围堰堰体防渗采用复合土工膜心墙形式节省投资较为重要

本工(gong)(gong)(gong)(gong)程中(zhong)投标阶(jie)(jie)段围(wei)(wei)堰(yan)堰(yan)体防渗(shen)采(cai)用复合(he)土工(gong)(gong)(gong)(gong)膜(mo)心墙(qiang)形式(shi)，主要考虑围(wei)(wei)堰(yan)作(zuo)为临(lin)时挡水结构，在保(bao)证基坑安全的情(qing)况下，节省投资(zi)较(jiao)(jiao)为重要，而采(cai)用心墙(qiang)土工(gong)(gong)(gong)(gong)膜(mo)用量(liang)少(shao)，防渗(shen)效果好。但(dan)施工(gong)(gong)(gong)(gong)中(zhong)复合(he)土工(gong)(gong)(gong)(gong)膜(mo)、过渡料(liao)、堆石(shi)料(liao)需同步分层填(tian)筑，施工(gong)(gong)(gong)(gong)难度和干扰大，施工(gong)(gong)(gong)(gong)过程中(zhong)质量(liang)监(jian)管尤其严(yan)格(ge)，施工(gong)(gong)(gong)(gong)完成后成品保(bao)护同样重要，对(dui)工(gong)(gong)(gong)(gong)期(qi)宽松项目较(jiao)(jiao)适合(he)。因此，在投标阶(jie)(jie)段，工(gong)(gong)(gong)(gong)期(qi)固定，方案(an)确定较(jiao)(jiao)容易。

实(shi)际施工(gong)(gong)过(guo)程(cheng)(cheng)中，由于(yu)各种原因，本(ben)(ben)工(gong)(gong)程(cheng)(cheng)截流工(gong)(gong)期(qi)推迟1个(ge)月，而(er)度汛节点工(gong)(gong)期(qi)未发(fa)生改变，这(zhei)就要求压(ya)缩混凝(ning)土(tu)防(fang)(fang)渗(shen)墙工(gong)(gong)期(qi)或(huo)围堰(yan)(yan)填筑(zhu)(zhu)工(gong)(gong)期(qi)。实(shi)际上，本(ben)(ben)工(gong)(gong)程(cheng)(cheng)有(you)三个(ge)不(bu)(bu)利(li)因素，造成(cheng)工(gong)(gong)期(qi)不(bu)(bu)可(ke)能压(ya)缩，一(yi)是(shi)必(bi)须在围堰(yan)(yan)堰(yan)(yan)体内保(bao)证(zheng)通行道路，确保(bao)相邻标段车辆大规模出渣，对(dui)(dui)填筑(zhu)(zhu)围堰(yan)(yan)干(gan)扰极大，如(ru)采用心(xin)墙形(xing)式，基(ji)本(ben)(ben)上无法施工(gong)(gong);二(er)是(shi)围堰(yan)(yan)填筑(zhu)(zhu)料位(wei)于(yu)堰(yan)(yan)体上游，堰(yan)(yan)前通道始(shi)终保(bao)通，围堰(yan)(yan)最终成(cheng)形(xing)困难(nan)(nan);三是(shi)河(he)床地质条件十分(fen)(fen)复(fu)杂(za)，混凝(ning)土(tu)防(fang)(fang)渗(shen)墙施工(gong)(gong)成(cheng)槽困难(nan)(nan)，进(jin)(jin)度不(bu)(bu)可(ke)控(kong)。鉴于(yu)此，需要对(dui)(dui)方案进(jin)(jin)行重新审定，经多(duo)次专家会(hui)议研究(jiu)，采用复(fu)合土(tu)工(gong)(gong)膜斜墙防(fang)(fang)渗(shen)施工(gong)(gong)，可(ke)以做(zuo)到混凝(ning)土(tu)防(fang)(fang)渗(shen)墙和围堰(yan)(yan)填筑(zhu)(zhu)分(fen)(fen)开进(jin)(jin)行，有(you)利(li)于(yu)加快施工(gong)(gong)进(jin)(jin)度，在度汛节点工(gong)(gong)期(qi)前完成(cheng)围堰(yan)(yan)施工(gong)(gong)是(shi)可(ke)能的。但由于(yu)斜墙部位(wei)地质勘探资料不(bu)(bu)完整，如(ru)采用原设计(ji)指标可(ke)能会(hui)对(dui)(dui)围堰(yan)(yan)防(fang)(fang)渗(shen)效果产生一(yi)定影响。