南水北调工程下穿高速公路暗涵施工控制技术

南水北调是国家重点工程，下穿既有结构物的大型暗涵是南水北调工程中一种比较典型的结构形式。下穿段浅埋暗挖施工过程中洞内安全和地面环境问题突出；对于大型钢筋混凝土结构而言，施工中防温裂技术难度大，影响因素错综复杂，一旦控制不当，容易造成结构裂缝超限。严重影响暗涵结构的耐久性和使用功能。论文以南水北调中线古运河枢纽工程下穿石太高速公路段为背景，对既有高速公路路面沉降和箱涵结构混凝土限裂温控标准进行了分析研究。研究认为，施工过程中既有路面沉降应控制在100mm以内、结构混凝土内部温降应控制在54．4℃以下，并在此基础上，提出了双中洞多分部开挖技术、一次性施作长管棚结合小导管注浆超前预支护技术、设置遮阳棚和地垄储料保温措施等综合施工技术，确保了施工过程中既有高速公路的运营安全和暗涵结构的工程质量。

Construction Control Technology of Underdrain Beneath Existing Expressway in South-to-North Water Transfer Project

The large-scale culvert under-crossing existing structure is a typical structure in South-to-North water transfer project, a national major project in China. The control technology of ground surface settlement and structure temperature crack is complex during tunneling in the under-crossing segment. The Guyunhe underdrain project is a main section of the middle route project of South-to-North water diversion, in which the culvert crosses under the Shi-Tai expressway near the city of Shijiazhuang. Some problems about the constructing control standards are discussed based on this project in this paper. The results suggest that the existing road surface subsidence should he controlled within 100 mm and the temperature decrease of structural concrete should he controlled within 54.4 ℃ to fulfill requirement of the construction environment and structural temperature crack limit. On this basis, the corresponding control measures, such as Multi-hole pairs of partial excavation technology, long pipe roof with a small tube grouting technology, sun-shading awning and material storage barn insulation technology, are put forward to ensure the project quality and the operation safety of existing expressway.