虹吸排水法处理软土地基的水位与沉降计算模型

Calculation Model for Water Level and Settlement of Soft Foundation Treated by Siphon Drainage

软土具有渗透性差、承载力低等特性,软土地基的处理一直是岩土工程中的一大难题。利用虹吸免动力排水的特点,可将虹吸排水法应用于软土地基处理中,达到改善土体性质的目的。本文针对虹吸排水法独特的定降深降水模式,先基于离散化的Theis井流模型以及非线性的分层总和法,构建了以孔隙率为核心、渗透系数与压缩模量随固结情况改变的水位与沉降动态计算模型,并与数值模拟结果对比,然后从土体渗透系数、排水板间距以及场地大小3个方面对虹吸排水法处理软土地基的效果进行了分析。结果表明:数值模拟结果验证了计算模型的可靠性,对于浙江沿海不同渗透系数的土体,虹吸排水法均可起到良好的排水固结作用;调整排水板间距可对排水固结时间以及地下水位线起到显著控制作用;排水带来的附加应力随着场地面积的增大向土体深处延伸,对于面积50 m×50 m大小的场地,有效影响深度可达到地表以下27.31 m,远远超出虹吸扬程的极限。在实际的大面积软土地基处理中,虹吸排水法可发挥更好的作用。

Soft soil has the characteristics of poor permeability and low bearing capacity.The treatment of soft soil foundation is always a major problem in geotechnical engineering.With the characteristics of free power in drainage,the siphon drainage method can be applied in soft ground the treatment to improve the properties of the soil.Based on the discretized Theis well flow model and the nonlinear layered summation method of settlement,this paper constructs a water level and settlement calculation model considering the changes in permeability coefficient and compressive modulus by settlement with porosity as the core for the unique fixed-deck precipitation model of the siphon drainage method.The effect of the siphon drainage method in soft foundation treatment is analyzed from the aspects of soil permeability coefficient,drainage board spacing,and site size.The results mainly focus on the following three aspects.First,the calculation outcomes are compared with numerical simulation results and the reliability of the calculation model is verified.And the siphon drainage method can perform well in drainage and consolidation for soils of different permeability coefficients in Zhejiang coastal areas.Second,adjusting the spacing of drainage plates can significantly control the drainage consolidation time and the groundwater level.Third,the additional stress caused by drainage will extend into the soil as the site area increases,and for a 50 m×50 m site,the effective influence depth can reach 27.31 m below the surface,which is far beyond the limit of siphon lift.Therefore,the siphon drainage method will get a better effect in practical large-area soft soil foundation treatment.