添加砾石对崩岗岩土无侧限抗压强度的影响

崩岗是中国南方红壤地区常见的一种土壤侵蚀类型,该研究借鉴砾石影响降雨入渗、产流产沙和力学性质的研究成果,对砾石质量分数、形状和直径三因素进行正交设计,研究不同组合砾石对崩岗岩土无侧限抗压强度的影响。崩岗4层土体较好的处理分别为：淋溶层A：A3B1C1,质量分数15%,直径2～4 mm,圆砾;黏化层Bt：A3B2C1,质量分数15%,直径5～7 mm,圆砾;淀积层B：A3B2C1,质量分数15%,直径5～7 mm,圆砾;母质层C：A3B2C1,质量分数15%,直径5～7 mm,圆砾。4层土体的轴向应力随轴向应变均呈急剧上升、急剧下降、减速衰减和衰减稳定4个阶段,但砾石复合土高于未加砾石土。4层土体在较好处理下的无侧限抗压强度分别比未加砾石土提高59.56%、71.70%、49.51%和83.64%,且二者呈线性递增函数关系（R2＝0.99）,添加砾石的土柱在受压时破坏程度较小。本研究将为崩岗侵蚀预防和分层治理提供一定的理论依据。

Effects of gravel addition on unconfined compressive strength of Benggang soil

Abstract: Collapsing is a common type of soil erosion in red soil regions of south China, which is destructive and has a wide range of influence, and directly endangers agricultural development and the safety of people''s lives and property. Based on the research results of gravel influencing on rainfall infiltration, flow generation, sand production, and mechanical properties, this study preliminarily determined the conditions of rocking-gravel combination including gravel content, gravel shape and gravel diameter. Due to the difference in the size and shape of gravel particles, the bite difference between soil and gravel is obvious, which has a great influence on the mechanical properties of soil mass. It was found that the Eluvial layer A had relatively average particle size, good structure, and fine texture. In other three layers, the contents of three particle sizes differed greatly with poor adhesive and texture, and loose particles. For 4 layers of collapsing hill soil, the axial stress of CK and optimal gravel-fortified soil samples had the same change trend with axial stress, and all experienced 4 stages of up sharply, down sharply, down slowly, and down stably, but the axial stress curve of gravel composite soil was above that of CK, especially the Eluvial layer A and Argic layer Bt. The optimal gravel-soil combination conditions varied with the soil layer: for Eluvial layer A, with 15% gravel content, 2-4 mm gravel diameter, and pebble gravel-shaped; for Argic layer Bt, with gravel content 15%, gravel diameter 5-7 mm, and pebble gravel-shaped; for deposition layer B, with gravel content 15%, gravel diameter 5-7 mm, and pebble gravel-shaped; for Parent layer C, with 15% gravel content, 5-7 mm gravel diameter, and pebble gravel-shaped. The unconfined compression strengths of gravel-fortified soils at different level were significantly higher than that of CK, which increased by 59.56%, 71.70%, 49.51%, and 83.64%, respectively. The relationship between the unconfined compression strength of optimal gravel-fortified soil and no graveled soil presented a linear increasing function, showing that the addition of gravel had an obvious effect on enhancing the unconfined compression strength of collapsing hill soil. The soil without gravel was broken to different degrees. The Eluvial layer A and the parent material layer C were mainly broken at the lower part, and the parent material layer C had more debris due to its low clay content and cementation strength between the soil particles. The argic layer Bt and deposition layer B were mainly broken on one side of the soil column, because there were more clay particles and the cohesive force of the soil was strong, which made the soil column not easy to be destroyed. The failure degree of gravel-fortified soil column was less than that of no graveled soil, which could effectively improve the compressive performance at different level of collapsing hill soil, and the compressive mechanism of soil at different level was different. This study will provide some theoretical basis and guidance for the prevention and control of landslide erosion and the study of landslide stability.