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<p>The 2018 Baige landslide within the Jinsha River tectonic suture zone on the eastern Tibetan Plateau triggered a severe disaster chain. Field investigations identified that the landslide’s source area was predominantly composed of clay-altered rock masses. However, the mechanical properties of these materials were poorly understood, hindering a comprehensive explanation of the failure mechanism. This study combined detailed field surveys with large-scale in-situ direct shear tests on the clay-altered rocks and back-analysis of the landslide’s pre-failure initiation strength. We established an empirical formula linking the shear strength of the altered soft rock to its degree of alteration, characterized by block proportion, which clearly describes how the internal friction angle varies with block content. The back-analysis yielded an overall initiation strength significantly higher than in-situ test results, indicating that the slip zone is a heterogeneous mixture of intermittent altered zones and intact rock blocks, not purely clay. Furthermore, we reveal a combined control mechanism wherein the fragmented rock mass structure and the clay-altered rocks jointly govern slope stability. Altered zones develop along joints, with a set sub-parallel to the slope controlling failure. Under long-term gravitational creep and external dynamics, these discontinuous zones progressively interconnect, allowing the slip surface to reach initiation strength and leading to catastrophic failure. This research provides a critical theoretical foundation for risk assessment and prevention of large landslides in tectonic suture zones globally.</p>

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Formation Mechanism of the Catastrophic Baige Landslide in the Jinsha River, Tibet, China: New Insights from Clay-Altered Rocks in the Tectonic Suture Zone

  • 期刊论文

  • 发表日期：

    2026年5月20日

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  • Sanshao Ren,
  • Yongshuang Zhang,
  • Shenghua Cui,
  • Jinqiu Li,
  • Jingxin Gong,
  • Xiang Li

摘要

The 2018 Baige landslide within the Jinsha River tectonic suture zone on the eastern Tibetan Plateau triggered a severe disaster chain. Field investigations identified that the landslide’s source area was predominantly composed of clay-altered rock masses. However, the mechanical properties of these materials were poorly understood, hindering a comprehensive explanation of the failure mechanism. This study combined detailed field surveys with large-scale in-situ direct shear tests on the clay-altered rocks and back-analysis of the landslide’s pre-failure initiation strength. We established an empirical formula linking the shear strength of the altered soft rock to its degree of alteration, characterized by block proportion, which clearly describes how the internal friction angle varies with block content. The back-analysis yielded an overall initiation strength significantly higher than in-situ test results, indicating that the slip zone is a heterogeneous mixture of intermittent altered zones and intact rock blocks, not purely clay. Furthermore, we reveal a combined control mechanism wherein the fragmented rock mass structure and the clay-altered rocks jointly govern slope stability. Altered zones develop along joints, with a set sub-parallel to the slope controlling failure. Under long-term gravitational creep and external dynamics, these discontinuous zones progressively interconnect, allowing the slip surface to reach initiation strength and leading to catastrophic failure. This research provides a critical theoretical foundation for risk assessment and prevention of large landslides in tectonic suture zones globally.