Study On Grouting Detection Method And Assessment Indicators Of Karst Roadbed Grouting Effect In Nanning-Guangzhou Railway

Abstract:The problem of covered karst is becoming potential hazards of new Nanguang railway’s roadbed stability owing to the strong development of karst and clear features of its surface subsidence. This thesis is based on Nanguang railway construction project, combined with large-scale indoor and outdoor experiments and theoretical analyses. An in-depth and systematic analysis of testing standards and methods for railway karst roadbed grouting effect is carried out. The course of this study applies data analyses, laboratory experiments, numerical analyses, site monitoring and other methods. And the findings of the study are as follows:1. An in-depth investigation and analysis of engineering geologic background Nanguang railway’s karst roadbed defines the types of on-site testing areas. And three typically geological models are formed, the fractured limestone model with clay overburden, the fractured limestone model with sand and gravel overburden, the karst cave limestone model with clay overburden respectively. A study of the purpose of karst roadbed grouting reinforcement, as well as a research of the testing depth determines the testing methods for the resistivity method, transient surface wave law, electromagnetic wave CT and pressurized water testing method.2. Indoor model tests are employed to investigate the resistivity method grouting effect, and the influence of generalized model’s resistivity testing effect with different karst roadbeds before, after grouting and groundwater level changes on it. Another study is carried out, focusing on the relationship between device parameters and testing depth, cover layer’s impact, underground water levels’impact and different karst roadbed geological generalized model resistivity testing effect and standards.3. An in-depth analysis of the electrical sounding curve before and after grouting, the apparent resistivity contour before and after grouting, different time detection results after grouting, and the resistivity-method testing standards after grouting in the typical geological cross-section of the different pilot areas is presented via the grouting effect testing of Nanguang railway.4. Laboratory experiments are to test the conventional wave velocity characteristics of the scene typical geological media objects. And a detailed analysis of grouting effect testing standards with varying geological generalized models is presented based on the test results, combined with the finite element numerical simulation.5. An overall analysis of grouting effect testing standards with instantaneous surface wave method is employed, based on the field trials of the Rayleigh wave propagation characteristics of typically geological cross-section in different pilot areas before and after grouting, surface particle vibration characteristics and the variation of dispersion curves, united by site validation for grouting effect.6. A systematic analysis of the influence of fracture distribution and combination characteristics, fracture length and roughness, fissure opening degree on the rock permeability rate in water pressure testing is adopted, based on the pipe model test with different roughness, horizontal-lined single fractured deal model test, horizontal-surfaced single fractured deal model test,and three sets of orthogonal fissures ideal model test.7. An in-depth study of the relationship of various detection methods, integrated ways and full testing standards is accomplished through the comprehensive comparison of various detection methods and testing standards.