Abstract
The dam site area of Zhangjiazhai Reservoir in Guizhou is affected by the coupling effect of karst and igneous rock intrusion, where multiple deep weathering troughs have developed, posing severe challenges to engineering construction. Through surface geological survey, pit and trench exploration, drilling, geophysical exploration, and rock and soil mass testing, it has been identified that three longitudinal karst-weathering deep troughs are developed at the left dam abutment, and one horizontal weathering deep trough at the right dam abutment. The research findings reveal two genetic mechanisms of deep weathering troughs: 'tectonic-igneous rock-karst coupling' and 'contact zone differential weathering-tectonic-topography coupling', establishing a treatment framework of 'precise exploration-classified treatment-dynamic monitoring' for different types of deep weathering troughs, and proposing differentiated treatment measures. After curtain grouting treatment, downstream springs dried up, demonstrating obvious grouting effects, and the treated dam foundation meets stability requirements. The research results clarify the classification characteristics, genetic mechanisms, and treatment measures of deep weathering troughs in karst-igneous rock intrusion coupling zones, providing reference for similar projects.
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Preamble
Characteristics and Treatment of Weathered Deep Troughs Coupled with Igneous Intrusions in Karst Areas
YU Jiasong¹, GUO Guo¹, WU Denghao²
¹ PowerChina Guiyang Engineering Corporation Limited, Guiyang 550081, China
² Guizhou Survey and Design Research Institute for Water Resources and Hydropower, Guiyang 550002, China
Abstract
At the Zhangjiazhai Reservoir dam site in Guizhou, the coupling of karst processes and igneous intrusions has resulted in the development of multiple weathered deep troughs, posing severe challenges to construction. Through integrated investigation methods including surface geological surveys, pit and trench excavations, drilling, geophysical prospecting, and rock-soil mass testing, the study identified three longitudinal karst-weathered deep troughs at the left dam abutment and one horizontal weathered deep trough at the right dam abutment. The research reveals two distinct genetic mechanisms for these features: a "tectonic-igneous rock-karst coupling" mechanism and a "contact zone differential weathering-tectonic-topography coupling" mechanism. A treatment framework of "precision exploration—classification treatment—dynamic monitoring" was established for different types of weathered deep troughs, with differentiated treatment measures proposed accordingly. Following curtain grouting treatment, downstream springs dried up, demonstrating significant grouting effectiveness, and the treated dam foundation satisfied stability requirements. This study clarifies the classification characteristics, genetic mechanisms, and treatment measures for weathered deep troughs in karst-igneous intrusion coupling zones, providing valuable reference for similar engineering projects.
Keywords: Maokou Formation limestone; karst; diabase; reservoir; weathered deep trough