Study on the coupled model of limestone soaking damage and pore water pressure in the Three Gorges Reservoir Area
[Objective]Since the start of water storage in 2003,the number of earthquakes in the Three Gorges Reservoir area has reached tens of thousands.Comparing the changes in seismic data before and after water storage,it can be seen that the soaking effect of reservoir water has significantly changed the mechanical properties of limestone in the seismic area of the reservoir.In or-der to study the influence of long-term reservoir water immersion on the mechanical properties of limestone in the reservoir area,[Methods]This article focuses on the water storage environment in the reservoir area and conducts experiments on the influence of different soaking times and pore water pressure on the triaxial compressive strength of limestone,as well as electron microscopy scanning analysis of the changes in limestone porosity under soaking.[Results]The experimental result showed that when differ-ent pore water pressures were considered in the immersion and triaxial tests,the triaxial compressive strength of limestone showed a strength enhancement phenomenon during short-term immersion,There are differences with some theories of water rock interac-tion.Based on these differences,this article analyzes the development law of limestone damage from the perspectives of macro-scopic mechanical properties and microstructure,and proposes a coupling model of limestone soak damage-pore water pressure coupling model.The critical value of pore pressure that causes dissolution pores to rupture under experimental conditions was estimated,and the pore pressure value was taken as 5.6 km underground based on static water pressure,which is in good agree-ment with the depth of the reservoir earthquake source in the Gaoqiao fault area of the Three Gorges Reservoir area.[Conclu-sion]The damage of limestone in the reservoir water earthquake area is not a single soaking damage,but a failure process that couples a series of complex phenomena such as porosity evolution,pore pressure change,and pore water morphology evolution.The research method in this article can provide certain theoretical reference value for the study of the mechanism of induced earth-quakes in hydraulic engineering.