[资料] 轻型井点降水施工方案 [复制链接]

1、工程简介N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
着中重说明基础工程中的地质概况、地下水概况以及与降水有关的情况，即为什么要降水？N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
2、降水方式方法及采取的措施N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
现场井点布置，采用的设备型号，技术参数等。N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
3、降水工作中应注意的事项N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
在降水施工过程中，技术、质量、安全、环保应注意的事项N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
4、计算书（附后）N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
本节主要讨论轻型井点降水有关计算N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
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轻型井点降水计算N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
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一、 总涌水量计算N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
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1.基坑总涌水量Q（m3/d），即环形井点系统用水量，常按无压完整井井群，N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
用下式计算公式： N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
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（2H―s）s               N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
Q＝1.366K                     N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
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2.单井井点涌水量q（m3/d）常按无压完整井，按下计算公式：N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
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               （2H―s）sN¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
q＝1.366KN¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
                         lgR―lgrN¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
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式中：K—土的渗透系数（m/d）；N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
H—含水层厚度（m）；N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
s—水的降低值（m）；N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
R—抽水影响半径（m），由现场抽水试验确定，也可用下式计算：R＝1.95 s√H• KN¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
r—井点的半径（m）；N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
x0—基坑的假想半径（m，当矩形基坑长宽比小于5时，可化成假想半径x0的圆形井，按下式计算：x0＝√F/πN¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
F—基坑井点管所包围的平面面积（m2）；N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
π—圆周率，取3.1416；N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
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二、井点管需要根数N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
井点管需要根数n可按下式计算：N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
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n＝m       N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
qN¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
式中 q＝65π•d•l 3√  KN¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
式中：N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
n—井点管根数；N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
m—考虑堵塞等因素的井点备用系数，一般取m＝1.1；N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
     q—单根井点管的出水量（m3/d）；N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
d—滤管直径（m）；N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
l—滤管长度（m）；N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
三、井点管平均间距N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
井点管平均间距D（m），可按下式计算：N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
        2（L＋B）N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
D＝              N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
n－1N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
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求出的D应大于15d，并应符合总管接头的间距（一般为80、120、160mm）要求。N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
式中：L—矩形井点系统的长度（m）；N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
      B—矩形井点系统的宽度（m）；N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
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四、例题N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
某工程基坑平面尺寸见图，基坑宽10m，长19m，深4.1m，挖土边坡1：0.5。地下水位－0.6m。根据地质勘察资料，该处地面下0.7m，为杂填土，此层下面有6.6m的细砂层，土的渗透系数K＝5m/d，再往下为不透水的粘土层。现采用轻型井点设备进行人工降低地下水位，机械开挖土方，试对该轻型井点系统进行计算。N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
解：（1）井点系统布置N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
该基坑顶部平面尺寸为14m×23m，布置环状井点，井点管离边坡为0.8m。要求降水深度s＝4.10－0.6＋0.5＝4.0m，因此，用一级轻型井点系统即可满足要求，总管和井点布置在同一水平面上。由井点系统布置处至下面一层不透水粘土层的深度为0.7＋6.6＝7.3m，设井点管长度为7.2m（井管长6m，滤管1.2m，直径0.05m），因此，滤管底距离不透水粘土层只差0.1m，可按无压完整井进行设计和计算。N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
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（2）基坑总涌水量计算N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
含水层厚度：H＝7.3－0.6＝6.7 mN¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
降水深度：s＝4.1－0.6＋0.5＝4.0mN¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
基坑假想半径：由于该基坑长宽比不大于5，所以可化简为一个假想半径为x0的圆井进行计算：N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
x0＝√F/π ＝√（14＋0.8×2）（23＋0.8×2）／3.14 ＝11mN¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
抽水影响半径：R＝1.95 s√H• K  ＝1.95×4√6.7×5 ＝45.1mN¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
基坑总涌水量：     N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
（2H―s）s               N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
Q＝1.366K               N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
           lgR―lgx0 N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
                    （2×6.7―4）×4               N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
＝1.366×5               N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
               Lg45.1―lg11   N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
     ＝419 m3/dN¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
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（3）计算井点管数量和间距N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
单井出水量：N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
q＝65π•d•l 3√  K        N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
      ＝65 ×3.14 ×0.05×1.2 3√  5        N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
＝20.9 m3/dN¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
井点管数量：N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
Q           419N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
n＝m       ＝1.1×      ＝22根N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
q        20.9N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
在基坑四角处井点管应加密，如考虑每个角加2根井管，采用的井点管数量为22＋8＝30根。N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
井点管间距平均为：N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
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2×（24.6＋15.6）           N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
D＝                 ＝2.77 m    取2.4mN¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
30―1N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
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井点管布置时，为让开机械挖土开行路线，宜布置成端部开口（即留3根井管数量距离），因此，实际需要井点管数量为：N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
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2×（24.6＋15.6）           N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
D＝                 ―2≈31.5根N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
2.4        N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó
用32根。N¦vf͐ʋbbs.3c3t.comßÈQ{W$yó