悬挂式止水帷幕基坑渗流模型的简化

Analysis for simplifying the foundation seepage model on the pensile curtain

为考虑隔水层之上悬挂止水帷幕对基坑渗流的影响,基于共形映射理论,建立了基坑坑底以下有效深度范围内无相对隔水层悬挂式止水帷幕基坑渗流的对称和非对称两种数学模型,推导在均质、各向同性、符合达西定律土体基坑渗流的单宽涌水量表达式。先对比对称和非对称两种模型,验证非对称模型等效对称模型的合理性。随后以云南某基坑为例,将等效后的对称模型的计算结果与实际渗流量进行比较,以此验证模型的有效性。结果表明,在工程允许范围内可将复杂的非对称模型等效为对称模型进行计算,而且推导出的两种模型是有效的,计算结果比较接近实际渗流量。

In order to investigate and confirm whether the suspended impervious curtain at above the aquifuge can likely affect the foundation pit seepage,this paper has established a foundation pit seepage model based on the conformal mapping theory. As is known,the so-called seepage model is usually oriented to study the foundation pit in which there is no relative aquifuge in its effective depth range,and the curtain to be used in this paper should be categorized into the pensile one. In this paper,merely two foundation pit seepage models are discussed,they are symmetric and asymmetric ones. According to the above two different models,we have deduced two different kinds of representative expressions of the foundation pit seepage per unit width,which can generally be used to the homogeneous and isotropic soil in accordance with Darcy＇s theorem. And then,this article has made a comparison between the different situations of the pit seepage according to the changing depth of the embedded curtains both in the sphere of the symmetrical model and the asymmetrical one,though there does not exist a certain relative aquifuge in effective depth under the pit bottom of the said curtains here in the above two models. Through comparison,this paper has verified the rational effective equality between the equivalent asymmetric model and the symmetric one. Thus,it has taken the foundation pit in seepage Yunnan as a case study sample,and compared the calculated results of the equivalent symmetrical model with the actual seepage flux,proving the validity and reliability of the aforementioned models. All the above studies and tests can show a conclusion that,the symmetric model and asymmetric model are both effective,whose calculation results have been testified basically close to the actual seepage status-in-situ. In addition,per unit width of the foundation pit seepage turns out to be proportional to the soil seepage coefficient. And,for the symmetrical model,the foundation pit seepage per unit width proves also to be proportional to the head difference between the inside and outside foundation pits. Therefore,the complicated asymmetrical model can also be applied to the calculation of the symmetrical model within a permission range of a certain engineering error.