Stability Analysis Of Underground Openings Based On Load-unload Response Ratio(LURR)

In recent years, with the acceleration of infrastructure constructionof our country, especially the construction of subway and exploitation ofmines, many caverns are formed under the ground; There are manyfactors for the stability of underground caverns, most of which arenonlinear instability and may cause serious consequences once damaged;However, there are many limitations in actual operation in terms ofstability research of underground caverns. Load-unload response ratio is anew method of studying instability of nonlinear system. Currently, somescholars apply it in the earthquake prediction and stability analysis ofslopes. The paper is dedicated in applying this new method to theresearch of stability of underground caverns.(1) By taking load and stress as input parameters of load-unloadresponse ratio and taking displacement and strain as output response ofload-unload response ratio, the paper carries out analysis and research interms of mechanical property and strength characteristics of three types ofrocks, namely griotte, sandstone and serpentinite, under uniaxial andtriaxial loading and unloading. Research shows: when these three kindsof rocks reach their ultimate loads, or sharp increase of load-unloadresponse ratio occurs, or huge curve fluctuations of load-unload responseratio occurs, it indicates that load-unload response ratio has predictionfunction to the damage of rocks.(2) Combined with crustal stress data of copper mine in DongguaMountain and by taking advantage of FLAC3Dsimulation software oflarge numerical value, numerical simulation model is established andcalculated accordingly, with stress of the key point of cavern, maximumprimary stress, medium primary stress and minimum primary stress asinput parameter of load-unload response ratio and with strain,displacement and plastic zone as output response of load-unload responseratio; Research is carried out on the load-unload response ratio of singlecavern in the state of plane and three-dimensional and analysis isimplemented in terms of its stability. On the basis of that, the paper carries out preliminary discussion on the stability of underground caverncomplex.(3) By taking advantage of760plane tunnel and single pointdisplacement instrument of stope layout of copper mine in DongguaMountain, monitoring is carried out regarding internal displacement ofwall rock in caverns, long-term observation is needed for surfacedisplacement (that is vault subsidence) of caverns, and research is takenout on its displacement value and rate of change; Research shows that theinternal displacement of wall rock has the tendency of gradual increasewhile the value is small and the rate of exchange is almost identical. Thesurface displacement change of wall rock is relatively small. On the basisof that, the paper carries out analysis in terms of the stability of caverns.