The Analysis Of Resistivity Sounding Used In Examination Of Effect Of Carst Grouting In Nanning-Guangzhou Railway

Karst in our country has a wide distribution, and its existence may adversely affect the construction of railway. In karstic areas of Nanning-Guangzhou railway, grouting was used to reinforce embankment. Resistivity sounding is a Geophysical exploration method which is based on the resistivity differences of under -ground mediums and gets resistivity vertical change by changing the electrode spacing. This method was used to detect the grouting quality.Based on test and resistivity sounding theory; it firstly discussed the test results in 3 diffierent Geological conditions which include caves covered by clays; Jointed rocks covered by clays and Pebbles; Jointed rocks covered by clays.Then it established models by the FEM tool ANSYS to make inversion of test data. Still it analysed the data changes before and after grouting, combined with geological and grouting conditions, then making evaluation of grouting quality which was tesed by resistivity sounding.In this paper, it focued on type of resistivity sounding curves, apparent resistivity changes before and after grouting, test results and influence scop of grouting by using test data and inversion results.Moreover, combined with analysis results and other test methods, it proposed the best detecting time after grouting to be 7～14 days.Meanwhile, evaluation standard of grouting quality which using resistivity sounding was estanded, when the changing rate of apparent resistivity before and after grouting is greater than 20%, the grouting effect grade is "significant"; when it is less than 10%,the grade is "less signifi-cant";when it is between 10% and 20%,the grade is "relatively significant"...