School of Civil Engineering, Chang'an University, Xi'an, Shaanxi province, China.
PLoS One. 2024 Mar 13;19(3):e0298653. doi: 10.1371/journal.pone.0298653. eCollection 2024.
Soil structure and overconsolidation are two important factors that affect soil strength. Current research studies have primarily focused on the influence of single factors, and relatively few studies have studied the coupling effect of the two. In this paper, the effects of structure and overconsolidation on the mechanical properties of loess under certain conditions have been studied by compression tests and direct shear tests. Undisturbed loess, remolded loess, overconsolidated undisturbed loess, and overconsolidated remolded loess were investigated in this work. The results indicate that structure and overconsolidation can enhance the overall strength of the soil, but the effects of these two factors also interfere and weaken each other. The combined effect of structure and overconsolidation can lead to higher soil shear strength. Compared with remolded normally consolidated soil, when the vertical pressure is 50kPa, 100kPa, and 200kPa, the structure increases the strength of the original normally consolidated soil by 35%, 21%, and 7%, respectively. Overconsolidation increases the strength of the remolded overconsolidated soil by 51.3%, 40.9%, and 17.7%, respectively. The combined effect of structure and overconsolidation increases the strength of the original overconsolidated soil by 89%, 72.5%, and 32.7%, respectively. The increase in soil strength caused by the coupling effect is smaller than the sum of the strength increase caused by the two factors. The main reason is that the soil structure can reduces the compaction effect of overconsolidation, and the compaction load applied during the process of overconsolidation can also damage the soil structure, and the scanning electron microscopy observation is consistent with the experimental results and analysis. Finally, an empirical relation was developed for the effect of overconsolidation, structural properties, and their coupling on soil strength. The calculated results of the formula are highly consistent with the experimental data, and have good rationality and accuracy.
土壤结构和超固结是影响土强度的两个重要因素。目前的研究主要集中在单一因素的影响上，而研究两者耦合效应的相对较少。本文通过压缩试验和直剪试验研究了一定条件下黄土的结构和超固结对力学性质的影响。本文研究了原状黄土、重塑黄土、超固结原状黄土和超固结重塑黄土。结果表明，结构和超固结可以提高土的整体强度，但这两个因素的影响也相互干扰和削弱。结构和超固结的综合效应会导致土的剪切强度更高。与重塑正常固结土相比，当垂直压力为 50kPa、100kPa 和 200kPa 时，原状正常固结土的结构分别使原状正常固结土的强度提高了 35%、21%和 7%。超固结使重塑超固结土的强度分别提高了 51.3%、40.9%和 17.7%。结构和超固结的综合效应使原状超固结土的强度分别提高了 89%、72.5%和 32.7%。由耦合效应引起的土壤强度增加小于两个因素引起的强度增加之和。主要原因是土壤结构可以降低超固结的压实效果，而超固结过程中施加的压实荷载也会破坏土壤结构，扫描电子显微镜观察与实验结果和分析一致。最后，建立了超固结、结构特性及其耦合对土强度影响的经验关系。公式的计算结果与实验数据高度一致，具有良好的合理性和准确性。
