无粘性土中管涌的毛管模型及其应用

通过对骨架孔隙中细颗粒的受力分析。建立了描述无粘性土中管涌发生、发展的毛管模型。利用该模型。将细颗粒的流失量、土体渗透性和颗粒起动的水力条件三者联系起来。得到了可动颗粒起动的临界水头梯度公式和考虑细颗粒流失的渗透系数公式。通过管涌试验校验证实了有关公式的有效性。计算结果表明，管涌过程中的渗透性显著地受细颗粒流失的影响。而且当有细颗粒流失后。级配不连续的管涌型土比级配连续的管涌型土更易发展成管涌破坏。

CAPILLARY-TUBE MODEL FOR PIPING IN NONCOHESIVE SOILS AND ITS APPLICATION

Based on the analysis of the forces acting on the fine grains in the skeleton pores,a capillary-tube model is introduced to characterize the development of piping in noncohesive soils. With the model,the relationship among the washout of fines,the permeability of soils and the hydraulic condition of incipient motion of grains is investigated,and a set of formulae of the critical hydraulic gradient for the incipient motion of movable grains and the permeability coefficient considering the washout of fines are obtained. The application of the formulae to some examples of piping tests gives reasonable results in comparison with the experimental observations. The theoretical results illustrate that the washout of the fine grains has an important influence on the permeability of noncohesive soils. In addition,it is proved that piping failure takes place more easily in the piping-typed soils with a bimodal grain-size-distribution than in the soils with a unimodal grain-size-distribution after some fine grains are washed out.