滤料及地层对管廊基坑降水井效果影响研究

Influence of filter materials and formation on effect of drainage well in pipe gallery foundation pit

为了研究综合管廊基坑中降水井效果与滤料和地层的关系,以实际工程为依托,在不同地层区域改变降水井的滤料粒径,记录降水井的出水量、含砂量和周边地下水位变化,分析滤料与地层对降水井降水效果的影响,并通过试验选择最优的滤料形状和粒径。结果表明:砾砂地层中,5~10 mm粒径降水井的出水量最大,含砂量最小;圆砾地层中,10~20 mm粒径降水井的出水量最大,含砂量差别不大;以粒径相同的圆砾和角砾作为滤料时,降水井的出水量差别不大,在水流、施工扰动等作用下,角砾会破坏滤网,降低其过滤能力,导致含砂量较大,这种现象在砾砂地层中更明显;降水井滤料粒径需根据周边地层确定,若上覆地层含砂量大,滤料的粒径不宜过大,且形状应较圆润。

In order to study the relationship between the effect of drainage wells in the foundation pit of the comprehensive pipe gallery and the filter material and formation,based on actual engineering,the filter material particle size of the drainage wells was changed in different strata areas,and the water output,sand content,and surrounding groundwater level changes of the drainage wells were recorded.The influence of the filter material and formation on the dewatering effect of the well was analyzed,and the experiment was conducted to select the optimal shape and particle size of the filter material.The results showed that in gravel sand formations,the water output of drainage well with 5~10 mm particle size filter materials was the highest and the sand content was the lowest.In the round gravel formation,the water output of drainage well with 10~20 mm particle size was the highest with no signifficant difference of sand content.When using round gravel and angular gravel with the same particle size as the filter material,there was not much difference in the water output of the well.Under the action of water flow,construction disturbance,etc.,angular gravel will damage the filter screen,reduce its filtration capacity,and lead to a higher sand content.This phenomenon was more pronounced in gravel sand formations.The particle size of the filter material in the well should be determined according to the surrounding formation.If the overlying formation have a high sand content,the particle size of the filter material should not be too large and the shape should be relatively round.