Pumice sand of volcanic origin contains a high fraction of non-plastic fines (>40 % for Satozuka pumice sand in Sapporo, Japan). Suffusion in such soil can wash away a portion of the fine particles and alter the soil microstructure. The moisture content and degree of compaction can affect the suffusion characteristics of soil deposits, however their effect has not yet been evaluated. Future construction sites in growing Sapporo City, consisting of pumice sand, will require a high degree of compaction (over 90 % and preferably over 95 %) as this sand is prone to suffusion in spite of its dense state. The aim of this study is to assess the impact of suffusion on densely compacted pumice sand with a high proportion of fines, based on its mechanical properties, with an emphasis on shear strength and dilatancy. Firstly, the suffusion characteristics of Satozuka pumice sand were evaluated. Subsequently, undrained triaxial tests ($\overline{\mathrm{C}\mathrm{U}}$ tests) under monotonic loading were conducted on high-density specimens, with suffusion and without suffusion, to study the impact of suffusion. It is seen in the results that the hydraulic conductivity, shear strength, stress paths, and dilatancy are all noticeably affected by suffusion. The specimens with suffusion exhibit an increase in residual shear strength and maximum deviator stress under shearing and experience an earlier occurrence of phase transformation from contraction to dilation during shearing. This tendency implies that suffusion has no significant negative impact on the deterioration of earth fill made from pumice sand and non-plastic fines, and that it persists at degrees of compaction between 80 % and 100 %.

火山来源的浮石砂含有高比例的非塑料细粉（日本札幌的 Satozuka 浮石砂>40%）。这种土壤中的弥漫可以冲走一部分细颗粒并改变土壤的微观结构。含水量和压实程度会影响土壤沉积物的漫射特性，但其影响尚未得到评估。札幌市未来的建筑工地由浮石砂组成，需要高度压实（超过 90%，最好超过 95%），因为尽管这种沙子很致密，但很容易发生漫溢。本研究的目的是根据其机械性能，重点评估剪切强度和剪胀性，评估弥漫对细粉比例较高的致密压实浮石砂的影响。首先，对里冢浮石砂的扩散特性进行了评价。随后，不排水三轴试验（$\stackrel{￣}{\mathrm{C}\mathrm{U}}$对高密度试件进行单调加载下的漫射和无漫射试验，研究漫射的影响。从结果中可以看出，水力传导率、剪切强度、应力路径和剪胀性均受到漫射的显着影响。具有弥漫性的样本在剪切下表现出残余剪切强度和最大偏应力的增加，并且在剪切过程中经历从收缩到扩张的相变较早发生。这种趋势意味着，漫射对由浮石砂和非塑性细粉制成的填土的恶化没有显着的负面影响，并且它在压实度在 80% 到 100% 之间时持续存在。