库区节理岩体干湿循环-动荷载损伤机理研究

Damage mechanism of jointed rock masses in reservoir area under combined action of dry-wet cycles and dynamic loading

摘要

【目的】库区蓄水导致的水库地震以及库水位波动造成的库岸滑坡地质灾害频发，为准确评估白鹤滩水电站建设对库区边坡稳定性的影响，亟须开展库区节理岩体在干湿循环-动荷载联合作用下劣化特性研究。【方法】基于此，针对白鹤滩库区典型滑坡体中的节理白云岩与节理砂岩，通过室内试验手段，系统分析了不同岩性及不同损伤周期下节理岩体干湿循环-动荷载损伤机理。【结果】结果显示，在干湿循环-动荷载联合作用下，前3个周期节理岩体快速劣化，节理砂岩与白云岩剪切强度劣化率达到25.5%与22.3%,在5个周期后劣化程度趋于稳定，12周期作用下节理砂岩黏聚力与内摩擦角劣化率达到22%与13%,而节理白云岩黏聚力与内摩擦角劣化率均达到了33%。【结论】结果表明，节理岩体的劣化主要受控于干湿循环导致的岩体矿物溶解以及动荷载造成的岩体结构面磨损；干湿循环对节理砂岩的劣化更为显著，低法向应力下，动荷载对砂岩结构面磨损更为严重，而高法向应力下动荷载对白云岩损伤加剧，导致在联合劣化作用下，节理砂岩剪切强度劣化率大于节理白云岩，但随着法向应力的增加，两种岩体强度劣化率差异减小。干湿循环-动荷载联合作用会显著劣化节理岩体力学性能，且受岩性、法向应力及作用周期的共同影响，为白鹤滩库区边坡稳定性评估与防灾减灾提供了重要的理论依据。

Abstract

[Objective] The reservoir-induced earthquakes caused by the impoundment and geological hazards such as reservoir bank landslides triggered by fluctuations in reservoir water level frequently occur. To accurately assess the impact of the Baihetan hydropower station construction on slope stability in the reservoir area, it is imperative to investigate the degradation characteristics of jointed rock masses under the combined action of dry-wet cycles and dynamic loading. [Methods] Based on this, for jointed dolomite and jointed sandstone collected from typical landslides in the Baihetan reservoir area, laboratory tests were conducted to systematically analyze the damage mechanisms of jointed rock masses under dry-wet cycles and dynamic loading, considering different lithologies and damage cycles. [Results] The result showed that under the combined action of dry-wet cycles and dynamic loading, the jointed rock masses rapidly degraded in the first three cycles. The shear strength degradation rates reached 25.5% for jointed sandstone and 22.3% for jointed dolomite. After five cycles, the degradation degree tended to stabilize. Under twelve cycles, the degradation rates of cohesion and internal friction angle of jointed sandstone rock masses reached 22% and 13%, and those of jointed dolomite rock masses both reached 33%. [Conclusion] The result indicate that the degradation of jointed rock masses is primarily controlled by mineral dissolution caused by dry-wet cycles and the abrasion of structural planes induced by dynamic loading. The degradation caused by dry-wet cycles is more pronounced for the jointed sandstone. Under low normal stress, more severe abrasion on sandstone structural planes is caused by the dynamic loading, whereas under high normal stress, higher damage degree of dolomite is caused by the dynamic loading. Under the combined degradation, the shear strength degradation rate of jointed sandstone is greater than that of jointed dolomite. However, this difference in strength degradation rates between the two rock types diminishes with increasing normal stress. The mechanical properties of jointed rock masses are significantly degraded by the combined action of dry-wet cycles and dynamic loading, and affected by lithology, normal stress, and the number of cycles. This provides an important theoretical basis for slope stability assessment and disaster mitigation in the Baihetan reservoir area.

关键词

节理岩体 / 干湿循环 / 动荷载 / 剪切强度 / 劣化机理 / 力学性能 / 损伤周期 / 滑坡

Key words

jointed rock masses / dry-wet cycles / dynamic loading / shear strength / degradation mechanism / mechanical properties / damage cycle / landslide

基金资助

国家自然科学基金项目(42577165)

国家自然科学基金项目(42207218)

中国三峡建工(集团)有限公司科研项目(BHT/0930)