针对淤泥质黏土及高填方地基处理方案的深化研究

In-Depth Research on Soft Soil and High Fill Foundation Treatment Scheme

摘要: 成都东1000 kV变电站作为“西电东送”战略的重要枢纽，建设过程中面临严峻的地质挑战，站址内存在淤泥质黏土、以风化基岩为主要回填料的高填方，而普遍存在于站区的风化基岩具有遇水易离析崩塌特性，这些不良地质都会导致地基湿陷沉降和变形。针对场地存在2~7 m厚、体积约250,000 m³的淤泥质黏土，以及最大13 m厚的填方问题，采用常规强夯法可能会使淤泥质黏土变成橡皮土，不能满足设计要求。通过方案比选与现场试验，提出“强夯置换 + 分层强夯 + 灌注桩”的综合处理方案，利用挖出的中风化基岩通过强夯工艺置换淤泥质软土，再分层夯实风化基岩回填土层，最后在夯实地基上浇筑灌注桩。该方案不仅提高建(构)筑物地基承载力，减少桩基负摩阻力，又能有效控制地面沉陷与不均匀沉降；同时通过设置排洪沟、盲沟及站内排水沟等一系列有组织排水措施，保证风化基岩的稳定。该方案具有良好的技术可行性和经济性。其中强夯置换处理方案作为场地预处理在特高压工程中的首次大面积应用，研究成果可为复杂地质条件下特高压变电站的地基处理设计提供借鉴和参考。

Abstract: The Chengdu East 1000 kV Substation, as a critical hub of the “West-to-East Power Transmission” strategy, faced severe geological challenges during its construction. The site contained mucky clay and high fill areas primarily composed of weathered bedrock. The prevalent weathered bedrock across the station area exhibited characteristics of easy disintegration and collapse upon contact with water, while these unfavorable geological conditions could lead to foundation wetting-induced settlement and deformation. To address the site’s mucky clay layer, which was 2~7 meters thick with a volume of approximately 250,000 m³, as well as fill areas with a maximum thickness of 13 meters, conventional dynamic compaction methods risked turning the mucky clay into elastic soil, failing to meet design requirements. Through solution comparisons and field tests, a comprehensive treatment scheme of “dynamic compaction replacement + layered dynamic compaction + bored piles” was proposed. This method involved excavating moderately weathered bedrock and using dynamic compaction to replace the soft mucky clay, followed by layered compaction of the weathered bedrock backfill. Finally, bored piles were cast on the compacted foundation. This solution not only improved the foundation bearing capacity of structures and reduced negative skin friction on piles but also effectively controlled ground subsidence and differential settlement. Additionally, by implementing organized drainage measures such as flood diversion ditches, blind drains, and internal drainage ditches, the stability of the weathered bedrock was ensured. The solution demonstrated strong technical feasibility and cost-effectiveness. As the first large-scale application of dynamic compaction replacement for site pre-treatment in ultra-high voltage (UHV) projects, this research provides valuable references for foundation treatment design in UHV substations under complex geological conditions.