu)(tu)工(gong)(gong)(gong)膜(mo)防渗(shen)(shen)(shen)(shen)(shen)(shen)(shen)体与粘(zhan)土(tu)(tu)防渗(shen)(shen)(shen)(shen)(shen)(shen)(shen)体相(xiang)比,厚度(du)(du)值要(yao)(yao)小,这(zhei)样(yang)在(zai)相(xiang)同的(de)水(shui)(shui)(shui)(shui)(shui)头差条件下(xia)(xia),土(tu)(tu)工(gong)(gong)(gong)膜(mo)防渗(shen)(shen)(shen)(shen)(shen)(shen)(shen)体的(de)水(shui)(shui)(shui)(shui)(shui)力梯(ti)度(du)(du)远大(da)于粘(zhan)土(tu)(tu)防渗(shen)(shen)(shen)(shen)(shen)(shen)(shen)体的(de)水(shui)(shui)(shui)(shui)(shui)力梯(ti)度(du)(du)。一(yi)般情况(kuang)下(xia)(xia),防渗(shen)(shen)(shen)(shen)(shen)(shen)(shen)材(cai)料渗(shen)(shen)(shen)(shen)(shen)(shen)(shen)透系(xi)数要(yao)(yao)求在(zai)(l0ˉ¹²cm/s~10-14cm/s)区间内,这(zhei)样(yang)土(tu)(tu)工(gong)(gong)(gong)膜(mo)满足以上要(yao)(yao)求,就(jiu)能满足其防渗(shen)(shen)(shen)(shen)(shen)(shen)(shen)要(yao)(yao)求。
2)摩擦特性
土工(gong)膜铺设在(zai)斜(xie)坡(po)上(shang)时(shi),其(qi)(qi)可以(yi)和其(qi)(qi)他材料产生明显(xian)的(de)摩擦,因而摩擦性(xing)(xing)能也是一个重要的(de)控(kong)制指标。可以(yi)在(zai)现场摩擦试验基础上(shang)确定出其(qi)(qi)摩擦性(xing)(xing)能,其(qi)(qi)中常用(yong)的(de)为类似于无(wu)粘性(xing)(xing)土休止(zhi)角的(de)拍板实验,这列试验中首(shou)先在(zai)平板上(shang)放(fang)上(shang)土工(gong)膜,堆放(fang)土等材料,不断(duan)地(di)抬高板的(de)一端,这样(yang)就可以(yi)测定出起(qi)初滑动时(shi)的(de)坡(po)角。
3)耐水(shui)压性能
土工膜属于土工膜防渗(shen)结(jie)构主体,其在(zai)(zai)工作过(guo)程中(zhong)会承受(shou)很高的(de)(de)水(shui)压(ya)(ya)力(li),而(er)(er)在(zai)(zai)一(yi)(yi)定(ding)(ding)的(de)(de)条件下,其可能会在(zai)(zai)颗粒孔隙处被(bei)水(shui)压(ya)(ya)压(ya)(ya)破(po)(po)而(er)(er)击(ji)穿。在(zai)(zai)实验测试过(guo)程中(zhong),需要(yao)在(zai)(zai)其两(liang)侧压(ya)(ya)力(li)水(shui)头达(da)到(dao)一(yi)(yi)定(ding)(ding)水(shui)平后,检(jian)测其破(po)(po)裂情(qing)(qing)况下的(de)(de)压(ya)(ya)力(li)。逐(zhu)级(ji)增加(jia)试样(yang)两(liang)侧水(shui)力(li)压(ya)(ya)养(yang),保持一(yi)(yi)定(ding)(ding)时间,在(zai)(zai)渗(shen)流(liu)量急速增加(jia)的(de)(de)情(qing)(qing)况下,可以判断出试样(yang)受(shou)到(dao)破(po)(po)坏,据此(ci)就可以确(que)定(ding)(ding)出相应的(de)(de)耐(nai)静水(shui)压(ya)(ya)值(zhi)。
4)耐(nai)久性
土工(gong)(gong)(gong)膜(mo)的耐久性(xing)(xing)在(zai)工(gong)(gong)(gong)程施(shi)工(gong)(gong)(gong)过程也是(shi)(shi)需要重(zhong)点考虑的,与此(ci)相关的因(yin)素主要是(shi)(shi)老化(hua)和(he)蠕(ru)变(bian)(bian)。影(ying)响土工(gong)(gong)(gong)膜(mo)的老化(hua)[471的因(yin)素多样,主要是(shi)(shi)光、热、应力和(he)化(hua)学物质等,在(zai)这些条(tiao)件影(ying)响下,土工(gong)(gong)(gong)膜(mo)耐久性(xing)(xing)会出现(xian)明显的变(bian)(bian)化(hua)。而蠕(ru)变(bian)(bian)是(shi)(shi)指不(bu)改变(bian)(bian)受力大小的情况下,变(bian)(bian)形和(he)时间(jian)之间(jian)关系呈正比增长变(bian)(bian)化(hua)。此(ci)指标大小和(he)原(yuan)材(cai)料的性(xing)(xing)质和(he)生(sheng)产(chan)工(gong)(gong)(gong)艺存在(zai)一定的相关性(xing)(xing)。
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