核磁共振试验下水压变化对灰岩孔隙参数的影响OA

In order to understand the influence of reservoir water level fluctuations on the stability of dam foundation rock masses,the pore parameters of limestone taken from a high arch dam foundation in the Jinsha River under the condition of cyclic water pressure were studied by means of nuclear mag-netic resonance technology and water pressure control system.By analyzing the T2 spectra of the rock mass before and after the tests and combining with relevant formulas,the variation pattern of porosity,pore distribution and permeability of the initial saturated and dry specimens was investigated.The re-sults show that limestone has the highest content of micropores,and the content gradually decreases with increasing pore diameter,and the pore connectivity is good.After the water pressure test,the pore connectivity of the limestone is enhanced.The porosity of limestone decreases by 0.01%-0.08%,and the decrease in dry rock mass is greater when the initial state is the same.The magnitude of the initial porosity is directly proportional to the increase in the porosity of the movable fluid.There exists a threshold value for the initial porosity of limestone.In this experiment,this value is between 1.04%and 1.08%.If it is greater than this value,the porosity of the movable fluid increases;conversely,it decreases.The variation pattern of permeability is similar to that of porosity in movable fluids.Pore wa-ter pressure tends to cause the pores of the specimen to expand,while external water pressure causes the pores to contract.Both have a significant impact on the pores with diameters greater than and less than 0.1 μm,respectively.