The compression behaviour of fine-grained soils is mainly controlled by pore collapse, while the compression behaviour of sands is mainly governed by grain breakage. For soils containing both fine and coarse soil particles such as quartz and calcite grains, the compressibility may depend on both pore collapse and grain breakage. In this study, the compressibility of two natural soils reported in the literature was first analysed in this sense, showing the effect of grain breakage on the compressibility of soils. To further verify this phenomenon, high-pressure oedometer tests were carried out on a natural stiff clay containing a significant fraction of granular elements. The obtained results confirmed the significant effect of grain breakage. In order to better understand the role of fines in the grain breakage phenomenon, artificial sand–clay mixtures were prepared with different fine fractions and tested in oedometer. Results show that the compression behaviour of sand–clay mixtures can be roughly divided into three zones according to the fine fractions: at low fine fractions, the compression behaviour is governed by grain breakage; at high fine fractions, the compression behaviour is governed by the pore collapse of fines; and at medium fine fractions, both pore collapse and grain breakage affect the compression behaviour. In this last case, pore collapse occurs first, letting grains to be well in contact either directly (grain–grain contacts) or indirectly (grain–fine grain contacts) to activate the grain breakage phenomenon upon further loading. This is consistent with the identified compression behaviour of natural fine-grained soils.

细粒土的压缩行为主要受孔隙坍塌控制，而砂土的压缩行为主要受颗粒破碎控制。对于含有细颗粒和粗颗粒的土壤，如石英和方解石颗粒，可压缩性可能取决于孔隙坍塌和颗粒破碎。本研究首先从这个意义上分析了文献报道的两种天然土壤的可压缩性，显示了颗粒破碎对土壤可压缩性的影响。为了进一步验证这一现象，对含有大量粒状元素的天然硬质粘土进行了高压固结仪测试。所得结果证实了谷物破碎的显着影响。为了更好地了解细粉在颗粒破碎现象中的作用，用不同的细粒制备人造砂-粘土混合物，并在固结仪中进行测试。结果表明，砂土混合物的压缩行为可以根据细粒级分粗略分为三个区域：在低细粒级时，压缩行为受颗粒破碎的控制；在高细粒分数下，压缩行为由细粒的孔隙坍塌控制；在中等细粒级，孔隙坍塌和颗粒破碎都会影响压缩行为。在最后一种情况下，孔隙坍塌首先发生，让颗粒直接（颗粒-颗粒接触）或间接（颗粒-细颗粒接触）良好接触，以在进一步加载时激活颗粒破碎现象。这与已确定的天然细粒土壤的压缩行为一致。