| With the continuous development of urbanization and industrialization in the loess area,the environmental pollution caused by a large amount of domestic sewage and industrial wastewater has become increasingly prominent,and the soil has been eroded,which has changed the physical state of the loess.The soil pollution and site stability are directly related to the safety and stability of buildings(structures)and natural slopes.This problem has become one of the environmental geotechnical issues that have received widespread attention.As a special soil,loess has typical special structure and engineering properties.At present,there are few studies on its tensile strength characteristics.Despite the small tensile strength of loess,the geological hazards caused by soil cracking,landslides and debris flows cannot be ignored.The pollution of the environment to the soil affects the evolution of the tensile strength of loess and the stability of the project.Therefore,the research on the tensile strength of contaminated soil is of great significance in the practical application of environmental engineering.Based on this,research work on the tensile strength characteristics of acid-contaminated undisturbed loess was carried.The tensile strength of the undisturbed loess contaminated by different concentrations of hydrochloric acid,nitric acid and sulfuric acid was studied by uniaxial stretching.The damage mechanism of the undisturbed loess contaminated by acid was analyzed from the changes in the internal structure of the soil and the corrosion evolution of chemical substances.The following research results were summarized:(1)At present,the testing instrument for the tensile strength of loess is still in the process of discussion and standardization.It is not perfect and has not formed a unified standard.In order to simulate the undisturbed loess tensile cracking failure to the greatest extent,it has been assembled by itself after many debugging and tests.A set of horizontal uniaxial tension device for testing the tensile strength provides a relatively reliable testing method for the study of the tensile strength of loess.The results are compared through the axial fracturing test,and the difference between the two test results is small,that is,the horizontal uniaxial tensile tester can be used for experimental research.(2)The tensile strength of acid-contaminated undisturbed loess was studied.Four concentrations of acid solutions were configured to measure the tensile strength of the contaminated undisturbed loess.The research results show that the tensile strength is between 6.47 k Pa and 11.82 k Pa,which is relatively high.The tensile strength of uncontaminated soil has decreased,and the tensile strength damage range is between 10.32%and 45.26%.The type of acid solution is different,and its tensile strength is as follows:hydrochloric acid <nitric acid <sulfuric acid <distilled water.With the increase of acid solution concentration,the tensile strength of soil contaminated by hydrochloric acid and nitric acid decreased,and the tensile strength of soil contaminated by sulfuric acid increased and the increase gradually decreased.(3)The tensile strength of the acid-contaminated undisturbed loess under different freeze-thaw cycles was studied.The test results showed that with the increase of the number of freeze-thaw cycles,the tensile strength of the acid-contaminated undisturbed loess decreased,3 to 5 times.After the freeze-thaw cycle,the tensile strength of loess tends to be basically stable.Based on the analysis of test data,a model for the deterioration of the tensile strength of loess under acid erosion and freeze-thaw cycles was established.(4)Through the numerical simulation analysis of acid-contaminated slope stability,the safety factor of slope stability is 2.43.With the increase of acid solution concentration,the slope stability shows a decreasing trend,which has a significant impact on the shallow stability of the slope.And most of the sliding surface of the slope is flat failure. |
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