湿干冻融下渠基膨胀土裂隙发育与强度衰减规律研究

Research on crack development and strength attenuation of expansive soil under wet-dry freeze-thaw effect

摘要

【目的】寒旱区湿干冻融循环作用下膨胀土输水渠道易发生浅层失稳，是膨胀土输水渠道安全运行的关键问题。【方法】以北疆伊犁河北岸干渠膨胀土为研究对象，对试样进行湿干冻融循环效应的模拟和低应力直剪试验，分析试验过程中膨胀土的裂隙参量，探讨裂隙参量与膨胀土强度特性的变化规律，研究裂隙参量对膨胀土强度特性的影响规律。【结果】结果显示：膨胀土试样的裂隙参量与黏聚力衰减率会随湿干冻融交替效应和密实程度的降低而增大，其力学性能会进一步劣化。湿干冻融循环效应下，膨胀土裂隙结构经历了快速开裂、稳步拓展、稳定发育过程，与黏聚力的快速衰减、缓慢衰减、稳定衰减阶段相对应。【结论】结果表明：抗剪强度与各裂隙参量有一定相关性，其中连通系数的变化趋势与黏聚力衰减的关联性最为密切，关联度为0.730~0.878,权重达到0.260~0.300,可定量表征湿干冻融循环效应下膨胀土的裂隙发育特征及强度衰减规律。

Abstract

[Objective] Shallow instability of expansive soil water conveyance channel is easy to occur under the action of dry and wet freeze-thaw cycles in cold and arid regions, which is the key problem for the safe operation of expansive soil water conveyance channel. [Methods] Taking the expansive soil of the North bank of the Ili River in northern Xinjiang as the research object, the simulation of wet-dry freeze-thaw cycle effect and low stress direct shear test were carried out on the sample. The crack parameters of the expansive soil during the test were analyzed, and the changing rules of the crack parameters and the strength characteristics of the expansive soil were discussed. The influence of crack parameters on the strength characteristics of the expansive soil was studied. [Results] The result show that the fracture parameters and cohesion decay rate of the expanded soil sample will increase with the decrease of wet-dry freeze-thaw effect and the density degree, and the mechanical properties will further deteriorate. Under the wet-dry freeze-thaw cycle effect, the crack structure of expansive soil experienced rapid cracking, steady expansion and steady development, corresponding to the rapid decay, slow decay and steady decay stages of cohesion, indicating that the shear strength has a certain correlation with the fracture parameters, and the change trend of the connectivity coefficient is most closely related to the decay of cohesion. [Conclusion] The correlation degree ranges from 0.730 to 0.878 and the weight ranges from 0.260 to 0.300, which can quantitatively characterize the fracture development characteristics and strength attenuation rule of expansive soil under the effect of wet-dry freeze-thaw cycle.

关键词

膨胀土 / 湿干冻融循环 / 裂隙参量 / 强度衰减 / 关联度 / 变形

Key words

expansive soil / wet-dry freeze-thaw cycle / fracture parameter / the intensity attenuation / degree of association / deformation

基金资助

自治区“天山英才” 青年拔尖人才培养计划(2024TSYCCX0037)

国家自然科学基金项目(52369021)

第二批“天山英才” 优秀工程师培养计划项目(2024—2026)