反复吸湿循环对原状残积土剪切特性的影响

发布时间：2018-03-03 10:53

本文选题：道路工程　切入点：原状残积土　出处：《中国公路学报》2017年02期 　论文类型：期刊论文

【摘要】：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。
[Abstract]:In order to study the shear characteristics of natural soil under repeated hygroscopicity cycle due to the change of suction path, the triaxial test of unsaturated soil under different confining pressure, suction and repeated moisture absorption was carried out. Based on the effective stress principle, the hysteretic characteristics of mineral composition and soil-water characteristic curve (SWCC), the differences in shear characteristics of unsaturated soils caused by different water absorption conditions are analyzed and explained from various angles, at the same time, The effect of saturation change on soil strength caused by hysteresis characteristics of SWCC was studied, and the change trend of unsaturated soil volume after different times of water absorption was studied. The results show that the ductility and shearing shrinkage of undisturbed residual soils are similar to those of normal consolidated soils. Under the same suction condition, the difference of shear strength between the first desorption and the hygroscopic path does not increase with the increase of effective stress, but at the same confining pressure, the first desorption occurs at the same confining pressure. The difference of shear strength of moisture absorption path shows a decreasing trend with the increase of suction, the increase of total volume of residual soil is irreversible and hysteresis after multiple water absorption, and the swelling and shear fracture characteristics of soil are related to the effective stress and suction level. The larger the stress level is, the more obvious the strain softening effect of soil is, and the soil softening is related to the change of soil saturation caused by hydraulic hysteresis and the irreversible deformation (or cumulative irreversible deformation) caused by hydraulic hysteresis. The cumulative irreversible deformation caused by multiple desorption cycles is the main reason for the decrease of soil strength. The results are of great significance to the stability analysis and design of residual soil slope.
【作者单位】：福建农林大学交通与土木工程学院;福州大学岩土工程与工程地质研究所;
【基金】：交通土建师资队伍博士化国际化工程项目(61201405105) 福建省自然科学基金项目(2015J01164)
【分类号】：TU43

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