大雁塔盐害及劣化模拟试验研究

易溶盐富集是陕西西安大雁塔砖体表面风化、结构破坏、强度衰减的主要原因。为分析盐害对大雁塔砖体结构、强度的影响机理，采用以饱和硫酸钠溶液为介质，对大雁塔砖体进行易溶盐结晶循环模拟劣化试验。在Na₂SO₄反复结晶、溶解过程中，测定试样的质量、波速及单轴抗压强度等指标，分析其变化规律。结果表明，在盐害作用下，试验砖体表现出与塔体表面类似的风化破坏现象；Na₂SO₄晶体在试样孔隙内不断发育，晶体挤压效应导致孔隙率增大，内部结构破损；质量、波速、单轴抗压强度随循环的次数呈先增加后减小的变化规律。砖体对盐害耐受力约为砖体质量的0.5%。

Research on the salt disease and deterioration simulation of the Great Wild Goose Pagoda

Aggregation and crystallization of soluble salts is a critical contributor to the surface weathering,structural deconstruction and loss of strength of ancient bricks of the Great Wild Goose Pagoda in Xi’an,Shaanxi Province.In order to analyze the mechanism of the salt disease,we carried out a deterioration simulation where brick samples from the pagoda were soaked with a saturated solution of sodium sulfate.During the repeated cycles of crystallization-dissolution of thenardite(sodium sulfate),we determined the variation of mass,wave velocity,uniaxial compressive strength and other characteristics of the samples.The results show that 1)the weathering phenomena of the samples in the laboratory were similar to those of the natural bricks of the pagoda;2)the continuous crystallization force of thenardite increased the porosity and loosened the inner structure of the bricks;3)the variation patterns of mass,wave velocity and uniaxial compressive strength were similar—increasing at the beginning and then decreasing.The bearing capacity of a brick for soluble salts is 0.5%that of the mass percentage.