干湿循环作用下压实黄土裂隙演化特征

doi:10.11988/ckyyb.20230394

摘要/Abstract

摘要：

为了解干湿循环作用下压实黄土裂隙演化规律,通过自制装置开展考虑不同干密度和干湿循环路径的干湿循环裂隙试验,获取土样表面裂隙发育图像。采用PCAS软件对土样裂隙进行定量化分析,获得裂隙形态特征参数,并结合数字图像相关(DIC)法获得土样应变场。结果表明:①压实黄土裂隙发育随干湿循环次数的增长可划分为裂隙缓慢发展、快速增长和裂隙缓滞发展3个阶段;②裂隙发育程度受干密度、干湿循环路径共同影响,干密度越大,裂隙越难发育,干湿循环幅度越大、下限含水量越低,裂隙发育越充分;③裂隙中心线部位第一主应变随距起裂点距离的增大呈线性减小趋势,裂隙尖端、裂隙临近区块土体所受挤压作用随远离裂隙程度增大而减弱。研究成果可为压实黄土裂隙演化特征分析提供参考。

关键词: 压实黄土, 干湿循环, 裂隙发育, 数字图像相关(DIC)技术, 应变场

Abstract:

To investigate the evolution of fractures in compacted loess under drying-wetting cycles, we conducted crack tests by varying the dry density and drying-wetting path using a self-developed device, and captured the surface crack patterns of soil samples.Furthermore, we quantitatively analyzed the soil cracks using PCAS software for morphological parameters and obtained strain fields via DIC (Digital Image Correlation) method. Our findings revealed three distinct stages in the development of compacted loess cracks with increasing drying-wetting cycles: initial slow growth, subsequent rapid expansion, and stabilization. Crack development intensity was influenced by both dry density and drying-wetting cycle paths. Higher dry densities hindered crack propagation, while larger amplitude of drying-wetting and lower moisture thresholds cultivated crack development. Additionally, the first principal strain along the crack’s central line exhibited a linear decrease with distance from the crack initiation point, indicating diminishing soil compression effects near the crack tip and adjacent blocks. These results provide insights into understanding crack evolution in compacted loess.

Key words: compacted loess, drying-wetting cycles, crack propagation, DIC, strain field

中图分类号:

TU43土力学

胡长明, 胡婷婷, 朱武卫, 袁一力, 杨晓, 柳明亮, 侯旭辉. 干湿循环作用下压实黄土裂隙演化特征[J]. 长江科学院院报, 2024, 41(8): 96-103.

HU Chang-ming, HU Ting-ting, ZHU Wu-wei, YUAN Yi-li, YANG Xiao, LIU Ming-liang, HOU Xu-hui. Evolution Characteristics of Cracks in Compacted Loess under Drying-Wetting Cycles[J]. Journal of Yangtze River Scientific Research Institute, 2024, 41(8): 96-103.

图/表 17

表1 土体的基本物理性质

Table 1 Physical parameters of the compacted loess

相对密度	液限/ %	塑限/ %	塑性指数	颗粒组成/%
相对密度	液限/ %	塑限/ %	塑性指数	>0.075 mm	0.075~ 0.005 mm	<0.005 mm
2.70	29.7	18.4	11.3	1.05	78.43	20.52

图1 试验装置示意图

Fig.1 Diagram of test apparatus

图2 PCAS系统处理过程示意图

Fig.2 Diagram of PCAS system processing

图3 土样不同干湿循环次数后表面裂隙形态

Fig.3 Surface crack patterns after different drying-wetting cycles

图4 不同干湿循环次数后裂隙指标

Fig.4 Crack indices after different drying-wetting cycles

图5 不同干密度土样表面裂隙分布

Fig.5 Distribution of surface cracks of samples with different dry densities

图6 不同干密度下的裂隙指标

Fig.6 Crack indices of samples with different dry densities

图7 不同干湿循环路径下土样表面裂隙分布

Fig.7 Distribution of surface cracks under different drying-wetting paths

图8 不同干湿循环路径下裂隙指标

Fig.8 Crack indices under different drying-wetting paths

图9 首次减湿过程中土样表面第一主应变场分布

Fig.9 Distribution of the first principal strain field on soil sample surface during the first drying process

图10 不同干湿循环次数后土样第一主应变分布场

Fig.10 Distribution of the first principal strain field of soil samples after different drying-wetting cycles

图11 不同土体部位第一主应变变化曲线

Fig.11 Variation curves of the first principal strain at different soil positions

图12 裂隙中心线主应变与起裂点距离关系曲线

Fig.12 Relationship between principal strain along the crack’s central line and distance from the crack initiation point

图13 不同干密度土体第一主应变场

Fig.13 The first principal strain field of soil samples with different dry densities

图14 不同干密度土体局部位置应变变化曲线

Fig.14 Strain curves of parts of the soil samples with different dry densities

图15 不同干湿循环路径土体第一主应变场

Fig.15 The first principal strain field of soil samples under different cycle paths

图16 不同干湿循环路径下土体局部位置第一主应变曲线

Fig.16 Variation curves of the first principal strain at parts of the soil samples under different cycle paths

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