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为了研究反复吸湿循环下天然土体因吸力路径变化引起道路、桥梁等工程土体剪切特性变化的规律,开展了不同围压、吸力和反复吸湿条件下的非饱和土三轴试验研究,从有效应力原理、矿物成分和土水特征曲线(SWCC)滞回特性出发,对不同吸水条件引起的非饱和土剪切特性差异进行多角度分析和解释;同时,研究不同吸水次数后非饱和土体积变化趋势和SWCC滞回特性引起饱和度变化对土体强度的影响,深入分析土体抗剪强度吸水软化的原因。结果表明:脱湿路径下原状残积土表现出的延性和剪缩特性与正常固结土的剪切性状相似,而吸湿路径下土样具有的脆性和剪胀特性与超固结土相符;同一吸力条件下,第1次脱、吸湿路径的抗剪强度差值并不随有效应力的增加而增加;而相同围压下,第1次脱、吸湿路径的抗剪强度差值表现出随吸力增加而减小的趋势;多次吸水后,残积土总体积增加具有不可逆和滞后的特点,土体膨胀性和剪破特性与有效应力和吸力水平有关,应力水平越大,土体应变软化效应越明显;土体软化与水力滞回特性引起土体饱和度的变化和产生的不可逆变形(或累积不可逆变形)有关,多次脱吸湿循环产生的累积不可逆变形是导致土体强度下降的主要原因。研究结果对残积土边坡稳定性分析评价及其治理设计具有重要意义。
In order to study the regularity of the change of shear characteristics of natural soil under roadway, bridge and so on due to the change of suction path under repeated hygroscopic cycles, the triaxial tests of unsaturated soils under different confining pressure, suction and repeated moisture absorption were carried out. From Effective stress principle, mineral composition and soil water characteristic curve (SWCC) hysteresis characteristics of different conditions of unsaturated soils caused by different water absorption characteristics of multi-angle analysis and interpretation of multi-angle; the same time, the number of different water absorption of unsaturated soil volume The trend of change and SWCC hysteresis characteristics caused by the change of saturation on the strength of soils. The results show that the ductility and shear-shrinkage of undisturbed intact soil under the desiccant path are similar to that of the normal consolidated soil, while the brittle and dilatant characteristics of the soil specimen under the moisture-absorbing path are consistent with the overconsolidated soil. Under the same confining pressure, the difference of the shear strength of the first off-moisture absorption path does not increase with the increase of the effective stress. Under the same confining pressure, But the trend of decreasing is that after repeated water absorption, the total volume of residual soil increases irreversibly and lag. The expansibility and shear characteristics of soil are related to the effective stress and suction level. The greater the stress level, the more the strain softening effect It is obvious that soil softening and hydraulic hysteresis are related to the change of soil saturation and irreversible deformation (or cumulative irreversible deformation). The cumulative irreversible deformation caused by multiple dehumidification cycles is the main reason for the decrease of soil strength. The research results are of great significance for the analysis and evaluation of the stability of residual soil slope and its treatment and design.