张宁, 兰恒星, 李郎平, 等. 2022. 青藏高原东南缘实测地应力特征及意义分析[J]. 工程地质学报, 30(3): 696-707. doi: 10.13544/j.cnki.jeg.2022-0112.
    引用本文: 张宁, 兰恒星, 李郎平, 等. 2022. 青藏高原东南缘实测地应力特征及意义分析[J]. 工程地质学报, 30(3): 696-707. doi: 10.13544/j.cnki.jeg.2022-0112.
    Zhang Ning, Lan Hengxing, Li Langping, et al. 2022. Characteristics and implications of in-situ stresses in Southeastern Tibetan Plateau[J]. Journal of Engineering Geology, 30(3): 696-707. doi: 10.13544/j.cnki.jeg.2022-0112.
    Citation: Zhang Ning, Lan Hengxing, Li Langping, et al. 2022. Characteristics and implications of in-situ stresses in Southeastern Tibetan Plateau[J]. Journal of Engineering Geology, 30(3): 696-707. doi: 10.13544/j.cnki.jeg.2022-0112.

    青藏高原东南缘实测地应力特征及意义分析

    CHARACTERISTICS AND IMPLICATIONS OF IN-SITU STRESSES IN SOUTHEASTERN TIBETAN PLATEAU

    • 摘要: 在广泛收集整理了900组实测地应力数据的基础上,结合中国大陆现代构造应力场应力分区,通过统计回归分析的方法,分析了青藏高原东南缘5个4级应力区的主应力、侧压力系数、应力积累水平等应力量值特征随深度的变化规律,同时结合震源机制解分析了应力区的应力方向特征。研究结果表明:(1)巴颜喀拉山应力区、龙门山-松潘应力区、墨脱-昌都应力区的应力梯度值较大,深部应力状态以水平应力为主,川滇和滇西南应力区的梯度值较小,深部应力状态以垂直应力为主,应力分布呈现“北强南弱”的特征;(2)应力积累水平参数μm的大小表明,巴颜喀拉山应力区、龙门山-松潘应力区与川滇应力区的应力积累水平较高,更接近摩擦极限平衡状态,发生地震的可能更大;(3)最大水平主应力优势方向表现为围绕喜马拉雅东构造结呈顺时针旋转,与中上地壳的震源机制得到最大水平方向的优势方向具有一致性。利用上述结果,结合地壳动力学模型,初步定性分析了“北强南弱”的应力特征可能是由于北侧应力区受块体侧向挤出模型控制,南侧应力区受下地壳流模型控制。最后以岩爆为例,基于各应力区的应力状态对重大地下工程稳定性进行了评价,分析表明青藏高原东南缘在0~2 km范围内岩爆风险等级以轻微岩爆、中等岩爆和强烈岩爆为主,局部区域存在极强岩爆,且各应力区相同岩爆等级对应的埋深具有明显差异性。

       

      Abstract: This paper examines the variation characteristics of principal stress, lateral pressure coefficient and stress accumulation level with depth in the five tectonic stress zones(i.e., the Bayankala Mountain, Longmenshan-Songpan, Motuo-changdu, Sichuan-Yunnan and southwestern Yunnan stress zones) within the southeastern Tibetan Plateau. It uses the statistical regression analysis based on an extensive collection of 900 groups of in-situ stress data. The stress direction characteristics were also analyzed based on a combined analysis of focal mechanism with the orientation of the maximum horizontal in-situ stress. The results show that: (1)In the Bayankala Mountain, Longmenshan-Songpan and Motuo-changdu stress zones, the stress gradients are relatively large, and the deep stress is dominated by the horizontal component; while, in the Sichuan-Yunnan and southwestern Yunnan stress zones, the stress gradients are relatively small, and the deep stress is dominated by the vertical component; showing a stress pattern of "strong in north and weak in south". (2)The ratio of average differential stress to average effective stress(μm), which is a parameter measuring the stress accumulation level, is relatively high in the Bayankala Mountain, Longmenshan-Songpan and Sichuan-Yunnan stress zones, suggesting a state closer to the limit equilibrium of friction, and thus a higher probability of earthquake. (3)The dominant direction of the maximum horizontal stress of the southeastern Tibet Plateau rotates clockwise around the eastern Himalayan syntaxis, which is consistent with the GPS velocity field and the dominant direction of the maximum horizontal stress derived from the focal mechanism in the middle and upper crust. Based on these results, we preliminarily concluded that the stress pattern of "strong in north and weak in south" may be owing to the dominances of block lateral extrusions in north and lower crustal flows in south. Finally, using rock burst risk as an index, the stability of major underground projects in each stress zone was evaluated based on the stress state. The results show that: the rockburst risks within 0~2 km buried depth in the southeastern Tibetan Plateau are mainly low, moderate and high and that extremely high rock burst risk only exists in local areas. Furthermore, the buried depths of the same rock burst risk level at different stress zones have obvious differences.

       

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