Fang Y.,Wuhan University |
Huang Z.,Wuhan University |
Zhang X.,Wuhan University |
Yu Y.,Wuhan University |
And 3 more authors.
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2015
In order to study the mechanism of CO2 corrosion through condensed water in Longmen Grottoes, experimental location was set in Qianxi Temple where there existed serious disease of condensed water. The number of visitors, variations of carbon dioxide concentration, the forming rules of condensed water and variations of grotto's chemical composition were monitored in Qianxi Temple. Self-developed simulation equipment for CO2 corrosion was designed, and the macro solution rate was calculated. With the aid of scanning electron microscopy(SEM), carbonate's microscopic corrosion mechanism was studied. The results show that mass loss of carbonate rock grows exponentially, and limestone's solution rate is about 2 times of dolomite. When the temperature in cave is 25 ℃, humidity is 85% and CO2 concentration is 1×10-3, the condensate generation is up to 227.87 kg in Qianxi Temple every year. One hundred years later, the highest erosion depths might reach 4.35 cm. Then defection is mainly controlled by crystallinity and cleavage structure, because these differences limestone's solution rate is greater than that of the dolomite. What's more, pores between crystal become clear, and only crystal edges have obvious rounding and corrosion, which means solution effect occurs in surface. ©, 2015, Central South University of Technology. All right reserved.
Zhang A.,Hubei University |
Fang Y.,Hubei Engineering University |
Chen J.,Institute of Longmen Grottoes |
Fan Z.,Institute of Longmen Grottoes
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2014
In order to protect stone relics from the infraction of condensation water, it is necessary to study the mechanism of condensation water. Based on dissolution experimental methods, the dissolution of condensation water on carbonate rocks was stimulated with the self-made static and dynamic experimental system. Considering CO2 concentration, temperature and humidity, the effect of different factors on the dissolution process was analyzed and the mass loss, microstructure, water change, and etc. were tested during the experiment process. Finally, the process of dissolution was stimulated by the numerical software Phreeqc to verify the accuracy of simulation experiment. Static and dynamic simulation experiments show that condensation water dissolves carbonate rocks increasing with CO2 concentration and the dissolution of limestone is greater than dolomite. In the dynamic simulation experiment of vapor condensation, dolomite dissolution and rock porosity are significantly increased because the microscopic vapor is strong intrusive. Dissolution process and calculated dissolution depth are consistent with numerical simulation results. Dissolution curve shows quadratic indicating that preliminary dissolution is faster and post-dissolution is gentler. Calculated dissolution depth of limestone is 0.027 6 mm and the dissolution depth of dolomite is 0.0136 mm in a year. ©, 2014, Academia Sinica. All right reserved.
Ding W.,Luoyang Institute of Science and Technology |
Xu T.,China Construction Seventh Engineering Division Co. |
Wang H.,Luoyang Institute of Science and Technology |
Chen J.,Institute of Longmen Grottoes
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2015
Mechanical experiments of the limestone samples from Longmen grottoes under the action of coupled chemical solutions and freezing-thawing processes were carried out to investigate the infiltrated water erosion and freezing-thawing damage on the surrounding rocks in Longmen grottoes. The results of the experiments demonstrated that the mechanical damage of limestone was increased gradually as with increasing freezing- thawing cycles under the coupled chemical solution and freezing-thawing processes and the damage was greater than that under the erosion of chemical solutions only. For example, for the cases of the freezing-thawing cycles of 90 under the coupled chemical solution and freezing-thawing processes, the strengths of the specimens soaked in the distilled water, Longmen water and NaCl solution dropped 50.73%, 54.92% and 57.67% respectively compared with the specimen strength in the natural state. While under the erosion of chemical solutions without freezing-thawing, the strengths was dropped only 21.58%, 22.88% and 28.72% respectively. The freezing-thawing deterioration model of limestone under investigation was found to be all due to the particle loss model. The abundance of the condensation nuclei and the pH value of water solution were found to be the important factors affecting the degree of damage to the limestone under the coupled chemical solution and freezing-thawing processes. An equation describing the erosion damage to limestone under coupled action was established. ©, 2015, Academia Sinica. All right reserved.
Ding W.-X.,Luoyang Institute of Science and Technology |
Chen J.-P.,Institute of Longmen Grottoes |
Xu T.,China Construction Seventh Engineering Division Co. |
Chen H.-J.,Luoyang Institute of Science and Technology |
Wang H.-Y.,Luoyang Institute of Science and Technology
Yantu Lixue/Rock and Soil Mechanics | Year: 2015
To explore the chemical erosion phenomena, the chemical compositions of the spring water, seeping water and rainwater in Longmen Grottoes area are analyzed; and chemical solutions with different compositions are artificially made, which are in turn used to study the mechanical properties and the chemical solubility of Longmen Grottoes limestone under influences of different chemical solutions. The strength damage characteristics of the limestone are obtained based on the mechanical experiments with respect to different solutions and different erosion durations. A time-dependent corrosion equation of uniaxial compressive strength for limestone is developed under different chemical solutions. Based on the chemical kinetic tests on limestone under the effects of the different chemical solutions and for different erosion durations, the solubility of limestone eroded by different chemical solutions is addressed. The chemical dynamic erosion equations of limestone are developed. The analysis indicates that the strength of limestone decreases due to the dissolution of chemical solutions under chemical erosion. The salt effect and the common ion effect significantly influence the dissolution rate and strength of limestone. The salt effect can raise the dissolution rate, while the common ion effect can reduce the dissolution rate. When the composition and concentration of the solution are the same, the stronger the acidity, the larger the dissolution rate is. The dissolution rate of limestone increases with the increase of salt concentration when the composition and the pH value of the solution are the same. ©, 2015, Academia Sinica. All right reserved.