饱和细粒土孔隙结构定量表征
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摘要
土的物质组成多样且结构尺度跨度大,多物质成分和多尺度结构影响土体结构特征。借助室内试验及数值模拟(数据约束模型),表征饱和细粒土固结过程中多物质成分的多尺度结构,并进行三维结构定量表征,侧重探讨饱和细粒土固结过程中孔隙结构的变化特征。研究表明,饱和细粒土受压固结的蠕变界限在400 kPa左右,对应的界限孔隙值为0.4μm(微米孔隙)。随土样受压强度增加,土体中不同尺度的孔隙及其连通体数量均发生变化:孔隙和孔隙连通体数量都先增加后减少最后趋于稳定,但变化规律并不完全一致。孔隙数量在200 kPa压力时达到峰值,而孔隙连通体数量却在400 kPa压力下达到峰值,孔隙总体积受孔隙数量和孔隙体积两个因素影响。土体固结前期主要发生大孔隙变形,大孔隙数量是影响其固结效应的重要因素。而在固结后期,微小孔隙体积是影响土体固结效应和蠕变的关键因素之一。本研究多方法结构分析在突破吹填淤泥这类饱和细粒土的结构定量分析后,有利于物质微宏观力学理论的进一步深化。
The compositions of soils are various. Particularly, the scale of the soil structure is large. Both multi-material and multi-scale have an effect on the structural characteristics of soils. Based on the indoor experiments(MIP, SEM and X-μCT)and numerical simulation tests(data constrained modeling, abbreviated as DCM), the multi-scale structure of multi-component in the consolidation process of saturated fine-grained soil is studied. In addition, 3D structure of saturated fine-grained soil is analyzed quantitatively. This study focuses on studying the changing mechanism of soil structure in the process of consolidation.The results show that the pressure reaches 400 kPa approximately when the saturated fine-grained soil begins to creep. The corresponding critical value of pore diameter is 0.4 μm(micrometer-pore). The pore and pore cluster quantities increase with the increasing pressure and then decrease. Beyond this value, there is no noticeable change. However, the change rules of pore and pore cluster are not entirely consistent. The quantities of pore and pore cluster reach the peak at pressure up to 200 kPa and 400 kPa, respectively. The methods in this study are not only applied in saturated fine-grained soil, but also contributes to further study on the micro-macroscopic mechanics of other materials. The DCM may become a breakthrough when analyzing the structure of other soil materials. Thus, the quantitative characterization of various soil structures may be achieved.
The compositions of soils are various. Particularly, the scale of the soil structure is large. Both multi-material and multi-scale have an effect on the structural characteristics of soils. Based on the indoor experiments(MIP, SEM and X-μCT)and numerical simulation tests(data constrained modeling, abbreviated as DCM), the multi-scale structure of multi-component in the consolidation process of saturated fine-grained soil is studied. In addition, 3D structure of saturated fine-grained soil is analyzed quantitatively. This study focuses on studying the changing mechanism of soil structure in the process of consolidation.The results show that the pressure reaches 400 kPa approximately when the saturated fine-grained soil begins to creep. The corresponding critical value of pore diameter is 0.4 μm(micrometer-pore). The pore and pore cluster quantities increase with the increasing pressure and then decrease. Beyond this value, there is no noticeable change. However, the change rules of pore and pore cluster are not entirely consistent. The quantities of pore and pore cluster reach the peak at pressure up to 200 kPa and 400 kPa, respectively. The methods in this study are not only applied in saturated fine-grained soil, but also contributes to further study on the micro-macroscopic mechanics of other materials. The DCM may become a breakthrough when analyzing the structure of other soil materials. Thus, the quantitative characterization of various soil structures may be achieved.
引文
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[5]杨爱武,闫澍旺,杜东菊.结构性吹填软土蠕变模型研究[J].岩土力学,2012,33(11):3213-3218,3224.(YANGAi-wu,YAN Shu-wang,DU Dong-ju.Study of creep model ofstructural soft dredger fill[J].Rock and Soil Mechanics,2012,33(11):3213-3218,3224.(in Chinese))
[6]李学,刘治清,宋晶,等.有机质在吹填淤泥固结中的微宏观特征[J].中国海洋大学学报(自然科学版),2017,47(10):28-35.(LI Xue,LIU Zhi-qing,SONG Jing,et al.Micro-macro characteristics of organic matter in dredger fill consolidation[J].Periodical of Ocean University of China,2017,47(10):28-35.(in Chinese))