Abstract: With the rapid development of water diversion projects, water conveyance tunnels often pass through adverse geological bodies of sandy cobble strata. The coupling of rainfall infiltration and tunnel excavation easily triggers water and sand inrush disasters, which seriously threatens engineering safety. Based on the geological conditions of water diversion tunnels in Luoyang area, a model test device for tunnel water and sand inrush with a multi-information monitoring system was independently developed. By simulating horseshoe-shaped tunnel excavation, two comparative working conditions (normal excavation and advanced reinforcement) were designed. Key parameters such as earth pressure, pore water pressure and displacement were monitored in real time. The characteristics of catastrophic evolution stages and the particle migration mechanism under seepage-stress coupling were systematically analyzed.The catastrophic evolution of water and sand inrush in tunnels in sandy cobble strata shows a five-stage characteristic:seepage → intensified seepage → particle loss → formation of piping channel → water and sand inrush failure.Particle migration undergoes the process of initial stability-initiation of fine particles - continuous migration- channel formation.Pore water pressure presents a phased variation of stable at early stage-sudden increase at middle stage-decrease at late stage. Surface settlement displays a three-stage pattern:rapid subsidence-slow subsidence-gentle stabilization.The coupling of rainfall and excavation forms a three-dimensional dynamic coupling mechanism of seepage-stress-particle migration,which is the core driving factor for disaster initiation.Advanced reinforcement is an effective measure to avoid surface collapse. The tests reveal the catastrophic evolution law and multi-field coupling mechanism of water and sand inrush in sandy cobble tunnels under the effect of rainfall infiltration,and identify the key catastrophic nodes and controlling factors.It provides a theoretical basis and technical support for the disaster-resistant design and construction risk prevention and control of tunnels in such special strata.