Abstract
In Ganzhou City, China, a complex bedrock lithology and structure, diverse topography, frequent engineering works, and abundant rainfall generate frequent, sudden, small-scale landslides that are difficult to prevent and control. This study integrates evidence data from a field investigation of landslides with geological-engineering analogues to document the distribution and development of these geohazards in Ganzhou City. Based on the distribution of landslides across different types of bedrock and soil, we identify five lithological groups prone to slope failure: granite, metamorphics (slate and phyllite), red sedimentary layers, clastic sedimentary rocks with weak interlayers, and loose Quaternary deposits. Granite and metamorphic bedrock are the two lithologies most prone to landslides. Our analysis of the genesis and mode of slope failure suggests that most landslides in Ganzhou City originated from four modes of slope failure: scouring erosion collapse, steep slope collapse, rock sliding along a rock stratum, and wedge-shaped block sliding and caving. An in-situ model test and numerical simulations were used to explore the evolution of slope deformation and failure on the most landslide-prone lithological groups, and the accumulation of debris post-failure. This work provides a reference for the assessment of the risk from, and the management of, landslide geohazards in Ganzhou City and geologically similar regions.
Highlights
Landslides, the most frequent geohazard in China, have attracted considerable research attention (Wang et al, 2011; Zhou and Zhao, 2013; Deng et al, 2021)
Owing to the complexity and diversity of bedrock and soil, different degrees of weathering, and variations in slope form and scale, the same external conditions result in the type and scale of landslides across these lithological groups. on the on-site investigation of slope failure suggested that landslides in Ganzhou City primarily result from the following four genetic mechanisms: a) scouring erosion collapse, b) steep slope collapse, c) rock sliding along a rock stratum, and, d) wedge-shaped block sliding and caving
Many landslide sites are concealed by vegetation cover
Summary
Landslides, the most frequent geohazard in China, have attracted considerable research attention (Wang et al, 2011; Zhou and Zhao, 2013; Deng et al, 2021). Flow-collapse landslides occur mainly on fully weathered granite, slate and phyllite slopes These slopes are steep, more than 15 m high, and formed on a thick weathering mantle with a loose, cohesive soil of low permeability. The weathering mantle slipped along such a structural plane after heavy rainfall (Figures 10A–C) Another rockslide along a bedrock stratum is located near the Xinwuxia Village road, in Ganzhou City, on the bedrock of limestone and phyllite interbeds of the Upper Sinian Laohutang Formation. In Ganzhou, wedge block sliding and caving occurs primarily on steep slopes of jointed and fractured, metamorphic, and clastic bedrock with weak layers and two or more dominant structural planes Slope failure of this type progresses in three stages. As the above results show, collapse-flow sliding led to a wide disaster range and a large amount of accumulated soil after failure; sliding along a rock stratum led to a narrow disaster range and a small amount of accumulated soil and rock after failure; wedge-shaped block sliding and caving occurred suddenly and at a high speed, leading to a wide disaster range, but the amount of soil and rock accumulated after failure was small
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