[资料] 轻型井点降水施工方案 [复制链接]

1、工程简介ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
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？ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
2、降水方式方法及采取的措施ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
现场井点布置，采用的设备型号，技术参数等。ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
3、降水工作中应注意的事项ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
在降水施工过程中，技术、质量、安全、环保应注意的事项ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
4、计算书（附后）ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
本节主要讨论轻型井点降水有关计算ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
轻型井点降水计算ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
一、 总涌水量计算ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
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，ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
用下式计算公式： ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
     ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
（2H―s）s               ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
Q＝1.366K                     ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
lgR―lgx0                                  ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
2.单井井点涌水量q（m3/d）常按无压完整井，按下计算公式：ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
               （2H―s）sä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
q＝1.366Kä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
                         lgR―lgrä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
式中：K—土的渗透系数（m/d）；ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
H—含水层厚度（m）；ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
s—水的降低值（m）；ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
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• Kä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
r—井点的半径（m）；ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
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/πä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
F—基坑井点管所包围的平面面积（m2）；ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
π—圆周率，取3.1416；ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
二、井点管需要根数ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
井点管需要根数n可按下式计算：ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
       Qä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
n＝m       ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
qä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
式中 q＝65π•d•l 3√  Kä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
式中：ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
n—井点管根数；ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
m—考虑堵塞等因素的井点备用系数，一般取m＝1.1；ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
     q—单根井点管的出水量（m3/d）；ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
d—滤管直径（m）；ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
l—滤管长度（m）；ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
三、井点管平均间距ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
井点管平均间距D（m），可按下式计算：ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
        2（L＋B）ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
D＝              ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
n－1ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
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。ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
式中：L—矩形井点系统的长度（m）；ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
      B—矩形井点系统的宽度（m）；ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
四、例题ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
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。ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
解：（1）井点系统布置ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
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。ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
（2）基坑总涌水量计算ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
含水层厚度：H＝7.3－0.6＝6.7 mä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
降水深度：s＝4.1－0.6＋0.5＝4.0mä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
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：ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
x0＝√F/π ＝√（14＋0.8×2）（23＋0.8×2）／3.14 ＝11mä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
抽水影响半径：R＝1.95 s√H• K  ＝1.95×4√6.7×5 ＝45.1mä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
基坑总涌水量：     ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
（2H―s）s               ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
Q＝1.366K               ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
           lgR―lgx0 ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
                    （2×6.7―4）×4               ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
＝1.366×5               ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
               Lg45.1―lg11   ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
     ＝419 m3/dä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
（3）计算井点管数量和间距ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
单井出水量：ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
q＝65π•d•l 3√  K        ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
      ＝65 ×3.14 ×0.05×1.2 3√  5        ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
＝20.9 m3/dä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
井点管数量：ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
Q           419ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
n＝m       ＝1.1×      ＝22根ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
q        20.9ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
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。ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
井点管间距平均为：ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
2×（24.6＋15.6）           ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
D＝                 ＝2.77 m    取2.4mä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
30―1ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
        ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
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：ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
2×（24.6＋15.6）           ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
D＝                 ―2≈31.5根ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
2.4        ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ
用32根。ä1|º±µ±Üƒbbs.3c3t.comäÌ],ÙïÎnæ