穿江管道对堤防渗透安全的影响研究

Study on the Influence of River-Crossing Pipeline to the Permeability Safety of Embankment

穿江管道从堤防下方穿越时改变了渗流场,可能影响两岸堤防的安全。采用数值模拟方法,重点分析在不同渗透系数下穿江管道埋深和穿越位置对堤防渗透安全的影响,首先采用ANSYS软件建立有限元模型,然后通过有限单元法计算渗流场,并根据临界水力坡降判断堤防的渗流稳定性。数值模拟结果表明:管道的穿越位置与地层渗透系数对堤防地基最大渗透坡降影响显著;穿越位置距堤脚越远、地层的渗透系数越小,最大渗透坡降就越小;穿越位置最好布置在堤防背水侧距堤脚70 m以外;管道的埋深对渗透坡降影响并不明显。最大渗透坡降易出现在渗透系数差别较大的两种材料接触的地方,如管道出(入)土点与地层相交处、堤防堤脚与地基交界处,这些部位需重点进行防渗处理。

The original seepage field of the embankment will be changed when the river-crossing pipeline crosses the embankment,which may affect the safety of river embankment. In this paper,the method of numerical simulation was adopted to research this issue. The embankment seepage safety was emphatically analyzed which affected by the burial depth of the river-crossing pipeline and the crossing position of pipeline under different permeability coefficients. Firstly,the finite element model was created by ANSYS and then the finite element method was used to calculate the seepage field. Then,the seepage stability of embankment could be judged according to the critical hydraulic gradient. The results of numerical simulation indicate that the maximum hydraulic gradient of the embankment will be significantly affected by two factors of the position of river-crossing pipeline and the permeability coefficient of the stratum. The further the position of river-crossing pipeline is,the smaller the permeability coefficient of the stratum and the smaller the maximum seepage gradient will be. The better position of the river-crossing pipeline is 70 meters away from the landside of embankment and the burial depth of the pipeline has no remarkable influence to the seepage gradient. In practical engineering,the maximum seepage gradient is prone to appear in the joint area of two kinds of materials with different permeability coefficients,such as the intersection between the unearthed point of pipeline and stratum,and the junction of embankment toe and foundation,so the seepage control measures must be taken accordingly.