Optimizations for tunnel drainage water system based on locations of crystallizations

Crystalline blockages are common disease in tunnel drainage systems. In order to optimize the tunnel drainage system, it is necessary to identify the locations that are prone to crystallization. This paper recorded the quantity and the locations of the crystallizations in over ten tunnels in operation period along Renxin Expressway and Yinghuai Expressway in Guangdong Province. The crystal samples were taken from different locations to analyze their micromorphology through X-ray diffraction and scanning electron microscopy. The results show that tunnel crystallizations were mostly discovered at construction joints, inspection wells, and blind ditches, among which 74% of the crystallizations were at construction joints; the main constituent of in-situ crystals is calcite calcium carbonate, but the crystal stacking modes and micromorphology varied based on their locations in tunnel. The crystals at the construction joints are cubic with grains stacked in average-sized layers; those at the inspection wells are elliptic with larger grains loosely distributed; those at the blind ditches are acicular with cluster grains but greatly varied sizes. This paper proposes optimizations towards water stop structure and inspection wells in drainage ditch based on positions that are prone to crystallizations, providing a novel idea for solving the crystallization problem in the tunnel drainage system from the perspective of prevention and detection.