Stress and Deformation Analysis of Gallery Structure in Hydraulic Engineered Cementitious Composite Foundation of Asphalt Core Rockfill Dam

[Objective] This study aims to address the cracking and leakage in the foundation galleries of core rockfill dams situated on deep overburden layers by proposing a novel HECC (Hydraulic Engineered Cementitious Composite) dam foundation gallery structure. The structure involves a plastic hinge section made of the HECC material at large stress positions to adapt to the gallery deformation. [Methods] First, three-dimensional finite element numerical simulation method was adopted to analyze the deformation properties of the gallery, reveal the cracking mechanism of the gallery, identify the prone-to-crack parts, and determine the position of the HECC material. Then, by comparing the stress distribution of the gallery before and after installing the HECC plastic hinge section, the anti-cracking effect of the composite gallery structure was verified. [Results] (1) Under hydrostatic loads and self-weight, the gallery exhibited complex flexural deformation. Overall, the maximum displacement occurred at the center of the riverbed, with deformation gradually decreasing towards the banks, showing distinct reverse bending zones at both ends. (2) For conventional concrete gallery, significant tensile stress zones were primarily located at the ends. Within 30 m of the right end and 35 m of the left end, the tensile stress exceeded the tensile strength of the concrete. This was particularly pronounced in the 10 m to 20 m range from each end, where high levels of tensile stress were observed at the gallery’s crown and sidewalls. (3) In the proposed foundation gallery structure, 20m-long HECC plastic hinge sections were installed at the ends on both the left and right banks. These HECC sections fully entered plastic state, with the maximum equivalent plastic strain remaining within the material’s allowable limits, ensuring that the HECC segments would not leak. (4) As the HECC sections underwent plastic deformation, they accommodated most of the deformation from the main gallery body. Through stress redistribution, the overall stress level in the conventional concrete portion of the gallery was significantly reduced. The area where tensile stress exceeded the design strength in the typical cross-sections of the high-stress zones at the ends was markedly decreased, with a maximum reduction of approximately 70%, thus significantly lowering the risk of cracking. [Conclusions] (1) The regions within 30m of the ends of the foundation gallery in asphalt core rockfill dam are areas of intense stress variation and are prone to cracking. (2) The introduction of HECC plastic hinge sections in these high-stress zones at both ends allows the HECC sections to enter a plastic state first. Through internal stress redistribution, the stress in the conventional gallery sections is substantially reduced. The areas where tensile stress exceeds the design strength in typical cross-sections, especially in the high-stress end zones, are significantly reduced, thereby reducing the risk of cracking. (3) The HECC plastic hinge sections leverages the material’s inherent strain-hardening, ultra-high toughness, crack dispersion, and self-healing properties. This not only ensures the sections themselves remain impermeable but also effectively reduces or prevents cracking and leakage issues in the concrete gallery.