Damage Experiment Study And Mechanism Analysis For The Limestone Under Mechanical-hydrological-chemical Coupling

In recent years, rock mass of Longmen Grottoes by the chemical corrosion effect of the seepage flow, subsequent humus, acid rain and acid fog is relatively serious. The effect of Mechanical(M)-Hydrological(H)-Chemical(C) coupling accelerates the chemical corrosion of rock mass, which weakens the physical and mechanical properties of the rock mass, which is a threat to the long-term stability of the rock mass of Longmen Grottoes. According to the M, H, C factors of Longmen Grottoes area, carries out the physical and mechanical experiments of Longmen Grottoes fresh limestone under the corrosion effect of MHC coupling, analyzes the damage time-dependent characteristics and corrosion damage mechanism of the physical and mechanical parameters. The results will provide certain theoretical basis for the protection of Longmen Grottoes, which has important practical values for projects. The main research work and results are as follows:1. The physical and mechanical time-dependent characteristics of Longmen Grottoes fresh limestone under MC coupling are researched. The mass, the elastic wave velocity, uniaxial compression strength of the specimens and the pH values of water solutions under MC coupling with different soaking time are measured, and the experimental results of fresh limestone and weathering limestone are Compared. The results show that: The increase of quality is mainly due to the absorption of moisture, which is hardly influenced by chemical properties of water solutions, which can achieve stability in 30 days. The time that the elastic wave velocity comes to the highs and lows for weathering limestone is earlier than fresh limestone, the elastic wave velocity changes frequently, the variation of elastic wave velocity before and after corrosion is larger. Regardless of the weathering or fresh specimen, the stable time of pH value for Longmen water is the shortest, which is 2 hours and 10 hours, and Na2SO4 solution is the longest, its stable time is 20 days and 35 days. The variation of the strength for weathering limestone is larger than fresh limestone in the same water solution, the longer, the more obvious.2. The physical and mechanical time-dependent characteristics of Longmen Grottoes fresh limestone under MHC coupling are researched. The mass, the elasticwave velocity, uniaxial compression strength of the specimens and the pH values of water solutions under MHC coupling with different soaking time are measured, and the experimental results of fresh limestone under the effect of MC and MHC coupling are Compared. The results show that: The interval of reaching stable for quality under MHC coupling is longer than MC coupling, the declining amplitude of quality under MHC coupling is larger than MC coupling, the fluctuation period the elastic wave velocity gets shorter with time for MHC coupling. The final stable pH value gets larger and the stable time gets shorter. The declining amplitude of strength under the effect of NaCl solution is larger in the same ionic concentration and pH value. In the same ionic concentration and chemical composition, the pH is smaller, the reducing of the strength is greater. In the same chemical composition and pH value, the ionic concentration is bigger, the reducing of the strength is greater. The shorten strength of limestone under MHC coupling is greater than MC coupling. With the increase of corrosion time, the declining amplitude of strength gets grow.3. Establishes the corrosion damage model of Longmen Grottoes limestone under the actions of MHC coupling, and compares with the test results. The results show that: the model is better in accordance with the experimental data.