非饱和砾石土心墙料渗透变形的试验研究

Experimental study on seepage deformation of unsaturated gravel clayey soils

开展了砾石土心墙料的渗透变形试验,对比了砾石土是否饱和、水力坡降提升模式等对抗渗能力的影响,重点研究了土样不预先饱和、直接施加高水力坡降时的渗透变形特性,同时对比了小于5 mm的细粒含量、是否布置反滤等的影响。饱和状态对砾石土高水力坡降作用下的抗渗能力影响较大,预先饱和的砾石土能够承担较大坡降而不发生管涌破坏,而不预先饱和的砾石土则可能发生管涌破坏。在承受单级快速施加的较大坡降时,不预先饱和的砾石土均发生渗透破坏。施加的坡降越大,则细颗粒开始被带出的时间和破坏时间越短。细粒含量降低会导致不预先饱和土样抗渗坡降的下降。当砾石土干密度、初始含水量相等时,破坏水力坡降随细粒含量下降而减小。有反滤保护后砾石土抗管涌破坏能力明显提升,但低细粒含量的土料仍可能发生管涌破坏。

In this study,experimental tests on seepage deformation of unsaturated gravel clayey soils are carried out,and the influence of soil saturation conditions and hydraulic gradient loading on the capability of wide-graded gravel clayey soil against seepage failure is studied.Results show that the saturation condition has a great influence on the capability against seepage failure.A pre-saturated soil sample can bear a larger hydraulic gradient before piping failure,while the failure occurs at a certain hydraulic gradient when the sample is not pre-saturated.All the unsaturated gravel soil samples fail when a relatively large hydraulic gradient is applied in a single stage.An increase in hydraulic gradient decreases the elapsed time at which fine particles begin to be brought out and the elapsed time at piping failure.Decreasing fines content also leads to a decline in the sample’s resistance to piping failure.For gravel soils with the same dry density and water content,the failure hydraulic gradient decreases with the decreasing fines content.The anti-piping capability of gravel soil is obviously improved by adding a filter protection,but the soil,even so protected,may still fail due to piping if its fines content is low.