For the French ancient rail track, owing to the effect of traffic loadings, an interlayer was naturally created due to the interpenetration of ballast grains and subgrade fine soil. Under the effect of rainfall/evaporation, the water content of interlayer soil can vary, affecting its dynamic properties such as resilient modulus and damping ratio. In order to investigate the effect of water content on the resilient modulus and the damping ratio of interlayer soil, a series of cyclic triaxial tests were carried out, following a multi-step loading procedure with various deviator stress amplitudes of 10, 30, 50, 100 and 200 kPa. Two target fines water contents (17.6% and 10.6%) and five coarse grain contents (0%, 10%, 20%, 35% and 45%) were considered. Results showed that under a given coarse grain content, an increase of water content led to a decrease of resilient modulus owing to the decrease of suction while an increase of damping ratio owing to the increase of soil viscosity. Through the variations of resilient modulus and damping ratio with coarse grain content_, a characteristic coarse grain content was identified, defining two distinct soil fabrics: a fine soil dominated fabric when the coarse grain content was smaller than the characteristic value, and a coarse grain dominated fabric when the coarse grain content was larger than the characteristic value. Moreover, a constant characteristic coarse grain content was obtained at a given water content: 25.5% at 17.6% water content and 32.0% at 10.6% water content. The increase of characteristic coarse grain content with the decrease of water content could be explained by the swelling-shrinkage of fine soil: with a decrease of water content, the shrinkage of fine soil led to an increase of the volume of macro-pores. More coarse grains were thus needed to constitute the global skeleton, giving rise to an increase of the characteristic coarse grain content. In addition, comparison of the values of characteristic coarse grain content obtained from cyclic tests with those from monotonic tests showed that at a given water content, cyclic loading led to a slightly larger value than monotonic loading, evidencing the more significant effect of cyclic loading on soil fabric.

对于法国古老的铁路轨道，由于交通负荷的影响，由于道grain颗粒和路基细土的相互渗透，自然形成了一个中间层。在降雨/蒸发作用下，夹层土壤中的水分会发生变化，从而影响其动态特性，例如弹性模量和阻尼比。为了研究含水量对层间土壤弹性模量和阻尼比的影响，按照多步加载程序，以10、30、50， 100和200 kPa。考虑了两个目标细粉含量（17.6％和10.6％）和五个粗粒含量（0％，10％，20％，35％和45％）。结果表明，在给定的粗粮含量下，含水量的增加由于吸力的降低而导致弹性模量的降低，而土壤黏度的提高则导致阻尼比的提高。通过弹性模量和阻尼比随粗粒含量的变化而变化_，确定了特征性粗粒含量，定义了两种不同的土壤织物：当粗粒含量小于特征值时为细土为主的织物，而当粗粒含量大于特征值时为粗粒为主的织物。而且，在给定的水含量下获得恒定的特征粗粒含量：在17.6％水含量下为25.5％，在10.6％水含量下为32.0％。特征粗粒含量随含水量的减少而增加，可以用细土的膨胀收缩来解释：随着含水量的减少，细土的收缩导致大孔体积的增加。因此，需要更多的粗晶粒来构成整体骨架，从而导致特征性粗晶粒含量的增加。