轻型井点降水方案.doc

目录 一、工程概况 ···································································2 二、编制依据· ···································································2 三、降水方案选择·······························································2 四、井点降水相关计算·························································3 五、主要降水设备·······························································6 六、施工工期·····································································7 七、井点施工方法·······························································7 八、质量标准及质量保证措施················································8 九、危险点分析································································10 十、安全生产及文明施工措施···············································10 十一、环保措施································································11 一、 工程概况 本期设计为2×600MW亚临界汽轮发电机组。 工程地质情况：本工程持力层采用③圆砾层做持力层，③圆砾，层顶一般埋深3.0m ~4.5m，一般厚度6.5m ~9.5m。④细中砂层，层顶埋深一般为10.0m ~13.0m。一般厚度5.0m~7.0m。⑤圆砾层分布于④层之下。层顶一般埋深15.0m ~18.0m。⑥粘土（残积土），褐色，稍湿，坚硬，覆于凝灰岩之上。最大厚度大于6.8m。 二、编制依据 《火电施工质量检验及评定标准》 《电力建设施工及验收技术规范》 《建筑施工计算手册》 临时土方开挖图纸 三、降水方案选择 该项目地处伊敏河畔，属砂砾地质结构，渗透系数为150m/天，容水量大，受降水影响地下水位波动变幅1-2m 。枯水期在-6m左右。而本工程大部分建筑物埋深在-6m，处于临界状态，丰水期就无法施工，本工程采取的措施是：采用明沟、集水井的方式进行作业层表面水的降水。在枯水期柱、基础底脚施工完、回填完，防止丰水期淹没，以减少降水施工的降水费用。基础埋深超过-6m的，采用局部井点降水。 本工程主厂房基础底标高为-5.0m，不须采用井点降水，而循环水泵坑及汽轮机基础底标高为-7.5m，可采用轻型井点降水。基础平面基底长度约为50m，宽度约为36m。基础埋深为见施工图，地面持力层为圆砾层，井点降水可以避免大量涌水、冒泥、翻浆，而且在砂砾地层中开挖基坑时，可防止流砂现象发生，渗流向下改善土的性质，使基底土质更加密实，结合本工程基础施工主要在枯水期期间，周期较长的特点，采用轻型井点降水法，沿建筑物环状布置进行人工降水。同时基坑二角设集水箱配合4台QY-3.5型潜水泵排除明水的方法。 四、井点降水相关计算 1、井点管的埋设深度 H≥H1＋h＋iL＋l 式中 H——井点管的埋设深度(m) H1——井点埋设面至基坑底面距离(m) 取3.0m h—— 基坑中央最深挖掘面至降水曲线点的安全距离(m)取1.0m L—— 井点管中心至基坑中心的短边距离(m) 取27 i—— 降水曲线坡度 取1/10 l—— 滤管长度(m)取1.2 H≥3.0＋1.0＋27×1/10＋1.2=7.9m 取8m 2、涌水量计算 Q=1.366K Q——井点系统总涌水量（m3/d） K——渗透系数（m/d）取150 H——含水层厚度（m）计算暂取11m R——抽水影响半径（m）计算取91 S——水位降低值（m）取1.2，地下水位取6.8m