含浅层强透水层堤基上覆砂层管涌破坏试验研究.docVIP

含浅层强透水层堤基上覆砂层管涌破坏试验研究 　　摘要： 　　堤基中往往存在局部浅层强透水层并形成渗流优先通道，该通道不能大幅度削减流体的水头势能，易引起堤基管涌破坏，此类堤基管涌破坏机理的研究尚不明朗，仍需进一步研究。采用砂槽试验模拟堤基渗流，试验中通过抬升水箱水位，观察砂土中细颗粒流失现象，并分析渗流量、渗透坡降、测压管水头、砂土颗粒级配、锥头阻力、沉降量等关键参数。试验结果表明，水箱水位增大至48 cm，浅层强透水层上覆砂层被“击穿”发生管涌破坏，管涌破坏分为稳定渗流阶段、细颗粒流失阶段（0.05d≤0.075粒级砂土流失）、较细颗粒流失阶段（0.075d≤0.1粒级砂土流失）、管涌破坏扩大阶段（0.1d≤0.25粒级砂土流失）。管涌破坏过程中，细颗粒砂土流失，锥头阻力降低，砂土层发生沉降，且较细颗粒流失阶段的沉降较为突出。细颗粒砂土流失导致砂土层孔隙率和渗透系数上升，渗流量和渗透坡降随之增大。 　　关键词：堤基；强透水层；管涌；砂土；锥头阻力；沉降 　　中图分类号：TU443 　　文献标志码：A文章编号2018 　　Abstract： 　　There is shallow and strong permeable stratum in dike foundation， which can form a prior seepage channel， and fluid head potential isnt weakened by this channel， it is easy to cause dike foundation piping failure， and the study of failure mechanism of dike foundation piping is not clear， it still needs further study. Sand tank test is used to simulate embankment foundation influent in this paper， water block stage is drived up in test， and observing the phenomenon of fine particle loss in sand， and the key parameters of seepage discharge， seepage gradient， piezometric tube head， grain composition of sand， cone resistance and settlement are analysed. The test results show that sand on the shallow and strong permeable stratum occur piping failure when water block stage increases to 48 cm. Piping failure is divided into steady seepage stage， internal erosion of fine particles stage， internal erosion of relative fine particles stage and piping failure expansion stage. The internal erosion of fine particles in process of piping failure， and cone resistance has reduced， sand has settled， and settlement heavily focus on internal erosion of relative fine particles stage. The porosity and permeability coefficient of sand， seepage discharge and seepage gradient increase when fine particle loss. This reseach results can offer theory reference for similar projects. 　　Keywords： 　　dike foundation； strong permeable stratum； piping； sand； cone resistance； settlement 　　管涌是指地基土体在渗流作用